linux-kernel - Re: [PATCH v4 07/10] drm/display: hdmi-state-helper: Act on color format DRM property

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Message-ID: <nbrdnftrsybpowsu2f6me3jumdeodg45x4quouzlzd5jo7xrux@4pny3aiverzn>
Date: Thu, 20 Nov 2025 16:54:25 +0100
From: Maxime Ripard <mripard@...nel.org>
To: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
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>, 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
Subject: Re: [PATCH v4 07/10] drm/display: hdmi-state-helper: Act on color
 format DRM property

On Wed, Nov 19, 2025 at 01:41:18PM +0100, Nicolas Frattaroli wrote:
> On Wednesday, 19 November 2025 10:09:12 Central European Standard Time Maxime Ripard wrote:
> > Hi,
> > 
> > On Mon, Nov 17, 2025 at 08:11:51PM +0100, Nicolas Frattaroli wrote:
> > > With the introduction of the "color format" DRM property, which allows
> > > userspace to request a specific color format, the HDMI state helper
> > > should implement this.
> > > 
> > > Implement it by checking whether the property is set and set to
> > > something other than auto. If so, pass the requested color format, and
> > > otherwise set RGB.
> > > 
> > > Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
> > > ---
> > >  drivers/gpu/drm/display/drm_hdmi_state_helper.c | 8 +++++++-
> > >  1 file changed, 7 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/gpu/drm/display/drm_hdmi_state_helper.c b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> > > index a561f124be99..add0d51fce33 100644
> > > --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> > > +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> > > @@ -650,9 +650,15 @@ hdmi_compute_config(const struct drm_connector *connector,
> > >  				       conn_state->max_bpc,
> > >  				       8, connector->max_bpc);
> > >  	int ret;
> > > +	enum hdmi_colorspace hdmi_colorspace;
> > > +
> > > +	if (conn_state->color_format && conn_state->color_format != DRM_COLOR_FORMAT_AUTO)
> > > +		hdmi_colorspace = color_format_to_hdmi_colorspace(conn_state->color_format);
> > > +	else
> > > +		hdmi_colorspace = HDMI_COLORSPACE_RGB;
> > >  
> > >  	ret = hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc,
> > > -				      HDMI_COLORSPACE_RGB);
> > > +				      hdmi_colorspace);
> > 
> > I don't think we want the fallback to yuv420 for anything but auto, so
> 
> Okay. Changing all the non-hdmi-state-helper drivers (amdgpu, i915)
> to do this as well would require some more work however, especially
> in the case of amdgpu where the code flow is not always obvious.

Yeah, I think we want to be consistent here, the whole point of the HDMI
state helpers was to be consistently consistent with Intel's behaviour
anyway :)

> > I'd rather have something like
> > 
> > if (conn_state->color_format != DRM_COLOR_FORMAT_AUTO)
> >    return hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc,
> >                                   color_format_to_hdmi_colorspace(conn_state->color_format))
> > 
> > We'll also need unit tests.
> 
> Sure, am I guessing correctly that they'd go in
> drm_hdmi_state_helper_test.c?

Yes

Maxime

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