From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.16]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 074F03914EE for ; Wed, 1 Apr 2026 12:11:23 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=198.175.65.16 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775045487; cv=none; b=XeYtFMBaUhhPMsJIWj9uVcWFNamSXsF5o0ySjKH0tWy3QYs6up2+bqdE9M3iFNi0GTGRfeLt9gmJspWhGyjTDesM0ezy9hISqA+C+Hb3EmLxQFlT5QYlj8v5T2y+1FJg9u3AwoDROvb+mP4thbh2zwJ54tVbWu4n1JLVLlls4xE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775045487; c=relaxed/simple; bh=LtRf7ZPQ2KP/yLd6h4tuXhNMx+utLON+zyadehE9NWs=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Rh7CsQ8z7n1lFe7Numn4vgtw8kc/tQMHIL5K35+jScafHoZDbILL42P14qdI44HykE9i6r4YjLcZ+ZLW+RV1imo2vDcePE9InvUQaCNm2rkxlQtco6CdU1dT3x0RE7/GsLoDwtpmKH/nZmKX6oXX48yRkZXjWikmxltJqd5eaKo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com; spf=pass smtp.mailfrom=intel.com; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b=X6rJpvZI; arc=none smtp.client-ip=198.175.65.16 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.intel.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=intel.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=intel.com header.i=@intel.com header.b="X6rJpvZI" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1775045484; x=1806581484; h=date:from:to:cc:subject:message-id:references: mime-version:content-transfer-encoding:in-reply-to; bh=LtRf7ZPQ2KP/yLd6h4tuXhNMx+utLON+zyadehE9NWs=; b=X6rJpvZIN6WeVE5Iucn4B1k5HInlWx6dm7BDPK/rKdunPke8K+/+x/Zr MBC54p+dqmrwNqYPW5x5vxHgQmszWiYHkLmJyKnu+KtWgOtuak4P6f5V+ 4Hn/X4AFzPzi51k4V8oH9FthloINnxh6HUCsNM5StYRbjOWbvowY4BqRV N+5vBiEJEoOL6z/1hjAfqYecxrSMNauvXJCnQI6XVi/PnsktA3Pz5Edyf 1s1YrnZu59/n6fYNtgYDk1P2TyrFFxRoDg86EeLv/LK+J5aBdLa8ToQnO za2Y0Q9fuKRt5442acwE3NUCbJkwZg9JhamYm2/DufdrLTLRvm+xJuh5l A==; X-CSE-ConnectionGUID: uOfFKG3XSI+gjDcHQ3T90A== X-CSE-MsgGUID: SE/O9IvHST2xGKqqvVduvg== X-IronPort-AV: E=McAfee;i="6800,10657,11745"; a="76268724" X-IronPort-AV: E=Sophos;i="6.23,153,1770624000"; d="scan'208";a="76268724" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa108.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2026 05:11:23 -0700 X-CSE-ConnectionGUID: EnIUM/blQZOH4k+QMBCR9Q== X-CSE-MsgGUID: LVUKNrBhS52fHw78/muo5Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.23,153,1770624000"; d="scan'208";a="231071665" Received: from pgcooper-mobl3.ger.corp.intel.com (HELO localhost) ([10.245.244.199]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Apr 2026 05:11:17 -0700 Date: Wed, 1 Apr 2026 15:11:14 +0300 From: Ville =?iso-8859-1?Q?Syrj=E4l=E4?= To: Xaver Hugl Cc: Nicolas Frattaroli , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Harry Wentland , Leo Li , Rodrigo Siqueira , Alex Deucher , Christian =?iso-8859-1?Q?K=F6nig?= , Daniel Stone , Dmitry Baryshkov , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, amd-gfx@lists.freedesktop.org, kernel@collabora.com, Derek Foreman , Marius Vlad , wayland-devel@lists.freedesktop.org Subject: Re: [PATCH v5 0/3] Add "link bpc" DRM property Message-ID: References: <20260319-link-bpc-v5-0-5306cd04a708@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 Wed, Apr 01, 2026 at 01:57:08PM +0200, Xaver Hugl wrote: > Am Do., 19. März 2026 um 13:28 Uhr schrieb Nicolas Frattaroli > : > > > > This series adds a new "link bpc" DRM property. It reflects the display > > link's actual achieved output bits per component, considering any > > degradation of the bit depth done by drivers for bandwidth or other > > reasons. The property's value is updated during an atomic commit, which > > is also when it fires an uevent if it changed to let userspace know. > > Hi, > I think it's a really good idea to have a property for knowing the > actual bpc of the link... however, I do have one big concern with this > API specifically: It only gives me this information after a modeset. > > With this limitation, I can at most show the user which bpc was chosen > after the apply display settings and have the end user manually test > and figure things out, but I cannot show in the UI which bpc will be > chosen with some configuration before they apply it, and I cannot do > atomic tests to find a desired tradeoff automatically on the > compositor side. I think the idea of some kind of feedback properties in the atomic commit has come up before, but no one has ever tried to implement them. > > As a side note, for future patches relevant for compositors, please cc > wayland-devel. It really shouldn't be up to chance whether or not > compositor developers that would later use the API find out about it > before it's merged, and keeping track of all of dri-devel is way too > much to ask from userspace developers. > > - Xaver -- Ville Syrjälä Intel