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Message-ID: <92e20f9b-2cbf-4efe-b61b-989da0cc1668@tuxedocomputers.com>
Date: Wed, 10 Jan 2024 14:09:11 +0100
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Subject: Re: [PATCH 5/7] drm/uAPI: Add "preferred color format" drm property
 as setting for userspace
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To: Andri Yngvason <andri@yngvason.is>, Maxime Ripard <mripard@kernel.org>
Cc: Harry Wentland <harry.wentland@amd.com>, Leo Li <sunpeng.li@amd.com>,
 Rodrigo Siqueira <Rodrigo.Siqueira@amd.com>,
 Alex Deucher <alexander.deucher@amd.com>,
 =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
 "Pan, Xinhui" <Xinhui.Pan@amd.com>, David Airlie <airlied@gmail.com>,
 Daniel Vetter <daniel@ffwll.ch>,
 Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
 Thomas Zimmermann <tzimmermann@suse.de>,
 Jani Nikula <jani.nikula@linux.intel.com>,
 Joonas Lahtinen <joonas.lahtinen@linux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@intel.com>,
 Tvrtko Ursulin <tvrtko.ursulin@linux.intel.com>,
 amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org,
 linux-kernel@vger.kernel.org, intel-gfx@lists.freedesktop.org,
 Simon Ser <contact@emersion.fr>, Dan Carpenter <dan.carpenter@oracle.com>
References: <20240109181104.1670304-1-andri@yngvason.is>
 <20240109181104.1670304-6-andri@yngvason.is>
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 <CAFNQBQzijyE4wR34AOLM45m+ryx128igVKO9zPJ5-M3afFQMxQ@mail.gmail.com>
From: Werner Sembach <wse@tuxedocomputers.com>
In-Reply-To: <CAFNQBQzijyE4wR34AOLM45m+ryx128igVKO9zPJ5-M3afFQMxQ@mail.gmail.com>
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Hi,

Am 10.01.24 um 11:11 schrieb Andri Yngvason:
> Hi,
>
> mið., 10. jan. 2024 kl. 09:27 skrifaði Maxime Ripard <mripard@kernel.org>:
>> On Tue, Jan 09, 2024 at 06:11:02PM +0000, Andri Yngvason wrote:
>>> From: Werner Sembach <wse@tuxedocomputers.com>
>>>
>>> Add a new general drm property "preferred color format" which can be used
>>> by userspace to tell the graphic drivers to which color format to use.
>>>
>>> Possible options are:
>>>      - auto (default/current behaviour)
>>>      - rgb
>>>      - ycbcr444
>>>      - ycbcr422 (not supported by both amdgpu and i915)
>>>      - ycbcr420
>>>
>>> In theory the auto option should choose the best available option for the
>>> current setup, but because of bad internal conversion some monitors look
>>> better with rgb and some with ycbcr444.
>> I looked at the patch and I couldn't find what is supposed to happen if
>> you set it to something else than auto, and the driver can't match that.
>> Are we supposed to fallback to the "auto" behaviour, or are we suppose
>> to reject the mode entirely?
>>
>> The combination with the active output format property suggests the
>> former, but we should document it explicitly.
> It is also my understanding that it should fall back to the "auto"
> behaviour. I will add this to the documentation.

Yes, that was the intention, and then userspace can check, but it wasn't well 
received: https://gitlab.freedesktop.org/drm/amd/-/issues/476#note_964530

Actually a lot of the thoughts that went into the original patch set can be 
found in that topic.

There was another iteration of the patch set that I never finished and sent to 
the LKML because I got discouraged by this: 
https://lore.kernel.org/dri-devel/20210623102923.70877c1a@eldfell/

I can try to dig it up, but it is completely untested and I don't think I still 
have the respective TODO list anymore, so I don't know if it is a better or 
worst starting point than the last iteration I sent to the LKML.

Greetings

Werner

>
> Thanks,
> Andri