xref: /freebsd-src/share/man/man4/gpiokeys.4 (revision fa9896e082a1046ff4fbc75fcba4d18d1f2efc19)

.\"
.\" SPDX-License-Identifier: BSD-2-Clause
.\"
.\" Copyright (c) 2020 Andriy Gapon <avg@FreeBSD.org>
.\"
.\" 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 August 5, 2020
.Dt GPIOKEYS 4
.Os
.Sh NAME
.Nm gpiokeys
.Nd GPIO keys 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 "options FDT"
.Cd "device gpio"
.Cd "device gpiokeys"
.Ed
.Pp
Alternatively, to load the driver as a
module at boot time, place the following line in
.Xr loader.conf 5 :
.Bd -literal -offset indent
gpiokeys_load="YES"
.Ed
.Sh DESCRIPTION
The
.Nm
driver provides a way to represent a set of general purpose inputs as a
.Xr keyboard 4
device.
At the moment the driver supports only
.Xr FDT 4
based systems.
The DTS determines what pins are mapped to buttons and what key codes are
generated for each virtual button.
The
.Xr keyboard 4
device can be used from userland to monitor for input changes.
.Pp
On an
.Xr FDT 4
based system
the DTS part for a
.Nm
device usually looks like:
.Bd -literal
/ {

	...

	gpio_keys {
		compatible = "gpio-keys";

		btn1 {
			label = "button1";
			linux,code = <KEY_1>;
			gpios = <&gpio 0 3 GPIO_ACTIVE_LOW>
		};

		btn2 {
			label = "button2";
			linux,code = <KEY_2>;
			gpios = <&gpio 0 4 GPIO_ACTIVE_LOW>
		};
	};
};
.Ed
.Pp
For more details about the
.Va gpios
property, please consult
.Pa /usr/src/sys/dts/bindings-gpio.txt .
.Pp
The
.Nm
driver supports two properties for specifying a key code.
.Pp
The property
.Va freebsd,code
specifies a
.Fx
native scancode compatible with
.Xr kbdmap 5
keyboard maps.
.Pp
The property
.Va linux,code
specifies an evdev scancode.
That scancode is internally translated to a native scancode.
Note that not all evdev scancodes have corresponding native scancodes.
If a scancode cannot be translated, then a diagnostic message is printed
and the input is ignored.
.Pp
The property
.Va label
is a descriptive name of a button.
It is used for diagnostic messages only.
This property is optional.
If not set, the node name is used in its place.
.Pp
The property
.Va autorepeat
determines whether autorepeat is enabled for a button.
.Pp
The property
.Va debounce-interval
defines debouncing interval time in milliseconds.
If not specified the interval defaults to 5.
.Sh SEE ALSO
.Xr fdt 4 ,
.Xr gpio 4 ,
.Xr keyboard 4 ,
.Xr kbdmap 5
.Sh HISTORY
The
.Nm
manual page first appeared in
.Fx 12.2 .
.Sh AUTHORS
The
.Nm
driver was written by
.An Oleksandr Tymoshenko Aq Mt gonzo@FreeBSD.org .
This
manual page was written by
.An Andriy Gapon Aq Mt avg@FreeBSD.org .