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Date: Mon, 15 Jan 2024 16:06:00 +0100
From: Sebastian Wick <sebastian.wick@redhat.com>
To: Arthur Grillo <arthurgrillo@riseup.net>
Cc: Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@gmail.com>,
	Haneen Mohammed <hamohammed.sa@gmail.com>,
	Harry Wentland <harry.wentland@amd.com>,
	Jonathan Corbet <corbet@lwn.net>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	=?iso-8859-1?Q?Ma=EDra?= Canal <mairacanal@riseup.net>,
	Melissa Wen <melissa.srw@gmail.com>,
	Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	linux-kernel@vger.kernel.org, dri-devel@lists.freedesktop.org,
	linux-doc@vger.kernel.org
Subject: Re: [PATCH v2 0/7] Add YUV formats to VKMS
Message-ID: <20240115150600.GC160656@toolbox>
References: <20240110-vkms-yuv-v2-0-952fcaa5a193@riseup.net>
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In-Reply-To: <20240110-vkms-yuv-v2-0-952fcaa5a193@riseup.net>

On Wed, Jan 10, 2024 at 02:44:00PM -0300, Arthur Grillo wrote:
> This patchset aims to add support for additional buffer YUV formats.
> More specifically, it adds support to:
> 
> Semi-planar formats:
> 
> - NV12
> - NV16
> - NV24
> - NV21
> - NV61
> - NV42
> 
> Planar formats:
> 
> - YUV440
> - YUV422
> - YUV444
> - YVU440
> - YVU422
> - YVU444
> 
> These formats have more than one plane, and most have chroma
> subsampling. These properties don't have support on VKMS, so I had to
> work on this before.
> 
> To ensure that the conversions from YUV to RGB are working, I wrote a
> KUnit test. As the work from Harry on creating KUnit tests on VKMS[1] is
> not yet merged, I took the setup part (Kconfig entry and .kunitfile)
> from it.
> 
> Furthermore, I couldn't find any sources with the conversion matrices,
> so I had to work out the values myself based on the ITU papers[2][3][4].
> So, I'm not 100% sure if the values are accurate. I'd appreciate some
> input if anyone has more knowledge in this area.

H.273 CICP [1] has concise descriptions of the required values for most
widely used formats and the colour python framework [2] also can be used
to quickly get to the desired information most of the time.

[1]: https://www.itu.int/rec/T-REC-H.273
[2]: https://www.colour-science.org/

> Also, I used two IGT tests to check if the formats were having a correct
> conversion (all with the --extended flag):
> 
> - kms_plane@pixel_format
> - kms_plane@pixel_format_source_clamping.
> 
> The nonsubsampled formats don't have support on IGT, so I sent a patch
> fixing this[5].
> 
> Currently, this patchset does not add those formats to the writeback, as
> it would require a rewrite of how the conversions are done (similar to
> what was done on a previous patch[6]). So, I would like to review this
> patchset before I start the work on this other part.
> 
> [1]: https://lore.kernel.org/all/20231108163647.106853-5-harry.wentland@amd.com/
> [2]: https://www.itu.int/rec/R-REC-BT.601-7-201103-I/en
> [3]: https://www.itu.int/rec/R-REC-BT.709-6-201506-I/en
> [4]: https://www.itu.int/rec/R-REC-BT.2020-2-201510-I/en
> [5]: https://lists.freedesktop.org/archives/igt-dev/2024-January/066937.html
> [6]: https://lore.kernel.org/dri-devel/20230414135151.75975-2-mcanal@igalia.com/
> 
> Signed-off-by: Arthur Grillo <arthurgrillo@riseup.net>
> ---
> Changes in v2:
> - Use EXPORT_SYMBOL_IF_KUNIT instead of including the .c test
>   file (Maxime)
> - Link to v1: https://lore.kernel.org/r/20240105-vkms-yuv-v1-0-34c4cd3455e0@riseup.net
> 
> ---
> Arthur Grillo (7):
>       drm/vkms: Use drm_frame directly
>       drm/vkms: Add support for multy-planar framebuffers
>       drm/vkms: Add range and encoding properties to pixel_read function
>       drm/vkms: Add chroma subsampling
>       drm/vkms: Add YUV support
>       drm/vkms: Drop YUV formats TODO
>       drm/vkms: Create KUnit tests for YUV conversions
> 
>  Documentation/gpu/vkms.rst                    |   3 +-
>  drivers/gpu/drm/vkms/Kconfig                  |  15 ++
>  drivers/gpu/drm/vkms/Makefile                 |   1 +
>  drivers/gpu/drm/vkms/tests/.kunitconfig       |   4 +
>  drivers/gpu/drm/vkms/tests/Makefile           |   3 +
>  drivers/gpu/drm/vkms/tests/vkms_format_test.c | 156 ++++++++++++++++
>  drivers/gpu/drm/vkms/vkms_drv.h               |   6 +-
>  drivers/gpu/drm/vkms/vkms_formats.c           | 247 ++++++++++++++++++++++----
>  drivers/gpu/drm/vkms/vkms_formats.h           |   9 +
>  drivers/gpu/drm/vkms/vkms_plane.c             |  26 ++-
>  drivers/gpu/drm/vkms/vkms_writeback.c         |   5 -
>  11 files changed, 426 insertions(+), 49 deletions(-)
> ---
> base-commit: eeb8e8d9f124f279e80ae679f4ba6e822ce4f95f
> change-id: 20231226-vkms-yuv-6f7859f32df8
> 
> Best regards,
> -- 
> Arthur Grillo <arthurgrillo@riseup.net>
>