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

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Date:   Thu, 16 Sep 2021 20:29:09 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Oskar Senft <osk@...gle.com>
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

On Thu, Sep 16, 2021 at 11:09:16PM -0400, Oskar Senft wrote:
> Ok, I experimented with that and I think I'm starting to get an idea
> how the DT bindings YAML works.
> 
> > > Yes, let's do that. I'd like us to keep the "sensors" subnode to have a clear
> > > association and differentiator to other sub-nodes such as "regulators".
> > > Open is if we can use "temperature-sensor@0" or if it would have to be
> > > a chip specific "ltd", but I think we can sort that out after suggesting
> > > an initial set of bindings to Rob.
> 
> However, I found that when I use the name@x syntax, the schema
> validator also requires the use of a reg or ranges property. But then
> doing so requires to set the #address-cells and #size-cells
> properties, which - I think - makes things weird.
> 
> So these two examples are options that validate:
>     i2c {
>         #address-cells = <1>;
>         #size-cells = <0>;
> 
>         nct7802@28 {
>             compatible = "nuvoton,nct7802";
>             reg = <0x28>;
> 
>             temperature-sensors {
>                 ltd {
>                   status = "disabled";
>                   label = "mainboard temperature";
>                 };
> 
>                 rtd1 {
>                   status = "okay";
>                   label = "inlet temperature";
>                   type = <4> /* thermistor */;
>                 };
>             };
>         };
>     };
> 
> or
> 
>     i2c {
>         #address-cells = <1>;
>         #size-cells = <0>;
> 
>         nct7802@28 {
>             compatible = "nuvoton,nct7802";
>             reg = <0x28>;
> 
>             temperature-sensors {
>                 #address-cells = <1>;
>                 #size-cells = <0>;
> 
>                 sensor@0 {
>                   reg = <0>;
>                   status = "disabled";
>                   label = "mainboard temperature";
>                 };
> 
>                 sensor@1 {
>                   reg = <1>;
>                   status = "okay";
>                   label = "inlet temperature";
>                   type = <4> /* thermistor */;
>                 };
>             };
>         };
>     };
> 
> In the second case we end up having to duplicate information, i.e.
> "sensor@1" and "reg = <1>". Also, I have not yet found a way to
> validate that the "@x" is identical to the "reg = <x>". I believe that
> this is just how it is in device trees, but I want to make sure this
> is what we want?
> 
> Thoughts?
> 
Comparing those two, I prefer the first option. Can you write that up
in a yaml file to present to Rob ? If he doesn't like it, we can still
suggest the second variant as an alternative.

Thanks,
Guenter