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Date:   Sun, 27 Nov 2022 17:42:19 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc:     Samuel Holland <samuel@sholland.org>,
        Lars-Peter Clausen <lars@metafoo.de>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        devicetree@vger.kernel.org, linux-iio@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] dt-bindings: iio: adc: ti,adc081c: Document the binding
Message-ID: <20221127174219.34d0406c@jic23-huawei>
In-Reply-To: <e4be94a3-cdfc-cdf8-5d69-0eef480033f9@linaro.org>
References: <20221125220903.8632-1-samuel@sholland.org>
        <e4be94a3-cdfc-cdf8-5d69-0eef480033f9@linaro.org>
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On Sun, 27 Nov 2022 13:51:19 +0100
Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org> wrote:

> On 25/11/2022 23:09, Samuel Holland wrote:
> > Linux has a driver for these ADCs at drivers/iio/adc/ti-adc081c.c, but
> > the compatible strings were undocumented. Add a binding for them. The
> > hardware has an alert interrupt output, but existing ti,adc081c users
> > do not provide the 'interrupts' property, so leave it as optional.
> > 
> > Signed-off-by: Samuel Holland <samuel@sholland.org>
> > ---
> > 
> >  .../bindings/iio/adc/ti,adc081c.yaml          | 55 +++++++++++++++++++
> >  1 file changed, 55 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/iio/adc/ti,adc081c.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/adc/ti,adc081c.yaml b/Documentation/devicetree/bindings/iio/adc/ti,adc081c.yaml
> > new file mode 100644
> > index 000000000000..caaad777580c
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/adc/ti,adc081c.yaml
> > @@ -0,0 +1,55 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/adc/ti,adc081c.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: TI Single-channel I2C ADCs
> > +
> > +maintainers:
> > +  - Jonathan Cameron <jic23@kernel.org>
> > +  - Lars-Peter Clausen <lars@metafoo.de>
> > +
> > +description: |
> > +  Single-channel ADC supporting 8, 10, or 12-bit samples and high/low alerts.
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - ti,adc081c
> > +      - ti,adc101c
> > +      - ti,adc121c
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +  vref-supply:
> > +    description:
> > +      Regulator for the combined power supply and voltage reference
> > +
> > +  "#io-channel-cells":
> > +    const: 1
> > +
> > +required:
> > +  - compatible
> > +  - reg  
> 
> Why not requiring io-channel-cells? If it is an IIO ADC provider, you
> need the cells, right?

Only if anyone is using it as a provider.  If it's purely being used via
IIO then there are no consumers registered.

So historically I've left it up to those defining the binding to decide if
they think #io-channel-cells should be required or optional.

It gets a bit non obvious with some of the more complex special ADCs on whether
they will ever be consumed.  This one is generic, so quite likely it will be.

Jonathan

> 
> Best regards,
> Krzysztof
>