Re: [PATCH v7 1/7] spi: dt-bindings: Add spi-device-addr peripheral property

["Nuno Sá" <noname.nuno@gmail.com>]

On Tue, Jul 28, 2026 at 05:10:55PM +0100, Conor Dooley wrote:
> On Sat, Jul 25, 2026 at 11:04:45PM +0100, Jonathan Cameron wrote:
> > On Sat, 25 Jul 2026 15:55:01 -0500
> > David Lechner <dlechner@baylibre.com> wrote:
> > 
> > > On 7/22/26 2:54 AM, Janani Sunil wrote:
> > > > Some SPI devices support sharing a single chip select across multiple
> > > > physical chips by encoding a device address in the SPI frame itself.
> > > > Add the generic spi-device-addr property for describing these hardware
> > > > addresses. The property is placed on the SPI peripheral node and may
> > > > contain multiple addresses.
> > > > 
> > > > Signed-off-by: Janani Sunil <janani.sunil@analog.com>
> > > > ---
> > > >  Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml | 7 +++++++
> > > >  1 file changed, 7 insertions(+)
> > > > 
> > > > diff --git a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
> > > > index 880a9f624566..b59d047cf117 100644
> > > > --- a/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
> > > > +++ b/Documentation/devicetree/bindings/spi/spi-peripheral-props.yaml
> > > > @@ -142,6 +142,13 @@ properties:
> > > >      minItems: 2
> > > >      maxItems: 4
> > > >  
> > > > +  spi-device-addr:
> > > > +    $ref: /schemas/types.yaml#/definitions/uint32-array
> > > > +    description:
> > > > +      Device addresses used when multiple peripherals share a single chip
> > > > +      select. The array allows one logical peripheral to comprise multiple
> > > > +      physical devices, with one address per device.  
> > > 
> > > "per physical device" for clarity.
> > > 
> > 
> > We may end up relaxing that again if multichip packages start doing this.
> > Fine to add that clarification for now. We can revisit when / if it ever
> > needs that relaxing.
> > 
> > > > +
> > > >    st,spi-midi-ns:
> > > >      deprecated: true
> > > >      description: |
> > > >   
> > > 
> > > If there is nothing useful the SPI core code can do with this information,
> > > I'm not entirely convinced that this needs to be a common property.
> > 
> > I think being common does make some sense from a standarization point of
> > view and it isn't obvious where to put it other than under spi.
> > 
> > > 
> > > And this only allows for one logical device. If we wanted to treat each
> > > address as a logical device (all with same CS), we would need #address-cells = <2>;
> > > instead where the DT "address" is two values, the CS and the device address.
> > 
> > Ah.  Good point for the adc@address or similar needing to match a combination
> > of CS and spi-device-addr.  Conor any thoughts on how this would be done?
> 
> I'm sorry, I don't quite understand. Why do you want to support both of
> these representations? Hardware wise both of these things would be
> describing the same setup, so allowing this alternate "multiple logical
> device" typically is not permitted. What even is the use case of it?
> Does it matter at all if you have one or more logical devices from a
> consumer perspective?
> 
> I do have an idea of how to solve the adc@address problem (you can do
> adc@address,spi-device-address like some other devices) but as I said I
> don't get why it would be needed.

IIUC, I think for the current ADI device it could actually be useful to have
the above representation given that, in theory, any of the logical
devices can have their own supplies, pins, etc (so it would help to have
each of them as adc@address,spi-device-address)... But we choose not to go
down that path (in previous versions) for simplicity. So yeah, not sure
:).

- Nuno Sá

> 
> > 
> > 
> > Also feels like this series should update the one use of the microchip binding
> > in tree.
> > 
> > arch/riscv/boot/dts/microchip/mpfs-beaglev-fire.dts
> 
> I never asked for this cos I maintain the platform and was gonna fix it
> up myself, but sure!