Re: [PATCH v2 0/8] iio: add new backend framework

["Nuno Sá" <noname.nuno@gmail.com>]

On Fri, 2023-12-08 at 15:30 +0000, Conor Dooley wrote:
> On Fri, Dec 08, 2023 at 04:14:07PM +0100, Nuno Sa via B4 Relay wrote:
> > This series depends on [1] and it only build on top of it. The point is
> > to already speed up the reviewing of the framework. That obviously means
> > that all those pacthes were dropped in v2.
> > 
> > v1:
> >  
> > https://lore.kernel.org/linux-iio/20231204144925.4fe9922f@jic23-huawei/T/#m222f517
> > 5273b81dbfe40b7f0daffcdc67d6cb8ff
> > 
> > Changes in v2:
> >  - Patch 1-2 and 5
> >    * new patches.
> >  - Patch 6:
> >    * Fixed some docs failures;
> >    * Fixed a legacy 'conv' name in one of the function parameters;
> >    * Added .request_buffer() and .free_buffer() ops;
> >    * Refactored the helper macros;
> >    * Added Olivier as Reviewer.
> >  - Patch 7:
> >    * Use new devm_iio_backend_request_buffer().
> >  - Patch 8:
> >    * Implement new .request_buffer() and .free_buffer() ops;
> > 
> > Also would like to mention that in v2 I'm experimenting in having the
> > DMA on the backend device (as discussed with David in v1). Does not look
> > to bad but as I said before, I'm not seeing a big issue if we end up
> > having the buffer allocation in the frontend.
> > 
> > For the bindings folks:
> > 
> > I'm introducing a new io-backends property in the ad9467 bindings but I'm
> > not sure this is the way to do it. Ideally that new property become a
> > generic schema and I'm guessing I should send a PULL to?
> > 
> > https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/iio/iio-consumer.yaml
> 
> That seems like the right thing to do to me, depending on how widespread
> the use of these backends might be. What is seemingly missing though,
> from this cover and from the bindings patch in the series in particular,
> is an explanation of what the "iio-backends" hardware actually is.
> 

Yeah, sorry about the bindings patch but I was already with the feeling that a PR in
devicetree-org to be the right place. I'll be adding more drivers needing that
property and STM also wants make use this.

I'll improve on the explanation and send a PR for a generic schema.

> There is some text below, but it does not seem complete to me. Is the
> idea that this "backend" is shared between multiple frontend consumers?
> The one example is described as being "highly focused on ADI usecases"
> 

For now it cannot really be shared. The code is not prepared for it (we would need to
keep enable/disable counters etc...). For now, I'm just adding the simpler cases of
1:1 and 1:n (1 frontend for multiple backends). Internally we do have 1:n designs
that I definitely want (in time) to bring upstream.

That said, having a usecase for it in the future, it is something that can be added,
yes...

Thanks for the feedback!
- Nuno Sá
>