Commit 72364b91 authored by Sakari Ailus's avatar Sakari Ailus Committed by Hans Verkuil
Browse files

media: v4l: subdev: Add a function to lock two sub-device states, use it 



Add two new functions, v4l2_subdev_lock_states() and
v4l2_subdev_unclock_states(), to acquire and release the state of two
sub-devices. They differ from calling v4l2_subdev_{un,}lock_state() so
that if the two states share the same lock, the lock is acquired only
once.

Also use the new functions in v4l2_subdev_link_validate().

Signed-off-by: default avatarSakari Ailus <sakari.ailus@linux.intel.com>
Reviewed-by: default avatarJulien Massot <julien.massot@collabora.com>
Reviewed-by: default avatarLaurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: default avatarHans Verkuil <hverkuil-cisco@xs4all.nl>
parent cd2c7545

drivers/media/v4l2-core/v4l2-subdev.c

+4 −8
Original line number Diff line number Diff line
@@ -1437,17 +1437,13 @@ int v4l2_subdev_link_validate(struct media_link *link) 


	states_locked = sink_state && source_state;



	if (states_locked) {

		v4l2_subdev_lock_state(sink_state);

		v4l2_subdev_lock_state(source_state);

	}

	if (states_locked)

		v4l2_subdev_lock_states(sink_state, source_state);



	ret = v4l2_subdev_link_validate_locked(link, states_locked);



	if (states_locked) {

		v4l2_subdev_unlock_state(sink_state);

		v4l2_subdev_unlock_state(source_state);

	}

	if (states_locked)

		v4l2_subdev_unlock_states(sink_state, source_state);



	return ret;

}

include/media/v4l2-subdev.h

+40 −0
Original line number Diff line number Diff line
@@ -1724,6 +1724,46 @@ static inline void v4l2_subdev_unlock_state(struct v4l2_subdev_state *state) 
	mutex_unlock(state->lock);

}



/**

 * v4l2_subdev_lock_states - Lock two sub-device states

 * @state1: One subdevice state

 * @state2: The other subdevice state

 *

 * Locks the state of two sub-devices.

 *

 * The states must be unlocked with v4l2_subdev_unlock_states() after use.

 *

 * This differs from calling v4l2_subdev_lock_state() on both states so that if

 * the states share the same lock, the lock is acquired only once (so no

 * deadlock occurs). The caller is responsible for ensuring the locks will

 * always be acquired in the same order.

 */

static inline void v4l2_subdev_lock_states(struct v4l2_subdev_state *state1,

					   struct v4l2_subdev_state *state2)

{

	mutex_lock(state1->lock);

	if (state1->lock != state2->lock)

		mutex_lock(state2->lock);

}



/**

 * v4l2_subdev_unlock_states() - Unlock two sub-device states

 * @state1: One subdevice state

 * @state2: The other subdevice state

 *

 * Unlocks the state of two sub-devices.

 *

 * This differs from calling v4l2_subdev_unlock_state() on both states so that

 * if the states share the same lock, the lock is released only once.

 */

static inline void v4l2_subdev_unlock_states(struct v4l2_subdev_state *state1,

					     struct v4l2_subdev_state *state2)

{

	mutex_unlock(state1->lock);

	if (state1->lock != state2->lock)

		mutex_unlock(state2->lock);

}



/**

 * v4l2_subdev_get_unlocked_active_state() - Checks that the active subdev state

 *					     is unlocked and returns it