Re: [PATCH v2 2/3] input: pwm-beeper: add documentation for volume devicetree bindings

[Rob Herring <robh@kernel.org>]

On Fri, Oct 07, 2016 at 09:08:17AM +0000, Schrempf Frieder wrote:
> This patch adds the documentation for the devicetree bindings to set
> the volume levels.
> 
> Signed-off-by: Frieder Schrempf <frieder.schrempf@exceet.de>
> ---
> Changes in v2:
>  - split into 3 separate patches
>  - make volume properties optional
> 
>  .../devicetree/bindings/input/pwm-beeper.txt       | 22 ++++++++++++++++++++++
>  1 file changed, 22 insertions(+)
> 
> diff --git a/Documentation/devicetree/bindings/input/pwm-beeper.txt b/Documentation/devicetree/bindings/input/pwm-beeper.txt
> index be332ae..6d8ba4e 100644
> --- a/Documentation/devicetree/bindings/input/pwm-beeper.txt
> +++ b/Documentation/devicetree/bindings/input/pwm-beeper.txt
> @@ -5,3 +5,25 @@ Registers a PWM device as beeper.
>  Required properties:
>  - compatible: should be "pwm-beeper"
>  - pwms: phandle to the physical PWM device
> +
> +Optional properties:
> +- volume-levels: Array of distinct 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).

What does the index correspond to? The linear volume?

> +- default-volume-level: the default volume level (index into the
> +      array defined by the "volume-levels" property)
> +
> +The volume level can be set via sysfs under /sys/class/input/inputX/volume.
> +The maximum volume level index can be read from /sys/class/input/inputX/max_volume_level.
> +
> +Example:
> +
> +	pwm-beeper {
> +		compatible = "pwm-beeper";
> +		pwms = <&pwm4 0 5000>;
> +		volume-levels = <0 8 20 40 500>;
> +		default-volume-level = <4>;
> +	};
> -- 
> 1.9.1