diff --git a/doc/device-tree-bindings/input/adc-keys.txt b/doc/device-tree-bindings/input/adc-keys.txt new file mode 100644 index 0000000000..6c8be6a9ac --- /dev/null +++ b/doc/device-tree-bindings/input/adc-keys.txt @@ -0,0 +1,67 @@ +ADC attached resistor ladder buttons +------------------------------------ + +Required properties: + - compatible: "adc-keys" + - io-channels: Phandle to an ADC channel + - io-channel-names = "buttons"; + - keyup-threshold-microvolt: Voltage above or equal to which all the keys are + considered up. + +Optional properties: + - poll-interval: Poll interval time in milliseconds + - autorepeat: Boolean, Enable auto repeat feature of Linux input + subsystem. + +Each button (key) is represented as a sub-node of "adc-keys": + +Required subnode-properties: + - label: Descriptive name of the key. + - linux,code: Keycode to emit. + - press-threshold-microvolt: voltage above or equal to which this key is + considered pressed. + +No two values of press-threshold-microvolt may be the same. +All values of press-threshold-microvolt must be less than +keyup-threshold-microvolt. + +Example: + +#include + + adc-keys { + compatible = "adc-keys"; + io-channels = <&lradc 0>; + io-channel-names = "buttons"; + keyup-threshold-microvolt = <2000000>; + + button-up { + label = "Volume Up"; + linux,code = ; + press-threshold-microvolt = <1500000>; + }; + + button-down { + label = "Volume Down"; + linux,code = ; + press-threshold-microvolt = <1000000>; + }; + + button-enter { + label = "Enter"; + linux,code = ; + press-threshold-microvolt = <500000>; + }; + }; + ++--------------------------------+------------------------+ +| 2.000.000 <= value | no key pressed | ++--------------------------------+------------------------+ +| 1.500.000 <= value < 2.000.000 | KEY_VOLUMEUP pressed | ++--------------------------------+------------------------+ +| 1.000.000 <= value < 1.500.000 | KEY_VOLUMEDOWN pressed | ++--------------------------------+------------------------+ +| 500.000 <= value < 1.000.000 | KEY_ENTER pressed | ++--------------------------------+------------------------+ +| value < 500.000 | no key pressed | ++--------------------------------+------------------------+