[media] v4l2-event: Add v4l2_subscribed_event_ops

Useful functions:

- v4l2_event_queue()

void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev)

  Queue events to video device. The driver's only responsibility is to fill

  in the type and the data fields. The other fields will be filled in by

  V4L2.

- v4l2_event_subscribe()

int v4l2_event_subscribe(struct v4l2_fh *fh,

			 struct v4l2_event_subscription *sub, unsigned elems,

			 const struct v4l2_subscribed_event_ops *ops)

  The video_device->ioctl_ops->vidioc_subscribe_event must check the driver

  is able to produce events with specified event id. Then it calls

  v4l2_event_subscribe() to subscribe the event. The last argument is the

  size of the event queue for this event. If it is 0, then the framework

  will fill in a default value (this depends on the event type).

  v4l2_event_subscribe() to subscribe the event.

- v4l2_event_unsubscribe()

  The elems argument is the size of the event queue for this event. If it is 0,

  then the framework will fill in a default value (this depends on the event

  type).

  The ops argument allows the driver to specify a number of callbacks:

  * add:     called when a new listener gets added (subscribing to the same

             event twice will only cause this callback to get called once)

  * del:     called when a listener stops listening

  * replace: replace event 'old' with event 'new'.

  * merge:   merge event 'old' into event 'new'.

  All 4 callbacks are optional, if you don't want to specify any callbacks

  the ops argument itself maybe NULL.

int v4l2_event_unsubscribe(struct v4l2_fh *fh,

			   struct v4l2_event_subscription *sub)

  vidioc_unsubscribe_event in struct v4l2_ioctl_ops. A driver may use

  v4l2_event_unsubscribe() directly unless it wants to be involved in

  The special type V4L2_EVENT_ALL may be used to unsubscribe all events. The

  drivers may want to handle this in a special way.

- v4l2_event_pending()

int v4l2_event_pending(struct v4l2_fh *fh)

  Returns the number of pending events. Useful when implementing poll.

	case V4L2_EVENT_VSYNC:

	case V4L2_EVENT_EOS:

	case V4L2_EVENT_CTRL:

		return v4l2_event_subscribe(fh, sub, 0);

		return v4l2_event_subscribe(fh, sub, 0, NULL);

	default:

		return -EINVAL;

	}

	if (sub->id != 0)

		return -EINVAL;

	return v4l2_event_subscribe(fh, sub, OMAP3ISP_CCDC_NEVENTS);

	return v4l2_event_subscribe(fh, sub, OMAP3ISP_CCDC_NEVENTS, NULL);

}

static int ccdc_unsubscribe_event(struct v4l2_subdev *sd, struct v4l2_fh *fh,

	if (sub->type != stat->event_type)

		return -EINVAL;

	return v4l2_event_subscribe(fh, sub, STAT_NEVENTS);

	return v4l2_event_subscribe(fh, sub, STAT_NEVENTS, NULL);

}

int omap3isp_stat_unsubscribe_event(struct v4l2_subdev *subdev,

				struct v4l2_event_subscription *sub)

{

	if (sub->type == V4L2_EVENT_CTRL)

		return v4l2_event_subscribe(fh, sub, 0);

		return v4l2_event_subscribe(fh, sub, 0, NULL);

	return -EINVAL;

}

EXPORT_SYMBOL(v4l2_ctrl_subscribe_event);