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

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Message-ID: <CAJZ5v0juvqnn0A7pwpijhWkLDZB8U31T3J96a_Cr_RPN8C88iw@mail.gmail.com>
Date: Mon, 27 Oct 2025 20:58:04 +0100
From: "Rafael J. Wysocki" <rafael@...nel.org>
To: Armin Wolf <W_Armin@....de>
Cc: rafael@...nel.org, lenb@...nel.org, linux-acpi@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 0/3] ACPI fan _DSM support

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!