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

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 8 May 2026 10:19:15 +0100
Nuno Sá <noname.nuno@gmail.com> wrote:

> On Thu, May 07, 2026 at 05:25:58PM +0000, Stan, Liviu wrote:
> > Thank you for the comments, and I apologize for the late reply.
> > 
> > On Mon, Apr 28, 2026,  Nuno Sá wrote:
> > ...  
> > > > Both sensor types expose an IIO_RESISTANCE channel reading from
> > > > the resistance result register bank (0x060-0x00AF), added to
> > > > the regmap readable ranges. Scales are 1/1,024,000 for copper
> > > > trace (result in mOhm) and 1/1024 for leak detector (result
> > > > in Ohm).  
> > > 
> > > But for userspace we report both in Ohm? That's the ABI AFAICT. In DT,
> > > you also mention IIO_TEMP is used:
> > > "IIO_TEMP reports coverage percentage"
> > > 
> > > Can you expand more on what the above means? Are we reporting milli
> > > degrees celcius to userspace?  
> > 
> > Yes, both IIO_RESISTANCE channels report in Ω. The commit message was 
> > misleading, it described the register's native units (mΩ for copper trace,
> > Ω for leak detector), not the userspace output. The scales are chosen to 
> > cancel those units and give Ω in both cases.
> >   
> 
> ack
> 
> > As for the IIO_TEMP question, the chip's custom sensor table stores 
> > temperature in Kelvin (same as the LTC2984 custom RTD table). For the 
> > leak detector, coverage data is encoded as (P + 273.15) K, so when the 
> > chip converts Kelvin to Celsius on output, after the driver applies the 
> > 1000/1024 scale, the IIO output is P * 1000 millidegrees C - 0% reads
> > as ~0 millidegrees, 100% reads as ~100000 millidegrees. But yes, the 
> > actual useable quantity is coverage percentage, not temperature. Is there
> > a more suitable existing IIO channel type for coverage percentage?
> >   
> 
> Will defer this to Jonathan but if we can have a real of the coverage
> given the temperature, I guess this is ok. Given that I think we don't have
> a better channel (unless we add one?) for this. Or just extended_info...
> 

I have no idea what coverage percentage means in this case.
Can you provide some more details or a reference?  Google isn't giving me
anything useful.

> 
> > > I could not find the datasheet so I guess it's not yet public?  
> > 
> > Correct, it is not public yet. Will upload the URL once it is.
> >