[media] v4l2-event/ctrls/fh: allocate events per fh and per type instead of just per-fh

The driver had to decide how many events to allocate when the v4l2_fh struct
was created. It was possible to add more events afterwards, but there was no
way to ensure that you wouldn't miss important events if the event queue
would fill up for that filehandle.

In addition, once there were no more free events, any new events were simply
dropped on the floor.

For the control event in particular this made life very difficult since
control status/value changes could just be missed if the number of allocated
events and the speed at which the application read events was too low to keep
up with the number of generated events. The application would have no idea
what the latest state was for a control since it could have missed the latest
control change.

So this patch makes some major changes in how events are allocated. Instead
of allocating events per-filehandle they are now allocated when subscribing an
event. So for that particular event type N events (determined by the driver)
are allocated. Those events are reserved for that particular event type.
This ensures that you will not miss events for a particular type altogether.

In addition, if there are N events in use and a new event is raised, then
the oldest event is dropped and the new one is added. So the latest event
is always available.

This can be further improved by adding the ability to merge the state of
two events together, ensuring that no data is lost at all. This will be
added in the next patch.

This also makes it possible to allow the user to determine the number of
events that will be allocated. This is not implemented at the moment, but
would be trivial.

Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

10 files changed, 39 insertions, 106 deletions

diff --git a/drivers/media/video/ivtv/ivtv-fileops.c b/drivers/media/video/ivtv/ivtv-fileops.c
index d4275d2460c..38f052257f4 100644
--- a/drivers/media/video/ivtv/ivtv-fileops.c
+++ b/drivers/media/video/ivtv/ivtv-fileops.c
@@ -966,10 +966,6 @@ static int ivtv_serialized_open(struct ivtv_stream *s, struct file *filp)
 		return -ENOMEM;
 	}
 	v4l2_fh_init(&item->fh, s->vdev);
-	if (s->type == IVTV_DEC_STREAM_TYPE_YUV ||
-	    s->type == IVTV_DEC_STREAM_TYPE_MPG) {
-		res = v4l2_event_alloc(&item->fh, 60);
-	}
 	if (res < 0) {
 		v4l2_fh_exit(&item->fh);
 		kfree(item);
diff --git a/drivers/media/video/ivtv/ivtv-ioctl.c b/drivers/media/video/ivtv/ivtv-ioctl.c
index ff75d07097b..3e5c090af11 100644
--- a/drivers/media/video/ivtv/ivtv-ioctl.c
+++ b/drivers/media/video/ivtv/ivtv-ioctl.c
@@ -1450,13 +1450,11 @@ static int ivtv_subscribe_event(struct v4l2_fh *fh, struct v4l2_event_subscripti
 	switch (sub->type) {
 	case V4L2_EVENT_VSYNC:
 	case V4L2_EVENT_EOS:
-		break;
 	case V4L2_EVENT_CTRL:
-		return v4l2_ctrl_subscribe_fh(fh, sub, 0);
+		return v4l2_event_subscribe(fh, sub, 0);
 	default:
 		return -EINVAL;
 	}
-	return v4l2_event_subscribe(fh, sub);
 }
 
 static int ivtv_log_status(struct file *file, void *fh)
diff --git a/drivers/media/video/omap3isp/ispccdc.c b/drivers/media/video/omap3isp/ispccdc.c
index 39d501bda63..67662470661 100644
--- a/drivers/media/video/omap3isp/ispccdc.c
+++ b/drivers/media/video/omap3isp/ispccdc.c
@@ -1691,7 +1691,7 @@ static int ccdc_subscribe_event(struct v4l2_subdev *sd, struct v4l2_fh *fh,
 	if (sub->type != V4L2_EVENT_OMAP3ISP_HS_VS)
 		return -EINVAL;
 
-	return v4l2_event_subscribe(fh, sub);
+	return v4l2_event_subscribe(fh, sub, OMAP3ISP_CCDC_NEVENTS);
 }
 
 static int ccdc_unsubscribe_event(struct v4l2_subdev *sd, struct v4l2_fh *fh,
@@ -2162,7 +2162,6 @@ static int ccdc_init_entities(struct isp_ccdc_device *ccdc)
 	sd->grp_id = 1 << 16;	/* group ID for isp subdevs */
 	v4l2_set_subdevdata(sd, ccdc);
 	sd->flags |= V4L2_SUBDEV_FL_HAS_EVENTS | V4L2_SUBDEV_FL_HAS_DEVNODE;
-	sd->nevents = OMAP3ISP_CCDC_NEVENTS;
 
