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 <hdego...@redhat.com>
---
 drivers/media/video/ivtv/ivtv-ioctl.c  |    2 +-
 drivers/media/video/omap3isp/ispccdc.c |    2 +-
 drivers/media/video/omap3isp/ispstat.c |    2 +-
 drivers/media/video/pwc/pwc-v4l.c      |    2 +-
 drivers/media/video/v4l2-event.c       |   42 ++++++++++++++++++++++++-------
 drivers/media/video/vivi.c             |    2 +-
 include/media/v4l2-event.h             |   24 +++++++++++++-----
 7 files changed, 54 insertions(+), 22 deletions(-)

diff --git a/drivers/media/video/ivtv/ivtv-ioctl.c 
b/drivers/media/video/ivtv/ivtv-ioctl.c
index ecafa69..9aec8a0 100644
--- a/drivers/media/video/ivtv/ivtv-ioctl.c
+++ b/drivers/media/video/ivtv/ivtv-ioctl.c
@@ -1456,7 +1456,7 @@ 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 40b141c..b6da736 100644
--- a/drivers/media/video/omap3isp/ispccdc.c
+++ b/drivers/media/video/omap3isp/ispccdc.c
@@ -1700,7 +1700,7 @@ 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 8080659..4f337a2 100644
--- a/drivers/media/video/omap3isp/ispstat.c
+++ b/drivers/media/video/omap3isp/ispstat.c
@@ -1049,7 +1049,7 @@ 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/pwc/pwc-v4l.c 
b/drivers/media/video/pwc/pwc-v4l.c
index 68e1323..7f159bf 100644
--- a/drivers/media/video/pwc/pwc-v4l.c
+++ b/drivers/media/video/pwc/pwc-v4l.c
@@ -1138,7 +1138,7 @@ static int pwc_subscribe_event(struct v4l2_fh *fh,
 {
        switch (sub->type) {
        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/v4l2-event.c b/drivers/media/video/v4l2-event.c
index 9f56f18..7190c2b 100644
--- a/drivers/media/video/v4l2-event.c
+++ b/drivers/media/video/v4l2-event.c
@@ -131,14 +131,14 @@ 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);
                }
        }
 
@@ -207,8 +207,14 @@ static void ctrls_merge(const struct v4l2_event *old, 
struct v4l2_event *new)
        new->u.ctrl.changes |= old->u.ctrl.changes;
 }
 
+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;
@@ -236,9 +242,9 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
        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);
@@ -247,10 +253,22 @@ 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);
 
        return 0;
@@ -300,6 +318,10 @@ 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/media/video/vivi.c b/drivers/media/video/vivi.c
index c25787d..74ebbad 100644
--- a/drivers/media/video/vivi.c
+++ b/drivers/media/video/vivi.c
@@ -1013,7 +1013,7 @@ static int vidioc_subscribe_event(struct v4l2_fh *fh,
 {
        switch (sub->type) {
        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/include/media/v4l2-event.h b/include/media/v4l2-event.h
index 5f14e88..88fa9a1 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);
-- 
1.7.7

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