Re: [PATCH 2/2] iio: temperature: ltc2983: Add support for ADT7604

[Nuno Sá]

On Tue, May 12, 2026 at 11:55:21AM +0000, Stan, Liviu wrote:
> On Tue, May 12, 2026, Nuno Sá wrote:
> > > > > The current approach presents it as IIO_TEMP since the chip outputs
> > > > > coverage (using the custom table interpolation) via the temperature 
> > > > > result bank, not the resistance bank, but I agree a new channel type
> > > > > makes sense. Should I create a specific type like
> > > > > IIO_COVERAGE_PERCENT or would a general IIO_PERCENTAGE 
> > > > > be better?
> > > >
> > > > For ABI purposes we don't care where it comes from.
> > > >
> > > > We already have some 'ratio' type measurements like concentration which
> > > > are percentages and similar to those I think we need some indication of 'what'
> > > > is being measured given it's unit free.  Hence IIO_COVERAGE_PERCENT
> > > > seems the better choice to me.
> > >
> > > Understood. Will do that in v2.
> > 
> > I do wonder if a complete type is what we want? How will we present it?
> > 
> > in_coverage_ratio?
> > 
> > What I'm not too convinced is that coverage is relative to what? Well
> > it's a percentage so I guess we could not care and leave interpretation to
> > userspace (to know which device is dealing with). Still I wonder if a
> > new iio_chan_info wouldn't be more appropriate? In this case applied to
> > iio_resistance. So something like:
> > 
> > in_resistance_coverage_ratio
> > 
> > So it's clear what physical quantity coverage ratio is affecting.
> 
> I still think a new channel type is the right approach. Consider copper 
> trace sensors - they also support a custom table, and when one is 
> provided the chip outputs both a resistance result and a temperature 
> result (the interpolation output), each in their own register bank. The 
> current approach handles that with separate IIO_RESISTANCE and 
> IIO_TEMP channels. So, for consistency, if we use a chan_info 
> attribute for the leak detector coverage output, we would need to do
> the same for the copper trace temperature output. Since IIO_TEMP
> makes sense for the interpolation result for copper traces and
> because it is a distinct physical quantity output by the chip, I think it
> would make the most sense that leak detectors follow the same
> pattern and create a separate IIO channel.
> 
> What do you think?
> 

Yeah, makes sense. Jonathan already put it very nicely for the distinct
channel case.

- Nuno Sá