From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mout-p-103.mailbox.org (mout-p-103.mailbox.org [80.241.56.161]) (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 204B139DBEF for ; Tue, 31 Mar 2026 12:56:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=80.241.56.161 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774961797; cv=none; b=Vu0nFmS20FUIyObaDOuMGXf+1H9U77gBaoV9obcnbQdUxokwrYrKAjVPiZAkp/SoidK2pgMpxWxuZyYQqeMAs5NEZPheYYKeKQiH7WCWcg5ddF7A82nLhiha9Kb+0B9wB9u6fEKmgBuTaOaaJgvJm9GWPeeZzrF7nYzoWISW7qU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1774961797; c=relaxed/simple; bh=O/dR89Mk95cLu4GDFq0S/3rqV0ztPCd7/28YoveqquY=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=d+f0A8g0LL3hPJ+l+MTlehQJKbgPYIZk/hlNd8KEbWMcZnANZH5t1aqkJV3nF0rcHzM90EAFqVtV4sExG3F3h1g0nwy/fhejZRT/1XAbZgVV10Y3AAYnQBWActHzMDf2pH8xO2cRSEZFGAB6iQGFNndTX5L8f4cBN1o0pf5TYHo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mailbox.org; spf=pass smtp.mailfrom=mailbox.org; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b=gg70urw6; arc=none smtp.client-ip=80.241.56.161 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=mailbox.org Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=mailbox.org Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=mailbox.org header.i=@mailbox.org header.b="gg70urw6" Received: from smtp2.mailbox.org (smtp2.mailbox.org [10.196.197.2]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by mout-p-103.mailbox.org (Postfix) with ESMTPS id 4flSmY5yvWz9txF; Tue, 31 Mar 2026 14:56:29 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mailbox.org; s=mail20150812; t=1774961789; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=fR4tNqzFAaNjfM1ALkgthuV0izYT7IoG9clnVyc5I2Y=; b=gg70urw6KJnGO60ZcSCVK5vpTyL8rdBLOZc/+S7EZ2NQ83hfI5P4Zo6kfr7gUgQu5X/0/7 5eGZIQKSzvEKUIuCtG8AsDN2t5ktDffSmyGeBQ1ZsbU48iS7Lz53bgBCbm2CmuE+4+qZDt 4kazYhJxV+Ryl60Dcxelngt6izjc5bTbN3NtgjfAAsg0JUsaxD0TMsSnNgVk8tQxg++j1R 2PgT1hF0DcPrbg9dTIfte2wWzde53GyqpmskFWpD+CXu7h4zWNFpIhEd6oJIfVJSFGeI2n tG8zPxG/IvHOUUgVIAFHPQUTwZYvudawTaIiNzlhR7CImGycEecNJCgono8Law== Message-ID: Date: Tue, 31 Mar 2026 14:56:22 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v5 0/3] Add "link bpc" DRM property To: Pekka Paalanen Cc: Nicolas Frattaroli , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Harry Wentland , Leo Li , Rodrigo Siqueira , Alex Deucher , =?UTF-8?Q?Christian_K=C3=B6nig?= , =?UTF-8?B?VmlsbGUgU3lyasOkbMOk?= , 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 References: <20260319-link-bpc-v5-0-5306cd04a708@collabora.com> <8676926.T7Z3S40VBb@workhorse> <4265353.aeNJFYEL58@workhorse> <254c20a4-cce3-4c8e-9902-514586f3e694@mailbox.org> <20260326155305.736b4e64@fluorite> <47325395-3790-4cb4-8efd-84a3d8ddb80c@mailbox.org> <20260331153805.376486e2@fluorite> From: =?UTF-8?Q?Michel_D=C3=A4nzer?= Content-Language: en-CA In-Reply-To: <20260331153805.376486e2@fluorite> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-MBO-RS-ID: 3ea22b55c6cef5a3c0b X-MBO-RS-META: ru88ojqwgmnp6kdirxom5z1d59n5o6gg On 3/31/26 14:38, Pekka Paalanen wrote: > On Tue, 31 Mar 2026 10:01:59 +0200 > Michel Dänzer wrote: >> On 3/26/26 14:53, Pekka Paalanen wrote: >>> On Tue, 24 Mar 2026 17:44:21 +0100 >>> Michel Dänzer wrote: >>> >>>> * There's no clear use case. >>>> >>>> This is generally a requirement for new KMS UAPI. >>>> >>>> The practical usefulness of the corresponding weston MR is dubious >>>> per the concern above. >>> >>> I think the example of RGB 10 bpc to be degraded to YCbCr 10 bpc >>> rather than RGB 8 bpc is an excellent use case. >> >> This series and the corresponding Weston MR aren't enough to address >> that use case though, are they? All they achieve is logging a >> potentially misleading warning. >> >> It might make sense to combine this series and the Weston MR with >> whatever else is needed for that use case. > > What do you believe is missing? For the stated use case, e.g. a mechanism to control RGB vs YCbCr? > Informing the user that the display quality may not be as expected is > the point. The warning implies that the "link bpc" value is expected to match the "max bpc" value, which generally isn't the case. >>> I had another use case in >>> https://gitlab.freedesktop.org/wayland/weston/-/merge_requests/1850#note_3115686 >> >> That would need to take dithering into account as well? > > Yes, dithering could be an adverse effect or not sufficient. Hence the > 'link bpc' property should not consider any kind of dithering, to be on > the safe side. I fully expect dithering to become explicitly > controllable, as policy belongs in userspace. I agree that would be ideal, alas it's not current reality. -- Earthling Michel Dänzer \ GNOME / Xwayland / Mesa developer https://redhat.com \ Libre software enthusiast