Re: [PATCH v5 05/17] drm/display: hdmi-state-helper: Act on color format DRM property

[Maxime Ripard <mripard@kernel.org>]

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On Fri, Nov 28, 2025 at 10:05:41PM +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 | 12 +++++++++++-
>  1 file changed, 11 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..5da956bdd68c 100644
> --- a/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> +++ b/drivers/gpu/drm/display/drm_hdmi_state_helper.c
> @@ -649,11 +649,21 @@ hdmi_compute_config(const struct drm_connector *connector,
>  	unsigned int max_bpc = clamp_t(unsigned int,
>  				       conn_state->max_bpc,
>  				       8, connector->max_bpc);
> +	enum hdmi_colorspace hdmi_colorspace =
> +		drm_color_format_to_hdmi_colorspace(conn_state->color_format);
>  	int ret;
>  
>  	ret = hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc,
> -				      HDMI_COLORSPACE_RGB);
> +				      hdmi_colorspace);
>  	if (ret) {
> +		/* If a color format was explicitly requested, don't fall back */
> +		if (conn_state->color_format) {
> +			drm_dbg_kms(connector->dev,
> +				    "Explicitly set color format '%s' doesn't work.\n",
> +				    drm_get_color_format_name(conn_state->color_format));
> +			return ret;
> +		}
> +

I think the following would be more readable:


if (conn_state->color_format && conn_state->color_format != DRM_COLOR_FORMAT_AUTO) {
    enum hdmi_colorspace hdmi_colorspace =
        drm_color_format_to_hdmi_colorspace(conn_state->color_format);

    return hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc, hdmi_colorspace)
}

ret = ret = hdmi_compute_format_bpc(connector, conn_state, mode, max_bpc,
                                    HDMI_COLORSPACE_RGB);

...

Maxime

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