linux-kernel - Re: [RFC 4/4] dt-bindings: gpio: Add bindings for SCMI pinctrl based gpio

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Message-ID: <CACRpkdZgmwhGYH43iAq=cERaGO9a-mVHXG8sQ2htPw0DcrnuNA@mail.gmail.com>
Date:   Tue, 3 Oct 2023 15:16:49 +0200
From:   Linus Walleij <linus.walleij@...aro.org>
To:     AKASHI Takahiro <takahiro.akashi@...aro.org>
Cc:     sudeep.holla@....com, cristian.marussi@....com, robh+dt@...nel.org,
        krzysztof.kozlowski+dt@...aro.org, conor+dt@...nel.org,
        Oleksii_Moisieiev@...m.com, linux-arm-kernel@...ts.infradead.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-gpio@...r.kernel.org
Subject: Re: [RFC 4/4] dt-bindings: gpio: Add bindings for SCMI pinctrl based gpio

Hi Takahiro,

first, thanks for working on this important and crucial driver!

I'll try to clarify and also explain something of what the others
are saying (unless I misunderstand them...)

On Mon, Oct 2, 2023 at 4:17 AM AKASHI Takahiro
<takahiro.akashi@...aro.org> wrote:

> A dt binding for SCMI pinctrl based gpio driver is defined in this
> commit. It basically conforms to generic pinctrl-gpio mapping framework.
>
> Signed-off-by: AKASHI Takahiro <takahiro.akashi@...aro.org>

I think like Christian says that SCMI maybe has nothing to do
with this binding? It is just one possible use case (though we don't know
of any others.) The resource it is using is generic functionality that exist
in any pin controller that provides ways to drive lines high and low
etc.

Would it be named a generic pin control-based GPIO?

(...)
> +++ b/Documentation/devicetree/bindings/gpio/arm,scmi-gpio.yaml
(...)
> +$id: http://devicetree.org/schemas/gpio/arm,scmi-gpio.yaml#

So no ARM, no scmi, just pin-control-gpio.yaml, be bold!

(I like this long unabbreviated name)

> +title: SCMI pinctrl based generic GPIO controller

Pin control-based generic GPIO controller

Add

description:
  The pin control-based GPIO will facilitate a pin controllers ability
  to drive electric lines high/low and other generic properties of a
  pin controller to perform general-purpose one-bit binary I/O.

(At least I think this is the idea, I hope I understand correctly.)

> +properties:
> +  $nodename:
> +    pattern: "^scmi_gpio(@[0-9a-f]+)$"

These nodes are always just named gpio@...
the resource marker is "this is a GPIO" that's all it means.

> +  compatible:
> +    const: arm,scmi-gpio-generic

const: pin-control-gpio

Other than that I am aboard with the solution!

Yours,
Linus Walleij