Hi Hans,
Thanks for the patch.
On Tuesday 14 June 2011 17:22:29 Hans Verkuil wrote:
> From: Hans Verkuil <hans.verk...@cisco.com>
>
> When the event queue for a subscribed event is full, then the oldest
> event is dropped. It would be nice if the contents of that oldest
> event could be merged with the next-oldest. That way no information is
> lost, only intermediate steps are lost.
>
> This patch adds an optional merge function that will be called to do
> this job and implements it for the control event.
>
> Signed-off-by: Hans Verkuil <hans.verk...@cisco.com>
> ---
> drivers/media/video/v4l2-event.c | 27 ++++++++++++++++++++++++++-
> include/media/v4l2-event.h | 5 +++++
> 2 files changed, 31 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/media/video/v4l2-event.c
> b/drivers/media/video/v4l2-event.c index 9e325dd..aeec2d5 100644
> --- a/drivers/media/video/v4l2-event.c
> +++ b/drivers/media/video/v4l2-event.c
> @@ -113,6 +113,7 @@ static void __v4l2_event_queue_fh(struct v4l2_fh *fh,
> const struct v4l2_event *e {
> struct v4l2_subscribed_event *sev;
> struct v4l2_kevent *kev;
> + bool copy_payload = true;
>
> /* Are we subscribed? */
> sev = v4l2_event_subscribed(fh, ev->type, ev->id);
> @@ -130,12 +131,23 @@ static void __v4l2_event_queue_fh(struct v4l2_fh *fh,
> const struct v4l2_event *e sev->in_use--;
> sev->first = sev_pos(sev, 1);
> fh->navailable--;
> + if (sev->merge) {
> + if (sev->elems == 1) {
> + sev->merge(&kev->event, ev, &kev->event);
> + copy_payload = false;
> + } else {
> + struct v4l2_kevent *second_oldest =
> + sev->events + sev_pos(sev, 0);
> + sev->merge(&second_oldest->event,
> &second_oldest->event, &kev-
>event);
> + }
> + }
> }
>
> /* Take one and fill it. */
> kev = sev->events + sev_pos(sev, sev->in_use);
> kev->event.type = ev->type;
> - kev->event.u = ev->u;
> + if (copy_payload)
> + kev->event.u = ev->u;
> kev->event.id = ev->id;
> kev->event.timestamp = *ts;
> kev->event.sequence = fh->sequence;
> @@ -184,6 +196,17 @@ int v4l2_event_pending(struct v4l2_fh *fh)
> }
> EXPORT_SYMBOL_GPL(v4l2_event_pending);
>
> +static void ctrls_merge(struct v4l2_event *dst,
> + const struct v4l2_event *new,
> + const struct v4l2_event *old)
> +{
> + u32 changes = new->u.ctrl.changes | old->u.ctrl.changes;
> +
> + if (dst == old)
> + dst->u.ctrl = new->u.ctrl;
> + dst->u.ctrl.changes = changes;
> +}
> +
> int v4l2_event_subscribe(struct v4l2_fh *fh,
> struct v4l2_event_subscription *sub, unsigned elems)
> {
> @@ -210,6 +233,8 @@ int v4l2_event_subscribe(struct v4l2_fh *fh,
> sev->flags = sub->flags;
> sev->fh = fh;
> sev->elems = elems;
> + if (ctrl)
> + sev->merge = ctrls_merge;
>
> spin_lock_irqsave(&fh->vdev->fh_lock, flags);
> found_ev = v4l2_event_subscribed(fh, sub->type, sub->id);
> diff --git a/include/media/v4l2-event.h b/include/media/v4l2-event.h
> index 8d681e5..111b2bc 100644
> --- a/include/media/v4l2-event.h
> +++ b/include/media/v4l2-event.h
> @@ -55,6 +55,11 @@ struct v4l2_subscribed_event {
> struct v4l2_fh *fh;
> /* list node that hooks into the object's event list (if there is one)
> */
> struct list_head node;
> + /* Optional callback that can merge two events.
> + Note that 'dst' can be the same as either 'new' or 'old'. */
This can lead to various problems in drivers, if the code forgets that
changing dst will change new or old. Would it be possible to make it a two
arguments (dst, src) function ?
> + void (*merge)(struct v4l2_event *dst,
> + const struct v4l2_event *new,
> + const struct v4l2_event *old);
> /* the number of elements in the events array */
> unsigned elems;
> /* the index of the events containing the oldest available event */
--
Regards,
Laurent Pinchart
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