diff options
Diffstat (limited to 'Documentation')
41 files changed, 2968 insertions, 282 deletions
diff --git a/Documentation/DMA-API.txt b/Documentation/DMA-API.txt index 1af0f2d50220..2ffb0d62f0fe 100644 --- a/Documentation/DMA-API.txt +++ b/Documentation/DMA-API.txt | |||
@@ -33,7 +33,9 @@ pci_alloc_consistent(struct pci_dev *dev, size_t size, | |||
33 | 33 | ||
34 | Consistent memory is memory for which a write by either the device or | 34 | Consistent memory is memory for which a write by either the device or |
35 | the processor can immediately be read by the processor or device | 35 | the processor can immediately be read by the processor or device |
36 | without having to worry about caching effects. | 36 | without having to worry about caching effects. (You may however need |
37 | to make sure to flush the processor's write buffers before telling | ||
38 | devices to read that memory.) | ||
37 | 39 | ||
38 | This routine allocates a region of <size> bytes of consistent memory. | 40 | This routine allocates a region of <size> bytes of consistent memory. |
39 | it also returns a <dma_handle> which may be cast to an unsigned | 41 | it also returns a <dma_handle> which may be cast to an unsigned |
@@ -304,12 +306,12 @@ dma address with dma_mapping_error(). A non zero return value means the mapping | |||
304 | could not be created and the driver should take appropriate action (eg | 306 | could not be created and the driver should take appropriate action (eg |
305 | reduce current DMA mapping usage or delay and try again later). | 307 | reduce current DMA mapping usage or delay and try again later). |
306 | 308 | ||
307 | int | 309 | int |
308 | dma_map_sg(struct device *dev, struct scatterlist *sg, int nents, | 310 | dma_map_sg(struct device *dev, struct scatterlist *sg, |
309 | enum dma_data_direction direction) | 311 | int nents, enum dma_data_direction direction) |
310 | int | 312 | int |
311 | pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg, | 313 | pci_map_sg(struct pci_dev *hwdev, struct scatterlist *sg, |
312 | int nents, int direction) | 314 | int nents, int direction) |
313 | 315 | ||
314 | Maps a scatter gather list from the block layer. | 316 | Maps a scatter gather list from the block layer. |
315 | 317 | ||
@@ -327,12 +329,33 @@ critical that the driver do something, in the case of a block driver | |||
327 | aborting the request or even oopsing is better than doing nothing and | 329 | aborting the request or even oopsing is better than doing nothing and |
328 | corrupting the filesystem. | 330 | corrupting the filesystem. |
329 | 331 | ||
330 | void | 332 | With scatterlists, you use the resulting mapping like this: |
331 | dma_unmap_sg(struct device *dev, struct scatterlist *sg, int nhwentries, | 333 | |
332 | enum dma_data_direction direction) | 334 | int i, count = dma_map_sg(dev, sglist, nents, direction); |
333 | void | 335 | struct scatterlist *sg; |
334 | pci_unmap_sg(struct pci_dev *hwdev, struct scatterlist *sg, | 336 | |
335 | int nents, int direction) | 337 | for (i = 0, sg = sglist; i < count; i++, sg++) { |
338 | hw_address[i] = sg_dma_address(sg); | ||
339 | hw_len[i] = sg_dma_len(sg); | ||
340 | } | ||
341 | |||
342 | where nents is the number of entries in the sglist. | ||
343 | |||
344 | The implementation is free to merge several consecutive sglist entries | ||
345 | into one (e.g. with an IOMMU, or if several pages just happen to be | ||
346 | physically contiguous) and returns the actual number of sg entries it | ||
347 | mapped them to. On failure 0, is returned. | ||
348 | |||
349 | Then you should loop count times (note: this can be less than nents times) | ||
350 | and use sg_dma_address() and sg_dma_len() macros where you previously | ||
351 | accessed sg->address and sg->length as shown above. | ||
352 | |||
353 | void | ||
354 | dma_unmap_sg(struct device *dev, struct scatterlist *sg, | ||
355 | int nhwentries, enum dma_data_direction direction) | ||
356 | void | ||
357 | pci_unmap_sg(struct pci_dev *hwdev, struct scatterlist *sg, | ||
358 | int nents, int direction) | ||
336 | 359 | ||
337 | unmap the previously mapped scatter/gather list. All the parameters | 360 | unmap the previously mapped scatter/gather list. All the parameters |
338 | must be the same as those and passed in to the scatter/gather mapping | 361 | must be the same as those and passed in to the scatter/gather mapping |
diff --git a/Documentation/DMA-mapping.txt b/Documentation/DMA-mapping.txt index ee4bb73683cd..7c717699032c 100644 --- a/Documentation/DMA-mapping.txt +++ b/Documentation/DMA-mapping.txt | |||
@@ -58,11 +58,15 @@ translating each of those pages back to a kernel address using | |||
58 | something like __va(). [ EDIT: Update this when we integrate | 58 | something like __va(). [ EDIT: Update this when we integrate |
59 | Gerd Knorr's generic code which does this. ] | 59 | Gerd Knorr's generic code which does this. ] |
60 | 60 | ||
61 | This rule also means that you may not use kernel image addresses | 61 | This rule also means that you may use neither kernel image addresses |
62 | (ie. items in the kernel's data/text/bss segment, or your driver's) | 62 | (items in data/text/bss segments), nor module image addresses, nor |
63 | nor may you use kernel stack addresses for DMA. Both of these items | 63 | stack addresses for DMA. These could all be mapped somewhere entirely |
64 | might be mapped somewhere entirely different than the rest of physical | 64 | different than the rest of physical memory. Even if those classes of |
65 | memory. | 65 | memory could physically work with DMA, you'd need to ensure the I/O |
66 | buffers were cacheline-aligned. Without that, you'd see cacheline | ||
67 | sharing problems (data corruption) on CPUs with DMA-incoherent caches. | ||
68 | (The CPU could write to one word, DMA would write to a different one | ||
69 | in the same cache line, and one of them could be overwritten.) | ||
66 | 70 | ||
67 | Also, this means that you cannot take the return of a kmap() | 71 | Also, this means that you cannot take the return of a kmap() |
68 | call and DMA to/from that. This is similar to vmalloc(). | 72 | call and DMA to/from that. This is similar to vmalloc(). |
@@ -194,7 +198,7 @@ document for how to handle this case. | |||
194 | Finally, if your device can only drive the low 24-bits of | 198 | Finally, if your device can only drive the low 24-bits of |
195 | address during PCI bus mastering you might do something like: | 199 | address during PCI bus mastering you might do something like: |
196 | 200 | ||
197 | if (pci_set_dma_mask(pdev, 0x00ffffff)) { | 201 | if (pci_set_dma_mask(pdev, DMA_24BIT_MASK)) { |
198 | printk(KERN_WARNING | 202 | printk(KERN_WARNING |
199 | "mydev: 24-bit DMA addressing not available.\n"); | 203 | "mydev: 24-bit DMA addressing not available.\n"); |
200 | goto ignore_this_device; | 204 | goto ignore_this_device; |
@@ -212,7 +216,7 @@ functions (for example a sound card provides playback and record | |||
212 | functions) and the various different functions have _different_ | 216 | functions) and the various different functions have _different_ |
213 | DMA addressing limitations, you may wish to probe each mask and | 217 | DMA addressing limitations, you may wish to probe each mask and |
214 | only provide the functionality which the machine can handle. It | 218 | only provide the functionality which the machine can handle. It |
215 | is important that the last call to pci_set_dma_mask() be for the | 219 | is important that the last call to pci_set_dma_mask() be for the |
216 | most specific mask. | 220 | most specific mask. |
217 | 221 | ||
218 | Here is pseudo-code showing how this might be done: | 222 | Here is pseudo-code showing how this might be done: |
@@ -284,6 +288,11 @@ There are two types of DMA mappings: | |||
284 | 288 | ||
285 | in order to get correct behavior on all platforms. | 289 | in order to get correct behavior on all platforms. |
286 | 290 | ||
291 | Also, on some platforms your driver may need to flush CPU write | ||
292 | buffers in much the same way as it needs to flush write buffers | ||
293 | found in PCI bridges (such as by reading a register's value | ||
294 | after writing it). | ||
295 | |||
287 | - Streaming DMA mappings which are usually mapped for one DMA transfer, | 296 | - Streaming DMA mappings which are usually mapped for one DMA transfer, |
288 | unmapped right after it (unless you use pci_dma_sync_* below) and for which | 297 | unmapped right after it (unless you use pci_dma_sync_* below) and for which |
289 | hardware can optimize for sequential accesses. | 298 | hardware can optimize for sequential accesses. |
@@ -303,6 +312,9 @@ There are two types of DMA mappings: | |||
303 | 312 | ||
304 | Neither type of DMA mapping has alignment restrictions that come | 313 | Neither type of DMA mapping has alignment restrictions that come |
305 | from PCI, although some devices may have such restrictions. | 314 | from PCI, although some devices may have such restrictions. |
315 | Also, systems with caches that aren't DMA-coherent will work better | ||
316 | when the underlying buffers don't share cache lines with other data. | ||
317 | |||
306 | 318 | ||
307 | Using Consistent DMA mappings. | 319 | Using Consistent DMA mappings. |
308 | 320 | ||
diff --git a/Documentation/DocBook/Makefile b/Documentation/DocBook/Makefile index 7d87dd73cbe4..5a2882d275ba 100644 --- a/Documentation/DocBook/Makefile +++ b/Documentation/DocBook/Makefile | |||
@@ -2,7 +2,7 @@ | |||
2 | # This makefile is used to generate the kernel documentation, | 2 | # This makefile is used to generate the kernel documentation, |
3 | # primarily based on in-line comments in various source files. | 3 | # primarily based on in-line comments in various source files. |
4 | # See Documentation/kernel-doc-nano-HOWTO.txt for instruction in how | 4 | # See Documentation/kernel-doc-nano-HOWTO.txt for instruction in how |
5 | # to ducument the SRC - and how to read it. | 5 | # to document the SRC - and how to read it. |
6 | # To add a new book the only step required is to add the book to the | 6 | # To add a new book the only step required is to add the book to the |
7 | # list of DOCBOOKS. | 7 | # list of DOCBOOKS. |
8 | 8 | ||
diff --git a/Documentation/DocBook/kernel-api.tmpl b/Documentation/DocBook/kernel-api.tmpl index 8c9c6704e85b..ca02e04a906c 100644 --- a/Documentation/DocBook/kernel-api.tmpl +++ b/Documentation/DocBook/kernel-api.tmpl | |||
@@ -322,7 +322,6 @@ X!Earch/i386/kernel/mca.c | |||
322 | <chapter id="sysfs"> | 322 | <chapter id="sysfs"> |
323 | <title>The Filesystem for Exporting Kernel Objects</title> | 323 | <title>The Filesystem for Exporting Kernel Objects</title> |
324 | !Efs/sysfs/file.c | 324 | !Efs/sysfs/file.c |
325 | !Efs/sysfs/dir.c | ||
326 | !Efs/sysfs/symlink.c | 325 | !Efs/sysfs/symlink.c |
327 | !Efs/sysfs/bin.c | 326 | !Efs/sysfs/bin.c |
328 | </chapter> | 327 | </chapter> |
diff --git a/Documentation/DocBook/libata.tmpl b/Documentation/DocBook/libata.tmpl index d260d92089ad..f869b03929db 100644 --- a/Documentation/DocBook/libata.tmpl +++ b/Documentation/DocBook/libata.tmpl | |||
@@ -120,14 +120,27 @@ void (*dev_config) (struct ata_port *, struct ata_device *); | |||
120 | <programlisting> | 120 | <programlisting> |
121 | void (*set_piomode) (struct ata_port *, struct ata_device *); | 121 | void (*set_piomode) (struct ata_port *, struct ata_device *); |
122 | void (*set_dmamode) (struct ata_port *, struct ata_device *); | 122 | void (*set_dmamode) (struct ata_port *, struct ata_device *); |
123 | void (*post_set_mode) (struct ata_port *ap); | 123 | void (*post_set_mode) (struct ata_port *); |
124 | unsigned int (*mode_filter) (struct ata_port *, struct ata_device *, unsigned int); | ||
124 | </programlisting> | 125 | </programlisting> |
125 | 126 | ||
126 | <para> | 127 | <para> |
127 | Hooks called prior to the issue of SET FEATURES - XFER MODE | 128 | Hooks called prior to the issue of SET FEATURES - XFER MODE |
128 | command. dev->pio_mode is guaranteed to be valid when | 129 | command. The optional ->mode_filter() hook is called when libata |
129 | ->set_piomode() is called, and dev->dma_mode is guaranteed to be | 130 | has built a mask of the possible modes. This is passed to the |
130 | valid when ->set_dmamode() is called. ->post_set_mode() is | 131 | ->mode_filter() function which should return a mask of valid modes |
132 | after filtering those unsuitable due to hardware limits. It is not | ||
133 | valid to use this interface to add modes. | ||
134 | </para> | ||
135 | <para> | ||
136 | dev->pio_mode and dev->dma_mode are guaranteed to be valid when | ||
137 | ->set_piomode() and when ->set_dmamode() is called. The timings for | ||
138 | any other drive sharing the cable will also be valid at this point. | ||
139 | That is the library records the decisions for the modes of each | ||
140 | drive on a channel before it attempts to set any of them. | ||
141 | </para> | ||
142 | <para> | ||
143 | ->post_set_mode() is | ||
131 | called unconditionally, after the SET FEATURES - XFER MODE | 144 | called unconditionally, after the SET FEATURES - XFER MODE |
132 | command completes successfully. | 145 | command completes successfully. |
133 | </para> | 146 | </para> |
@@ -230,6 +243,32 @@ void (*dev_select)(struct ata_port *ap, unsigned int device); | |||
230 | 243 | ||
231 | </sect2> | 244 | </sect2> |
232 | 245 | ||
246 | <sect2><title>Private tuning method</title> | ||
247 | <programlisting> | ||
248 | void (*set_mode) (struct ata_port *ap); | ||
249 | </programlisting> | ||
250 | |||
251 | <para> | ||
252 | By default libata performs drive and controller tuning in | ||
253 | accordance with the ATA timing rules and also applies blacklists | ||
254 | and cable limits. Some controllers need special handling and have | ||
255 | custom tuning rules, typically raid controllers that use ATA | ||
256 | commands but do not actually do drive timing. | ||
257 | </para> | ||
258 | |||
259 | <warning> | ||
260 | <para> | ||
261 | This hook should not be used to replace the standard controller | ||
262 | tuning logic when a controller has quirks. Replacing the default | ||
263 | tuning logic in that case would bypass handling for drive and | ||
264 | bridge quirks that may be important to data reliability. If a | ||
265 | controller needs to filter the mode selection it should use the | ||
266 | mode_filter hook instead. | ||
267 | </para> | ||
268 | </warning> | ||
269 | |||
270 | </sect2> | ||
271 | |||
233 | <sect2><title>Reset ATA bus</title> | 272 | <sect2><title>Reset ATA bus</title> |
234 | <programlisting> | 273 | <programlisting> |
235 | void (*phy_reset) (struct ata_port *ap); | 274 | void (*phy_reset) (struct ata_port *ap); |
@@ -666,7 +705,7 @@ and other resources, etc. | |||
666 | 705 | ||
667 | <sect1><title>ata_scsi_error()</title> | 706 | <sect1><title>ata_scsi_error()</title> |
668 | <para> | 707 | <para> |
669 | ata_scsi_error() is the current hostt->eh_strategy_handler() | 708 | ata_scsi_error() is the current transportt->eh_strategy_handler() |
670 | for libata. As discussed above, this will be entered in two | 709 | for libata. As discussed above, this will be entered in two |
671 | cases - timeout and ATAPI error completion. This function | 710 | cases - timeout and ATAPI error completion. This function |
672 | calls low level libata driver's eng_timeout() callback, the | 711 | calls low level libata driver's eng_timeout() callback, the |
diff --git a/Documentation/acpi-hotkey.txt b/Documentation/acpi-hotkey.txt index 744f1aec6553..38040fa37649 100644 --- a/Documentation/acpi-hotkey.txt +++ b/Documentation/acpi-hotkey.txt | |||
@@ -30,7 +30,7 @@ specific hotkey(event)) | |||
30 | echo "event_num:event_type:event_argument" > | 30 | echo "event_num:event_type:event_argument" > |
31 | /proc/acpi/hotkey/action. | 31 | /proc/acpi/hotkey/action. |
32 | The result of the execution of this aml method is | 32 | The result of the execution of this aml method is |
33 | attached to /proc/acpi/hotkey/poll_method, which is dnyamically | 33 | attached to /proc/acpi/hotkey/poll_method, which is dynamically |
34 | created. Please use command "cat /proc/acpi/hotkey/polling_method" | 34 | created. Please use command "cat /proc/acpi/hotkey/polling_method" |
35 | to retrieve it. | 35 | to retrieve it. |
36 | 36 | ||
diff --git a/Documentation/feature-removal-schedule.txt b/Documentation/feature-removal-schedule.txt index 495858b236b6..293fed113dff 100644 --- a/Documentation/feature-removal-schedule.txt +++ b/Documentation/feature-removal-schedule.txt | |||
@@ -71,14 +71,6 @@ Who: Mauro Carvalho Chehab <mchehab@brturbo.com.br> | |||
71 | 71 | ||
72 | --------------------------- | 72 | --------------------------- |
73 | 73 | ||
74 | What: remove EXPORT_SYMBOL(panic_timeout) | ||
75 | When: April 2006 | ||
76 | Files: kernel/panic.c | ||
77 | Why: No modular usage in the kernel. | ||
78 | Who: Adrian Bunk <bunk@stusta.de> | ||
79 | |||
80 | --------------------------- | ||
81 | |||
82 | What: remove EXPORT_SYMBOL(insert_resource) | 74 | What: remove EXPORT_SYMBOL(insert_resource) |
83 | When: April 2006 | 75 | When: April 2006 |
84 | Files: kernel/resource.c | 76 | Files: kernel/resource.c |
@@ -127,13 +119,6 @@ Who: Christoph Hellwig <hch@lst.de> | |||
127 | 119 | ||
128 | --------------------------- | 120 | --------------------------- |
129 | 121 | ||
130 | What: EXPORT_SYMBOL(lookup_hash) | ||
131 | When: January 2006 | ||
132 | Why: Too low-level interface. Use lookup_one_len or lookup_create instead. | ||
133 | Who: Christoph Hellwig <hch@lst.de> | ||
134 | |||
135 | --------------------------- | ||
136 | |||
137 | What: CONFIG_FORCED_INLINING | 122 | What: CONFIG_FORCED_INLINING |
138 | When: June 2006 | 123 | When: June 2006 |
139 | Why: Config option is there to see if gcc is good enough. (in january | 124 | Why: Config option is there to see if gcc is good enough. (in january |
@@ -241,3 +226,15 @@ Why: The USB subsystem has changed a lot over time, and it has been | |||
241 | Who: Greg Kroah-Hartman <gregkh@suse.de> | 226 | Who: Greg Kroah-Hartman <gregkh@suse.de> |
242 | 227 | ||
243 | --------------------------- | 228 | --------------------------- |
229 | |||
230 | What: find_trylock_page | ||
231 | When: January 2007 | ||
232 | Why: The interface no longer has any callers left in the kernel. It | ||
233 | is an odd interface (compared with other find_*_page functions), in | ||
234 | that it does not take a refcount to the page, only the page lock. | ||
235 | It should be replaced with find_get_page or find_lock_page if possible. | ||
236 | This feature removal can be reevaluated if users of the interface | ||
237 | cannot cleanly use something else. | ||
238 | Who: Nick Piggin <npiggin@suse.de> | ||
239 | |||
240 | --------------------------- | ||
diff --git a/Documentation/filesystems/vfs.txt b/Documentation/filesystems/vfs.txt index adaa899e5c90..3a2e5520c1e3 100644 --- a/Documentation/filesystems/vfs.txt +++ b/Documentation/filesystems/vfs.txt | |||
@@ -694,7 +694,7 @@ struct file_operations | |||
694 | ---------------------- | 694 | ---------------------- |
695 | 695 | ||
696 | This describes how the VFS can manipulate an open file. As of kernel | 696 | This describes how the VFS can manipulate an open file. As of kernel |
697 | 2.6.13, the following members are defined: | 697 | 2.6.17, the following members are defined: |
698 | 698 | ||
699 | struct file_operations { | 699 | struct file_operations { |
700 | loff_t (*llseek) (struct file *, loff_t, int); | 700 | loff_t (*llseek) (struct file *, loff_t, int); |
@@ -723,6 +723,10 @@ struct file_operations { | |||
723 | int (*check_flags)(int); | 723 | int (*check_flags)(int); |
724 | int (*dir_notify)(struct file *filp, unsigned long arg); | 724 | int (*dir_notify)(struct file *filp, unsigned long arg); |
725 | int (*flock) (struct file *, int, struct file_lock *); | 725 | int (*flock) (struct file *, int, struct file_lock *); |
726 | ssize_t (*splice_write)(struct pipe_inode_info *, struct file *, size_t, unsigned | ||
727 | int); | ||
728 | ssize_t (*splice_read)(struct file *, struct pipe_inode_info *, size_t, unsigned | ||
729 | int); | ||
726 | }; | 730 | }; |
727 | 731 | ||
728 | Again, all methods are called without any locks being held, unless | 732 | Again, all methods are called without any locks being held, unless |
@@ -790,6 +794,12 @@ otherwise noted. | |||
790 | 794 | ||
791 | flock: called by the flock(2) system call | 795 | flock: called by the flock(2) system call |
792 | 796 | ||
797 | splice_write: called by the VFS to splice data from a pipe to a file. This | ||
798 | method is used by the splice(2) system call | ||
799 | |||
800 | splice_read: called by the VFS to splice data from file to a pipe. This | ||
801 | method is used by the splice(2) system call | ||
802 | |||
793 | Note that the file operations are implemented by the specific | 803 | Note that the file operations are implemented by the specific |
794 | filesystem in which the inode resides. When opening a device node | 804 | filesystem in which the inode resides. When opening a device node |
795 | (character or block special) most filesystems will call special | 805 | (character or block special) most filesystems will call special |
diff --git a/Documentation/fujitsu/frv/kernel-ABI.txt b/Documentation/fujitsu/frv/kernel-ABI.txt index 0ed9b0a779bc..8b0a5fc8bfd9 100644 --- a/Documentation/fujitsu/frv/kernel-ABI.txt +++ b/Documentation/fujitsu/frv/kernel-ABI.txt | |||
@@ -1,17 +1,19 @@ | |||
1 | ================================= | 1 | ================================= |
2 | INTERNAL KERNEL ABI FOR FR-V ARCH | 2 | INTERNAL KERNEL ABI FOR FR-V ARCH |
3 | ================================= | 3 | ================================= |
4 | 4 | ||
5 | The internal FRV kernel ABI is not quite the same as the userspace ABI. A number of the registers | 5 | The internal FRV kernel ABI is not quite the same as the userspace ABI. A |
6 | are used for special purposed, and the ABI is not consistent between modules vs core, and MMU vs | 6 | number of the registers are used for special purposed, and the ABI is not |
7 | no-MMU. | 7 | consistent between modules vs core, and MMU vs no-MMU. |
8 | 8 | ||
9 | This partly stems from the fact that FRV CPUs do not have a separate supervisor stack pointer, and | 9 | This partly stems from the fact that FRV CPUs do not have a separate |
10 | most of them do not have any scratch registers, thus requiring at least one general purpose | 10 | supervisor stack pointer, and most of them do not have any scratch |
11 | register to be clobbered in such an event. Also, within the kernel core, it is possible to simply | 11 | registers, thus requiring at least one general purpose register to be |
12 | jump or call directly between functions using a relative offset. This cannot be extended to modules | 12 | clobbered in such an event. Also, within the kernel core, it is possible to |
13 | for the displacement is likely to be too far. Thus in modules the address of a function to call | 13 | simply jump or call directly between functions using a relative offset. |
14 | must be calculated in a register and then used, requiring two extra instructions. | 14 | This cannot be extended to modules for the displacement is likely to be too |
15 | far. Thus in modules the address of a function to call must be calculated | ||
16 | in a register and then used, requiring two extra instructions. | ||
15 | 17 | ||
16 | This document has the following sections: | 18 | This document has the following sections: |
17 | 19 | ||
@@ -39,7 +41,8 @@ When a system call is made, the following registers are effective: | |||
39 | CPU OPERATING MODES | 41 | CPU OPERATING MODES |
40 | =================== | 42 | =================== |
41 | 43 | ||
42 | The FR-V CPU has three basic operating modes. In order of increasing capability: | 44 | The FR-V CPU has three basic operating modes. In order of increasing |
45 | capability: | ||
43 | 46 | ||
44 | (1) User mode. | 47 | (1) User mode. |
45 | 48 | ||
@@ -47,42 +50,46 @@ The FR-V CPU has three basic operating modes. In order of increasing capability: | |||
47 | 50 | ||
48 | (2) Kernel mode. | 51 | (2) Kernel mode. |
49 | 52 | ||
50 | Normal kernel mode. There are many additional control registers available that may be | 53 | Normal kernel mode. There are many additional control registers |
51 | accessed in this mode, in addition to all the stuff available to user mode. This has two | 54 | available that may be accessed in this mode, in addition to all the |
52 | submodes: | 55 | stuff available to user mode. This has two submodes: |
53 | 56 | ||
54 | (a) Exceptions enabled (PSR.T == 1). | 57 | (a) Exceptions enabled (PSR.T == 1). |
55 | 58 | ||
56 | Exceptions will invoke the appropriate normal kernel mode handler. On entry to the | 59 | Exceptions will invoke the appropriate normal kernel mode |
57 | handler, the PSR.T bit will be cleared. | 60 | handler. On entry to the handler, the PSR.T bit will be cleared. |
58 | 61 | ||
59 | (b) Exceptions disabled (PSR.T == 0). | 62 | (b) Exceptions disabled (PSR.T == 0). |
60 | 63 | ||
61 | No exceptions or interrupts may happen. Any mandatory exceptions will cause the CPU to | 64 | No exceptions or interrupts may happen. Any mandatory exceptions |
62 | halt unless the CPU is told to jump into debug mode instead. | 65 | will cause the CPU to halt unless the CPU is told to jump into |
66 | debug mode instead. | ||
63 | 67 | ||
64 | (3) Debug mode. | 68 | (3) Debug mode. |
65 | 69 | ||
66 | No exceptions may happen in this mode. Memory protection and management exceptions will be | 70 | No exceptions may happen in this mode. Memory protection and |
67 | flagged for later consideration, but the exception handler won't be invoked. Debugging traps | 71 | management exceptions will be flagged for later consideration, but |
68 | such as hardware breakpoints and watchpoints will be ignored. This mode is entered only by | 72 | the exception handler won't be invoked. Debugging traps such as |
69 | debugging events obtained from the other two modes. | 73 | hardware breakpoints and watchpoints will be ignored. This mode is |
74 | entered only by debugging events obtained from the other two modes. | ||
70 | 75 | ||
71 | All kernel mode registers may be accessed, plus a few extra debugging specific registers. | 76 | All kernel mode registers may be accessed, plus a few extra debugging |
77 | specific registers. | ||
72 | 78 | ||
73 | 79 | ||
74 | ================================= | 80 | ================================= |
75 | INTERNAL KERNEL-MODE REGISTER ABI | 81 | INTERNAL KERNEL-MODE REGISTER ABI |
76 | ================================= | 82 | ================================= |
77 | 83 | ||
78 | There are a number of permanent register assignments that are set up by entry.S in the exception | 84 | There are a number of permanent register assignments that are set up by |
79 | prologue. Note that there is a complete set of exception prologues for each of user->kernel | 85 | entry.S in the exception prologue. Note that there is a complete set of |
