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>

3 files changed, 28 insertions, 0 deletions

diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index 5dbd375a3f2a..0df57466e783 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -320,6 +320,10 @@ config HOTPLUG_CPU
 
           Say N if you are unsure.
 
+config ARCH_CPU_PROBE_RELEASE
+        def_bool y
+        depends on HOTPLUG_CPU
+
 config ARCH_ENABLE_MEMORY_HOTPLUG
         def_bool y
 
diff --git a/arch/powerpc/include/asm/machdep.h b/arch/powerpc/include/asm/machdep.h
index 9efa2be78331..9f0fc9e6ce0d 100644
--- a/arch/powerpc/include/asm/machdep.h
+++ b/arch/powerpc/include/asm/machdep.h
@@ -266,6 +266,11 @@ struct machdep_calls {
         void (*suspend_disable_irqs)(void);
         void (*suspend_enable_irqs)(void);
 #endif
+
+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+        ssize_t (*cpu_probe)(const char *, size_t);
+        ssize_t (*cpu_release)(const char *, size_t);
+#endif
 };
 
 extern void e500_idle(void);
diff --git a/arch/powerpc/kernel/sysfs.c b/arch/powerpc/kernel/sysfs.c
index 956ab33fd73f..e235e52dc4fe 100644
--- a/arch/powerpc/kernel/sysfs.c
+++ b/arch/powerpc/kernel/sysfs.c
@@ -461,6 +461,25 @@ static void unregister_cpu_online(unsigned int cpu)
 
         cacheinfo_cpu_offline(cpu);
 }
+
+#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
+ssize_t arch_cpu_probe(const char *buf, size_t count)
+{
+        if (ppc_md.cpu_probe)
+                return ppc_md.cpu_probe(buf, count);
+
+        return -EINVAL;
+}
+
+ssize_t arch_cpu_release(const char *buf, size_t count)
+{
+        if (ppc_md.cpu_release)
+                return ppc_md.cpu_release(buf, count);
+
+        return -EINVAL;
+}
+#endif /* CONFIG_ARCH_CPU_PROBE_RELEASE */
+
 #endif /* CONFIG_HOTPLUG_CPU */
 
 static int __cpuinit sysfs_cpu_notify(struct notifier_block *self,