1.\" Copyright (c) 2013, Sean Bruno <sbruno@freebsd.org> 2.\" All rights reserved. 3.\" 4.\" Redistribution and use in source and binary forms, with or without 5.\" modification, are permitted provided that the following conditions 6.\" are met: 7.\" 1. Redistributions of source code must retain the above copyright 8.\" notice, this list of conditions and the following disclaimer. 9.\" 2. Redistributions in binary form must reproduce the above copyright 10.\" notice, this list of conditions and the following disclaimer in the 11.\" documentation and/or other materials provided with the distribution. 12.\" 13.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND 14.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 15.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 16.\" ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE 17.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 18.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 19.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 20.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 21.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 22.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 23.\" SUCH DAMAGE. 24.\" 25.Dd June 27, 2019 26.Dt GPIO 4 27.Os 28.Sh NAME 29.Nm gpiobus 30.Nd GPIO bus system 31.Sh SYNOPSIS 32To compile these devices into your kernel and use the device hints, place the 33following lines in your kernel configuration file: 34.Bd -ragged -offset indent 35.Cd "device gpio" 36.Cd "device gpioc" 37.Cd "device gpioiic" 38.Cd "device gpioled" 39.Ed 40.Pp 41Additional device entries for the 42.Li ARM 43architecture include: 44.Bd -ragged -offset indent 45.Cd "device a10_gpio" 46.Cd "device bcm_gpio" 47.Cd "device imx51_gpio" 48.Cd "device lpcgpio" 49.Cd "device mv_gpio" 50.Cd "device ti_gpio" 51.Cd "device gpio_avila" 52.Cd "device gpio_cambria" 53.Cd "device zy7_gpio" 54.Cd "device pxagpio" 55.Ed 56.Pp 57Additional device entries for the 58.Li MIPS 59architecture include: 60.Bd -ragged -offset indent 61.Cd "device ar71xxx_gpio" 62.Cd "device octeon_gpio" 63.Cd "device rt305_gpio" 64.Ed 65.Pp 66Additional device entries for the 67.Li POWERPC 68architecture include: 69.Bd -ragged -offset indent 70.Cd "device wiigpio" 71.Cd "device macgpio" 72.Ed 73.Pp 74Additional device entries for the 75.Li RISC-V 76architecture include: 77.Bd -ragged -offset indent 78.Cd "device sifive_gpio" 79.Ed 80.Sh DESCRIPTION 81The 82.Nm 83system provides a simple interface to the GPIO pins that are usually 84available on embedded architectures and can provide bit banging style 85devices to the system. 86.Pp 87The acronym 88.Li GPIO 89means 90.Dq General-Purpose Input/Output. 91.Pp 92The BUS physically consists of multiple pins that can be configured 93for input/output, IRQ delivery, SDA/SCL 94.Em iicbus 95use, etc. 96.Pp 97On some embedded architectures (like MIPS), discovery of the bus and 98configuration of the pins is done via 99.Xr device.hints 5 100in the platform's kernel 101.Xr config 5 102file. 103.Pp 104On some others (like ARM), where 105.Xr FDT 4 106is used to describe the device tree, the bus discovery is done via the DTS 107passed to the kernel, being either statically compiled in, or by a variety 108of ways where the boot loader (or Open Firmware enabled system) passes the 109DTS blob to the kernel at boot. 110.Pp 111On a 112.Xr device.hints 5 113based system these hints can be used to configure drivers for devices 114attached to 115.Nm 116pins: 117.Bl -tag -width ".Va hint.driver.unit.pin_list" 118.It Va hint.driver.unit.at 119The 120.Nm gpiobus 121where the device is attached. 122For example, 123.Qq gpiobus0 . 124.Ar driver 125and 126.Ar unit 127are the driver name and the unit number for the device driver. 128.It Va hint.driver.unit.pins 129This is a bitmask of the pins on the 130.Nm gpiobus 131that are connected to the device. 132The pins will be allocated to the specified driver instance. 133Only pins with numbers from 0 to 31 can be specified using this hint. 134.It Va hint.driver.unit.pin_list 135This is a list of pin numbers of pins on the 136.Nm gpiobus 137that are connected to the device. 138The pins will be allocated to the specified driver instance. 139This is a more user friendly alternative to the 140.Ar pins 141hint. 142Additionally, this hint allows specifying pin numbers greater than 31. 143The numbers can be decimal or hexadecimal with 0x prefix. 144Any non-digit character can be used as a separator. 145For example, it can be a comma, a slash or a space. 146The separator can be followed by any number of space characters. 147.El 148.Pp 149The following 150.Xr device.hints 5 151are only provided by the 152.Cd ar71xx_gpio 153driver: 154.Bl -tag -width ".Va hint.gpio.function_clear" 155.It Va hint.gpio.%d.pinmask 156This is a bitmask of pins on the GPIO board that we would like to expose 157for use to the host operating system. 158To expose pin 0, 4 and 7, use the bitmask of 15910010001 converted to the hexadecimal value 0x0091. 160.It Va hint.gpio.%d.pinon 161This is a bitmask of pins on the GPIO board that will be set to ON at host 162start. 163To set pin 2, 5 and 13 to be set ON at boot, use the bitmask of 16410000000010010 converted to the hexadecimal value 0x2012. 165.It Va hint.gpio.function_set 166.It Va hint.gpio.function_clear 167These are bitmasks of pins that will remap a pin to handle a specific 168function (USB, UART TX/RX, etc) in the Atheros function registers. 169This is mainly used to set/clear functions that we need when they are set up or 170not set up by uBoot. 171.El 172.Pp 173Simply put, each pin of the GPIO interface is connected to an input/output 174of some device in a system. 175.Sh SEE ALSO 176.Xr gpioiic 4 , 177.Xr gpioled 4 , 178.Xr iicbus 4 , 179.Xr device.hints 5 , 180.Xr gpioctl 8 181.Sh HISTORY 182The 183.Nm 184manual page first appeared in 185.Fx 10.0 . 186.Sh AUTHORS 187This 188manual page was written by 189.An Sean Bruno Aq Mt sbruno@FreeBSD.org . 190