media: v4l: ctrl: Provide unlocked variant of v4l2_ctrl_grab

Sometimes it may be necessary to grab a control while holding the control
handler's lock. Provide an unlocked variant of v4l2_ctrl_grab for the
purpose --- it's called __v4l2_ctrl_grab.
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

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

@@ -2511,14 +2511,15 @@ void v4l2_ctrl_activate(struct v4l2_ctrl *ctrl, bool active)
 }
 EXPORT_SYMBOL(v4l2_ctrl_activate);
 
-void v4l2_ctrl_grab(struct v4l2_ctrl *ctrl, bool grabbed)
+void __v4l2_ctrl_grab(struct v4l2_ctrl *ctrl, bool grabbed)
 {
 	bool old;
 
 	if (ctrl == NULL)
 		return;
 
-	v4l2_ctrl_lock(ctrl);
+	lockdep_assert_held(ctrl->handler->lock);
+
 	if (grabbed)
 		/* set V4L2_CTRL_FLAG_GRABBED */
 		old = test_and_set_bit(1, &ctrl->flags);
@@ -2527,9 +2528,8 @@ void v4l2_ctrl_grab(struct v4l2_ctrl *ctrl, bool grabbed)
 		old = test_and_clear_bit(1, &ctrl->flags);
 	if (old != grabbed)
 		send_event(NULL, ctrl, V4L2_EVENT_CTRL_CH_FLAGS);
-	v4l2_ctrl_unlock(ctrl);
 }
-EXPORT_SYMBOL(v4l2_ctrl_grab);
+EXPORT_SYMBOL(__v4l2_ctrl_grab);
 
 /* Log the control name and value */
 static void log_ctrl(const struct v4l2_ctrl *ctrl,

include/media/v4l2-ctrls.h

@@ -728,6 +728,22 @@ struct v4l2_ctrl *v4l2_ctrl_find(struct v4l2_ctrl_handler *hdl, u32 id);
  */
 void v4l2_ctrl_activate(struct v4l2_ctrl *ctrl, bool active);
 
+/**
+ * __v4l2_ctrl_grab() - Unlocked variant of v4l2_ctrl_grab.
+ *
+ * @ctrl:	The control to (de)activate.
+ * @grabbed:	True if the control should become grabbed.
+ *
+ * This sets or clears the V4L2_CTRL_FLAG_GRABBED flag atomically.
+ * Does nothing if @ctrl == NULL.
+ * The V4L2_EVENT_CTRL event will be generated afterwards.
+ * This will usually be called when starting or stopping streaming in the
+ * driver.
+ *
+ * This function assumes that the control handler is locked by the caller.
+ */
+void __v4l2_ctrl_grab(struct v4l2_ctrl *ctrl, bool grabbed);
+
 /**
  * v4l2_ctrl_grab() - Mark the control as grabbed or not grabbed.
  *
@@ -743,7 +759,15 @@ void v4l2_ctrl_activate(struct v4l2_ctrl *ctrl, bool active);
  * This function assumes that the control handler is not locked and will
  * take the lock itself.
  */
-void v4l2_ctrl_grab(struct v4l2_ctrl *ctrl, bool grabbed);
+static inline void v4l2_ctrl_grab(struct v4l2_ctrl *ctrl, bool grabbed)
+{
+	if (!ctrl)
+		return;
+
+	v4l2_ctrl_lock(ctrl);
+	__v4l2_ctrl_grab(ctrl, grabbed);
+	v4l2_ctrl_unlock(ctrl);
+}
 
 /**
  *__v4l2_ctrl_modify_range() - Unlocked variant of v4l2_ctrl_modify_range()