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-rw-r--r--fs/jbd/commit.c6
-rw-r--r--fs/jbd/journal.c88
-rw-r--r--fs/jbd/transaction.c8
3 files changed, 11 insertions, 91 deletions
diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c
index a003d50edcdb..a263d82761df 100644
--- a/fs/jbd/commit.c
+++ b/fs/jbd/commit.c
@@ -375,7 +375,7 @@ void journal_commit_transaction(journal_t *journal)
375 struct buffer_head *bh = jh2bh(jh); 375 struct buffer_head *bh = jh2bh(jh);
376 376
377 jbd_lock_bh_state(bh); 377 jbd_lock_bh_state(bh);
378 jbd_slab_free(jh->b_committed_data, bh->b_size); 378 jbd_free(jh->b_committed_data, bh->b_size);
379 jh->b_committed_data = NULL; 379 jh->b_committed_data = NULL;
380 jbd_unlock_bh_state(bh); 380 jbd_unlock_bh_state(bh);
381 } 381 }
@@ -792,14 +792,14 @@ restart_loop:
792 * Otherwise, we can just throw away the frozen data now. 792 * Otherwise, we can just throw away the frozen data now.
793 */ 793 */
794 if (jh->b_committed_data) { 794 if (jh->b_committed_data) {
795 jbd_slab_free(jh->b_committed_data, bh->b_size); 795 jbd_free(jh->b_committed_data, bh->b_size);
796 jh->b_committed_data = NULL; 796 jh->b_committed_data = NULL;
797 if (jh->b_frozen_data) { 797 if (jh->b_frozen_data) {
798 jh->b_committed_data = jh->b_frozen_data; 798 jh->b_committed_data = jh->b_frozen_data;
799 jh->b_frozen_data = NULL; 799 jh->b_frozen_data = NULL;
800 } 800 }
801 } else if (jh->b_frozen_data) { 801 } else if (jh->b_frozen_data) {
802 jbd_slab_free(jh->b_frozen_data, bh->b_size); 802 jbd_free(jh->b_frozen_data, bh->b_size);
803 jh->b_frozen_data = NULL; 803 jh->b_frozen_data = NULL;
804 } 804 }
805 805
diff --git a/fs/jbd/journal.c b/fs/jbd/journal.c
index a6be78c05dce..7edf3fdfdadd 100644
--- a/fs/jbd/journal.c
+++ b/fs/jbd/journal.c
@@ -83,7 +83,6 @@ EXPORT_SYMBOL(journal_force_commit);
83 83
84static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *); 84static int journal_convert_superblock_v1(journal_t *, journal_superblock_t *);
85static void __journal_abort_soft (journal_t *journal, int errno); 85static void __journal_abort_soft (journal_t *journal, int errno);
86static int journal_create_jbd_slab(size_t slab_size);
87 86
88/* 87/*
89 * Helper function used to manage commit timeouts 88 * Helper function used to manage commit timeouts
@@ -334,10 +333,10 @@ repeat:
334 char *tmp; 333 char *tmp;
335 334
336 jbd_unlock_bh_state(bh_in); 335 jbd_unlock_bh_state(bh_in);
337 tmp = jbd_slab_alloc(bh_in->b_size, GFP_NOFS); 336 tmp = jbd_alloc(bh_in->b_size, GFP_NOFS);
338 jbd_lock_bh_state(bh_in); 337 jbd_lock_bh_state(bh_in);
339 if (jh_in->b_frozen_data) { 338 if (jh_in->b_frozen_data) {
340 jbd_slab_free(tmp, bh_in->b_size); 339 jbd_free(tmp, bh_in->b_size);
341 goto repeat; 340 goto repeat;
342 } 341 }
343 342
@@ -1095,13 +1094,6 @@ int journal_load(journal_t *journal)
1095 } 1094 }
1096 } 1095 }
1097 1096
1098 /*
1099 * Create a slab for this blocksize
1100 */
1101 err = journal_create_jbd_slab(be32_to_cpu(sb->s_blocksize));
1102 if (err)
1103 return err;
1104
1105 /* Let the recovery code check whether it needs to recover any 1097 /* Let the recovery code check whether it needs to recover any
1106 * data from the journal. */ 1098 * data from the journal. */
1107 if (journal_recover(journal)) 1099 if (journal_recover(journal))
@@ -1624,77 +1616,6 @@ void * __jbd_kmalloc (const char *where, size_t size, gfp_t flags, int retry)
1624} 1616}
1625 1617
1626/* 1618/*
1627 * jbd slab management: create 1k, 2k, 4k, 8k slabs as needed
1628 * and allocate frozen and commit buffers from these slabs.
1629 *
1630 * Reason for doing this is to avoid, SLAB_DEBUG - since it could
1631 * cause bh to cross page boundary.
