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X-CSE-ConnectionGUID: JCyG2RB5QSC6boaAmu66KA== X-CSE-MsgGUID: zFxDfkndQfiAxpYjY3M8tQ== X-IronPort-AV: E=McAfee;i="6800,10657,11740"; a="75228914" X-IronPort-AV: E=Sophos;i="6.23,140,1770624000"; d="scan'208";a="75228914" Received: from fmviesa005.fm.intel.com ([10.60.135.145]) by orvoesa112.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2026 11:43:28 -0700 X-CSE-ConnectionGUID: PIgWhb1sReuCAFXJCMmd4Q== X-CSE-MsgGUID: SQkIRvm5QpyELM31Jk3yCw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,140,1770624000"; d="scan'208";a="229541235" Received: from smoticic-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.245.117]) by fmviesa005-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 25 Mar 2026 11:43:17 -0700 Date: Wed, 25 Mar 2026 20:43:15 +0200 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Maxime Ripard Cc: Nicolas Frattaroli , Harry Wentland , Leo Li , Rodrigo Siqueira , Alex Deucher , Christian =?iso-8859-1?Q?K=F6nig?= , David Airlie , Simona Vetter , Maarten Lankhorst , 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> <23910073.EfDdHjke4D@workhorse> <20260325-neat-elegant-raven-ebc9ab@houat> <20260325-magnificent-ultraviolet-oarfish-baefbc@houat> 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: <20260325-magnificent-ultraviolet-oarfish-baefbc@houat> 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 Wed, Mar 25, 2026 at 03:56:58PM +0100, Maxime Ripard wrote: > On Wed, Mar 25, 2026 at 01:03:07PM +0200, Ville Syrjälä wrote: > > On Wed, Mar 25, 2026 at 09:24:27AM +0100, Maxime Ripard wrote: > > > On Tue, Mar 24, 2026 at 09:53:35PM +0200, Ville Syrjälä wrote: > > > > On Tue, Mar 24, 2026 at 08:10:11PM +0100, Nicolas Frattaroli wrote: > > > > > On Tuesday, 24 March 2026 18:00:45 Central European Standard Time Ville Syrjälä wrote: > > > > > > On Tue, Mar 24, 2026 at 05:01:07PM +0100, Nicolas Frattaroli wrote: > > > > > > > +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. > > > > > > > + * > > > > > > > + * For display protocols other than HDMI, the recursive bridge chain > > > > > > > + * format selection picks the first chain of bridge formats that works, > > > > > > > + * as has already been the case before the introduction of the "color > > > > > > > + * format" property. Non-HDMI bridges should therefore either sort their > > > > > > > + * bus output formats by preference, or agree on a unified auto format > > > > > > > + * selection logic that's implemented in a common state helper (like > > > > > > > + * how HDMI does it). > > > > > > > + */ > > > > > > > + DRM_CONNECTOR_COLOR_FORMAT_AUTO = 0, > > > > > > > + > > > > > > > + /** > > > > > > > + * @DRM_CONNECTOR_COLOR_FORMAT_RGB444: RGB output format > > > > > > > + */ > > > > > > > + DRM_CONNECTOR_COLOR_FORMAT_RGB444, > > > > > > > + > > > > > > > + /** > > > > > > > + * @DRM_CONNECTOR_COLOR_FORMAT_YCBCR444: YCbCr 4:4:4 output format (ie. > > > > > > > + * not subsampled) > > > > > > > + */ > > > > > > > + DRM_CONNECTOR_COLOR_FORMAT_YCBCR444, > > > > > > > + > > > > > > > + /** > > > > > > > + * @DRM_CONNECTOR_COLOR_FORMAT_YCBCR422: YCbCr 4:2:2 output format (ie. > > > > > > > + * with horizontal subsampling) > > > > > > > + */ > > > > > > > + DRM_CONNECTOR_COLOR_FORMAT_YCBCR422, > > > > > > > + > > > > > > > + /** > > > > > > > + * @DRM_CONNECTOR_COLOR_FORMAT_YCBCR420: YCbCr 4:2:0 output format (ie. > > > > > > > + * with horizontal and vertical subsampling) > > > > > > > + */ > > > > > > > + DRM_CONNECTOR_COLOR_FORMAT_YCBCR420, > > > > > > > > > > > > Seems like this should document what the quantization range > > > > > > should be for each format. > > > > > > > > > > > > > > > > I don't think so? If you want per-component bit depth values, > > > > > DRM_FORMAT_* defines would be the appropriate values to use. This > > > > > enum is more abstract than that, and is there to communicate > > > > > YUV vs. RGB and chroma subsampling, with bit depth being handled > > > > > by other properties. > > > > > > > > > > If you mean the factor used for subsampling, then that'd only be > > > > > relevant if YCBCR410 was supported where one chroma plane isn't > > > > > halved but quartered in resolution. I suspect 4:1:0 will never > > > > > be added; no digital display protocol standard supports it to my > > > > > knowledge, and hopefully none ever will. > > > > > > > > No, I mean the quantization range (16-235 vs. 0-255 etc). > > > > > > > > The i915 behaviour is that YCbCr is always limited range, > > > > RGB can either be full or limited range depending on the > > > > "Broadcast RGB" property and other related factors. > > > > > > So far the HDMI state has both the format and quantization range as > > > different fields. I'm not sure we need to document the range in the > > > format field, maybe only mention it's not part of the format but has a > > > field of its own? > > > > I think we only have it for RGB (on some drivers only?). For YCbCr > > I think the assumption is limited range everywhere. > > > > But I'm not really concerned about documenting struct members. > > What I'm talking about is the *uapi* docs. Surely userspace > > will want to know what the new property actually does so the > > uapi needs to be documented properly. And down the line some > > new driver might also implement the wrong behaviour if there > > is no clear specification. > > Ack > > > So I'm thinking (or perhaps hoping) the rule might be something like: > > - YCbCr limited range > > - RGB full range if "Broadcast RGB" property is not present > > Isn't it much more complicated than that for HDMI though? My > recollection was that any VIC but VIC1 would be limited range, and > anything else full range? Do we have some driver that implements the CTA-861 CE vs. IT mode logic but doesn't expose the "Broadcast RGB" property? I was hoping those would always go hand in hand now. > > > - RGB full or limited range based on the "Broadcast RGB" property > > if it's present > > > > I think the "Broadcast RGB" property itself might also be lacking > > proper uapi docs, so that may need to be remedied as well. > > I took care of documenting it when merging the HDMI helpers: > https://docs.kernel.org/gpu/drm-kms.html#hdmi-specific-connector-properties > > Maxime -- Ville Syrjälä Intel