80 | transition and kernel->kernel transition. There are also user->debug and kernel->debug mode | 86 | exception prologues for each of user->kernel transition and kernel->kernel |
81 | transition prologues. | 87 | transition. There are also user->debug and kernel->debug mode transition |
88 | prologues. | ||
82 | 89 | ||
83 | 90 | ||
84 | REGISTER FLAVOUR USE | 91 | REGISTER FLAVOUR USE |
85 | =============== ======= ==================================================== | 92 | =============== ======= ============================================== |
86 | GR1 Supervisor stack pointer | 93 | GR1 Supervisor stack pointer |
87 | GR15 Current thread info pointer | 94 | GR15 Current thread info pointer |
88 | GR16 GP-Rel base register for small data | 95 | GR16 GP-Rel base register for small data |
@@ -92,10 +99,12 @@ transition prologues. | |||
92 | GR31 NOMMU Destroyed by debug mode entry | 99 | GR31 NOMMU Destroyed by debug mode entry |
93 | GR31 MMU Destroyed by TLB miss kernel mode entry | 100 | GR31 MMU Destroyed by TLB miss kernel mode entry |
94 | CCR.ICC2 Virtual interrupt disablement tracking | 101 | CCR.ICC2 Virtual interrupt disablement tracking |
95 | CCCR.CC3 Cleared by exception prologue (atomic op emulation) | 102 | CCCR.CC3 Cleared by exception prologue |
103 | (atomic op emulation) | ||
96 | SCR0 MMU See mmu-layout.txt. | 104 | SCR0 MMU See mmu-layout.txt. |
97 | SCR1 MMU See mmu-layout.txt. | 105 | SCR1 MMU See mmu-layout.txt. |
98 | SCR2 MMU Save for EAR0 (destroyed by icache insns in debug mode) | 106 | SCR2 MMU Save for EAR0 (destroyed by icache insns |
107 | in debug mode) | ||
99 | SCR3 MMU Save for GR31 during debug exceptions | 108 | SCR3 MMU Save for GR31 during debug exceptions |
100 | DAMR/IAMR NOMMU Fixed memory protection layout. | 109 | DAMR/IAMR NOMMU Fixed memory protection layout. |
101 | DAMR/IAMR MMU See mmu-layout.txt. | 110 | DAMR/IAMR MMU See mmu-layout.txt. |
@@ -104,18 +113,21 @@ transition prologues. | |||
104 | Certain registers are also used or modified across function calls: | 113 | Certain registers are also used or modified across function calls: |
105 | 114 | ||
106 | REGISTER CALL RETURN | 115 | REGISTER CALL RETURN |
107 | =============== =============================== =============================== | 116 | =============== =============================== ====================== |
108 | GR0 Fixed Zero - | 117 | GR0 Fixed Zero - |
109 | GR2 Function call frame pointer | 118 | GR2 Function call frame pointer |
110 | GR3 Special Preserved | 119 | GR3 Special Preserved |
111 | GR3-GR7 - Clobbered | 120 | GR3-GR7 - Clobbered |
112 | GR8 Function call arg #1 Return value (or clobbered) | 121 | GR8 Function call arg #1 Return value |
113 | GR9 Function call arg #2 Return value MSW (or clobbered) | 122 | (or clobbered) |
123 | GR9 Function call arg #2 Return value MSW | ||
124 | (or clobbered) | ||
114 | GR10-GR13 Function call arg #3-#6 Clobbered | 125 | GR10-GR13 Function call arg #3-#6 Clobbered |
115 | GR14 - Clobbered | 126 | GR14 - Clobbered |
116 | GR15-GR16 Special Preserved | 127 | GR15-GR16 Special Preserved |
117 | GR17-GR27 - Preserved | 128 | GR17-GR27 - Preserved |
118 | GR28-GR31 Special Only accessed explicitly | 129 | GR28-GR31 Special Only accessed |
130 | explicitly | ||
119 | LR Return address after CALL Clobbered | 131 | LR Return address after CALL Clobbered |
120 | CCR/CCCR - Mostly Clobbered | 132 | CCR/CCCR - Mostly Clobbered |
121 | 133 | ||
@@ -124,46 +136,53 @@ Certain registers are also used or modified across function calls: | |||
124 | INTERNAL DEBUG-MODE REGISTER ABI | 136 | INTERNAL DEBUG-MODE REGISTER ABI |
125 | ================================ | 137 | ================================ |
126 | 138 | ||
127 | This is the same as the kernel-mode register ABI for functions calls. The difference is that in | 139 | This is the same as the kernel-mode register ABI for functions calls. The |
128 | debug-mode there's a different stack and a different exception frame. Almost all the global | 140 | difference is that in debug-mode there's a different stack and a different |
129 | registers from kernel-mode (including the stack pointer) may be changed. | 141 | exception frame. Almost all the global registers from kernel-mode |
142 | (including the stack pointer) may be changed. | ||
130 | 143 | ||
131 | REGISTER FLAVOUR USE | 144 | REGISTER FLAVOUR USE |
132 | =============== ======= ==================================================== | 145 | =============== ======= ============================================== |
133 | GR1 Debug stack pointer | 146 | GR1 Debug stack pointer |
134 | GR16 GP-Rel base register for small data | 147 | GR16 GP-Rel base register for small data |
135 | GR31 Current debug exception frame pointer (__debug_frame) | 148 | GR31 Current debug exception frame pointer |
149 | (__debug_frame) | ||
136 | SCR3 MMU Saved value of GR31 | 150 | SCR3 MMU Saved value of GR31 |
137 | 151 | ||
138 | 152 | ||
139 | Note that debug mode is able to interfere with the kernel's emulated atomic ops, so it must be | 153 | Note that debug mode is able to interfere with the kernel's emulated atomic |
140 | exceedingly careful not to do any that would interact with the main kernel in this regard. Hence | 154 | ops, so it must be exceedingly careful not to do any that would interact |
141 | the debug mode code (gdbstub) is almost completely self-contained. The only external code used is | 155 | with the main kernel in this regard. Hence the debug mode code (gdbstub) is |
142 | the sprintf family of functions. | 156 | almost completely self-contained. The only external code used is the |
157 | sprintf family of functions. | ||
143 | 158 | ||
144 | Futhermore, break.S is so complicated because single-step mode does not switch off on entry to an | 159 | Futhermore, break.S is so complicated because single-step mode does not |
145 | exception. That means unless manually disabled, single-stepping will blithely go on stepping into | 160 | switch off on entry to an exception. That means unless manually disabled, |
146 | things like interrupts. See gdbstub.txt for more information. | 161 | single-stepping will blithely go on stepping into things like interrupts. |
162 | See gdbstub.txt for more information. | ||
147 | 163 | ||
148 | 164 | ||
149 | ========================== | 165 | ========================== |
150 | VIRTUAL INTERRUPT HANDLING | 166 | VIRTUAL INTERRUPT HANDLING |
151 | ========================== | 167 | ========================== |
152 | 168 | ||
153 | Because accesses to the PSR is so slow, and to disable interrupts we have to access it twice (once | 169 | Because accesses to the PSR is so slow, and to disable interrupts we have |
154 | to read and once to write), we don't actually disable interrupts at all if we don't have to. What | 170 | to access it twice (once to read and once to write), we don't actually |
155 | we do instead is use the ICC2 condition code flags to note virtual disablement, such that if we | 171 | disable interrupts at all if we don't have to. What we do instead is use |
156 | then do take an interrupt, we note the flag, really disable interrupts, set another flag and resume | 172 | the ICC2 condition code flags to note virtual disablement, such that if we |
157 | execution at the point the interrupt happened. Setting condition flags as a side effect of an | 173 | then do take an interrupt, we note the flag, really disable interrupts, set |
158 | arithmetic or logical instruction is really fast. This use of the ICC2 only occurs within the | 174 | another flag and resume execution at the point the interrupt happened. |
175 | Setting condition flags as a side effect of an arithmetic or logical | ||
176 | instruction is really fast. This use of the ICC2 only occurs within the | ||
159 | kernel - it does not affect userspace. | 177 | kernel - it does not affect userspace. |
160 | 178 | ||
161 | The flags we use are: | 179 | The flags we use are: |
162 | 180 | ||
163 | (*) CCR.ICC2.Z [Zero flag] | 181 | (*) CCR.ICC2.Z [Zero flag] |
164 | 182 | ||
165 | Set to virtually disable interrupts, clear when interrupts are virtually enabled. Can be | 183 | Set to virtually disable interrupts, clear when interrupts are |
166 | modified by logical instructions without affecting the Carry flag. | 184 | virtually enabled. Can be modified by logical instructions without |
185 | affecting the Carry flag. | ||
167 | 186 | ||
168 | (*) CCR.ICC2.C [Carry flag] | 187 | (*) CCR.ICC2.C [Carry flag] |
169 | 188 | ||
@@ -176,8 +195,9 @@ What happens is this: | |||
176 | 195 | ||
177 | ICC2.Z is 0, ICC2.C is 1. | 196 | ICC2.Z is 0, ICC2.C is 1. |
178 | 197 | ||
179 | (2) An interrupt occurs. The exception prologue examines ICC2.Z and determines that nothing needs | 198 | (2) An interrupt occurs. The exception prologue examines ICC2.Z and |
180 | doing. This is done simply with an unlikely BEQ instruction. | 199 | determines that nothing needs doing. This is done simply with an |
200 | unlikely BEQ instruction. | ||
181 | 201 | ||
182 | (3) The interrupts are disabled (local_irq_disable) | 202 | (3) The interrupts are disabled (local_irq_disable) |
183 | 203 | ||
@@ -187,48 +207,56 @@ What happens is this: | |||
187 | 207 | ||
188 | ICC2.Z would be set to 0. | 208 | ICC2.Z would be set to 0. |
189 | 209 | ||
190 | A TIHI #2 instruction (trap #2 if condition HI - Z==0 && C==0) would be used to trap if | 210 | A TIHI #2 instruction (trap #2 if condition HI - Z==0 && C==0) would |
191 | interrupts were now virtually enabled, but physically disabled - which they're not, so the | 211 | be used to trap if interrupts were now virtually enabled, but |
192 | trap isn't taken. The kernel would then be back to state (1). | 212 | physically disabled - which they're not, so the trap isn't taken. The |
213 | kernel would then be back to state (1). | ||
193 | 214 | ||
194 | (5) An interrupt occurs. The exception prologue examines ICC2.Z and determines that the interrupt | 215 | (5) An interrupt occurs. The exception prologue examines ICC2.Z and |
195 | shouldn't actually have happened. It jumps aside, and there disabled interrupts by setting | 216 | determines that the interrupt shouldn't actually have happened. It |
196 | PSR.PIL to 14 and then it clears ICC2.C. | 217 | jumps aside, and there disabled interrupts by setting PSR.PIL to 14 |
218 | and then it clears ICC2.C. | ||
197 | 219 | ||
198 | (6) If interrupts were then saved and disabled again (local_irq_save): | 220 | (6) If interrupts were then saved and disabled again (local_irq_save): |
199 | 221 | ||
200 | ICC2.Z would be shifted into the save variable and masked off (giving a 1). | 222 | ICC2.Z would be shifted into the save variable and masked off |
223 | (giving a 1). | ||
201 | 224 | ||
202 | ICC2.Z would then be set to 1 (thus unchanged), and ICC2.C would be unaffected (ie: 0). | 225 | ICC2.Z would then be set to 1 (thus unchanged), and ICC2.C would be |
226 | unaffected (ie: 0). | ||
203 | 227 | ||
204 | (7) If interrupts were then restored from state (6) (local_irq_restore): | 228 | (7) If interrupts were then restored from state (6) (local_irq_restore): |
205 | 229 | ||
206 | ICC2.Z would be set to indicate the result of XOR'ing the saved value (ie: 1) with 1, which | 230 | ICC2.Z would be set to indicate the result of XOR'ing the saved |
207 | gives a result of 0 - thus leaving ICC2.Z set. | 231 | value (ie: 1) with 1, which gives a result of 0 - thus leaving |
232 | ICC2.Z set. | ||
208 | 233 | ||
209 | ICC2.C would remain unaffected (ie: 0). | 234 | ICC2.C would remain unaffected (ie: 0). |
210 | 235 | ||
211 | A TIHI #2 instruction would be used to again assay the current state, but this would do | 236 | A TIHI #2 instruction would be used to again assay the current state, |
212 | nothing as Z==1. | 237 | but this would do nothing as Z==1. |
213 | 238 | ||
214 | (8) If interrupts were then enabled (local_irq_enable): | 239 | (8) If interrupts were then enabled (local_irq_enable): |
215 | 240 | ||
216 | ICC2.Z would be cleared. ICC2.C would be left unaffected. Both flags would now be 0. | 241 | ICC2.Z would be cleared. ICC2.C would be left unaffected. Both |
242 | flags would now be 0. | ||
217 | 243 | ||
218 | A TIHI #2 instruction again issued to assay the current state would then trap as both Z==0 | 244 | A TIHI #2 instruction again issued to assay the current state would |
219 | [interrupts virtually enabled] and C==0 [interrupts really disabled] would then be true. | 245 | then trap as both Z==0 [interrupts virtually enabled] and C==0 |
246 | [interrupts really disabled] would then be true. | ||
220 | 247 | ||
221 | (9) The trap #2 handler would simply enable hardware interrupts (set PSR.PIL to 0), set ICC2.C to | 248 | (9) The trap #2 handler would simply enable hardware interrupts |
222 | 1 and return. | 249 | (set PSR.PIL to 0), set ICC2.C to 1 and return. |
223 | 250 | ||
224 | (10) Immediately upon returning, the pending interrupt would be taken. | 251 | (10) Immediately upon returning, the pending interrupt would be taken. |
225 | 252 | ||
226 | (11) The interrupt handler would take the path of actually processing the interrupt (ICC2.Z is | 253 | (11) The interrupt handler would take the path of actually processing the |
227 | clear, BEQ fails as per step (2)). | 254 | interrupt (ICC2.Z is clear, BEQ fails as per step (2)). |
228 | 255 | ||
229 | (12) The interrupt handler would then set ICC2.C to 1 since hardware interrupts are definitely | 256 | (12) The interrupt handler would then set ICC2.C to 1 since hardware |
230 | enabled - or else the kernel wouldn't be here. | 257 | interrupts are definitely enabled - or else the kernel wouldn't be here. |
231 | 258 | ||
232 | (13) On return from the interrupt handler, things would be back to state (1). | 259 | (13) On return from the interrupt handler, things would be back to state (1). |
233 | 260 | ||
234 | This trap (#2) is only available in kernel mode. In user mode it will result in SIGILL. | 261 | This trap (#2) is only available in kernel mode. In user mode it will |
262 | result in SIGILL. | ||
diff --git a/Documentation/i2c/busses/i2c-parport b/Documentation/i2c/busses/i2c-parport index d9f23c0763f1..77b995dfca22 100644 --- a/Documentation/i2c/busses/i2c-parport +++ b/Documentation/i2c/busses/i2c-parport | |||
@@ -12,18 +12,22 @@ meant as a replacement for the older, individual drivers: | |||
12 | teletext adapters) | 12 | teletext adapters) |
13 | 13 | ||
14 | It currently supports the following devices: | 14 | It currently supports the following devices: |
15 | * Philips adapter | 15 | * (type=0) Philips adapter |
16 | * home brew teletext adapter | 16 | * (type=1) home brew teletext adapter |
17 | * Velleman K8000 adapter | 17 | * (type=2) Velleman K8000 adapter |
18 | * ELV adapter | 18 | * (type=3) ELV adapter |
19 | * Analog Devices evaluation boards (ADM1025, ADM1030, ADM1031, ADM1032) | 19 | * (type=4) Analog Devices ADM1032 evaluation board |
20 | * Barco LPT->DVI (K5800236) adapter | 20 | * (type=5) Analog Devices evaluation boards: ADM1025, ADM1030, ADM1031 |
21 | * (type=6) Barco LPT->DVI (K5800236) adapter | ||
21 | 22 | ||
22 | These devices use different pinout configurations, so you have to tell | 23 | These devices use different pinout configurations, so you have to tell |
23 | the driver what you have, using the type module parameter. There is no | 24 | the driver what you have, using the type module parameter. There is no |
24 | way to autodetect the devices. Support for different pinout configurations | 25 | way to autodetect the devices. Support for different pinout configurations |
25 | can be easily added when needed. | 26 | can be easily added when needed. |
26 | 27 | ||
28 | Earlier kernels defaulted to type=0 (Philips). But now, if the type | ||
29 | parameter is missing, the driver will simply fail to initialize. | ||
30 | |||
27 | 31 | ||
28 | Building your own adapter | 32 | Building your own adapter |
29 | ------------------------- | 33 | ------------------------- |
diff --git a/Documentation/input/joystick-parport.txt b/Documentation/input/joystick-parport.txt index 88a011c9f985..d537c48cc6d0 100644 --- a/Documentation/input/joystick-parport.txt +++ b/Documentation/input/joystick-parport.txt | |||
@@ -36,12 +36,12 @@ with them. | |||
36 | 36 | ||
37 | All NES and SNES use the same synchronous serial protocol, clocked from | 37 | All NES and SNES use the same synchronous serial protocol, clocked from |
38 | the computer's side (and thus timing insensitive). To allow up to 5 NES | 38 | the computer's side (and thus timing insensitive). To allow up to 5 NES |
39 | and/or SNES gamepads connected to the parallel port at once, the output | 39 | and/or SNES gamepads and/or SNES mice connected to the parallel port at once, |
40 | lines of the parallel port are shared, while one of 5 available input lines | 40 | the output lines of the parallel port are shared, while one of 5 available |
41 | is assigned to each gamepad. | 41 | input lines is assigned to each gamepad. |
42 | 42 | ||
43 | This protocol is handled by the gamecon.c driver, so that's the one | 43 | This protocol is handled by the gamecon.c driver, so that's the one |
44 | you'll use for NES and SNES gamepads. | 44 | you'll use for NES, SNES gamepads and SNES mice. |
45 | 45 | ||
46 | The main problem with PC parallel ports is that they don't have +5V power | 46 | The main problem with PC parallel ports is that they don't have +5V power |
47 | source on any of their pins. So, if you want a reliable source of power | 47 | source on any of their pins. So, if you want a reliable source of power |
@@ -106,7 +106,7 @@ A, Turbo B, Select and Start, and is connected through 5 wires, then it is | |||
106 | either a NES or NES clone and will work with this connection. SNES gamepads | 106 | either a NES or NES clone and will work with this connection. SNES gamepads |
107 | also use 5 wires, but have more buttons. They will work as well, of course. | 107 | also use 5 wires, but have more buttons. They will work as well, of course. |
108 | 108 | ||
109 | Pinout for NES gamepads Pinout for SNES gamepads | 109 | Pinout for NES gamepads Pinout for SNES gamepads and mice |
110 | 110 | ||
111 | +----> Power +-----------------------\ | 111 | +----> Power +-----------------------\ |
112 | | 7 | o o o o | x x o | 1 | 112 | | 7 | o o o o | x x o | 1 |
@@ -454,6 +454,7 @@ uses the following kernel/module command line: | |||
454 | 6 | N64 pad | 454 | 6 | N64 pad |
455 | 7 | Sony PSX controller | 455 | 7 | Sony PSX controller |
456 | 8 | Sony PSX DDR controller | 456 | 8 | Sony PSX DDR controller |
457 | 9 | SNES mouse | ||
457 | 458 | ||
458 | The exact type of the PSX controller type is autoprobed when used so | 459 | The exact type of the PSX controller type is autoprobed when used so |
459 | hot swapping should work (but is not recomended). | 460 | hot swapping should work (but is not recomended). |
diff --git a/Documentation/isdn/README.gigaset b/Documentation/isdn/README.gigaset new file mode 100644 index 000000000000..85a64defd385 --- /dev/null +++ b/Documentation/isdn/README.gigaset | |||
@@ -0,0 +1,286 @@ | |||
1 | GigaSet 307x Device Driver | ||
2 | ========================== | ||
3 | |||
4 | 1. Requirements | ||
5 | ------------ | ||
6 | 1.1. Hardware | ||
7 | -------- | ||
8 | This release supports the connection of the Gigaset 307x/417x family of | ||
9 | ISDN DECT bases via Gigaset M101 Data, Gigaset M105 Data or direct USB | ||
10 | connection. The following devices are reported to be compatible: | ||
11 | 307x/417x: | ||
12 | Gigaset SX255isdn | ||
13 | Gigaset SX353isdn | ||
14 | Sinus 45 [AB] isdn (Deutsche Telekom) | ||
15 | Sinus 721X/XA | ||
16 | Vox Chicago 390 ISDN (KPN Telecom) | ||
17 | M101: | ||
18 | Sinus 45 Data 1 (Telekom) | ||
19 | M105: | ||
20 | Gigaset USB Adapter DECT | ||
21 | Sinus 45 Data 2 (Telekom) | ||
22 | Sinus 721 data | ||
23 | Chicago 390 USB (KPN) | ||
24 | See also http://www.erbze.info/sinus_gigaset.htm and | ||
25 | http://gigaset307x.sourceforge.net/ | ||
26 | |||
27 | We had also reports from users of Gigaset M105 who could use the drivers | ||
28 | with SX 100 and CX 100 ISDN bases (only in unimodem mode, see section 2.4.) | ||
29 | If you have another device that works with our driver, please let us know. | ||
30 | For example, Gigaset SX205isdn/Sinus 721 X SE and Gigaset SX303isdn bases | ||
31 | are just versions without answering machine of models known to work, so | ||
32 | they should work just as well; but so far we are lacking positive reports | ||
33 | on these. | ||
34 | |||
35 | Chances of getting an USB device to work are good if the output of | ||
36 | lsusb | ||
37 | at the command line contains one of the following: | ||
38 | ID 0681:0001 | ||
39 | ID 0681:0002 | ||
40 | ID 0681:0009 | ||
41 | ID 0681:0021 | ||
42 | ID 0681:0022 | ||
43 | |||
44 | 1.2. Software | ||
45 | -------- | ||
46 | The driver works with ISDN4linux and so can be used with any software | ||
47 | which is able to use ISDN4linux for ISDN connections (voice or data). | ||
48 | CAPI4Linux support is planned but not yet available. | ||
49 | |||
50 | There are some user space tools available at | ||
51 | http://sourceforge.net/projects/gigaset307x/ | ||
52 | which provide access to additional device specific functions like SMS, | ||
53 | phonebook or call journal. | ||
54 | |||
55 | |||
56 | 2. How to use the driver | ||
57 | --------------------- | ||
58 | 2.1. Modules | ||
59 | ------- | ||
60 | To get the device working, you have to load the proper kernel module. You | ||
61 | can do this using | ||
62 | modprobe modulename | ||
63 | where modulename is usb_gigaset (M105) or bas_gigaset (direct USB | ||
64 | connection to the base). | ||
65 | |||
66 | 2.2. Device nodes for user space programs | ||
67 | ------------------------------------ | ||
68 | The device can be accessed from user space (eg. by the user space tools | ||
69 | mentioned in 1.2.) through the device nodes: | ||
70 | |||
71 | - /dev/ttyGU0 for M105 (USB data boxes) | ||
72 | - /dev/ttyGB0 for the base driver (direct USB connection) | ||
73 | |||
74 | You can also select a "default device" which is used by the frontends when | ||
75 | no device node is given as parameter, by creating a symlink /dev/ttyG to | ||
76 | one of them, eg.: | ||
77 | |||
78 | ln -s /dev/ttyGB0 /dev/ttyG | ||
79 | |||
80 | 2.3. ISDN4linux | ||
81 | ---------- | ||
82 | This is the "normal" mode of operation. After loading the module you can | ||
83 | set up the ISDN system just as you'd do with any ISDN card. | ||
84 | Your distribution should provide some configuration utility. | ||
85 | If not, you can use some HOWTOs like | ||
86 | http://www.linuxhaven.de/dlhp/HOWTO/DE-ISDN-HOWTO-5.html | ||
87 | If this doesn't work, because you have some recent device like SX100 where | ||
88 | debug output (see section 3.2.) shows something like this when dialing | ||
89 | CMD Received: ERROR | ||
90 | Available Params: 0 | ||
91 | Connection State: 0, Response: -1 | ||
92 | gigaset_process_response: resp_code -1 in ConState 0 ! | ||
93 | Timeout occurred | ||
94 | you might need to use unimodem mode: | ||
95 | |||
96 | 2.4. Unimodem mode | ||
97 | ------------- | ||
98 | This is needed for some devices [e.g. SX100] as they have problems with | ||
99 | the "normal" commands. | ||
100 | |||
101 | If you have installed the command line tool gigacontr, you can enter | ||
102 | unimodem mode using | ||
103 | gigacontr --mode unimodem | ||
104 | You can switch back using | ||
105 | gigacontr --mode isdn | ||
106 | |||
107 | You can also load the driver using e.g. | ||
108 | modprobe usb_gigaset startmode=0 | ||
109 | to prevent the driver from starting in "isdn4linux mode". | ||
110 | |||
111 | In this mode the device works like a modem connected to a serial port | ||
112 | (the /dev/ttyGU0, ... mentioned above) which understands the commands | ||
113 | ATZ init, reset | ||
114 | => OK or ERROR | ||
115 | ATD | ||
116 | ATDT dial | ||
117 | => OK, CONNECT, | ||
118 | BUSY, | ||
119 | NO DIAL TONE, | ||
120 | NO CARRIER, | ||
121 | NO ANSWER | ||
122 | <pause>+++<pause> change to command mode when connected | ||
123 | ATH hangup | ||
124 | |||
125 | You can use some configuration tool of your distribution to configure this | ||
126 | "modem" or configure pppd/wvdial manually. There are some example ppp | ||
127 | configuration files and chat scripts in the gigaset-VERSION/ppp directory. | ||
128 | Please note that the USB drivers are not able to change the state of the | ||
129 | control lines (the M105 driver can be configured to use some undocumented | ||
130 | control requests, if you really need the control lines, though). This means | ||
131 | you must use "Stupid Mode" if you are using wvdial or you should use the | ||
132 | nocrtscts option of pppd. | ||
133 | You must also assure that the ppp_async module is loaded with the parameter | ||
134 | flag_time=0. You can do this e.g. by adding a line like | ||
135 | |||
136 | options ppp_async flag_time=0 | ||
137 | |||
138 | to /etc/modprobe.conf. If your distribution has some local module | ||
139 | configuration file like /etc/modprobe.conf.local, | ||
140 | using that should be preferred. | ||
141 | |||
142 | 2.5. Call-ID (CID) mode | ||
143 | ------------------ | ||
144 | Call-IDs are numbers used to tag commands to, and responses from, the | ||
145 | Gigaset base in order to support the simultaneous handling of multiple | ||
146 | ISDN calls. Their use can be enabled ("CID mode") or disabled ("Unimodem | ||
147 | mode"). Without Call-IDs (in Unimodem mode), only a very limited set of | ||
148 | functions is available. It allows outgoing data connections only, but | ||
149 | does not signal incoming calls or other base events. | ||
150 | |||
151 | DECT cordless data devices (M10x) permanently occupy the cordless | ||
152 | connection to the base while Call-IDs are activated. As the Gigaset | ||
153 | bases only support one DECT data connection at a time, this prevents | ||
154 | other DECT cordless data devices from accessing the base. | ||
155 | |||
156 | During active operation, the driver switches to the necessary mode | ||
157 | automatically. However, for the reasons above, the mode chosen when | ||
158 | the device is not in use (idle) can be selected by the user. | ||
159 | - If you want to receive incoming calls, you can use the default | ||
160 | settings (CID mode). | ||
161 | - If you have several DECT data devices (M10x) which you want to use | ||
162 | in turn, select Unimodem mode by passing the parameter "cidmode=0" to | ||
163 | the driver ("modprobe usb_gigaset cidmode=0" or modprobe.conf). | ||
164 | |||
165 | If you want both of these at once, you are out of luck. | ||
166 | |||
167 | You can also use /sys/module/<name>/parameters/cidmode for changing | ||
168 | the CID mode setting (<name> is usb_gigaset or bas_gigaset). | ||
169 | |||
170 | |||
171 | 3. Troubleshooting | ||
172 | --------------- | ||
