Re: [PATCH 2/2] iio: adc: ad9467: make iio backend optional

["Nuno Sá" <noname.nuno@gmail.com>]

On Sun, 2026-01-11 at 11:41 +0000, Jonathan Cameron wrote:
> On Mon, 05 Jan 2026 14:57:02 +0000
> Nuno Sá <noname.nuno@gmail.com> wrote:
> 
> > On Mon, 2026-01-05 at 13:06 +0200, Tomas Melin wrote:
> > > Hi,
> > > 
> > > On 21/12/2025 22:00, Jonathan Cameron wrote:  
> > > > On Tue, 16 Dec 2025 11:40:06 +0000
> > > > Tomas Melin <tomas.melin@vaisala.com> wrote:
> > > >   
> > > > > Not all users can or want to use the device with an iio-backend.
> > > > > For these users, let the driver work in standalone mode, not coupled
> > > > > to the backend or the services it provides.
> > > > > 
> > > > > Signed-off-by: Tomas Melin <tomas.melin@vaisala.com>  
> > > > Hi Tomas,
> > > >   
> > > > >  static int ad9467_probe(struct spi_device *spi)
> > > > > @@ -1352,21 +1361,25 @@ static int ad9467_probe(struct spi_device *spi)
> > > > >  	indio_dev->channels = st->info->channels;
> > > > >  	indio_dev->num_channels = st->info->num_channels;
> > > > >  
> > > > > +	/* Using a backend is optional */  
> > > > 
> > > > I'll largely defer to Nuno on the backend aspects but I would like a
> > > > lot more than a statement that it is optional in this comment.
> > > > At least something about where the data goes and what a real system
> > > > that didn't provide a backend would look like etc.  
> > > 
> > > Having the backend as optional is about flexibility to incorporate these
> > > devices as fits best with the system. The current backend approach is
> > > pretty much dictated with how the ADI default backend is implemented.
> > > These devices are fully configurable via SPI interface so the backend
> > > doesn't necessarily need to be anything fancy or even configurable.
> > > 
> > > So there is atleast two use cases that promote the optional iio-backend
> > > approach
> > >  - simple backend that is not configurable, no need for a dedicated
> > > driver. The backend (FPGA) sits and waits for data and handles it when
> > > it arrives  
> > 
> > Agree on the above. Ideally we could have some dummy backend for the above but
> > it is not really easy/maintainable to have it.
> 
> When we say the backend needs no driver, where does the data end up?
> Is the idea that it goes into some processing pipeline and sent to
> some external path that we have no visibility of? i.e. We configure the
> data capture in Linux but never see the data?

Yes, that's also my assumption about Tomas's usecase.

- Nuno Sá