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

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Message-ID: <CACRpkdb1-LXwLdV3qLMc+i_VaLoJ-mTs=+0QtuJtNaQR_xVpxQ@mail.gmail.com>
Date:   Wed, 31 Aug 2022 15:26:24 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     Martyn Welch <martyn.welch@...labora.com>,
        Bartosz Golaszewski <brgl@...ev.pl>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        kernel@...labora.com, linux-gpio@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/5] dt-bindings: gpio: pca95xx: add entry for pcal6534
 and PI4IOE5V6534Q

On Tue, Aug 30, 2022 at 9:50 AM Krzysztof Kozlowski
<krzysztof.kozlowski@...aro.org> wrote:
> On 29/08/2022 16:39, Martyn Welch wrote:
> > 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.
> >
> > Signed-off-by: Martyn Welch <martyn.welch@...labora.com>
>
> Then diodes should be followed by fallback (and use only one compatible
> to bind).

Ugh I don't think we have done a very good job at providing fallbacks
(several compatibles) for this hardware. Just looking at the list makes
me suspicious.

The fallback scheme is pretty hard to maintain when vendors are a bit
unclear on whether things are really compatible or not, and sometimes
they are compatible but rather not say :(

Yours,
Linus Walleij