Re: [PATCH v3] hwmon: (cros_ec) Add set and get target fan RPM function

[Guenter Roeck]

On 3/22/25 06:55, Thomas Weißschuh wrote:
> On 2025-03-18 15:45:23+0800, Sung-Chi Li wrote:
> > The ChromeOS embedded controller (EC) supports closed loop fan speed
> > control, so add the fan target attribute under hwmon framework, such
> > that kernel can expose reading and specifying the desired fan RPM for
> > fans connected to the EC.
> >
> > When probing the cros_ec hwmon module, we also check the supported
> > command version of setting target fan RPM. This commit implements the
> > version 0 of getting the target fan RPM, which can only read the target
> > RPM of the first fan. This commit also implements the version 1 of
> > setting the target fan RPM to each fan respectively.
> >
> > Signed-off-by: Sung-Chi Li <lschyi@xxxxxxxxxxxx>
> > ---
> > ChromeOS embedded controller (EC) supports closed-loop fan control. We
> > anticipate to have the fan related control from the kernel side, so this
> > series register the HWMON_F_TARGET attribute, and implement the read and
> > write function for setting/reading the target fan RPM from the EC side.
>
> Should it be possible to switch back to automatic control?
> I can't find anything in the hwmon ABI about it.
> And neither in the CrOS EC source.
>
> Am I missing something?

Not sure I understand the context, but the fan control method is normally
selected with pwmX_enable, which is defined as

                Fan speed control method:

                - 0: no fan speed control (i.e. fan at full speed)
                - 1: manual fan speed control enabled (using `pwmY`)
                - 2+: automatic fan speed control enabled

Guenter