linux-kernel - Re: [PATCH v2 1/2] dt-bindings: staging: iio: cdc: ad7746: add binding documentation for AD7746

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Message-ID: <20210420193746.GA3632576@robh.at.kernel.org>
Date:   Tue, 20 Apr 2021 14:37:46 -0500
From:   Rob Herring <robh@...nel.org>
To:     Lucas Stankus <lucas.p.stankus@...il.com>
Cc:     lars@...afoo.de, Michael.Hennerich@...log.com, jic23@...nel.org,
        gregkh@...uxfoundation.org, linux-iio@...r.kernel.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/2] dt-bindings: staging: iio: cdc: ad7746: add
 binding documentation for AD7746

On Sun, Apr 18, 2021 at 07:49:51PM -0300, Lucas Stankus wrote:
> Add device tree binding documentation for AD7746 cdc in YAML format.
> 
> Signed-off-by: Lucas Stankus <lucas.p.stankus@...il.com>
> ---
> 
> A minor note about the adi,excitation-vdd-permille property. Jonathan
> suggested the name to be adi,excitation-vdd-milicent, but I was unsure of
> the milicent naming. With a quick search I found out that the common way to
> call a thousandth is 'per mille'[1], but I didn't find any use of it in the
> kernel documentation. Any thoughts about it?

Seems okay to me.

> [1] https://en.wikipedia.org/wiki/Per_mille
> 
>  .../bindings/iio/cdc/adi,ad7746.yaml          | 73 +++++++++++++++++++
>  1 file changed, 73 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml b/Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml
> new file mode 100644
> index 000000000000..a2a7eee674ba
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/cdc/adi,ad7746.yaml
> @@ -0,0 +1,73 @@
> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/cdc/adi,ad7746.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: AD7746 24-Bit Capacitance-to-Digital Converter with Temperature Sensor
> +
> +maintainers:
> +  - Michael Hennerich <michael.hennerich@...log.com>
> +
> +description: |
> +  AD7746 24-Bit Capacitance-to-Digital Converter with Temperature Sensor
> +
> +  Specifications about the part can be found at:
> +  https://www.analog.com/media/en/technical-documentation/data-sheets/ad7291.pdf
> +
> +properties:
> +  compatible:
> +    enum:
> +      - adi,ad7745
> +      - adi,ad7746
> +      - adi,ad7747
> +
> +  reg:
> +    maxItems: 1
> +
> +  adi,excitation-vdd-permille:
> +    description: |
> +      Set VDD per mille to be used as the excitation voltage.
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    enum: [125, 250, 375, 500]
> +
> +  adi,exca-output-en:
> +    description: Enables the EXCA pin as the excitation output.
> +    type: boolean
> +
> +  adi,exca-output-invert:
> +    description: Inverts the excitation output in the EXCA pin.
> +    type: boolean

'invert' assumes I know what the non-inverted signal is. Sometimes that 
makes sense, but if you can define in terms of the inverse that would be 
better. For example, for a normally active low signal, name the property 
'foo-active-high'.

> +
> +  adi,excb-output-en:
> +    description: Enables the EXCB pin as the excitation output.
> +    type: boolean
> +
> +  adi,excb-output-invert:
> +    description: Inverts the excitation output in the EXCB pin.
> +    type: boolean
> +
> +required:
> +  - compatible
> +  - reg
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    i2c {
> +      #address-cells = <1>;
> +      #size-cells = <0>;
> +
> +      ad7746: cdc@48 {
> +        compatible = "adi,ad7746";
> +        reg = <0x48>;
> +        adi,excitation-vdd-permille = <125>;
> +
> +        adi,exca-output-en;
> +        adi,exca-output-invert;
> +        adi,excb-output-en;
> +        adi,excb-output-invert;
> +      };
> +    };
> +...
> -- 
> 2.31.1
>