173 | 3.1. Solutions to frequently reported problems | ||
174 | ----------------------------------------- | ||
175 | Problem: | ||
176 | You have a slow provider and isdn4linux gives up dialing too early. | ||
177 | Solution: | ||
178 | Load the isdn module using the dialtimeout option. You can do this e.g. | ||
179 | by adding a line like | ||
180 | |||
181 | options isdn dialtimeout=15 | ||
182 | |||
183 | to /etc/modprobe.conf. If your distribution has some local module | ||
184 | configuration file like /etc/modprobe.conf.local, | ||
185 | using that should be preferred. | ||
186 | |||
187 | Problem: | ||
188 | Your isdn script aborts with a message about isdnlog. | ||
189 | Solution: | ||
190 | Try deactivating (or commenting out) isdnlog. This driver does not | ||
191 | support it. | ||
192 | |||
193 | Problem: | ||
194 | You have two or more DECT data adapters (M101/M105) and only the | ||
195 | first one you turn on works. | ||
196 | Solution: | ||
197 | Select Unimodem mode for all DECT data adapters. (see section 2.4.) | ||
198 | |||
199 | 3.2. Telling the driver to provide more information | ||
200 | ---------------------------------------------- | ||
201 | Building the driver with the "Gigaset debugging" kernel configuration | ||
202 | option (CONFIG_GIGASET_DEBUG) gives it the ability to produce additional | ||
203 | information useful for debugging. | ||
204 | |||
205 | You can control the amount of debugging information the driver produces by | ||
206 | writing an appropriate value to /sys/module/gigaset/parameters/debug, e.g. | ||
207 | echo 0 > /sys/module/gigaset/parameters/debug | ||
208 | switches off debugging output completely, | ||
209 | echo 0x10a020 > /sys/module/gigaset/parameters/debug | ||
210 | enables the standard set of debugging output messages. These values are | ||
211 | bit patterns where every bit controls a certain type of debugging output. | ||
212 | See the constants DEBUG_* in the source file gigaset.h for details. | ||
213 | |||
214 | The initial value can be set using the debug parameter when loading the | ||
215 | module "gigaset", e.g. by adding a line | ||
216 | options gigaset debug=0 | ||
217 | to /etc/modprobe.conf, ... | ||
218 | |||
219 | Generated debugging information can be found | ||
220 | - as output of the command | ||
221 | dmesg | ||
222 | - in system log files written by your syslog daemon, usually | ||
223 | in /var/log/, e.g. /var/log/messages. | ||
224 | |||
225 | 3.3. Reporting problems and bugs | ||
226 | --------------------------- | ||
227 | If you can't solve problems with the driver on your own, feel free to | ||
228 | use one of the forums, bug trackers, or mailing lists on | ||
229 | http://sourceforge.net/projects/gigaset307x | ||
230 | or write an electronic mail to the maintainers. | ||
231 | |||
232 | Try to provide as much information as possible, such as | ||
233 | - distribution | ||
234 | - kernel version (uname -r) | ||
235 | - gcc version (gcc --version) | ||
236 | - hardware architecture (uname -m, ...) | ||
237 | - type and firmware version of your device (base and wireless module, | ||
238 | if any) | ||
239 | - output of "lsusb -v" (if using an USB device) | ||
240 | - error messages | ||
241 | - relevant system log messages (it would help if you activate debug | ||
242 | output as described in 3.2.) | ||
243 | |||
244 | For help with general configuration problems not specific to our driver, | ||
245 | such as isdn4linux and network configuration issues, please refer to the | ||
246 | appropriate forums and newsgroups. | ||
247 | |||
248 | 3.4. Reporting problem solutions | ||
249 | --------------------------- | ||
250 | If you solved a problem with our drivers, wrote startup scripts for your | ||
251 | distribution, ... feel free to contact us (using one of the places | ||
252 | mentioned in 3.3.). We'd like to add scripts, hints, documentation | ||
253 | to the driver and/or the project web page. | ||
254 | |||
255 | |||
256 | 4. Links, other software | ||
257 | --------------------- | ||
258 | - Sourceforge project developing this driver and associated tools | ||
259 | http://sourceforge.net/projects/gigaset307x | ||
260 | - Yahoo! Group on the Siemens Gigaset family of devices | ||
261 | http://de.groups.yahoo.com/group/Siemens-Gigaset | ||
262 | - Siemens Gigaset/T-Sinus compatibility table | ||
263 | http://www.erbze.info/sinus_gigaset.htm | ||
264 | |||
265 | |||
266 | 5. Credits | ||
267 | ------- | ||
268 | Thanks to | ||
269 | |||
270 | Karsten Keil | ||
271 | for his help with isdn4linux | ||
272 | Deti Fliegl | ||
273 | for his base driver code | ||
274 | Dennis Dietrich | ||
275 | for his kernel 2.6 patches | ||
276 | Andreas Rummel | ||
277 | for his work and logs to get unimodem mode working | ||
278 | Andreas Degert | ||
279 | for his logs and patches to get cx 100 working | ||
280 | Dietrich Feist | ||
281 | for his generous donation of one M105 and two M101 cordless adapters | ||
282 | Christoph Schweers | ||
283 | for his generous donation of a M34 device | ||
284 | |||
285 | and all the other people who sent logs and other information. | ||
286 | |||
diff --git a/Documentation/kbuild/modules.txt b/Documentation/kbuild/modules.txt index fcccf2432f98..61fc079eb966 100644 --- a/Documentation/kbuild/modules.txt +++ b/Documentation/kbuild/modules.txt | |||
@@ -44,7 +44,7 @@ What is covered within this file is mainly information to authors | |||
44 | of modules. The author of an external modules should supply | 44 | of modules. The author of an external modules should supply |
45 | a makefile that hides most of the complexity so one only has to type | 45 | a makefile that hides most of the complexity so one only has to type |
46 | 'make' to build the module. A complete example will be present in | 46 | 'make' to build the module. A complete example will be present in |
47 | chapter ¤. Creating a kbuild file for an external module". | 47 | chapter 4, "Creating a kbuild file for an external module". |
48 | 48 | ||
49 | 49 | ||
50 | === 2. How to build external modules | 50 | === 2. How to build external modules |
diff --git a/Documentation/kernel-parameters.txt b/Documentation/kernel-parameters.txt index f8cb55c30b0f..b3a6187e5305 100644 --- a/Documentation/kernel-parameters.txt +++ b/Documentation/kernel-parameters.txt | |||
@@ -1,4 +1,4 @@ | |||
1 | February 2003 Kernel Parameters v2.5.59 | 1 | Kernel Parameters |
2 | ~~~~~~~~~~~~~~~~~ | 2 | ~~~~~~~~~~~~~~~~~ |
3 | 3 | ||
4 | The following is a consolidated list of the kernel parameters as implemented | 4 | The following is a consolidated list of the kernel parameters as implemented |
@@ -17,9 +17,17 @@ are specified on the kernel command line with the module name plus | |||
17 | 17 | ||
18 | usbcore.blinkenlights=1 | 18 | usbcore.blinkenlights=1 |
19 | 19 | ||
20 | The text in square brackets at the beginning of the description states the | 20 | This document may not be entirely up to date and comprehensive. The command |
21 | restrictions on the kernel for the said kernel parameter to be valid. The | 21 | "modinfo -p ${modulename}" shows a current list of all parameters of a loadable |
22 | restrictions referred to are that the relevant option is valid if: | 22 | module. Loadable modules, after being loaded into the running kernel, also |
23 | reveal their parameters in /sys/module/${modulename}/parameters/. Some of these | ||
24 | parameters may be changed at runtime by the command | ||
25 | "echo -n ${value} > /sys/module/${modulename}/parameters/${parm}". | ||
26 | |||
27 | The parameters listed below are only valid if certain kernel build options were | ||
28 | enabled and if respective hardware is present. The text in square brackets at | ||
29 | the beginning of each description states the restrictions within which a | ||
30 | parameter is applicable: | ||
23 | 31 | ||
24 | ACPI ACPI support is enabled. | 32 | ACPI ACPI support is enabled. |
25 | ALSA ALSA sound support is enabled. | 33 | ALSA ALSA sound support is enabled. |
@@ -1046,10 +1054,10 @@ running once the system is up. | |||
1046 | noltlbs [PPC] Do not use large page/tlb entries for kernel | 1054 | noltlbs [PPC] Do not use large page/tlb entries for kernel |
1047 | lowmem mapping on PPC40x. | 1055 | lowmem mapping on PPC40x. |
1048 | 1056 | ||
1049 | nomce [IA-32] Machine Check Exception | ||
1050 | |||
1051 | nomca [IA-64] Disable machine check abort handling | 1057 | nomca [IA-64] Disable machine check abort handling |
1052 | 1058 | ||
1059 | nomce [IA-32] Machine Check Exception | ||
1060 | |||
1053 | noresidual [PPC] Don't use residual data on PReP machines. | 1061 | noresidual [PPC] Don't use residual data on PReP machines. |
1054 | 1062 | ||
1055 | noresume [SWSUSP] Disables resume and restores original swap | 1063 | noresume [SWSUSP] Disables resume and restores original swap |
@@ -1682,20 +1690,6 @@ running once the system is up. | |||
1682 | 1690 | ||
1683 | 1691 | ||
1684 | ______________________________________________________________________ | 1692 | ______________________________________________________________________ |
1685 | Changelog: | ||
1686 | |||
1687 | 2000-06-?? Mr. Unknown | ||
1688 | The last known update (for 2.4.0) - the changelog was not kept before. | ||
1689 | |||
1690 | 2002-11-24 Petr Baudis <pasky@ucw.cz> | ||
1691 | Randy Dunlap <randy.dunlap@verizon.net> | ||
1692 | Update for 2.5.49, description for most of the options introduced, | ||
1693 | references to other documentation (C files, READMEs, ..), added S390, | ||
1694 | PPC, SPARC, MTD, ALSA and OSS category. Minor corrections and | ||
1695 | reformatting. | ||
1696 | |||
1697 | 2005-10-19 Randy Dunlap <rdunlap@xenotime.net> | ||
1698 | Lots of typos, whitespace, some reformatting. | ||
1699 | 1693 | ||
1700 | TODO: | 1694 | TODO: |
1701 | 1695 | ||
diff --git a/Documentation/laptop-mode.txt b/Documentation/laptop-mode.txt index b18e21675906..5696e879449b 100644 --- a/Documentation/laptop-mode.txt +++ b/Documentation/laptop-mode.txt | |||
@@ -919,11 +919,11 @@ int main(int argc, char **argv) | |||
919 | int settle_time = 60; | 919 | int settle_time = 60; |
920 | 920 | ||
921 | /* Parse the simple command-line */ | 921 | /* Parse the simple command-line */ |
922 | if (ac == 2) | 922 | if (argc == 2) |
923 | disk = av[1]; | 923 | disk = argv[1]; |
924 | else if (ac == 4) { | 924 | else if (argc == 4) { |
925 | settle_time = atoi(av[2]); | 925 | settle_time = atoi(argv[2]); |
926 | disk = av[3]; | 926 | disk = argv[3]; |
927 | } else | 927 | } else |
928 | usage(); | 928 | usage(); |
929 | 929 | ||
diff --git a/Documentation/leds-class.txt b/Documentation/leds-class.txt new file mode 100644 index 000000000000..8c35c0426110 --- /dev/null +++ b/Documentation/leds-class.txt | |||
@@ -0,0 +1,71 @@ | |||
1 | LED handling under Linux | ||
2 | ======================== | ||
3 | |||
4 | If you're reading this and thinking about keyboard leds, these are | ||
5 | handled by the input subsystem and the led class is *not* needed. | ||
6 | |||
7 | In its simplest form, the LED class just allows control of LEDs from | ||
8 | userspace. LEDs appear in /sys/class/leds/. The brightness file will | ||
9 | set the brightness of the LED (taking a value 0-255). Most LEDs don't | ||
10 | have hardware brightness support so will just be turned on for non-zero | ||
11 | brightness settings. | ||
12 | |||
13 | The class also introduces the optional concept of an LED trigger. A trigger | ||
14 | is a kernel based source of led events. Triggers can either be simple or | ||
15 | complex. A simple trigger isn't configurable and is designed to slot into | ||
16 | existing subsystems with minimal additional code. Examples are the ide-disk, | ||
17 | nand-disk and sharpsl-charge triggers. With led triggers disabled, the code | ||
18 | optimises away. | ||
19 | |||
20 | Complex triggers whilst available to all LEDs have LED specific | ||
21 | parameters and work on a per LED basis. The timer trigger is an example. | ||
22 | |||
23 | You can change triggers in a similar manner to the way an IO scheduler | ||
24 | is chosen (via /sys/class/leds/<device>/trigger). Trigger specific | ||
25 | parameters can appear in /sys/class/leds/<device> once a given trigger is | ||
26 | selected. | ||
27 | |||
28 | |||
29 | Design Philosophy | ||
30 | ================= | ||
31 | |||
32 | The underlying design philosophy is simplicity. LEDs are simple devices | ||
33 | and the aim is to keep a small amount of code giving as much functionality | ||
34 | as possible. Please keep this in mind when suggesting enhancements. | ||
35 | |||
36 | |||
37 | LED Device Naming | ||
38 | ================= | ||
39 | |||
40 | Is currently of the form: | ||
41 | |||
42 | "devicename:colour" | ||
43 | |||
44 | There have been calls for LED properties such as colour to be exported as | ||
45 | individual led class attributes. As a solution which doesn't incur as much | ||
46 | overhead, I suggest these become part of the device name. The naming scheme | ||
47 | above leaves scope for further attributes should they be needed. | ||
48 | |||
49 | |||
50 | Known Issues | ||
51 | ============ | ||
52 | |||
53 | The LED Trigger core cannot be a module as the simple trigger functions | ||
54 | would cause nightmare dependency issues. I see this as a minor issue | ||
55 | compared to the benefits the simple trigger functionality brings. The | ||
56 | rest of the LED subsystem can be modular. | ||
57 | |||
58 | Some leds can be programmed to flash in hardware. As this isn't a generic | ||
59 | LED device property, this should be exported as a device specific sysfs | ||
60 | attribute rather than part of the class if this functionality is required. | ||
61 | |||
62 | |||
63 | Future Development | ||
64 | ================== | ||
65 | |||
66 | At the moment, a trigger can't be created specifically for a single LED. | ||
67 | There are a number of cases where a trigger might only be mappable to a | ||
68 | particular LED (ACPI?). The addition of triggers provided by the LED driver | ||
69 | should cover this option and be possible to add without breaking the | ||
70 | current interface. | ||
71 | |||
diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt new file mode 100644 index 000000000000..92f0056d928c --- /dev/null +++ b/Documentation/memory-barriers.txt | |||
@@ -0,0 +1,1941 @@ | |||
1 | ============================ | ||
2 | LINUX KERNEL MEMORY BARRIERS | ||
3 | ============================ | ||
4 | |||
5 | By: David Howells <dhowells@redhat.com> | ||
6 | |||
7 | Contents: | ||
8 | |||
9 | (*) Abstract memory access model. | ||
10 | |||
11 | - Device operations. | ||
12 | - Guarantees. | ||
13 | |||
14 | (*) What are memory barriers? | ||
15 | |||
16 | - Varieties of memory barrier. | ||
17 | - What may not be assumed about memory barriers? | ||
18 | - Data dependency barriers. | ||
19 | - Control dependencies. | ||
20 | - SMP barrier pairing. | ||
21 | - Examples of memory barrier sequences. | ||
22 | |||
23 | (*) Explicit kernel barriers. | ||
24 | |||
25 | - Compiler barrier. | ||
26 | - The CPU memory barriers. | ||
27 | - MMIO write barrier. | ||
28 | |||
29 | (*) Implicit kernel memory barriers. | ||
30 | |||
31 | - Locking functions. | ||
32 | - Interrupt disabling functions. | ||
33 | - Miscellaneous functions. | ||
34 | |||
35 | (*) Inter-CPU locking barrier effects. | ||
36 | |||
37 | - Locks vs memory accesses. | ||
38 | - Locks vs I/O accesses. | ||
39 | |||
40 | (*) Where are memory barriers needed? | ||
41 | |||
42 | - Interprocessor interaction. | ||
43 | - Atomic operations. | ||
44 | - Accessing devices. | ||
45 | - Interrupts. | ||
46 | |||
47 | (*) Kernel I/O barrier effects. | ||
48 | |||
49 | (*) Assumed minimum execution ordering model. | ||
50 | |||
51 | (*) The effects of the cpu cache. | ||
52 | |||
53 | - Cache coherency. | ||
54 | - Cache coherency vs DMA. | ||
55 | - Cache coherency vs MMIO. | ||
56 | |||
57 | (*) The things CPUs get up to. | ||
58 | |||
59 | - And then there's the Alpha. | ||
60 | |||
61 | (*) References. | ||
62 | |||
63 | |||
64 | ============================ | ||
65 | ABSTRACT MEMORY ACCESS MODEL | ||
66 | ============================ | ||
67 | |||
68 | Consider the following abstract model of the system: | ||
69 | |||
70 | : : | ||
71 | : : | ||
72 | : : | ||
73 | +-------+ : +--------+ : +-------+ | ||
74 | | | : | | : | | | ||
75 | | | : | | : | | | ||
76 | | CPU 1 |<----->| Memory |<----->| CPU 2 | | ||
77 | | | : | | : | | | ||
78 | | | : | | : | | | ||
79 | +-------+ : +--------+ : +-------+ | ||
80 | ^ : ^ : ^ | ||
81 | | : | : | | ||
82 | | : | : | | ||
83 | | : v : | | ||
84 | | : +--------+ : | | ||
85 | | : | | : | | ||
86 | | : | | : | | ||
87 | +---------->| Device |<----------+ | ||
88 | : | | : | ||
89 | : | | : | ||
90 | : +--------+ : | ||
91 | : : | ||
92 | |||
93 | Each CPU executes a program that generates memory access operations. In the | ||
94 | abstract CPU, memory operation ordering is very relaxed, and a CPU may actually | ||
95 | perform the memory operations in any order it likes, provided program causality | ||
96 | appears to be maintained. Similarly, the compiler may also arrange the | ||
97 | instructions it emits in any order it likes, provided it doesn't affect the | ||
98 | apparent operation of the program. | ||
99 | |||
100 | So in the above diagram, the effects of the memory operations performed by a | ||
101 | CPU are perceived by the rest of the system as the operations cross the | ||
102 | interface between the CPU and rest of the system (the dotted lines). | ||
103 | |||
104 | |||
105 | For example, consider the following sequence of events: | ||
106 | |||
107 | CPU 1 CPU 2 | ||
108 | =============== =============== | ||
109 | { A == 1; B == 2 } | ||
110 | A = 3; x = A; | ||
111 | B = 4; y = B; | ||
112 | |||
113 | The set of accesses as seen by the memory system in the middle can be arranged | ||
114 | in 24 different combinations: | ||
115 | |||
116 | STORE A=3, STORE B=4, x=LOAD A->3, y=LOAD B->4 | ||
117 | STORE A=3, STORE B=4, y=LOAD B->4, x=LOAD A->3 | ||
118 | STORE A=3, x=LOAD A->3, STORE B=4, y=LOAD B->4 | ||
119 | STORE A=3, x=LOAD A->3, y=LOAD B->2, STORE B=4 | ||
120 | STORE A=3, y=LOAD B->2, STORE B=4, x=LOAD A->3 | ||
121 | STORE A=3, y=LOAD B->2, x=LOAD A->3, STORE B=4 | ||
122 | STORE B=4, STORE A=3, x=LOAD A->3, y=LOAD B->4 | ||
123 | STORE B=4, ... | ||
124 | ... | ||
125 | |||
126 | and can thus result in four different combinations of values: | ||
127 | |||
128 | x == 1, y == 2 | ||
129 | x == 1, y == 4 | ||
130 | x == 3, y == 2 | ||
131 | x == 3, y == 4 | ||
132 | |||
133 | |||
134 | Furthermore, the stores committed by a CPU to the memory system may not be | ||
135 | perceived by the loads made by another CPU in the same order as the stores were | ||
136 | committed. | ||
137 | |||
138 | |||
139 | As a further example, consider this sequence of events: | ||
140 | |||
141 | CPU 1 CPU 2 | ||
142 | =============== =============== | ||
143 | { A == 1, B == 2, C = 3, P == &A, Q == &C } | ||
144 | B = 4; Q = P; | ||
145 | P = &B D = *Q; | ||
146 | |||
147 | There is an obvious data dependency here, as the value loaded into D depends on | ||
148 | the address retrieved from P by CPU 2. At the end of the sequence, any of the | ||
149 | following results are possible: | ||
150 | |||
151 | (Q == &A) and (D == 1) | ||
152 | (Q == &B) and (D == 2) | ||
153 | (Q == &B) and (D == 4) | ||
154 | |||
155 | Note that CPU 2 will never try and load C into D because the CPU will load P | ||
156 | into Q before issuing the load of *Q. | ||
157 | |||
158 | |||
159 | DEVICE OPERATIONS | ||
160 | ----------------- | ||
161 | |||
162 | Some devices present their control interfaces as collections of memory | ||
163 | locations, but the order in which the control registers are accessed is very | ||
164 | important. For instance, imagine an ethernet card with a set of internal | ||
165 | registers that are accessed through an address port register (A) and a data | ||
166 | port register (D). To read internal register 5, the following code might then | ||
167 | be used: | ||
168 | |||
169 | *A = 5; | ||
170 | x = *D; | ||
171 | |||
172 | but this might show up as either of the following two sequences: | ||
173 | |||
174 | STORE *A = 5, x = LOAD *D | ||
175 | x = LOAD *D, STORE *A = 5 | ||
176 | |||
177 | the second of which will almost certainly result in a malfunction, since it set | ||
178 | the address _after_ attempting to read the register. | ||
179 | |||
180 | |||
181 | GUARANTEES | ||
182 | ---------- | ||
183 | |||
184 | There are some minimal guarantees that may be expected of a CPU: | ||
185 | |||
186 | (*) On any given CPU, dependent memory accesses will be issued in order, with | ||
187 | respect to itself. This means that for: | ||
188 | |||
189 | Q = P; D = *Q; | ||
190 | |||
191 | the CPU will issue the following memory operations: | ||
192 | |||
193 | Q = LOAD P, D = LOAD *Q | ||
194 | |||
195 | and always in that order. | ||
196 | |||
197 | (*) Overlapping loads and stores within a particular CPU will appear to be | ||
198 | ordered within that CPU. This means that for: | ||
199 | |||
200 | a = *X; *X = b; | ||
201 | |||
202 | the CPU will only issue the following sequence of memory operations: | ||
203 | |||
204 | a = LOAD *X, STORE *X = b | ||
205 | |||
206 | And for: | ||
207 | |||
208 | *X = c; d = *X; | ||
209 | |||
210 | the CPU will only issue: | ||
211 | |||
212 | STORE *X = c, d = LOAD *X | ||
213 | |||
214 | (Loads and stores overlap if they are targetted at overlapping pieces of | ||
215 | memory). | ||
216 | |||
217 | And there are a number of things that _must_ or _must_not_ be assumed: | ||
218 | |||
219 | (*) It _must_not_ be assumed that independent loads and stores will be issued | ||
220 | in the order given. This means that for: | ||
221 | |||
222 | X = *A; Y = *B; *D = Z; | ||
223 | |||
224 | we may get any of the following sequences: | ||
225 | |||
226 | X = LOAD *A, Y = LOAD *B, STORE *D = Z | ||
227 | X = LOAD *A, STORE *D = Z, Y = LOAD *B | ||
228 | Y = LOAD *B, X = LOAD *A, STORE *D = Z | ||
229 | Y = LOAD *B, STORE *D = Z, X = LOAD *A | ||
230 | STORE *D = Z, X = LOAD *A, Y = LOAD *B | ||
231 | STORE *D = Z, Y = LOAD *B, X = LOAD *A | ||
232 | |||
233 | (*) It _must_ be assumed that overlapping memory accesses may be merged or | ||
234 | discarded. This means that for: | ||
235 | |||
236 | X = *A; Y = *(A + 4); | ||
237 | |||
238 | we may get any one of the following sequences: | ||
239 | |||
240 | X = LOAD *A; Y = LOAD *(A + 4); | ||
241 | Y = LOAD *(A + 4); X = LOAD *A; | ||
242 | {X, Y} = LOAD {*A, *(A + 4) }; | ||
243 | |||
244 | And for: | ||
245 | |||
246 | *A = X; Y = *A; | ||
247 | |||
248 | we may get either of: | ||
249 | |||
250 | STORE *A = X; Y = LOAD *A; | ||
251 | STORE *A = Y; | ||
252 | |||
253 | |||
254 | ========================= | ||
255 | WHAT ARE MEMORY BARRIERS? | ||
256 | ========================= | ||
257 | |||
258 | As can be seen above, independent memory operations are effectively performed | ||
259 | in random order, but this can be a problem for CPU-CPU interaction and for I/O. | ||
260 | What is required is some way of intervening to instruct the compiler and the | ||
261 | CPU to restrict the order. | ||
262 | |||
263 | Memory barriers are such interventions. They impose a perceived partial | ||
264 | ordering between the memory operations specified on either side of the barrier. | ||
265 | They request that the sequence of memory events generated appears to other | ||
266 | parts of the system as if the barrier is effective on that CPU. | ||
267 | |||
268 | |||
269 | VARIETIES OF MEMORY BARRIER | ||
270 | --------------------------- | ||
271 | |||
272 | Memory barriers come in four basic varieties: | ||
273 | |||
274 | (1) Write (or store) memory barriers. | ||
275 | |||
276 | A write memory barrier gives a guarantee that all the STORE operations | ||
277 | specified before the barrier will appear to happen before all the STORE | ||
278 | operations specified after the barrier with respect to the other | ||
279 | components of the system. | ||
280 | |||
281 | A write barrier is a partial ordering on stores only; it is not required | ||
282 | to have any effect on loads. | ||
283 | |||
284 | A CPU can be viewed as as commiting a sequence of store operations to the | ||
285 | memory system as time progresses. All stores before a write barrier will | ||
286 | occur in the sequence _before_ all the stores after the write barrier. | ||
287 | |||
288 | [!] Note that write barriers should normally be paired with read or data | ||
289 | dependency barriers; see the "SMP barrier pairing" subsection. | ||
290 | |||
291 | |||
292 | (2) Data dependency barriers. | ||
293 | |||
294 | A data dependency barrier is a weaker form of read barrier. In the case | ||
295 | where two loads are performed such that the second depends on the result | ||
296 | of the first (eg: the first load retrieves the address to which the second | ||
297 | load will be directed), a data dependency barrier would be required to | ||
298 | make sure that the target of the second load is updated before the address | ||
299 | obtained by the first load is accessed. | ||
300 | |||
301 | A data dependency barrier is a partial ordering on interdependent loads | ||
302 | only; it is not required to have any effect on stores, independent loads | ||
303 | or overlapping loads. | ||
304 | |||
305 | As mentioned in (1), the other CPUs in the system can be viewed as | ||
306 | committing sequences of stores to the memory system that the CPU being | ||
307 | considered can then perceive. A data dependency barrier issued by the CPU | ||
308 | under consideration guarantees that for any load preceding it, if that | ||
309 | load touches one of a sequence of stores from another CPU, then by the | ||
310 | time the barrier completes, the effects of all the stores prior to that | ||
311 | touched by the load will be perceptible to any loads issued after the data | ||
312 | dependency barrier. | ||
313 | |||
314 | See the "Examples of memory barrier sequences" subsection for diagrams | ||
315 | showing the ordering constraints. | ||
316 | |||
317 | [!] Note that the first load really has to have a _data_ dependency and | ||
318 | not a control dependency. If the address for the second load is dependent | ||
319 | on the first load, but the dependency is through a conditional rather than | ||
320 | actually loading the address itself, then it's a _control_ dependency and | ||
321 | a full read barrier or better is required. See the "Control dependencies" | ||
322 | subsection for more information. | ||
323 | |||
324 | [!] Note that data dependency barriers should normally be paired with | ||
325 | write barriers; see the "SMP barrier pairing" subsection. | ||
326 | |||
327 | |||
328 | (3) Read (or load) memory barriers. | ||
329 | |||
330 | A read barrier is a data dependency barrier plus a guarantee that all the | ||
331 | LOAD operations specified before the barrier will appear to happen before | ||
332 | all the LOAD operations specified after the barrier with respect to the | ||
