dt-bindings: input: adc-keys bindings documentation
Dump adc-keys bindings documentation from Linux kernel source tree from
commit 698dc0cf9447 ("dt-bindings: input: adc-keys: clarify
description").
Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Neil Armstrong <narmstrong@baylibre.com>
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 0000000..6c8be6a
--- /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 <dt-bindings/input/input.h>
+
+ adc-keys {
+ compatible = "adc-keys";
+ io-channels = <&lradc 0>;
+ io-channel-names = "buttons";
+ keyup-threshold-microvolt = <2000000>;
+
+ button-up {
+ label = "Volume Up";
+ linux,code = <KEY_VOLUMEUP>;
+ press-threshold-microvolt = <1500000>;
+ };
+
+ button-down {
+ label = "Volume Down";
+ linux,code = <KEY_VOLUMEDOWN>;
+ press-threshold-microvolt = <1000000>;
+ };
+
+ button-enter {
+ label = "Enter";
+ linux,code = <KEY_ENTER>;
+ 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 |
++--------------------------------+------------------------+