 	pads[CCDC_PAD_SINK].flags = MEDIA_PAD_FL_SINK;
 	pads[CCDC_PAD_SOURCE_VP].flags = MEDIA_PAD_FL_SOURCE;
diff --git a/drivers/media/video/omap3isp/ispstat.c b/drivers/media/video/omap3isp/ispstat.c
index b44cb685236..808065948ac 100644
--- a/drivers/media/video/omap3isp/ispstat.c
+++ b/drivers/media/video/omap3isp/ispstat.c
@@ -1032,7 +1032,6 @@ static int isp_stat_init_entities(struct ispstat *stat, const char *name,
 	snprintf(subdev->name, V4L2_SUBDEV_NAME_SIZE, "OMAP3 ISP %s", name);
 	subdev->grp_id = 1 << 16;	/* group ID for isp subdevs */
 	subdev->flags |= V4L2_SUBDEV_FL_HAS_EVENTS | V4L2_SUBDEV_FL_HAS_DEVNODE;
-	subdev->nevents = STAT_NEVENTS;
 	v4l2_set_subdevdata(subdev, stat);
 
 	stat->pad.flags = MEDIA_PAD_FL_SINK;
@@ -1050,7 +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);
+	return v4l2_event_subscribe(fh, sub, STAT_NEVENTS);
 }
 
 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 b63fe2a17fc..a37e5bff434 100644
--- a/drivers/media/video/v4l2-ctrls.c
+++ b/drivers/media/video/v4l2-ctrls.c
@@ -1011,7 +1011,6 @@ static int handler_new_ref(struct v4l2_ctrl_handler *hdl,
 	   insertion is an O(1) operation. */
 	if (list_empty(&hdl->ctrl_refs) || id > node2id(hdl->ctrl_refs.prev)) {
 		list_add_tail(&new_ref->node, &hdl->ctrl_refs);
-		hdl->nr_of_refs++;
 		goto insert_in_hash;
 	}
 
@@ -2051,20 +2050,3 @@ void v4l2_ctrl_del_event(struct v4l2_ctrl *ctrl,
 	v4l2_ctrl_unlock(ctrl);
 }
 EXPORT_SYMBOL(v4l2_ctrl_del_event);
-
-int v4l2_ctrl_subscribe_fh(struct v4l2_fh *fh,
-			struct v4l2_event_subscription *sub, unsigned n)
-{
-	struct v4l2_ctrl_handler *hdl = fh->ctrl_handler;
-	int ret = 0;
-
-	if (!ret) {
-		if (hdl->nr_of_refs * 2 > n)
-			n = hdl->nr_of_refs * 2;
-		ret = v4l2_event_alloc(fh, n);
-	}
-	if (!ret)
-		ret = v4l2_event_subscribe(fh, sub);
-	return ret;
-}
-EXPORT_SYMBOL(v4l2_ctrl_subscribe_fh);
diff --git a/drivers/media/video/v4l2-event.c b/drivers/media/video/v4l2-event.c
index dc68f608569..9e325dd3ce2 100644
--- a/drivers/media/video/v4l2-event.c
+++ b/drivers/media/video/v4l2-event.c
@@ -30,44 +30,11 @@
 #include <linux/sched.h>
 #include <linux/slab.h>
 
-static void v4l2_event_unsubscribe_all(struct v4l2_fh *fh);
-
-int v4l2_event_alloc(struct v4l2_fh *fh, unsigned int n)
-{
-	unsigned long flags;
-
-	while (fh->nallocated < n) {
-		struct v4l2_kevent *kev;
-
-		kev = kzalloc(sizeof(*kev), GFP_KERNEL);
-		if (kev == NULL)
-			return -ENOMEM;
-
-		spin_lock_irqsave(&fh->vdev->fh_lock, flags);
-		list_add_tail(&kev->list, &fh->free);
-		fh->nallocated++;
-		spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
-	}
-
-	return 0;
-}
-EXPORT_SYMBOL_GPL(v4l2_event_alloc);
-
-#define list_kfree(list, type, member)				\
-	while (!list_empty(list)) {				\
-		type *hi;					\
-		hi = list_first_entry(list, type, member);	\
-		list_del(&hi->member);				\
-		kfree(hi);					\
-	}
-
-void v4l2_event_free(struct v4l2_fh *fh)
+static unsigned sev_pos(const struct v4l2_subscribed_event *sev, unsigned idx)
 {
-	list_kfree(&fh->free, struct v4l2_kevent, list);
-	list_kfree(&fh->available, struct v4l2_kevent, list);
-	v4l2_event_unsubscribe_all(fh);
+	idx += sev->first;
+	return idx >= sev->elems ? idx - sev->elems : idx;
 }
-EXPORT_SYMBOL_GPL(v4l2_event_free);
 
