linux-kernel - Re: [PATCH v8 4/5] dt-bindings: input: pwm-beeper: add volume

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Date:   Thu, 26 Jan 2023 13:36:21 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Manuel Traut <manuel.traut@...com>, linux-kernel@...r.kernel.org
Cc:     Dmitry Torokhov <dmitry.torokhov@...il.com>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Frieder Schrempf <frieder.schrempf@...tron.de>,
        linux-input@...r.kernel.org, devicetree@...r.kernel.org
Subject: Re: [PATCH v8 4/5] dt-bindings: input: pwm-beeper: add volume

On 26/01/2023 10:18, Manuel Traut wrote:
> Adds an array of supported volume levels and a default volume level.
> 
> Signed-off-by: Manuel Traut <manuel.traut@...com>

This is the second patch. Bindings must be introduced before you start
using them.

> ---
>  .../devicetree/bindings/input/pwm-beeper.yaml | 20 +++++++++++++++++++
>  1 file changed, 20 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/input/pwm-beeper.yaml b/Documentation/devicetree/bindings/input/pwm-beeper.yaml
> index 351df83d5cbe..f1f9283ca855 100644
> --- a/Documentation/devicetree/bindings/input/pwm-beeper.yaml
> +++ b/Documentation/devicetree/bindings/input/pwm-beeper.yaml
> @@ -26,6 +26,24 @@ properties:
>    beeper-hz:
>      description: bell frequency in Hz
>  
> +  volume-levels:

use -bp suffix:
https://github.com/devicetree-org/dt-schema/blob/main/dtschema/schemas/property-units.yaml#L44

which will mean the unit is 1/100 of %, not 1/10. Then you can also drop
the $ref.


> +    description: >
> +      Array of PWM duty cycle values that correspond to
> +      linear volume levels. These need to be in the range of
> +      0 to 500, while 0 means 0% duty cycle (mute) and 500
> +      means 50% duty cycle (max volume).
> +      Please note that the actual volume of most beepers is
> +      highly non-linear, which means that low volume levels
> +      are probably somewhere in the range of 1 to 30 (0.1-3%
> +      duty cycle).
> +    $ref: /schemas/types.yaml#/definitions/uint32-array
> +
> +  default-volume-level:

I propose to use just the value, not the index, so the name should
finish with '-bp' and the $ref can be dropped.

> +    description: >
> +      The default volume level (index into the array defined
> +      by the "volume-levels" property).
> +    $ref: /schemas/types.yaml#/definitions/uint32
> +
>  required:
>    - compatible
>    - pwms
> @@ -45,4 +63,6 @@ examples:
>        compatible = "pwm-beeper";
>        pwms = <&pwm0>;
>        amp-supply = <&beeper_amp>;
> +      volume-levels = <0 8 20 40 500>;
> +      default-volume-level = <4>;
>      };

Best regards,
Krzysztof