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

Rob Herring
2021-04-20T19:37:51Z

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@gmail.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@analog.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
>