Re: [PATCH v1 3/5] ABI: iio: add new ABI doc for mhz19b

[Jonathan Cameron <jic23@kernel.org>]

On Mon, 7 Apr 2025 11:10:21 +0900
gyeyoung <gye976@gmail.com> wrote:

> Hello Jonathan,
> 
> 
> > > > Actually - any idea what the gain is doing?  Is it adjusting a analog
> > > > amplfier, or messing with the integration time (I have little idea
> > > > how these sensors work!)
> > > >  
> > > sorry, I'm not affiliated with the vendor,
> > > so I do not have any information other than the datasheet.
> > > And the datasheet doesn't specify any trade-offs related to adjusting the range.
> > > (only "± (50ppm+3% reading value)" is here)
> > >
> > > I think this range setting would be better implemented in
> > > some other way (like module parameter) rather than IIO subsystem.  
> >
> > I'm not in general keen on module parameters effecting policy (and noise
> > vs range is definitely a policy thing) so I think we would want to figure out
> > a suitable sysfs ABI.  
> 
> Or, how about adding IIO_CHAN_INFO_RANGE to the
> iio_chan_info_postfix[] array for range setting?
> I think there might be examples of devices that expand the range
> without affecting scaling,
> like this device (though I haven’t found a case yet...)
> 
> If this is a valid approach, would it be okay if I submit a patch for it?

No. The reason isn't technical, but rather that if we provide that
we'll spend years explaining to people that _scale is the right
choice if the _scale is 1/_range (or similar).

Even without making it easy a lot of drivers try to do that!

I think leave it as an open question for the future for now.

Jonathan

> 
> Regards,
> Gyeyoung
>