linux-kernel - Re: [PATCH v5 04/17] drm/bridge: Act on the DRM color format property

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Message-ID: <20251209-smart-oarfish-of-wind-0c1c8b@houat>
Date: Tue, 9 Dec 2025 15:27:28 +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>, 
	Dmitry Baryshkov <lumag@...nel.org>, Sascha Hauer <s.hauer@...gutronix.de>, 
	Rob Herring <robh@...nel.org>, 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 v5 04/17] drm/bridge: Act on the DRM color format property

Hi,

On Fri, Nov 28, 2025 at 10:05:40PM +0100, Nicolas Frattaroli wrote:
> The new DRM color format property allows userspace to request a specific
> color format on a connector. In turn, this fills the connector state's
> color_format member to switch color formats.
> 
> Make drm_bridges consider the color_format set in the connector state
> during the atomic bridge check. Specifically, reject any output bus
> formats that do not correspond to the requested color format.
> 
> Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
> ---
>  drivers/gpu/drm/drm_bridge.c | 45 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 45 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_bridge.c b/drivers/gpu/drm/drm_bridge.c
> index 8f355df883d8..8aac9747f35e 100644
> --- a/drivers/gpu/drm/drm_bridge.c
> +++ b/drivers/gpu/drm/drm_bridge.c
> @@ -1052,6 +1052,47 @@ static int select_bus_fmt_recursive(struct drm_bridge *first_bridge,
>  	return ret;
>  }
>  
> +static bool __pure bus_format_is_color_fmt(u32 bus_fmt, enum drm_color_format fmt)
> +{
> +	if (fmt == DRM_COLOR_FORMAT_AUTO)
> +		return true;
> +
> +	switch (bus_fmt) {
> +	case MEDIA_BUS_FMT_FIXED:
> +		return true;
> +	case MEDIA_BUS_FMT_RGB888_1X24:
> +	case MEDIA_BUS_FMT_RGB101010_1X30:
> +	case MEDIA_BUS_FMT_RGB121212_1X36:
> +	case MEDIA_BUS_FMT_RGB161616_1X48:
> +		return fmt == DRM_COLOR_FORMAT_RGB444;
> +	case MEDIA_BUS_FMT_YUV8_1X24:
> +	case MEDIA_BUS_FMT_YUV10_1X30:
> +	case MEDIA_BUS_FMT_YUV12_1X36:
> +	case MEDIA_BUS_FMT_YUV16_1X48:
> +		return fmt == DRM_COLOR_FORMAT_YCBCR444;
> +	case MEDIA_BUS_FMT_UYVY8_1X16:
> +	case MEDIA_BUS_FMT_VYUY8_1X16:
> +	case MEDIA_BUS_FMT_YUYV8_1X16:
> +	case MEDIA_BUS_FMT_YVYU8_1X16:
> +	case MEDIA_BUS_FMT_UYVY10_1X20:
> +	case MEDIA_BUS_FMT_YUYV10_1X20:
> +	case MEDIA_BUS_FMT_VYUY10_1X20:
> +	case MEDIA_BUS_FMT_YVYU10_1X20:
> +	case MEDIA_BUS_FMT_UYVY12_1X24:
> +	case MEDIA_BUS_FMT_VYUY12_1X24:
> +	case MEDIA_BUS_FMT_YUYV12_1X24:
> +	case MEDIA_BUS_FMT_YVYU12_1X24:
> +		return fmt == DRM_COLOR_FORMAT_YCBCR422;
> +	case MEDIA_BUS_FMT_UYYVYY8_0_5X24:
> +	case MEDIA_BUS_FMT_UYYVYY10_0_5X30:
> +	case MEDIA_BUS_FMT_UYYVYY12_0_5X36:
> +	case MEDIA_BUS_FMT_UYYVYY16_0_5X48:
> +		return fmt == DRM_COLOR_FORMAT_YCBCR420;
> +	default:
> +		return false;
> +	}
> +}
> +
>  /*
>   * This function is called by &drm_atomic_bridge_chain_check() just before
>   * calling &drm_bridge_funcs.atomic_check() on all elements of the chain.
> @@ -1137,6 +1178,10 @@ drm_atomic_bridge_chain_select_bus_fmts(struct drm_bridge *bridge,
>  	}
>  
>  	for (i = 0; i < num_out_bus_fmts; i++) {
> +		if (!bus_format_is_color_fmt(out_bus_fmts[i], conn_state->color_format)) {
> +			ret = -ENOTSUPP;
> +			continue;
> +		}

Sorry, I'm struggling a bit to understand how this would work if a bridge both supports the bus
format selection and HDMI state helpers? Can you expand on it?

Maxime

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