Re: [PATCH v2 0/6] ACPI fan _DSM support

[Armin Wolf]

Am 23.10.25 um 21:22 schrieb Rafael J. Wysocki:

> On Thu, Oct 23, 2025 at 11:59 AM Rafael J. Wysocki <rafael@xxxxxxxxxx> wrote:
> > On Wed, Oct 22, 2025 at 11:41 PM Armin Wolf <W_Armin@xxxxxx> 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
> I've applied two first patches for 6.19 and the third one for 6.18-rc, as a fix.

Please note that the third patch depends on the first patch! Otherwise you will
get a runtime error when acpi_fan_hwmon_read() tries to cast the platform device
to a ACPI device.

> My understanding is that patches [4-5/6] are preparations for the last
> one that needs a pointer to the MSFT documentation it is based on.

I understand, i will send a v3 series without the first three patch and this
issue being addressed.

Thanks,
Armin Wolf