FreeBSD/Linux Kernel Cross Reference
sys/contrib/device-tree/Bindings/input/gpio-matrix-keypad.txt

     * GPIO driven matrix keypad device tree bindings
     
     GPIO driven matrix keypad is used to interface a SoC with a matrix keypad.
     The matrix keypad supports multiple row and column lines, a key can be
     placed at each intersection of a unique row and a unique column. The matrix
     keypad can sense a key-press and key-release by means of GPIO lines and
     report the event using GPIO interrupts to the cpu.
     
     Required Properties:
    - compatible:           Should be "gpio-matrix-keypad"
    - row-gpios:            List of gpios used as row lines. The gpio specifier
                            for this property depends on the gpio controller to
                            which these row lines are connected.
    - col-gpios:            List of gpios used as column lines. The gpio specifier
                            for this property depends on the gpio controller to
                            which these column lines are connected.
    - linux,keymap:         The definition can be found at
                            bindings/input/matrix-keymap.txt
    
    Optional Properties:
    - linux,no-autorepeat:  do no enable autorepeat feature.
    - wakeup-source:        use any event on keypad as wakeup event.
                            (Legacy property supported: "linux,wakeup")
    - debounce-delay-ms:    debounce interval in milliseconds
    - col-scan-delay-us:    delay, measured in microseconds, that is needed
                            before we can scan keypad after activating column gpio
    - drive-inactive-cols:  drive inactive columns during scan,
                            default is to turn inactive columns into inputs.
    
    Example:
            matrix-keypad {
                    compatible = "gpio-matrix-keypad";
                    debounce-delay-ms = <5>;
                    col-scan-delay-us = <2>;
    
                    row-gpios = <&gpio2 25 0
                                 &gpio2 26 0
                                 &gpio2 27 0>;
    
                    col-gpios = <&gpio2 21 0
                                 &gpio2 22 0>;
    
                    linux,keymap = <0x0000008B
                                    0x0100009E
                                    0x02000069
                                    0x0001006A
                                    0x0101001C
                                    0x0201006C>;
            };

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