linux-kernel - Re: [PATCH 5/7] drm/uAPI: Add "preferred color format" drm property as setting for userspace

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Date: Wed, 10 Jan 2024 10:11:32 +0000
From: Andri Yngvason <andri@...vason.is>
To: Maxime Ripard <mripard@...nel.org>
Cc: Harry Wentland <harry.wentland@....com>, Leo Li <sunpeng.li@....com>, 
	Rodrigo Siqueira <Rodrigo.Siqueira@....com>, Alex Deucher <alexander.deucher@....com>, 
	Christian König <christian.koenig@....com>, 
	"Pan, Xinhui" <Xinhui.Pan@....com>, David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Thomas Zimmermann <tzimmermann@...e.de>, 
	Jani Nikula <jani.nikula@...ux.intel.com>, 
	Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>, Rodrigo Vivi <rodrigo.vivi@...el.com>, 
	Tvrtko Ursulin <tvrtko.ursulin@...ux.intel.com>, amd-gfx@...ts.freedesktop.org, 
	dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org, 
	intel-gfx@...ts.freedesktop.org, Simon Ser <contact@...rsion.fr>, 
	Werner Sembach <wse@...edocomputers.com>, Dan Carpenter <dan.carpenter@...cle.com>
Subject: Re: [PATCH 5/7] drm/uAPI: Add "preferred color format" drm property
 as setting for userspace

Hi,

mið., 10. jan. 2024 kl. 09:27 skrifaði Maxime Ripard <mripard@...nel.org>:
> On Tue, Jan 09, 2024 at 06:11:02PM +0000, Andri Yngvason wrote:
> > From: Werner Sembach <wse@...edocomputers.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.

Thanks,
Andri