Re: [PATCH v2 09/15] dt-bindings: iio: adc: adi,ad4134: Document SPI connection mode

[Marcelo Schmitt <marcelo.schmitt1@gmail.com>]

On 09/17, Rob Herring wrote:
> On Thu, Sep 17, 2026 at 04:30:39AM +0100, Jonathan Cameron wrote:
> > On Wed, 16 Sep 2026 11:00:25 -0500
> > Rob Herring <robh@kernel.org> wrote:
> > 
> > > On Tue, Sep 15, 2026 at 04:14:44PM -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>
> > > > ---
> > > > Change log v1 -> v2:
> > > > - Set default for adi,spi-mode property.
> > > > - Added '#daisy-chained-devices' property.
> > > > - Documented constraints for adi,spi-mode + #daisy-chained-devices combinations.
> > > > 
> > > >  .../bindings/iio/adc/adi,ad4134.yaml          | 51 ++++++++++++++++---
> > > >  1 file changed, 44 insertions(+), 7 deletions(-)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
> > > > index ea6d7e026419..012e09decf7a 100644
> > > > --- a/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
> > > > +++ b/Documentation/devicetree/bindings/iio/adc/adi,ad4134.yaml
> > > > @@ -131,6 +131,26 @@ 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 ]
> > > > +    default: no-cs
> > > > +    description: |
> > > > +      This property indicates the SPI wiring configuration.
> > > > +      * 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.  
> > > 
> > > Absence of this property should be conventional mode.
> > Hi Rob,
> > 
> > Unfortunately we missed this in the binding originally so we are left with the default
> > of what the driver did at the time.
> > 
> > I wouldn't be against merging a change in that default as a fix though if we
> > don't think this is yet in heavy use (merged in 7.0, but given not a complete
> > feature set yet, maybe?)
> 
I don't believe this part is being extensively used. Going with the conventional
4-wire default is the more natural choice so I'm growing my TODO list with a
note for a follow up patch to update this default.

> Ok, it's fine then. Just make sure the commit msg has this detail.

Ok, will add.


Thanks,
Marcelo