linux-kernel - Re: [PATCH v4 03/10] drm: Add enum conversion from/to HDMI_COLORSPACE to DRM_COLOR

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Message-ID: <20251119041648.GD10711@pendragon.ideasonboard.com>
Date: Wed, 19 Nov 2025 13:16:48 +0900
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
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>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	Andrzej Hajda <andrzej.hajda@...el.com>,
	Neil Armstrong <neil.armstrong@...aro.org>,
	Robert Foss <rfoss@...nel.org>, 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,
	Marius Vlad <marius.vlad@...labora.com>
Subject: Re: [PATCH v4 03/10] drm: Add enum conversion from/to
 HDMI_COLORSPACE to DRM_COLOR_FORMAT

On Mon, Nov 17, 2025 at 08:11:47PM +0100, Nicolas Frattaroli wrote:
> From: Marius Vlad <marius.vlad@...labora.com>
> 
> This would please the compiler to have a enum transformation from one to
> another even though the values are the same. It should also make things

The hdmi_colorspace enumerators are defined as (with comments added to
make the values explicit)

enum hdmi_colorspace {
	HDMI_COLORSPACE_RGB,			/* 0 */
	HDMI_COLORSPACE_YUV422,			/* 1 */
	HDMI_COLORSPACE_YUV444,			/* 2 */
	HDMI_COLORSPACE_YUV420,			/* 3 */
	HDMI_COLORSPACE_RESERVED4,		/* 4 */
	HDMI_COLORSPACE_RESERVED5,		/* 5 */
	HDMI_COLORSPACE_RESERVED6,		/* 6 */
	HDMI_COLORSPACE_IDO_DEFINED,		/* 7 */
};

and the DRM color formats as (after patch 02/10)

enum drm_color_format {
	DRM_COLOR_FORMAT_NONE			= 0,		/* 0 */
	DRM_COLOR_FORMAT_RGB444			= (1 << 0),	/* 1 */
	DRM_COLOR_FORMAT_YCBCR422		= (1 << 1),	/* 2 */
	DRM_COLOR_FORMAT_YCBCR444		= (1 << 2),	/* 4 */
	DRM_COLOR_FORMAT_YCBCR420		= (1 << 3),	/* 8 */
	/* auto case, driver will set the color_format */
	DRM_COLOR_FORMAT_AUTO			= (1 << 4),	/* 16 */
};

Contrary to what is stated in the commit message, the values are not the
same. Maybe you confused DRM_COLOR_FORMAT_* with DRM_MODE_COLOR_FORMAT_*
?

> obvious that we use different enums.
> 
> Signed-off-by: Marius Vlad <marius.vlad@...labora.com>
> ---
>  drivers/gpu/drm/drm_connector.c | 18 ++++++++++++++++++
>  include/drm/drm_connector.h     |  3 +++
>  2 files changed, 21 insertions(+)
> 
> diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c
> index 0ad7be0a2d09..61c077b67ac3 100644
> --- a/drivers/gpu/drm/drm_connector.c
> +++ b/drivers/gpu/drm/drm_connector.c
> @@ -1384,6 +1384,24 @@ drm_color_format_enum_to_color_format(enum drm_color_format_enum fmt_enum)
>  	}
>  }
>  
> +enum hdmi_colorspace
> +color_format_to_hdmi_colorspace(enum drm_color_format fmt)
> +{
> +	switch (fmt) {
> +	default:
> +	case DRM_COLOR_FORMAT_AUTO:
> +	case DRM_COLOR_FORMAT_RGB444:
> +		return HDMI_COLORSPACE_RGB;
> +	case DRM_COLOR_FORMAT_YCBCR444:
> +		return HDMI_COLORSPACE_YUV444;
> +	case DRM_COLOR_FORMAT_YCBCR422:
> +		return HDMI_COLORSPACE_YUV422;
> +	case DRM_COLOR_FORMAT_YCBCR420:
> +		return HDMI_COLORSPACE_YUV420;
> +	}
> +}
> +EXPORT_SYMBOL(color_format_to_hdmi_colorspace);
> +
>  /**
>   * drm_get_color_format_name - return a string for color format
>   * @colorspace: color format to compute name of
> diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h
> index a071079fd3ad..e044976c8d76 100644
> --- a/include/drm/drm_connector.h
> +++ b/include/drm/drm_connector.h
> @@ -2586,6 +2586,9 @@ drm_color_format_to_color_format_enum(enum drm_color_format fmt);
>  u32
>  drm_color_format_enum_to_color_format(enum drm_color_format_enum fmt_enum);
>  
> +enum hdmi_colorspace
> +color_format_to_hdmi_colorspace(enum drm_color_format fmt);
> +
>  /**
>   * drm_for_each_connector_iter - connector_list iterator macro
>   * @connector: &struct drm_connector pointer used as cursor

-- 
Regards,

Laurent Pinchart