From 72364b91ce022ded4aa541c62f51c10a65fb3498 Mon Sep 17 00:00:00 2001 From: Sakari Ailus Date: Wed, 6 Sep 2023 10:56:14 +0300 Subject: 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: Sakari Ailus Reviewed-by: Julien Massot Reviewed-by: Laurent Pinchart Signed-off-by: Hans Verkuil --- include/media/v4l2-subdev.h | 40 ++++++++++++++++++++++++++++++++++++++++ 1 file changed, 40 insertions(+) (limited to 'include/media') diff --git a/include/media/v4l2-subdev.h b/include/media/v4l2-subdev.h index 1af16b16f0bf..e22c50ce7e05 100644 --- a/include/media/v4l2-subdev.h +++ b/include/media/v4l2-subdev.h @@ -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 -- cgit v1.2.3