333 | other components of the system. | ||
334 | |||
335 | A read barrier is a partial ordering on loads only; it is not required to | ||
336 | have any effect on stores. | ||
337 | |||
338 | Read memory barriers imply data dependency barriers, and so can substitute | ||
339 | for them. | ||
340 | |||
341 | [!] Note that read barriers should normally be paired with write barriers; | ||
342 | see the "SMP barrier pairing" subsection. | ||
343 | |||
344 | |||
345 | (4) General memory barriers. | ||
346 | |||
347 | A general memory barrier is a combination of both a read memory barrier | ||
348 | and a write memory barrier. It is a partial ordering over both loads and | ||
349 | stores. | ||
350 | |||
351 | General memory barriers imply both read and write memory barriers, and so | ||
352 | can substitute for either. | ||
353 | |||
354 | |||
355 | And a couple of implicit varieties: | ||
356 | |||
357 | (5) LOCK operations. | ||
358 | |||
359 | This acts as a one-way permeable barrier. It guarantees that all memory | ||
360 | operations after the LOCK operation will appear to happen after the LOCK | ||
361 | operation with respect to the other components of the system. | ||
362 | |||
363 | Memory operations that occur before a LOCK operation may appear to happen | ||
364 | after it completes. | ||
365 | |||
366 | A LOCK operation should almost always be paired with an UNLOCK operation. | ||
367 | |||
368 | |||
369 | (6) UNLOCK operations. | ||
370 | |||
371 | This also acts as a one-way permeable barrier. It guarantees that all | ||
372 | memory operations before the UNLOCK operation will appear to happen before | ||
373 | the UNLOCK operation with respect to the other components of the system. | ||
374 | |||
375 | Memory operations that occur after an UNLOCK operation may appear to | ||
376 | happen before it completes. | ||
377 | |||
378 | LOCK and UNLOCK operations are guaranteed to appear with respect to each | ||
379 | other strictly in the order specified. | ||
380 | |||
381 | The use of LOCK and UNLOCK operations generally precludes the need for | ||
382 | other sorts of memory barrier (but note the exceptions mentioned in the | ||
383 | subsection "MMIO write barrier"). | ||
384 | |||
385 | |||
386 | Memory barriers are only required where there's a possibility of interaction | ||
387 | between two CPUs or between a CPU and a device. If it can be guaranteed that | ||
388 | there won't be any such interaction in any particular piece of code, then | ||
389 | memory barriers are unnecessary in that piece of code. | ||
390 | |||
391 | |||
392 | Note that these are the _minimum_ guarantees. Different architectures may give | ||
393 | more substantial guarantees, but they may _not_ be relied upon outside of arch | ||
394 | specific code. | ||
395 | |||
396 | |||
397 | WHAT MAY NOT BE ASSUMED ABOUT MEMORY BARRIERS? | ||
398 | ---------------------------------------------- | ||
399 | |||
400 | There are certain things that the Linux kernel memory barriers do not guarantee: | ||
401 | |||
402 | (*) There is no guarantee that any of the memory accesses specified before a | ||
403 | memory barrier will be _complete_ by the completion of a memory barrier | ||
404 | instruction; the barrier can be considered to draw a line in that CPU's | ||
405 | access queue that accesses of the appropriate type may not cross. | ||
406 | |||
407 | (*) There is no guarantee that issuing a memory barrier on one CPU will have | ||
408 | any direct effect on another CPU or any other hardware in the system. The | ||
409 | indirect effect will be the order in which the second CPU sees the effects | ||
410 | of the first CPU's accesses occur, but see the next point: | ||
411 | |||
412 | (*) There is no guarantee that the a CPU will see the correct order of effects | ||
413 | from a second CPU's accesses, even _if_ the second CPU uses a memory | ||
414 | barrier, unless the first CPU _also_ uses a matching memory barrier (see | ||
415 | the subsection on "SMP Barrier Pairing"). | ||
416 | |||
417 | (*) There is no guarantee that some intervening piece of off-the-CPU | ||
418 | hardware[*] will not reorder the memory accesses. CPU cache coherency | ||
419 | mechanisms should propagate the indirect effects of a memory barrier | ||
420 | between CPUs, but might not do so in order. | ||
421 | |||
422 | [*] For information on bus mastering DMA and coherency please read: | ||
423 | |||
424 | Documentation/pci.txt | ||
425 | Documentation/DMA-mapping.txt | ||
426 | Documentation/DMA-API.txt | ||
427 | |||
428 | |||
429 | DATA DEPENDENCY BARRIERS | ||
430 | ------------------------ | ||
431 | |||
432 | The usage requirements of data dependency barriers are a little subtle, and | ||
433 | it's not always obvious that they're needed. To illustrate, consider the | ||
434 | following sequence of events: | ||
435 | |||
436 | CPU 1 CPU 2 | ||
437 | =============== =============== | ||
438 | { A == 1, B == 2, C = 3, P == &A, Q == &C } | ||
439 | B = 4; | ||
440 | <write barrier> | ||
441 | P = &B | ||
442 | Q = P; | ||
443 | D = *Q; | ||
444 | |||
445 | There's a clear data dependency here, and it would seem that by the end of the | ||
446 | sequence, Q must be either &A or &B, and that: | ||
447 | |||
448 | (Q == &A) implies (D == 1) | ||
449 | (Q == &B) implies (D == 4) | ||
450 | |||
451 | But! CPU 2's perception of P may be updated _before_ its perception of B, thus | ||
452 | leading to the following situation: | ||
453 | |||
454 | (Q == &B) and (D == 2) ???? | ||
455 | |||
456 | Whilst this may seem like a failure of coherency or causality maintenance, it | ||
457 | isn't, and this behaviour can be observed on certain real CPUs (such as the DEC | ||
458 | Alpha). | ||
459 | |||
460 | To deal with this, a data dependency barrier must be inserted between the | ||
461 | address load and the data load: | ||
462 | |||
463 | CPU 1 CPU 2 | ||
464 | =============== =============== | ||
465 | { A == 1, B == 2, C = 3, P == &A, Q == &C } | ||
466 | B = 4; | ||
467 | <write barrier> | ||
468 | P = &B | ||
469 | Q = P; | ||
470 | <data dependency barrier> | ||
471 | D = *Q; | ||
472 | |||
473 | This enforces the occurrence of one of the two implications, and prevents the | ||
474 | third possibility from arising. | ||
475 | |||
476 | [!] Note that this extremely counterintuitive situation arises most easily on | ||
477 | machines with split caches, so that, for example, one cache bank processes | ||
478 | even-numbered cache lines and the other bank processes odd-numbered cache | ||
479 | lines. The pointer P might be stored in an odd-numbered cache line, and the | ||
480 | variable B might be stored in an even-numbered cache line. Then, if the | ||
481 | even-numbered bank of the reading CPU's cache is extremely busy while the | ||
482 | odd-numbered bank is idle, one can see the new value of the pointer P (&B), | ||
483 | but the old value of the variable B (1). | ||
484 | |||
485 | |||
486 | Another example of where data dependency barriers might by required is where a | ||
487 | number is read from memory and then used to calculate the index for an array | ||
488 | access: | ||
489 | |||
490 | CPU 1 CPU 2 | ||
491 | =============== =============== | ||
492 | { M[0] == 1, M[1] == 2, M[3] = 3, P == 0, Q == 3 } | ||
493 | M[1] = 4; | ||
494 | <write barrier> | ||
495 | P = 1 | ||
496 | Q = P; | ||
497 | <data dependency barrier> | ||
498 | D = M[Q]; | ||
499 | |||
500 | |||
501 | The data dependency barrier is very important to the RCU system, for example. | ||
502 | See rcu_dereference() in include/linux/rcupdate.h. This permits the current | ||
503 | target of an RCU'd pointer to be replaced with a new modified target, without | ||
504 | the replacement target appearing to be incompletely initialised. | ||
505 | |||
506 | See also the subsection on "Cache Coherency" for a more thorough example. | ||
507 | |||
508 | |||
509 | CONTROL DEPENDENCIES | ||
510 | -------------------- | ||
511 | |||
512 | A control dependency requires a full read memory barrier, not simply a data | ||
513 | dependency barrier to make it work correctly. Consider the following bit of | ||
514 | code: | ||
515 | |||
516 | q = &a; | ||
517 | if (p) | ||
518 | q = &b; | ||
519 | <data dependency barrier> | ||
520 | x = *q; | ||
521 | |||
522 | This will not have the desired effect because there is no actual data | ||
523 | dependency, but rather a control dependency that the CPU may short-circuit by | ||
524 | attempting to predict the outcome in advance. In such a case what's actually | ||
525 | required is: | ||
526 | |||
527 | q = &a; | ||
528 | if (p) | ||
529 | q = &b; | ||
530 | <read barrier> | ||
531 | x = *q; | ||
532 | |||
533 | |||
534 | SMP BARRIER PAIRING | ||
535 | ------------------- | ||
536 | |||
537 | When dealing with CPU-CPU interactions, certain types of memory barrier should | ||
538 | always be paired. A lack of appropriate pairing is almost certainly an error. | ||
539 | |||
540 | A write barrier should always be paired with a data dependency barrier or read | ||
541 | barrier, though a general barrier would also be viable. Similarly a read | ||
542 | barrier or a data dependency barrier should always be paired with at least an | ||
543 | write barrier, though, again, a general barrier is viable: | ||
544 | |||
545 | CPU 1 CPU 2 | ||
546 | =============== =============== | ||
547 | a = 1; | ||
548 | <write barrier> | ||
549 | b = 2; x = a; | ||
550 | <read barrier> | ||
551 | y = b; | ||
552 | |||
553 | Or: | ||
554 | |||
555 | CPU 1 CPU 2 | ||
556 | =============== =============================== | ||
557 | a = 1; | ||
558 | <write barrier> | ||
559 | b = &a; x = b; | ||
560 | <data dependency barrier> | ||
561 | y = *x; | ||
562 | |||
563 | Basically, the read barrier always has to be there, even though it can be of | ||
564 | the "weaker" type. | ||
565 | |||
566 | |||
567 | EXAMPLES OF MEMORY BARRIER SEQUENCES | ||
568 | ------------------------------------ | ||
569 | |||
570 | Firstly, write barriers act as a partial orderings on store operations. | ||
571 | Consider the following sequence of events: | ||
572 | |||
573 | CPU 1 | ||
574 | ======================= | ||
575 | STORE A = 1 | ||
576 | STORE B = 2 | ||
577 | STORE C = 3 | ||
578 | <write barrier> | ||
579 | STORE D = 4 | ||
580 | STORE E = 5 | ||
581 | |||
582 | This sequence of events is committed to the memory coherence system in an order | ||
583 | that the rest of the system might perceive as the unordered set of { STORE A, | ||
584 | STORE B, STORE C } all occuring before the unordered set of { STORE D, STORE E | ||
585 | }: | ||
586 | |||
587 | +-------+ : : | ||
588 | | | +------+ | ||
589 | | |------>| C=3 | } /\ | ||
590 | | | : +------+ }----- \ -----> Events perceptible | ||
591 | | | : | A=1 | } \/ to rest of system | ||
592 | | | : +------+ } | ||
593 | | CPU 1 | : | B=2 | } | ||
594 | | | +------+ } | ||
595 | | | wwwwwwwwwwwwwwww } <--- At this point the write barrier | ||
596 | | | +------+ } requires all stores prior to the | ||
597 | | | : | E=5 | } barrier to be committed before | ||
598 | | | : +------+ } further stores may be take place. | ||
599 | | |------>| D=4 | } | ||
600 | | | +------+ | ||
601 | +-------+ : : | ||
602 | | | ||
603 | | Sequence in which stores committed to memory system | ||
604 | | by CPU 1 | ||
605 | V | ||
606 | |||
607 | |||
608 | Secondly, data dependency barriers act as a partial orderings on data-dependent | ||
609 | loads. Consider the following sequence of events: | ||
610 | |||
611 | CPU 1 CPU 2 | ||
612 | ======================= ======================= | ||
613 | { B = 7; X = 9; Y = 8; C = &Y } | ||
614 | STORE A = 1 | ||
615 | STORE B = 2 | ||
616 | <write barrier> | ||
617 | STORE C = &B LOAD X | ||
618 | STORE D = 4 LOAD C (gets &B) | ||
619 | LOAD *C (reads B) | ||
620 | |||
621 | Without intervention, CPU 2 may perceive the events on CPU 1 in some | ||
622 | effectively random order, despite the write barrier issued by CPU 1: | ||
623 | |||
624 | +-------+ : : : : | ||
625 | | | +------+ +-------+ | Sequence of update | ||
626 | | |------>| B=2 |----- --->| Y->8 | | of perception on | ||
627 | | | : +------+ \ +-------+ | CPU 2 | ||
628 | | CPU 1 | : | A=1 | \ --->| C->&Y | V | ||
629 | | | +------+ | +-------+ | ||
630 | | | wwwwwwwwwwwwwwww | : : | ||
631 | | | +------+ | : : | ||
632 | | | : | C=&B |--- | : : +-------+ | ||
633 | | | : +------+ \ | +-------+ | | | ||
634 | | |------>| D=4 | ----------->| C->&B |------>| | | ||
635 | | | +------+ | +-------+ | | | ||
636 | +-------+ : : | : : | | | ||
637 | | : : | | | ||
638 | | : : | CPU 2 | | ||
639 | | +-------+ | | | ||
640 | Apparently incorrect ---> | | B->7 |------>| | | ||
641 | perception of B (!) | +-------+ | | | ||
642 | | : : | | | ||
643 | | +-------+ | | | ||
644 | The load of X holds ---> \ | X->9 |------>| | | ||
645 | up the maintenance \ +-------+ | | | ||
646 | of coherence of B ----->| B->2 | +-------+ | ||
647 | +-------+ | ||
648 | : : | ||
649 | |||
650 | |||
651 | In the above example, CPU 2 perceives that B is 7, despite the load of *C | ||
652 | (which would be B) coming after the the LOAD of C. | ||
653 | |||
654 | If, however, a data dependency barrier were to be placed between the load of C | ||
655 | and the load of *C (ie: B) on CPU 2: | ||
656 | |||
657 | CPU 1 CPU 2 | ||
658 | ======================= ======================= | ||
659 | { B = 7; X = 9; Y = 8; C = &Y } | ||
660 | STORE A = 1 | ||
661 | STORE B = 2 | ||
662 | <write barrier> | ||
663 | STORE C = &B LOAD X | ||
664 | STORE D = 4 LOAD C (gets &B) | ||
665 | <data dependency barrier> | ||
666 | LOAD *C (reads B) | ||
667 | |||
668 | then the following will occur: | ||
669 | |||
670 | +-------+ : : : : | ||
671 | | | +------+ +-------+ | ||
672 | | |------>| B=2 |----- --->| Y->8 | | ||
673 | | | : +------+ \ +-------+ | ||
674 | | CPU 1 | : | A=1 | \ --->| C->&Y | | ||
675 | | | +------+ | +-------+ | ||
676 | | | wwwwwwwwwwwwwwww | : : | ||
677 | | | +------+ | : : | ||
678 | | | : | C=&B |--- | : : +-------+ | ||
679 | | | : +------+ \ | +-------+ | | | ||
680 | | |------>| D=4 | ----------->| C->&B |------>| | | ||
681 | | | +------+ | +-------+ | | | ||
682 | +-------+ : : | : : | | | ||
683 | | : : | | | ||
684 | | : : | CPU 2 | | ||
685 | | +-------+ | | | ||
686 | \ | X->9 |------>| | | ||
687 | \ +-------+ | | | ||
688 | ----->| B->2 | | | | ||
689 | +-------+ | | | ||
690 | Makes sure all effects ---> ddddddddddddddddd | | | ||
691 | prior to the store of C +-------+ | | | ||
692 | are perceptible to | B->2 |------>| | | ||
693 | successive loads +-------+ | | | ||
694 | : : +-------+ | ||
695 | |||
696 | |||
697 | And thirdly, a read barrier acts as a partial order on loads. Consider the | ||
698 | following sequence of events: | ||
699 | |||
700 | CPU 1 CPU 2 | ||
701 | ======================= ======================= | ||
702 | STORE A=1 | ||
703 | STORE B=2 | ||
704 | STORE C=3 | ||
705 | <write barrier> | ||
706 | STORE D=4 | ||
707 | STORE E=5 | ||
708 | LOAD A | ||
709 | LOAD B | ||
710 | LOAD C | ||
711 | LOAD D | ||
712 | LOAD E | ||
713 | |||
714 | Without intervention, CPU 2 may then choose to perceive the events on CPU 1 in | ||
715 | some effectively random order, despite the write barrier issued by CPU 1: | ||
716 | |||
717 | +-------+ : : | ||
718 | | | +------+ | ||
719 | | |------>| C=3 | } | ||
720 | | | : +------+ } | ||
721 | | | : | A=1 | } | ||
722 | | | : +------+ } | ||
723 | | CPU 1 | : | B=2 | }--- | ||
724 | | | +------+ } \ | ||
725 | | | wwwwwwwwwwwww} \ | ||
726 | | | +------+ } \ : : +-------+ | ||
727 | | | : | E=5 | } \ +-------+ | | | ||
728 | | | : +------+ } \ { | C->3 |------>| | | ||
729 | | |------>| D=4 | } \ { +-------+ : | | | ||
730 | | | +------+ \ { | E->5 | : | | | ||
731 | +-------+ : : \ { +-------+ : | | | ||
732 | Transfer -->{ | A->1 | : | CPU 2 | | ||
733 | from CPU 1 { +-------+ : | | | ||
734 | to CPU 2 { | D->4 | : | | | ||
735 | { +-------+ : | | | ||
736 | { | B->2 |------>| | | ||
737 | +-------+ | | | ||
738 | : : +-------+ | ||
739 | |||
740 | |||
741 | If, however, a read barrier were to be placed between the load of C and the | ||
742 | load of D on CPU 2, then the partial ordering imposed by CPU 1 will be | ||
743 | perceived correctly by CPU 2. | ||
744 | |||
745 | +-------+ : : | ||
746 | | | +------+ | ||
747 | | |------>| C=3 | } | ||
748 | | | : +------+ } | ||
749 | | | : | A=1 | }--- | ||
750 | | | : +------+ } \ | ||
751 | | CPU 1 | : | B=2 | } \ | ||
752 | | | +------+ \ | ||
753 | | | wwwwwwwwwwwwwwww \ | ||
754 | | | +------+ \ : : +-------+ | ||
755 | | | : | E=5 | } \ +-------+ | | | ||
756 | | | : +------+ }--- \ { | C->3 |------>| | | ||
757 | | |------>| D=4 | } \ \ { +-------+ : | | | ||
758 | | | +------+ \ -->{ | B->2 | : | | | ||
759 | +-------+ : : \ { +-------+ : | | | ||
760 | \ { | A->1 | : | CPU 2 | | ||
761 | \ +-------+ | | | ||
762 | At this point the read ----> \ rrrrrrrrrrrrrrrrr | | | ||
763 | barrier causes all effects \ +-------+ | | | ||
764 | prior to the storage of C \ { | E->5 | : | | | ||
765 | to be perceptible to CPU 2 -->{ +-------+ : | | | ||
766 | { | D->4 |------>| | | ||
767 | +-------+ | | | ||
768 | : : +-------+ | ||
769 | |||
770 | |||
771 | ======================== | ||
772 | EXPLICIT KERNEL BARRIERS | ||
773 | ======================== | ||
774 | |||
775 | The Linux kernel has a variety of different barriers that act at different | ||
776 | levels: | ||
777 | |||
778 | (*) Compiler barrier. | ||
779 | |||
780 | (*) CPU memory barriers. | ||
781 | |||
782 | (*) MMIO write barrier. | ||
783 | |||
784 | |||
785 | COMPILER BARRIER | ||
786 | ---------------- | ||
787 | |||
788 | The Linux kernel has an explicit compiler barrier function that prevents the | ||
789 | compiler from moving the memory accesses either side of it to the other side: | ||
790 | |||
791 | barrier(); | ||
792 | |||
793 | This a general barrier - lesser varieties of compiler barrier do not exist. | ||
794 | |||
795 | The compiler barrier has no direct effect on the CPU, which may then reorder | ||
796 | things however it wishes. | ||
797 | |||
798 | |||
799 | CPU MEMORY BARRIERS | ||
800 | ------------------- | ||
801 | |||
802 | The Linux kernel has eight basic CPU memory barriers: | ||
803 | |||
804 | TYPE MANDATORY SMP CONDITIONAL | ||
805 | =============== ======================= =========================== | ||
806 | GENERAL mb() smp_mb() | ||
807 | WRITE wmb() smp_wmb() | ||
808 | READ rmb() smp_rmb() | ||
809 | DATA DEPENDENCY read_barrier_depends() smp_read_barrier_depends() | ||
810 | |||
811 | |||
812 | All CPU memory barriers unconditionally imply compiler barriers. | ||
813 | |||
814 | SMP memory barriers are reduced to compiler barriers on uniprocessor compiled | ||
815 | systems because it is assumed that a CPU will be appear to be self-consistent, | ||
816 | and will order overlapping accesses correctly with respect to itself. | ||
817 | |||
818 | [!] Note that SMP memory barriers _must_ be used to control the ordering of | ||
819 | references to shared memory on SMP systems, though the use of locking instead | ||
820 | is sufficient. | ||
821 | |||
822 | Mandatory barriers should not be used to control SMP effects, since mandatory | ||
823 | barriers unnecessarily impose overhead on UP systems. They may, however, be | ||
824 | used to control MMIO effects on accesses through relaxed memory I/O windows. | ||
825 | These are required even on non-SMP systems as they affect the order in which | ||
826 | memory operations appear to a device by prohibiting both the compiler and the | ||
827 | CPU from reordering them. | ||
828 | |||
829 | |||
830 | There are some more advanced barrier functions: | ||
831 | |||
832 | (*) set_mb(var, value) | ||
833 | (*) set_wmb(var, value) | ||
834 | |||
835 | These assign the value to the variable and then insert at least a write | ||
836 | barrier after it, depending on the function. They aren't guaranteed to | ||
837 | insert anything more than a compiler barrier in a UP compilation. | ||
838 | |||
839 | |||
840 | (*) smp_mb__before_atomic_dec(); | ||
841 | (*) smp_mb__after_atomic_dec(); | ||
842 | (*) smp_mb__before_atomic_inc(); | ||
843 | (*) smp_mb__after_atomic_inc(); | ||
844 | |||
845 | These are for use with atomic add, subtract, increment and decrement | ||
846 | functions that don't return a value, especially when used for reference | ||
847 | counting. These functions do not imply memory barriers. | ||
848 | |||
849 | As an example, consider a piece of code that marks an object as being dead | ||
850 | and then decrements the object's reference count: | ||
851 | |||
852 | obj->dead = 1; | ||
853 | smp_mb__before_atomic_dec(); | ||
854 | atomic_dec(&obj->ref_count); | ||
855 | |||
856 | This makes sure that the death mark on the object is perceived to be set | ||
857 | *before* the reference counter is decremented. | ||
858 | |||
859 | See Documentation/atomic_ops.txt for more information. See the "Atomic | ||
860 | operations" subsection for information on where to use these. | ||
861 | |||
862 | |||
863 | (*) smp_mb__before_clear_bit(void); | ||
864 | (*) smp_mb__after_clear_bit(void); | ||
865 | |||
866 | These are for use similar to the atomic inc/dec barriers. These are | ||
867 | typically used for bitwise unlocking operations, so care must be taken as | ||
868 | there are no implicit memory barriers here either. | ||
869 | |||
870 | Consider implementing an unlock operation of some nature by clearing a | ||
871 | locking bit. The clear_bit() would then need to be barriered like this: | ||
872 | |||
873 | smp_mb__before_clear_bit(); | ||
874 | clear_bit( ... ); | ||
875 | |||
876 | This prevents memory operations before the clear leaking to after it. See | ||
877 | the subsection on "Locking Functions" with reference to UNLOCK operation | ||
878 | implications. | ||
879 | |||
880 | See Documentation/atomic_ops.txt for more information. See the "Atomic | ||
881 | operations" subsection for information on where to use these. | ||
882 | |||
883 | |||
884 | MMIO WRITE BARRIER | ||
885 | ------------------ | ||
886 | |||
887 | The Linux kernel also has a special barrier for use with memory-mapped I/O | ||
888 | writes: | ||
889 | |||
890 | mmiowb(); | ||
891 | |||
892 | This is a variation on the mandatory write barrier that causes writes to weakly | ||
893 | ordered I/O regions to be partially ordered. Its effects may go beyond the | ||
894 | CPU->Hardware interface and actually affect the hardware at some level. | ||
895 | |||
896 | See the subsection "Locks vs I/O accesses" for more information. | ||
897 | |||
898 | |||
899 | =============================== | ||
900 | IMPLICIT KERNEL MEMORY BARRIERS | ||
901 | =============================== | ||
902 | |||
903 | Some of the other functions in the linux kernel imply memory barriers, amongst | ||
904 | which are locking, scheduling and memory allocation functions. | ||
905 | |||
906 | This specification is a _minimum_ guarantee; any particular architecture may | ||
907 | provide more substantial guarantees, but these may not be relied upon outside | ||
908 | of arch specific code. | ||
909 | |||
910 | |||
911 | LOCKING FUNCTIONS | ||
912 | ----------------- | ||
913 | |||
914 | The Linux kernel has a number of locking constructs: | ||
915 | |||
916 | (*) spin locks | ||
917 | (*) R/W spin locks | ||
918 | (*) mutexes | ||
919 | (*) semaphores | ||
920 | (*) R/W semaphores | ||
921 | (*) RCU | ||
922 | |||
923 | In all cases there are variants on "LOCK" operations and "UNLOCK" operations | ||
924 | for each construct. These operations all imply certain barriers: | ||
925 | |||
926 | (1) LOCK operation implication: | ||
927 | |||
928 | Memory operations issued after the LOCK will be completed after the LOCK | ||
929 | operation has completed. | ||
930 | |||
931 | Memory operations issued before the LOCK may be completed after the LOCK | ||
932 | operation has completed. | ||
933 | |||
934 | (2) UNLOCK operation implication: | ||
935 | |||
936 | Memory operations issued before the UNLOCK will be completed before the | ||
937 | UNLOCK operation has completed. | ||
938 | |||
939 | Memory operations issued after the UNLOCK may be completed before the | ||
940 | UNLOCK operation has completed. | ||
941 | |||
942 | (3) LOCK vs LOCK implication: | ||
943 | |||
944 | All LOCK operations issued before another LOCK operation will be completed | ||
945 | before that LOCK operation. | ||
946 | |||
947 | (4) LOCK vs UNLOCK implication: | ||
948 | |||
949 | All LOCK operations issued before an UNLOCK operation will be completed | ||
950 | before the UNLOCK operation. | ||
951 | |||
952 | All UNLOCK operations issued before a LOCK operation will be completed | ||
953 | before the LOCK operation. | ||
954 | |||
955 | (5) Failed conditional LOCK implication: | ||
956 | |||
957 | Certain variants of the LOCK operation may fail, either due to being | ||
958 | unable to get the lock immediately, or due to receiving an unblocked | ||
959 | signal whilst asleep waiting for the lock to become available. Failed | ||
960 | locks do not imply any sort of barrier. | ||
961 | |||
962 | Therefore, from (1), (2) and (4) an UNLOCK followed by an unconditional LOCK is | ||
963 | equivalent to a full barrier, but a LOCK followed by an UNLOCK is not. | ||
964 | |||
965 | [!] Note: one of the consequence of LOCKs and UNLOCKs being only one-way | ||
966 | barriers is that the effects instructions outside of a critical section may | ||
967 | seep into the inside of the critical section. | ||
968 | |||
969 | Locks and semaphores may not provide any guarantee of ordering on UP compiled | ||
970 | systems, and so cannot be counted on in such a situation to actually achieve | ||
971 | anything at all - especially with respect to I/O accesses - unless combined | ||
972 | with interrupt disabling operations. | ||
973 | |||
974 | See also the section on "Inter-CPU locking barrier effects". | ||
975 | |||
976 | |||
977 | As an example, consider the following: | ||
978 | |||
979 | *A = a; | ||
980 | *B = b; | ||
981 | LOCK | ||
982 | *C = c; | ||
983 | *D = d; | ||
984 | UNLOCK | ||
985 | *E = e; | ||
986 | *F = f; | ||
987 | |||
988 | The following sequence of events is acceptable: | ||
989 | |||
990 | LOCK, {*F,*A}, *E, {*C,*D}, *B, UNLOCK | ||
991 | |||
992 | [+] Note that {*F,*A} indicates a combined access. | ||
993 | |||
994 | But none of the following are: | ||
995 | |||
996 | {*F,*A}, *B, LOCK, *C, *D, UNLOCK, *E | ||
997 | *A, *B, *C, LOCK, *D, UNLOCK, *E, *F | ||
998 | *A, *B, LOCK, *C, UNLOCK, *D, *E, *F | ||
999 | *B, LOCK, *C, *D, UNLOCK, {*F,*A}, *E | ||
1000 | |||
1001 | |||
1002 | |||
1003 | INTERRUPT DISABLING FUNCTIONS | ||
1004 | ----------------------------- | ||
1005 | |||
1006 | Functions that disable interrupts (LOCK equivalent) and enable interrupts | ||
1007 | (UNLOCK equivalent) will act as compiler barriers only. So if memory or I/O | ||
1008 | barriers are required in such a situation, they must be provided from some | ||
1009 | other means. | ||
