2 files changed, 112 insertions, 7 deletions

diff --git a/Documentation/x86/boot.txt b/Documentation/x86/boot.txt
index 7b4596ac412..e0203662f9e 100644
--- a/Documentation/x86/boot.txt
+++ b/Documentation/x86/boot.txt
@@ -158,7 +158,7 @@ Offset	Proto	Name		Meaning
 0202/4  2.00+   header          Magic signature "HdrS"
 0206/2  2.00+   version         Boot protocol version supported
 0208/4  2.00+   realmode_swtch  Boot loader hook (see below)
-020C/2  2.00+   start_sys       The load-low segment (0x1000) (obsolete)
+020C/2  2.00+   start_sys_seg   The load-low segment (0x1000) (obsolete)
 020E/2  2.00+   kernel_version  Pointer to kernel version string
 0210/1  2.00+   type_of_loader  Boot loader identifier
 0211/1  2.00+   loadflags       Boot protocol option flags
@@ -170,10 +170,11 @@ Offset	Proto	Name		Meaning
 0224/2  2.01+   heap_end_ptr    Free memory after setup end
 0226/2  N/A     pad1            Unused
 0228/4  2.02+   cmd_line_ptr    32-bit pointer to the kernel command line
-022C/4  2.03+   initrd_addr_max Highest legal initrd address
+022C/4  2.03+   ramdisk_max     Highest legal initrd address
 0230/4  2.05+   kernel_alignment Physical addr alignment required for kernel
 0234/1  2.05+   relocatable_kernel Whether kernel is relocatable or not
-0235/3  N/A     pad2            Unused
+0235/1  N/A     pad2            Unused
+0236/2  N/A     pad3            Unused
 0238/4  2.06+   cmdline_size    Maximum size of the kernel command line
 023C/4  2.07+   hardware_subarch Hardware subarchitecture
 0240/8  2.07+   hardware_subarch_data Subarchitecture-specific data
@@ -299,14 +300,14 @@ Protocol:	2.00+
   e.g. 0x0204 for version 2.04, and 0x0a11 for a hypothetical version
   10.17.
 
-Field name:     readmode_swtch
+Field name:     realmode_swtch
 Type:           modify (optional)
 Offset/size:    0x208/4
 Protocol:       2.00+
 
   Boot loader hook (see ADVANCED BOOT LOADER HOOKS below.)
 
-Field name:     start_sys
+Field name:     start_sys_seg
 Type:           read
 Offset/size:    0x20c/2
 Protocol:       2.00+
@@ -468,7 +469,7 @@ Protocol:	2.02+
   zero, the kernel will assume that your boot loader does not support
   the 2.02+ protocol.
 
-Field name:     initrd_addr_max
+Field name:     ramdisk_max
 Type:           read
 Offset/size:    0x22c/4
 Protocol:       2.03+
@@ -542,7 +543,10 @@ Protocol:	2.08+
 
   The payload may be compressed. The format of both the compressed and
   uncompressed data should be determined using the standard magic
-  numbers. Currently only gzip compressed ELF is used.
+  numbers.  The currently supported compression formats are gzip
+  (magic numbers 1F 8B or 1F 9E), bzip2 (magic number 42 5A) and LZMA
+  (magic number 5D 00).  The uncompressed payload is currently always ELF
+  (magic number 7F 45 4C 46).
   
