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

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Message-ID: <7179523.lOV4Wx5bFT@workhorse>
Date: Wed, 19 Nov 2025 13:41:18 +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>, 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 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.

> 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?

> Maxime
>