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 23:58:13 +0200

Hi again,

Le Sun 17 May 26, 23:48, Paul Kocialkowski a écrit :
> 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.

I just found this old series I never follow-up on which does pretty much
exactly that, along with additions to v4l2_format_info.

https://patchwork.kernel.org/project/linux-media/list/?series=733589&archive=both

If you don't mind I will just pick up this work based on my earlier
series directly.

All the best,

Paul

> 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.

-- 
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.