Re: [PATCH v5 07/10] dt-bindings: iio: sx9324: Add input analog gain

[Jonathan Cameron <jic23@kernel.org>]

On Fri, 29 Apr 2022 15:01:41 -0700
Gwendal Grignou <gwendal@chromium.org> wrote:

> Allow setting the configure the input analog gain.
> 
> Signed-off-by: Gwendal Grignou <gwendal@chromium.org>

Hi Gwendal.

So, my immediate thought on this is whether it make sense as a
dt controlled thing or not. It's the sort of thing hardwaregain
is for in the userspace ABI. However, I see that's already
in use for the digital gain. This one also unhelpfully applies
to all changes whereas the digital gain is pair wise. Hence
there is basically no way we can map the two controls to a
single ABI element.

So, how would we expect a board designer to set this value?

If the answer is we basically have no idea but some boards do
want it set then I'm fine with this basically being a somewhat magic
value that is in some vague way associated with the antenna setup...

Jonathan

> ---
> New in v5.
> 
>  .../bindings/iio/proximity/semtech,sx9324.yaml        | 11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml b/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml
> index 0be87ac05b97a..d265eb5258c84 100644
> --- a/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml
> +++ b/Documentation/devicetree/bindings/iio/proximity/semtech,sx9324.yaml
> @@ -143,6 +143,17 @@ properties:
>      description:
>        Pre-charge input resistance in Ohm.
>  
> +  semtech,input-analog-gain:
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +    minimum: 0
> +    maximum: 3
> +    description: |
> +      Defines the input antenna analog gain
> +      0: x1.247
> +      1: x1 (default)
> +      2: x0.768
> +      3: x0.552
> +
>  required:
>    - compatible
>    - reg