clockevents: Allow set-state callbacks to be optional

Its mandatory for the drivers to provide set_state_{oneshot|periodic}()
(only if related modes are supported) and set_state_shutdown() callbacks
today, if they are implementing the new set-state interface.

But this leads to unnecessary noop callbacks for drivers which don't
want to implement them. Over that, it will lead to a full function call
for nothing really useful.

Lets make all set-state callbacks optional.

Suggested-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: http://lkml.kernel.org/r/1436256875-15562-1-git-send-email-daniel.lezcano@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 9 insertions, 15 deletions

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 08ccc3da3ca0..50eb107f1198 100644
--- a/kernel/time/clockevents.c
+++ b/kernel/time/clockevents.c
@@ -120,19 +120,25 @@ static int __clockevents_switch_state(struct clock_event_device *dev,
                 /* The clockevent device is getting replaced. Shut it down. */
 
         case CLOCK_EVT_STATE_SHUTDOWN:
-                return dev->set_state_shutdown(dev);
+                if (dev->set_state_shutdown)
+                        return dev->set_state_shutdown(dev);
+                return 0;
 
         case CLOCK_EVT_STATE_PERIODIC:
                 /* Core internal bug */
                 if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
                         return -ENOSYS;
-                return dev->set_state_periodic(dev);
+                if (dev->set_state_periodic)
+                        return dev->set_state_periodic(dev);
+                return 0;
 
         case CLOCK_EVT_STATE_ONESHOT:
                 /* Core internal bug */
                 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
                         return -ENOSYS;
-                return dev->set_state_oneshot(dev);
+                if (dev->set_state_oneshot)
+                        return dev->set_state_oneshot(dev);
+                return 0;
 
         case CLOCK_EVT_STATE_ONESHOT_STOPPED:
                 /* Core internal bug */
@@ -471,18 +477,6 @@ static int clockevents_sanity_check(struct clock_event_device *dev)
         if (dev->features & CLOCK_EVT_FEAT_DUMMY)
                 return 0;
 
-        /* New state-specific callbacks */
-        if (!dev->set_state_shutdown)
-                return -EINVAL;
-
-        if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
-            !dev->set_state_periodic)
-                return -EINVAL;
-
-        if ((dev->features & CLOCK_EVT_FEAT_ONESHOT) &&
-            !dev->set_state_oneshot)
-                return -EINVAL;
-
         return 0;
 }