Re: [PATCH 1/2] usb: gadget: uvc: Switch to monotonic clock for buffer timestamps

From: Laurent Pinchart
Date: Fri Mar 28 2014 - 07:16:27 EST


Hi Hans,

On Friday 28 March 2014 09:50:42 Hans Verkuil wrote:
> On 03/23/2014 04:32 PM, Laurent Pinchart wrote:
> > The wall time clock isn't useful for applications as it can jump around
> > due to time adjustement. Switch to the monotonic clock.
> >
> > Signed-off-by: Laurent Pinchart <laurent.pinchart@xxxxxxxxxxxxxxxx>
> > ---
> >
> > drivers/usb/gadget/uvc_queue.c | 12 +++++-------
> > 1 file changed, 5 insertions(+), 7 deletions(-)
> >
> > diff --git a/drivers/usb/gadget/uvc_queue.c
> > b/drivers/usb/gadget/uvc_queue.c index 0bb5d50..d4561ba 100644
> > --- a/drivers/usb/gadget/uvc_queue.c
> > +++ b/drivers/usb/gadget/uvc_queue.c
> > @@ -364,6 +364,7 @@ static struct uvc_buffer *uvc_queue_next_buffer(struct
> > uvc_video_queue *queue,
> > struct uvc_buffer *buf)
> > {
> > struct uvc_buffer *nextbuf;
> > + struct timespec ts;
> >
> > if ((queue->flags & UVC_QUEUE_DROP_INCOMPLETE) &&
> > buf->length != buf->bytesused) {
> > @@ -379,14 +380,11 @@ static struct uvc_buffer
> > *uvc_queue_next_buffer(struct uvc_video_queue *queue,>
> > else
> > nextbuf = NULL;
> >
> > - /*
> > - * FIXME: with videobuf2, the sequence number or timestamp fields
> > - * are valid only for video capture devices and the UVC gadget
> > usually
> > - * is a video output device. Keeping these until the specs are clear
> > on
> > - * this aspect.
> > - */
> > + ktime_get_ts(&ts);
>
> Why not use the v4l2-common.c helper v4l2_get_timestamp()?

No reason at all. I'll fix that.

> > +
> > buf->buf.v4l2_buf.sequence = queue->sequence++;
> >
> > - do_gettimeofday(&buf->buf.v4l2_buf.timestamp);
> > + buf->buf.v4l2_buf.timestamp.tv_sec = ts.tv_sec;
> > + buf->buf.v4l2_buf.timestamp.tv_usec = ts.tv_nsec / NSEC_PER_USEC;
>
> You should also add:
>
> buf->buf.v4l2_buf.field = V4L2_FIELD_NONE;
>
> I noticed that that was never set, which is wrong.

Good point. Will be fixed in v2.

> > vb2_set_plane_payload(&buf->buf, 0, buf->bytesused);
> > vb2_buffer_done(&buf->buf, VB2_BUF_STATE_DONE);

--
Regards,

Laurent Pinchart

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