Re: [PATCH v2 09/11] iio: backend: add new functionality

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 5 Apr 2024 17:00:07 +0200
Nuno Sa <nuno.sa@analog.com> wrote:

> This adds the needed backend ops for supporting a backend inerfacing
> with an high speed dac. The new ops are:
> 
> * data_source_set();
> * set_sampling_freq();
> * extend_chan_spec();
> * ext_info_set();
> * ext_info_get().
> 
> Also to note the new helpers that are meant to be used by the backends
> when extending an IIO channel (adding extended info):
> 
> * iio_backend_ext_info_set();
> * iio_backend_ext_info_get().
> 
> Signed-off-by: Nuno Sa <nuno.sa@analog.com>

Whilst the code for the backend retrieval callback is simple
I wonder if we are better off just not having it for now.

Keep the infrastructure that checks for the default approach not working
but don't actually provide the alternative until we need it.

Advantage is pretty minor though so maybe just keep it.
Unless others have strong opinions, up to you to decide whether to keep it.

One trivial thing noticed inline.

> ---
>  drivers/iio/industrialio-backend.c | 179 +++++++++++++++++++++++++++++++++++++
>  include/linux/iio/backend.h        |  49 ++++++++++
>  2 files changed, 228 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-backend.c b/drivers/iio/industrialio-backend.c
> index 2fea2bbbe47f..ac554798897f 100644
> --- a/drivers/iio/industrialio-backend.c
> +++ b/drivers/iio/industrialio-backend.c
> @@ -29,6 +29,7 @@
>   *
>   * Copyright (C) 2023-2024 Analog Devices Inc.
>   */
> +#include "asm-generic/errno-base.h"

You'll need a strong reason if you want to do that include rather than
a normal one like linux/errno.h

>  #define dev_fmt(fmt) "iio-backend: " fmt
>  
>  #include <linux/cleanup.h>
> @@ -43,10 +44,12 @@
>  #include <linux/types.h>
>  
>  #include <linux/iio/backend.h>
> +#include <linux/iio/iio.h>
>