GPIO(4) BSD Kernel Interfaces Manual GPIO(4)NAMEgpio — General Purpose Input/Output
SYNOPSIS
gpio* at elansc?
gpio* at epgpio?
gpio* at gcscpcib?
gpio* at gpiosim?
gpio* at gscpcib?
gpio* at ichlpcib?
gpio* at nsclpcsio?
gpio* at ppbus?
#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 user‐
land is performed through ioctl(2) calls on these devices.
Whether the layout of the GPIO device can be configured is subject to
authorization by the kauth(9) framework.
If for example secmodel_securelevel(9) is active, the layout of the GPIO
device is defined at a securelevel less than 1, 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 a securelevel less than 1. 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 */
};
GPIOREAD (struct gpio_req)
Returns the input pin value in the gpio_pin_op structure:
#define GPIOMAXNAME 64
struct gpio_req {
char gp_name[GPIOMAXNAME]; /* pin name */
int gp_pin; /* pin number */
int gp_value; /* value */
};
The gp_name or gp_pin field must be set before calling.
GPIOWRITE (struct gpio_req)
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.
GPIOTOGGLE (struct gpio_req)
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.
GPIOSET (struct gpio_set)
Changes pin configuration flags with the new ones provided in the
gpio_set structure:
#define GPIOMAXNAME 64
struct gpio_set {
char gp_name[GPIOMAXNAME]; /* pin name */
int gp_pin; /* pin number */
int gp_caps; /* pin capabilities (ro) */
int gp_flags; /* pin configuration flags */
char gp_name2[GPIOMAXNAME]; /* 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
GPIO_PIN_PULSATE pulsate 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 GPIOSET will be accessible
at securelevels greater than 0.
GPIOUNSET (struct gpio_set)
Unset the specified pin, i.e. clear its name and make it unaccessi‐
ble 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 */
uint32_t ga_mask; /* binary mask */
uint32_t ga_flags; /* driver dependent */
};
The drvctl(8) command can be used to detach a device from a gpio
pin.
FILES
/dev/gpiou GPIO device unit u file.
SEE ALSOioctl(2), drvctl(8), gpioctl(8)HISTORY
The gpio device first appeared in OpenBSD 3.6 and NetBSD 4.0.
AUTHORS
The gpio driver was written by Alexander Yurchenko ⟨grange@openbsd.org⟩.
gpio and was ported to NetBSD by Jared D. McNeill ⟨jmcneill@NetBSD.org⟩.
Runtime device attachment was added by Marc Balmer ⟨marc@msys.ch⟩.
BUGS
Event capabilities are not supported.
BSD November 13, 2011 BSD
