linux-kernel - Re: [PATCH v2 2/5] dt-bindings: gpio: pca95xx: add entry for pcal6534 and PI4IOE5V6534Q

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Date:   Tue, 6 Sep 2022 15:08:00 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Andy Shevchenko <andriy.shevchenko@...el.com>
Cc:     Martyn Welch <martyn.welch@...labora.co.uk>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Martyn Welch <martyn.welch@...labora.com>,
        Krzysztof Kozlowski <krzk@...nel.org>,
        linux-gpio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/5] dt-bindings: gpio: pca95xx: add entry for pcal6534
 and PI4IOE5V6534Q

On Tue, Sep 6, 2022 at 2:19 PM Andy Shevchenko
<andriy.shevchenko@...el.com> wrote:
> On Tue, Sep 06, 2022 at 09:28:16AM +0100, Martyn Welch wrote:
> > From: Martyn Welch <martyn.welch@...labora.com>
> >
> > The NXP PCAL6534 is a 34-bit I2C I/O expander similar to the PCAL6524. The
> > Diodes PI4IOE5V6534Q is a functionally identical chip provided by Diodes
> > Inc.
>
> ...
>
> > +    oneOf:
> > +      - items:
> > +        - const: diodes,pi4ioe5v6534q
> > +        - const: nxp,pcal6534
>
> ^^^
>
> > +      - items:
> > +        - enum:
>
> > +          - nxp,pcal6534
>
> ^^^
>
> Not sure why is this dup?

No that is how DT compatibles work. One version of the component,
bought from NXP will look like this:

compatible = "nxp,pcal6534";

Another version bought from diodes will look like this:

compatible = "diodes,pi4ioe5v6534q", "nxp,pcal6534";

Then the drivers are probed matching from left to right,
with the "most compatible" matching first.

This also answers your question on the implementation.

Yours,
Linus Walleij