linux-kernel - Re: [PATCH] dt-bindings: iio: afe: voltage-divider: Add io-channel-cells

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Date: Fri, 26 Jan 2024 16:51:55 +0000
From: Conor Dooley <conor@...nel.org>
To: Naresh Solanki <naresh.solanki@...ements.com>
Cc: Peter Rosin <peda@...ntia.se>, Jonathan Cameron <jic23@...nel.org>,
	Lars-Peter Clausen <lars@...afoo.de>,
	Rob Herring <robh+dt@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>, mazziesaccount@...il.com,
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dt-bindings: iio: afe: voltage-divider: Add
 io-channel-cells

On Fri, Jan 26, 2024 at 09:55:20PM +0530, Naresh Solanki wrote:
> On Fri, 26 Jan 2024 at 21:47, Conor Dooley <conor@...nel.org> wrote:
> > On Fri, Jan 26, 2024 at 05:25:08PM +0530, Naresh Solanki wrote:
> > > Signed-off-by: Naresh Solanki <naresh.solanki@...ements.com>
> > > ---
> > >  Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml | 3 +++
> > >  1 file changed, 3 insertions(+)
> > >
> > > diff --git a/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml b/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml
> > > index dddf97b50549..b4b5489ad98e 100644
> > > --- a/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml
> > > +++ b/Documentation/devicetree/bindings/iio/afe/voltage-divider.yaml
> > > @@ -39,6 +39,9 @@ properties:
> > >      description: |
> > >        Channel node of a voltage io-channel.
> > >
> > > +  '#io-channel-cells':
> > > +    const: 1
> >
> > The example in this binding looks like the voltage-divider is intended
> > to be an "IIO consumer" but "#io-channels-cells" is an "IIO provider"
> > property.
> >
> > Are you sure this is correct?
> I'm not aware that #io-channels-cells is only for IIO provider.

#foo-cells properties are always for resource providers

> But I do get some kernel message as mention in commit messages
> if this is specified in DT.

Can you please share the DT in question? Or at least, the section that
describes the IIO provider and consumer?

It should look like the example:

    spi {
        #address-cells = <1>;
        #size-cells = <0>;
        adc@0 {
            compatible = "maxim,max1027";
            reg = <0>;
            #io-channel-cells = <1>;
            interrupt-parent = <&gpio5>;
            interrupts = <15 IRQ_TYPE_EDGE_RISING>;
            spi-max-frequency = <1000000>;
        };
    };

    sysv {
        compatible = "voltage-divider";
        io-channels = <&maxadc 1>;

        /* Scale the system voltage by 22/222 to fit the ADC range. */
        output-ohms = <22>;
        full-ohms = <222>; /* 200 + 22 */
    };

Thanks,
Conor.

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