Re: [PATCH 4/8] iio: backend: add API for interface configuration

["Nuno Sá" <noname.nuno@gmail.com>]

On Mon, 2024-12-16 at 21:36 +0100, Angelo Dureghello wrote:
> From: Antoniu Miclaus <antoniu.miclaus@analog.com>
> 
> Add backend support for setting and getting the interface type
> in use.
> 
> Link:
> https://lore.kernel.org/linux-iio/20241129153546.63584-1-antoniu.miclaus@analog.com/T/#m6d86939078d780512824f1540145aade38b0990b
> Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
> Co-developed-by: Angelo Dureghello <adureghello@baylibre.com>
> Signed-off-by: Angelo Dureghello <adureghello@baylibre.com>
> ---
> This patch has been picked up from the Antoniu patchset
> still not accepted, and extended with the interface setter,
> fixing also namespace names to be between quotation marks.
> ---
>  drivers/iio/industrialio-backend.c | 42
> ++++++++++++++++++++++++++++++++++++++
>  include/linux/iio/backend.h        | 19 +++++++++++++++++
>  2 files changed, 61 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-
> backend.c
> index 363281272035..6edc3e685f6a 100644
> --- a/drivers/iio/industrialio-backend.c
> +++ b/drivers/iio/industrialio-backend.c
> @@ -636,6 +636,48 @@ ssize_t iio_backend_ext_info_set(struct iio_dev
> *indio_dev, uintptr_t private,
>  }
>  EXPORT_SYMBOL_NS_GPL(iio_backend_ext_info_set, "IIO_BACKEND");
>  
> +/**
> + * iio_backend_interface_type_get - get the interface type used.
> + * @back: Backend device
> + * @type: Interface type
> + *
> + * RETURNS:
> + * 0 on success, negative error number on failure.
> + */
> +int iio_backend_interface_type_get(struct iio_backend *back,
> +				   enum iio_backend_interface_type *type)
> +{
> +	int ret;
> +
> +	ret = iio_backend_op_call(back, interface_type_get, type);
> +	if (ret)
> +		return ret;
> +
> +	if (*type >= IIO_BACKEND_INTERFACE_MAX)
> +		return -EINVAL;
> +
> +	return 0;
> +}
> +EXPORT_SYMBOL_NS_GPL(iio_backend_interface_type_get, "IIO_BACKEND");
> +
> +/**
> + * iio_backend_interface_type_set - set the interface type used.
> + * @back: Backend device
> + * @type: Interface type
> + *
> + * RETURNS:
> + * 0 on success, negative error number on failure.
> + */
> +int iio_backend_interface_type_set(struct iio_backend *back,
> +				   enum iio_backend_interface_type type)
> +{
> +	if (type >= IIO_BACKEND_INTERFACE_MAX)
> +		return -EINVAL;
> +
> +	return  iio_backend_op_call(back, interface_type_set, type);
> +}
> +EXPORT_SYMBOL_NS_GPL(iio_backend_interface_type_set, "IIO_BACKEND");
> +
>  /**
>   * iio_backend_extend_chan_spec - Extend an IIO channel
>   * @back: Backend device
> diff --git a/include/linux/iio/backend.h b/include/linux/iio/backend.h
> index 10be00f3b120..2b7221099d8c 100644
> --- a/include/linux/iio/backend.h
> +++ b/include/linux/iio/backend.h
> @@ -70,6 +70,15 @@ enum iio_backend_sample_trigger {
>  	IIO_BACKEND_SAMPLE_TRIGGER_MAX
>  };
>  
> +enum iio_backend_interface_type {
> +	IIO_BACKEND_INTERFACE_SERIAL_LVDS,
> +	IIO_BACKEND_INTERFACE_SERIAL_CMOS,

The above are apparently not used in the next patch so I would not add them now.
> +	IIO_BACKEND_INTERFACE_SERIAL_SPI,
> +	IIO_BACKEND_INTERFACE_SERIAL_DSPI,
> +	IIO_BACKEND_INTERFACE_SERIAL_QSPI,

I'll throw my 2 cents but it would be nice to have more feedback on this. I'm
not completely sure about the xSPI stuff in here. We treated the QSPI as a bus
both for control and data in which we also add child devices. And we've been
adding specific bus operations/configurations through the 'struct
ad3552r_hs_platform_data' interface. So, I'm wondering if this should also not
be set through that interface?

LVDS/CMOS still looks slightly different to me...

- Nuno Sá