Re: [PATCH 06/10] media: Add B412 video format

[Hans Verkuil]

On 20/12/2022 04:11, Ming Qian wrote:
> B412 is a reversed RGB format with alpha channel last,
> 12 bits per component like ABGR32,
> expanded to 16bits.
> Data in the 12 high bits, zeros in the 4 low bits,
> arranged in little endian order.
> 
> Signed-off-by: Ming Qian <ming.qian@xxxxxxx>
> ---
>  Documentation/userspace-api/media/v4l/pixfmt-rgb.rst | 9 +++++++++
>  drivers/media/v4l2-core/v4l2-common.c                | 1 +
>  drivers/media/v4l2-core/v4l2-ioctl.c                 | 1 +
>  include/uapi/linux/videodev2.h                       | 1 +
>  4 files changed, 12 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-rgb.rst b/Documentation/userspace-api/media/v4l/pixfmt-rgb.rst
> index f7785c93292a..b9d1e48c0224 100644
> --- a/Documentation/userspace-api/media/v4l/pixfmt-rgb.rst
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-rgb.rst
> @@ -793,6 +793,15 @@ arranged in little endian order.
>        - G\ :sub:`15-4`
>        - R\ :sub:`15-4`
>        -
> +    * .. _V4L2-PIX-FMT-B412:
> +
> +      - ``V4L2_PIX_FMT_B412``
> +      - 'B412'
> +
> +      - B\ :sub:`15-4`
> +      - G\ :sub:`15-4`
> +      - R\ :sub:`15-4`
> +      - A\ :sub:`15-4`
>  
>  .. raw:: latex
>  
> diff --git a/drivers/media/v4l2-core/v4l2-common.c b/drivers/media/v4l2-core/v4l2-common.c
> index 0cc58abae562..5384648903a9 100644
> --- a/drivers/media/v4l2-core/v4l2-common.c
> +++ b/drivers/media/v4l2-core/v4l2-common.c
> @@ -253,6 +253,7 @@ const struct v4l2_format_info *v4l2_format_info(u32 format)
>  		{ .format = V4L2_PIX_FMT_RGB555,  .pixel_enc = V4L2_PIXEL_ENC_RGB, .mem_planes = 1, .comp_planes = 1, .bpp = { 2, 0, 0, 0 }, .hdiv = 1, .vdiv = 1 },
>  		{ .format = V4L2_PIX_FMT_BGR666,  .pixel_enc = V4L2_PIXEL_ENC_RGB, .mem_planes = 1, .comp_planes = 1, .bpp = { 4, 0, 0, 0 }, .hdiv = 1, .vdiv = 1 },
>  		{ .format = V4L2_PIX_FMT_B312,    .pixel_enc = V4L2_PIXEL_ENC_RGB, .mem_planes = 1, .comp_planes = 1, .bpp = { 6, 0, 0, 0 }, .hdiv = 1, .vdiv = 1 },
> +		{ .format = V4L2_PIX_FMT_B412,    .pixel_enc = V4L2_PIXEL_ENC_RGB, .mem_planes = 1, .comp_planes = 1, .bpp = { 8, 0, 0, 0 }, .hdiv = 1, .vdiv = 1 },
>  
>  		/* YUV packed formats */
>  		{ .format = V4L2_PIX_FMT_YUYV,    .pixel_enc = V4L2_PIXEL_ENC_YUV, .mem_planes = 1, .comp_planes = 1, .bpp = { 2, 0, 0, 0 }, .hdiv = 2, .vdiv = 1 },
> diff --git a/drivers/media/v4l2-core/v4l2-ioctl.c b/drivers/media/v4l2-core/v4l2-ioctl.c
> index 8c3d40d3acf5..8cb21024bd96 100644
> --- a/drivers/media/v4l2-core/v4l2-ioctl.c
> +++ b/drivers/media/v4l2-core/v4l2-ioctl.c
> @@ -1299,6 +1299,7 @@ static void v4l_fill_fmtdesc(struct v4l2_fmtdesc *fmt)
>  	case V4L2_PIX_FMT_RGBA32:	descr = "32-bit RGBA 8-8-8-8"; break;
>  	case V4L2_PIX_FMT_RGBX32:	descr = "32-bit RGBX 8-8-8-8"; break;
>  	case V4L2_PIX_FMT_B312:		descr = "12-bit Depth BGR"; break;
> +	case V4L2_PIX_FMT_B412:		descr = "12-bit Depth BGRA"; break;
>  	case V4L2_PIX_FMT_GREY:		descr = "8-bit Greyscale"; break;
>  	case V4L2_PIX_FMT_Y4:		descr = "4-bit Greyscale"; break;
>  	case V4L2_PIX_FMT_Y6:		descr = "6-bit Greyscale"; break;
> diff --git a/include/uapi/linux/videodev2.h b/include/uapi/linux/videodev2.h
> index c67f895210de..a26ff16a52c8 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -579,6 +579,7 @@ struct v4l2_pix_format {
>  
>  /* RGB formats (6 or 8 bytes per pixel) */
>  #define V4L2_PIX_FMT_B312    v4l2_fourcc('B', '3', '1', '2') /* 48  BGR 12-bit per component */
> +#define V4L2_PIX_FMT_B412    v4l2_fourcc('B', '4', '1', '2') /* 64  BGRA 12-bit per component */

This would be ABGR32_12, to correspond with the 8 bit ABGR32.
Unfortunately, that define has a terrible mismatch with the actual component
order (alpha comes last in memory, not first as the name suggests).

It would be nice to be able to fix this, but I think that would be even
more confusing.

Regards,

	Hans

>  
>  /* Grey formats */
>  #define V4L2_PIX_FMT_GREY    v4l2_fourcc('G', 'R', 'E', 'Y') /*  8  Greyscale     */