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 C7286CCA470 for ; Wed, 8 Oct 2025 01:38:16 +0000 (UTC) Received: from gabe.freedesktop.org (localhost [127.0.0.1]) by gabe.freedesktop.org (Postfix) with ESMTP id 19A7910E025; Wed, 8 Oct 2025 01:38:16 +0000 (UTC) Authentication-Results: gabe.freedesktop.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.b="CHSf5Uj9"; dkim-atps=neutral Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by gabe.freedesktop.org (Postfix) with ESMTPS id 3149910E025 for ; Wed, 8 Oct 2025 01:38:15 +0000 (UTC) Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 268DB604FB; Wed, 8 Oct 2025 01:38:14 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9ED1EC4CEF1; Wed, 8 Oct 2025 01:38:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1759887493; bh=g9HKatffLmG7PZQzs7MEvfVFFeFvciAqfzfnc7tu7pA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=CHSf5Uj926ugwsG9Rn6jt2cBtFtu+AtRIRoqF+rz047j4GZ/y2ofcRmbk3B+azBPr uYqvq5Iv65Ae4qpDrJh24qZXGZzIpN2QSOMmbKcdc+D8ve/hTD1w/oAPyPuLRutsCi h5I033Go4OIDSyU7oBgNKXKzLJrFlAZYbFT/kT8TBewVXQPU7Xkxo8jwBaC8fg59uY DdrM+jGI1q9Dqmc8TO8e6pbEmqzVZlvfSwy/Oy5qLy/Q88V1FN8HZNUPQsd3KyU6Rk xx2Zhjb70Dy3EEkQjN6Z0synZrCxy51HZE8GtT3vevmzzDhHrob7EvltEykGDj3+3f 3kb1jhS3/zdXQ== Date: Tue, 7 Oct 2025 20:38:12 -0500 From: Rob Herring To: Svyatoslav Ryhel Cc: Doug Anderson , Neil Armstrong , Jessica Zhang , Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Krzysztof Kozlowski , Conor Dooley , Thierry Reding , Jonathan Hunter , Sam Ravnborg , dri-devel@lists.freedesktop.org, devicetree@vger.kernel.org, linux-kernel@vger.kernel.org, linux-tegra@vger.kernel.org Subject: Re: [PATCH v1 1/8] dt-bindings: display: panel: properly document LG LD070WX3 panel Message-ID: <20251008013812.GA1911585-robh@kernel.org> References: <20250929142455.24883-1-clamor95@gmail.com> <20250929142455.24883-2-clamor95@gmail.com> <20251006221308.GA653118-robh@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-BeenThere: dri-devel@lists.freedesktop.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Direct Rendering Infrastructure - Development List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" On Tue, Oct 07, 2025 at 08:24:06AM +0300, Svyatoslav Ryhel wrote: > вт, 7 жовт. 2025 р. о 01:13 Rob Herring пише: > > > > On Thu, Oct 02, 2025 at 02:35:42PM -0700, Doug Anderson wrote: > > > Hi, > > > > > > On Mon, Sep 29, 2025 at 10:03 PM Svyatoslav Ryhel wrote: > > > > > > > > вт, 30 вер. 2025 р. о 06:12 Doug Anderson пише: > > > > > > > > > > Hi, > > > > > > > > > > On Mon, Sep 29, 2025 at 7:25 AM Svyatoslav Ryhel wrote: > > > > > > > > > > > > LG LD070WX3-SL01 was mistakenly documented as a simple DSI panel, which it > > > > > > clearly is not. Address this by adding the proper schema for this panel. > > > > > > > > > > > > Signed-off-by: Svyatoslav Ryhel > > > > > > --- > > > > > > .../bindings/display/panel/lg,ld070wx3.yaml | 60 +++++++++++++++++++ > > > > > > .../display/panel/panel-simple-dsi.yaml | 2 - > > > > > > 2 files changed, 60 insertions(+), 2 deletions(-) > > > > > > create mode 100644 Documentation/devicetree/bindings/display/panel/lg,ld070wx3.yaml > > > > > > > > > > > > diff --git a/Documentation/devicetree/bindings/display/panel/lg,ld070wx3.yaml b/Documentation/devicetree/bindings/display/panel/lg,ld070wx3.yaml > > > > > > new file mode 100644 > > > > > > index 000000000000..0a82cf311452 > > > > > > --- /dev/null > > > > > > +++ b/Documentation/devicetree/bindings/display/panel/lg,ld070wx3.yaml > > > > > > @@ -0,0 +1,60 @@ > > > > > > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause) > > > > > > +%YAML 1.2 > > > > > > +--- > > > > > > +$id: http://devicetree.org/schemas/display/panel/lg,ld070wx3.yaml# > > > > > > +$schema: http://devicetree.org/meta-schemas/core.yaml# > > > > > > + > > > > > > +title: LG Corporation 7" WXGA TFT LCD panel > > > > > > + > > > > > > +maintainers: > > > > > > + - Svyatoslav Ryhel > > > > > > + > > > > > > +allOf: > > > > > > + - $ref: panel-common.yaml# > > > > > > + > > > > > > +properties: > > > > > > + compatible: > > > > > > + items: > > > > > > + - const: