freebsd-skq/share/man/man4/gpioled.4

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.Dd May 14, 2014
.Dt GPIOLED 4
.Os
.Sh NAME
.Nm gpioled
.Nd GPIO LED generic device driver
.Sh SYNOPSIS
To compile this driver into the kernel,
place the following lines in your
kernel configuration file:
.Bd -ragged -offset indent
.Cd "device gpio"
.Cd "device gpioled"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides glue to attach a
.Xr led 4
compatible device to a GPIO pin.
Each LED in the system has a
.Pa name
which is used to export a device as
.Pa /dev/led/<name> .
The GPIO pin can then be controlled by writing to this device as described
in
.Xr led 4 .
.Pp
On a 
.Xr device.hints 5 
based system, like
.Li MIPS ,
these values are configurable for
.Nm :
.Bl -tag -width ".Va hint.gpioiic.%d.atXXX"
.It Va hint.gpioled.%d.at
The gpiobus you are attaching to.
Normally assigned to gpiobus0.
.It Va hint.gpioled.%d.name
Arbitrary name of device in
.Pa /dev/led/
to create for
.Xr led 4 .
.It Va 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).
.El
.Pp
On a
.Xr FDT 4
based system, like
.Li ARM ,
the DTS part for a
.Nm gpioled
device usually looks like:
.Bd -literal
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";
	};
};
.Ed
.Pp
Optionally, you can choose to combine all the LEDs under a single
.Dq gpio-leds
compatible node:
.Bd -literal
simplebus0 {

	...

	leds {
		compatible = "gpio-leds";

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

		led1 {
			gpios = <&gpio 17 2 0>;
			name = "user-led1"
		};
	};
};
.Ed
.Pp
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.
.Pp
For more details about the
.Va gpios
property, please consult
.Pa /usr/src/sys/boot/fdt/dts/bindings-gpio.txt .
.Pp
The property
.Va name
is the arbitrary name of the device in
.Pa /dev/led/
to create for
.Xr led 4 .
.Sh SEE ALSO
.Xr fdt 4 ,
.Xr gpio 4 ,
.Xr gpioiic 4 ,
.Xr led 4
.Sh HISTORY
The
.Nm
manual page first appeared in
.Fx 10.1 .
.Sh AUTHORS
This
manual page was written by
.An Luiz Otavio O Souza .