Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
MIME-Version: 1.0
References: <20210910130337.2025426-1-osk@google.com> <71c17c47-ca9e-e9d2-7b89-cc25b512c06a@roeck-us.net>
In-Reply-To: <71c17c47-ca9e-e9d2-7b89-cc25b512c06a@roeck-us.net>
From:   Oskar Senft <osk@google.com>
Date:   Fri, 10 Sep 2021 16:44:54 -0400
Message-ID: <CABoTLcRZ43EUVzbqWniu64PkB7Yx4RMYKjaBxaSihk+k0Ca-gA@mail.gmail.com>
Subject: Re: [PATCH] dt-bindings: hwmon: Add nct7802 bindings
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     linux-hwmon@vger.kernel.org, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org, Jean Delvare <jdelvare@suse.com>,
        Rob Herring <robh+dt@kernel.org>
Content-Type: text/plain; charset="UTF-8"
Precedence: bulk

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.