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

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Date:   Fri, 7 Oct 2016 09:08:17 +0000
From:   Schrempf Frieder <frieder.schrempf@...eet.de>
To:     "robh@...nel.org" <robh@...nel.org>
CC:     "dmitry.torokhov@...il.com" <dmitry.torokhov@...il.com>,
        "pawel.moll@....com" <pawel.moll@....com>,
        "ijc+devicetree@...lion.org.uk" <ijc+devicetree@...lion.org.uk>,
        "galak@...eaurora.org" <galak@...eaurora.org>,
        "luis@...ethencourt.com" <luis@...ethencourt.com>,
        "linux-input@...r.kernel.org" <linux-input@...r.kernel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "Schrempf Frieder" <frieder.schrempf@...eet.de>
Subject: [PATCH v2 2/3] input: pwm-beeper: add documentation for volume
 devicetree bindings

This patch adds the documentation for the devicetree bindings to set
the volume levels.

Signed-off-by: Frieder Schrempf <frieder.schrempf@...eet.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).
+- 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