[media] v4l: Allow changing control handler lock

Allow choosing the lock used by the control handler. This may be handy
sometimes when a driver providing multiple subdevs does not want to use
several locks to serialise its functions.

Signed-off-by: Sakari Ailus <sakari.ailus@iki.fi>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 6 insertions, 3 deletions

diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index c6f6b4c2c5f2..dde6fbacc271 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -167,7 +167,9 @@ struct v4l2_ctrl_ref {
 /** struct v4l2_ctrl_handler - The control handler keeps track of all the
   * controls: both the controls owned by the handler and those inherited
   * from other handlers.
+  * @_lock:     Default for "lock".
   * @lock:      Lock to control access to this handler and its controls.
+  *             May be replaced by the user right after init.
   * @ctrls:     The list of controls owned by this handler.
   * @ctrl_refs: The list of control references.
   * @cached:    The last found control reference. It is common that the same
@@ -178,7 +180,8 @@ struct v4l2_ctrl_ref {
   * @error:     The error code of the first failed control addition.
   */
 struct v4l2_ctrl_handler {
-        struct mutex lock;
+        struct mutex _lock;
+        struct mutex *lock;
         struct list_head ctrls;
         struct list_head ctrl_refs;
         struct v4l2_ctrl_ref *cached;
@@ -455,7 +458,7 @@ void v4l2_ctrl_grab(struct v4l2_ctrl *ctrl, bool grabbed);
   */
 static inline void v4l2_ctrl_lock(struct v4l2_ctrl *ctrl)
 {
-        mutex_lock(&ctrl->handler->lock);
+        mutex_lock(ctrl->handler->lock);
 }
 
 /** v4l2_ctrl_lock() - Helper function to unlock the handler
@@ -464,7 +467,7 @@ static inline void v4l2_ctrl_lock(struct v4l2_ctrl *ctrl)
   */
 static inline void v4l2_ctrl_unlock(struct v4l2_ctrl *ctrl)
 {
-        mutex_unlock(&ctrl->handler->lock);
+        mutex_unlock(ctrl->handler->lock);
 }
 
 /** v4l2_ctrl_g_ctrl() - Helper function to get the control's value from within a driver.