[PATCH v2] media: v4l2-subdev: Refactor events

[Tommaso Merciai <tomm.merciai@gmail.com>]

Controls can be exposed to userspace via a v4l-subdevX device, and
userspace has to be able to subscribe to control events so that it is
notified when the control changes value.
If a control handler is set for the subdev then set the HAS_EVENTS
flag automatically into v4l2_subdev_init_finalize() and use
v4l2_ctrl_subdev_subscribe_event() and v4l2_event_subdev_unsubscribe()
as default if subdev don't have .(un)subscribe control operations.

Signed-off-by: Tommaso Merciai <tomm.merciai@gmail.com>
---
Changes since v1:
 - Aligned event subscription with unsubscription as suggested by LPinchart,
   SAilus

 drivers/media/v4l2-core/v4l2-subdev.c | 22 ++++++++++++++++++++--
 1 file changed, 20 insertions(+), 2 deletions(-)

diff --git a/drivers/media/v4l2-core/v4l2-subdev.c b/drivers/media/v4l2-core/v4l2-subdev.c
index 3a4ba08810d2..fad8fa1f63e8 100644
--- a/drivers/media/v4l2-core/v4l2-subdev.c
+++ b/drivers/media/v4l2-core/v4l2-subdev.c
@@ -691,10 +691,25 @@ static long subdev_do_ioctl(struct file *file, unsigned int cmd, void *arg,
 		return v4l2_event_dequeue(vfh, arg, file->f_flags & O_NONBLOCK);
 
 	case VIDIOC_SUBSCRIBE_EVENT:
-		return v4l2_subdev_call(sd, core, subscribe_event, vfh, arg);
+		if (v4l2_subdev_has_op(sd, core, subscribe_event))
+			return v4l2_subdev_call(sd, core, subscribe_event,
+						vfh, arg);
+
+		if ((sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS) &&
+		    vfh->ctrl_handler)
+			return v4l2_ctrl_subdev_subscribe_event(sd, vfh, arg);
+
+		return -ENOIOCTLCMD;
 
 	case VIDIOC_UNSUBSCRIBE_EVENT:
-		return v4l2_subdev_call(sd, core, unsubscribe_event, vfh, arg);
+		if (v4l2_subdev_has_op(sd, core, unsubscribe_event))
+			return v4l2_subdev_call(sd, core, unsubscribe_event,
+						vfh, arg);
+
+		if (sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS)
+			return v4l2_event_subdev_unsubscribe(sd, vfh, arg);
+
+		return -ENOIOCTLCMD;
 
 #ifdef CONFIG_VIDEO_ADV_DEBUG
 	case VIDIOC_DBG_G_REGISTER:
@@ -1641,6 +1656,9 @@ int __v4l2_subdev_init_finalize(struct v4l2_subdev *sd, const char *name,
 		}
 	}
 
+	if (sd->ctrl_handler)
+		sd->flags |= V4L2_SUBDEV_FL_HAS_EVENTS;
+
 	state = __v4l2_subdev_state_alloc(sd, name, key);
 	if (IS_ERR(state))
 		return PTR_ERR(state);
-- 
2.34.1