linux-kernel - Re: [PATCH] dt-bindings: hwmon: Add nct7802 bindings

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Date:   Fri, 10 Sep 2021 16:44:54 -0400
From:   Oskar Senft <osk@...gle.com>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     linux-hwmon@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, Jean Delvare <jdelvare@...e.com>,
        Rob Herring <robh+dt@...nel.org>
Subject: Re: [PATCH] dt-bindings: hwmon: Add nct7802 bindings

Hi Guenter

Thanks for the quick feedback!

> > +  nuvoton,rtd-modes:
> > +    description: |
> > +      Select modes for the three RTDs.
> > +
> At the very least, "RTD" should be defined. The datasheet doesn't say explicitly,
> but I suspect it means "Remote Temperature Diode".
Ha, good point. As I understand, RTD means "Resistance Temperature
Detector". But TBH, I'm not sure how that squares with Nuvoton's use
of "LTD" for the local sensor ... sigh.

> > +      Valid values for RTD1 and RTD2 are:
> > +        "closed",
> > +        "current",
> > +        "thermistor",
> > +        "voltage"
> I am not sure what "closed" means (the datasheet doesn't say), but I suspect it means
> that the sensor is disabled (?). For the other modes, the translation to the standard
> ABI is:
Thanks for that pointer, I now found that in
Documentation/hwmon/sysfs-interface. Given that there's no definition
for "disabled", I guess I'll just leave that out of the device tree
binding for now? That way we'll stay consistent with the sysfs ABI.

That gives us the following mapping for sysfs / device tree -> nct7802 HW:
2 (3904 transistor) -> 3 (voltage)
3 (thermal diode) -> 1 (current)
4 (thermistor) -> 2 (thermistor)

I'll update the device tree binding to be an array then. I also update
the temp_type functions to support all 3 values.

Oskar.