From: Marcus Glocker <marcus@nazgul.ch>
Subject: Re: sys/utvfu, sys/uvideo: clearify used timestamps
To: "Kirill A. Korinsky" <kirill@korins.ky>
Cc: tech@openbsd.org
Date: Tue, 25 Feb 2025 21:01:18 +0100

On Tue, Feb 25, 2025 at 07:11:49PM GMT, Kirill A. Korinsky wrote:

> tech@,
> 
> I'd like to clearify which timestamps have we used in v4l2 buffers in
> both drivers: utvfu and uvideo, which uses the same logic.
> 
> V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC and V4L2_BUF_FLAG_TSTAMP_SRC_EOF mean
> that timestamp has been taken from CLOCK_MONOTONIC when the last pixel
> of the frame was read from device, and not before the first one.
> 
> Thus, I had explicity unset V4L2_BUF_FLAG_TIMECODE bit if application
> requested it, because it isn't supported.
> 
> Ok?

ok mglocker@
 
> Index: sys/dev/usb/utvfu.c
> ===================================================================
> RCS file: /home/cvs/src/sys/dev/usb/utvfu.c,v
> diff -u -p -r1.22 utvfu.c
> --- sys/dev/usb/utvfu.c	15 Jan 2025 20:34:50 -0000	1.22
> +++ sys/dev/usb/utvfu.c	25 Feb 2025 17:45:24 -0000
> @@ -1378,7 +1378,12 @@ utvfu_mmap_queue(struct utvfu_softc *sc,
>  	sc->sc_mmap[i].v4l2_buf.bytesused = len;
>  
>  	/* timestamp it */
> -	getmicrotime(&sc->sc_mmap[i].v4l2_buf.timestamp);
> +	getmicrouptime(&sc->sc_mmap[i].v4l2_buf.timestamp);
> +	sc->sc_mmap[i].v4l2_buf.flags &= ~V4L2_BUF_FLAG_TIMESTAMP_MASK;
> +	sc->sc_mmap[i].v4l2_buf.flags |= V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> +	sc->sc_mmap[i].v4l2_buf.flags &= ~V4L2_BUF_FLAG_TSTAMP_SRC_MASK;
> +	sc->sc_mmap[i].v4l2_buf.flags |= V4L2_BUF_FLAG_TSTAMP_SRC_EOF;
> +	sc->sc_mmap[i].v4l2_buf.flags &= ~V4L2_BUF_FLAG_TIMECODE;
>  
>  	/* appropriately set/clear flags */
>  	sc->sc_mmap[i].v4l2_buf.flags &= ~V4L2_BUF_FLAG_QUEUED;
> Index: sys/dev/usb/uvideo.c
> ===================================================================
> RCS file: /home/cvs/src/sys/dev/usb/uvideo.c,v
> diff -u -p -r1.242 uvideo.c
> --- sys/dev/usb/uvideo.c	24 Feb 2025 21:24:54 -0000	1.242
> +++ sys/dev/usb/uvideo.c	25 Feb 2025 17:45:14 -0000
> @@ -2426,7 +2426,12 @@ uvideo_mmap_queue(struct uvideo_softc *s
>  	sc->sc_mmap[i].v4l2_buf.bytesused = len;
>  
>  	/* timestamp it */
> -	getmicrotime(&sc->sc_mmap[i].v4l2_buf.timestamp);
> +	getmicrouptime(&sc->sc_mmap[i].v4l2_buf.timestamp);
> +	sc->sc_mmap[i].v4l2_buf.flags &= ~V4L2_BUF_FLAG_TIMESTAMP_MASK;
> +	sc->sc_mmap[i].v4l2_buf.flags |= V4L2_BUF_FLAG_TIMESTAMP_MONOTONIC;
> +	sc->sc_mmap[i].v4l2_buf.flags &= ~V4L2_BUF_FLAG_TSTAMP_SRC_MASK;
> +	sc->sc_mmap[i].v4l2_buf.flags |= V4L2_BUF_FLAG_TSTAMP_SRC_EOF;
> +	sc->sc_mmap[i].v4l2_buf.flags &= ~V4L2_BUF_FLAG_TIMECODE;
>  
>  	/* forward error bit */
>  	sc->sc_mmap[i].v4l2_buf.flags &= ~V4L2_BUF_FLAG_ERROR;
>