lg,ld070wx3-sl01 > > > > > > + > > > > > > + reg: > > > > > > + maxItems: 1 > > > > > > + > > > > > > + vdd-supply: true > > > > > > + vcc-supply: true > > > > > > + > > > > > > + backlight: true > > > > > > + port: true > > > > > > + > > > > > > +required: > > > > > > + - compatible > > > > > > + - vdd-supply > > > > > > + - vcc-supply > > > > > > > > > > I suspect you'll get a NAK here because you're not preserving backward > > > > > compatibility for existing device trees. While there can sometimes be > > > > > reasons to do that, you'd need to provide a very strong justification. > > > > > > > > > > > > > > > It seems like instead of breaking compatibility you could just have > > > > > two supplies: > > > > > > > > > > * power-supply - The name for the "dvdd" supply. > > > > > * avdd-supply - The name for the "avdd" supply. > > > > > > > > > > ...and then you make both of them not "required". Maybe you'd add some > > > > > documentation saying that things might not work 100% correctly if they > > > > > weren't provided but that old device trees didn't specify them? > > > > > > > > Schema describes hardware. If it does not (and in this case it clearly > > > > DOES NOT), then such schema should be adjusted according to hardware. > > > > The priority is: > > > > 1) ABI > > 2) describe h/w accurately > > > > IMO, if there are 2 rails on the h/w and you have 2 supplies in the DT, > > then you have described the h/w. names are less important. > > > > > > If there are any users of such binding, they should be adjusted too > > > > (third commit of this patchset does exactly that). Panel datasheet is > > > > explicit, panel has ONLY vdd supply and vcc supply, names are taken > > > > from there too. > > > > > > I'm more than happy to defer to DT people on this, but the general > > > argument is that "device tree" is supposed to remain forever forward > > > compatible. In other words, someone could have taken a snapshot of the > > > "tegra114-tn7.dts" device tree at any point in time and then shipped > > > it in some BIOS. Presumably the old "tegra114-tn7.dts" (for some > > > reason) managed to init the panel properly in the past and the idea is > > > that there should still be a way to init the panel with the old device > > > tree now. > > > > > > Obviously, that's an ideal version of the world and sometimes > > > hard/impossible to make a reality, but it's supposed to be what we > > > strive for. > > > > > > >From a more practical standpoint, the dts changes and code changes > > > will go through different trees and so making them mutually depend on > > > each other can leave people broken if they happen to have one patch > > > but not the other. > > > > > > I suppose one way to handle this (if DT people like it) is to keep the > > > bindings the way you have it but then add some layer of backward > > > compatibility in the driver. It will mean that anyone with the old DTS > > > would officially not "validate" properly against the new bindings, but > > > I think that could be OK as long as it was explicitly mentioned in the > > > commit message. Obviously, though, DT bindings reviewers would have > > > the last word there... > > > > That's fine, but then I prefer we keep 'power-supply' as deprecated. > > Then if we ever validate that drivers only use documented properties, > > it would pass. We already check drivers use documented compatible > > strings, so that wouldn't be too hard to do. > > > > Sure, but ATM there is only one user of this compatible in the > mainline Linux kernel, which is Nvidia tablet Tegra Note 7 and: > > 1. Node used in its tree is addressed in the third commit of this patchset > 2. Its panel is broken anyway since it cannot init properly if > bootloader does not leave a pre-inited panel, it cannot suspend > properly and it has a loose regulator which relies on always-on > property rather then being hooked to the panel. Then put all this justification in the commit message. > I can assure you that besides me there seems to be no one interested > in this tablet. Okay, then it is on you if anyone does care. Rob