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

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Message-ID: <ZR0PZ+RHzfbrlbnI@octopus>
Date:   Wed, 4 Oct 2023 16:08:23 +0900
From:   AKASHI Takahiro <takahiro.akashi@...aro.org>
To:     Linus Walleij <linus.walleij@...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

On Tue, Oct 03, 2023 at 03:16:49PM +0200, Linus Walleij wrote:
> 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...)

Ah, thank you.

> 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?

If you like :)
As I said, I was not confident that the driver be applicable
to other pinctrl-gpio cases.

> (...)
> > +++ 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'm not so ambitious.

> (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.)

Okay.

> > +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.

By following other gpio drivers' bindings, I will drop this rule.

> > +  compatible:
> > +    const: arm,scmi-gpio-generic
> 
> const: pin-control-gpio
> 
> Other than that I am aboard with the solution!

Hope that the driver works on real hardware :)

-Takahiro Akashi

> Yours,
> Linus Walleij