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A common way of multiplexing buttons on a single input in cheap devices is to use a resistor ladder on an ADC. This driver supports that configuration by polling an ADC channel provided by IIO. Acked-by: Jonathan Cameron <jic23@kernel.org> Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com> Acked-by: Rob Herring <robh@kernel.org> Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
50 lines
1.2 KiB
Plaintext
50 lines
1.2 KiB
Plaintext
ADC attached resistor ladder buttons
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Required properties:
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- compatible: "adc-keys"
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- io-channels: Phandle to an ADC channel
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- io-channel-names = "buttons";
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- keyup-threshold-microvolt: Voltage at which all the keys are considered up.
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Optional properties:
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- poll-interval: Poll interval time in milliseconds
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- autorepeat: Boolean, Enable auto repeat feature of Linux input
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subsystem.
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Each button (key) is represented as a sub-node of "adc-keys":
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Required subnode-properties:
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- label: Descriptive name of the key.
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- linux,code: Keycode to emit.
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- press-threshold-microvolt: Voltage ADC input when this key is pressed.
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Example:
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#include <dt-bindings/input/input.h>
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adc-keys {
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compatible = "adc-keys";
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io-channels = <&lradc 0>;
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io-channel-names = "buttons";
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keyup-threshold-microvolt = <2000000>;
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button-up {
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label = "Volume Up";
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linux,code = <KEY_VOLUMEUP>;
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press-threshold-microvolt = <1500000>;
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};
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button-down {
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label = "Volume Down";
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linux,code = <KEY_VOLUMEDOWN>;
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press-threshold-microvolt = <1000000>;
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};
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button-enter {
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label = "Enter";
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linux,code = <KEY_ENTER>;
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press-threshold-microvolt = <500000>;
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};
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};
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