1632 */
1633
1634#define JBD_MAX_SLABS 5
1635#define JBD_SLAB_INDEX(size) (size >> 11)
1636
1637static struct kmem_cache *jbd_slab[JBD_MAX_SLABS];
1638static const char *jbd_slab_names[JBD_MAX_SLABS] = {
1639 "jbd_1k", "jbd_2k", "jbd_4k", NULL, "jbd_8k"
1640};
1641
1642static void journal_destroy_jbd_slabs(void)
1643{
1644 int i;
1645
1646 for (i = 0; i < JBD_MAX_SLABS; i++) {
1647 if (jbd_slab[i])
1648 kmem_cache_destroy(jbd_slab[i]);
1649 jbd_slab[i] = NULL;
1650 }
1651}
1652
1653static int journal_create_jbd_slab(size_t slab_size)
1654{
1655 int i = JBD_SLAB_INDEX(slab_size);
1656
1657 BUG_ON(i >= JBD_MAX_SLABS);
1658
1659 /*
1660 * Check if we already have a slab created for this size
1661 */
1662 if (jbd_slab[i])
1663 return 0;
1664
1665 /*
1666 * Create a slab and force alignment to be same as slabsize -
1667 * this will make sure that allocations won't cross the page
1668 * boundary.
1669 */
1670 jbd_slab[i] = kmem_cache_create(jbd_slab_names[i],
1671 slab_size, slab_size, 0, NULL);
1672 if (!jbd_slab[i]) {
1673 printk(KERN_EMERG "JBD: no memory for jbd_slab cache\n");
1674 return -ENOMEM;
1675 }
1676 return 0;
1677}
1678
1679void * jbd_slab_alloc(size_t size, gfp_t flags)
1680{
1681 int idx;
1682
1683 idx = JBD_SLAB_INDEX(size);
1684 BUG_ON(jbd_slab[idx] == NULL);
1685 return kmem_cache_alloc(jbd_slab[idx], flags | __GFP_NOFAIL);
1686}
1687
1688void jbd_slab_free(void *ptr, size_t size)
1689{
1690 int idx;
1691
1692 idx = JBD_SLAB_INDEX(size);
1693 BUG_ON(jbd_slab[idx] == NULL);
1694 kmem_cache_free(jbd_slab[idx], ptr);
1695}
1696
1697/*
1698 * Journal_head storage management 1619 * Journal_head storage management
1699 */ 1620 */
1700static struct kmem_cache *journal_head_cache; 1621static struct kmem_cache *journal_head_cache;
@@ -1881,13 +1802,13 @@ static void __journal_remove_journal_head(struct buffer_head *bh)
1881 printk(KERN_WARNING "%s: freeing " 1802 printk(KERN_WARNING "%s: freeing "
1882 "b_frozen_data\n", 1803 "b_frozen_data\n",
1883 __FUNCTION__); 1804 __FUNCTION__);
1884 jbd_slab_free(jh->b_frozen_data, bh->b_size); 1805 jbd_free(jh->b_frozen_data, bh->b_size);
1885 } 1806 }
1886 if (jh->b_committed_data) { 1807 if (jh->b_committed_data) {
1887 printk(KERN_WARNING "%s: freeing " 1808 printk(KERN_WARNING "%s: freeing "
1888 "b_committed_data\n", 1809 "b_committed_data\n",
1889 __FUNCTION__); 1810 __FUNCTION__);
1890 jbd_slab_free(jh->b_committed_data, bh->b_size); 1811 jbd_free(jh->b_committed_data, bh->b_size);
1891 } 1812 }
1892 bh->b_private = NULL; 1813 bh->b_private = NULL;
1893 jh->b_bh = NULL; /* debug, really */ 1814 jh->b_bh = NULL; /* debug, really */
@@ -2042,7 +1963,6 @@ static void journal_destroy_caches(void)
2042 journal_destroy_revoke_caches(); 1963 journal_destroy_revoke_caches();
2043 journal_destroy_journal_head_cache(); 1964 journal_destroy_journal_head_cache();
2044 journal_destroy_handle_cache(); 1965 journal_destroy_handle_cache();
2045 journal_destroy_jbd_slabs();
2046} 1966}
2047 1967
2048static int __init journal_init(void) 1968static int __init journal_init(void)
diff --git a/fs/jbd/transaction.c b/fs/jbd/transaction.c
index 8df5bac0b7a5..db8404514c92 100644
--- a/fs/jbd/transaction.c
+++ b/fs/jbd/transaction.c
@@ -675,7 +675,7 @@ repeat:
675 JBUFFER_TRACE(jh, "allocate memory for buffer"); 675 JBUFFER_TRACE(jh, "allocate memory for buffer");
676 jbd_unlock_bh_state(bh); 676 jbd_unlock_bh_state(bh);
677 frozen_buffer = 677 frozen_buffer =
678 jbd_slab_alloc(jh2bh(jh)->b_size, 678 jbd_alloc(jh2bh(jh)->b_size,
679 GFP_NOFS); 679 GFP_NOFS);
680 if (!frozen_buffer) { 680 if (!frozen_buffer) {
681 printk(KERN_EMERG 681 printk(KERN_EMERG
@@ -735,7 +735,7 @@ done:
735 735
736out: 736out:
737 if (unlikely(frozen_buffer)) /* It's usually NULL */ 737 if (unlikely(frozen_buffer)) /* It's usually NULL */
738 jbd_slab_free(frozen_buffer, bh->b_size); 738 jbd_free(frozen_buffer, bh->b_size);
739 739
740 JBUFFER_TRACE(jh, "exit"); 740 JBUFFER_TRACE(jh, "exit");
741 return error; 741 return error;
@@ -888,7 +888,7 @@ int journal_get_undo_access(handle_t *handle, struct buffer_head *bh)
888 888
889repeat: 889repeat:
890 if (!jh->b_committed_data) { 890 if (!jh->b_committed_data) {
891 committed_data = jbd_slab_alloc(jh2bh(jh)->b_size, GFP_NOFS); 891 committed_data = jbd_alloc(jh2bh(jh)->b_size, GFP_NOFS);
892 if (!committed_data) { 892 if (!committed_data) {
893 printk(KERN_EMERG "%s: No memory for committed data\n", 893 printk(KERN_EMERG "%s: No memory for committed data\n",
894 __FUNCTION__); 894 __FUNCTION__);
@@ -915,7 +915,7 @@ repeat:
915out: 915out:
916 journal_put_journal_head(jh); 916 journal_put_journal_head(jh);
917 if (unlikely(committed_data)) 917 if (unlikely(committed_data))
918 jbd_slab_free(committed_data, bh->b_size); 918 jbd_free(committed_data, bh->b_size);
919 return err; 919 return err;
920} 920}
921 921
generated by cgit v1.2.2 (git 2.25.0) at 2025-09-05 20:14:57 -0400
