Re: [PATCH hwmon-next v2 1/1] hwmon: (mlxreg-fan) Use pwm attribute for setting fan speed low limit

[Guenter Roeck <linux@roeck-us.net>]

On Wed, Jan 26, 2022 at 04:18:25PM +0200, Vadim Pasternak wrote:
> Recently 'cur_state' user space 'sysfs' interface 'sysfs' has been
> deprecated. This interface is used in Nvidia systems for setting fan
> speed limit. Currently fan speed limit is set from the user space by
> setting 'sysfs' 'cur_state' attribute to 'max_state + n', where 'n' is
> required limit, for example: 15 for 50% speed limit, 20 for full fan
> speed enforcement.
> The purpose of this feature is to provides ability to limit fan speed
> according to some system wise considerations, like absence of some
> replaceable units (PSU or line cards), high system ambient temperature,
> unreliable transceivers temperature sensing or some other factors which
> indirectly impacts system's airflow.
> 
> The motivation is to support fan low limit feature through 'hwmon'
> interface.
> 
> Use 'hwmon' 'pwm' attribute for setting low limit for fan speed in
> case 'thermal' subsystem is configured in kernel. In this case setting
> fan speed through 'hwmon' will never let the 'thermal' subsystem to
> select a lower duty cycle than the duty cycle selected with the 'pwm'
> attribute.
> From other side, fan speed is to be updated in hardware through 'pwm'
> only in case the requested fan speed is above last speed set by
> 'thermal' subsystem, otherwise requested fan speed will be just stored
> with no PWM update.
> 
> Signed-off-by: Vadim Pasternak <vadimp@nvidia.com>

Applied with minimal change.

Guenter

...
> +		/* Sit minimal PWM speed. */

s/Sit/Set/