 static int __v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event)
 {
@@ -84,11 +51,13 @@ static int __v4l2_event_dequeue(struct v4l2_fh *fh, struct v4l2_event *event)
 	WARN_ON(fh->navailable == 0);
 
 	kev = list_first_entry(&fh->available, struct v4l2_kevent, list);
-	list_move(&kev->list, &fh->free);
+	list_del(&kev->list);
 	fh->navailable--;
 
 	kev->event.pending = fh->navailable;
 	*event = kev->event;
+	kev->sev->first = sev_pos(kev->sev, 1);
+	kev->sev->in_use--;
 
 	spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
 
@@ -154,17 +123,24 @@ static void __v4l2_event_queue_fh(struct v4l2_fh *fh, const struct v4l2_event *e
 	fh->sequence++;
 
 	/* Do we have any free events? */
-	if (list_empty(&fh->free))
-		return;
+	if (sev->in_use == sev->elems) {
+		/* no, remove the oldest one */
+		kev = sev->events + sev_pos(sev, 0);
+		list_del(&kev->list);
+		sev->in_use--;
+		sev->first = sev_pos(sev, 1);
+		fh->navailable--;
+	}
 
 	/* Take one and fill it. */
-	kev = list_first_entry(&fh->free, struct v4l2_kevent, list);
+	kev = sev->events + sev_pos(sev, sev->in_use);
 	kev->event.type = ev->type;
 	kev->event.u = ev->u;
 	kev->event.id = ev->id;
 	kev->event.timestamp = *ts;
 	kev->event.sequence = fh->sequence;
-	list_move_tail(&kev->list, &fh->available);
+	sev->in_use++;
+	list_add_tail(&kev->list, &fh->available);
 
 	fh->navailable++;
 
@@ -209,38 +185,39 @@ int v4l2_event_pending(struct v4l2_fh *fh)
 EXPORT_SYMBOL_GPL(v4l2_event_pending);
 
 int v4l2_event_subscribe(struct v4l2_fh *fh,
-			 struct v4l2_event_subscription *sub)
+			 struct v4l2_event_subscription *sub, unsigned elems)
 {
 	struct v4l2_subscribed_event *sev, *found_ev;
 	struct v4l2_ctrl *ctrl = NULL;
 	unsigned long flags;
+	unsigned i;
 
+	if (elems < 1)
+		elems = 1;
 	if (sub->type == V4L2_EVENT_CTRL) {
 		ctrl = v4l2_ctrl_find(fh->ctrl_handler, sub->id);
 		if (ctrl == NULL)
 			return -EINVAL;
 	}
 
-	sev = kzalloc(sizeof(*sev), GFP_KERNEL);
+	sev = kzalloc(sizeof(*sev) + sizeof(struct v4l2_kevent) * elems, GFP_KERNEL);
 	if (!sev)
 		return -ENOMEM;
+	for (i = 0; i < elems; i++)
+		sev->events[i].sev = sev;
+	sev->type = sub->type;
+	sev->id = sub->id;
+	sev->flags = sub->flags;
+	sev->fh = fh;
+	sev->elems = elems;
 
 	spin_lock_irqsave(&fh->vdev->fh_lock, flags);
-
 	found_ev = v4l2_event_subscribed(fh, sub->type, sub->id);
-	if (!found_ev) {
-		INIT_LIST_HEAD(&sev->list);
-		sev->type = sub->type;
-		sev->id = sub->id;
-		sev->fh = fh;
-		sev->flags = sub->flags;
-
+	if (!found_ev)
 		list_add(&sev->list, &fh->subscribed);
-	}
-
 	spin_unlock_irqrestore(&fh->vdev->fh_lock, flags);
 
-	/* v4l2_ctrl_add_fh uses a mutex, so do this outside the spin lock */
+	/* v4l2_ctrl_add_event uses a mutex, so do this outside the spin lock */
 	if (found_ev)
 		kfree(sev);
 	else if (ctrl)
@@ -250,7 +227,7 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
 }
 EXPORT_SYMBOL_GPL(v4l2_event_subscribe);
 