n $drive_status$, if implemented, should provide information on the status of the drive (not the status of the disc, which may or may not be in the drive). If the drive is not a changer, $slot_nr$ should be ignored. In \cdromh\ the possibilities are listed: $$ \halign{$#$\ \hfil&$/*$ \rm# $*/$\hfil\cr CDS_NO_INFO& no information available\cr CDS_NO_DISC& no disc is inserted, tray is closed\cr CDS_TRAY_OPEN& tray is opened\cr CDS_DRIVE_NOT_READY& something is wrong, tray is moving?\cr CDS_DISC_OK& a disc is loaded and everything is fine\cr } $$ \subsection{$Int\ media_changed(struct\ cdrom_device_info * cdi, int\ disc_nr)$} This function is very similar to the original function in $struct\ file_operations$. It returns 1 if the medium of the device $cdi\to dev$ has changed since the last call, and 0 otherwise. The parameter $disc_nr$ identifies a specific slot in a juke-box, it should be ignored for single-disc drives. Note that by `re-routing' this function through $cdrom_media_changed()$, we can implement separate queues for the VFS and a new $ioctl()$ function that can report device changes to software (\eg, an auto-mounting daemon). \subsection{$Int\ tray_move(struct\ cdrom_device_info * cdi, int\ position)$} This function, if implemented, should control the tray movement. (No other function should control this.) The parameter $position$ controls the desired direction of movement: \begin{itemize} \item[0] Close tray \item[1] Open tray \end{itemize} This function returns 0 upon success, and a non-zero value upon error. Note that if the tray is already in the desired position, no action need be taken, and the return value should be 0. \subsection{$Int\ lock_door(struct\ cdrom_device_info * cdi, int\ lock)$} This function (and no other code) controls locking of the door, if the drive allows this. The value of $lock$ controls the desired locking state: \begin{itemize} \item[0] Unlock door, manual opening is allowed \item[1] Lock door, tray cannot be ejected manually \end{itemize} This function returns 0 upon success, and a non-zero value upon error. Note that if the door is already in the requested state, no action need be taken, and the return value should be 0. \subsection{$Int\ select_speed(struct\ cdrom_device_info * cdi, int\ speed)$} Some \cdrom\ drives are capable of changing their head-speed. There are several reasons for changing the speed of a \cdrom\ drive. Badly pressed \cdrom s may benefit from less-than-maximum head rate. Modern \cdrom\ drives can obtain very high head rates (up to $24\times$ is common). It has been reported that these drives can make reading errors at these high speeds, reducing the speed can prevent data loss in these circumstances. Finally, some of these drives can make an annoyingly loud noise, which a lower speed may reduce. %Finally, %although the audio-low-pass filters probably aren't designed for it, %more than real-time playback of audio might be used for high-speed %copying of audio tracks. This function specifies the speed at which data is read or audio is played back. The value of $speed$ specifies the head-speed of the drive, measured in units of standard cdrom speed (176\,kB/sec raw data or 150\,kB/sec file system data). So to request that a \cdrom\ drive operate at 300\,kB/sec you would call the CDROM_SELECT_SPEED $ioctl$ with $speed=2$. The special value `0' means `auto-selection', \ie, maximum data-rate or real-time audio rate. If the drive doesn't have this `auto-selection' capability, the decision should be made on the current disc loaded and the return value should be positive. A negative return value indicates an error. \subsection{$Int\ select_disc(struct\ cdrom_device_info * cdi, int\ number)$} If the drive can store multiple discs (a juke-box) this function will perform disc selection. It should return the number of the selected disc on success, a negative value on error. Currently, only the ide-cd driver supports this functionality. \subsection{$Int\ get_last_session(struct\ cdrom_device_info * cdi, struct\ cdrom_multisession * ms_info)$} This function should implement the old corresponding $ioctl()$. For device $cdi\to dev$, the start of the last session of the current disc should be returned in the pointer argument $ms_info$. Note that routines in \cdromc\ have sanitized this argument: its requested format will {\em always\/} be of the type $CDROM_LBA$ (linear block addressing mode), whatever the calling software requested. But sanitization goes even further: the low-level implementation may return the requested information in $CDROM_MSF$ format if it wishes so (setting the $ms_info\rightarrow addr_format$ field appropriately, of course) and the routines in \cdromc\ will make the transformation if necessary. The return value is 0 upon success. \subsection{$Int\ get_mcn(struct\ cdrom_device_info * cdi, struct\ cdrom_mcn * mcn)$} Some discs carry a `Media Catalog Number' (MCN), also called `Universal Product Code' (UPC). This number should reflect the number that is generally found in the bar-code on the product. Unfortunately, the few discs that carry such a number on the disc don't even use the same format. The return argument to