Re: [PATCH v3 1/4] iio: add IIO_MOD_REFERENCE modifier

[Jonathan Cameron <jic23@jic23.retrosnub.co.uk>]

On Sun, 12 Dec 2021 18:40:54 -0800
Gwendal Grignou <gwendal@chromium.org> wrote:

> Add modifier IIO_MOD_REFERENCE for reporting sx9360 reference
> proximity measurement.
> All modifier must be defined for libiio to recognize
> |in_proximity_reference| as a channel.
> 
> Signed-off-by: Gwendal Grignou <gwendal@chromium.org>
Hmm. So the question is whether this is a valid modifier.

I'm not totally convinced, because I can see we might well
get stacking cases say

iio_concentration_o2_reference

However we do have precedence with 'ambient' which applies
to temperature sensors.

The alternative here would be to have it as a normal indexed
channel but with a label saying it is the reference.

Would that work for this case?  If I were doing the ambient
case again I'd use label for that as well, but label is a more
recent addition to the ABI.

> ---
> New in v3.
> 
>  drivers/iio/industrialio-core.c | 1 +
>  include/uapi/linux/iio/types.h  | 1 +
>  2 files changed, 2 insertions(+)
> 
> diff --git a/drivers/iio/industrialio-core.c b/drivers/iio/industrialio-core.c
> index 20d5178ca0739a..2b272f54de8ae9 100644
> --- a/drivers/iio/industrialio-core.c
> +++ b/drivers/iio/industrialio-core.c
> @@ -134,6 +134,7 @@ static const char * const iio_modifier_names[] = {
>  	[IIO_MOD_ETHANOL] = "ethanol",
>  	[IIO_MOD_H2] = "h2",
>  	[IIO_MOD_O2] = "o2",
> +	[IIO_MOD_REFERENCE] = "reference",
>  };
>  
>  /* relies on pairs of these shared then separate */
> diff --git a/include/uapi/linux/iio/types.h b/include/uapi/linux/iio/types.h
> index 48c13147c0a870..aa83a9b578502a 100644
> --- a/include/uapi/linux/iio/types.h
> +++ b/include/uapi/linux/iio/types.h
> @@ -95,6 +95,7 @@ enum iio_modifier {
>  	IIO_MOD_ETHANOL,
>  	IIO_MOD_H2,
>  	IIO_MOD_O2,
> +	IIO_MOD_REFERENCE,
>  };
>  
>  enum iio_event_type {