power management: no valid states w/o pm_ops

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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 4 insertions, 1 deletions

diff --git a/kernel/power/main.c b/kernel/power/main.c
index e1c413120469..a064dfd8877a 100644
--- a/kernel/power/main.c
+++ b/kernel/power/main.c
@@ -167,7 +167,10 @@ static inline int valid_state(suspend_state_t state)
         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;
 }