Hi Ricardo,
Thank you for the patch.
On Fri, Oct 20, 2023 at 06:41:45AM +0000, Ricardo Ribalda wrote:
> Add support for the frame_sync event, so user-space can become aware
> earlier of new frames.
>
> Suggested-by: Esker Wong <esker@xxxxxxxxxxxx>
> Tested-by: Esker Wong <esker@xxxxxxxxxxxx>
> Signed-off-by: Ricardo Ribalda <ribalda@xxxxxxxxxxxx>
> ---
> We have measured a latency of around 30msecs between frame sync
> and dqbuf.
Not surprising, especially for large resolutions. I'm curious though,
what do you use this event for ?
> ---
> drivers/media/usb/uvc/uvc_v4l2.c | 2 ++
> drivers/media/usb/uvc/uvc_video.c | 8 +++++++-
> 2 files changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/media/usb/uvc/uvc_v4l2.c b/drivers/media/usb/uvc/uvc_v4l2.c
> index f4988f03640a..9f3fb5fd2375 100644
> --- a/drivers/media/usb/uvc/uvc_v4l2.c
> +++ b/drivers/media/usb/uvc/uvc_v4l2.c
> @@ -1352,6 +1352,8 @@ static int uvc_ioctl_subscribe_event(struct v4l2_fh *fh,
> switch (sub->type) {
> case V4L2_EVENT_CTRL:
> return v4l2_event_subscribe(fh, sub, 0, &uvc_ctrl_sub_ev_ops);
> + case V4L2_EVENT_FRAME_SYNC:
> + return v4l2_event_subscribe(fh, sub, 0, NULL);
> default:
> return -EINVAL;
> }
> diff --git a/drivers/media/usb/uvc/uvc_video.c b/drivers/media/usb/uvc/uvc_video.c
> index 28dde08ec6c5..1d4b4807b005 100644
> --- a/drivers/media/usb/uvc/uvc_video.c
> +++ b/drivers/media/usb/uvc/uvc_video.c
> @@ -1073,9 +1073,15 @@ static int uvc_video_decode_start(struct uvc_streaming *stream,
> * that discontinuous sequence numbers always indicate lost frames.
> */
> if (stream->last_fid != fid) {
> - stream->sequence++;
> + struct v4l2_event event = {
> + .type = V4L2_EVENT_FRAME_SYNC,
> + .u.frame_sync.frame_sequence = ++stream->sequence,
Extra space before ++.
It's easy to miss the ++ there when reading the code, would the
following be more readable ?
struct v4l2_event event = {
.type = V4L2_EVENT_FRAME_SYNC,
};
stream->sequence++;
if (stream->sequence)
uvc_video_stats_update(stream);
.u.frame_sync.frame_sequence = stream->sequence;
v4l2_event_queue(&stream->vdev, &event);
> + };
> +
> if (stream->sequence)
> uvc_video_stats_update(stream);
> +
> + v4l2_event_queue(&stream->vdev, &event);
> }
>
> uvc_video_clock_decode(stream, buf, data, len);
>
> ---
> base-commit: ce55c22ec8b223a90ff3e084d842f73cfba35588
> change-id: 20231020-uvc-event-d3d1bbbdcb2f
--
Regards,
Laurent Pinchart
