linux-kernel - Re: [PATCH v1] ACPI: video: Fix missing backlight node creation on

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Message-Id: <20250912103538.3657242-1-zhangzihuan@kylinos.cn>
Date: Fri, 12 Sep 2025 18:35:38 +0800
From: Zihuan Zhang <zhangzihuan@...inos.cn>
To: hansg@...nel.org
Cc: lenb@...nel.org,
	linux-acpi@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	mario.limonciello@....com,
	rafael@...nel.org,
	stable@...r.kernel.org,
	zhangzihuan@...inos.cn
Subject: Re: [PATCH v1] ACPI: video: Fix missing backlight node creation on

> 1. There must be a GPU driver for these laptops somewhere?
> Even if out of tree using a laptop without a GPU these days
> just does not give a good user experience. So fix the GPU
> driver to call acpi_video_register_backlight().
> 
> Note acpi_video_register_backlight() is deliberately exported
> without requiring the consuming out of tree kernel module to
> be GPL to allow this.
> 
> Other options would be:
> 
> 2. Add some special heuristics for Zhaoxin CPUs,
> the kernel already has a CPUID match mechanism for
> things like this. This could potentially be combined
> with a DMI system-vendor check to only do this special
> case handling on e.g. Lenovo and Inspur laptops.
> 
> 3. Instead of adding the CPU-id based special case
> just outright use DMI quirks. In this case lets try
> to use substring matches to cover multiple models
> with a single entry so as to not grow the quirk
> table too much.


Got it, thanks!

In fact, we have tried a few approaches (cmdline option, CPU-ID based quirk, and DMI quirk),
and all of them work. 
I will sync this information with Zhaoxin to see which way they prefer.