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

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Date:   Thu, 26 Jan 2023 16:20:36 +0100
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Manuel Traut <manuel.traut@...com>
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

On 26/01/2023 16:11, Manuel Traut wrote:
>> 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.

sysfs is not related to bindings. To rephrase your question: what shall
be shown in anywhere if the index is not correct? The same problem, the
same solution.

Best regards,
Krzysztof