Re: [PATCH v3 1/2] dt-bindings: iio: dac: Add AD5529R

[Nuno Sá]

On Fri, Jun 19, 2026 at 12:33:11PM +0200, Janani Sunil wrote:
> 
> On 6/14/26 21:44, Jonathan Cameron wrote:
> > On Tue, 9 Jun 2026 16:47:23 +0200
> > Janani Sunil <jan.sun97@xxxxxxxxx> wrote:
> > 
> 
> Hi Jonathan, Rob, Krzysztof, Conor,
> 
> One possible model that would also allow mixing the 12-bit and 16-bit variants would be to treat the parent node
> as the shared SPI transport only, and let each dac@N child carry its own compatible.
> 
> Rob, Krzysztof, Conor — wanted to get your input on whether this is an acceptable binding pattern.
> 
> properties:
>   compatible:
>     const: adi,ad5529r-bus
> 
> patternProperties:
>   "^dac@[0-3]$":
>     type: object
>     properties:
>       compatible:
>         enum:
>           - adi,ad5529r-16
>           - adi,ad5529r-12
>       reg:
>         minimum: 0
>         maximum: 3
> 
> With a DT example such as:
> 
> ad5529r@0 {
>         compatible = "adi,ad5529r-bus";
>         reg = <0>;
> 
>         dac@0 {
>                 compatible = "adi,ad5529r-16";
>                 reg = <0>;
>         };
> 
>         dac@1 {
>                 compatible = "adi,ad5529r-12";
>                 reg = <1>;
>         };
> };
> 
> The downside is that it introduces adi,ad5529r-bus as a compatible that does not correspond to an actual
> standalone device variant - it would require a parent driver to manage the shared SPI transport and enumerate the
> child devices. The actual DAC functionality is handled by the matching per-child compatibles(12 or 16 bit).
> Is this an acceptable pattern, or is there a preferred way to model this type of addressing scheme?
> 

At some point, I wondered if we can't just have this at spi level? Like
(in the simplest terms) a new spi-peripheral property that would allow
devices to share the same CS. Then we would need an adi,pin-id kind of
property for this device but the bindings would be pretty much as if we
only supported one device.

I see Mark is already in the loop, maybe he has seen this kind of things
before.

- Nuno Sá