GPIO(4)                   OpenBSD Programmer's Manual                  GPIO(4)

NAME
     gpio - General Purpose Input/Output

SYNOPSIS
     gpio* at ath?
     gpio* at elansc? (i386)
     gpio* ar glxpcib? (i386)
     gpio* at gscpcib? (i386)
     gpio* at isagpio?
     gpio* at nsclpcsio?
     gpio* at pcagpio?
     gpio* at pcaled?
     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 de-
     vice file under the /dev directory, e.g. /dev/gpio0.  Access from user-
     land 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 con-
     figured 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 accessi-
           ble at securelevels greater than 0.

     GPIOPINUNSET (struct gpio_pin_set)
           Unset the specified pin, i.e. clear its name and make it inaccessi-
           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 */
                   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 <grange@openbsd.org>.
     Runtime device attachment was added by
     Marc Balmer <mbalmer@openbsd.org>.

BUGS
     Event capabilities are not supported.

OpenBSD 4.7                    February 18, 2010                             3
