From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from gabe.freedesktop.org (gabe.freedesktop.org [131.252.210.177]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 20540D3517A for ; Wed, 1 Apr 2026 12:11:27 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 307E810ED61; Wed, 1 Apr 2026 12:11:25 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=intel.com header.i=@intel.com header.b="X6rJpvZI"; dkim-atps=neutral Received: from mgamail.intel.com (mgamail.intel.com [198.175.65.16]) by gabe.freedesktop.org (Postfix) with ESMTPS id 8449310ECB9; Wed, 1 Apr 2026 12:11:23 +0000 (UTC) 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: QkfwQgSuRbOKpfVwNr/Vhw== X-CSE-MsgGUID: QMj7VqjGSdi1IfUj608Fhw== X-IronPort-AV: E=McAfee;i="6800,10657,11745"; a="76268725" X-IronPort-AV: E=Sophos;i="6.23,153,1770624000"; d="scan'208";a="76268725" 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> 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 X-BeenThere: amd-gfx@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Discussion list for AMD gfx List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: amd-gfx-bounces@lists.freedesktop.org Sender: "amd-gfx" 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