doc: Add documentation for bootloader_{type,version}

Add documentation for kernel/bootloader_type and kernel/bootloader_version to sysctl/kernel.txt. This should really have been done a long time ago. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Cc: Shen Feng <shen@cn.fujitsu.com>

doc: Add documentation for bootloader_{type,version}
Add documentation for kernel/bootloader_type and kernel/bootloader_version to sysctl/kernel.txt. This should really have been done a long time ago. Signed-off-by: H. Peter Anvin <hpa@zytor.com> Cc: Shen Feng <shen@cn.fujitsu.com>
H. Peter Anvin
1 parent 505422517d
Showing 1 changed file with 31 additions and 0 deletions Side-by-side Diff
Documentation/sysctl/kernel.txt
@@ -19,6 +19,8 @@
 show up in /proc/sys/kernel:
 - acpi_video_flags
 - acct
+- bootloader_type	     [ X86 only ]
+- bootloader_version	     [ X86 only ]
 - callhome		     [ S390 only ]
 - auto_msgmni
 - core_pattern
@@ -90,6 +92,35 @@
 That is, suspend accounting if there left <= 2% free; resume it
 if we got >=4%; consider information about amount of free space
 valid for 30 seconds.
+
+==============================================================
+
+bootloader_type:
+
+x86 bootloader identification
+
+This gives the bootloader type number as indicated by the bootloader,
+shifted left by 4, and OR'd with the low four bits of the bootloader
+version.  The reason for this encoding is that this used to match the
+type_of_loader field in the kernel header; the encoding is kept for
+backwards compatibility.  That is, if the full bootloader type number
+is 0x15 and the full version number is 0x234, this file will contain
+the value 340 = 0x154.
+
+See the type_of_loader and ext_loader_type fields in
+Documentation/x86/boot.txt for additional information.
+
+==============================================================
+
+bootloader_version:
+
+x86 bootloader version
+
+The complete bootloader version number.  In the example above, this
+file will contain the value 564 = 0x234.
+
+See the type_of_loader and ext_loader_ver fields in
+Documentation/x86/boot.txt for additional information.
  
 ==============================================================
...	...	@@ -19,6 +19,8 @@
19	19	show up in /proc/sys/kernel:
20	20	- acpi_video_flags
21	21	- acct
	22	+- bootloader_type [ X86 only ]
	23	+- bootloader_version [ X86 only ]
22	24	- callhome [ S390 only ]
23	25	- auto_msgmni
24	26	- core_pattern
...	...	@@ -90,6 +92,35 @@
90	92	That is, suspend accounting if there left <= 2% free; resume it
91	93	if we got >=4%; consider information about amount of free space
92	94	valid for 30 seconds.
	95	+
	96	+==============================================================
	97	+
	98	+bootloader_type:
	99	+
	100	+x86 bootloader identification
	101	+
	102	+This gives the bootloader type number as indicated by the bootloader,
	103	+shifted left by 4, and OR'd with the low four bits of the bootloader
	104	+version. The reason for this encoding is that this used to match the
	105	+type_of_loader field in the kernel header; the encoding is kept for
	106	+backwards compatibility. That is, if the full bootloader type number
	107	+is 0x15 and the full version number is 0x234, this file will contain
	108	+the value 340 = 0x154.
	109	+
	110	+See the type_of_loader and ext_loader_type fields in
	111	+Documentation/x86/boot.txt for additional information.
	112	+
	113	+==============================================================
	114	+
	115	+bootloader_version:
	116	+
	117	+x86 bootloader version
	118	+
	119	+The complete bootloader version number. In the example above, this
	120	+file will contain the value 564 = 0x234.
	121	+
	122	+See the type_of_loader and ext_loader_ver fields in
	123	+Documentation/x86/boot.txt for additional information.
93	124
94	125	==============================================================
95	126