sysfs/cpu: Add probe/release files

Version 3 of this patch is updated with documentation added to
Documentation/ABI.  There are no changes to any of the C code from v2
of the patch.

In order to support kernel DLPAR of CPU resources we need to provide an
interface to add (probe) and remove (release) the resource from the system.
This patch Creates new generic probe and release sysfs files to facilitate
cpu probe/release.  The probe/release interface provides for allowing each
arch to supply their own routines for implementing the backend of adding
and removing cpus to/from the system.

This also creates the powerpc specific stubs to handle the arch callouts
from writes to the sysfs files.

The creation and use of these files is regulated by the
CONFIG_ARCH_CPU_PROBE_RELEASE option so that only architectures that need the
capability will have the files created.

Signed-off-by: Nathan Fontenot <nfont@austin.ibm.com>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/Documentation/ABI/testing/sysfs-devices-system-cpu b/Documentation/ABI/testing/sysfs-devices-system-cpu
index a703b9e9aeb9..d868a11c94a5 100644
--- a/Documentation/ABI/testing/sysfs-devices-system-cpu
+++ b/Documentation/ABI/testing/sysfs-devices-system-cpu
@@ -62,6 +62,21 @@ Description:	CPU topology files that describe kernel limits related to
                 See Documentation/cputopology.txt for more information.
 
 
+What:           /sys/devices/system/cpu/probe
+                /sys/devices/system/cpu/release
+Date:           November 2009
+Contact:        Linux kernel mailing list <linux-kernel@vger.kernel.org>
+Description:    Dynamic addition and removal of CPU's.  This is not hotplug
+                removal, this is meant complete removal/addition of the CPU
+                from the system.
+
+                probe: writes to this file will dynamically add a CPU to the
+                system.  Information written to the file to add CPU's is
+                architecture specific.
+
+                release: writes to this file dynamically remove a CPU from
+                the system.  Information writtento the file to remove CPU's
+                is architecture specific.
 
 What:           /sys/devices/system/cpu/cpu#/node
 Date:           October 2009