NAME¶
gpiobus
—
GPIO bus system
SYNOPSIS¶
To compile these devices into your kernel and use the device hints, place the
following lines in your kernel configuration file:
device gpio
device gpioc
device gpioiic
device gpioled
Additional device entries for the
ARM
architecure
include:
device a10_gpio
device bcm_gpio
device imx51_gpio
device lpcgpio
device mv_gpio
device ti_gpio
device gpio_avila
device gpio_cambria
device zy7_gpio
device pxagpio
Additional device entries for the
MIPS
architecure
include:
device ar71xxx_gpio
device octeon_gpio
device rt305_gpio
Additional device entries for the
POWERPC
architecure
include:
device wiigpio
device macgpio
DESCRIPTION¶
The
gpiobus system provides a simple interface to
the GPIO pins that are usually available on embedded architectures and can
provide bit banging style devices to the system.
The acronym
GPIO
means “General-Purpose
Input/Output.”
The BUS physically consists of multiple pins that can be configured for
input/output, IRQ delivery, SDA/SCL
iicbus use,
etc.
On some embedded architechtures (like MIPS), discovery of the bus and
configuration of the pins is done via
device.hints(5) in the platform's kernel
config(5) file.
On some others (like ARM), where
FDT(4) is used to
describe the device tree, the bus discovery is done via the DTS passed to the
kernel, being either statically compiled in, or by a variety of ways where the
boot loader (or Open Firmware enabled system) passes the DTS blob to kernel at
boot.
The following are only provided by the
ar71xx_gpio
driver.
- hint.gpio.%d.pinmask
- This is a bitmask of pins on the gpio board that we would like to expose
for use to the host o/s. To expose pin 0, 4 and 7, use the bitmask of
10010001 converted to the hexadecimal value 0x0091.
- hint.gpio.%d.pinon
- This is a bitmask of pins on the gpio board that will be set to ON at host
start. To set pin 2, 5 and 13 to be set ON at boot, use the bitmask of
10000000010010 converted to the hexadecimal value 0x2012.
- hint.gpio.function_set
-
- hint.gpio.function_clear
- These are a bitmask of pins that will remap a pin to handle a specific
function (USB, UART TX/RX, etc) in the Atheros function registers. This is
mainly used to set/clear functions that we need when they are setup or not
setup by uBoot.
Simply put, each pin of the GPIO interface is connected to an input/output of
some device in a system.
SEE ALSO¶
gpioiic(4),
gpioled(4),
iicbus(4),
gpioctl(8)
HISTORY¶
The
gpiobus
manual page first appeared in
FreeBSD 10.0.
AUTHORS¶
This manual page was written by
Sean Bruno
⟨sbruno@FreeBSD.org⟩.