Re: [PATCH 2/3] dt-bindings: iio: dac: add support for MCP48FEB02 SPI

[Conor Dooley <conor@kernel.org>]

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On Thu, Jul 23, 2026 at 01:50:59PM +0000, sashiko-bot@kernel.org wrote:
> Thank you for your contribution! Sashiko AI review found 2 potential issue(s) to consider:
> - [Medium] The schema retains `additionalProperties: false` at the root level while introducing a conditional `$ref` to `spi-peripheral-props.yaml` in the `allOf` block. This breaks schema validation for standard SPI properties.
> - [Low] The newly added SPI device tree example uses an inappropriate SPI chip select value (`0x60`), copied from the I2C device address example.
> --
> 
> --- Patch [2]: [PATCH 2/3] dt-bindings: iio: dac: add support for MCP48FEB02 SPI ---
> commit a357ffde05c7807cd64bca71103d780d8dde416b
> Author: Ariana Lazar <ariana.lazar@microchip.com>
> 
> dt-bindings: iio: dac: add support for MCP48FEB02 SPI
> 
> This commit adds SPI support for the MCP48FxBy1/2/4/8 DAC families to the
> existing MCP47FEB02 device tree binding. It introduces the new compatible
> strings, the spi-max-frequency property, and a devicetree example for SPI.
> 
> > diff --git a/Documentation/devicetree/bindings/iio/dac/microchip,mcp47feb02.yaml b/Documentation/devicetree/bindings/iio/dac/microchip,mcp47feb02.yaml
> > index d131f136bd151..d25c763241a4f 100644
> > --- a/Documentation/devicetree/bindings/iio/dac/microchip,mcp47feb02.yaml
> > +++ b/Documentation/devicetree/bindings/iio/dac/microchip,mcp47feb02.yaml
> > @@ -178,6 +239,13 @@ required:
> >    - vdd-supply
> >  
> >  allOf:
> > +  - if:
> > +      properties:
> > +        compatible:
> > +          contains:
> > +            pattern: "^microchip,mcp48f[ev]b[0-2][1248]$"
> > +    then:
> > +      $ref: /schemas/spi/spi-peripheral-props.yaml#
> 
> [ ... ]
> 
> > +    then:
> > +      properties:
> > +        spi-max-frequency: false
> > +
> >  additionalProperties: false
> 
> [Severity: Medium]
> Since this schema now includes a conditional $ref to spi-peripheral-props.yaml
> in the allOf block, should this be changed to unevaluatedProperties: false?
> 
> JSON Schema limits additionalProperties: false to only evaluating properties
> explicitly declared in the root properties or patternProperties. Any standard
> SPI properties pulled in via the conditional $ref will be incorrectly rejected
> by dt_binding_check.

This trips up Sashiko a lot.
This additionalProperties is fine if spi-max-frequency is the only
property from that binding that this device uses.

> 
> >  examples:
> > @@ -299,4 +424,29 @@ examples:
> >              };
> >          };
> >      };
> > +  - |
> > +    spi {
> > +        #address-cells = <1>;
> > +        #size-cells = <0>;
> > +
> > +        dac@60 {
> > +          compatible = "microchip,mcp48feb02";
> > +          reg = <0x60>;
> 
> [Severity: Low]
> Is 0x60 intended to be used as an SPI chip select here, or was this copied
> from the I2C example?
> 
> Typically, an SPI chip select would be 0 or 1, and the node would be named
> dac@0 with reg = <0>.

It's an example, so it doesn't matter. But yes, looks like a copy-paste
mistake.

> 
> > +          vdd-supply = <&vdac_vdd>;
> > +          vref-supply = <&vref_reg>;
> > +          spi-max-frequency = <10000000>;
> > +
> > +          #address-cells = <1>;
> > +          #size-cells = <0>;
> > +          channel@0 {
> > +            reg = <0>;
> > +            label = "Adjustable_voltage_ch0";
> > +          };
> > +
> > +          channel@1 {
> > +            reg = <0x1>;
> > +            label = "Adjustable_voltage_ch1";
> > +          };
> > +        };
> > +    };
> >  ...
> 
> -- 
> Sashiko AI review · https://sashiko.dev/#/patchset/20260723-mcp47feb02_refactor-v1-0-ee59e63672bc@microchip.com?part=2

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