Re: [PATCH v3 1/6] dt-bindings: iio: adc: ad7768-1: Document multidevice support

["Nuno Sá" <nuno.sa@analog.com>]

On Tue, Aug 18, 2026 at 10:02:50AM -0500, David Lechner wrote:
> On 8/17/26 6:32 PM, Jonathan Santos wrote:
> > The AD7768-1 family supports aggregating up to four devices on a single
> > SPI controller, with each device occupying a dedicated CS line and a
> > single data lane.
> > 
> > Extend the `reg` property to accept up to 4 entries (one per device).
> > 
> > Add `spi-rx-bus-width` property to declare the per-device lane count.
> > Since each lane is bound to one CS, the number of entries must match
> > `reg`. Make it required when `reg` has more than one entry.
> > 
> I don't see why we should have to require the spi-rx-bus-width property.
> It seems logical that if it is not present, then we would assume one
> lane per CS. This is already how bindings work.
> 
> For example, adi,ad4080 and ge,achc have multiple CS lines and don't
> require any bus width properties.

Hmm that's my default then! I was the one requesting it. Basically
because of:

https://elixir.bootlin.com/linux/v7.2/source/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml#L76

So I thought that $refing spi-peripheral-props.yaml and leaving the
default value would make dtbs_check to fail if one used 

spi-rx-bus-width = <1>, <1>, <1>, <1>;

in DT. 

Won't it fail?

And if we don't give the property I believe we'll have:

https://elixir.bootlin.com/linux/v7.2/source/drivers/spi/spi.c#L2509

And given these series assumption of spi->num_rx_lanes == number of
devices (which I don't agree btw), I thought we would need to make
spi-rx-bus-width  explicit in our bindings! I still think but I might be
wrong and I'm by no means an expert on dt bindings schemas work :)

- Nuno Sá

>