1010 | |||
1011 | |||
1012 | MISCELLANEOUS FUNCTIONS | ||
1013 | ----------------------- | ||
1014 | |||
1015 | Other functions that imply barriers: | ||
1016 | |||
1017 | (*) schedule() and similar imply full memory barriers. | ||
1018 | |||
1019 | (*) Memory allocation and release functions imply full memory barriers. | ||
1020 | |||
1021 | |||
1022 | ================================= | ||
1023 | INTER-CPU LOCKING BARRIER EFFECTS | ||
1024 | ================================= | ||
1025 | |||
1026 | On SMP systems locking primitives give a more substantial form of barrier: one | ||
1027 | that does affect memory access ordering on other CPUs, within the context of | ||
1028 | conflict on any particular lock. | ||
1029 | |||
1030 | |||
1031 | LOCKS VS MEMORY ACCESSES | ||
1032 | ------------------------ | ||
1033 | |||
1034 | Consider the following: the system has a pair of spinlocks (N) and (Q), and | ||
1035 | three CPUs; then should the following sequence of events occur: | ||
1036 | |||
1037 | CPU 1 CPU 2 | ||
1038 | =============================== =============================== | ||
1039 | *A = a; *E = e; | ||
1040 | LOCK M LOCK Q | ||
1041 | *B = b; *F = f; | ||
1042 | *C = c; *G = g; | ||
1043 | UNLOCK M UNLOCK Q | ||
1044 | *D = d; *H = h; | ||
1045 | |||
1046 | Then there is no guarantee as to what order CPU #3 will see the accesses to *A | ||
1047 | through *H occur in, other than the constraints imposed by the separate locks | ||
1048 | on the separate CPUs. It might, for example, see: | ||
1049 | |||
1050 | *E, LOCK M, LOCK Q, *G, *C, *F, *A, *B, UNLOCK Q, *D, *H, UNLOCK M | ||
1051 | |||
1052 | But it won't see any of: | ||
1053 | |||
1054 | *B, *C or *D preceding LOCK M | ||
1055 | *A, *B or *C following UNLOCK M | ||
1056 | *F, *G or *H preceding LOCK Q | ||
1057 | *E, *F or *G following UNLOCK Q | ||
1058 | |||
1059 | |||
1060 | However, if the following occurs: | ||
1061 | |||
1062 | CPU 1 CPU 2 | ||
1063 | =============================== =============================== | ||
1064 | *A = a; | ||
1065 | LOCK M [1] | ||
1066 | *B = b; | ||
1067 | *C = c; | ||
1068 | UNLOCK M [1] | ||
1069 | *D = d; *E = e; | ||
1070 | LOCK M [2] | ||
1071 | *F = f; | ||
1072 | *G = g; | ||
1073 | UNLOCK M [2] | ||
1074 | *H = h; | ||
1075 | |||
1076 | CPU #3 might see: | ||
1077 | |||
1078 | *E, LOCK M [1], *C, *B, *A, UNLOCK M [1], | ||
1079 | LOCK M [2], *H, *F, *G, UNLOCK M [2], *D | ||
1080 | |||
1081 | But assuming CPU #1 gets the lock first, it won't see any of: | ||
1082 | |||
1083 | *B, *C, *D, *F, *G or *H preceding LOCK M [1] | ||
1084 | *A, *B or *C following UNLOCK M [1] | ||
1085 | *F, *G or *H preceding LOCK M [2] | ||
1086 | *A, *B, *C, *E, *F or *G following UNLOCK M [2] | ||
1087 | |||
1088 | |||
1089 | LOCKS VS I/O ACCESSES | ||
1090 | --------------------- | ||
1091 | |||
1092 | Under certain circumstances (especially involving NUMA), I/O accesses within | ||
1093 | two spinlocked sections on two different CPUs may be seen as interleaved by the | ||
1094 | PCI bridge, because the PCI bridge does not necessarily participate in the | ||
1095 | cache-coherence protocol, and is therefore incapable of issuing the required | ||
1096 | read memory barriers. | ||
1097 | |||
1098 | For example: | ||
1099 | |||
1100 | CPU 1 CPU 2 | ||
1101 | =============================== =============================== | ||
1102 | spin_lock(Q) | ||
1103 | writel(0, ADDR) | ||
1104 | writel(1, DATA); | ||
1105 | spin_unlock(Q); | ||
1106 | spin_lock(Q); | ||
1107 | writel(4, ADDR); | ||
1108 | writel(5, DATA); | ||
1109 | spin_unlock(Q); | ||
1110 | |||
1111 | may be seen by the PCI bridge as follows: | ||
1112 | |||
1113 | STORE *ADDR = 0, STORE *ADDR = 4, STORE *DATA = 1, STORE *DATA = 5 | ||
1114 | |||
1115 | which would probably cause the hardware to malfunction. | ||
1116 | |||
1117 | |||
1118 | What is necessary here is to intervene with an mmiowb() before dropping the | ||
1119 | spinlock, for example: | ||
1120 | |||
1121 | CPU 1 CPU 2 | ||
1122 | =============================== =============================== | ||
1123 | spin_lock(Q) | ||
1124 | writel(0, ADDR) | ||
1125 | writel(1, DATA); | ||
1126 | mmiowb(); | ||
1127 | spin_unlock(Q); | ||
1128 | spin_lock(Q); | ||
1129 | writel(4, ADDR); | ||
1130 | writel(5, DATA); | ||
1131 | mmiowb(); | ||
1132 | spin_unlock(Q); | ||
1133 | |||
1134 | this will ensure that the two stores issued on CPU #1 appear at the PCI bridge | ||
1135 | before either of the stores issued on CPU #2. | ||
1136 | |||
1137 | |||
1138 | Furthermore, following a store by a load to the same device obviates the need | ||
1139 | for an mmiowb(), because the load forces the store to complete before the load | ||
1140 | is performed: | ||
1141 | |||
1142 | CPU 1 CPU 2 | ||
1143 | =============================== =============================== | ||
1144 | spin_lock(Q) | ||
1145 | writel(0, ADDR) | ||
1146 | a = readl(DATA); | ||
1147 | spin_unlock(Q); | ||
1148 | spin_lock(Q); | ||
1149 | writel(4, ADDR); | ||
1150 | b = readl(DATA); | ||
1151 | spin_unlock(Q); | ||
1152 | |||
1153 | |||
1154 | See Documentation/DocBook/deviceiobook.tmpl for more information. | ||
1155 | |||
1156 | |||
1157 | ================================= | ||
1158 | WHERE ARE MEMORY BARRIERS NEEDED? | ||
1159 | ================================= | ||
1160 | |||
1161 | Under normal operation, memory operation reordering is generally not going to | ||
1162 | be a problem as a single-threaded linear piece of code will still appear to | ||
1163 | work correctly, even if it's in an SMP kernel. There are, however, three | ||
1164 | circumstances in which reordering definitely _could_ be a problem: | ||
1165 | |||
1166 | (*) Interprocessor interaction. | ||
1167 | |||
1168 | (*) Atomic operations. | ||
1169 | |||
1170 | (*) Accessing devices (I/O). | ||
1171 | |||
1172 | (*) Interrupts. | ||
1173 | |||
1174 | |||
1175 | INTERPROCESSOR INTERACTION | ||
1176 | -------------------------- | ||
1177 | |||
1178 | When there's a system with more than one processor, more than one CPU in the | ||
1179 | system may be working on the same data set at the same time. This can cause | ||
1180 | synchronisation problems, and the usual way of dealing with them is to use | ||
1181 | locks. Locks, however, are quite expensive, and so it may be preferable to | ||
1182 | operate without the use of a lock if at all possible. In such a case | ||
1183 | operations that affect both CPUs may have to be carefully ordered to prevent | ||
1184 | a malfunction. | ||
1185 | |||
1186 | Consider, for example, the R/W semaphore slow path. Here a waiting process is | ||
1187 | queued on the semaphore, by virtue of it having a piece of its stack linked to | ||
1188 | the semaphore's list of waiting processes: | ||
1189 | |||
1190 | struct rw_semaphore { | ||
1191 | ... | ||
1192 | spinlock_t lock; | ||
1193 | struct list_head waiters; | ||
1194 | }; | ||
1195 | |||
1196 | struct rwsem_waiter { | ||
1197 | struct list_head list; | ||
1198 | struct task_struct *task; | ||
1199 | }; | ||
1200 | |||
1201 | To wake up a particular waiter, the up_read() or up_write() functions have to: | ||
1202 | |||
1203 | (1) read the next pointer from this waiter's record to know as to where the | ||
1204 | next waiter record is; | ||
1205 | |||
1206 | (4) read the pointer to the waiter's task structure; | ||
1207 | |||
1208 | (3) clear the task pointer to tell the waiter it has been given the semaphore; | ||
1209 | |||
1210 | (4) call wake_up_process() on the task; and | ||
1211 | |||
1212 | (5) release the reference held on the waiter's task struct. | ||
1213 | |||
1214 | In otherwords, it has to perform this sequence of events: | ||
1215 | |||
1216 | LOAD waiter->list.next; | ||
1217 | LOAD waiter->task; | ||
1218 | STORE waiter->task; | ||
1219 | CALL wakeup | ||
1220 | RELEASE task | ||
1221 | |||
1222 | and if any of these steps occur out of order, then the whole thing may | ||
1223 | malfunction. | ||
1224 | |||
1225 | Once it has queued itself and dropped the semaphore lock, the waiter does not | ||
1226 | get the lock again; it instead just waits for its task pointer to be cleared | ||
1227 | before proceeding. Since the record is on the waiter's stack, this means that | ||
1228 | if the task pointer is cleared _before_ the next pointer in the list is read, | ||
1229 | another CPU might start processing the waiter and might clobber the waiter's | ||
1230 | stack before the up*() function has a chance to read the next pointer. | ||
1231 | |||
1232 | Consider then what might happen to the above sequence of events: | ||
1233 | |||
1234 | CPU 1 CPU 2 | ||
1235 | =============================== =============================== | ||
1236 | down_xxx() | ||
1237 | Queue waiter | ||
1238 | Sleep | ||
1239 | up_yyy() | ||
1240 | LOAD waiter->task; | ||
1241 | STORE waiter->task; | ||
1242 | Woken up by other event | ||
1243 | <preempt> | ||
1244 | Resume processing | ||
1245 | down_xxx() returns | ||
1246 | call foo() | ||
1247 | foo() clobbers *waiter | ||
1248 | </preempt> | ||
1249 | LOAD waiter->list.next; | ||
1250 | --- OOPS --- | ||
1251 | |||
1252 | This could be dealt with using the semaphore lock, but then the down_xxx() | ||
1253 | function has to needlessly get the spinlock again after being woken up. | ||
1254 | |||
1255 | The way to deal with this is to insert a general SMP memory barrier: | ||
1256 | |||
1257 | LOAD waiter->list.next; | ||
1258 | LOAD waiter->task; | ||
1259 | smp_mb(); | ||
1260 | STORE waiter->task; | ||
1261 | CALL wakeup | ||
1262 | RELEASE task | ||
1263 | |||
1264 | In this case, the barrier makes a guarantee that all memory accesses before the | ||
1265 | barrier will appear to happen before all the memory accesses after the barrier | ||
1266 | with respect to the other CPUs on the system. It does _not_ guarantee that all | ||
1267 | the memory accesses before the barrier will be complete by the time the barrier | ||
1268 | instruction itself is complete. | ||
1269 | |||
1270 | On a UP system - where this wouldn't be a problem - the smp_mb() is just a | ||
1271 | compiler barrier, thus making sure the compiler emits the instructions in the | ||
1272 | right order without actually intervening in the CPU. Since there there's only | ||
1273 | one CPU, that CPU's dependency ordering logic will take care of everything | ||
1274 | else. | ||
1275 | |||
1276 | |||
1277 | ATOMIC OPERATIONS | ||
1278 | ----------------- | ||
1279 | |||
1280 | Whilst they are technically interprocessor interaction considerations, atomic | ||
1281 | operations are noted specially as some of them imply full memory barriers and | ||
1282 | some don't, but they're very heavily relied on as a group throughout the | ||
1283 | kernel. | ||
1284 | |||
1285 | Any atomic operation that modifies some state in memory and returns information | ||
1286 | about the state (old or new) implies an SMP-conditional general memory barrier | ||
1287 | (smp_mb()) on each side of the actual operation. These include: | ||
1288 | |||
1289 | xchg(); | ||
1290 | cmpxchg(); | ||
1291 | atomic_cmpxchg(); | ||
1292 | atomic_inc_return(); | ||
1293 | atomic_dec_return(); | ||
1294 | atomic_add_return(); | ||
1295 | atomic_sub_return(); | ||
1296 | atomic_inc_and_test(); | ||
1297 | atomic_dec_and_test(); | ||
1298 | atomic_sub_and_test(); | ||
1299 | atomic_add_negative(); | ||
1300 | atomic_add_unless(); | ||
1301 | test_and_set_bit(); | ||
1302 | test_and_clear_bit(); | ||
1303 | test_and_change_bit(); | ||
1304 | |||
1305 | These are used for such things as implementing LOCK-class and UNLOCK-class | ||
1306 | operations and adjusting reference counters towards object destruction, and as | ||
1307 | such the implicit memory barrier effects are necessary. | ||
1308 | |||
1309 | |||
1310 | The following operation are potential problems as they do _not_ imply memory | ||
1311 | barriers, but might be used for implementing such things as UNLOCK-class | ||
1312 | operations: | ||
1313 | |||
1314 | atomic_set(); | ||
1315 | set_bit(); | ||
1316 | clear_bit(); | ||
1317 | change_bit(); | ||
1318 | |||
1319 | With these the appropriate explicit memory barrier should be used if necessary | ||
1320 | (smp_mb__before_clear_bit() for instance). | ||
1321 | |||
1322 | |||
1323 | The following also do _not_ imply memory barriers, and so may require explicit | ||
1324 | memory barriers under some circumstances (smp_mb__before_atomic_dec() for | ||
1325 | instance)): | ||
1326 | |||
1327 | atomic_add(); | ||
1328 | atomic_sub(); | ||
1329 | atomic_inc(); | ||
1330 | atomic_dec(); | ||
1331 | |||
1332 | If they're used for statistics generation, then they probably don't need memory | ||
1333 | barriers, unless there's a coupling between statistical data. | ||
1334 | |||
1335 | If they're used for reference counting on an object to control its lifetime, | ||
1336 | they probably don't need memory barriers because either the reference count | ||
1337 | will be adjusted inside a locked section, or the caller will already hold | ||
1338 | sufficient references to make the lock, and thus a memory barrier unnecessary. | ||
1339 | |||
1340 | If they're used for constructing a lock of some description, then they probably | ||
1341 | do need memory barriers as a lock primitive generally has to do things in a | ||
1342 | specific order. | ||
1343 | |||
1344 | |||
1345 | Basically, each usage case has to be carefully considered as to whether memory | ||
1346 | barriers are needed or not. | ||
1347 | |||
1348 | [!] Note that special memory barrier primitives are available for these | ||
1349 | situations because on some CPUs the atomic instructions used imply full memory | ||
1350 | barriers, and so barrier instructions are superfluous in conjunction with them, | ||
1351 | and in such cases the special barrier primitives will be no-ops. | ||
1352 | |||
1353 | See Documentation/atomic_ops.txt for more information. | ||
1354 | |||
1355 | |||
1356 | ACCESSING DEVICES | ||
1357 | ----------------- | ||
1358 | |||
1359 | Many devices can be memory mapped, and so appear to the CPU as if they're just | ||
1360 | a set of memory locations. To control such a device, the driver usually has to | ||
1361 | make the right memory accesses in exactly the right order. | ||
1362 | |||
1363 | However, having a clever CPU or a clever compiler creates a potential problem | ||
1364 | in that the carefully sequenced accesses in the driver code won't reach the | ||
1365 | device in the requisite order if the CPU or the compiler thinks it is more | ||
1366 | efficient to reorder, combine or merge accesses - something that would cause | ||
1367 | the device to malfunction. | ||
1368 | |||
1369 | Inside of the Linux kernel, I/O should be done through the appropriate accessor | ||
1370 | routines - such as inb() or writel() - which know how to make such accesses | ||
1371 | appropriately sequential. Whilst this, for the most part, renders the explicit | ||
1372 | use of memory barriers unnecessary, there are a couple of situations where they | ||
1373 | might be needed: | ||
1374 | |||
1375 | (1) On some systems, I/O stores are not strongly ordered across all CPUs, and | ||
1376 | so for _all_ general drivers locks should be used and mmiowb() must be | ||
1377 | issued prior to unlocking the critical section. | ||
1378 | |||
1379 | (2) If the accessor functions are used to refer to an I/O memory window with | ||
1380 | relaxed memory access properties, then _mandatory_ memory barriers are | ||
1381 | required to enforce ordering. | ||
1382 | |||
1383 | See Documentation/DocBook/deviceiobook.tmpl for more information. | ||
1384 | |||
1385 | |||
1386 | INTERRUPTS | ||
1387 | ---------- | ||
1388 | |||
1389 | A driver may be interrupted by its own interrupt service routine, and thus the | ||
1390 | two parts of the driver may interfere with each other's attempts to control or | ||
1391 | access the device. | ||
1392 | |||
1393 | This may be alleviated - at least in part - by disabling local interrupts (a | ||
1394 | form of locking), such that the critical operations are all contained within | ||
1395 | the interrupt-disabled section in the driver. Whilst the driver's interrupt | ||
1396 | routine is executing, the driver's core may not run on the same CPU, and its | ||
1397 | interrupt is not permitted to happen again until the current interrupt has been | ||
1398 | handled, thus the interrupt handler does not need to lock against that. | ||
1399 | |||
1400 | However, consider a driver that was talking to an ethernet card that sports an | ||
1401 | address register and a data register. If that driver's core talks to the card | ||
1402 | under interrupt-disablement and then the driver's interrupt handler is invoked: | ||
1403 | |||
1404 | LOCAL IRQ DISABLE | ||
1405 | writew(ADDR, 3); | ||
1406 | writew(DATA, y); | ||
1407 | LOCAL IRQ ENABLE | ||
1408 | <interrupt> | ||
1409 | writew(ADDR, 4); | ||
1410 | q = readw(DATA); | ||
1411 | </interrupt> | ||
1412 | |||
1413 | The store to the data register might happen after the second store to the | ||
1414 | address register if ordering rules are sufficiently relaxed: | ||
1415 | |||
1416 | STORE *ADDR = 3, STORE *ADDR = 4, STORE *DATA = y, q = LOAD *DATA | ||
1417 | |||
1418 | |||
1419 | If ordering rules are relaxed, it must be assumed that accesses done inside an | ||
1420 | interrupt disabled section may leak outside of it and may interleave with | ||
1421 | accesses performed in an interrupt - and vice versa - unless implicit or | ||
1422 | explicit barriers are used. | ||
1423 | |||
1424 | Normally this won't be a problem because the I/O accesses done inside such | ||
1425 | sections will include synchronous load operations on strictly ordered I/O | ||
1426 | registers that form implicit I/O barriers. If this isn't sufficient then an | ||
1427 | mmiowb() may need to be used explicitly. | ||
1428 | |||
1429 | |||
1430 | A similar situation may occur between an interrupt routine and two routines | ||
1431 | running on separate CPUs that communicate with each other. If such a case is | ||
1432 | likely, then interrupt-disabling locks should be used to guarantee ordering. | ||
1433 | |||
1434 | |||
1435 | ========================== | ||
1436 | KERNEL I/O BARRIER EFFECTS | ||
1437 | ========================== | ||
1438 | |||
1439 | When accessing I/O memory, drivers should use the appropriate accessor | ||
1440 | functions: | ||
1441 | |||
1442 | (*) inX(), outX(): | ||
1443 | |||
1444 | These are intended to talk to I/O space rather than memory space, but | ||
1445 | that's primarily a CPU-specific concept. The i386 and x86_64 processors do | ||
1446 | indeed have special I/O space access cycles and instructions, but many | ||
1447 | CPUs don't have such a concept. | ||
1448 | |||
1449 | The PCI bus, amongst others, defines an I/O space concept - which on such | ||
1450 | CPUs as i386 and x86_64 cpus readily maps to the CPU's concept of I/O | ||
1451 | space. However, it may also mapped as a virtual I/O space in the CPU's | ||
1452 | memory map, particularly on those CPUs that don't support alternate | ||
1453 | I/O spaces. | ||
1454 | |||
1455 | Accesses to this space may be fully synchronous (as on i386), but | ||
1456 | intermediary bridges (such as the PCI host bridge) may not fully honour | ||
1457 | that. | ||
1458 | |||
1459 | They are guaranteed to be fully ordered with respect to each other. | ||
1460 | |||
1461 | They are not guaranteed to be fully ordered with respect to other types of | ||
1462 | memory and I/O operation. | ||
1463 | |||
1464 | (*) readX(), writeX(): | ||
1465 | |||
1466 | Whether these are guaranteed to be fully ordered and uncombined with | ||
1467 | respect to each other on the issuing CPU depends on the characteristics | ||
1468 | defined for the memory window through which they're accessing. On later | ||
1469 | i386 architecture machines, for example, this is controlled by way of the | ||
1470 | MTRR registers. | ||
1471 | |||
1472 | Ordinarily, these will be guaranteed to be fully ordered and uncombined,, | ||
1473 | provided they're not accessing a prefetchable device. | ||
1474 | |||
1475 | However, intermediary hardware (such as a PCI bridge) may indulge in | ||
1476 | deferral if it so wishes; to flush a store, a load from the same location | ||
1477 | is preferred[*], but a load from the same device or from configuration | ||
1478 | space should suffice for PCI. | ||
1479 | |||
1480 | [*] NOTE! attempting to load from the same location as was written to may | ||
1481 | cause a malfunction - consider the 16550 Rx/Tx serial registers for | ||
1482 | example. | ||
1483 | |||
1484 | Used with prefetchable I/O memory, an mmiowb() barrier may be required to | ||
1485 | force stores to be ordered. | ||
1486 | |||
1487 | Please refer to the PCI specification for more information on interactions | ||
1488 | between PCI transactions. | ||
1489 | |||
1490 | (*) readX_relaxed() | ||
1491 | |||
1492 | These are similar to readX(), but are not guaranteed to be ordered in any | ||
1493 | way. Be aware that there is no I/O read barrier available. | ||
1494 | |||
1495 | (*) ioreadX(), iowriteX() | ||
1496 | |||
1497 | These will perform as appropriate for the type of access they're actually | ||
1498 | doing, be it inX()/outX() or readX()/writeX(). | ||
1499 | |||
1500 | |||
1501 | ======================================== | ||
1502 | ASSUMED MINIMUM EXECUTION ORDERING MODEL | ||
1503 | ======================================== | ||
1504 | |||
1505 | It has to be assumed that the conceptual CPU is weakly-ordered but that it will | ||
1506 | maintain the appearance of program causality with respect to itself. Some CPUs | ||
1507 | (such as i386 or x86_64) are more constrained than others (such as powerpc or | ||
1508 | frv), and so the most relaxed case (namely DEC Alpha) must be assumed outside | ||
1509 | of arch-specific code. | ||
1510 | |||
1511 | This means that it must be considered that the CPU will execute its instruction | ||
1512 | stream in any order it feels like - or even in parallel - provided that if an | ||
1513 | instruction in the stream depends on the an earlier instruction, then that | ||
1514 | earlier instruction must be sufficiently complete[*] before the later | ||
1515 | instruction may proceed; in other words: provided that the appearance of | ||
1516 | causality is maintained. | ||
1517 | |||
1518 | [*] Some instructions have more than one effect - such as changing the | ||
1519 | condition codes, changing registers or changing memory - and different | ||
1520 | instructions may depend on different effects. | ||
1521 | |||
1522 | A CPU may also discard any instruction sequence that winds up having no | ||
1523 | ultimate effect. For example, if two adjacent instructions both load an | ||
1524 | immediate value into the same register, the first may be discarded. | ||
1525 | |||
1526 | |||
1527 | Similarly, it has to be assumed that compiler might reorder the instruction | ||
1528 | stream in any way it sees fit, again provided the appearance of causality is | ||
1529 | maintained. | ||
1530 | |||
1531 | |||
1532 | ============================ | ||
1533 | THE EFFECTS OF THE CPU CACHE | ||
1534 | ============================ | ||
1535 | |||
1536 | The way cached memory operations are perceived across the system is affected to | ||
1537 | a certain extent by the caches that lie between CPUs and memory, and by the | ||
1538 | memory coherence system that maintains the consistency of state in the system. | ||
1539 | |||
1540 | As far as the way a CPU interacts with another part of the system through the | ||
1541 | caches goes, the memory system has to include the CPU's caches, and memory | ||
1542 | barriers for the most part act at the interface between the CPU and its cache | ||
1543 | (memory barriers logically act on the dotted line in the following diagram): | ||
1544 | |||
1545 | <--- CPU ---> : <----------- Memory -----------> | ||
1546 | : | ||
1547 | +--------+ +--------+ : +--------+ +-----------+ | ||
1548 | | | | | : | | | | +--------+ | ||
1549 | | CPU | | Memory | : | CPU | | | | | | ||
1550 | | Core |--->| Access |----->| Cache |<-->| | | | | ||
1551 | | | | Queue | : | | | |--->| Memory | | ||
1552 | | | | | : | | | | | | | ||
1553 | +--------+ +--------+ : +--------+ | | | | | ||
1554 | : | Cache | +--------+ | ||
1555 | : | Coherency | | ||
1556 | : | Mechanism | +--------+ | ||
1557 | +--------+ +--------+ : +--------+ | | | | | ||
1558 | | | | | : | | | | | | | ||
1559 | | CPU | | Memory | : | CPU | | |--->| Device | | ||
1560 | | Core |--->| Access |----->| Cache |<-->| | | | | ||
1561 | | | | Queue | : | | | | | | | ||
1562 | | | | | : | | | | +--------+ | ||
1563 | +--------+ +--------+ : +--------+ +-----------+ | ||
1564 | : | ||
1565 | : | ||
1566 | |||
1567 | Although any particular load or store may not actually appear outside of the | ||
1568 | CPU that issued it since it may have been satisfied within the CPU's own cache, | ||
1569 | it will still appear as if the full memory access had taken place as far as the | ||
1570 | other CPUs are concerned since the cache coherency mechanisms will migrate the | ||
1571 | cacheline over to the accessing CPU and propagate the effects upon conflict. | ||
1572 | |||
1573 | The CPU core may execute instructions in any order it deems fit, provided the | ||
1574 | expected program causality appears to be maintained. Some of the instructions | ||
1575 | generate load and store operations which then go into the queue of memory | ||
1576 | accesses to be performed. The core may place these in the queue in any order | ||
1577 | it wishes, and continue execution until it is forced to wait for an instruction | ||
1578 | to complete. | ||
1579 | |||
1580 | What memory barriers are concerned with is controlling the order in which | ||
1581 | accesses cross from the CPU side of things to the memory side of things, and | ||
1582 | the order in which the effects are perceived to happen by the other observers | ||
1583 | in the system. | ||
1584 | |||
1585 | [!] Memory barriers are _not_ needed within a given CPU, as CPUs always see | ||
1586 | their own loads and stores as if they had happened in program order. | ||
1587 | |||
1588 | [!] MMIO or other device accesses may bypass the cache system. This depends on | ||
1589 | the properties of the memory window through which devices are accessed and/or | ||
1590 | the use of any special device communication instructions the CPU may have. | ||
1591 | |||
1592 | |||
1593 | CACHE COHERENCY | ||
1594 | --------------- | ||
1595 | |||
1596 | Life isn't quite as simple as it may appear above, however: for while the | ||
1597 | caches are expected to be coherent, there's no guarantee that that coherency | ||
1598 | will be ordered. This means that whilst changes made on one CPU will | ||
1599 | eventually become visible on all CPUs, there's no guarantee that they will | ||
1600 | become apparent in the same order on those other CPUs. | ||
1601 | |||
1602 | |||
1603 | Consider dealing with a system that has pair of CPUs (1 & 2), each of which has | ||
