Re: [PATCH 2/3] media: bttv: add back vbi hack

["Dr. David Alan Gilbert" <dave@treblig.org>]

* Hans Verkuil (hverkuil-cisco@xs4all.nl) wrote:
> The old (now removed) videobuf framework had an optional vbi hack where
> the sequence number of the frame counter was copied in the last 4 bytes
> of the buffer. This hack was active only for the read() interface
> (so not for streaming I/O), and it was enabled by bttv. This allowed
> applications that used read() for the VBI data to match it with the
> corresponding video frame.
> 
> When bttv was converted to vb2 this hack was forgotten, but some old
> applications rely on this.
> 
> So add this back, but this time in the bttv driver rather than in the
> vb2 framework.
> 
> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
> Fixes: b7ec3212a73a ("media: bttv: convert to vb2")

Thanks; this seems to fix the sequence number errors I was getting,
so:
Tested-by: Dr. David Alan Gilbert <dave@treblig.org>

> ---
>  drivers/media/pci/bt8xx/bttv-driver.c | 21 +++++++++++++++++++++
>  1 file changed, 21 insertions(+)
> 
> diff --git a/drivers/media/pci/bt8xx/bttv-driver.c b/drivers/media/pci/bt8xx/bttv-driver.c
> index 8e8c9dada67a..49a3dd70ec0f 100644
> --- a/drivers/media/pci/bt8xx/bttv-driver.c
> +++ b/drivers/media/pci/bt8xx/bttv-driver.c
> @@ -2772,6 +2772,27 @@ bttv_irq_wakeup_vbi(struct bttv *btv, struct bttv_buffer *wakeup,
>  		return;
>  	wakeup->vbuf.vb2_buf.timestamp = ktime_get_ns();
>  	wakeup->vbuf.sequence = btv->field_count >> 1;
> +
> +	/*
> +	 * Ugly hack for backwards compatibility.
> +	 * Some applications expect that the last 4 bytes of
> +	 * the VBI data contains the sequence number.
> +	 *
> +	 * This makes it possible to associate the VBI data
> +	 * with the video frame if you use read() to get the
> +	 * VBI data.
> +	 */
> +	if (vb2_fileio_is_active(wakeup->vbuf.vb2_buf.vb2_queue)) {
> +		u32 *vaddr = vb2_plane_vaddr(&wakeup->vbuf.vb2_buf, 0);
> +		unsigned long size =
> +			vb2_get_plane_payload(&wakeup->vbuf.vb2_buf, 0) / 4;
> +
> +		if (vaddr && size) {
> +			vaddr += size - 1;
> +			*vaddr = wakeup->vbuf.sequence;
> +		}
> +	}
> +
>  	vb2_buffer_done(&wakeup->vbuf.vb2_buf, state);
>  	if (btv->field_count == 0)
>  		btor(BT848_INT_VSYNC, BT848_INT_MASK);
> -- 
> 2.42.0
> 
-- 
 -----Open up your eyes, open up your mind, open up your code -------   
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