[tip:timers/urgent] clockevents: Allow set-state callbacks to be optional

[tip-bot for Viresh Kumar]

Commit-ID:  7c4a976cd55972b68c75a978f171b6db5df4ce66
Gitweb:     http://git.kernel.org/tip/7c4a976cd55972b68c75a978f171b6db5df4ce66
Author:     Viresh Kumar <viresh.kumar@xxxxxxxxxx>
AuthorDate: Tue, 7 Jul 2015 10:14:35 +0200
Committer:  Thomas Gleixner <tglx@xxxxxxxxxxxxx>
CommitDate: Tue, 7 Jul 2015 10:44:45 +0200

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@xxxxxxxxxx>
Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
Signed-off-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Link: http://lkml.kernel.org/r/1436256875-15562-1-git-send-email-daniel.lezcano@xxxxxxxxxx
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
---
 kernel/time/clockevents.c | 24 +++++++++---------------
 1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/kernel/time/clockevents.c b/kernel/time/clockevents.c
index 08ccc3d..50eb107 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;
 }
 
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