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X-CSE-ConnectionGUID: ytz6kgz7Sq2O2FOAKDAqfA== X-CSE-MsgGUID: yvcApxs8RwCOpgNtGE5huw== X-IronPort-AV: E=McAfee;i="6800,10657,11740"; a="74609589" X-IronPort-AV: E=Sophos;i="6.23,142,1770624000"; d="scan'208";a="74609589" Received: from orviesa008.jf.intel.com ([10.64.159.148]) by fmvoesa113.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Mar 2026 05:13:41 -0700 X-CSE-ConnectionGUID: Hy7QV1bWQjSMDuQal12t3g== X-CSE-MsgGUID: cmBX5ss4QoGdYutSUOzaDg== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,142,1770624000"; d="scan'208";a="225000372" Received: from pgcooper-mobl3.ger.corp.intel.com (HELO localhost) ([10.245.244.14]) by orviesa008-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Mar 2026 05:13:31 -0700 Date: Thu, 26 Mar 2026 14:13:28 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Dave Stevenson Cc: Nicolas Frattaroli , Harry Wentland , Leo Li , Rodrigo Siqueira , Alex Deucher , Christian =?iso-8859-1?Q?K=F6nig?= , David Airlie , Simona Vetter , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , Andrzej Hajda , Neil Armstrong , Robert Foss , Laurent Pinchart , Jonas Karlman , Jernej Skrabec , Sandy Huang , Heiko =?iso-8859-1?Q?St=FCbner?= , Andy Yan , Jani Nikula , Rodrigo Vivi , Joonas Lahtinen , Tvrtko Ursulin , Dmitry Baryshkov , Sascha Hauer , Rob Herring , Jonathan Corbet , Shuah Khan , kernel@collabora.com, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-rockchip@lists.infradead.org, intel-gfx@lists.freedesktop.org, intel-xe@lists.freedesktop.org, linux-doc@vger.kernel.org, Werner Sembach , Andri Yngvason , Marius Vlad Subject: Re: [PATCH v11 03/22] drm: Add new general DRM property "color format" Message-ID: References: <20260324-color-format-v11-0-605559af4fb4@collabora.com> <20260324-color-format-v11-3-605559af4fb4@collabora.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Patchwork-Hint: comment Organization: Intel Finland Oy - BIC 0357606-4 - c/o Alberga Business Park, 6 krs Bertel Jungin Aukio 5, 02600 Espoo, Finland On Thu, Mar 26, 2026 at 11:16:12AM +0000, Dave Stevenson wrote: > On Wed, 25 Mar 2026 at 13:43, Ville Syrjälä > wrote: > > > > On Wed, Mar 25, 2026 at 12:49:19PM +0000, Dave Stevenson wrote: > > > On Tue, 24 Mar 2026 at 16:02, Nicolas Frattaroli > > > wrote: > > > > > > > > Add a new general DRM property named "color format" which can be used by > > > > userspace to request the display driver to output a particular color > > > > format. > > > > > > > > Possible options are: > > > > - auto (setup by default, driver internally picks the color format) > > > > - rgb > > > > - ycbcr444 > > > > - ycbcr422 > > > > - ycbcr420 > > > > > > > > Drivers should advertise from this list which formats they support. > > > > Together with this list and EDID data from the sink we should be able > > > > to relay a list of usable color formats to users to pick from. > > > > > > > > Co-developed-by: Werner Sembach > > > > Signed-off-by: Werner Sembach > > > > Co-developed-by: Andri Yngvason > > > > Signed-off-by: Andri Yngvason > > > > Signed-off-by: Marius Vlad > > > > Reviewed-by: Maxime Ripard > > > > Signed-off-by: Nicolas Frattaroli > > > > --- > > > > drivers/gpu/drm/drm_atomic_helper.c | 5 ++ > > > > drivers/gpu/drm/drm_atomic_uapi.c | 11 ++++ > > > > drivers/gpu/drm/drm_connector.c | 108 ++++++++++++++++++++++++++++++++++++ > > > > include/drm/drm_connector.h | 104 ++++++++++++++++++++++++++++++++++ > > > > 4 files changed, 228 insertions(+) > > > > > > > > diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c > > > > index 26953ed6b53e..b7753454b777 100644 > > > > --- a/drivers/gpu/drm/drm_atomic_helper.c > > > > +++ b/drivers/gpu/drm/drm_atomic_helper.c > > > > @@ -737,6 +737,11 @@ drm_atomic_helper_check_modeset(struct drm_device *dev, > > > > if (old_connector_state->max_requested_bpc != > > > > new_connector_state->max_requested_bpc) > > > > new_crtc_state->connectors_changed = true; > > > > + > > > > + if (old_connector_state->color_format != > > > > + new_connector_state->color_format) > > > > + new_crtc_state->connectors_changed = true; > > > > + > > > > } > > > > > > > > if (funcs->atomic_check) > > > > diff --git a/drivers/gpu/drm/drm_atomic_uapi.c b/drivers/gpu/drm/drm_atomic_uapi.c > > > > index 5bd5bf6661df..dee510c85e59 100644 > > > > --- a/drivers/gpu/drm/drm_atomic_uapi.c > > > > +++ b/drivers/gpu/drm/drm_atomic_uapi.c > > > > @@ -935,6 +935,15 @@ static int drm_atomic_connector_set_property(struct drm_connector *connector, > > > > state->privacy_screen_sw_state = val; > > > > } else if (property == connector->broadcast_rgb_property) { > > > > state->hdmi.broadcast_rgb = val; > > > > + } else if (property == connector->color_format_property) { > > > > + if (val > INT_MAX || !drm_connector_color_format_valid(val)) { > > > > + drm_dbg_atomic(connector->dev, > > > > + "[CONNECTOR:%d:%s] unknown color format %llu\n", > > > > + connector->base.id, connector->name, val); > > > > + return -EINVAL; > > > > + } > > > > + > > > > + state->color_format = val; > > > > } else if (connector->funcs->atomic_set_property) { > > > > return connector->funcs->atomic_set_property(connector, > > > > state, property, val); > > > > @@ -1020,6 +1029,8 @@ drm_atomic_connector_get_property(struct drm_connector *connector, > > > > *val = state->privacy_screen_sw_state; > > > > } else if (property == connector->broadcast_rgb_property) { > > > > *val = state->hdmi.broadcast_rgb; > > > > + } else if (property == connector->color_format_property) { > > > > + *val = state->color_format; > > > > } else if (connector->funcs->atomic_get_property) { > > > > return connector->funcs->atomic_get_property(connector, > > > > state, property, val); > > > > diff --git a/drivers/gpu/drm/drm_connector.c b/drivers/gpu/drm/drm_connector.c > > > > index 47dc53c4a738..e848374dee0b 100644 > > > > --- a/drivers/gpu/drm/drm_connector.c > > > > +++ b/drivers/gpu/drm/drm_connector.c > > > > @@ -1388,6 +1388,18 @@ static const u32 hdmi_colorspaces = > > > > BIT(DRM_MODE_COLORIMETRY_DCI_P3_RGB_D65) | > > > > BIT(DRM_MODE_COLORIMETRY_DCI_P3_RGB_THEATER); > > > > > > > > +static const u32 hdmi_colorformats = > > > > + BIT(DRM_OUTPUT_COLOR_FORMAT_RGB444) | > > > > + BIT(DRM_OUTPUT_COLOR_FORMAT_YCBCR444) | > > > > + BIT(DRM_OUTPUT_COLOR_FORMAT_YCBCR422) | > > > > + BIT(DRM_OUTPUT_COLOR_FORMAT_YCBCR420); > > > > + > > > > +static const u32 dp_colorformats = > > > > + BIT(DRM_OUTPUT_COLOR_FORMAT_RGB444) | > > > > + BIT(DRM_OUTPUT_COLOR_FORMAT_YCBCR444) | > > > > + BIT(DRM_OUTPUT_COLOR_FORMAT_YCBCR422) | > > > > + BIT(DRM_OUTPUT_COLOR_FORMAT_YCBCR420); > > > > + > > > > /* > > > > * As per DP 1.4a spec, 2.2.5.7.5 VSC SDP Payload for Pixel Encoding/Colorimetry > > > > * Format Table 2-120 > > > > @@ -2940,6 +2952,102 @@ int drm_connector_attach_colorspace_property(struct