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

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Date:   Thu, 26 Jan 2023 16:11:49 +0100
From:   Manuel Traut <manuel.traut@...com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
Cc:     linux-kernel@...r.kernel.org,
        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

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

OK, will be done in v9.

> > ---
> >  .../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.

OK, this is also fine for me. Chaned the description and implementation
for v9.
 
> > +    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.

I am not so happy with this suggestion. What shall be displayed in
sysfs as volume if a user specifies a value that is not defined in
the array.. So I tend to keep this as is.

Thanks for your feedback
Manuel

> > +    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
> 

-- 
Manuel Traut