GPIO(4) FreeBSD Kernel Interfaces Manual GPIO(4)
NAME
gpio - General Purpose Input/Output
SYNOPSIS
gpio* at ath?
gpio* at bcmgpio? (arm64, armv7)
gpio* at glxpcib? (i386)
gpio* at gscpcib? (i386)
gpio* at isagpio?
gpio* at mpfgpio? (riscv64)
gpio* at nsclpcsio?
gpio* at omgpio? (armv7)
gpio* at pcagpio?
gpio* at pcaled?
gpio* at skgpio? (amd64, i386)
gpio* at sxipio? (arm64, armv7)
gpio0 at voyager? (loongson)
#include <sys/types.h>
#include <sys/gpio.h>
#include <sys/ioctl.h>
DESCRIPTION
The gpio device attaches to the GPIO controller and provides a uniform
programming interface to its pins.
Each GPIO controller with an attached gpio device has an associated
device file under the /dev directory, e.g. /dev/gpio0. Access from
userland is performed through ioctl(2) calls on these devices.
The layout of the GPIO device is defined at securelevel 0, i.e. typically
during system boot, and cannot be changed later. GPIO pins can be
configured and given a symbolic name and device drivers that use GPIO
pins can be attached to the gpio device at securelevel 0. All other pins
will not be accessible once the runlevel has been raised.
IOCTL INTERFACE
The following structures and constants are defined in the <sys/gpio.h>
header file:
GPIOINFO struct gpio_info
Returns information about the GPIO controller in the gpio_info
structure:
struct gpio_info {
int gpio_npins; /* total number of pins available */
};
GPIOPINREAD struct gpio_pin_op
Returns the input pin value in the gpio_pin_op structure:
#define GPIOPINMAXNAME 64
struct gpio_pin_op {
char gp_name[GPIOPINMAXNAME]; /* pin name */
int gp_pin; /* pin number */
int gp_value; /* value */
};
The gp_name or gp_pin field must be set before calling.
GPIOPINWRITE struct gpio_pin_op
Writes the output value to the pin. The value set in the gp_value
field must be either GPIO_PIN_LOW (logical 0) or GPIO_PIN_HIGH
(logical 1). On return, the gp_value field contains the old pin
state.
GPIOPINTOGGLE struct gpio_pin_op
Toggles the pin output value, i.e. changes it to the opposite.
gp_value field is ignored and on return contains the old pin state.
GPIOPINSET struct gpio_pin_set
Changes pin configuration flags with the new ones provided in the
gpio_pin_set structure:
#define GPIOPINMAXNAME 64
struct gpio_pin_set {
char gp_name[GPIOPINMAXNAME]; /* pin name */
int gp_pin; /* pin number */
int gp_caps; /* pin capabilities (ro) */
int gp_flags; /* pin configuration flags */
char gp_name2[GPIOPINMAXNAME]; /* new name */
};
The gp_flags field is a combination of the following flags:
GPIO_PIN_INPUT input direction
GPIO_PIN_OUTPUT output direction
GPIO_PIN_INOUT bi-directional
GPIO_PIN_OPENDRAIN open-drain output
GPIO_PIN_PUSHPULL push-pull output
GPIO_PIN_TRISTATE output disabled
GPIO_PIN_PULLUP internal pull-up enabled
GPIO_PIN_PULLDOWN internal pull-down enabled
GPIO_PIN_INVIN invert input
GPIO_PIN_INVOUT invert output
Note that the GPIO controller may not support all of these flags.
On return the gp_caps field contains flags that are supported. If
no flags are specified, the pin configuration stays unchanged.
Only GPIO pins that have been set using GPIOPINSET will be
accessible at securelevels greater than 0.
GPIOPINUNSET struct gpio_pin_set
Unset the specified pin, i.e. clear its name and make it
inaccessible at securelevels greater than 0.
GPIOATTACH struct gpio_attach
Attach the device described in the gpio_attach structure on this
gpio device.
struct gpio_attach {
char ga_dvname[16]; /* device name */
int ga_offset; /* pin number */
u_int32_t ga_mask; /* binary mask */
};
GPIODETACH struct gpio_attach
Detach a device from this gpio device that was previously attached
using the GPIOATTACH ioctl(2). The ga_offset and ga_mask fields of
the gpio_attach structure are ignored.
FILES
/dev/gpiou GPIO device unit u file.
SEE ALSO
ioctl(2), gpioctl(8)
HISTORY
The gpio device first appeared in OpenBSD 3.6.
AUTHORS
The gpio driver was written by Alexander Yurchenko <
[email protected]>.
Runtime device attachment was added by Marc Balmer <
[email protected]>.
BUGS
Event capabilities are not supported.
FreeBSD 14.1-RELEASE-p8 January 17, 2023 FreeBSD 14.1-RELEASE-p8