Re: [PATCH 05/11] au0828: Fix green screen in analog

[Hans Verkuil <hverkuil+cisco@kernel.org>]

On 12/03/2026 22:35, Bradford Love wrote:
> When the driver was converted to VB2 the original function to fix
> green frame detection was removed and a default vb2 dqbuf function
> was used instead. This vb2 dqbuf function leads to green frames not
> being detected and correupting stream captures.
> 
> The vidioc_dqbuf function checks the greenscreen flag, and, if set
> resets the stream to discard the green frame and decode a real frame.
> 
> Signed-off-by: Bradford Love <brad@nextdimension.cc>
> ---
>  drivers/media/usb/au0828/au0828-video.c | 30 +++++++++++++++++++++++--
>  1 file changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/usb/au0828/au0828-video.c b/drivers/media/usb/au0828/au0828-video.c
> index fbaa542c8259..f65f15b1d92a 100644
> --- a/drivers/media/usb/au0828/au0828-video.c
> +++ b/drivers/media/usb/au0828/au0828-video.c
> @@ -1671,6 +1671,32 @@ static int vidioc_log_status(struct file *file, void *fh)
>  	return 0;
>  }
>  
> +static int vidioc_dqbuf(struct file *file, void *priv, struct v4l2_buffer *b)
> +{
> +	struct video_device *vdev = video_devdata(file);
> +	struct au0828_dev *dev = video_drvdata(file);
> +	int rc;
> +
> +	rc = check_dev(dev);
> +	if (rc < 0)
> +		return rc;
> +
> +	/* Workaround for a bug in the au0828 hardware design that
> +	 * sometimes results in the colorspace being inverted
> +	 */
> +	if (dev->greenscreen_detected == 1) {
> +		dprintk(1, "Detected green frame.  Resetting stream...\n");
> +		au0828_analog_stream_reset(dev);
> +		dev->greenscreen_detected = 0;
> +	}
> +
> +	if (vdev->queue->owner && vdev->queue->owner != file->private_data)
> +		return -EBUSY;
> +
> +	return vb2_dqbuf(vdev->queue, b, file->f_flags & O_NONBLOCK);

Please replace those last 4 lines with:

	return vb2_ioctl_dqbuf(file, priv, b);

It's cleaner that way.

Regards,

	Hans

> +}
> +
> +
>  void au0828_v4l2_suspend(struct au0828_dev *dev)
>  {
>  	struct urb *urb;
> @@ -1764,8 +1790,8 @@ static const struct v4l2_ioctl_ops video_ioctl_ops = {
>  	.vidioc_prepare_buf         = vb2_ioctl_prepare_buf,
>  	.vidioc_querybuf            = vb2_ioctl_querybuf,
>  	.vidioc_qbuf                = vb2_ioctl_qbuf,
> -	.vidioc_dqbuf               = vb2_ioctl_dqbuf,
> -	.vidioc_expbuf               = vb2_ioctl_expbuf,
> +	.vidioc_dqbuf               = vidioc_dqbuf,
> +	.vidioc_expbuf              = vb2_ioctl_expbuf,
>  
>  	.vidioc_s_std               = vidioc_s_std,
>  	.vidioc_g_std               = vidioc_g_std,