linux-kernel - Re: [PATCH v1 2/8] dt-bindings: iio: dac: maxim,ds4424: add maxim,rfs-ohms property

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Message-ID: <20260119-turbine-feminize-9dcd5c86feec@spud>
Date: Mon, 19 Jan 2026 18:27:52 +0000
From: Conor Dooley <conor@...nel.org>
To: Oleksij Rempel <o.rempel@...gutronix.de>
Cc: Jonathan Cameron <jic23@...nel.org>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzk+dt@...nel.org>,
	Conor Dooley <conor+dt@...nel.org>, kernel@...gutronix.de,
	linux-kernel@...r.kernel.org, linux-iio@...r.kernel.org,
	devicetree@...r.kernel.org, Andy Shevchenko <andy@...nel.org>,
	David Lechner <dlechner@...libre.com>,
	Nuno Sá <nuno.sa@...log.com>,
	David Jander <david@...tonic.nl>
Subject: Re: [PATCH v1 2/8] dt-bindings: iio: dac: maxim,ds4424: add
 maxim,rfs-ohms property

On Mon, Jan 19, 2026 at 07:24:18PM +0100, Oleksij Rempel wrote:
> Introduce the 'maxim,rfs-ohms' property. The full-scale output current
> of these DACs is determined by external resistors (Rfs) connected to
> the FS pins. The driver requires the physical resistance values to
> calculate the correct current scale (Amps per step) for the IIO
> subsystem.
> 
> Keep it optional to avoid forcing updates of existing DTs; without it
> the driver cannot derive a correct IIO scale.

I don't really follow the logic here, if the driver doesn't work
properly without it, shouldn't it be a required property even if that
means existing devicetrees get new warnings? Warnings are preferable to
the drivers malfunctioning on those devices, after all!

> 
> Signed-off-by: Oleksij Rempel <o.rempel@...gutronix.de>
> ---
>  .../devicetree/bindings/iio/dac/maxim,ds4424.yaml     | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml b/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml
> index efe63e6cb55d..b7af8464a4fc 100644
> --- a/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml
> +++ b/Documentation/devicetree/bindings/iio/dac/maxim,ds4424.yaml
> @@ -27,6 +27,17 @@ 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).
> +    minItems: 2
> +    maxItems: 4
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +
>  required:
>    - compatible
>    - reg
> -- 
> 2.47.3
> 

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