[v1] doc: media: Document MM21 tiled format

MM21 has been documented through two software implementation [0] in libyuv and
[2] GStreamer. This format is similar to other tiled format, though it uses
uneven tile sizes. The luma tiles are 16x32 while the chroma tile have a
subsampled size of 16x16. This is the uncompressed cousin of V4L2_PIX_FMT_MT21C
and shares its tiling pattern and alignment.

[0] https://chromium.googlesource.com/libyuv/libyuv/+/b4ddbaf549a1bf5572bf703fd2862d1eb7380c6a
[1] https://gitlab.freedesktop.org/gstreamer/gstreamer/-/commit/c9b127dae3af4b3fe78468e697cb491902425254

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
---
 .../userspace-api/media/v4l/pixfmt-reserved.rst   | 15 ++++-----------
 .../userspace-api/media/v4l/pixfmt-yuv-planar.rst |  6 ++++++
 2 files changed, 10 insertions(+), 11 deletions(-)

On Mon, Feb 21, 2022 at 02:12:01PM -0500, Nicolas Dufresne wrote:
> MM21 has been documented through two software implementation [0] in libyuv and
> [2] GStreamer. This format is similar to other tiled format, though it uses
> uneven tile sizes. The luma tiles are 16x32 while the chroma tile have a
> subsampled size of 16x16. This is the uncompressed cousin of V4L2_PIX_FMT_MT21C
> and shares its tiling pattern and alignment.
> 
> [0] https://chromium.googlesource.com/libyuv/libyuv/+/b4ddbaf549a1bf5572bf703fd2862d1eb7380c6a
> [1] https://gitlab.freedesktop.org/gstreamer/gstreamer/-/commit/c9b127dae3af4b3fe78468e697cb491902425254
> 
> Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>

Reviewed-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>

> ---
>  .../userspace-api/media/v4l/pixfmt-reserved.rst   | 15 ++++-----------
>  .../userspace-api/media/v4l/pixfmt-yuv-planar.rst |  6 ++++++
>  2 files changed, 10 insertions(+), 11 deletions(-)
> 
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst b/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
> index 2f2133b4cd9ce..cabfa34b7db5a 100644
> --- a/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-reserved.rst
> @@ -233,19 +233,12 @@ please make a proposal on the linux-media mailing list.
>  
>        - ``V4L2_PIX_FMT_MT21C``
>        - 'MT21'
> -      - Compressed two-planar YVU420 format used by Mediatek MT8173.
> -	The compression is lossless.
> -	It is an opaque intermediate format and the MDP hardware must be
> +      - Compressed two-planar YVU420 format used by Mediatek MT8173, MT8192,
> +        MT8195 and more. The compression is lossless. This format have
> +	similitude with ``V4L2_PIX_FMT_MM21`` in term of alignment and tiling.
> +	It remains an opaque intermediate format and the MDP hardware must be
>  	used to convert ``V4L2_PIX_FMT_MT21C`` to ``V4L2_PIX_FMT_NV12M``,
>  	``V4L2_PIX_FMT_YUV420M`` or ``V4L2_PIX_FMT_YVU420``.
> -    * .. _V4L2-PIX-FMT-MM21:
> -
> -      - ``V4L2_PIX_FMT_MM21``
> -      - 'MM21'
> -      - Non-compressed, tiled two-planar format used by Mediatek MT8183.
> -	This is an opaque intermediate format and the MDP3 hardware can be
> -	used to convert it to other formats.
> -
>  .. raw:: latex
>  
>      \normalsize
> diff --git a/Documentation/userspace-api/media/v4l/pixfmt-yuv-planar.rst b/Documentation/userspace-api/media/v4l/pixfmt-yuv-planar.rst
> index 3a09d93d405b2..570791fbc5c8b 100644
> --- a/Documentation/userspace-api/media/v4l/pixfmt-yuv-planar.rst
> +++ b/Documentation/userspace-api/media/v4l/pixfmt-yuv-planar.rst
> @@ -296,6 +296,12 @@ tiles linearly in memory. The line stride and image height must be
>  aligned to a multiple of 32. The layouts of the luma and chroma planes are
>  identical.
>  
> +``V4L2_PIX_FMT_MM21`` store luma pixel in 16x32 tiles, and chroma pixels
> +in 16x16 tiles. The line stride must be aligned to a multiple of 16 and the
> +image height must be aligned to a multiple of 32. The number of luma and chroma
> +tiles are identical, even though the tile size differ. The image is formed of
> +two non-contiguous planes.
> +
>  .. _nv12mt:
>  
>  .. kernel-figure:: nv12mt.svg
> -- 
> 2.35.1
>