Documentation: ABI: /sys/devices/system/cpu/cpu#/ topology files

Add brief descriptions for the following sysfs files:

	/sys/devices/system/cpu/cpu#/topology/core_id
	/sys/devices/system/cpu/cpu#/topology/core_siblings
	/sys/devices/system/cpu/cpu#/topology/core_siblings_list
	/sys/devices/system/cpu/cpu#/topology/physical_package_id
	/sys/devices/system/cpu/cpu#/topology/thread_siblings
	/sys/devices/system/cpu/cpu#/topology/thread_siblings_list

The descriptions in Documentation/cputopology.txt weren't very
informative, so I attempted a better description based on code
reading and hopeful guessing.

Updated Documentation/cputopology.txt with the better descriptions and
fixed some style issues.

Cc: Mike Travis <travis@sgi.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Alex Chiang <achiang@hp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 30 insertions, 17 deletions

diff --git a/Documentation/cputopology.txt b/Documentation/cputopology.txt
index b41f3e58aefa..f1c5c4bccd3e 100644
--- a/Documentation/cputopology.txt
+++ b/Documentation/cputopology.txt
@@ -1,15 +1,28 @@
 
-Export cpu topology info via sysfs. Items (attributes) are similar
+Export CPU topology info via sysfs. Items (attributes) are similar
 to /proc/cpuinfo.
 
 1) /sys/devices/system/cpu/cpuX/topology/physical_package_id:
-represent the physical package id of  cpu X;
+
+        physical package id of cpuX. Typically corresponds to a physical
+        socket number, but the actual value is architecture and platform
+        dependent.
+
 2) /sys/devices/system/cpu/cpuX/topology/core_id:
-represent the cpu core id to cpu X;
+
+        the CPU core ID of cpuX. Typically it is the hardware platform's
+        identifier (rather than the kernel's).  The actual value is
+        architecture and platform dependent.
+
 3) /sys/devices/system/cpu/cpuX/topology/thread_siblings:
-represent the thread siblings to cpu X in the same core;
+
+        internel kernel map of cpuX's hardware threads within the same
+        core as cpuX
+
 4) /sys/devices/system/cpu/cpuX/topology/core_siblings:
-represent the thread siblings to cpu X in the same physical package;
+
+        internal kernel map of cpuX's hardware threads within the same
+        physical_package_id.
 
 To implement it in an architecture-neutral way, a new source file,
 drivers/base/topology.c, is to export the 4 attributes.
@@ -32,32 +45,32 @@ not defined by include/asm-XXX/topology.h:
 3) thread_siblings: just the given CPU
 4) core_siblings: just the given CPU
 
-Additionally, cpu topology information is provided under
+Additionally, CPU topology information is provided under
 /sys/devices/system/cpu and includes these files.  The internal
 source for the output is in brackets ("[]").
 
-    kernel_max: the maximum cpu index allowed by the kernel configuration.
+    kernel_max: the maximum CPU index allowed by the kernel configuration.
                 [NR_CPUS-1]
 
-    offline:    cpus that are not online because they have been
+    offline:    CPUs that are not online because they have been
                 HOTPLUGGED off (see cpu-hotplug.txt) or exceed the limit
-                of cpus allowed by the kernel configuration (kernel_max
+                of CPUs allowed by the kernel configuration (kernel_max
                 above). [~cpu_online_mask + cpus >= NR_CPUS]
 
-    online:     cpus that are online and being scheduled [cpu_online_mask]
+    online:     CPUs that are online and being scheduled [cpu_online_mask]
 
-    possible:   cpus that have been allocated resources and can be
+    possible:   CPUs that have been allocated resources and can be
                 brought online if they are present. [cpu_possible_mask]
 
-    present:    cpus that have been identified as being present in the
+    present:    CPUs that have been identified as being present in the
                 system. [cpu_present_mask]
 
 The format for the above output is compatible with cpulist_parse()
 [see <linux/cpumask.h>].  Some examples follow.
 
-In this example, there are 64 cpus in the system but cpus 32-63 exceed
+In this example, there are 64 CPUs in the system but cpus 32-63 exceed
 the kernel max which is limited to 0..31 by the NR_CPUS config option
-being 32.  Note also that cpus 2 and 4-31 are not online but could be
+being 32.  Note also that CPUs 2 and 4-31 are not online but could be
 brought online as they are both present and possible.
 
      kernel_max: 31
@@ -67,8 +80,8 @@ brought online as they are both present and possible.
         present: 0-31
 
 In this example, the NR_CPUS config option is 128, but the kernel was
-started with possible_cpus=144.  There are 4 cpus in the system and cpu2
-was manually taken offline (and is the only cpu that can be brought
+started with possible_cpus=144.  There are 4 CPUs in the system and cpu2
+was manually taken offline (and is the only CPU that can be brought
 online.)
 
      kernel_max: 127
@@ -78,4 +91,4 @@ online.)
         present: 0-3
 
 See cpu-hotplug.txt for the possible_cpus=NUM kernel start parameter
-as well as more information on the various cpumask's.
+as well as more information on the various cpumasks.