Subject: Re: [PATCH v3 3/3] media: sun6i-csi: capture: Support MC-centric format enumeration

From: Paul Kocialkowski <[email-masked]>
Date: Sun, 17 May 2026 23:48:08 +0200

Hi Arash,

Le Sat 09 May 26, 08:39, Arash Golgol a écrit :
> Extend vidioc_enum_fmt to support MC-centric enumeration by filtering
> pixel formats based on the provided mbus code. Advertise MC I/O support
> on the video device to reflect its intended usage within a media graph.

There is one (important) thing I overlooked last time: the list of
direct matches between mbus code and pixelformat only covers some of the
formats that the driver supports, but not all of them.

This is reflected in sun6i_csi_capture_link_validate, where we check
that a given mbus format set on the bridge is compatible with the
pixelformat set on the capture side.

I think we essentially have to extract that validation logic into a new
helper and then use it against all supported pixel formats for a given
mbus code to find out if that pixel format should be returned or not.
So it also means that multiple pixel formats can be supported for a given
mbus format.

A typical example of this would be MEDIA_BUS_FMT_YUYV8_2X8 than can be
stored to either YUYV (raw mode), NV16/YUV422 (YUV mode, no resampling) or
NV12/YUV420 (YUV mode, 422 -> 420 resampling).

You're welcome to give it a try if you'd like or I could take a look at
this myself.

Also the first comment after the sun6i_csi_capture_format_matches
declaration should be "YUV422", not "YUV420" (would be good to fix it
while touching these parts).

All the best,

Paul

> Signed-off-by: Arash Golgol <[email-masked]>
> Reviewed-by: Laurent Pinchart <[email-masked]>
> ---
> Changes in v3:
>  - No change
>  - Link to v2: https://patchwork.kernel.org/project/linux-media/patch/[email-masked]/
> 
> Changes in v2:
>  - Return pixelformat directly instead of a pointer
>  - Link to v1: https://patchwork.kernel.org/project/linux-media/patch/[email-masked]/
> 
>  .../sunxi/sun6i-csi/sun6i_csi_capture.c       | 39 +++++++++++++++++--
>  1 file changed, 36 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi_capture.c b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi_capture.c
> index f788b4234673..5737ebaa7297 100644
> --- a/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi_capture.c
> +++ b/drivers/media/platform/sunxi/sun6i-csi/sun6i_csi_capture.c
> @@ -327,6 +327,22 @@ static bool sun6i_csi_capture_format_match(u32 pixelformat, u32 mbus_code)
>  	return false;
>  }
>  
> +static u32 sun6i_csi_capture_pixelformat_find(u32 mbus_code)
> +{
> +	unsigned int i;
> +
> +	for (i = 0; i < ARRAY_SIZE(sun6i_csi_capture_format_matches); i++) {
> +		const struct sun6i_csi_capture_format_match *match =
> +			&sun6i_csi_capture_format_matches[i];
> +
> +		if (match->mbus_code == mbus_code)
> +			return match->pixelformat;
> +	}
> +
> +	/* Valid fourcc is non-zero. */
> +	return 0;
> +}
> +
>  /* Capture */
>  
>  static void
> @@ -729,11 +745,27 @@ static int sun6i_csi_capture_enum_fmt(struct file *file, void *priv,
>  				      struct v4l2_fmtdesc *fmtdesc)
>  {
>  	u32 index = fmtdesc->index;
> +	u32 mbus_code = fmtdesc->mbus_code;
> +	u32 pixelformat;
> +
> +	/* MC-centric or Video-node-centric */
> +	if (mbus_code) {
> +		/* There is only one pixelformat for a mbus_code. */
> +		if (index)
> +			return -EINVAL;
> +
> +		pixelformat = sun6i_csi_capture_pixelformat_find(mbus_code);
> +	} else {
> +		if (index >= ARRAY_SIZE(sun6i_csi_capture_formats))
> +			return -EINVAL;
> +
> +		pixelformat = sun6i_csi_capture_formats[index].pixelformat;
> +	}
>  
> -	if (index >= ARRAY_SIZE(sun6i_csi_capture_formats))
> +	if (!pixelformat)
>  		return -EINVAL;
>  
> -	fmtdesc->pixelformat = sun6i_csi_capture_formats[index].pixelformat;
> +	fmtdesc->pixelformat = pixelformat;
>  
>  	return 0;
>  }
> @@ -1065,7 +1097,8 @@ int sun6i_csi_capture_setup(struct sun6i_csi_device *csi_dev)
>  
>  	strscpy(video_dev->name, SUN6I_CSI_CAPTURE_NAME,
>  		sizeof(video_dev->name));
> -	video_dev->device_caps = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING;
> +	video_dev->device_caps = V4L2_CAP_VIDEO_CAPTURE | V4L2_CAP_STREAMING |
> +				 V4L2_CAP_IO_MC;
>  	video_dev->vfl_dir = VFL_DIR_RX;
>  	video_dev->release = video_device_release_empty;
>  	video_dev->fops = &sun6i_csi_capture_fops;
> -- 
> 2.34.1
> 

-- 
Paul Kocialkowski,

Independent contractor - sys-base - https://www.sys-base.io/
Free software developer - https://www.paulk.fr/

Expert in multimedia, graphics and embedded hardware support with Linux.