PM: introduce hibernation and suspend notifiers

Make it possible to register hibernation and suspend notifiers, so that
subsystems can perform hibernation-related or suspend-related operations that
should not be carried out by device drivers' .suspend() and .resume()
routines.

[akpm@linux-foundation.org: build fixes]
[akpm@linux-foundation.org: cleanups]
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Acked-by: Pavel Machek <pavel@ucw.cz>
Cc: Nigel Cunningham <nigel@nigel.suspend2.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/notifier.h b/include/linux/notifier.h
index 576f2bb..be3f2bb 100644
--- a/include/linux/notifier.h
+++ b/include/linux/notifier.h
@@ -212,5 +212,11 @@
 #define CPU_DEAD_FROZEN		(CPU_DEAD | CPU_TASKS_FROZEN)
 #define CPU_DYING_FROZEN	(CPU_DYING | CPU_TASKS_FROZEN)
 
+/* Hibernation and suspend events */
+#define PM_HIBERNATION_PREPARE	0x0001 /* Going to hibernate */
+#define PM_POST_HIBERNATION	0x0002 /* Hibernation finished */
+#define PM_SUSPEND_PREPARE	0x0003 /* Going to suspend the system */
+#define PM_POST_SUSPEND		0x0004 /* Suspend finished */
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_NOTIFIER_H */