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X-CSE-ConnectionGUID: pOI6ITWjSzeXROErzOOInA== X-CSE-MsgGUID: 9gDCUZ26TjqQem/JIn45/w== X-IronPort-AV: E=McAfee;i="6800,10657,11742"; a="74768565" X-IronPort-AV: E=Sophos;i="6.23,145,1770624000"; d="scan'208";a="74768565" Received: from orviesa006.jf.intel.com ([10.64.159.146]) by fmvoesa113.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Mar 2026 17:22:13 -0700 X-CSE-ConnectionGUID: mSyIvSuCRBKSEXuAKNOjtQ== X-CSE-MsgGUID: SWzO0wyVQ2SyujTRwk21xw== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,145,1770624000"; d="scan'208";a="224498686" Received: from ijarvine-mobl1.ger.corp.intel.com (HELO localhost) ([10.245.244.188]) by orviesa006-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Mar 2026 17:22:04 -0700 Date: Sat, 28 Mar 2026 02:22:01 +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-v11-3-605559af4fb4@collabora.com> <23910073.EfDdHjke4D@workhorse> <20260325-neat-elegant-raven-ebc9ab@houat> <20260325-magnificent-ultraviolet-oarfish-baefbc@houat> <20260326-pumpkin-goshawk-of-stamina-0ccb84@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: 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 07:58:25PM +0200, Ville Syrjälä wrote: > On Thu, Mar 26, 2026 at 06:02:47PM +0100, Maxime Ripard wrote: > > On Wed, Mar 25, 2026 at 08:43:15PM +0200, Ville Syrjälä wrote: > > > 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. > > > > I'm not sure. i915 and the HDMI state helpers handle it properly (I > > think?) but it looks like only vc4 registers the Broadcast RGB property > > and uses the HDMI state helpers. > > > > And it looks like amdgpu registers Broadcast RGB but doesn't use > > drm_default_rgb_quant_range() which seems suspicious? > > If they want just manual full vs. limited then they should > limit the property to not expose the "auto" option at all. > > amdgpu also ties this in with the "colorspace" property, which > originally in i915 only controlled the infoframes/etc. But on > amdgpu it now controls various aspects of output color > transformation. The end result is that the property is a complete > mess with most of the values making no sense. And for whatever > reason everyone involved refused to remove/deprecate the > nonsensical values :/ > > Looks like this series should make sure the documentation for > the "colorspace" property is in sync with the new property > as well. Currently now it's giving conflicting information. After pondering about this a bit more I guess we could actually use this to make all the values of the colorspace property make some sense. Since we won't have to worry about that RGB->YCbCr 4:2:0 fallback when using and explicit color format, all we'd have to do is explicitly reject the nonsensical combinations: color_format_and_colorspace_ok() { switch (color_format) { case DRM_CONNECTOR_COLOR_FORMAT_YCBCR444: case DRM_CONNECTOR_COLOR_FORMAT_YCBCR422: case DRM_CONNECTOR_COLOR_FORMAT_YCBCR420: switch (colorspace) { case DRM_MODE_COLORIMETRY_NO_DATA: case DRM_MODE_COLORIMETRY_SMPTE_170M_YCC: case DRM_MODE_COLORIMETRY_BT601_YCC: case DRM_MODE_COLORIMETRY_BT709_YCC: case DRM_MODE_COLORIMETRY_XVYCC_601: case DRM_MODE_COLORIMETRY_XVYCC_709: case DRM_MODE_COLORIMETRY_SYCC_601: case DRM_MODE_COLORIMETRY_OPYCC_601: case DRM_MODE_COLORIMETRY_BT2020_CYCC: case DRM_MODE_COLORIMETRY_BT2020_YCC: case DRM_MODE_COLORIMETRY_BT709_YCC: return true; default: return false; } break; case DRM_CONNECTOR_COLOR_FORMAT_RGB444: switch (colorspace) { case DRM_MODE_COLORIMETRY_NO_DATA: case DRM_MODE_COLORIMETRY_OPRGB: case DRM_MODE_COLORIMETRY_BT2020_RGB: case DRM_MODE_COLORIMETRY_DCI_P3_RGB_D65: case DRM_MODE_COLORIMETRY_DCI_P3_RGB_THEATER: case DRM_MODE_COLORIMETRY_RGB_WIDE_FIXED: case DRM_MODE_COLORIMETRY_RGB_WIDE_FLOAT: case DRM_MODE_COLORIMETRY_OPRGB: case DRM_MODE_COLORIMETRY_DCI_P3_RGB_D65: case DRM_MODE_COLORIMETRY_BT2020_RGB: return true; default return false; } break; case DRM_CONNECTOR_COLOR_FORMAT_AUTO: switch (colorspace) { case DRM_MODE_COLORIMETRY_NO_DATA: case DRM_MODE_COLORIMETRY_BT2020_RGB: case DRM_MODE_COLORIMETRY_BT2020_YCC: return true; default: return false; } default: bad; } } And then presumably the colorspace property is the thing that should dictate which conversion matrix to use. So something like this: csc_matrix() { switch (colorspace) { case DRM_MODE_COLORIMETRY_SMPTE_170M_YCC: case DRM_MODE_COLORIMETRY_BT601_YCC: case DRM_MODE_COLORIMETRY_XVYCC_601: case DRM_MODE_COLORIMETRY_SYCC_601: case DRM_MODE_COLORIMETRY_OPYCC_601: return 601; case DRM_MODE_COLORIMETRY_BT709_YCC: case DRM_MODE_COLORIMETRY_XVYCC_709: return 709; case DRM_MODE_COLORIMETRY_BT2020_YCC: case DRM_MODE_COLORIMETRY_BT2020_RGB: return 2020; case DRM_MODE_COLORIMETRY_BT2020_CYCC: return 2020_const; case DRM_MODE_COLORIMETRY_NO_DATA: return vdisplay >= 720 ? 709 : 601; default: bad; } } -- Ville Syrjälä Intel