linux-kernel - [PATCH v1] doc: media: Document MM21 tiled format

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Message-Id: <20220221191202.805745-1-nicolas.dufresne@collabora.com>
Date:   Mon, 21 Feb 2022 14:12:01 -0500
From:   Nicolas Dufresne <nicolas.dufresne@...labora.com>
To:     Mauro Carvalho Chehab <mchehab@...nel.org>
Cc:     kernel@...labora.com, yunfei.dong@...iatek.com,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 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@...labora.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(-)

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