Re: [PATCH v2 2/8] dt-bindings: iio: adc: Add excitation current sources properties

[Jonathan Cameron]

On Thu, 25 Jun 2026 16:55:04 -0500
David Lechner <dlechner@xxxxxxxxxxxx> wrote:

> From: Kurt Borja <kuurtb@xxxxxxxxx>
> 
> Some ADCs incorporate current sources that provide excitation current to
> resistive temperature devices (RTDs), thermistors, diodes and other
> resistive sensors that require constant current biasing.
> 
> Signed-off-by: Kurt Borja <kuurtb@xxxxxxxxx>
> Signed-off-by: David Lechner (TI) <dlechner@xxxxxxxxxxxx>
> ---
> v2 changes (compared to Kurt's RFC v2):
> * Make units nanoamps instead of microamps to fit known devices.
> * Drop bit about allowing single value for multiple channels.
> * Add bit about semantics of the array index.
> ---
>  Documentation/devicetree/bindings/iio/adc/adc.yaml | 20 ++++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adc.yaml b/Documentation/devicetree/bindings/iio/adc/adc.yaml
> index 12800737d4fb..860601ec5334 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adc.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adc.yaml
> @@ -81,6 +81,26 @@ properties:
>        ADCs usually allow choosing between internal reference sources or a pair
>        of external pins.
>  
> +  excitation-channels:

How would this apply if a device provided excitation on pins that didn't correspond
to channels? i.e. some extra ones.  Perhaps such a device that also supports
configuration (rather than a static set up) would just need a different binding.
Feels like I'm creating a corner case we may never see :)

> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +    description:
> +      Excitation current sources provide current to resistive temperature
> +      devices (RTDs), thermistors, diodes and other resistive sensors that
> +      require constant current biasing.
> +
> +      This array describes the mux configuration of the excitation current
> +      sources.
> +
> +  excitation-current-nanoamp:
> +    description:
> +      Excitation current sources provide current to resistive temperature
> +      devices (RTDs), thermistors, diodes and other resistive sensors that
> +      require constant current biasing.
> +
> +      This array describes the current configuration of the excitation current
> +      sources. The index in the array corresponds to the same index in the
> +      excitation-channels array.
> +
>  anyOf:
>    - oneOf:
>        - required:
>