Re: [PATCH v4 1/2] dt-bindings: adc: add AD7173

From: Conor Dooley <conor@kernel.org>
To: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: mitrutzceclan <mitrutzceclan@gmail.com>,
	linus.walleij@linaro.org, brgl@bgdev.pl, andy@kernel.org,
	linux-gpio@vger.kernel.org,
	"Lars-Peter Clausen" <lars@metafoo.de>,
	"Jonathan Cameron" <jic23@kernel.org>,
	"Rob Herring" <robh+dt@kernel.org>,
	"Krzysztof Kozlowski" <krzysztof.kozlowski+dt@linaro.org>,
	"Conor Dooley" <conor+dt@kernel.org>,
	"Michael Walle" <michael@walle.cc>,
	"Andy Shevchenko" <andy.shevchenko@gmail.com>,
	"Arnd Bergmann" <arnd@arndb.de>,
	"ChiaEn Wu" <chiaen_wu@richtek.com>,
	"Niklas Schnelle" <schnelle@linux.ibm.com>,
	"Leonard Göhrs" <l.goehrs@pengutronix.de>,
	"Mike Looijmans" <mike.looijmans@topic.nl>,
	"Haibo Chen" <haibo.chen@nxp.com>,
	"Hugo Villeneuve" <hvilleneuve@dimonoff.com>,
	"Ceclan Dumitru" <dumitru.ceclan@analog.com>,
	linux-iio@vger.kernel.org, devicetree@vger.kernel.org,
	linux-kernel@vger.kernel.org,
	"Conor Dooley" <conor.dooley@microchip.com>
Subject: Re: [PATCH v4 1/2] dt-bindings: adc: add AD7173
Date: Thu, 16 Nov 2023 17:54:13 +0000	[thread overview]
Message-ID: <20231116-spousal-mystify-dcd1d4fec7e6@squawk> (raw)
In-Reply-To: <44cfcd9a-f139-479b-85ff-5fd23c9714b2@linaro.org>

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On Thu, Nov 16, 2023 at 03:54:13PM +0100, Krzysztof Kozlowski wrote:
> On 16/11/2023 14:46, mitrutzceclan wrote:
> > From: Dumitru Ceclan <mitrutzceclan@gmail.com>
> > 
> > The AD7173 family offer a complete integrated Sigma-Delta ADC solution
> > which can be used in high precision, low noise single channel applications
> > or higher speed multiplexed applications. The Sigma-Delta ADC is intended
> > primarily for measurement of signals close to DC but also delivers
> > outstanding performance with input bandwidths out to ~10kHz.
> > 
> > Reviewed-by: Conor Dooley <conor.dooley@microchip.com> # except reference_select
> 
> Please drop the tag. You clearly did not test it, so it must be
> re-reviewed. Do not send code which was not tested.

yeah, this is vastly different from what I reviewed. I suppose if
someone finds it necessary to add a "# except foo" to the end of a tag
it is very good signifier that the tag should in fact be removed.

> 
> > Signed-off-by: Dumitru Ceclan <mitrutzceclan@gmail.com>
> > ---
> > V3 -> V4
> >  - include supply attributes
> >  - add channel attribute for selecting conversion reference
> > 
> >  .../bindings/iio/adc/adi,ad7173.yaml          | 166 ++++++++++++++++++
> >  1 file changed, 166 insertions(+)
> >  create mode 100644 Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml
> > 
> > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml
> > new file mode 100644
> > index 000000000000..92aa352b6653
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad7173.yaml
> > @@ -0,0 +1,166 @@
> > +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> > +# Copyright 2023 Analog Devices Inc.
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/iio/adc/adi,ad7173.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Analog Devices AD7173 ADC device driver
> 
> Drop: device driver
> 
> Bindings are for hardware.
> 
> > +
> > +maintainers:
> > +  - Ceclan Dumitru <dumitru.ceclan@analog.com>
> > +
> > +description: |
> > +  Bindings for the Analog Devices AD717X ADC's. Datasheets for supported chips:
> > +    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7172-2.pdf
> > +    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7173-8.pdf
> > +    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7175-2.pdf
> > +    https://www.analog.com/media/en/technical-documentation/data-sheets/AD7176-2.pdf
> > +
> > +properties:
> > +  compatible:
> > +    enum:
> > +      - adi,ad7172-2
> > +      - adi,ad7173-8
> > +      - adi,ad7175-2
> > +      - adi,ad7176-2
> > +
> > +  reg:
> > +    maxItems: 1
> > +
> > +  interrupts:
> > +    maxItems: 1
> > +
> > +  '#address-cells':
> > +    const: 1
> > +
> > +  '#size-cells':
> > +    const: 0
> > +
> > +  spi-max-frequency:
> > +    maximum: 20000000
> > +
> > +  refin-supply:
> > +    description: external reference supply, can be used as reference for conversion.
> > +
> > +  refin2-supply:
> > +    description: external reference supply, can be used as reference for conversion.
> > +
> > +  avdd-supply:
> > +    description: avdd supply, can be used as reference for conversion.
> > +
> > +  dependencies:
> 
> Nope, needs testing... See also example-schema.
> 
> 
> > +    refin2-supply:
> > +      properties:
> > +        compatible:
> > +          adi,ad7173-8
> > +
> > +  required:
> 
> Please open example schema and put it in similar place.
> 
> > +    - compatible
> > +    - reg
> > +    - interrupts
> > +
> > +patternProperties:
> > +  "^channel@[0-9a-f]$":
> > +    type: object
> > +    $ref: adc.yaml
> > +    unevaluatedProperties: false
> > +
> > +    properties:
> > +      reg:
> > +        minimum: 0
> > +        maximum: 15
> > +
> > +      diff-channels:
> > +        items:
> > +          minimum: 0
> > +          maximum: 31
> > +
> > +      adi,reference-select:
> > +        description: |
> > +          Select the reference source to use when converting on
> > +          the specific channel. Valid values are:
> > +          0: REFIN(+)/REFIN(−).
> > +          1: REFIN2(+)/REFIN2(−)
> > +          2: REFOUT/AVSS (Internal reference)
> > +          3: AVDD
> > +
> > +          External reference 2 only available on ad7173-8.
> > +          If not specified, internal reference used.
> > +        $ref: /schemas/types.yaml#/definitions/uint32
> > +        enum: [0, 1, 2, 3]
> > +        default: 2

I really don't like these properties where integers are mapped to
functionalities like this. I'd much rather see a enum of strings where
the meaning for these things can be put in & there's no need to look up
the binding to figure out what "adi,reference-select = <3>" means.
For example having "refin", "refin2", "refout-avss" & "avdd" as the
options and therefore "adi,reference-select = "avdd" in a devicetree is
a lot more understandable IMO.

Cheers,
Conor.

> > +
> > +      bipolar:
> > +        type: boolean
> > +
> > +    required:
> > +      - reg
> > +      - diff-channels
> > +
> > +allOf:
> > +  - $ref: /schemas/spi/spi-peripheral-props.yaml#
> > +
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            const: adi,ad7173-8
> > +    then:
> 
> ??? Maybe you want to use "not"?
> 
> > +    else:
> 
> > +      patternProperties:
> > +        "^channel@[0-9a-f]$":
> > +          properties:
> > +            enum: [0, 2, 3]
> > +
> > +unevaluatedProperties: false
> > +
> 
> Best regards,
> Krzysztof
> 

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