linux-kernel - Re: [PATCH 1/2] dt-bindings: iio: adc: add ad7944 ADCs

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Date: Thu, 15 Feb 2024 07:23:34 -0600
From: Rob Herring <robh@...nel.org>
To: David Lechner <dlechner@...libre.com>
Cc: linux-iio@...r.kernel.org,
	Michael Hennerich <Michael.Hennerich@...log.com>,
	Jonathan Cameron <jic23@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
	Conor Dooley <conor+dt@...nel.org>,
	Nuno Sá <nuno.sa@...log.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/2] dt-bindings: iio: adc: add ad7944 ADCs

On Tue, Feb 06, 2024 at 11:34:13AM -0600, David Lechner wrote:
> On Tue, Feb 6, 2024 at 11:26 AM David Lechner <dlechner@...libre.com> wrote:
> >
> > This adds a new binding for the Analog Devices, Inc. AD7944, AD7985, and
> > AD7986 ADCs.
> >
> > Signed-off-by: David Lechner <dlechner@...libre.com>
> > ---
> >  .../devicetree/bindings/iio/adc/adi,ad7944.yaml    | 231 +++++++++++++++++++++
> >  MAINTAINERS                                        |   8 +
> >  2 files changed, 239 insertions(+)
> >
> > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7944.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7944.yaml
> > new file mode 100644
> > index 000000000000..a023adbeba42
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7944.yaml
> 
> ...
> 
> 
> +  adi,reference:
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum: [ internal, internal-buffer, external ]
> +    default: internal
> 
> ...
> 
> > +allOf:
> > +  # ref-supply is only used for external reference voltage
> > +  - if:
> > +      not:
> > +        required:
> > +          - adi,reference
> > +    then:
> > +      properties:
> > +        ref-supply: false
> > +    else:
> > +      if:
> > +        properties:
> > +          adi,reference:
> > +            const: external
> > +      then:
> > +        required:
> > +          - ref-supply
> > +      else:
> > +        properties:
> > +          ref-supply: false
> 
> This seems like something that could potentially be improved in the
> dtschema tooling. Since adi,reference has a default of "internal", I
> would expect:
> 
>      if:
>        properties:
>          adi,reference:
>            const: external

         required:
           - adi,reference

>      then:
>        required:
>          - ref-supply
>      else:
>        properties:
>          ref-supply: false
> 
> to be sufficient here. However, currently, if the adi,reference
> property is omitted from the dts/dtb, the condition here evaluates to
> true and unexpectedly (incorrectly?) the validator requires the
> ref-supply property.

That's just how json-schema works. With the above, it should work for 
you.

However, redesigning the binding would make things simpler. Just make 
'ref-supply' being present mean external ref. No 'ref-supply' is then 
internal. Then you just need a boolean for 'internal-buffer' mode and:

dependentSchemas:
  ref-supply:
    not:
      required: ['adi,internal-buffer-ref']

Rob