1604 | a pair of parallel data caches (CPU 1 has A/B, and CPU 2 has C/D): | ||
1605 | |||
1606 | : | ||
1607 | : +--------+ | ||
1608 | : +---------+ | | | ||
1609 | +--------+ : +--->| Cache A |<------->| | | ||
1610 | | | : | +---------+ | | | ||
1611 | | CPU 1 |<---+ | | | ||
1612 | | | : | +---------+ | | | ||
1613 | +--------+ : +--->| Cache B |<------->| | | ||
1614 | : +---------+ | | | ||
1615 | : | Memory | | ||
1616 | : +---------+ | System | | ||
1617 | +--------+ : +--->| Cache C |<------->| | | ||
1618 | | | : | +---------+ | | | ||
1619 | | CPU 2 |<---+ | | | ||
1620 | | | : | +---------+ | | | ||
1621 | +--------+ : +--->| Cache D |<------->| | | ||
1622 | : +---------+ | | | ||
1623 | : +--------+ | ||
1624 | : | ||
1625 | |||
1626 | Imagine the system has the following properties: | ||
1627 | |||
1628 | (*) an odd-numbered cache line may be in cache A, cache C or it may still be | ||
1629 | resident in memory; | ||
1630 | |||
1631 | (*) an even-numbered cache line may be in cache B, cache D or it may still be | ||
1632 | resident in memory; | ||
1633 | |||
1634 | (*) whilst the CPU core is interrogating one cache, the other cache may be | ||
1635 | making use of the bus to access the rest of the system - perhaps to | ||
1636 | displace a dirty cacheline or to do a speculative load; | ||
1637 | |||
1638 | (*) each cache has a queue of operations that need to be applied to that cache | ||
1639 | to maintain coherency with the rest of the system; | ||
1640 | |||
1641 | (*) the coherency queue is not flushed by normal loads to lines already | ||
1642 | present in the cache, even though the contents of the queue may | ||
1643 | potentially effect those loads. | ||
1644 | |||
1645 | Imagine, then, that two writes are made on the first CPU, with a write barrier | ||
1646 | between them to guarantee that they will appear to reach that CPU's caches in | ||
1647 | the requisite order: | ||
1648 | |||
1649 | CPU 1 CPU 2 COMMENT | ||
1650 | =============== =============== ======================================= | ||
1651 | u == 0, v == 1 and p == &u, q == &u | ||
1652 | v = 2; | ||
1653 | smp_wmb(); Make sure change to v visible before | ||
1654 | change to p | ||
1655 | <A:modify v=2> v is now in cache A exclusively | ||
1656 | p = &v; | ||
1657 | <B:modify p=&v> p is now in cache B exclusively | ||
1658 | |||
1659 | The write memory barrier forces the other CPUs in the system to perceive that | ||
1660 | the local CPU's caches have apparently been updated in the correct order. But | ||
1661 | now imagine that the second CPU that wants to read those values: | ||
1662 | |||
1663 | CPU 1 CPU 2 COMMENT | ||
1664 | =============== =============== ======================================= | ||
1665 | ... | ||
1666 | q = p; | ||
1667 | x = *q; | ||
1668 | |||
1669 | The above pair of reads may then fail to happen in expected order, as the | ||
1670 | cacheline holding p may get updated in one of the second CPU's caches whilst | ||
1671 | the update to the cacheline holding v is delayed in the other of the second | ||
1672 | CPU's caches by some other cache event: | ||
1673 | |||
1674 | CPU 1 CPU 2 COMMENT | ||
1675 | =============== =============== ======================================= | ||
1676 | u == 0, v == 1 and p == &u, q == &u | ||
1677 | v = 2; | ||
1678 | smp_wmb(); | ||
1679 | <A:modify v=2> <C:busy> | ||
1680 | <C:queue v=2> | ||
1681 | p = &b; q = p; | ||
1682 | <D:request p> | ||
1683 | <B:modify p=&v> <D:commit p=&v> | ||
1684 | <D:read p> | ||
1685 | x = *q; | ||
1686 | <C:read *q> Reads from v before v updated in cache | ||
1687 | <C:unbusy> | ||
1688 | <C:commit v=2> | ||
1689 | |||
1690 | Basically, whilst both cachelines will be updated on CPU 2 eventually, there's | ||
1691 | no guarantee that, without intervention, the order of update will be the same | ||
1692 | as that committed on CPU 1. | ||
1693 | |||
1694 | |||
1695 | To intervene, we need to interpolate a data dependency barrier or a read | ||
1696 | barrier between the loads. This will force the cache to commit its coherency | ||
1697 | queue before processing any further requests: | ||
1698 | |||
1699 | CPU 1 CPU 2 COMMENT | ||
1700 | =============== =============== ======================================= | ||
1701 | u == 0, v == 1 and p == &u, q == &u | ||
1702 | v = 2; | ||
1703 | smp_wmb(); | ||
1704 | <A:modify v=2> <C:busy> | ||
1705 | <C:queue v=2> | ||
1706 | p = &b; q = p; | ||
1707 | <D:request p> | ||
1708 | <B:modify p=&v> <D:commit p=&v> | ||
1709 | <D:read p> | ||
1710 | smp_read_barrier_depends() | ||
1711 | <C:unbusy> | ||
1712 | <C:commit v=2> | ||
1713 | x = *q; | ||
1714 | <C:read *q> Reads from v after v updated in cache | ||
1715 | |||
1716 | |||
1717 | This sort of problem can be encountered on DEC Alpha processors as they have a | ||
1718 | split cache that improves performance by making better use of the data bus. | ||
1719 | Whilst most CPUs do imply a data dependency barrier on the read when a memory | ||
1720 | access depends on a read, not all do, so it may not be relied on. | ||
1721 | |||
1722 | Other CPUs may also have split caches, but must coordinate between the various | ||
1723 | cachelets for normal memory accesss. The semantics of the Alpha removes the | ||
1724 | need for coordination in absence of memory barriers. | ||
1725 | |||
1726 | |||
1727 | CACHE COHERENCY VS DMA | ||
1728 | ---------------------- | ||
1729 | |||
1730 | Not all systems maintain cache coherency with respect to devices doing DMA. In | ||
1731 | such cases, a device attempting DMA may obtain stale data from RAM because | ||
1732 | dirty cache lines may be resident in the caches of various CPUs, and may not | ||
1733 | have been written back to RAM yet. To deal with this, the appropriate part of | ||
1734 | the kernel must flush the overlapping bits of cache on each CPU (and maybe | ||
1735 | invalidate them as well). | ||
1736 | |||
1737 | In addition, the data DMA'd to RAM by a device may be overwritten by dirty | ||
1738 | cache lines being written back to RAM from a CPU's cache after the device has | ||
1739 | installed its own data, or cache lines simply present in a CPUs cache may | ||
1740 | simply obscure the fact that RAM has been updated, until at such time as the | ||
1741 | cacheline is discarded from the CPU's cache and reloaded. To deal with this, | ||
1742 | the appropriate part of the kernel must invalidate the overlapping bits of the | ||
1743 | cache on each CPU. | ||
1744 | |||
1745 | See Documentation/cachetlb.txt for more information on cache management. | ||
1746 | |||
1747 | |||
1748 | CACHE COHERENCY VS MMIO | ||
1749 | ----------------------- | ||
1750 | |||
1751 | Memory mapped I/O usually takes place through memory locations that are part of | ||
1752 | a window in the CPU's memory space that have different properties assigned than | ||
1753 | the usual RAM directed window. | ||
1754 | |||
1755 | Amongst these properties is usually the fact that such accesses bypass the | ||
1756 | caching entirely and go directly to the device buses. This means MMIO accesses | ||
1757 | may, in effect, overtake accesses to cached memory that were emitted earlier. | ||
1758 | A memory barrier isn't sufficient in such a case, but rather the cache must be | ||
1759 | flushed between the cached memory write and the MMIO access if the two are in | ||
1760 | any way dependent. | ||
1761 | |||
1762 | |||
1763 | ========================= | ||
1764 | THE THINGS CPUS GET UP TO | ||
1765 | ========================= | ||
1766 | |||
1767 | A programmer might take it for granted that the CPU will perform memory | ||
1768 | operations in exactly the order specified, so that if a CPU is, for example, | ||
1769 | given the following piece of code to execute: | ||
1770 | |||
1771 | a = *A; | ||
1772 | *B = b; | ||
1773 | c = *C; | ||
1774 | d = *D; | ||
1775 | *E = e; | ||
1776 | |||
1777 | They would then expect that the CPU will complete the memory operation for each | ||
1778 | instruction before moving on to the next one, leading to a definite sequence of | ||
1779 | operations as seen by external observers in the system: | ||
1780 | |||
1781 | LOAD *A, STORE *B, LOAD *C, LOAD *D, STORE *E. | ||
1782 | |||
1783 | |||
1784 | Reality is, of course, much messier. With many CPUs and compilers, the above | ||
1785 | assumption doesn't hold because: | ||
1786 | |||
1787 | (*) loads are more likely to need to be completed immediately to permit | ||
1788 | execution progress, whereas stores can often be deferred without a | ||
1789 | problem; | ||
1790 | |||
1791 | (*) loads may be done speculatively, and the result discarded should it prove | ||
1792 | to have been unnecessary; | ||
1793 | |||
1794 | (*) loads may be done speculatively, leading to the result having being | ||
1795 | fetched at the wrong time in the expected sequence of events; | ||
1796 | |||
1797 | (*) the order of the memory accesses may be rearranged to promote better use | ||
1798 | of the CPU buses and caches; | ||
1799 | |||
1800 | (*) loads and stores may be combined to improve performance when talking to | ||
1801 | memory or I/O hardware that can do batched accesses of adjacent locations, | ||
1802 | thus cutting down on transaction setup costs (memory and PCI devices may | ||
1803 | both be able to do this); and | ||
1804 | |||
1805 | (*) the CPU's data cache may affect the ordering, and whilst cache-coherency | ||
1806 | mechanisms may alleviate this - once the store has actually hit the cache | ||
1807 | - there's no guarantee that the coherency management will be propagated in | ||
1808 | order to other CPUs. | ||
1809 | |||
1810 | So what another CPU, say, might actually observe from the above piece of code | ||
1811 | is: | ||
1812 | |||
1813 | LOAD *A, ..., LOAD {*C,*D}, STORE *E, STORE *B | ||
1814 | |||
1815 | (Where "LOAD {*C,*D}" is a combined load) | ||
1816 | |||
1817 | |||
1818 | However, it is guaranteed that a CPU will be self-consistent: it will see its | ||
1819 | _own_ accesses appear to be correctly ordered, without the need for a memory | ||
1820 | barrier. For instance with the following code: | ||
1821 | |||
1822 | U = *A; | ||
1823 | *A = V; | ||
1824 | *A = W; | ||
1825 | X = *A; | ||
1826 | *A = Y; | ||
1827 | Z = *A; | ||
1828 | |||
1829 | and assuming no intervention by an external influence, it can be assumed that | ||
1830 | the final result will appear to be: | ||
1831 | |||
1832 | U == the original value of *A | ||
1833 | X == W | ||
1834 | Z == Y | ||
1835 | *A == Y | ||
1836 | |||
1837 | The code above may cause the CPU to generate the full sequence of memory | ||
1838 | accesses: | ||
1839 | |||
1840 | U=LOAD *A, STORE *A=V, STORE *A=W, X=LOAD *A, STORE *A=Y, Z=LOAD *A | ||
1841 | |||
1842 | in that order, but, without intervention, the sequence may have almost any | ||
1843 | combination of elements combined or discarded, provided the program's view of | ||
1844 | the world remains consistent. | ||
1845 | |||
1846 | The compiler may also combine, discard or defer elements of the sequence before | ||
1847 | the CPU even sees them. | ||
1848 | |||
1849 | For instance: | ||
1850 | |||
1851 | *A = V; | ||
1852 | *A = W; | ||
1853 | |||
1854 | may be reduced to: | ||
1855 | |||
1856 | *A = W; | ||
1857 | |||
1858 | since, without a write barrier, it can be assumed that the effect of the | ||
1859 | storage of V to *A is lost. Similarly: | ||
1860 | |||
1861 | *A = Y; | ||
1862 | Z = *A; | ||
1863 | |||
1864 | may, without a memory barrier, be reduced to: | ||
1865 | |||
1866 | *A = Y; | ||
1867 | Z = Y; | ||
1868 | |||
1869 | and the LOAD operation never appear outside of the CPU. | ||
1870 | |||
1871 | |||
1872 | AND THEN THERE'S THE ALPHA | ||
1873 | -------------------------- | ||
1874 | |||
1875 | The DEC Alpha CPU is one of the most relaxed CPUs there is. Not only that, | ||
1876 | some versions of the Alpha CPU have a split data cache, permitting them to have | ||
1877 | two semantically related cache lines updating at separate times. This is where | ||
1878 | the data dependency barrier really becomes necessary as this synchronises both | ||
1879 | caches with the memory coherence system, thus making it seem like pointer | ||
1880 | changes vs new data occur in the right order. | ||
1881 | |||
1882 | The Alpha defines the Linux's kernel's memory barrier model. | ||
1883 | |||
1884 | See the subsection on "Cache Coherency" above. | ||
1885 | |||
1886 | |||
1887 | ========== | ||
1888 | REFERENCES | ||
1889 | ========== | ||
1890 | |||
1891 | Alpha AXP Architecture Reference Manual, Second Edition (Sites & Witek, | ||
1892 | Digital Press) | ||
1893 | Chapter 5.2: Physical Address Space Characteristics | ||
1894 | Chapter 5.4: Caches and Write Buffers | ||
1895 | Chapter 5.5: Data Sharing | ||
1896 | Chapter 5.6: Read/Write Ordering | ||
1897 | |||
1898 | AMD64 Architecture Programmer's Manual Volume 2: System Programming | ||
1899 | Chapter 7.1: Memory-Access Ordering | ||
1900 | Chapter 7.4: Buffering and Combining Memory Writes | ||
1901 | |||
1902 | IA-32 Intel Architecture Software Developer's Manual, Volume 3: | ||
1903 | System Programming Guide | ||
1904 | Chapter 7.1: Locked Atomic Operations | ||
1905 | Chapter 7.2: Memory Ordering | ||
1906 | Chapter 7.4: Serializing Instructions | ||
1907 | |||
1908 | The SPARC Architecture Manual, Version 9 | ||
1909 | Chapter 8: Memory Models | ||
1910 | Appendix D: Formal Specification of the Memory Models | ||
1911 | Appendix J: Programming with the Memory Models | ||
1912 | |||
1913 | UltraSPARC Programmer Reference Manual | ||
1914 | Chapter 5: Memory Accesses and Cacheability | ||
1915 | Chapter 15: Sparc-V9 Memory Models | ||
1916 | |||
1917 | UltraSPARC III Cu User's Manual | ||
1918 | Chapter 9: Memory Models | ||
1919 | |||
1920 | UltraSPARC IIIi Processor User's Manual | ||
1921 | Chapter 8: Memory Models | ||
1922 | |||
1923 | UltraSPARC Architecture 2005 | ||
1924 | Chapter 9: Memory | ||
1925 | Appendix D: Formal Specifications of the Memory Models | ||
1926 | |||
1927 | UltraSPARC T1 Supplement to the UltraSPARC Architecture 2005 | ||
1928 | Chapter 8: Memory Models | ||
1929 | Appendix F: Caches and Cache Coherency | ||
1930 | |||
1931 | Solaris Internals, Core Kernel Architecture, p63-68: | ||
1932 | Chapter 3.3: Hardware Considerations for Locks and | ||
1933 | Synchronization | ||
1934 | |||
1935 | Unix Systems for Modern Architectures, Symmetric Multiprocessing and Caching | ||
1936 | for Kernel Programmers: | ||
1937 | Chapter 13: Other Memory Models | ||
1938 | |||
1939 | Intel Itanium Architecture Software Developer's Manual: Volume 1: | ||
1940 | Section 2.6: Speculation | ||
1941 | Section 4.4: Memory Access | ||
diff --git a/Documentation/mtrr.txt b/Documentation/mtrr.txt index b78af1c32996..c39ac395970e 100644 --- a/Documentation/mtrr.txt +++ b/Documentation/mtrr.txt | |||
@@ -138,19 +138,29 @@ Reading MTRRs from a C program using ioctl()'s: | |||
138 | 138 | ||
139 | */ | 139 | */ |
140 | #include <stdio.h> | 140 | #include <stdio.h> |
141 | #include <stdlib.h> | ||
141 | #include <string.h> | 142 | #include <string.h> |
142 | #include <sys/types.h> | 143 | #include <sys/types.h> |
143 | #include <sys/stat.h> | 144 | #include <sys/stat.h> |
144 | #include <fcntl.h> | 145 | #include <fcntl.h> |
145 | #include <sys/ioctl.h> | 146 | #include <sys/ioctl.h> |
146 | #include <errno.h> | 147 | #include <errno.h> |
147 | #define MTRR_NEED_STRINGS | ||
148 | #include <asm/mtrr.h> | 148 | #include <asm/mtrr.h> |
149 | 149 | ||
150 | #define TRUE 1 | 150 | #define TRUE 1 |
151 | #define FALSE 0 | 151 | #define FALSE 0 |
152 | #define ERRSTRING strerror (errno) | 152 | #define ERRSTRING strerror (errno) |
153 | 153 | ||
154 | static char *mtrr_strings[MTRR_NUM_TYPES] = | ||
155 | { | ||
156 | "uncachable", /* 0 */ | ||
157 | "write-combining", /* 1 */ | ||
158 | "?", /* 2 */ | ||
159 | "?", /* 3 */ | ||
160 | "write-through", /* 4 */ | ||
161 | "write-protect", /* 5 */ | ||
162 | "write-back", /* 6 */ | ||
163 | }; | ||
154 | 164 | ||
155 | int main () | 165 | int main () |
156 | { | 166 | { |
@@ -232,13 +242,22 @@ Creating MTRRs from a C programme using ioctl()'s: | |||
232 | #include <fcntl.h> | 242 | #include <fcntl.h> |
233 | #include <sys/ioctl.h> | 243 | #include <sys/ioctl.h> |
234 | #include <errno.h> | 244 | #include <errno.h> |
235 | #define MTRR_NEED_STRINGS | ||
236 | #include <asm/mtrr.h> | 245 | #include <asm/mtrr.h> |
237 | 246 | ||
238 | #define TRUE 1 | 247 | #define TRUE 1 |
239 | #define FALSE 0 | 248 | #define FALSE 0 |
240 | #define ERRSTRING strerror (errno) | 249 | #define ERRSTRING strerror (errno) |
241 | 250 | ||
251 | static char *mtrr_strings[MTRR_NUM_TYPES] = | ||
252 | { | ||
253 | "uncachable", /* 0 */ | ||
254 | "write-combining", /* 1 */ | ||
255 | "?", /* 2 */ | ||
256 | "?", /* 3 */ | ||
257 | "write-through", /* 4 */ | ||
258 | "write-protect", /* 5 */ | ||
259 | "write-back", /* 6 */ | ||
260 | }; | ||
242 | 261 | ||
243 | int main (int argc, char **argv) | 262 | int main (int argc, char **argv) |
244 | { | 263 | { |
diff --git a/Documentation/networking/TODO b/Documentation/networking/TODO deleted file mode 100644 index 66d36ff14bae..000000000000 --- a/Documentation/networking/TODO +++ /dev/null | |||
@@ -1,18 +0,0 @@ | |||
1 | To-do items for network drivers | ||
2 | ------------------------------- | ||
3 | |||
4 | * Move ethernet crc routine to generic code | ||
5 | |||
6 | * (for 2.5) Integrate Jamal Hadi Salim's netdev Rx polling API change | ||
7 | |||
8 | * Audit all net drivers to make sure magic packet / wake-on-lan / | ||
9 | similar features are disabled in the driver by default. | ||
10 | |||
11 | * Audit all net drivers to make sure the module always prints out a | ||
12 | version string when loaded as a module, but only prints a version | ||
13 | string when built into the kernel if a device is detected. | ||
14 | |||
15 | * Add ETHTOOL_GDRVINFO ioctl support to all ethernet drivers. | ||
16 | |||
17 | * dmfe PCI DMA is totally wrong and only works on x86 | ||
18 | |||
diff --git a/Documentation/networking/bcm43xx.txt b/Documentation/networking/bcm43xx.txt new file mode 100644 index 000000000000..28541d2bee1e --- /dev/null +++ b/Documentation/networking/bcm43xx.txt | |||
@@ -0,0 +1,36 @@ | |||
1 | |||
2 | BCM43xx Linux Driver Project | ||
3 | ============================ | ||
4 | |||
5 | About this software | ||
6 | ------------------- | ||
7 | |||
8 | The goal of this project is to develop a linux driver for Broadcom | ||
9 | BCM43xx chips, based on the specification at | ||
10 | http://bcm-specs.sipsolutions.net/ | ||
11 | |||
12 | The project page is http://bcm43xx.berlios.de/ | ||
13 | |||
14 | |||
15 | Requirements | ||
16 | ------------ | ||
17 | |||
18 | 1) Linux Kernel 2.6.16 or later | ||
19 | http://www.kernel.org/ | ||
20 | |||
21 | You may want to configure your kernel with: | ||
22 | |||
23 | CONFIG_DEBUG_FS (optional): | ||
24 | -> Kernel hacking | ||
25 | -> Debug Filesystem | ||
26 | |||
27 | 2) SoftMAC IEEE 802.11 Networking Stack extension and patched ieee80211 | ||
28 | modules: | ||
29 | http://softmac.sipsolutions.net/ | ||
30 | |||
31 | 3) Firmware Files | ||
32 | |||
33 | Please try fwcutter. Fwcutter can extract the firmware from various | ||
34 | binary driver files. It supports driver files from Windows, MacOS and | ||
35 | Linux. You can get fwcutter from http://bcm43xx.berlios.de/. | ||
36 | Also, fwcutter comes with a README file for further instructions. | ||
diff --git a/Documentation/networking/packet_mmap.txt b/Documentation/networking/packet_mmap.txt index 4fc8e9874320..aaf99d5f0dad 100644 --- a/Documentation/networking/packet_mmap.txt +++ b/Documentation/networking/packet_mmap.txt | |||
@@ -254,7 +254,7 @@ and, the number of frames be | |||
254 | 254 | ||
255 | <block number> * <block size> / <frame size> | 255 | <block number> * <block size> / <frame size> |
256 | 256 | ||
257 | Suposse the following parameters, which apply for 2.6 kernel and an | 257 | Suppose the following parameters, which apply for 2.6 kernel and an |
258 | i386 architecture: | 258 | i386 architecture: |
259 | 259 | ||
260 | <size-max> = 131072 bytes | 260 | <size-max> = 131072 bytes |
diff --git a/Documentation/networking/tuntap.txt b/Documentation/networking/tuntap.txt index ec3d109d787a..76750fb9151a 100644 --- a/Documentation/networking/tuntap.txt +++ b/Documentation/networking/tuntap.txt | |||
@@ -138,7 +138,7 @@ This means that you have to read/write IP packets when you are using tun and | |||
138 | ethernet frames when using tap. | 138 | ethernet frames when using tap. |
139 | 139 | ||
140 | 5. What is the difference between BPF and TUN/TAP driver? | 140 | 5. What is the difference between BPF and TUN/TAP driver? |
141 | BFP is an advanced packet filter. It can be attached to existing | 141 | BPF is an advanced packet filter. It can be attached to existing |
142 | network interface. It does not provide a virtual network interface. | 142 | network interface. It does not provide a virtual network interface. |
143 | A TUN/TAP driver does provide a virtual network interface and it is possible | 143 | A TUN/TAP driver does provide a virtual network interface and it is possible |
144 | to attach BPF to this interface. | 144 | to attach BPF to this interface. |
diff --git a/Documentation/networking/xfrm_sync.txt b/Documentation/networking/xfrm_sync.txt new file mode 100644 index 000000000000..8be626f7c0b8 --- /dev/null +++ b/Documentation/networking/xfrm_sync.txt | |||
@@ -0,0 +1,166 @@ | |||
1 | |||
2 | The sync patches work is based on initial patches from | ||
3 | Krisztian <hidden@balabit.hu> and others and additional patches | ||
4 | from Jamal <hadi@cyberus.ca>. | ||
5 | |||
6 | The end goal for syncing is to be able to insert attributes + generate | ||
7 | events so that the an SA can be safely moved from one machine to another | ||
8 | for HA purposes. | ||
9 | The idea is to synchronize the SA so that the takeover machine can do | ||
10 | the processing of the SA as accurate as possible if it has access to it. | ||
11 | |||
12 | We already have the ability to generate SA add/del/upd events. | ||
13 | These patches add ability to sync and have accurate lifetime byte (to | ||
14 | ensure proper decay of SAs) and replay counters to avoid replay attacks | ||
15 | with as minimal loss at failover time. | ||
16 | This way a backup stays as closely uptodate as an active member. | ||
17 | |||
18 | Because the above items change for every packet the SA receives, | ||
19 | it is possible for a lot of the events to be generated. | ||
20 | For this reason, we also add a nagle-like algorithm to restrict | ||
21 | the events. i.e we are going to set thresholds to say "let me | ||
22 | know if the replay sequence threshold is reached or 10 secs have passed" | ||
23 | These thresholds are set system-wide via sysctls or can be updated | ||
24 | per SA. | ||
25 | |||
26 | The identified items that need to be synchronized are: | ||
27 | - the lifetime byte counter | ||
28 | note that: lifetime time limit is not important if you assume the failover | ||
29 | machine is known ahead of time since the decay of the time countdown | ||
30 | is not driven by packet arrival. | ||
31 | - the replay sequence for both inbound and outbound | ||
32 | |||
33 | 1) Message Structure | ||
34 | ---------------------- | ||
35 | |||
36 | nlmsghdr:aevent_id:optional-TLVs. | ||
37 | |||
38 | The netlink message types are: | ||
39 | |||
40 | XFRM_MSG_NEWAE and XFRM_MSG_GETAE. | ||
41 | |||
42 | A XFRM_MSG_GETAE does not have TLVs. | ||
43 | A XFRM_MSG_NEWAE will have at least two TLVs (as is | ||
44 | discussed further below). | ||
45 | |||
46 | aevent_id structure looks like: | ||
47 | |||
48 | struct xfrm_aevent_id { | ||
49 | struct xfrm_usersa_id sa_id; | ||
50 | __u32 flags; | ||
51 | }; | ||
52 | |||
53 | xfrm_usersa_id in this message layout identifies the SA. | ||
54 | |||
55 | flags are used to indicate different things. The possible | ||
56 | flags are: | ||
57 | XFRM_AE_RTHR=1, /* replay threshold*/ | ||
58 | XFRM_AE_RVAL=2, /* replay value */ | ||
59 | XFRM_AE_LVAL=4, /* lifetime value */ | ||
60 | XFRM_AE_ETHR=8, /* expiry timer threshold */ | ||
61 | XFRM_AE_CR=16, /* Event cause is replay update */ | ||
62 | XFRM_AE_CE=32, /* Event cause is timer expiry */ | ||
63 | XFRM_AE_CU=64, /* Event cause is policy update */ | ||
64 | |||
65 | How these flags are used is dependent on the direction of the | ||
66 | message (kernel<->user) as well the cause (config, query or event). | ||
67 | This is described below in the different messages. | ||
68 | |||
69 | The pid will be set appropriately in netlink to recognize direction | ||
70 | (0 to the kernel and pid = processid that created the event | ||
71 | when going from kernel to user space) | ||
72 | |||
73 | A program needs to subscribe to multicast group XFRMNLGRP_AEVENTS | ||
74 | to get notified of these events. | ||
75 | |||
76 | 2) TLVS reflect the different parameters: | ||
77 | ----------------------------------------- | ||
78 | |||
79 | a) byte value (XFRMA_LTIME_VAL) | ||
80 | This TLV carries the running/current counter for byte lifetime since | ||
81 | last event. | ||
82 | |||
83 | b)replay value (XFRMA_REPLAY_VAL) | ||
84 | This TLV carries the running/current counter for replay sequence since | ||
85 | last event. | ||
86 | |||
87 | c)replay threshold (XFRMA_REPLAY_THRESH) | ||
88 | This TLV carries the threshold being used by the kernel to trigger events | ||
89 | when the replay sequence is exceeded. | ||
90 | |||
91 | d) expiry timer (XFRMA_ETIMER_THRESH) | ||
92 | This is a timer value in milliseconds which is used as the nagle | ||
93 | value to rate limit the events. | ||
94 | |||
95 | 3) Default configurations for the parameters: | ||
96 | ---------------------------------------------- | ||
97 | |||
98 | By default these events should be turned off unless there is | ||
99 | at least one listener registered to listen to the multicast | ||
100 | group XFRMNLGRP_AEVENTS. | ||
101 | |||
102 | Programs installing SAs will need to specify the two thresholds, however, | ||
103 | in order to not change existing applications such as racoon | ||
104 | we also provide default threshold values for these different parameters | ||
105 | in case they are not specified. | ||
106 | |||
107 | the two sysctls/proc entries are: | ||
108 | a) /proc/sys/net/core/sysctl_xfrm_aevent_etime | ||
109 | used to provide default values for the XFRMA_ETIMER_THRESH in incremental | ||
110 | units of time of 100ms. The default is 10 (1 second) | ||
111 | |||
112 | b) /proc/sys/net/core/sysctl_xfrm_aevent_rseqth | ||
113 | used to provide default values for XFRMA_REPLAY_THRESH parameter | ||
114 | in incremental packet count. The default is two packets. | ||
115 | |||
116 | 4) Message types | ||
117 | ---------------- | ||
118 | |||
119 | a) XFRM_MSG_GETAE issued by user-->kernel. | ||
120 | XFRM_MSG_GETAE does not carry any TLVs. | ||
121 | The response is a XFRM_MSG_NEWAE which is formatted based on what | ||
122 | XFRM_MSG_GETAE queried for. | ||
