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From: Andri Yngvason <andri@yngvason.is>
Date: Wed, 10 Jan 2024 13:42:24 +0000
Message-ID: <CAFNQBQxnMh4aPfm+U8vEfxoTdQ+FByfqwUUDnMTzgkrW2+ZZqw@mail.gmail.com>
Subject: Re: [PATCH 5/7] drm/uAPI: Add "preferred color format" drm property
 as setting for userspace
To: Werner Sembach <wse@tuxedocomputers.com>
Cc: Maxime Ripard <mripard@kernel.org>, 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>
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mi=C3=B0., 10. jan. 2024 kl. 13:09 skrifa=C3=B0i Werner Sembach <wse@tuxedo=
computers.com>:
>
> Hi,
>
> Am 10.01.24 um 11:11 schrieb Andri Yngvason:
> > Hi,
> >
> > mi=C3=B0., 10. jan. 2024 kl. 09:27 skrifa=C3=B0i 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 l=
ook
> >>> better with rgb and some with ycbcr444.
> >> I looked at the patch and I couldn't find what is supposed to happen i=
f
> >> you set it to something else than auto, and the driver can't match tha=
t.
> >> 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 se=
nt to
> the LKML because I got discouraged by this:
> https://lore.kernel.org/dri-devel/20210623102923.70877c1a@eldfell/

Well, I've implemented this for sway and wlroots now and Simon has
reacted positively, so this does appear likely to end up as a feature
in wlroots based compositors.

>
> 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.
>

You can send the patches to me if you want and I can see if they're
useful. I'm really only interested in the color format part though.
Alternatively, you can continue your work and post it to LKML and I
can focus on the userspace side and testing. By the way, I have an
HDMI analyzer that can tell me the actual color format.

Thanks,
Andri