drm_connector *connector) > > > > } > > > > EXPORT_SYMBOL(drm_connector_attach_colorspace_property); > > > > > > > > +/** > > > > + * drm_connector_attach_color_format_property - create and attach color format property > > > > + * @connector: connector to create the color format property on > > > > + * @supported_color_formats: bitmask of bit-shifted &enum drm_output_color_format > > > > + * values the connector supports > > > > + * > > > > + * Called by a driver to create a color format property. The property is > > > > + * attached to the connector automatically on success. > > > > + * > > > > + * @supported_color_formats should only include color formats the connector > > > > + * type can actually support. > > > > + * > > > > + * Returns: > > > > + * 0 on success, negative errno on error > > > > + */ > > > > +int drm_connector_attach_color_format_property(struct drm_connector *connector, > > > > + unsigned long supported_color_formats) > > > > +{ > > > > + struct drm_device *dev = connector->dev; > > > > + struct drm_prop_enum_list enum_list[DRM_CONNECTOR_COLOR_FORMAT_COUNT]; > > > > + unsigned int i = 0; > > > > + unsigned long fmt; > > > > + > > > > + if (connector->color_format_property) > > > > + return 0; > > > > + > > > > + if (!supported_color_formats) { > > > > + drm_err(dev, "No supported color formats provided on [CONNECTOR:%d:%s]\n", > > > > + connector->base.id, connector->name); > > > > + return -EINVAL; > > > > + } > > > > + > > > > + if (supported_color_formats & ~GENMASK(DRM_OUTPUT_COLOR_FORMAT_COUNT - 1, 0)) { > > > > + drm_err(dev, "Unknown color formats provided on [CONNECTOR:%d:%s]\n", > > > > + connector->base.id, connector->name); > > > > + return -EINVAL; > > > > + } > > > > + > > > > + switch (connector->connector_type) { > > > > + case DRM_MODE_CONNECTOR_HDMIA: > > > > + case DRM_MODE_CONNECTOR_HDMIB: > > > > + if (supported_color_formats & ~hdmi_colorformats) { > > > > + drm_err(dev, "Color formats not allowed for HDMI on [CONNECTOR:%d:%s]\n", > > > > + connector->base.id, connector->name); > > > > + return -EINVAL; > > > > + } > > > > + break; > > > > + case DRM_MODE_CONNECTOR_DisplayPort: > > > > + case DRM_MODE_CONNECTOR_eDP: > > > > + if (supported_color_formats & ~dp_colorformats) { > > > > + drm_err(dev, "Color formats not allowed for DP on [CONNECTOR:%d:%s]\n", > > > > + connector->base.id, connector->name); > > > > + return -EINVAL; > > > > + } > > > > + break; > > > > + } > > > > + > > > > + enum_list[0].name = "AUTO"; > > > > + enum_list[0].type = DRM_CONNECTOR_COLOR_FORMAT_AUTO; > > > > + > > > > + for_each_set_bit(fmt, &supported_color_formats, DRM_OUTPUT_COLOR_FORMAT_COUNT) { > > > > + switch (fmt) { > > > > + case DRM_OUTPUT_COLOR_FORMAT_RGB444: > > > > + enum_list[++i].type = DRM_CONNECTOR_COLOR_FORMAT_RGB444; > > > > + break; > > > > + case DRM_OUTPUT_COLOR_FORMAT_YCBCR444: > > > > + enum_list[++i].type = DRM_CONNECTOR_COLOR_FORMAT_YCBCR444; > > > > + break; > > > > + case DRM_OUTPUT_COLOR_FORMAT_YCBCR422: > > > > + enum_list[++i].type = DRM_CONNECTOR_COLOR_FORMAT_YCBCR422; > > > > + break; > > > > + case DRM_OUTPUT_COLOR_FORMAT_YCBCR420: > > > > + enum_list[++i].type = DRM_CONNECTOR_COLOR_FORMAT_YCBCR420; > > > > + break; > > > > + default: > > > > + drm_warn(dev, "Unknown supported format %ld on [CONNECTOR:%d:%s]\n", > > > > + fmt, connector->base.id, connector->name); > > > > + continue; > > > > + } > > > > + enum_list[i].name = drm_hdmi_connector_get_output_format_name(fmt); > > > > + } > > > > + > > > > + connector->color_format_property = > > > > + drm_property_create_enum(dev, DRM_MODE_PROP_ENUM, "color format", > > > > + enum_list, i + 1); > > > > + > > > > + if (!connector->color_format_property) > > > > + return -ENOMEM; > > > > + > > > > + drm_object_attach_property(&connector->base, connector->color_format_property, > > > > + DRM_CONNECTOR_COLOR_FORMAT_AUTO); > > > > + > > > > + return 0; > > > > +} > > > > +EXPORT_SYMBOL(drm_connector_attach_color_format_property); > > > > + > > > > /** > > > > * drm_connector_atomic_hdr_metadata_equal - checks if the hdr metadata changed > > > > * @old_state: old connector state to compare > > > > diff --git a/include/drm/drm_connector.h b/include/drm/drm_connector.h > > > > index af8b92d2d5b7..bd549f912b76 100644 > > > > --- a/include/drm/drm_connector.h > > > > +++ b/include/drm/drm_connector.h > > > > @@ -571,14 +571,102 @@ enum drm_colorspace { > > > > * YCbCr 4:2:2 output format (ie. with horizontal subsampling) > > > > * @DRM_OUTPUT_COLOR_FORMAT_YCBCR420: > > > > * YCbCr 4:2:0 output format (ie. with horizontal and vertical subsampling) > > > > + * @DRM_OUTPUT_COLOR_FORMAT_COUNT: > > > > + * Number of valid output color format values in this enum > > > > */ > > > > enum drm_output_color_format { > > > > DRM_OUTPUT_COLOR_FORMAT_RGB444 = 0, > > > > DRM_OUTPUT_COLOR_FORMAT_YCBCR444, > > > > DRM_OUTPUT_COLOR_FORMAT_YCBCR422, > > > > DRM_OUTPUT_COLOR_FORMAT_YCBCR420, > > > > + DRM_OUTPUT_COLOR_FORMAT_COUNT, > > > > }; > > > > > > > > +/** > > > > + * enum drm_connector_color_format - Connector Color Format Request > > > > + * > > > > + * This enum, unlike &enum drm_output_color_format, is used to specify requests > > > > + * for a specific color format on a connector through the DRM "color format" > > > > + * property. The difference is that it has an "AUTO" value to specify that > > > > + * no specific choice has been made. > > > > + */ > > > > +enum drm_connector_color_format { > > > > + /** > > > > + * @DRM_CONNECTOR_COLOR_FORMAT_AUTO: The driver or display protocol > > > > + * helpers should pick a suitable color format. All implementations of a > > > > + * specific display protocol must behave the same way with "AUTO", but > > > > + * different display protocols do not necessarily have the same "AUTO" > > > > + * semantics. > > > > + * > > > > + * For HDMI, "AUTO" picks RGB, but falls back to YCbCr 4:2:0 if the > > > > + * bandwidth required for full-scale RGB is not available, or the mode > > > > + * is YCbCr 4:2:0-only, as long as the mode and output both support > > > > + * YCbCr 4:2:0. > > > > > > Is there a reason you propose dropping back to YCbCr 4:2:0 without > > > trying YCbCr 4:2:2 first? Minimising the subsampling is surely > > > beneficial, and vc4 for one can do 4:2:2 but not 4:2:0. > > > > On HDMI 4:2:2 is always 12bpc, so it doesn't save any bandwidth > > compared to 8bpc 4:4:4. > > It does save bandwidth against 10 or 12bpc RGB 4:4:4. > > Or is the implication that max_bpc = 12 and > DRM_CONNECTOR_COLOR_FORMAT_AUTO should drop bpc down to 8 and select > RGB in preference to selecting 4:2:2? Yeah, YCbCr has all kinds of extra complications compared to RGB, so the policy is to use RGB if possible, and only fall back to YCbCr as a last resort. And in that case 4:2:0 is the only thing that can help. -- Ville Syrjälä Intel