xref: /freebsd/share/man/man4/gpioled.4 (revision fa9896e082a1046ff4fbc75fcba4d18d1f2efc19)

.\" Copyright (c) 2013, Luiz Otavio O Souza <loos@FreeBSD.org>
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.Dd May 23, 2019
.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).
.It Va hint.gpioled.%d.invert
If set to 1, the pin will be set to 0 to light the LED, and 1 to clear it.
.It Va 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.
.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/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 .