[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>

8 files changed, 86 insertions, 30 deletions

diff --git a/Documentation/video4linux/v4l2-framework.txt b/Documentation/video4linux/v4l2-framework.txt
index e3dfc268d9c1..369d4bc87828 100644
--- a/Documentation/video4linux/v4l2-framework.txt
+++ b/Documentation/video4linux/v4l2-framework.txt
@@ -945,21 +945,35 @@ fast.
 
 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
@@ -968,7 +982,7 @@ Useful functions:
   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.
 
diff --git a/drivers/media/video/ivtv/ivtv-ioctl.c b/drivers/media/video/ivtv/ivtv-ioctl.c
index a151271f60e1..a7730fd4827f 100644
--- a/drivers/media/video/ivtv/ivtv-ioctl.c
+++ b/drivers/media/video/ivtv/ivtv-ioctl.c
@@ -1469,7 +1469,7 @@ static int ivtv_subscribe_event(struct v4l2_fh *fh, struct v4l2_event_subscripti
         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;
         }
diff --git a/drivers/media/video/omap3isp/ispccdc.c b/drivers/media/video/omap3isp/ispccdc.c
index eaabc27f0fa2..1f3c16d8f0b4 100644
--- a/drivers/media/video/omap3isp/ispccdc.c
+++ b/drivers/media/video/omap3isp/ispccdc.c
@@ -1703,7 +1703,7 @@ static int ccdc_subscribe_event(struct v4l2_subdev *sd, struct v4l2_fh *fh,
         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,
diff --git a/drivers/media/video/omap3isp/ispstat.c b/drivers/media/video/omap3isp/ispstat.c
index 11871ecc6d25..b8640be692f1 100644
--- a/drivers/media/video/omap3isp/ispstat.c
+++ b/drivers/media/video/omap3isp/ispstat.c
@@ -1032,7 +1032,7 @@ int omap3isp_stat_subscribe_event(struct v4l2_subdev *subdev,
         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,
diff --git a/drivers/media/video/v4l2-ctrls.c b/drivers/media/video/v4l2-ctrls.c
index c93a9796f1fb..91b197819fc2 100644
--- a/drivers/media/video/v4l2-ctrls.c
+++ b/drivers/media/video/v4l2-ctrls.c
@@ -2468,7 +2468,7 @@ int v4l2_ctrl_subscribe_event(struct v4l2_fh *fh,
                                 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);
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);
 
diff --git a/drivers/usb/gadget/uvc_v4l2.c b/drivers/usb/gadget/uvc_v4l2.c
index f6e083b50191..90db5fe9c56e 100644
--- a/drivers/usb/gadget/uvc_v4l2.c
+++ b/drivers/usb/gadget/uvc_v4l2.c
@@ -296,7 +296,7 @@ uvc_v4l2_do_ioctl(struct file *file, unsigned int cmd, void *arg)
                 if (sub->type < UVC_EVENT_FIRST || sub->type > UVC_EVENT_LAST)
                         return -EINVAL;
 
-                return v4l2_event_subscribe(&handle->vfh, arg, 2);
+                return v4l2_event_subscribe(&handle->vfh, arg, 2, NULL);
         }
 
         case VIDIOC_UNSUBSCRIBE_EVENT:
diff --git a/include/media/v4l2-event.h b/include/media/v4l2-event.h
index 5f14e8895ce2..88fa9a1e0df3 100644
--- a/include/media/v4l2-event.h
+++ b/include/media/v4l2-event.h
@@ -78,6 +78,19 @@ struct v4l2_kevent {
         struct v4l2_event       event;
 };
 
+/** struct v4l2_subscribed_event_ops - Subscribed event operations.
+  * @add:       Optional callback, called when a new listener is added
+  * @del:       Optional callback, called when a listener stops listening
+  * @replace:   Optional callback that can replace event 'old' with event 'new'.
+  * @merge:     Optional callback that can merge event 'old' into event 'new'.
+  */
+struct v4l2_subscribed_event_ops {
+        int  (*add)(struct v4l2_subscribed_event *sev);
+        void (*del)(struct v4l2_subscribed_event *sev);
+        void (*replace)(struct v4l2_event *old, const struct v4l2_event *new);
+        void (*merge)(const struct v4l2_event *old, struct v4l2_event *new);
+};
+
 /** struct v4l2_subscribed_event - Internal struct representing a subscribed event.
   * @list:      List node for the v4l2_fh->subscribed list.
   * @type:      Event type.
@@ -85,8 +98,7 @@ struct v4l2_kevent {
   * @flags:     Copy of v4l2_event_subscription->flags.
   * @fh:        Filehandle that subscribed to this event.
   * @node:      List node that hooks into the object's event list (if there is one).
-  * @replace:   Optional callback that can replace event 'old' with event 'new'.
-  * @merge:     Optional callback that can merge event 'old' into event 'new'.
+  * @ops:       v4l2_subscribed_event_ops
   * @elems:     The number of elements in the events array.
   * @first:     The index of the events containing the oldest available event.
   * @in_use:    The number of queued events.
@@ -99,10 +111,7 @@ struct v4l2_subscribed_event {
         u32                     flags;
         struct v4l2_fh          *fh;
         struct list_head        node;
-        void                    (*replace)(struct v4l2_event *old,
-                                           const struct v4l2_event *new);
-        void                    (*merge)(const struct v4l2_event *old,
-                                         struct v4l2_event *new);
+        const struct v4l2_subscribed_event_ops *ops;
         unsigned                elems;
         unsigned                first;
         unsigned                in_use;
@@ -115,7 +124,8 @@ void v4l2_event_queue(struct video_device *vdev, const struct v4l2_event *ev);
 void v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *ev);
 int v4l2_event_pending(struct v4l2_fh *fh);
 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);
 int v4l2_event_unsubscribe(struct v4l2_fh *fh,
                            struct v4l2_event_subscription *sub);
 void v4l2_event_unsubscribe_all(struct v4l2_fh *fh);