[media] v4l2-event: Add v4l2_subscribed_event_ops

Just like with ctrl events, drivers may want to get called back on
listener add / remove for other event types too. Rather then special
casing all of this in subscribe / unsubscribe event it is better to
use ops for this.

Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Acked-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

1 files changed, 43 insertions, 11 deletions

diff --git a/drivers/media/video/v4l2-event.c b/drivers/media/video/v4l2-event.c
index c26ad9637143..0ba2dfa86d07 100644
--- a/drivers/media/video/v4l2-event.c
+++ b/drivers/media/video/v4l2-event.c
@@ -120,6 +120,14 @@ static void __v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *e
 	if (sev == NULL)
 		return;
 
+	/*
+	 * If the event has been added to the fh->subscribed list, but its
+	 * add op has not completed yet elems will be 0, treat this as
+	 * not being subscribed.
+	 */
+	if (!sev->elems)
+		return;
+
 	/* Increase event sequence number on fh. */
 	fh->sequence++;
 
@@ -132,14 +140,14 @@ static void __v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *e
 		sev->first = sev_pos(sev, 1);
 		fh->navailable--;
 		if (sev->elems == 1) {
-			if (sev->replace) {
-				sev->replace(&kev->event, ev);
+			if (sev->ops && sev->ops->replace) {
+				sev->ops->replace(&kev->event, ev);
 				copy_payload = false;
 			}
-		} else if (sev->merge) {
+		} else if (sev->ops && sev->ops->merge) {
 			struct v4l2_kevent *second_oldest =
 				sev->events + sev_pos(sev, 0);
-			sev->merge(&kev->event, &second_oldest->event);
+			sev->ops->merge(&kev->event, &second_oldest->event);
 		}
 	}
 
@@ -208,8 +216,14 @@ static void ctrls_merge(const struct v4l2_event *old, struct v4l2_event *new)
 	new->u.ctrl.changes |= old->u.ctrl.changes;
 }
 
+static const struct v4l2_subscribed_event_ops ctrl_ops = {
+	.replace = ctrls_replace,
+	.merge = ctrls_merge,
+};
+
 int v4l2_event_subscribe(struct v4l2_fh *fh,
-			 struct v4l2_event_subscription *sub, unsigned elems)
+			 struct v4l2_event_subscription *sub, unsigned elems,
+			 const struct v4l2_subscribed_event_ops *ops)
 {
 	struct v4l2_subscribed_event *sev, *found_ev;
 	struct v4l2_ctrl *ctrl = NULL;
@@ -236,10 +250,9 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
 	sev->id = sub->id;
 	sev->flags = sub->flags;
 	sev->fh = fh;
-	sev->elems = elems;
+	sev->ops = ops;
 	if (ctrl) {
-		sev->replace = ctrls_replace;
-		sev->merge = ctrls_merge;
+		sev->ops = &ctrl_ops;
 	}
 
 	spin_lock_irqsave(&fh->vdev->fh_lock, flags);
@@ -248,12 +261,27 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
 		list_add(&sev->list, &fh->subscribed);
 	spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
 
-	/* v4l2_ctrl_add_event uses a mutex, so do this outside the spin lock */
-	if (found_ev)
+	if (found_ev) {
 		kfree(sev);
-	else if (ctrl)
+		return 0; /* Already listening */
+	}
+
+	if (sev->ops && sev->ops->add) {
+		int ret = sev->ops->add(sev);
+		if (ret) {
+			sev->ops = NULL;
+			v4l2_event_unsubscribe(fh, sub);
+			return ret;
+		}
+	}
+
+	/* v4l2_ctrl_add_event uses a mutex, so do this outside the spin lock */
+	if (ctrl)
 		v4l2_ctrl_add_event(ctrl, sev);
 
+	/* Mark as ready for use */
+	sev->elems = elems;
+
 	return 0;
 }
 EXPORT_SYMBOL_GPL(v4l2_event_subscribe);
@@ -306,6 +334,10 @@ int v4l2_event_unsubscribe(struct v4l2_fh *fh,
 	}
 
 	spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
+
+	if (sev && sev->ops && sev->ops->del)
+		sev->ops->del(sev);
+
 	if (sev && sev->type == V4L2_EVENT_CTRL) {
 		struct v4l2_ctrl *ctrl = v4l2_ctrl_find(fh->ctrl_handler, sev->id);