gpiokeys: add a basic manual page
Reviewed by: manu, bjk, 0mp MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D25939
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Andriy Gapon
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share/man/man4/gpiokeys.4
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152
share/man/man4/gpiokeys.4
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.\"
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.\" SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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.\"
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.\" Copyright (c) 2020 Andriy Gapon <avg@FreeBSD.org>
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
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.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
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.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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.\" SUCH DAMAGE.
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.\"
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.\" $FreeBSD$
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.\"
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.Dd August 5, 2020
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.Dt GPIOKEYS 4
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.Os
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.Sh NAME
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.Nm gpiokeys
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.Nd GPIO keys device driver
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.Sh SYNOPSIS
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To compile this driver into the kernel,
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place the following lines in your
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kernel configuration file:
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.Bd -ragged -offset indent
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.Cd "options FDT"
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.Cd "device gpio"
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.Cd "device gpiokeys"
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.Ed
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.Pp
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Alternatively, to load the driver as a
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module at boot time, place the following line in
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.Xr loader.conf 5 :
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.Bd -literal -offset indent
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gpiokeys_load="YES"
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.Ed
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.Sh DESCRIPTION
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The
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.Nm
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driver provides a way to represent a set of general purpose inputs as a
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.Xr keyboard 4
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device.
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At the moment the driver supports only
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.Xr FDT 4
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based systems.
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The DTS determines what pins are mapped to buttons and what key codes are
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generated for each virtual button.
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The
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.Xr keyboard 4
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device can be used from userland to monitor for input changes.
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.Pp
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On an
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.Xr FDT 4
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based system
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the DTS part for a
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.Nm
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device usually looks like:
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.Bd -literal
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/ {
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...
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gpio_keys {
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compatible = "gpio-keys";
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btn1 {
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label = "button1";
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linux,code = <KEY_1>;
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gpios = <&gpio 0 3 GPIO_ACTIVE_LOW>
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};
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btn2 {
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label = "button2";
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linux,code = <KEY_2>;
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gpios = <&gpio 0 4 GPIO_ACTIVE_LOW>
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};
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};
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};
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.Ed
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.Pp
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For more details about the
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.Va gpios
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property, please consult
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.Pa /usr/src/sys/dts/bindings-gpio.txt .
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.Pp
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The
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.Nm
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driver supports two properties for specifying a key code.
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.Pp
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The property
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.Va freebsd,code
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specifies a
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.Fx
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native scancode compatible with
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.Xr kbdmap 5
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keyboard maps.
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.Pp
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The property
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.Va linux,code
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specifies an evdev scancode.
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That scancode is internally translated to a native scancode.
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Note that not all evdev scancodes have corresponding native scancodes.
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If a scancode cannot be translated, then a diagnostic message is printed
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and the input is ignored.
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.Pp
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The property
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.Va label
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is a descriptive name of a button.
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It is used for diagnostic messages only.
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This property is optional.
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If not set, the node name is used in its place.
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.Pp
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The property
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.Va autorepeat
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determines whether autorepeat is enabled for a button.
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.Pp
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The property
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.Va debounce-interval
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defines debouncing interval time in milliseconds.
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If not specified the interval defaults to 5.
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.Sh SEE ALSO
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.Xr fdt 4 ,
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.Xr gpio 4 ,
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.Xr keyboard 4 ,
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.Xr kbdmap 5
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.Sh HISTORY
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The
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.Nm
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manual page first appeared in
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.Fx 12.2 .
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.Sh AUTHORS
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The
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.Nm
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driver was written by
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.An Oleksandr Tymoshenko Aq Mt gonzo@FreeBSD.org .
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This
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manual page was written by
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.An Andriy Gapon Aq Mt avg@FreeBSD.org .
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