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

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Message-ID: <0b214249-958c-4e14-a4d8-512f1d90dff4@kernel.org>
Date: Thu, 18 Sep 2025 09:33:51 +0200
From: Hans de Goede <hansg@...nel.org>
To: Zihuan Zhang <zhangzihuan@...inos.cn>
Cc: lenb@...nel.org, linux-acpi@...r.kernel.org,
 linux-kernel@...r.kernel.org, mario.limonciello@....com, rafael@...nel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH v1] ACPI: video: Fix missing backlight node creation on

Hi Zihuan,

On 18-Sep-25 2:36 AM, Zihuan Zhang wrote:
> 
> 在 2025/9/12 18:35, Zihuan Zhang 写道:
>>> 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.
> 
> Zhaoxin has confirmed that they will handle this through their own GPU driver.

That is good to hear, thank you for the update.

Regards,

Hans