-static void v4l2_event_unsubscribe_all(struct v4l2_fh *fh)
+void v4l2_event_unsubscribe_all(struct v4l2_fh *fh)
 {
 	struct v4l2_event_subscription sub;
 	struct v4l2_subscribed_event *sev;
@@ -271,6 +248,7 @@ static void v4l2_event_unsubscribe_all(struct v4l2_fh *fh)
 			v4l2_event_unsubscribe(fh, &sub);
 	} while (sev);
 }
+EXPORT_SYMBOL_GPL(v4l2_event_unsubscribe_all);
 
 int v4l2_event_unsubscribe(struct v4l2_fh *fh,
 			   struct v4l2_event_subscription *sub)
diff --git a/drivers/media/video/v4l2-fh.c b/drivers/media/video/v4l2-fh.c
index 333b8c8f40d..122822d2b8b 100644
--- a/drivers/media/video/v4l2-fh.c
+++ b/drivers/media/video/v4l2-fh.c
@@ -37,9 +37,7 @@ void v4l2_fh_init(struct v4l2_fh *fh, struct video_device *vdev)
 	INIT_LIST_HEAD(&fh->list);
 	set_bit(V4L2_FL_USES_V4L2_FH, &fh->vdev->flags);
 	fh->prio = V4L2_PRIORITY_UNSET;
-
 	init_waitqueue_head(&fh->wait);
-	INIT_LIST_HEAD(&fh->free);
 	INIT_LIST_HEAD(&fh->available);
 	INIT_LIST_HEAD(&fh->subscribed);
 	fh->sequence = -1;
@@ -88,7 +86,7 @@ void v4l2_fh_exit(struct v4l2_fh *fh)
 {
 	if (fh->vdev == NULL)
 		return;
-	v4l2_event_free(fh);
+	v4l2_event_unsubscribe_all(fh);
 	fh->vdev = NULL;
 }
 EXPORT_SYMBOL_GPL(v4l2_fh_exit);
diff --git a/drivers/media/video/v4l2-subdev.c b/drivers/media/video/v4l2-subdev.c
index 3b67a858491..b7967c9dc4a 100644
--- a/drivers/media/video/v4l2-subdev.c
+++ b/drivers/media/video/v4l2-subdev.c
@@ -76,13 +76,6 @@ static int subdev_open(struct file *file)
 	}
 
 	v4l2_fh_init(&subdev_fh->vfh, vdev);
-
-	if (sd->flags & V4L2_SUBDEV_FL_HAS_EVENTS) {
-		ret = v4l2_event_alloc(&subdev_fh->vfh, sd->nevents);
-		if (ret)
-			goto err;
-	}
-
 	v4l2_fh_add(&subdev_fh->vfh);
 	file->private_data = &subdev_fh->vfh;
 #if defined(CONFIG_MEDIA_CONTROLLER)
diff --git a/drivers/media/video/vivi.c b/drivers/media/video/vivi.c
index 1b90713b44c..cc1cf6b1718 100644
--- a/drivers/media/video/vivi.c
+++ b/drivers/media/video/vivi.c
@@ -993,7 +993,7 @@ static int vidioc_subscribe_event(struct v4l2_fh *fh,
 {
 	switch (sub->type) {
 	case V4L2_EVENT_CTRL:
-		return v4l2_ctrl_subscribe_fh(fh, sub, 0);
+		return v4l2_event_subscribe(fh, sub, 0);
 	default:
 		return -EINVAL;
 	}
diff --git a/drivers/usb/gadget/uvc_v4l2.c b/drivers/usb/gadget/uvc_v4l2.c
index 55828705d85..52f8f9e513a 100644
--- a/drivers/usb/gadget/uvc_v4l2.c
+++ b/drivers/usb/gadget/uvc_v4l2.c
@@ -124,18 +124,12 @@ uvc_v4l2_open(struct file *file)
 	struct video_device *vdev = video_devdata(file);
 	struct uvc_device *uvc = video_get_drvdata(vdev);
 	struct uvc_file_handle *handle;
-	int ret;
 
 	handle = kzalloc(sizeof(*handle), GFP_KERNEL);
 	if (handle == NULL)
 		return -ENOMEM;
 
 	v4l2_fh_init(&handle->vfh, vdev);
-
-	ret = v4l2_event_alloc(&handle->vfh, 8);
-	if (ret < 0)
-		goto error;
-
 	v4l2_fh_add(&handle->vfh);
 
 	handle->device = &uvc->video;
@@ -143,10 +137,6 @@ uvc_v4l2_open(struct file *file)
 
 	uvc_function_connect(uvc);
 	return 0;
-
-error:
-	v4l2_fh_exit(&handle->vfh);
-	return ret;
 }
 
 static int
@@ -308,7 +298,7 @@ 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);
+		return v4l2_event_subscribe(&handle->vfh, arg, 2);
 	}
 
 	case VIDIOC_UNSUBSCRIBE_EVENT: