linux-kernel - Re: [PATCH v1 1/2] dt-bindings: iio: adc: adding dt-bindings for PAC193X

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Message-ID: <c38afa67-d24f-0390-f18a-81bee15b7eca@kernel.org>
Date:   Tue, 21 Feb 2023 14:44:00 +0100
From:   Krzysztof Kozlowski <krzk@...nel.org>
To:     marius.cristea@...rochip.com, jic23@...nel.org, lars@...afoo.de,
        robh+dt@...nel.org
Cc:     linux-iio@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v1 1/2] dt-bindings: iio: adc: adding dt-bindings for
 PAC193X

On 20/02/2023 13:32, marius.cristea@...rochip.com wrote:
> From: Marius Cristea <marius.cristea@...rochip.com>

Subject: drop second/last, redundant "dt-bindings for". The
"dt-bindings" prefix is already stating that these are bindings.

> 
> This is the device tree schema for iio driver for
> Microchip PAC193X series of Power Monitors with Accumulator.

Do not use "This commit/patch".
https://elixir.bootlin.com/linux/v5.17.1/source/Documentation/process/submitting-patches.rst#L95

Use imperative - also for subject.

Please use scripts/get_maintainers.pl to get a list of necessary people
and lists to CC.  It might happen, that command when run on an older
kernel, gives you outdated entries.  Therefore please be sure you base
your patches on recent Linux kernel.


> 
> Signed-off-by: Marius Cristea <marius.cristea@...rochip.com>
> ---
>  .../bindings/iio/adc/microchip,pac193x.yaml   | 122 ++++++++++++++++++
>  1 file changed, 122 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/iio/adc/microchip,pac193x.yaml
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/microchip,pac193x.yaml b/Documentation/devicetree/bindings/iio/adc/microchip,pac193x.yaml
> new file mode 100644
> index 000000000000..e4ea560991e9
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/microchip,pac193x.yaml
> @@ -0,0 +1,122 @@
> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> +%YAML 1.2
> +---
> +$id: http://devicetree.org/schemas/iio/adc/microchip,pac193x.yaml#
> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> +
> +title: Microchip PAC193X Power Monitors with Accumulator
> +
> +maintainers:
> +  - Marius Cristea <marius.cristea@...rochip.com>
> +
> +properties:
> +  compatible:
> +    enum:
> +      - microchip,pac1934
> +      - microchip,pac1933
> +      - microchip,pac1932
> +      - microchip,pac1931

Maybe order these numerically (ascending)?

> +
> +  reg:
> +    maxItems: 1
> +
> +  "#address-cells":
> +    const: 1
> +
> +  "#size-cells":
> +    const: 0
> +
> +  microchip,samp-rate:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    description: Sampling rate for all device's channels.

What are the units? rate is usually in hz, which should be expressed in
unit suffix (property name)

> +    enum: [8, 64, 256, 1024]
> +    default: 1024
> +
> +required:

required goes after all properties, so after patternProperties

> +  - compatible
> +  - reg
> +  - microchip,samp-rate
> +  - "#address-cells"
> +  - "#size-cells"
> +
> +patternProperties:
> +  "^channel([1-4])@[1-4]+$":

Why first reg-pattern ([1-4])? For what do you need it?

> +    $ref: "adc.yaml"

Drop quotes

> +    type: object
> +    description: Represents the external channels which are connected to the ADC.
> +
> +    properties:
> +      reg:
> +        description: The channel number.
> +          It can have up to 4 channels, numbered from 1 to 4.
> +        items:
> +          - minimum: 1
> +            maximum: 4
> +
> +      microchip,uohms-shunt-res:

Not a correct unit suffix. Use standard properties:
git grep shunt -- Documentation/devicetree/


> +        $ref: /schemas/types.yaml#/definitions/uint32
> +        description: |
> +          Value in micro Ohms of the shunt resistor connected between
> +          the SENSE+ and SENSE- inputs, across which the current is measured. Value
> +          is needed to compute the scaling of the measured current.
> +
> +      microchip,rail-name:
> +        $ref: /schemas/types.yaml#/definitions/string
> +        description: Name of the monitored power rail.

Why do you need it? Why this is a property of DT? Aren't you now
duplicating label?

> +
> +      microchip,bi-directional:
> +        description: Whether the channel is bi-directional.

Describe here what is a "bi-directional" channel for ADC... Maybe it is
obvious, maybe not. For me it is not and none of other devices have it.

> +        type: boolean
> +
> +    required:
> +      - reg
> +      - microchip,uohms-shunt-res
> +      - microchip,rail-name
> +
> +    additionalProperties: false
> +
> +additionalProperties: false
> +
> +examples:
> +  - |
> +    i2c {
> +        #address-cells = <1>;
> +        #size-cells = <0>;
> +
> +        pac193x: pac193x@10 {

Node names should be generic.
https://devicetree-specification.readthedocs.io/en/latest/chapter2-devicetree-basics.html#generic-names-recommendation

> +            compatible = "microchip,pac1934";
> +            reg = <0x10>;
> +
> +            #address-cells = <1>;
> +            #size-cells = <0>;
> +            microchip,samp-rate = <64>;
> +
> +            channel1@1 {

1@1 is for sure not generic...



Best regards,
Krzysztof