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[2001:1c00:c1e:bf00:d69d:5353:dba5:ee81]) by smtp.gmail.com with ESMTPSA id i14-20020a50c3ce000000b004587c2b5048sm739068edf.52.2022.10.27.03.37.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 27 Oct 2022 03:37:50 -0700 (PDT) Message-ID: <6df2016d-ed2d-57fa-dcad-48537732895f@redhat.com> Date: Thu, 27 Oct 2022 12:37:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.3.1 Subject: Re: [PATCH v5 02/31] drm/i915: Don't register backlight when another backlight should be used (v2) To: Matthew Garrett References: <20221025193248.GA21457@srcf.ucam.org> <144cd47e-42dc-2b84-1a90-ea5e080e08a3@redhat.com> <20221025204043.GA23306@srcf.ucam.org> <20221025234040.GA27673@srcf.ucam.org> <20221026204920.GA15326@srcf.ucam.org> <099dee98-8aeb-af36-828c-110f5ac6e9a3@redhat.com> <20221027091123.GA28089@srcf.ucam.org> <933be908-0bc2-56cc-8d6f-38f2d208ef20@redhat.com> <20221027095249.GA28666@srcf.ucam.org> From: Hans de Goede In-Reply-To: <20221027095249.GA28666@srcf.ucam.org> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US, nl Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit 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: , Cc: Karol Herbst , "Rafael J . Wysocki" , nouveau@lists.freedesktop.org, dri-devel@lists.freedesktop.org, platform-driver-x86@vger.kernel.org, Dmitry Osipenko , amd-gfx@lists.freedesktop.org, linux-acpi@vger.kernel.org, Ben Skeggs , David Airlie , Len Brown , Daniel Dadap , Jani Nikula , intel-gfx , Mark Gross , Rodrigo Vivi , Mika Westerberg , Andy Shevchenko , Tvrtko Ursulin , Xinhui , Thomas Zimmermann , Alex Deucher , =?UTF-8?Q?Christian_K=c3=b6nig?= Errors-To: dri-devel-bounces@lists.freedesktop.org Sender: "dri-devel" Hi, On 10/27/22 11:52, Matthew Garrett wrote: > On Thu, Oct 27, 2022 at 11:39:38AM +0200, Hans de Goede wrote: > >> The *only* behavior which actually is new in 6.1 is the native GPU >> drivers now doing the equivalent of: >> >> if (acpi_video_get_backlight_type() != acpi_backlight_native) >> return; >> >> In their backlight register paths (i), which is causing the native >> backlight to disappear on your custom laptop setup and on Chromebooks >> (with the Chromebooks case being already solved I hope.). > > It's causing the backlight control to vanish on any machine that isn't > ((acpi_video || vendor interface) || !acpi). Most machines that fall > into that are either weird or Chromebooks or old, but there are machines > that fall into that. I acknowledge that their are machines that fall into this category, but I expect / hope there to be so few of them that we can just DMI quirk our way out if this. I believe the old group to be small because: 1. Generally speaking the "native" control method is usually not present on the really old (pre ACPI video spec) mobile GPUs. 2. On most old laptops I would still expect there to be a vendor interface too, and if both get registered standard desktop environments will prefer the vendor one, so then we need a native DMI quirk to disable the vendor interface anyways and we already have a bunch of those, so some laptops in this group are already covered by DMI quirks. And a fix for the Chromebook case is already in Linus' tree, which just leaves the weird case, of which there will hopefully be only a few. I do share your worry that this might break some machines, but the only way to really find out is to get this code out there I'm afraid. I have just written a blog post asking for people to check if their laptop might be affected; and to report various details to me of their laptop is affected: https://hansdegoede.dreamwidth.org/26548.html Lets wait and see how this goes. If I get (too) many reports then I will send a revert of the addition of the: if (acpi_video_get_backlight_type() != acpi_backlight_native) return; check to the i915 / radeon / amd / nouveau drivers. (And if I only get a couple of reports I will probably just submit DMI quirks for the affected models). Regards, Hans