this function is a pointer to a pre-declared memory region of type $struct\ cdrom_mcn$. The MCN is expected as a 13-character string, terminated by a null-character. \subsection{$Int\ reset(struct\ cdrom_device_info * cdi)$} This call should perform a hard-reset on the drive (although in circumstances that a hard-reset is necessary, a drive may very well not listen to commands anymore). Preferably, control is returned to the caller only after the drive has finished resetting. If the drive is no longer listening, it may be wise for the underlying low-level cdrom driver to time out. \subsection{$Int\ audio_ioctl(struct\ cdrom_device_info * cdi, unsigned\ int\ cmd, void * arg)$} Some of the \cdrom-$ioctl$s defined in \cdromh\ can be implemented by the routines described above, and hence the function $cdrom_ioctl$ will use those. However, most $ioctl$s deal with audio-control. We have decided to leave these to be accessed through a single function, repeating the arguments $cmd$ and $arg$. Note that the latter is of type $void*{}$, rather than $unsigned\ long\ int$. The routine $cdrom_ioctl()$ does do some useful things, though. It sanitizes the address format type to $CDROM_MSF$ (Minutes, Seconds, Frames) for all audio calls. It also verifies the memory location of $arg$, and reserves stack-memory for the argument. This makes implementation of the $audio_ioctl()$ much simpler than in the old driver scheme. For example, you may look up the function $cm206_audio_ioctl()$ in {\tt {cm206.c}} that should be updated with this documentation. An unimplemented ioctl should return $-ENOSYS$, but a harmless request (\eg, $CDROMSTART$) may be ignored by returning 0 (success). Other errors should be according to the standards, whatever they are. When an error is returned by the low-level driver, the \UCD\ tries whenever possible to return the error code to the calling program. (We may decide to sanitize the return value in $cdrom_ioctl()$ though, in order to guarantee a uniform interface to the audio-player software.) \subsection{$Int\ dev_ioctl(struct\ cdrom_device_info * cdi, unsigned\ int\ cmd, unsigned\ long\ arg)$} Some $ioctl$s seem to be specific to certain \cdrom\ drives. That is, they are introduced to service some capabilities of certain drives. In fact, there are 6 different $ioctl$s for reading data, either in some particular kind of format, or audio data. Not many drives support reading audio tracks as data, I believe this is because of protection of copyrights of artists. Moreover, I think that if audio-tracks are supported, it should be done through the VFS and not via $ioctl$s. A problem here could be the fact that audio-frames are 2352 bytes long, so either the audio-file-system should ask for 75264 bytes at once (the least common multiple of 512 and 2352), or the drivers should bend their backs to cope with this incoherence (to which I would be opposed). Furthermore, it is very difficult for the hardware to find the exact frame boundaries, since there are no synchronization headers in audio frames. Once these issues are resolved, this code should be standardized in \cdromc. Because there are so many $ioctl$s that seem to be introduced to satisfy certain drivers,\footnote{Is there software around that actually uses these? I'd be interested!} any `non-standard' $ioctl$s are routed through the call $dev_ioctl()$. In principle, `private' $ioctl$s should be numbered after the device's major number, and not the general \cdrom\ $ioctl$ number, {\tt {0x53}}. Currently the non-supported $ioctl$s are: {\it CDROMREADMODE1, CDROMREADMODE2, CDROMREADAUDIO, CDROMREADRAW, CDROMREADCOOKED, CDROMSEEK, CDROMPLAY\-BLK and CDROM\-READALL}. \subsection{\cdrom\ capabilities} \label{capability} Instead of just implementing some $ioctl$ calls, the interface in \cdromc\ supplies the possibility to indicate the {\em capabilities\/} of a \cdrom\ drive. This can be done by ORing any number of capability-constants that are defined in \cdromh\ at the registration phase. Currently, the capabilities are any of: $$ \halign{$#$\ \hfil&$/*$ \rm# $*/$\hfil\cr CDC_CLOSE_TRAY& can close tray by software control\cr CDC_OPEN_TRAY& can open tray\cr CDC_LOCK& can lock and unlock the door\cr CDC_SELECT_SPEED& can select speed, in units of $\sim$150\,kB/s\cr CDC_SELECT_DISC& drive is juke-box\cr CDC_MULTI_SESSION& can read sessions $>\rm1$\cr CDC_MCN& can read Media Catalog Number\cr CDC_MEDIA_CHANGED& can report if disc has changed\cr CDC_PLAY_AUDIO& can perform audio-functions (play, pause, etc)\cr CDC_RESET& hard reset device\cr CDC_IOCTLS& driver has non-standard ioctls\cr CDC_DRIVE_STATUS& driver implements drive status\cr } $$ The capability flag is declared $const$, to prevent drivers from accidentally tampering with the contents. The capability fags actually inform \cdromc\ of what the driver can do. If the drive found by the driver does not have the capability, is can be masked out by the $cdrom_device_info$ variable $mask$. For instance, the SCSI \cdrom\ driver has implemented the code