 Field name:     payload_length
 Type:           read
diff --git a/Documentation/x86/earlyprintk.txt b/Documentation/x86/earlyprintk.txt
new file mode 100644
index 00000000000..607b1a01606
--- /dev/null
+++ b/Documentation/x86/earlyprintk.txt
@@ -0,0 +1,101 @@
+
+Mini-HOWTO for using the earlyprintk=dbgp boot option with a
+USB2 Debug port key and a debug cable, on x86 systems.
+
+You need two computers, the 'USB debug key' special gadget and
+and two USB cables, connected like this:
+
+  [host/target] <-------> [USB debug key] <-------> [client/console]
+
+1. There are three specific hardware requirements:
+
+ a.) Host/target system needs to have USB debug port capability.
+
+ You can check this capability by looking at a 'Debug port' bit in
+ the lspci -vvv output:
+
+ # lspci -vvv
+ ...
+ 00:1d.7 USB Controller: Intel Corporation 82801H (ICH8 Family) USB2 EHCI Controller #1 (rev 03) (prog-if 20 [EHCI])
+         Subsystem: Lenovo ThinkPad T61
+         Control: I/O- Mem+ BusMaster+ SpecCycle- MemWINV- VGASnoop- ParErr- Stepping- SERR+ FastB2B- DisINTx-
+         Status: Cap+ 66MHz- UDF- FastB2B+ ParErr- DEVSEL=medium >TAbort- <TAbort- <MAbort- >SERR- <PERR- INTx-
+         Latency: 0
+         Interrupt: pin D routed to IRQ 19
+         Region 0: Memory at fe227000 (32-bit, non-prefetchable) [size=1K]
+         Capabilities: [50] Power Management version 2
+                 Flags: PMEClk- DSI- D1- D2- AuxCurrent=375mA PME(D0+,D1-,D2-,D3hot+,D3cold+)
+                 Status: D0 PME-Enable- DSel=0 DScale=0 PME+
+         Capabilities: [58] Debug port: BAR=1 offset=00a0
+                            ^^^^^^^^^^^ <==================== [ HERE ]
+         Kernel driver in use: ehci_hcd
+         Kernel modules: ehci-hcd
+ ...
+
+( If your system does not list a debug port capability then you probably
+  wont be able to use the USB debug key. )
+
+ b.) You also need a Netchip USB debug cable/key:
+
+        http://www.plxtech.com/products/NET2000/NET20DC/default.asp
+
+     This is a small blue plastic connector with two USB connections,
+     it draws power from its USB connections.
+
+ c.) Thirdly, you need a second client/console system with a regular USB port.
+
+2. Software requirements:
+
+ a.) On the host/target system:
+
+    You need to enable the following kernel config option:
+
+      CONFIG_EARLY_PRINTK_DBGP=y
+
+    And you need to add the boot command line: "earlyprintk=dbgp".
+    (If you are using Grub, append it to the 'kernel' line in
+     /etc/grub.conf)
+
+    NOTE: normally earlyprintk console gets turned off once the
+    regular console is alive - use "earlyprintk=dbgp,keep" to keep
+    this channel open beyond early bootup. This can be useful for
+    debugging crashes under Xorg, etc.
+
+ b.) On the client/console system:
+
+    You should enable the following kernel config option:
+
+      CONFIG_USB_SERIAL_DEBUG=y
+
+    On the next bootup with the modified kernel you should
+    get a /dev/ttyUSBx device(s).
+
+    Now this channel of kernel messages is ready to be used: start
+    your favorite terminal emulator (minicom, etc.) and set
+    it up to use /dev/ttyUSB0 - or use a raw 'cat /dev/ttyUSBx' to
+    see the raw output.
+
+ c.) On Nvidia Southbridge based systems: the kernel will try to probe
+     and find out which port has debug device connected.
+
+3. Testing that it works fine:
+
+   You can test the output by using earlyprintk=dbgp,keep and provoking
+   kernel messages on the host/target system. You can provoke a harmless
+   kernel message by for example doing:
+
+     echo h > /proc/sysrq-trigger
+
+   On the host/target system you should see this help line in "dmesg" output:
+
+     SysRq : HELP : loglevel(0-9) reBoot Crashdump terminate-all-tasks(E) memory-full-oom-kill(F) kill-all-tasks(I) saK show-backtrace-all-active-cpus(L) show-memory-usage(M) nice-all-RT-tasks(N) powerOff show-registers(P) show-all-timers(Q) unRaw Sync show-task-states(T) Unmount show-blocked-tasks(W) dump-ftrace-buffer(Z)
+
+   On the client/console system do:
+
+       cat /dev/ttyUSB0
+
+   And you should see the help line above displayed shortly after you've
+   provoked it on the host system.
+
+If it does not work then please ask about it on the linux-kernel@vger.kernel.org
+mailing list or contact the x86 maintainers.