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

From: Nicolas Frattaroli <nicolas.frattaroli@collabora.com>
To: Maxime Ripard <mripard@kernel.org>
Cc: "Harry Wentland" <harry.wentland@amd.com>,
	"Leo Li" <sunpeng.li@amd.com>,
	"Rodrigo Siqueira" <siqueira@igalia.com>,
	"Alex Deucher" <alexander.deucher@amd.com>,
	"Christian König" <christian.koenig@amd.com>,
	"David Airlie" <airlied@gmail.com>,
	"Simona Vetter" <simona@ffwll.ch>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"Andrzej Hajda" <andrzej.hajda@intel.com>,
	"Neil Armstrong" <neil.armstrong@linaro.org>,
	"Robert Foss" <rfoss@kernel.org>,
	"Laurent Pinchart" <Laurent.pinchart@ideasonboard.com>,
	"Jonas Karlman" <jonas@kwiboo.se>,
	"Jernej Skrabec" <jernej.skrabec@gmail.com>,
	"Sandy Huang" <hjc@rock-chips.com>,
	"Heiko Stübner" <heiko@sntech.de>,
	"Andy Yan" <andy.yan@rock-chips.com>,
	"Jani Nikula" <jani.nikula@linux.intel.com>,
	"Rodrigo Vivi" <rodrigo.vivi@intel.com>,
	"Joonas Lahtinen" <joonas.lahtinen@linux.intel.com>,
	"Tvrtko Ursulin" <tursulin@ursulin.net>,
	kernel@collabora.com, amd-gfx@lists.freedesktop.org,
	dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
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	intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org
Subject: Re: [PATCH v4 07/10] drm/display: hdmi-state-helper: Act on color format DRM property
Date: Wed, 19 Nov 2025 13:41:18 +0100	[thread overview]
Message-ID: <7179523.lOV4Wx5bFT@workhorse> (raw)
In-Reply-To: <4wt5dbvseauo2bvi66ohtk445zsfjtpjwgvochwwlyk4uugcmy@5ubwtkxyy2ax>

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@collabora.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
> 