linux-kernel - Re: [PATCH v7 02/22] drm: Add new general DRM property "color format"

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Message-ID: <6318997.lOV4Wx5bFT@workhorse>
Date: Fri, 06 Feb 2026 16:26:56 +0100
From: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
To: Maxime Ripard <mripard@...nel.org>
Cc: Harry Wentland <harry.wentland@....com>, Leo Li <sunpeng.li@....com>,
 Rodrigo Siqueira <siqueira@...lia.com>,
 Alex Deucher <alexander.deucher@....com>,
 Christian König <christian.koenig@....com>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Thomas Zimmermann <tzimmermann@...e.de>,
 Andrzej Hajda <andrzej.hajda@...el.com>,
 Neil Armstrong <neil.armstrong@...aro.org>, Robert Foss <rfoss@...nel.org>,
 Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
 Jonas Karlman <jonas@...boo.se>, Jernej Skrabec <jernej.skrabec@...il.com>,
 Sandy Huang <hjc@...k-chips.com>,
 Heiko Stübner <heiko@...ech.de>,
 Andy Yan <andy.yan@...k-chips.com>,
 Jani Nikula <jani.nikula@...ux.intel.com>,
 Rodrigo Vivi <rodrigo.vivi@...el.com>,
 Joonas Lahtinen <joonas.lahtinen@...ux.intel.com>,
 Tvrtko Ursulin <tursulin@...ulin.net>, Dmitry Baryshkov <lumag@...nel.org>,
 Sascha Hauer <s.hauer@...gutronix.de>, Rob Herring <robh@...nel.org>,
 Jonathan Corbet <corbet@....net>, kernel@...labora.com,
 amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-rockchip@...ts.infradead.org, intel-gfx@...ts.freedesktop.org,
 intel-xe@...ts.freedesktop.org, linux-doc@...r.kernel.org,
 Andri Yngvason <andri@...vason.is>, Werner Sembach <wse@...edocomputers.com>,
 Marius Vlad <marius.vlad@...labora.com>
Subject: Re: [PATCH v7 02/22] drm: Add new general DRM property "color format"

Hello,

On Friday, 6 February 2026 15:05:08 Central European Standard Time Maxime Ripard wrote:
> Hi,
> 
> On Wed, Jan 21, 2026 at 03:45:09PM +0100, Nicolas Frattaroli wrote:
> > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> > index 7eaec37ae1c7..b5604dca728a 100644
> > --- a/include/drm/drm_connector.h
> > +++ b/include/drm/drm_connector.h
> > @@ -556,6 +556,16 @@ enum drm_colorspace {
> >  	DRM_MODE_COLORIMETRY_COUNT
> >  };
> >  
> > +enum drm_color_format {
> > +	DRM_COLOR_FORMAT_AUTO			= 0,
> > +	DRM_COLOR_FORMAT_RGB444			= BIT(0),
> > +	DRM_COLOR_FORMAT_YCBCR444		= BIT(1),
> > +	DRM_COLOR_FORMAT_YCBCR422		= BIT(2),
> > +	DRM_COLOR_FORMAT_YCBCR420		= BIT(3),
> > +};
> > +
> > +#define DRM_COLOR_FORMAT_COUNT 5
> > +
> 
> I don't really see a reason to expose an enum, with a bunch of values
> that are all mutually exclusive, as a bitmask. It's pretty inconsistent
> with most (all?) the other similar properties we have.
> 
> I appreciate you did that to avoid fixing up every driver using those
> values, but then maybe we don't have to? We could create a userspace
> facing enum, and convert to DRM_COLOR_FORMAT internally.

This is what the series did at v5 and earlier. IMHO it was kind of
counter-productive, because we then had two different things for the
same purpose, and some conversion logic between them. I think it's more
error prone to do it that way (think: mixing up the two), and doesn't
have a clear benefit. Just to give a picture of how bad things get:

1. we have the HDMI color format (aka "HDMI_COLORSPACE")
2. we have driver specific output color formats, e.g. the intel ones
3. we have DRM_COLOR_FORMAT
4. we have the bus formats (multiple per color format)
5. we have the DRM plane formats (again, multiple per color format)

Adding a sixth into the mix feels a bit bad because we'll then need to
justify why we should have another layer of switch-case statements.

Kind regards,
Nicolas Frattaroli

> 
> Maxime
>