123 | The response will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. | ||
124 | *if XFRM_AE_RTHR flag is set, then XFRMA_REPLAY_THRESH is also retrieved | ||
125 | *if XFRM_AE_ETHR flag is set, then XFRMA_ETIMER_THRESH is also retrieved | ||
126 | |||
127 | b) XFRM_MSG_NEWAE is issued by either user space to configure | ||
128 | or kernel to announce events or respond to a XFRM_MSG_GETAE. | ||
129 | |||
130 | i) user --> kernel to configure a specific SA. | ||
131 | any of the values or threshold parameters can be updated by passing the | ||
132 | appropriate TLV. | ||
133 | A response is issued back to the sender in user space to indicate success | ||
134 | or failure. | ||
135 | In the case of success, additionally an event with | ||
136 | XFRM_MSG_NEWAE is also issued to any listeners as described in iii). | ||
137 | |||
138 | ii) kernel->user direction as a response to XFRM_MSG_GETAE | ||
139 | The response will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. | ||
140 | The threshold TLVs will be included if explicitly requested in | ||
141 | the XFRM_MSG_GETAE message. | ||
142 | |||
143 | iii) kernel->user to report as event if someone sets any values or | ||
144 | thresholds for an SA using XFRM_MSG_NEWAE (as described in #i above). | ||
145 | In such a case XFRM_AE_CU flag is set to inform the user that | ||
146 | the change happened as a result of an update. | ||
147 | The message will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. | ||
148 | |||
149 | iv) kernel->user to report event when replay threshold or a timeout | ||
150 | is exceeded. | ||
151 | In such a case either XFRM_AE_CR (replay exceeded) or XFRM_AE_CE (timeout | ||
152 | happened) is set to inform the user what happened. | ||
153 | Note the two flags are mutually exclusive. | ||
154 | The message will always have XFRMA_LTIME_VAL and XFRMA_REPLAY_VAL TLVs. | ||
155 | |||
156 | Exceptions to threshold settings | ||
157 | -------------------------------- | ||
158 | |||
159 | If you have an SA that is getting hit by traffic in bursts such that | ||
160 | there is a period where the timer threshold expires with no packets | ||
161 | seen, then an odd behavior is seen as follows: | ||
162 | The first packet arrival after a timer expiry will trigger a timeout | ||
163 | aevent; i.e we dont wait for a timeout period or a packet threshold | ||
164 | to be reached. This is done for simplicity and efficiency reasons. | ||
165 | |||
166 | -JHS | ||
diff --git a/Documentation/pcmcia/driver-changes.txt b/Documentation/pcmcia/driver-changes.txt index 97420f08c786..4739c5c3face 100644 --- a/Documentation/pcmcia/driver-changes.txt +++ b/Documentation/pcmcia/driver-changes.txt | |||
@@ -1,5 +1,11 @@ | |||
1 | This file details changes in 2.6 which affect PCMCIA card driver authors: | 1 | This file details changes in 2.6 which affect PCMCIA card driver authors: |
2 | 2 | ||
3 | * New release helper (as of 2.6.17) | ||
4 | Instead of calling pcmcia_release_{configuration,io,irq,win}, all that's | ||
5 | necessary now is calling pcmcia_disable_device. As there is no valid | ||
6 | reason left to call pcmcia_release_io and pcmcia_release_irq, the | ||
7 | exports for them were removed. | ||
8 | |||
3 | * Unify detach and REMOVAL event code, as well as attach and INSERTION | 9 | * Unify detach and REMOVAL event code, as well as attach and INSERTION |
4 | code (as of 2.6.16) | 10 | code (as of 2.6.16) |
5 | void (*remove) (struct pcmcia_device *dev); | 11 | void (*remove) (struct pcmcia_device *dev); |
diff --git a/Documentation/powerpc/booting-without-of.txt b/Documentation/powerpc/booting-without-of.txt index ee551c6ea235..217e51768b87 100644 --- a/Documentation/powerpc/booting-without-of.txt +++ b/Documentation/powerpc/booting-without-of.txt | |||
@@ -719,6 +719,11 @@ address which can extend beyond that limit. | |||
719 | - model : this is your board name/model | 719 | - model : this is your board name/model |
720 | - #address-cells : address representation for "root" devices | 720 | - #address-cells : address representation for "root" devices |
721 | - #size-cells: the size representation for "root" devices | 721 | - #size-cells: the size representation for "root" devices |
722 | - device_type : This property shouldn't be necessary. However, if | ||
723 | you decide to create a device_type for your root node, make sure it | ||
724 | is _not_ "chrp" unless your platform is a pSeries or PAPR compliant | ||
725 | one for 64-bit, or a CHRP-type machine for 32-bit as this will | ||
726 | matched by the kernel this way. | ||
722 | 727 | ||
723 | Additionally, some recommended properties are: | 728 | Additionally, some recommended properties are: |
724 | 729 | ||
diff --git a/Documentation/scsi/scsi_eh.txt b/Documentation/scsi/scsi_eh.txt index 331afd791cbb..ce767b90bb0d 100644 --- a/Documentation/scsi/scsi_eh.txt +++ b/Documentation/scsi/scsi_eh.txt | |||
@@ -19,9 +19,9 @@ TABLE OF CONTENTS | |||
19 | [2-1-1] Overview | 19 | [2-1-1] Overview |
20 | [2-1-2] Flow of scmds through EH | 20 | [2-1-2] Flow of scmds through EH |
21 | [2-1-3] Flow of control | 21 | [2-1-3] Flow of control |
22 | [2-2] EH through hostt->eh_strategy_handler() | 22 | [2-2] EH through transportt->eh_strategy_handler() |
23 | [2-2-1] Pre hostt->eh_strategy_handler() SCSI midlayer conditions | 23 | [2-2-1] Pre transportt->eh_strategy_handler() SCSI midlayer conditions |
24 | [2-2-2] Post hostt->eh_strategy_handler() SCSI midlayer conditions | 24 | [2-2-2] Post transportt->eh_strategy_handler() SCSI midlayer conditions |
25 | [2-2-3] Things to consider | 25 | [2-2-3] Things to consider |
26 | 26 | ||
27 | 27 | ||
@@ -413,9 +413,9 @@ scmd->allowed. | |||
413 | layer of failure of the scmds. | 413 | layer of failure of the scmds. |
414 | 414 | ||
415 | 415 | ||
416 | [2-2] EH through hostt->eh_strategy_handler() | 416 | [2-2] EH through transportt->eh_strategy_handler() |
417 | 417 | ||
418 | hostt->eh_strategy_handler() is invoked in the place of | 418 | transportt->eh_strategy_handler() is invoked in the place of |
419 | scsi_unjam_host() and it is responsible for whole recovery process. | 419 | scsi_unjam_host() and it is responsible for whole recovery process. |
420 | On completion, the handler should have made lower layers forget about | 420 | On completion, the handler should have made lower layers forget about |
421 | all failed scmds and either ready for new commands or offline. Also, | 421 | all failed scmds and either ready for new commands or offline. Also, |
@@ -424,7 +424,7 @@ SCSI midlayer. IOW, of the steps described in [2-1-2], all steps | |||
424 | except for #1 must be implemented by eh_strategy_handler(). | 424 | except for #1 must be implemented by eh_strategy_handler(). |
425 | 425 | ||
426 | 426 | ||
427 | [2-2-1] Pre hostt->eh_strategy_handler() SCSI midlayer conditions | 427 | [2-2-1] Pre transportt->eh_strategy_handler() SCSI midlayer conditions |
428 | 428 | ||
429 | The following conditions are true on entry to the handler. | 429 | The following conditions are true on entry to the handler. |
430 | 430 | ||
@@ -437,7 +437,7 @@ except for #1 must be implemented by eh_strategy_handler(). | |||
437 | - shost->host_failed == shost->host_busy | 437 | - shost->host_failed == shost->host_busy |
438 | 438 | ||
439 | 439 | ||
440 | [2-2-2] Post hostt->eh_strategy_handler() SCSI midlayer conditions | 440 | [2-2-2] Post transportt->eh_strategy_handler() SCSI midlayer conditions |
441 | 441 | ||
442 | The following conditions must be true on exit from the handler. | 442 | The following conditions must be true on exit from the handler. |
443 | 443 | ||
diff --git a/Documentation/scsi/scsi_mid_low_api.txt b/Documentation/scsi/scsi_mid_low_api.txt index 8bbae3e1abdf..75a535a975c3 100644 --- a/Documentation/scsi/scsi_mid_low_api.txt +++ b/Documentation/scsi/scsi_mid_low_api.txt | |||
@@ -804,7 +804,6 @@ Summary: | |||
804 | eh_bus_reset_handler - issue SCSI bus reset | 804 | eh_bus_reset_handler - issue SCSI bus reset |
805 | eh_device_reset_handler - issue SCSI device reset | 805 | eh_device_reset_handler - issue SCSI device reset |
806 | eh_host_reset_handler - reset host (host bus adapter) | 806 | eh_host_reset_handler - reset host (host bus adapter) |
807 | eh_strategy_handler - driver supplied alternate to scsi_unjam_host() | ||
808 | info - supply information about given host | 807 | info - supply information about given host |
809 | ioctl - driver can respond to ioctls | 808 | ioctl - driver can respond to ioctls |
810 | proc_info - supports /proc/scsi/{driver_name}/{host_no} | 809 | proc_info - supports /proc/scsi/{driver_name}/{host_no} |
@@ -970,24 +969,6 @@ Details: | |||
970 | 969 | ||
971 | 970 | ||
972 | /** | 971 | /** |
973 | * eh_strategy_handler - driver supplied alternate to scsi_unjam_host() | ||
974 | * @shp: host on which error has occurred | ||
975 | * | ||
976 | * Returns TRUE if host unjammed, else FALSE. | ||
977 | * | ||
978 | * Locks: none | ||
979 | * | ||
980 | * Calling context: kernel thread | ||
981 | * | ||
982 | * Notes: Invoked from scsi_eh thread. LLD supplied alternate to | ||
983 | * scsi_unjam_host() found in scsi_error.c | ||
984 | * | ||
985 | * Optionally defined in: LLD | ||
986 | **/ | ||
987 | int eh_strategy_handler(struct Scsi_Host * shp) | ||
988 | |||
989 | |||
990 | /** | ||
991 | * info - supply information about given host: driver name plus data | 972 | * info - supply information about given host: driver name plus data |
992 | * to distinguish given host | 973 | * to distinguish given host |
993 | * @shp: host to supply information about | 974 | * @shp: host to supply information about |
diff --git a/Documentation/serial/driver b/Documentation/serial/driver index 42ef9970bc86..df82116a9f26 100644 --- a/Documentation/serial/driver +++ b/Documentation/serial/driver | |||
@@ -3,14 +3,11 @@ | |||
3 | -------------------- | 3 | -------------------- |
4 | 4 | ||
5 | 5 | ||
6 | $Id: driver,v 1.10 2002/07/22 15:27:30 rmk Exp $ | ||
7 | |||
8 | |||
9 | This document is meant as a brief overview of some aspects of the new serial | 6 | This document is meant as a brief overview of some aspects of the new serial |
10 | driver. It is not complete, any questions you have should be directed to | 7 | driver. It is not complete, any questions you have should be directed to |
11 | <rmk@arm.linux.org.uk> | 8 | <rmk@arm.linux.org.uk> |
12 | 9 | ||
13 | The reference implementation is contained within serial_amba.c. | 10 | The reference implementation is contained within amba_pl011.c. |
14 | 11 | ||
15 | 12 | ||
16 | 13 | ||
@@ -31,6 +28,11 @@ The serial core provides a few helper functions. This includes identifing | |||
31 | the correct port structure (via uart_get_console) and decoding command line | 28 | the correct port structure (via uart_get_console) and decoding command line |
32 | arguments (uart_parse_options). | 29 | arguments (uart_parse_options). |
33 | 30 | ||
31 | There is also a helper function (uart_write_console) which performs a | ||
32 | character by character write, translating newlines to CRLF sequences. | ||
33 | Driver writers are recommended to use this function rather than implementing | ||
34 | their own version. | ||
35 | |||
34 | 36 | ||
35 | Locking | 37 | Locking |
36 | ------- | 38 | ------- |
@@ -86,6 +88,7 @@ hardware. | |||
86 | - TIOCM_DTR DTR signal. | 88 | - TIOCM_DTR DTR signal. |
87 | - TIOCM_OUT1 OUT1 signal. | 89 | - TIOCM_OUT1 OUT1 signal. |
88 | - TIOCM_OUT2 OUT2 signal. | 90 | - TIOCM_OUT2 OUT2 signal. |
91 | - TIOCM_LOOP Set the port into loopback mode. | ||
89 | If the appropriate bit is set, the signal should be driven | 92 | If the appropriate bit is set, the signal should be driven |
90 | active. If the bit is clear, the signal should be driven | 93 | active. If the bit is clear, the signal should be driven |
91 | inactive. | 94 | inactive. |
@@ -141,6 +144,10 @@ hardware. | |||
141 | enable_ms(port) | 144 | enable_ms(port) |
142 | Enable the modem status interrupts. | 145 | Enable the modem status interrupts. |
143 | 146 | ||
147 | This method may be called multiple times. Modem status | ||
148 | interrupts should be disabled when the shutdown method is | ||
149 | called. | ||
150 | |||
144 | Locking: port->lock taken. | 151 | Locking: port->lock taken. |
145 | Interrupts: locally disabled. | 152 | Interrupts: locally disabled. |
146 | This call must not sleep | 153 | This call must not sleep |
@@ -160,6 +167,8 @@ hardware. | |||
160 | state. Enable the port for reception. It should not activate | 167 | state. Enable the port for reception. It should not activate |
161 | RTS nor DTR; this will be done via a separate call to set_mctrl. | 168 | RTS nor DTR; this will be done via a separate call to set_mctrl. |
162 | 169 | ||
170 | This method will only be called when the port is initially opened. | ||
171 | |||
163 | Locking: port_sem taken. | 172 | Locking: port_sem taken. |
164 | Interrupts: globally disabled. | 173 | Interrupts: globally disabled. |
165 | 174 | ||
@@ -169,6 +178,11 @@ hardware. | |||
169 | RTS nor DTR; this will have already been done via a separate | 178 | RTS nor DTR; this will have already been done via a separate |
170 | call to set_mctrl. | 179 | call to set_mctrl. |
171 | 180 | ||
181 | Drivers must not access port->info once this call has completed. | ||
182 | |||
183 | This method will only be called when there are no more users of | ||
184 | this port. | ||
185 | |||
172 | Locking: port_sem taken. | 186 | Locking: port_sem taken. |
173 | Interrupts: caller dependent. | 187 | Interrupts: caller dependent. |
174 | 188 | ||
diff --git a/Documentation/sound/alsa/ALSA-Configuration.txt b/Documentation/sound/alsa/ALSA-Configuration.txt index 1def6049784c..0ee2c7dfc482 100644 --- a/Documentation/sound/alsa/ALSA-Configuration.txt +++ b/Documentation/sound/alsa/ALSA-Configuration.txt | |||
@@ -120,6 +120,34 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed. | |||
120 | enable - enable card | 120 | enable - enable card |
121 | - Default: enabled, for PCI and ISA PnP cards | 121 | - Default: enabled, for PCI and ISA PnP cards |
122 | 122 | ||
123 | Module snd-adlib | ||
124 | ---------------- | ||
125 | |||
126 | Module for AdLib FM cards. | ||
127 | |||
128 | port - port # for OPL chip | ||
129 | |||
130 | This module supports multiple cards. It does not support autoprobe, so | ||
131 | the port must be specified. For actual AdLib FM cards it will be 0x388. | ||
132 | Note that this card does not have PCM support and no mixer; only FM | ||
133 | synthesis. | ||
134 | |||
135 | Make sure you have "sbiload" from the alsa-tools package available and, | ||
136 | after loading the module, find out the assigned ALSA sequencer port | ||
137 | number through "sbiload -l". Example output: | ||
138 | |||
139 | Port Client name Port name | ||
140 | 64:0 OPL2 FM synth OPL2 FM Port | ||
141 | |||
142 | Load the std.sb and drums.sb patches also supplied by sbiload: | ||
143 | |||
144 | sbiload -p 64:0 std.sb drums.sb | ||
145 | |||
146 | If you use this driver to drive an OPL3, you can use std.o3 and drums.o3 | ||
147 | instead. To have the card produce sound, use aplaymidi from alsa-utils: | ||
148 | |||
149 | aplaymidi -p 64:0 foo.mid | ||
150 | |||
123 | Module snd-ad1816a | 151 | Module snd-ad1816a |
124 | ------------------ | 152 | ------------------ |
125 | 153 | ||
@@ -190,6 +218,15 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed. | |||
190 | 218 | ||
191 | The power-management is supported. | 219 | The power-management is supported. |
192 | 220 | ||
221 | Module snd-als300 | ||
222 | ----------------- | ||
223 | |||
224 | Module for Avance Logic ALS300 and ALS300+ | ||
225 | |||
226 | This module supports multiple cards. | ||
227 | |||
228 | The power-management is supported. | ||
229 | |||
193 | Module snd-als4000 | 230 | Module snd-als4000 |
194 | ------------------ | 231 | ------------------ |
195 | 232 | ||
@@ -701,6 +738,7 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed. | |||
701 | uniwill 3-jack | 738 | uniwill 3-jack |
702 | F1734 2-jack | 739 | F1734 2-jack |
703 | lg LG laptop (m1 express dual) | 740 | lg LG laptop (m1 express dual) |
741 | lg-lw LG LW20 laptop | ||
704 | test for testing/debugging purpose, almost all controls can be | 742 | test for testing/debugging purpose, almost all controls can be |
705 | adjusted. Appearing only when compiled with | 743 | adjusted. Appearing only when compiled with |
706 | $CONFIG_SND_DEBUG=y | 744 | $CONFIG_SND_DEBUG=y |
@@ -1013,6 +1051,23 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed. | |||
1013 | 1051 | ||
1014 | The power-management is supported. | 1052 | The power-management is supported. |
1015 | 1053 | ||
1054 | Module snd-miro | ||
1055 | --------------- | ||
1056 | |||
1057 | Module for Miro soundcards: miroSOUND PCM 1 pro, | ||
1058 | miroSOUND PCM 12, | ||
1059 | miroSOUND PCM 20 Radio. | ||
1060 | |||
1061 | port - Port # (0x530,0x604,0xe80,0xf40) | ||
1062 | irq - IRQ # (5,7,9,10,11) | ||
1063 | dma1 - 1st dma # (0,1,3) | ||
1064 | dma2 - 2nd dma # (0,1) | ||
1065 | mpu_port - MPU-401 port # (0x300,0x310,0x320,0x330) | ||
1066 | mpu_irq - MPU-401 irq # (5,7,9,10) | ||
1067 | fm_port - FM Port # (0x388) | ||
1068 | wss - enable WSS mode | ||
1069 | ide - enable onboard ide support | ||
1070 | |||
1016 | Module snd-mixart | 1071 | Module snd-mixart |
1017 | ----------------- | 1072 | ----------------- |
1018 | 1073 | ||
@@ -1202,6 +1257,20 @@ Prior to version 0.9.0rc4 options had a 'snd_' prefix. This was removed. | |||
1202 | 1257 | ||
1203 | The power-management is supported. | 1258 | The power-management is supported. |
1204 | 1259 | ||
1260 | Module snd-riptide | ||
1261 | ------------------ | ||
1262 | |||
1263 | Module for Conexant Riptide chip | ||
1264 | |||
1265 | joystick_port - Joystick port # (default: 0x200) | ||
1266 | mpu_port - MPU401 port # (default: 0x330) | ||
1267 | opl3_port - OPL3 port # (default: 0x388) | ||
1268 | |||
1269 | This module supports multiple cards. | ||
1270 | The driver requires the firmware loader support on kernel. | ||
1271 | You need to install the firmware file "riptide.hex" to the standard | ||
1272 | firmware path (e.g. /lib/firmware). | ||
1273 | |||
1205 | Module snd-rme32 | 1274 | Module snd-rme32 |
1206 | ---------------- | 1275 | ---------------- |
1207 | 1276 | ||
diff --git a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl index 6feef9e82b63..68eeebc17ff4 100644 --- a/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl +++ b/Documentation/sound/alsa/DocBook/writing-an-alsa-driver.tmpl | |||
@@ -1123,8 +1123,8 @@ | |||
1123 | if ((err = pci_enable_device(pci)) < 0) | 1123 | if ((err = pci_enable_device(pci)) < 0) |
1124 | return err; | 1124 | return err; |
1125 | /* check PCI availability (28bit DMA) */ | 1125 | /* check PCI availability (28bit DMA) */ |
1126 | if (pci_set_dma_mask(pci, 0x0fffffff) < 0 || | 1126 | if (pci_set_dma_mask(pci, DMA_28BIT_MASK) < 0 || |
1127 | pci_set_consistent_dma_mask(pci, 0x0fffffff) < 0) { | 1127 | pci_set_consistent_dma_mask(pci, DMA_28BIT_MASK) < 0) { |
1128 | printk(KERN_ERR "error to set 28bit mask DMA\n"); | 1128 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
1129 | pci_disable_device(pci); | 1129 | pci_disable_device(pci); |
1130 | return -ENXIO; | 1130 | return -ENXIO; |
@@ -1216,7 +1216,7 @@ | |||
1216 | The allocation of PCI resources is done in the | 1216 | The allocation of PCI resources is done in the |
1217 | <function>probe()</function> function, and usually an extra | 1217 | <function>probe()</function> function, and usually an extra |
1218 | <function>xxx_create()</function> function is written for this | 1218 | <function>xxx_create()</function> function is written for this |
1219 | purpose. | 1219 | purpose. |
1220 | </para> | 1220 | </para> |
1221 | 1221 | ||
1222 | <para> | 1222 | <para> |
@@ -1225,7 +1225,7 @@ | |||
1225 | allocating resources. Also, you need to set the proper PCI DMA | 1225 | allocating resources. Also, you need to set the proper PCI DMA |
1226 | mask to limit the accessed i/o range. In some cases, you might | 1226 | mask to limit the accessed i/o range. In some cases, you might |
1227 | need to call <function>pci_set_master()</function> function, | 1227 | need to call <function>pci_set_master()</function> function, |
1228 | too. | 1228 | too. |
1229 | </para> | 1229 | </para> |
1230 | 1230 | ||
1231 | <para> | 1231 | <para> |
@@ -1236,8 +1236,8 @@ | |||
1236 | <![CDATA[ | 1236 | <![CDATA[ |
1237 | if ((err = pci_enable_device(pci)) < 0) | 1237 | if ((err = pci_enable_device(pci)) < 0) |
1238 | return err; | 1238 | return err; |
1239 | if (pci_set_dma_mask(pci, 0x0fffffff) < 0 || | 1239 | if (pci_set_dma_mask(pci, DMA_28BIT_MASK) < 0 || |
1240 | pci_set_consistent_dma_mask(pci, 0x0fffffff) < 0) { | 1240 | pci_set_consistent_dma_mask(pci, DMA_28BIT_MASK) < 0) { |
1241 | printk(KERN_ERR "error to set 28bit mask DMA\n"); | 1241 | printk(KERN_ERR "error to set 28bit mask DMA\n"); |
1242 | pci_disable_device(pci); | 1242 | pci_disable_device(pci); |
1243 | return -ENXIO; | 1243 | return -ENXIO; |
@@ -1256,13 +1256,13 @@ | |||
1256 | functions. Unlike ALSA ver.0.5.x., there are no helpers for | 1256 | functions. Unlike ALSA ver.0.5.x., there are no helpers for |
1257 | that. And these resources must be released in the destructor | 1257 | that. And these resources must be released in the destructor |
1258 | function (see below). Also, on ALSA 0.9.x, you don't need to | 1258 | function (see below). Also, on ALSA 0.9.x, you don't need to |
1259 | allocate (pseudo-)DMA for PCI like ALSA 0.5.x. | 1259 | allocate (pseudo-)DMA for PCI like ALSA 0.5.x. |
1260 | </para> | 1260 | </para> |
1261 | 1261 | ||
1262 | <para> | 1262 | <para> |
1263 | Now assume that this PCI device has an I/O port with 8 bytes | 1263 | Now assume that this PCI device has an I/O port with 8 bytes |
1264 | and an interrupt. Then struct <structname>mychip</structname> will have the | 1264 | and an interrupt. Then struct <structname>mychip</structname> will have the |
1265 | following fields: | 1265 | following fields: |
1266 | 1266 | ||
1267 | <informalexample> | 1267 | <informalexample> |
1268 | <programlisting> | 1268 | <programlisting> |
diff --git a/Documentation/video4linux/CARDLIST.saa7134 b/Documentation/video4linux/CARDLIST.saa7134 index 8c7195455963..bca50903233f 100644 --- a/Documentation/video4linux/CARDLIST.saa7134 +++ b/Documentation/video4linux/CARDLIST.saa7134 | |||
@@ -52,7 +52,7 @@ | |||
52 | 51 -> ProVideo PV952 [1540:9524] | 52 | 51 -> ProVideo PV952 [1540:9524] |
53 | 52 -> AverMedia AverTV/305 [1461:2108] | 53 | 52 -> AverMedia AverTV/305 [1461:2108] |
54 | 53 -> ASUS TV-FM 7135 [1043:4845] | 54 | 53 -> ASUS TV-FM 7135 [1043:4845] |
55 | 54 -> LifeView FlyTV Platinum FM [5168:0214,1489:0214] | 55 | 54 -> LifeView FlyTV Platinum FM / Gold [5168:0214,1489:0214,5168:0304] |
56 | 55 -> LifeView FlyDVB-T DUO [5168:0306] | 56 | 55 -> LifeView FlyDVB-T DUO [5168:0306] |
57 | 56 -> Avermedia AVerTV 307 [1461:a70a] | 57 | 56 -> Avermedia AVerTV 307 [1461:a70a] |
58 | 57 -> Avermedia AVerTV GO 007 FM [1461:f31f] | 58 | 57 -> Avermedia AVerTV GO 007 FM [1461:f31f] |
@@ -84,7 +84,7 @@ | |||
84 | 83 -> Terratec Cinergy 250 PCI TV [153b:1160] | 84 | 83 -> Terratec Cinergy 250 PCI TV [153b:1160] |
85 | 84 -> LifeView FlyDVB Trio [5168:0319] | 85 | 84 -> LifeView FlyDVB Trio [5168:0319] |
86 | 85 -> AverTV DVB-T 777 [1461:2c05] | 86 | 85 -> AverTV DVB-T 777 [1461:2c05] |
87 | 86 -> LifeView FlyDVB-T [5168:0301] | 87 | 86 -> LifeView FlyDVB-T / Genius VideoWonder DVB-T [5168:0301,1489:0301] |
88 | 87 -> ADS Instant TV Duo Cardbus PTV331 [0331:1421] | 88 | 87 -> ADS Instant TV Duo Cardbus PTV331 [0331:1421] |
89 | 88 -> Tevion/KWorld DVB-T 220RF [17de:7201] | 89 | 88 -> Tevion/KWorld DVB-T 220RF [17de:7201] |
90 | 89 -> ELSA EX-VISION 700TV [1048:226c] | 90 | 89 -> ELSA EX-VISION 700TV [1048:226c] |
@@ -92,3 +92,4 @@ | |||
92 | 91 -> AVerMedia A169 B [1461:7360] | 92 | 91 -> AVerMedia A169 B [1461:7360] |
93 | 92 -> AVerMedia A169 B1 [1461:6360] | 93 | 92 -> AVerMedia A169 B1 [1461:6360] |
94 | 93 -> Medion 7134 Bridge #2 [16be:0005] | 94 | 93 -> Medion 7134 Bridge #2 [16be:0005] |
95 | 94 -> LifeView FlyDVB-T Hybrid Cardbus [5168:3306,5168:3502] | ||
diff --git a/Documentation/usb/et61x251.txt b/Documentation/video4linux/et61x251.txt index 29340282ab5f..29340282ab5f 100644 --- a/Documentation/usb/et61x251.txt +++ b/Documentation/video4linux/et61x251.txt | |||
diff --git a/Documentation/usb/ibmcam.txt b/Documentation/video4linux/ibmcam.txt index c25003644131..4a40a2e99451 100644 --- a/Documentation/usb/ibmcam.txt +++ b/Documentation/video4linux/ibmcam.txt | |||
@@ -122,7 +122,7 @@ WHAT YOU NEED: | |||
122 | - A Linux box with USB support (2.3/2.4; 2.2 w/backport may work) | 122 | - A Linux box with USB support (2.3/2.4; 2.2 w/backport may work) |
123 | 123 | ||
124 | - A Video4Linux compatible frame grabber program such as xawtv. | 124 | - A Video4Linux compatible frame grabber program such as xawtv. |
125 | 125 | ||
126 | HOW TO COMPILE THE DRIVER: | 126 | HOW TO COMPILE THE DRIVER: |
127 | 127 | ||
128 | You need to compile the driver only if you are a developer | 128 | You need to compile the driver only if you are a developer |
diff --git a/Documentation/usb/ov511.txt b/Documentation/video4linux/ov511.txt index a7fc0432bff1..142741e3c578 100644 --- a/Documentation/usb/ov511.txt +++ b/Documentation/video4linux/ov511.txt | |||
@@ -9,7 +9,7 @@ INTRODUCTION: | |||
9 | 9 | ||
10 | This is a driver for the OV511, a USB-only chip used in many "webcam" devices. | 10 | This is a driver for the OV511, a USB-only chip used in many "webcam" devices. |
11 | Any camera using the OV511/OV511+ and the OV6620/OV7610/20/20AE should work. | 11 | Any camera using the OV511/OV511+ and the OV6620/OV7610/20/20AE should work. |
12 | Video capture devices that use the Philips SAA7111A decoder also work. It | 12 | Video capture devices that use the Philips SAA7111A decoder also work. It |
13 | supports streaming and capture of color or monochrome video via the Video4Linux | 13 | supports streaming and capture of color or monochrome video via the Video4Linux |
14 | API. Most V4L apps are compatible with it. Most resolutions with a width and | 14 | API. Most V4L apps are compatible with it. Most resolutions with a width and |
15 | height that are a multiple of 8 are supported. | 15 | height that are a multiple of 8 are supported. |
@@ -52,15 +52,15 @@ from it: | |||
52 | 52 | ||
53 | chmod 666 /dev/video | 53 | chmod 666 /dev/video |
54 | chmod 666 /dev/video0 (if necessary) | 54 | chmod 666 /dev/video0 (if necessary) |
55 | 55 | ||
56 | Now you are ready to run a video app! Both vidcat and xawtv work well for me | 56 | Now you are ready to run a video app! Both vidcat and xawtv work well for me |
57 | at 640x480. | 57 | at 640x480. |
58 | 58 | ||
59 | [Using vidcat:] | 59 | [Using vidcat:] |
60 | 60 | ||
61 | vidcat -s 640x480 -p c > test.jpg | 61 | vidcat -s 640x480 -p c > test.jpg |
62 | xview test.jpg | 62 | xview test.jpg |
63 | 63 | ||
