From: Johannes Berg <johannes@sipsolutions.net>

Change /sys/power/state to not advertise any valid states (except for disk
if SOFTWARE_SUSPEND is enabled) when no pm_ops have been set so userspace
can easily discover what states should be available.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Cc: Rafael J. Wysocki <rjw@sisk.pl>
Cc: Pavel Macheck <pavel@ucw.cz>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 kernel/power/main.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletion(-)

diff -puN kernel/power/main.c~power-management-no-valid-states-w-o-pm_ops-docs kernel/power/main.c
--- a/kernel/power/main.c~power-management-no-valid-states-w-o-pm_ops-docs
+++ a/kernel/power/main.c
@@ -167,7 +167,10 @@ static inline int valid_state(suspend_st
 	if (state == PM_SUSPEND_DISK)
 		return 1;
 
-	if (pm_ops && pm_ops->valid && !pm_ops->valid(state))
+	/* all other states need lowlevel support and need to be
+	 * valid to the lowlevel implementation, no valid callback
+	 * implies that all are valid. */
+	if (!pm_ops || (pm_ops->valid && !pm_ops->valid(state)))
 		return 0;
 	return 1;
 }
_