linux-kernel - Re: [PATCH v3 0/3] ACPI fan

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Message-ID: <b90f5014-85b1-48a3-8dd4-e8216e129c9b@gmx.de>
Date: Mon, 27 Oct 2025 21:28:37 +0100
From: Armin Wolf <W_Armin@....de>
To: "Rafael J. Wysocki" <rafael@...nel.org>
Cc: lenb@...nel.org, linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/3] ACPI fan _DSM support

Am 27.10.25 um 20:58 schrieb Rafael J. Wysocki:

> On Fri, Oct 24, 2025 at 8:38 PM Armin Wolf <W_Armin@....de> wrote:
>> Microsoft has designed a _DSM interface for the ACPI fan device [1]
>> that allows the OS to set fan speed trip points. The ACPI firmware
>> will notify the ACPI fan device when said trip points are triggered.
>>
>> Unfortunately some device manufacturers (like HP) blindly assume that
>> the OS will use this _DSM interface and thus only update the fan speed
>> value returned by the _FST control method when sending a notification
>> to the ACPI fan device. This results in stale fan speed values being
>> reported by the ACPI fan driver [2].
>>
>> The first two patches add support for the ACPI fan notifications as
>> specified in ACPI 11.2.3. The last patch finally adds support for the
>> Microsoft _DSM interface.
>>
>> All patches where tested with a custom SSDT [3] and the acpi_call [4]
>> kernel module and appear to work just fine.
>>
>> [1] https://learn.microsoft.com/en-us/windows-hardware/design/device-experiences/design-guide
>> [2] https://github.com/lm-sensors/lm-sensors/issues/506
>> [3] https://github.com/Wer-Wolf/acpi-fan-ssdt/blob/master/ssdt-dsm.asl
>> [4] https://github.com/nix-community/acpi_call
>>
>> Changes since v2:
>> - drop already merged patches
>> - add links to the MSFT documentation in patch 3
>>
>> Changes since v1:
>> - use acpi_evaluate_dsm_typed() during _DSM initialization
>> - send ACPI netlink event when after handling a ACPI notification
>>
>> Armin Wolf (3):
>>    ACPI: fan: Add basic notification support
>>    ACPI: fan: Add hwmon notification support
>>    ACPI: fan: Add support for Microsoft fan extensions
> All applied as 6.19 material, thanks!

Thank you :)