64 | [Using xawtv:] | 64 | [Using xawtv:] |
65 | 65 | ||
66 | From the main xawtv directory: | 66 | From the main xawtv directory: |
@@ -70,7 +70,7 @@ From the main xawtv directory: | |||
70 | make | 70 | make |
71 | make install | 71 | make install |
72 | 72 | ||
73 | Now you should be able to run xawtv. Right click for the options dialog. | 73 | Now you should be able to run xawtv. Right click for the options dialog. |
74 | 74 | ||
75 | MODULE PARAMETERS: | 75 | MODULE PARAMETERS: |
76 | 76 | ||
@@ -286,4 +286,3 @@ Randy Dunlap, and others. Big thanks to them for their pioneering work on that | |||
286 | and the USB stack. Thanks to Bret Wallach for getting camera reg IO, ISOC, and | 286 | and the USB stack. Thanks to Bret Wallach for getting camera reg IO, ISOC, and |
287 | image capture working. Thanks to Orion Sky Lawlor, Kevin Moore, and Claudio | 287 | image capture working. Thanks to Orion Sky Lawlor, Kevin Moore, and Claudio |
288 | Matsuoka for their work as well. | 288 | Matsuoka for their work as well. |
289 | |||
diff --git a/Documentation/usb/se401.txt b/Documentation/video4linux/se401.txt index 7b9d1c960a10..7b9d1c960a10 100644 --- a/Documentation/usb/se401.txt +++ b/Documentation/video4linux/se401.txt | |||
diff --git a/Documentation/usb/sn9c102.txt b/Documentation/video4linux/sn9c102.txt index b957beae5607..142920bc011f 100644 --- a/Documentation/usb/sn9c102.txt +++ b/Documentation/video4linux/sn9c102.txt | |||
@@ -174,7 +174,7 @@ Module parameters are listed below: | |||
174 | ------------------------------------------------------------------------------- | 174 | ------------------------------------------------------------------------------- |
175 | Name: video_nr | 175 | Name: video_nr |
176 | Type: short array (min = 0, max = 64) | 176 | Type: short array (min = 0, max = 64) |
177 | Syntax: <-1|n[,...]> | 177 | Syntax: <-1|n[,...]> |
178 | Description: Specify V4L2 minor mode number: | 178 | Description: Specify V4L2 minor mode number: |
179 | -1 = use next available | 179 | -1 = use next available |
180 | n = use minor number n | 180 | n = use minor number n |
@@ -187,7 +187,7 @@ Default: -1 | |||
187 | ------------------------------------------------------------------------------- | 187 | ------------------------------------------------------------------------------- |
188 | Name: force_munmap | 188 | Name: force_munmap |
189 | Type: bool array (min = 0, max = 64) | 189 | Type: bool array (min = 0, max = 64) |
190 | Syntax: <0|1[,...]> | 190 | Syntax: <0|1[,...]> |
191 | Description: Force the application to unmap previously mapped buffer memory | 191 | Description: Force the application to unmap previously mapped buffer memory |
192 | before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not | 192 | before calling any VIDIOC_S_CROP or VIDIOC_S_FMT ioctl's. Not |
193 | all the applications support this feature. This parameter is | 193 | all the applications support this feature. This parameter is |
@@ -206,7 +206,7 @@ Default: 2 | |||
206 | ------------------------------------------------------------------------------- | 206 | ------------------------------------------------------------------------------- |
207 | Name: debug | 207 | Name: debug |
208 | Type: ushort | 208 | Type: ushort |
209 | Syntax: <n> | 209 | Syntax: <n> |
210 | Description: Debugging information level, from 0 to 3: | 210 | Description: Debugging information level, from 0 to 3: |
211 | 0 = none (use carefully) | 211 | 0 = none (use carefully) |
212 | 1 = critical errors | 212 | 1 = critical errors |
@@ -267,7 +267,7 @@ The sysfs interface also provides the "frame_header" entry, which exports the | |||
267 | frame header of the most recent requested and captured video frame. The header | 267 | frame header of the most recent requested and captured video frame. The header |
268 | is always 18-bytes long and is appended to every video frame by the SN9C10x | 268 | is always 18-bytes long and is appended to every video frame by the SN9C10x |
269 | controllers. As an example, this additional information can be used by the user | 269 | controllers. As an example, this additional information can be used by the user |
270 | application for implementing auto-exposure features via software. | 270 | application for implementing auto-exposure features via software. |
271 | 271 | ||
272 | The following table describes the frame header: | 272 | The following table describes the frame header: |
273 | 273 | ||
@@ -441,7 +441,7 @@ blue pixels in one video frame. Each pixel is associated with a 8-bit long | |||
441 | value and is disposed in memory according to the pattern shown below: | 441 | value and is disposed in memory according to the pattern shown below: |
442 | 442 | ||
443 | B[0] G[1] B[2] G[3] ... B[m-2] G[m-1] | 443 | B[0] G[1] B[2] G[3] ... B[m-2] G[m-1] |
444 | G[m] R[m+1] G[m+2] R[m+2] ... G[2m-2] R[2m-1] | 444 | G[m] R[m+1] G[m+2] R[m+2] ... G[2m-2] R[2m-1] |
445 | ... | 445 | ... |
446 | ... B[(n-1)(m-2)] G[(n-1)(m-1)] | 446 | ... B[(n-1)(m-2)] G[(n-1)(m-1)] |
447 | ... G[n(m-2)] R[n(m-1)] | 447 | ... G[n(m-2)] R[n(m-1)] |
@@ -472,12 +472,12 @@ The pixel reference value is calculated as follows: | |||
472 | The algorithm purely describes the conversion from compressed Bayer code used | 472 | The algorithm purely describes the conversion from compressed Bayer code used |
473 | in the SN9C10x chips to uncompressed Bayer. Additional steps are required to | 473 | in the SN9C10x chips to uncompressed Bayer. Additional steps are required to |
474 | convert this to a color image (i.e. a color interpolation algorithm). | 474 | convert this to a color image (i.e. a color interpolation algorithm). |
475 | 475 | ||
476 | The following Huffman codes have been found: | 476 | The following Huffman codes have been found: |
477 | 0: +0 (relative to reference pixel value) | 477 | 0: +0 (relative to reference pixel value) |
478 | 100: +4 | 478 | 100: +4 |
479 | 101: -4? | 479 | 101: -4? |
480 | 1110xxxx: set absolute value to xxxx.0000 | 480 | 1110xxxx: set absolute value to xxxx.0000 |
481 | 1101: +11 | 481 | 1101: +11 |
482 | 1111: -11 | 482 | 1111: -11 |
483 | 11001: +20 | 483 | 11001: +20 |
diff --git a/Documentation/usb/stv680.txt b/Documentation/video4linux/stv680.txt index 6448041e7a37..4f8946f32f51 100644 --- a/Documentation/usb/stv680.txt +++ b/Documentation/video4linux/stv680.txt | |||
@@ -5,15 +5,15 @@ Copyright, 2001, Kevin Sisson | |||
5 | 5 | ||
6 | INTRODUCTION: | 6 | INTRODUCTION: |
7 | 7 | ||
8 | STMicroelectronics produces the STV0680B chip, which comes in two | 8 | STMicroelectronics produces the STV0680B chip, which comes in two |
9 | types, -001 and -003. The -003 version allows the recording and downloading | 9 | types, -001 and -003. The -003 version allows the recording and downloading |
10 | of sound clips from the camera, and allows a flash attachment. Otherwise, | 10 | of sound clips from the camera, and allows a flash attachment. Otherwise, |
11 | it uses the same commands as the -001 version. Both versions support a | 11 | it uses the same commands as the -001 version. Both versions support a |
12 | variety of SDRAM sizes and sensors, allowing for a maximum of 26 VGA or 20 | 12 | variety of SDRAM sizes and sensors, allowing for a maximum of 26 VGA or 20 |
13 | CIF pictures. The STV0680 supports either a serial or a usb interface, and | 13 | CIF pictures. The STV0680 supports either a serial or a usb interface, and |
14 | video is possible through the usb interface. | 14 | video is possible through the usb interface. |
15 | 15 | ||
16 | The following cameras are known to work with this driver, although any | 16 | The following cameras are known to work with this driver, although any |
17 | camera with Vendor/Product codes of 0553/0202 should work: | 17 | camera with Vendor/Product codes of 0553/0202 should work: |
18 | 18 | ||
19 | Aiptek Pencam (various models) | 19 | Aiptek Pencam (various models) |
@@ -34,15 +34,15 @@ http://www.linux-usb.org | |||
34 | MODULE OPTIONS: | 34 | MODULE OPTIONS: |
35 | 35 | ||
36 | When the driver is compiled as a module, you can set a "swapRGB=1" | 36 | When the driver is compiled as a module, you can set a "swapRGB=1" |
37 | option, if necessary, for those applications that require it | 37 | option, if necessary, for those applications that require it |
38 | (such as xawtv). However, the driver should detect and set this | 38 | (such as xawtv). However, the driver should detect and set this |
39 | automatically, so this option should not normally be used. | 39 | automatically, so this option should not normally be used. |
40 | 40 | ||
41 | 41 | ||
42 | KNOWN PROBLEMS: | 42 | KNOWN PROBLEMS: |
43 | 43 | ||
44 | The driver seems to work better with the usb-ohci than the usb-uhci host | 44 | The driver seems to work better with the usb-ohci than the usb-uhci host |
45 | controller driver. | 45 | controller driver. |
46 | 46 | ||
47 | HELP: | 47 | HELP: |
48 | 48 | ||
@@ -50,6 +50,4 @@ The latest info on this driver can be found at: | |||
50 | http://personal.clt.bellsouth.net/~kjsisson or at | 50 | http://personal.clt.bellsouth.net/~kjsisson or at |
51 | http://stv0680-usb.sourceforge.net | 51 | http://stv0680-usb.sourceforge.net |
52 | 52 | ||
53 | Any questions to me can be send to: kjsisson@bellsouth.net | 53 | Any questions to me can be send to: kjsisson@bellsouth.net \ No newline at end of file |
54 | |||
55 | |||
diff --git a/Documentation/usb/w9968cf.txt b/Documentation/video4linux/w9968cf.txt index 9d46cd0b19e3..3b704f2aae6d 100644 --- a/Documentation/usb/w9968cf.txt +++ b/Documentation/video4linux/w9968cf.txt | |||
@@ -1,5 +1,5 @@ | |||
1 | 1 | ||
2 | W996[87]CF JPEG USB Dual Mode Camera Chip | 2 | W996[87]CF JPEG USB Dual Mode Camera Chip |
3 | Driver for Linux 2.6 (basic version) | 3 | Driver for Linux 2.6 (basic version) |
4 | ========================================= | 4 | ========================================= |
5 | 5 | ||
@@ -115,7 +115,7 @@ additional testing and full support, would be much appreciated. | |||
115 | ====================== | 115 | ====================== |
116 | For it to work properly, the driver needs kernel support for Video4Linux, USB | 116 | For it to work properly, the driver needs kernel support for Video4Linux, USB |
117 | and I2C, and the "ovcamchip" module for the image sensor. Make sure you are not | 117 | and I2C, and the "ovcamchip" module for the image sensor. Make sure you are not |
118 | actually using any external "ovcamchip" module, given that the W996[87]CF | 118 | actually using any external "ovcamchip" module, given that the W996[87]CF |
119 | driver depends on the version of the module present in the official kernels. | 119 | driver depends on the version of the module present in the official kernels. |
120 | 120 | ||
121 | The following options of the kernel configuration file must be enabled and | 121 | The following options of the kernel configuration file must be enabled and |
@@ -197,16 +197,16 @@ Note: The kernel must be compiled with the CONFIG_KMOD option | |||
197 | enabled for the 'ovcamchip' module to be loaded and for | 197 | enabled for the 'ovcamchip' module to be loaded and for |
198 | this parameter to be present. | 198 | this parameter to be present. |
199 | ------------------------------------------------------------------------------- | 199 | ------------------------------------------------------------------------------- |
200 | Name: simcams | 200 | Name: simcams |
201 | Type: int | 201 | Type: int |
202 | Syntax: <n> | 202 | Syntax: <n> |
203 | Description: Number of cameras allowed to stream simultaneously. | 203 | Description: Number of cameras allowed to stream simultaneously. |
204 | n may vary from 0 to 32. | 204 | n may vary from 0 to 32. |
205 | Default: 32 | 205 | Default: 32 |
206 | ------------------------------------------------------------------------------- | 206 | ------------------------------------------------------------------------------- |
207 | Name: video_nr | 207 | Name: video_nr |
208 | Type: int array (min = 0, max = 32) | 208 | Type: int array (min = 0, max = 32) |
209 | Syntax: <-1|n[,...]> | 209 | Syntax: <-1|n[,...]> |
210 | Description: Specify V4L minor mode number. | 210 | Description: Specify V4L minor mode number. |
211 | -1 = use next available | 211 | -1 = use next available |
212 | n = use minor number n | 212 | n = use minor number n |
@@ -219,7 +219,7 @@ Default: -1 | |||
219 | ------------------------------------------------------------------------------- | 219 | ------------------------------------------------------------------------------- |
220 | Name: packet_size | 220 | Name: packet_size |
221 | Type: int array (min = 0, max = 32) | 221 | Type: int array (min = 0, max = 32) |
222 | Syntax: <n[,...]> | 222 | Syntax: <n[,...]> |
223 | Description: Specify the maximum data payload size in bytes for alternate | 223 | Description: Specify the maximum data payload size in bytes for alternate |
224 | settings, for each device. n is scaled between 63 and 1023. | 224 | settings, for each device. n is scaled between 63 and 1023. |
225 | Default: 1023 | 225 | Default: 1023 |
@@ -234,7 +234,7 @@ Default: 2 | |||
234 | ------------------------------------------------------------------------------- | 234 | ------------------------------------------------------------------------------- |
235 | Name: double_buffer | 235 | Name: double_buffer |
236 | Type: bool array (min = 0, max = 32) | 236 | Type: bool array (min = 0, max = 32) |
237 | Syntax: <0|1[,...]> | 237 | Syntax: <0|1[,...]> |
238 | Description: Hardware double buffering: 0 disabled, 1 enabled. | 238 | Description: Hardware double buffering: 0 disabled, 1 enabled. |
239 | It should be enabled if you want smooth video output: if you | 239 | It should be enabled if you want smooth video output: if you |
240 | obtain out of sync. video, disable it, or try to | 240 | obtain out of sync. video, disable it, or try to |
@@ -243,13 +243,13 @@ Default: 1 for every device. | |||
243 | ------------------------------------------------------------------------------- | 243 | ------------------------------------------------------------------------------- |
244 | Name: clamping | 244 | Name: clamping |
245 | Type: bool array (min = 0, max = 32) | 245 | Type: bool array (min = 0, max = 32) |
246 | Syntax: <0|1[,...]> | 246 | Syntax: <0|1[,...]> |
247 | Description: Video data clamping: 0 disabled, 1 enabled. | 247 | Description: Video data clamping: 0 disabled, 1 enabled. |
248 | Default: 0 for every device. | 248 | Default: 0 for every device. |
249 | ------------------------------------------------------------------------------- | 249 | ------------------------------------------------------------------------------- |
250 | Name: filter_type | 250 | Name: filter_type |
251 | Type: int array (min = 0, max = 32) | 251 | Type: int array (min = 0, max = 32) |
252 | Syntax: <0|1|2[,...]> | 252 | Syntax: <0|1|2[,...]> |
253 | Description: Video filter type. | 253 | Description: Video filter type. |
254 | 0 none, 1 (1-2-1) 3-tap filter, 2 (2-3-6-3-2) 5-tap filter. | 254 | 0 none, 1 (1-2-1) 3-tap filter, 2 (2-3-6-3-2) 5-tap filter. |
255 | The filter is used to reduce noise and aliasing artifacts | 255 | The filter is used to reduce noise and aliasing artifacts |
@@ -258,13 +258,13 @@ Default: 0 for every device. | |||
258 | ------------------------------------------------------------------------------- | 258 | ------------------------------------------------------------------------------- |
259 | Name: largeview | 259 | Name: largeview |
260 | Type: bool array (min = 0, max = 32) | 260 | Type: bool array (min = 0, max = 32) |
261 | Syntax: <0|1[,...]> | 261 | Syntax: <0|1[,...]> |
262 | Description: Large view: 0 disabled, 1 enabled. | 262 | Description: Large view: 0 disabled, 1 enabled. |
263 | Default: 1 for every device. | 263 | Default: 1 for every device. |
264 | ------------------------------------------------------------------------------- | 264 | ------------------------------------------------------------------------------- |
265 | Name: upscaling | 265 | Name: upscaling |
266 | Type: bool array (min = 0, max = 32) | 266 | Type: bool array (min = 0, max = 32) |
267 | Syntax: <0|1[,...]> | 267 | Syntax: <0|1[,...]> |
268 | Description: Software scaling (for non-compressed video only): | 268 | Description: Software scaling (for non-compressed video only): |
269 | 0 disabled, 1 enabled. | 269 | 0 disabled, 1 enabled. |
270 | Disable it if you have a slow CPU or you don't have enough | 270 | Disable it if you have a slow CPU or you don't have enough |
@@ -341,8 +341,8 @@ Default: 50 for every device. | |||
341 | ------------------------------------------------------------------------------- | 341 | ------------------------------------------------------------------------------- |
342 | Name: bandingfilter | 342 | Name: bandingfilter |
343 | Type: bool array (min = 0, max = 32) | 343 | Type: bool array (min = 0, max = 32) |
344 | Syntax: <0|1[,...]> | 344 | Syntax: <0|1[,...]> |
345 | Description: Banding filter to reduce effects of fluorescent | 345 | Description: Banding filter to reduce effects of fluorescent |
346 | lighting: | 346 | lighting: |
347 | 0 disabled, 1 enabled. | 347 | 0 disabled, 1 enabled. |
348 | This filter tries to reduce the pattern of horizontal | 348 | This filter tries to reduce the pattern of horizontal |
@@ -374,7 +374,7 @@ Default: 0 for every device. | |||
374 | ------------------------------------------------------------------------------- | 374 | ------------------------------------------------------------------------------- |
375 | Name: monochrome | 375 | Name: monochrome |
376 | Type: bool array (min = 0, max = 32) | 376 | Type: bool array (min = 0, max = 32) |
377 | Syntax: <0|1[,...]> | 377 | Syntax: <0|1[,...]> |
378 | Description: The image sensor is monochrome: | 378 | Description: The image sensor is monochrome: |
379 | 0 = no, 1 = yes | 379 | 0 = no, 1 = yes |
380 | Default: 0 for every device. | 380 | Default: 0 for every device. |
@@ -400,19 +400,19 @@ Default: 32768 for every device. | |||
400 | ------------------------------------------------------------------------------- | 400 | ------------------------------------------------------------------------------- |
401 | Name: contrast | 401 | Name: contrast |
402 | Type: long array (min = 0, max = 32) | 402 | Type: long array (min = 0, max = 32) |
403 | Syntax: <n[,...]> | 403 | Syntax: <n[,...]> |
404 | Description: Set picture contrast (0-65535). | 404 | Description: Set picture contrast (0-65535). |
405 | Default: 50000 for every device. | 405 | Default: 50000 for every device. |
406 | ------------------------------------------------------------------------------- | 406 | ------------------------------------------------------------------------------- |
407 | Name: whiteness | 407 | Name: whiteness |
408 | Type: long array (min = 0, max = 32) | 408 | Type: long array (min = 0, max = 32) |
409 | Syntax: <n[,...]> | 409 | Syntax: <n[,...]> |
410 | Description: Set picture whiteness (0-65535). | 410 | Description: Set picture whiteness (0-65535). |
411 | Default: 32768 for every device. | 411 | Default: 32768 for every device. |
412 | ------------------------------------------------------------------------------- | 412 | ------------------------------------------------------------------------------- |
413 | Name: debug | 413 | Name: debug |
414 | Type: int | 414 | Type: int |
415 | Syntax: <n> | 415 | Syntax: <n> |
416 | Description: Debugging information level, from 0 to 6: | 416 | Description: Debugging information level, from 0 to 6: |
417 | 0 = none (use carefully) | 417 | 0 = none (use carefully) |
418 | 1 = critical errors | 418 | 1 = critical errors |
diff --git a/Documentation/usb/zc0301.txt b/Documentation/video4linux/zc0301.txt index f55262c6733b..f55262c6733b 100644 --- a/Documentation/usb/zc0301.txt +++ b/Documentation/video4linux/zc0301.txt | |||
diff --git a/Documentation/vm/hugetlbpage.txt b/Documentation/vm/hugetlbpage.txt index 1ad9af1ca4d0..2803f63c1a27 100644 --- a/Documentation/vm/hugetlbpage.txt +++ b/Documentation/vm/hugetlbpage.txt | |||
@@ -27,7 +27,7 @@ number of free hugetlb pages at any time. It also displays information about | |||
27 | the configured hugepage size - this is needed for generating the proper | 27 | the configured hugepage size - this is needed for generating the proper |
28 | alignment and size of the arguments to the above system calls. | 28 | alignment and size of the arguments to the above system calls. |
29 | 29 | ||
30 | The output of "cat /proc/meminfo" will have output like: | 30 | The output of "cat /proc/meminfo" will have lines like: |
31 | 31 | ||
32 | ..... | 32 | ..... |
33 | HugePages_Total: xxx | 33 | HugePages_Total: xxx |
@@ -42,11 +42,11 @@ pages in the kernel. Super user can dynamically request more (or free some | |||
42 | pre-configured) hugepages. | 42 | pre-configured) hugepages. |
43 | The allocation (or deallocation) of hugetlb pages is possible only if there are | 43 | The allocation (or deallocation) of hugetlb pages is possible only if there are |
44 | enough physically contiguous free pages in system (freeing of hugepages is | 44 | enough physically contiguous free pages in system (freeing of hugepages is |
45 | possible only if there are enough hugetlb pages free that can be transfered | 45 | possible only if there are enough hugetlb pages free that can be transferred |
46 | back to regular memory pool). | 46 | back to regular memory pool). |
47 | 47 | ||
48 | Pages that are used as hugetlb pages are reserved inside the kernel and can | 48 | Pages that are used as hugetlb pages are reserved inside the kernel and cannot |
49 | not be used for other purposes. | 49 | be used for other purposes. |
50 | 50 | ||
51 | Once the kernel with Hugetlb page support is built and running, a user can | 51 | Once the kernel with Hugetlb page support is built and running, a user can |
52 | use either the mmap system call or shared memory system calls to start using | 52 | use either the mmap system call or shared memory system calls to start using |
@@ -60,7 +60,7 @@ Use the following command to dynamically allocate/deallocate hugepages: | |||
60 | This command will try to configure 20 hugepages in the system. The success | 60 | This command will try to configure 20 hugepages in the system. The success |
61 | or failure of allocation depends on the amount of physically contiguous | 61 | or failure of allocation depends on the amount of physically contiguous |
62 | memory that is preset in system at this time. System administrators may want | 62 | memory that is preset in system at this time. System administrators may want |
63 | to put this command in one of the local rc init file. This will enable the | 63 | to put this command in one of the local rc init files. This will enable the |
64 | kernel to request huge pages early in the boot process (when the possibility | 64 | kernel to request huge pages early in the boot process (when the possibility |
65 | of getting physical contiguous pages is still very high). | 65 | of getting physical contiguous pages is still very high). |
66 | 66 | ||
@@ -78,8 +78,8 @@ the uid and gid of the current process are taken. The mode option sets the | |||
78 | mode of root of file system to value & 0777. This value is given in octal. | 78 | mode of root of file system to value & 0777. This value is given in octal. |
79 | By default the value 0755 is picked. The size option sets the maximum value of | 79 | By default the value 0755 is picked. The size option sets the maximum value of |
80 | memory (huge pages) allowed for that filesystem (/mnt/huge). The size is | 80 | memory (huge pages) allowed for that filesystem (/mnt/huge). The size is |
81 | rounded down to HPAGE_SIZE. The option nr_inode sets the maximum number of | 81 | rounded down to HPAGE_SIZE. The option nr_inodes sets the maximum number of |
82 | inodes that /mnt/huge can use. If the size or nr_inode options are not | 82 | inodes that /mnt/huge can use. If the size or nr_inodes options are not |
83 | provided on command line then no limits are set. For size and nr_inodes | 83 | provided on command line then no limits are set. For size and nr_inodes |
84 | options, you can use [G|g]/[M|m]/[K|k] to represent giga/mega/kilo. For | 84 | options, you can use [G|g]/[M|m]/[K|k] to represent giga/mega/kilo. For |
85 | example, size=2K has the same meaning as size=2048. An example is given at | 85 | example, size=2K has the same meaning as size=2048. An example is given at |
@@ -88,7 +88,7 @@ the end of this document. | |||
88 | read and write system calls are not supported on files that reside on hugetlb | 88 | read and write system calls are not supported on files that reside on hugetlb |
89 | file systems. | 89 | file systems. |
90 | 90 | ||
91 | A regular chown, chgrp and chmod commands (with right permissions) could be | 91 | Regular chown, chgrp, and chmod commands (with right permissions) could be |
92 | used to change the file attributes on hugetlbfs. | 92 | used to change the file attributes on hugetlbfs. |
93 | 93 | ||
94 | Also, it is important to note that no such mount command is required if the | 94 | Also, it is important to note that no such mount command is required if the |
@@ -96,8 +96,8 @@ applications are going to use only shmat/shmget system calls. Users who | |||
96 | wish to use hugetlb page via shared memory segment should be a member of | 96 | wish to use hugetlb page via shared memory segment should be a member of |
97 | a supplementary group and system admin needs to configure that gid into | 97 | a supplementary group and system admin needs to configure that gid into |
98 | /proc/sys/vm/hugetlb_shm_group. It is possible for same or different | 98 | /proc/sys/vm/hugetlb_shm_group. It is possible for same or different |
99 | applications to use any combination of mmaps and shm* calls. Though the | 99 | applications to use any combination of mmaps and shm* calls, though the |
100 | mount of filesystem will be required for using mmaps. | 100 | mount of filesystem will be required for using mmap calls. |
101 | 101 | ||
102 | ******************************************************************* | 102 | ******************************************************************* |
103 | 103 | ||
diff --git a/Documentation/x86_64/boot-options.txt b/Documentation/x86_64/boot-options.txt index 1921353259ae..f2cd6ef53ff3 100644 --- a/Documentation/x86_64/boot-options.txt +++ b/Documentation/x86_64/boot-options.txt | |||
@@ -151,6 +151,11 @@ NUMA | |||
151 | 151 | ||
152 | numa=fake=X Fake X nodes and ignore NUMA setup of the actual machine. | 152 | numa=fake=X Fake X nodes and ignore NUMA setup of the actual machine. |
153 | 153 | ||
154 | numa=hotadd=percent | ||
155 | Only allow hotadd memory to preallocate page structures upto | ||
156 | percent of already available memory. | ||
157 | numa=hotadd=0 will disable hotadd memory. | ||
158 | |||
154 | ACPI | 159 | ACPI |
155 | 160 | ||
156 | acpi=off Don't enable ACPI | 161 | acpi=off Don't enable ACPI |