linux-kernel - Re: [PATCH v2 0/6] ACPI fan

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Message-ID: <CAJZ5v0h8w0wrO5ziqQchN_f5Cb=Duqfc6=uOzR_-pk5_UcJ95g@mail.gmail.com>
Date: Thu, 23 Oct 2025 11:59:40 +0200
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 v2 0/6] ACPI fan _DSM support

On Wed, Oct 22, 2025 at 11:41 PM Armin Wolf <W_Armin@....de> wrote:
>
> Am 08.10.25 um 01:41 schrieb Armin Wolf:
>
> > 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 patch performs a simple cleanup in order to reduce the usage
> > of the acpi_device struct. The second patch fixes an issue with some
> > 64-bit ACPI implementations where an invalid value was reported
> > instead of the standard ACPI placeholder value (0xFFFFFFFF). The third
> > patch fixes an unrelated issue inside the hwmon support code while the
> > next 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.
>
> Any thought on this?

Not yet, but I'm going to get to it today.

> I tested it with a custom SSDT, so i can prove that those patches work.

OK