Re: [PATCH v7 2/7] dt-bindings: iio: adc: microchip,mcp3564: Add spi-device-addr

[David Lechner <dlechner@baylibre.com>]

On 7/29/26 3:47 PM, Conor Dooley wrote:

...

> Only going to reply to this for now, I'll reply to the other thread of
> this conversation later so as not to end up duplicating discussion, but
> I am thinking of things like what if someone puts a mcp3654r and an
> ad5529r on the same chip select? I think that's actually perfectly
> functional on a hardware level, provided the fuses/pins are set up
I'm not sure this works in general since SPI devices aren't going to
have a standard way to specify the address.

For example, ad5529r has the address at bits [14:12] in a 16-bit
"instruction phase" while mcp3654r has the address at [7:6] in the
"command byte".

An ad5529r instruction could inadvertently be interpreted as a
command by mcp3654r. So I don't think they could exist on the
same CS.

> correctly (and if it is not, mixing the microchip devices is possible
> and probably mixing future ADI ones will be too).
> 

Yes, I suppose this could be possible, but I don't think they would
be considered a single logical device in that case. So would be
covered by the device@cs,spi-addr binding that we already discussed.

Example:

adc@0,0 {
    compatible = "adi,adc1";
    ...
};

adc@0,1 {
    compatible = "adi,adc2";
    ...
};