Re: [PATCH 05/10] hwmon: generic-pwm-tachometer: Add generic PWM based tachometer

[Laxman Dewangan]

On Wednesday 07 March 2018 07:50 PM, Guenter Roeck wrote:
> On 03/07/2018 01:47 AM, Rajkumar Rampelli wrote:
> > > While I am not opposed to ABI changes, the merits of those would 
> > > need to be
> > > discussed on the mailing list. But replacing "fan1_input" with "rpm" is
> > > not an acceptable ABI change, even if it may measure something that 
> > > turns
> > > but isn't a fan.
> > >
> > > If this _is_ in fact supposed to be used for something else but 
> > > fans, we
> > > would have to discuss what that might be, and if hwmon is the 
> > > appropriate
> > > subsystem to measure and report it. This does to some degree lead 
> > > back to
> > > my concern of having the "fan" part of this patch series in the pwm 
> > > core.
> > > I am still not sure if that makes sense.
> > >
> > > Thanks,
> > > Guenter
> > I am planning to add tachometer support in pwm-fan.c driver 
> > (drivers/hwmon/) instead of adding new generic-pwm-tachometer.c 
> > driver. Measuring RPM value will be done in pwm-fan driver itself 
> > using pwm capture feature and will add new sysfs attributes under 
> > this driver to report rpm value of fan.
>
> There is an existing attribute to report the RPM of fans. It is called 
> fan[1..n]_input.
>
> "replacing "fan1_input" with "rpm" is not an acceptable ABI change"
>
> Preemptive NACK.

The RPM is measured speed via PWM signal capture  which is output from fan.
So should we have the fan[1..n]_output_rpm?