Re: [PATCH v2 2/8] dt-bindings: iio: dac: maxim,ds4424: add maxim,rfs-ohms property

Conor Dooley
2026-01-27T19:49:25Z

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On Tue, Jan 27, 2026 at 07:09:33AM +0100, Oleksij Rempel wrote:
> The Maxim DS4422/DS4424 and DS4402/DS4404 current DACs determine their
> full-scale output current via external resistors (Rfs) connected to the
> FSx pins. Without knowing these values, the full-scale range of the
> hardware is undefined.
>
> Add the 'maxim,rfs-ohms' property to describe these physical components.
> This property is required to provide a complete description of the
> hardware configuration.
>
> Signed-off-by: Oleksij Rempel <o.rempel@pengutronix.de>
> ---
> changes v2:
> - make maxim,rfs-ohms a required property as the hardware range is undefined
> without external resistors.
> - add allOf constraints to enforce 2 vs 4 items in maxim,rfs-ohms based on
> compatible string.
> - drop explicit $ref for maxim,rfs-ohms to fix dt_binding_check warning.
> - update example in binding to include the new required property.
> ---
> .../bindings/iio/dac/maxim,ds4424.yaml | 36 +++++++++++++++++++
> 1 file changed, 36 insertions(+)
>
> diff --git a/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml b/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml
> index efe63e6cb55d..400afd8771aa 100644
> --- a/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml
> +++ b/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml
> @@ -27,9 +27,44 @@ properties:
>
> vcc-supply: true
>
> + maxim,rfs-ohms:
> + description: |
> + Array of resistance values in Ohms for the external Rfs resistors
> + connected to the FS pins.
> + - For DS44x2 (2 channels): 2 values required.
> + - For DS44x4 (4 channels): 4 values required.
> + Typical values range from 40000 (40 kOhm) to 160000 (160 kOhm).

Add here
maxItems: 4
minItems: 2

Are 40kOhm and 160kOhm actual max/min values, or just a suggested range?

> +
> required:
> - compatible
> - reg
> + - maxim,rfs-ohms
> +
> +allOf:
> + - if:
> + properties:
> + compatible:
> + contains:
> + enum:
> + - maxim,ds4402
> + - maxim,ds4422
> + then:
> + properties:
> + maxim,rfs-ohms:

> + minItems: 2

Remove this...

> + maxItems: 2
> + - if:
> + properties:
> + compatible:
> + contains:
> + enum:
> + - maxim,ds4404
> + - maxim,ds4424
> + then:
> + properties:
> + maxim,rfs-ohms:
> + minItems: 4

> + maxItems: 4

...and this. The outer-most constraints should be in the definition and
the if/else bit just adjusts whichever bounds it needs to.

Cheers,
Conor.

pw-bot: changes-requested

>
> additionalProperties: false
>
> @@ -43,6 +78,7 @@ examples:
> compatible = "maxim,ds4424";
> reg = <0x10>; /* When A0, A1 pins are ground */
> vcc-supply = <&vcc_3v3>;
> + maxim,rfs-ohms = <5100>, <5100>, <5100>, <5100>;
> };
> };
> ...
> --
> 2.47.3
>

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