for loading and ejecting \cdrom's, and hence its corresponding flags in $capability$ will be set. But a SCSI \cdrom\ drive might be a caddy system, which can't load the tray, and hence for this drive the $cdrom_device_info$ struct will have set the $CDC_CLOSE_TRAY$ bit in $mask$. In the file \cdromc\ you will encounter many constructions of the type $$\it if\ (cdo\rightarrow capability \mathrel\& \mathord{\sim} cdi\rightarrow mask \mathrel{\&} CDC_<capability>) \ldots $$ There is no $ioctl$ to set the mask\dots The reason is that I think it is better to control the {\em behavior\/} rather than the {\em capabilities}. \subsection{Options} A final flag register controls the {\em behavior\/} of the \cdrom\ drives, in order to satisfy different users' wishes, hopefully independently of the ideas of the respective author who happened to have made the drive's support available to the \linux\ community. The current behavior options are: $$ \halign{$#$\ \hfil&$/*$ \rm# $*/$\hfil\cr CDO_AUTO_CLOSE& try to close tray upon device $open()$\cr CDO_AUTO_EJECT& try to open tray on last device $close()$\cr CDO_USE_FFLAGS& use $file_pointer\rightarrow f_flags$ to indicate purpose for $open()$\cr CDO_LOCK& try to lock door if device is opened\cr CDO_CHECK_TYPE& ensure disc type is data if opened for data\cr } $$ The initial value of this register is $CDO_AUTO_CLOSE \mathrel| CDO_USE_FFLAGS \mathrel| CDO_LOCK$, reflecting my own view on user interface and software standards. Before you protest, there are two new $ioctl$s implemented in \cdromc, that allow you to control the behavior by software. These are: $$ \halign{$#$\ \hfil&$/*$ \rm# $*/$\hfil\cr CDROM_SET_OPTIONS& set options specified in $(int)\ arg$\cr CDROM_CLEAR_OPTIONS& clear options specified in $(int)\ arg$\cr } $$ One option needs some more explanation: $CDO_USE_FFLAGS$. In the next newsection we explain what the need for this option is. A software package {\tt setcd}, available from the Debian distribution and {\tt sunsite.unc.edu}, allows user level control of these flags. \newsection{The need to know the purpose of opening the \cdrom\ device} Traditionally, Unix devices can be used in two different `modes', either by reading/writing to the device file, or by issuing controlling commands to the device, by the device's $ioctl()$ call. The problem with \cdrom\ drives, is that they can be used for two entirely different purposes. One is to mount removable file systems, \cdrom s, the other is to play audio CD's. Audio commands are implemented entirely through $ioctl$s, presumably because the first implementation (SUN?) has been such. In principle there is nothing wrong with this, but a good control of the `CD player' demands that the device can {\em always\/} be opened in order to give the $ioctl$ commands, regardless of the state the drive is in. On the other hand, when used as a removable-media disc drive (what the original purpose of \cdrom s is) we would like to make sure that the disc drive is ready for operation upon opening the device. In the old scheme, some \cdrom\ drivers don't do any integrity checking, resulting in a number of i/o errors reported by the VFS to the kernel when an attempt for mounting a \cdrom\ on an empty drive occurs. This is not a particularly elegant way to find out that there is no \cdrom\ inserted; it more-or-less looks like the old IBM-PC trying to read an empty floppy drive for a couple of seconds, after which the system complains it can't read from it. Nowadays we can {\em sense\/} the existence of a removable medium in a drive, and we believe we should exploit that fact. An integrity check on opening of the device, that verifies the availability of a \cdrom\ and its correct type (data), would be desirable. These two ways of using a \cdrom\ drive, principally for data and secondarily for playing audio discs, have different demands for the behavior of the $open()$ call. Audio use simply wants to open the device in order to get a file handle which is needed for issuing $ioctl$ commands, while data use wants to open for correct and reliable data transfer. The only way user programs can indicate what their {\em purpose\/} of opening the device is, is through the $flags$ parameter (see {\tt {open(2)}}). For \cdrom\ devices, these flags aren't implemented (some drivers implement checking for write-related flags, but this is not strictly necessary if the device file has correct permission flags). Most option flags simply don't make sense to \cdrom\ devices: $O_CREAT$, $O_NOCTTY$, $O_TRUNC$, $O_APPEND$, and $O_SYNC$ have no meaning to a \cdrom. We therefore propose to use the flag $O_NONBLOCK$ to indicate that the device is opened just for issuing $ioctl$ commands. Strictly, the meaning of $O_NONBLOCK$ is that opening and subsequent calls to the device don't cause the calling process to wait. We could interpret this as ``don't wait until someone has inserted some valid data-\cdrom.'' Thus, our proposal of the implementation for the $open()$ call for \cdrom s is: \begin{itemize} \item If no other flags are set than $O_RDONLY$, the device is opened for data transfer, and the return value will be 0 only upon successful initialization of the transfer. The call may even induce some actions on the \cdrom, such as closing the tray. \item If the option flag $O_NONBLOCK$ is set, opening will always be successful, unless the whole device doesn't exist. The drive will take no actions whatsoever. \end{itemize} \subsection{And what about standards?