Re: [RFC] iio: adc: support for multi-device aggregation

[Jonathan Santos]

On 05/08, Andy Shevchenko wrote:
> On Fri, May 08, 2026 at 10:27:54AM +0300, Andy Shevchenko wrote:
> > On Thu, May 07, 2026 at 06:28:58PM -0300, Jonathan Santos wrote:
> > > 
> > > We have a request to support multiple devices tied together in a single evaluation
> > > board. The goal is to be able to read them simultaneously via the IIO framework,
> > > while also controlling them individually. Currently we have two ADC devices that
> > > would benefit from this, but there might be more in the future.
> > 
> > > To summarize, the devices share SPI pins such as SCLK and MOSI, but have individual
> > > chip-selects and MOSIs (we can consider individual SPI interfaces). The ideia
> > > is to allow users to aggregate these devices so they can be read simultaneously
> > > from the user space.
> > 
> > This paragraph contradicts itself. The they share the bus. The bus is serial
> > and can't do at all what you are describing. Try to rephrase, or forget about
> > this, it's simply impossible.
> 
> Ah, this is semi-shared bus... Interesting how the host controller looks like
> for this? It's not a regular SPI.
>

Yes, the only pins they don't share is the SDI and CS. The main
difference in the controller is the multiple SDI lanes, but that is
something we support in the SPI driver. Because of this feature, the 
controller can read all lanes simultaneously and put them in order on the
DMA buffer.

> -- 
> With Best Regards,
> Andy Shevchenko
>