Re: [PATCH v1 08/13] dt-bindings: iio: adc: adi,ad4134: Document SPI connection mode

[Conor Dooley <conor@kernel.org>]

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On Wed, Sep 02, 2026 at 02:24:02PM -0300, Marcelo Schmitt wrote:
> Document how AD4134 chips are connected to the host SPI controller
> according to different wiring configurations.
> 
> Signed-off-by: Marcelo Schmitt <marcelo.schmitt@analog.com>
> ---
>  .../bindings/iio/adc/adi,ad4134.yaml          | 22 +++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
> index ea6d7e026419..d843c02a394a 100644
> --- a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
> +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
> @@ -131,6 +131,28 @@ properties:
>      enum: [ free-running, gated ]
>      default: gated
>  
> +  adi,spi-mode:
> +    $ref: /schemas/types.yaml#/definitions/string
> +    enum: [ no-cs, 4-wire, one-channel-chain, two-channel-chain ]
> +    description: |
> +      This property indicates the SPI wiring configuration.
> +
> +      When this property is omitted, it is assumed that the device is using
> +      'no-cs' wiring. When this property is present, it indicates that the
> +      device is using one of the following wiring configurations:

"default: no-cs" and drop the text about the default, but there's some
pretty interesting comments from Sashiko about #daisy-chained-devices
(used for ad7944), although I'm not sure how that'd work for the
two-channel-chain case.

I'd also really appreciate a dts example for a system
with one-channel-chain or two-channel-chain looks, given the second
device may require different supplies etc. I have no impression in my
head of how the dt would be constructed, so I'd like to see wht you have
in mind.

> +
> +      * no-cs: The datasheet calls this "minimum I/O mode". In this mode, the CS
> +        line is not used (tied to GND).
> +      * 4-wire: Specifies a conventional SPI wiring configuration.
> +      * one-channel-chain: In this mode, the DOUT0 line of one chip is connected
> +        to DOUT2 of the next chip upstream in the chain. Only the data interface
> +        of the upmost device in the stream is in direct connection with the
> +        digital host.
> +      * two-channel-chain: In this mode, the DOUT0 and DOUT1 lines of one chip
> +        are respectively connected to DOUT2 and DOUT3 of the next chip upstream
> +        in the chain. Only the data interface of the upmost device in the stream
> +        is in direct connection with the digital host.
> +
>  required:
>    - compatible
>    - reg
> -- 
> 2.53.0
> 

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