linux/Documentation/devicetree/bindings/leds/leds-gpio.txt

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LEDs connected to GPIO lines
Required properties:
- compatible : should be "gpio-leds".
Each LED is represented as a sub-node of the gpio-leds device. Each
node's name represents the name of the corresponding LED.
LED sub-node properties:
- gpios : Should specify the LED's GPIO, see "gpios property" in
Documentation/devicetree/bindings/gpio/gpio.txt. Active low LEDs should be
indicated using flags in the GPIO specifier.
- label : (optional)
see Documentation/devicetree/bindings/leds/common.txt
- linux,default-trigger : (optional)
see Documentation/devicetree/bindings/leds/common.txt
- default-state: (optional) The initial state of the LED. Valid
values are "on", "off", and "keep". If the LED is already on or off
and the default-state property is set the to same value, then no
glitch should be produced where the LED momentarily turns off (or
on). The "keep" setting will keep the LED at whatever its current
state is, without producing a glitch. The default is off if this
property is not present.
Examples:
leds {
compatible = "gpio-leds";
hdd {
label = "IDE Activity";
gpios = <&mcu_pio 0 1>; /* Active low */
linux,default-trigger = "ide-disk";
};
fault {
gpios = <&mcu_pio 1 0>;
/* Keep LED on if BIOS detected hardware fault */
default-state = "keep";
};
};
run-control {
compatible = "gpio-leds";
red {
gpios = <&mpc8572 6 0>;
default-state = "off";
};
green {
gpios = <&mpc8572 7 0>;
default-state = "on";
};
};