GPIOLED(4) Device Drivers Manual GPIOLED(4)

gpioled — GPIO LED generic device driver

To compile this driver into the kernel, place the following lines in your kernel configuration file:

device gpio
device gpioled

The gpioled driver provides glue to attach a led(4) compatible device to a GPIO pin. Each LED in the system has a name which is used to export a device as /dev/led/<name>. The GPIO pin can then be controlled by writing to this device as described in led(4).

On a device.hints(5) based system, like MIPS, these values are configurable for gpioled:

hint.gpioled.%d.at
The gpiobus you are attaching to. Normally assigned to gpiobus0.
hint.gpioled.%d.name
Arbitrary name of device in /dev/led/ to create for led(4).
hint.gpioled.%d.pins
Which pin on the GPIO interface to map to this instance. Please note that this mask should only ever have one bit set (any other bits - i.e., pins - will be ignored).
hint.gpioled.%d.invert
If set to 1, the pin will be set to 0 to light the LED, and 1 to clear it.
hint.gpioled.%d.state
The initial state of the LED when the driver takes control over it. If set to 1 or 0, the LED will be on or off correspondingly. If set to -1, the LED will be kept in its original state.

On a FDT(4) based system, like ARM, the DTS part for a gpioled device usually looks like:

gpio: gpio {

	gpio-controller;
	...

	led0 {
		compatible = "gpioled";
		gpios = <&gpio 16 2 0>;		/* GPIO pin 16. */
		name = "ok";
	};

	led1 {
		compatible = "gpioled";
		gpios = <&gpio 17 2 0>;		/* GPIO pin 17. */
		name = "user-led1";
	};
};

Optionally, you can choose to combine all the LEDs under a single “gpio-leds” compatible node:

simplebus0 {

	...

	leds {
		compatible = "gpio-leds";

		led0 {
			gpios = <&gpio 16 2 0>;
			name = "ok"
		};

		led1 {
			gpios = <&gpio 17 2 0>;
			name = "user-led1"
		};
	};
};

Both methods are equally supported and it is possible to have the LEDs defined with any sort of mix between the methods. The only restriction is that a GPIO pin cannot be mapped by two different (gpio)leds.

For more details about the gpios property, please consult /usr/src/sys/dts/bindings-gpio.txt.

The property name is the arbitrary name of the device in /dev/led/ to create for led(4).

fdt(4), gpio(4), gpioiic(4), led(4)

The gpioled manual page first appeared in FreeBSD 10.1.

This manual page was written by Luiz Otavio O Souza.

May 23, 2019 Debian