Re: [PATCH v4 1/4] dt-bindings: iio: adc: Add ltc2378

[sashiko-bot@kernel.org]

Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider:
- [Medium] The compatible string 'adi,ltc2338-18' incorrectly specifies 'adi,ltc2376-18' as a fallback despite conflicting hardware constraints for 'ref-supply', breaking backward compatibility.
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commit aa175408226610e4bc2c27ed8ee768b0307ee6fa
Author: Marcelo Schmitt <marcelo.schmitt@analog.com>

dt-bindings: iio: adc: Add ltc2378

This commit documents the device tree bindings for the Analog Devices LTC2378
and similar series of ADCs. It specifies the compatible strings, required
properties, and voltage reference constraints.

> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml
> new file mode 100644
> index 0000000000000..9adc420fe142b
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ltc2378.yaml
[ ... ]
> +      # Low sample rate fallback for 18-bit bipolar sensors.
> +      - items:
> +          - enum:
> +              - adi,ltc2379-18 # 1.6 MSPS
> +              - adi,ltc2338-18 # 1 MSPS
> +              - adi,ltc2378-18 # 1 MSPS
> +              - adi,ltc2377-18 # 500 kSPS
> +          - const: adi,ltc2376-18 # fallback (250 kSPS)
[ ... ]
> +allOf:
> +  # Except for LTC2338, all designs require a voltage reference input
> +  - if:
> +      properties:
> +        compatible:
> +          not:
> +            contains:
> +              enum:
> +                - adi,ltc2338-18
> +    then:
> +      required:
> +        - ref-supply
> +      properties:
> +        refin-supply: false
> +    else:
> +      properties:
> +        ref-supply: false

[Severity: Medium]
Will this cause probe failures on older kernels when using the fallback?

The compatible string adi,ltc2338-18 is configured to use adi,ltc2376-18 as a
fallback. However, this conditional block strictly forbids the ref-supply
property for adi,ltc2338-18.

Because adi,ltc2376-18 requires a ref-supply, a device tree correctly following
this binding for adi,ltc2338-18 will lack that property.

When an older kernel attempts to bind using the adi,ltc2376-18 fallback string,
will it fail to find the expected ref-supply regulator and abort probing?

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Sashiko AI review · https://sashiko.dev/#/patchset/cover.1782397418.git.marcelo.schmitt@analog.com?part=1