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

Oleksij Rempel
2026-01-27T06:09:43Z

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).
+
required:
- compatible
- reg
+ - maxim,rfs-ohms
+
+allOf:
+ - if:
+ properties:
+ compatible:
+ contains:
+ enum:
+ - maxim,ds4402
+ - maxim,ds4422
+ then:
+ properties:
+ maxim,rfs-ohms:
+ minItems: 2
+ maxItems: 2
+ - if:
+ properties:
+ compatible:
+ contains:
+ enum:
+ - maxim,ds4404
+ - maxim,ds4424
+ then:
+ properties:
+ maxim,rfs-ohms:
+ minItems: 4
+ maxItems: 4

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