linux/Documentation/devicetree/bindings/leds/leds-gpio.txt
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   1LEDs connected to GPIO lines
   2
   3Required properties:
   4- compatible : should be "gpio-leds".
   5
   6Each LED is represented as a sub-node of the gpio-leds device.  Each
   7node's name represents the name of the corresponding LED.
   8
   9LED sub-node properties:
  10- gpios :  Should specify the LED's GPIO, see "gpios property" in
  11  Documentation/devicetree/bindings/gpio/gpio.txt.  Active low LEDs should be
  12  indicated using flags in the GPIO specifier.
  13- label :  (optional)
  14  see Documentation/devicetree/bindings/leds/common.txt
  15- linux,default-trigger :  (optional)
  16  see Documentation/devicetree/bindings/leds/common.txt
  17- default-state:  (optional) The initial state of the LED.  Valid
  18  values are "on", "off", and "keep".  If the LED is already on or off
  19  and the default-state property is set the to same value, then no
  20  glitch should be produced where the LED momentarily turns off (or
  21  on).  The "keep" setting will keep the LED at whatever its current
  22  state is, without producing a glitch.  The default is off if this
  23  property is not present.
  24
  25Examples:
  26
  27leds {
  28        compatible = "gpio-leds";
  29        hdd {
  30                label = "IDE Activity";
  31                gpios = <&mcu_pio 0 1>; /* Active low */
  32                linux,default-trigger = "ide-disk";
  33        };
  34
  35        fault {
  36                gpios = <&mcu_pio 1 0>;
  37                /* Keep LED on if BIOS detected hardware fault */
  38                default-state = "keep";
  39        };
  40};
  41
  42run-control {
  43        compatible = "gpio-leds";
  44        red {
  45                gpios = <&mpc8572 6 0>;
  46                default-state = "off";
  47        };
  48        green {
  49                gpios = <&mpc8572 7 0>;
  50                default-state = "on";
  51        };
  52};
  53