[media] v4l2-ctrls: add control events

Whenever a control changes value or state an event is sent to anyone
that subscribed to it.

This functionality is useful for control panels but also for applications
that need to wait for (usually status) controls to change value.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 18 insertions, 5 deletions

diff --git a/include/media/v4l2-ctrls.h b/include/media/v4l2-ctrls.h
index e720f11a56fd..c45bf40e080d 100644
--- a/include/media/v4l2-ctrls.h
+++ b/include/media/v4l2-ctrls.h
@@ -28,9 +28,10 @@
 /* forward references */
 struct v4l2_ctrl_handler;
 struct v4l2_ctrl;
-struct v4l2_fh;
 struct video_device;
 struct v4l2_subdev;
+struct v4l2_event_subscription;
+struct v4l2_fh;
 
 /** struct v4l2_ctrl_ops - The control operations that the driver has to provide.
   * @g_volatile_ctrl: Get a new value for this control. Generally only relevant
@@ -107,6 +108,7 @@ struct v4l2_ctrl_ops {
 struct v4l2_ctrl {
 	/* Administrative fields */
 	struct list_head node;
+	struct list_head fhs;
 	struct v4l2_ctrl_handler *handler;
 	struct v4l2_ctrl **cluster;
 	unsigned ncontrols;
@@ -180,6 +182,11 @@ struct v4l2_ctrl_handler {
 	int error;
 };
 
+struct v4l2_ctrl_fh {
+	struct list_head node;
+	struct v4l2_fh *fh;
+};
+
 /** struct v4l2_ctrl_config - Control configuration structure.
   * @ops:	The control ops.
   * @id:	The control ID.
@@ -425,9 +432,9 @@ struct v4l2_ctrl *v4l2_ctrl_find(struct v4l2_ctrl_handler *hdl, u32 id);
   * This sets or clears the V4L2_CTRL_FLAG_INACTIVE flag atomically.
   * Does nothing if @ctrl == NULL.
   * This will usually be called from within the s_ctrl op.
+  * The V4L2_EVENT_CTRL event will be generated afterwards.
   *
-  * This function can be called regardless of whether the control handler
-  * is locked or not.
+  * This function assumes that the control handler is locked.
   */
 void v4l2_ctrl_activate(struct v4l2_ctrl *ctrl, bool active);
 
@@ -437,11 +444,12 @@ void v4l2_ctrl_activate(struct v4l2_ctrl *ctrl, bool active);
   *
   * 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 can be called regardless of whether the control handler
-  * is locked or not.
+  * 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);
 
@@ -486,6 +494,11 @@ s32 v4l2_ctrl_g_ctrl(struct v4l2_ctrl *ctrl);
   */
 int v4l2_ctrl_s_ctrl(struct v4l2_ctrl *ctrl, s32 val);
 
+void v4l2_ctrl_add_fh(struct v4l2_ctrl_handler *hdl,
+		struct v4l2_ctrl_fh *ctrl_fh,
+		struct v4l2_event_subscription *sub);
+void v4l2_ctrl_del_fh(struct v4l2_ctrl *ctrl, struct v4l2_fh *fh);
+
 /* Helpers for ioctl_ops. If hdl == NULL then they will all return -EINVAL. */
 int v4l2_queryctrl(struct v4l2_ctrl_handler *hdl, struct v4l2_queryctrl *qc);
 int v4l2_querymenu(struct v4l2_ctrl_handler *hdl, struct v4l2_querymenu *qm);