linux-kernel - Re: [PATCH 3/3] dt-bindings: iio: dac: fix ad3552r gain parameter names

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Date: Fri, 10 May 2024 10:43:18 -0500
From: David Lechner <dlechner@...libre.com>
To: Angelo Dureghello <adureghello@...libre.com>
Cc: jic23@...nel.org, robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org, 
	nuno.sa@...log.com, lars@...afoo.de, Michael.Hennerich@...log.com, 
	linux-iio@...r.kernel.org, devicetree@...r.kernel.org, 
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 3/3] dt-bindings: iio: dac: fix ad3552r gain parameter names

On Fri, May 10, 2024 at 9:19 AM Angelo Dureghello
<adureghello@...libre.com> wrote:
>
> From: Angelo Dureghello <adureghello@...libre.com>
>
> The adi,gain-scaling-p/n values are an inverted log2,
> so initial naiming was set correct, but the driver uses just
> adi,gain-scaling-p/n, so uniforming documentation, that seems
> a less-risk fix for future rebases, and still conformant to datasheet.
>
> Signed-off-by: Angelo Dureghello <adureghello@...libre.com>
> ---
>  .../devicetree/bindings/iio/dac/adi,ad3552r.yaml | 16 ++++++++--------
>  1 file changed, 8 insertions(+), 8 deletions(-)
>
> diff --git a/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> index 17442cdfbe27..9e3dbf890bfa 100644
> --- a/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> +++ b/Documentation/devicetree/bindings/iio/dac/adi,ad3552r.yaml
> @@ -94,13 +94,13 @@ patternProperties:
>              maximum: 511
>              minimum: -511
>
> -          adi,gain-scaling-p-inv-log2:
> -            description: GainP = 1 / ( 2 ^ adi,gain-scaling-p-inv-log2)
> +          adi,gain-scaling-p:
> +            description: GainP = 1 / ( 2 ^ adi,gain-scaling-p)
>              $ref: /schemas/types.yaml#/definitions/uint32
>              enum: [0, 1, 2, 3]
>
> -          adi,gain-scaling-n-inv-log2:
> -            description: GainN = 1 / ( 2 ^ adi,gain-scaling-n-inv-log2)
> +          adi,gain-scaling-n:
> +            description: GainN = 1 / ( 2 ^ adi,gain-scaling-n)
>              $ref: /schemas/types.yaml#/definitions/uint32
>              enum: [0, 1, 2, 3]
>
> @@ -109,8 +109,8 @@ patternProperties:
>
>          required:
>            - adi,gain-offset
> -          - adi,gain-scaling-p-inv-log2
> -          - adi,gain-scaling-n-inv-log2
> +          - adi,gain-scaling-p
> +          - adi,gain-scaling-n
>            - adi,rfb-ohms
>
>      required:
> @@ -214,8 +214,8 @@ examples:
>                  reg = <1>;
>                  custom-output-range-config {
>                      adi,gain-offset = <5>;
> -                    adi,gain-scaling-p-inv-log2 = <1>;
> -                    adi,gain-scaling-n-inv-log2 = <2>;
> +                    adi,gain-scaling-p = <1>;
> +                    adi,gain-scaling-n = <2>;
>                      adi,rfb-ohms = <1>;
>                  };
>              };
> --
> 2.45.0.rc1
>
>

The DT bindings are generally considered immutable. So unless we can
prove that no one has ever put adi,gain-scaling-n-inv-log2 in a .dtb
file, we probably need to fix this in the driver rather than in the
bindings. (The driver can still handle adi,gain-scaling-p in the
driver for backwards compatibility but the official binding should be
what was already accepted in the .yaml file)