Re: [PATCH v3 0/8] iio: add new backend framework

[Rob Herring <robh@kernel.org>]

On Wed, Dec 13, 2023 at 04:02:31PM +0100, Nuno Sa wrote:
> v1:
>  https://lore.kernel.org/linux-iio/20231204144925.4fe9922f@jic23-huawei/T/#m222f5175273b81dbfe40b7f0daffcdc67d6cb8ff
> 
> v2:
>  https://lore.kernel.org/r/20231208-dev-iio-backend-v2-0-5450951895e1@analog.com
> 
> Changes in v3:
> - Patch 1:
>  * Use proposed generic schema [1]. Also make it a required property;
>  * Improved the commit message.
> - Patch 2:
>  * Improved commit message.
> - Patch 4:
>  * Namespace all IIO DMAENGINE buffer exports;
>  * Removed unrelated new line removal change.
> - Patch 5:
>  * Namespace all IIO backend exports.
> - Patch 6:
>  * Set backend.h in alphabetical order;
>  * Import IIO backend namespace.
> - Patch 7:
>  * Don't depend on OF in kbuild anymore;
>  * Import IIO backend namespace.
> 
> For the bindings patches, I tried not to enter into much details about
> the IIO framework as I think specifics of the implementation don't care
> from the bindings perspective. Hopefully the commit messages are good
> enough.
> 
> I'm also aware that patch 1 is not backward compatible but we are
> anyways doing it on the driver side (and on the driver the property is
> indeed required). Anyways, just let me know if making the property
> required is not acceptable (I'm fairly confident no one was using the
> upstream version of the driver and so validating devicetrees for it). 
> 
> Keeping the block diagram in v3's cover so we don't have to follow links
> to check the one of the typicals setups. 
> 
>                                            -------------------------------------------------------
>  ------------------                        | -----------         ------------      -------  FPGA |
>  |     ADC        |------------------------| | AXI ADC |---------| DMA CORE |------| RAM |       |
>  | (Frontend/IIO) | Serial Data (eg: LVDS) | |(backend)|---------|          |------|     |       |
>  |                |------------------------| -----------         ------------      -------       |
>  ------------------                        -------------------------------------------------------

Why doesn't axi-adc just have an io-channels property to adc? It's the 
opposite direction for the link, but it seems more logical to me that 
axi-adc depends on adc rather than the other way around.

And if there's another consumer in the chain, then a node could 
certainly be both an io-channels consumer and producer.

The architecture of the drivers seems odd to me. It looks similar to 
making a phy driver handle all the state and protocol with the host 
controller being a backend.

Rob