} You might hesitate to accept this proposal as it comes from the \linux\ community, and not from some standardizing institute. What about SUN, SGI, HP and all those other Unix and hardware vendors? Well, these companies are in the lucky position that they generally control both the hardware and software of their supported products, and are large enough to set their own standard. They do not have to deal with a dozen or more different, competing hardware configurations.\footnote{Incidentally, I think that SUN's approach to mounting \cdrom s is very good in origin: under Solaris a volume-daemon automatically mounts a newly inserted \cdrom\ under {\tt {/cdrom/$<volume-name>$/}}. In my opinion they should have pushed this further and have {\em every\/} \cdrom\ on the local area network be mounted at the similar location, \ie, no matter in which particular machine you insert a \cdrom, it will always appear at the same position in the directory tree, on every system. When I wanted to implement such a user-program for \linux, I came across the differences in behavior of the various drivers, and the need for an $ioctl$ informing about media changes.} We believe that using $O_NONBLOCK$ to indicate that a device is being opened for $ioctl$ commands only can be easily introduced in the \linux\ community. All the CD-player authors will have to be informed, we can even send in our own patches to the programs. The use of $O_NONBLOCK$ has most likely no influence on the behavior of the CD-players on other operating systems than \linux. Finally, a user can always revert to old behavior by a call to $ioctl(file_descriptor, CDROM_CLEAR_OPTIONS, CDO_USE_FFLAGS)$. \subsection{The preferred strategy of $open()$} The routines in \cdromc\ are designed in such a way that run-time configuration of the behavior of \cdrom\ devices (of {\em any\/} type) can be carried out, by the $CDROM_SET/CLEAR_OPTIONS$ $ioctls$. Thus, various modes of operation can be set: \begin{description} \item[$CDO_AUTO_CLOSE \mathrel| CDO_USE_FFLAGS \mathrel| CDO_LOCK$] This is the default setting. (With $CDO_CHECK_TYPE$ it will be better, in the future.) If the device is not yet opened by any other process, and if the device is being opened for data ($O_NONBLOCK$ is not set) and the tray is found to be open, an attempt to close the tray is made. Then, it is verified that a disc is in the drive and, if $CDO_CHECK_TYPE$ is set, that it contains tracks of type `data mode 1.' Only if all tests are passed is the return value zero. The door is locked to prevent file system corruption. If the drive is opened for audio ($O_NONBLOCK$ is set), no actions are taken and a value of 0 will be returned. \item[$CDO_AUTO_CLOSE \mathrel| CDO_AUTO_EJECT \mathrel| CDO_LOCK$] This mimics the behavior of the current sbpcd-driver. The option flags are ignored, the tray is closed on the first open, if necessary. Similarly, the tray is opened on the last release, \ie, if a \cdrom\ is unmounted, it is automatically ejected, such that the user can replace it. \end{description} We hope that these option can convince everybody (both driver maintainers and user program developers) to adopt the new \cdrom\ driver scheme and option flag interpretation. \newsection{Description of routines in \cdromc} Only a few routines in \cdromc\ are exported to the drivers. In this new section we will discuss these, as well as the functions that `take over' the \cdrom\ interface to the kernel. The header file belonging to \cdromc\ is called \cdromh. Formerly, some of the contents of this file were placed in the file {\tt {ucdrom.h}}, but this file has now been merged back into \cdromh. \subsection{$Struct\ file_operations\ cdrom_fops$} The contents of this structure were described in section~\ref{cdrom.c}. A pointer to this structure is assigned to the $fops$ field of the $struct gendisk$. \subsection{$Int\ register_cdrom( struct\ cdrom_device_info\ * cdi)$} This function is used in about the same way one registers $cdrom_fops$ with the kernel, the device operations and information structures, as described in section~\ref{cdrom.c}, should be registered with the \UCD: $$ register_cdrom(\&<device>_info)); $$ This function returns zero upon success, and non-zero upon failure. The structure $<device>_info$ should have a pointer to the driver's $<device>_dops$, as in $$ \vbox{\halign{&$#$\hfil\cr struct\ &cdrom_device_info\ <device>_info = \{\cr & <device>_dops;\cr &\ldots\cr \}\cr }}$$ Note that a driver must have one static structure, $<device>_dops$, while it may have as many structures $<device>_info$ as there are minor devices active. $Register_cdrom()$ builds a linked list from these. \subsection{$Int\ unregister_cdrom(struct\ cdrom_device_info * cdi)$} Unregistering device $cdi$ with minor number $MINOR(cdi\to dev)$ removes the minor device from the list. If it was the last registered minor for the low-level driver, this disconnects the registered device-operation routines from the \cdrom\ interface. This function returns zero upon success, and non-zero upon failure. \subsection{$Int\ cdrom_open(struct\ inode * ip, struct\ file * fp)$} This function is not called directly by the low-level drivers, it is listed in the standard $cdrom_fops$. If the VFS opens a file, this function becomes active. A strategy is implemented in this routine, taking care of all capabilities and options that are set in the $cdrom_device_ops$ connected to the device. Then, the program flow is transferred to the device_dependent $open()$ call. \subsection{$Void\ cdrom_release(struct\ inode *ip, struct\ file *fp)$} This function implements the reverse-logic of $cdrom_open()$, and then calls the device-dependent $release()$ routine. When the use-count has reached 0, the allocated buffers are flushed by calls to $sync_dev(dev)$ and $invalidate_buffers(dev)$. \subsection{$Int\ cdrom_ioctl(struct\ inode *ip, struct\ file *fp, unsigned\ int\ cmd, unsigned\ long\ arg)$} \label{cdrom-ioctl} This function handles all the standard $ioctl$ requests for \cdrom\ devices in a uniform way. The different calls fall into three categories: $ioctl$s that can be directly implemented by device operations, ones that are routed through the call $audio_ioctl()$, and the remaining ones, that are presumable device-dependent. Generally, a negative return value indicates an error. \subsubsection{Directly implemented $ioctl$s} \label{ioctl-direct} The following `old' \cdrom-$ioctl$s are implemented by directly calling device-operations in $cdrom_device_ops$, if implemented and not masked: \begin{description} \item[CDROMMULTISESSION] Requests the last session on a \cdrom. \item[CDROMEJECT] Open tray. \item[CDROMCLOSETRAY] Close tray. \item[CDROMEJECT_SW] If $arg\not=0$, set behavior to auto-close (close tray on first open) and auto-eject (eject on last release), otherwise set behavior to non-moving on $open()$ and $release()$ calls. \item[CDROM_GET_MCN] Get the Media Catalog Number from a CD. \end{description} \subsubsection{$Ioctl$s routed through $audio_ioctl()$} \label{ioctl-audio} The following set of $ioctl$s are all implemented through a call to the $cdrom_fops$ function $audio_ioctl()$. Memory checks and allocation are performed in $cdrom_ioctl()$, and also sanitization of address format ($CDROM_LBA$/$CDROM_MSF$) is done. \begin{description} \item[CDROMSUBCHNL] Get sub-channel data in argument $arg$ of type $struct\ cdrom_subchnl *{}$. \item[CDROMREADTOCHDR] Read Table of Contents header, in $arg$ of type $struct\ cdrom_tochdr *{}$. \item[CDROMREADTOCENTRY] Read a Table of Contents entry in $arg$ and specified by $arg$ of type $struct\ cdrom_tocentry *{}$. \item[CDROMPLAYMSF] Play audio fragment specified in Minute, Second, Frame format, delimited by $arg$ of type $struct\ cdrom_msf *{}$. \item[CDROMPLAYTRKIND] Play audio fragment in track-index format delimited by $arg$ of type $struct\ \penalty-1000 cdrom_ti *{}$. \item[CDROMVOLCTRL] Set volume specified by $arg$ of type $struct\ cdrom_volctrl *{}$. \item[CDROMVOLREAD] Read volume into by $arg$ of type $struct\ cdrom_volctrl *{}$. \item[CDROMSTART] Spin up disc. \item[CDROMSTOP] Stop playback of audio fragment. \item[CDROMPAUSE] Pause playback of audio fragment. \item[CDROMRESUME] Resume playing. \end{description} \subsubsection{New $ioctl$s in \cdromc} The following $ioctl$s have been introduced to allow user programs to control the behavior of individual \cdrom\ devices. New $ioctl$ commands can be identified by the underscores in their names. \begin{description} \item[CDROM_SET_OPTIONS] Set options specified by $arg$. Returns the option flag register after modification. Use $arg = \rm0$ for reading the current flags. \item[CDROM_CLEAR_OPTIONS] Clear options specified by $arg$. Returns the option flag register after modification. \item[CDROM_SELECT_SPEED] Select head-rate speed of disc specified as by $arg$ in units of standard cdrom speed (176\,kB/sec raw data or 150\,kB/sec file system data). The value 0 means `auto-select', \ie, play audio discs at real time and data discs at maximum speed. The value $arg$ is checked against the maximum head rate of the drive found in the $cdrom_dops$. \item[CDROM_SELECT_DISC] Select disc numbered $arg$ from a juke-box. First disc is numbered 0. The number $arg$ is checked against the maximum number of discs in the juke-box found in the $cdrom_dops$. \item[CDROM_MEDIA_CHANGED] Returns 1 if a disc has been changed since the last call. Note that calls to $cdrom_media_changed$ by the VFS are treated by an independent queue, so both mechanisms will detect a media change once. For juke-boxes, an extra argument $arg$ specifies the slot for which the information is given. The special value $CDSL_CURRENT$ requests that information about the currently selected slot be returned. \item[CDROM_DRIVE_STATUS] Returns the status of the drive by a call to $drive_status()$. Return values are defined in section~\ref{drive status}. Note that this call doesn't return information on the current playing activity of the drive; this can be polled through an $ioctl$ call to $CDROMSUBCHNL$. For juke-boxes, an extra argument $arg$ specifies the slot for which (possibly limited) information is given. The special value $CDSL_CURRENT$ requests that information about the currently selected slot be returned. \item[CDROM_DISC_STATUS] Returns the type of the disc currently in the drive. It should be viewed as a complement to $CDROM_DRIVE_STATUS$. This $ioctl$ can provide \emph {some} information about the current disc that is inserted in the drive. This functionality used to be implemented in the low level drivers, but is now carried out entirely in \UCD. The history of development of the CD's use as a carrier medium for various digital information has lead to many different disc types. This $ioctl$ is useful only in the case that CDs have \emph {only one} type of data on them. While this is often the case, it is also very common for CDs to have some tracks with data, and some tracks with audio. Because this is an existing interface, rather than fixing this interface by changing the assumptions it was made under, thereby breaking all user applications that use this function, the \UCD\ implements this $ioctl$ as follows: If the CD in question has audio tracks on it, and it has absolutely no CD-I, XA, or data tracks on it, it will be reported as $CDS_AUDIO$. If it has both audio and data tracks, it will return $CDS_MIXED$. If there are no audio tracks on the disc, and if the CD in question has any CD-I tracks on it, it will be reported as $CDS_XA_2_2$. Failing that, if the CD in question has any XA tracks on it, it will be reported as $CDS_XA_2_1$. Finally, if the CD in question has any data tracks on it, it will be reported as a data CD ($CDS_DATA_1$). This $ioctl$ can return: $$ \halign{$#$\ \hfil&$/*$ \rm# $*/$\hfil\cr CDS_NO_INFO& no information available\cr CDS_NO_DISC& no disc is inserted, or tray is opened\cr CDS_AUDIO& Audio disc (2352 audio bytes/frame)\cr CDS_DATA_1& data disc, mode 1 (2048 user bytes/frame)\cr CDS_XA_2_1& mixed data (XA), mode 2, form 1 (2048 user bytes)\cr CDS_XA_2_2& mixed data (XA), mode 2, form 1 (2324 user bytes)\cr CDS_MIXED& mixed audio/data disc\cr } $$ For some information concerning frame layout of the various disc types, see a recent version of \cdromh. \item[CDROM_CHANGER_NSLOTS] Returns the number of slots in a juke-box. \item[CDROMRESET] Reset the drive. \item[CDROM_GET_CAPABILITY] Returns the $capability$ flags for the drive. Refer to section \ref{capability} for more information on these flags. \item[CDROM_LOCKDOOR] Locks the door of the drive. $arg == \rm0$ unlocks the door, any other value locks it. \item[CDROM_DEBUG] Turns on debugging info. Only root is allowed to do this. Same semantics as CDROM_LOCKDOOR. \end{description} \subsubsection{Device dependent $ioctl$s} Finally, all other $ioctl$s are passed to the function $dev_ioctl()$, if implemented. No memory allocation or verification is carried out. \newsection{How to update your driver} \begin{enumerate} \item Make a backup of your current driver. \item Get hold of the files \cdromc\ and \cdromh, they should be in the directory tree that came with this documentation. \item Make sure you include \cdromh. \item Change the 3rd argument of $register_blkdev$ from $\&<your-drive>_fops$ to $\&cdrom_fops$. \item Just after that line, add the following to register with the \UCD: $$register_cdrom(\&<your-drive>_info);$$ Similarly, add a call to $unregister_cdrom()$ at the appropriate place. \item Copy an example of the device-operations $struct$ to your source, \eg, from {\tt {cm206.c}} $cm206_dops$, and change all entries to names corresponding to your driver, or names you just happen to like. If your driver doesn't support a certain function, make the entry $NULL$. At the entry $capability$ you should list all capabilities your driver currently supports. If your driver has a capability that is not listed, please send me a message. \item Copy the $cdrom_device_info$ declaration from the same example driver, and modify the entries according to your needs. If your driver dynamically determines the capabilities of the hardware, this structure should also be declared dynamically. \item Implement all functions in your $<device>_dops$ structure, according to prototypes listed in \cdromh, and specifications given in section~\ref{cdrom.c}. Most likely you have already implemented the code in a large part, and you will almost certainly need to adapt the prototype and return values. \item Rename your $<device>_ioctl()$ function to $audio_ioctl$ and change the prototype a little. Remove entries listed in the first