gpio(4) - NetBSD Manual Pages

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GPIO(4)                 NetBSD Kernel Interfaces Manual                GPIO(4)


NAME

     gpio -- 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 soekrisgpio?
     gpio* at ppbus?
     gpio* at ptcd?
     gpio* at wbsio?

     #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_req 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.  If both
           are set, gp_name takes precedence.  On return, the gp_name field
           contains the current name of the pin, if set by the controller
           driver or an earlier call to GPIOSET.

     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
           GPIO_PIN_ALT0 -
           GPIO_PIN_ALT7       select alternate pin function 0 to 7

           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 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 */
                   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 ALSO

     ioctl(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 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.

NetBSD 10.1                       May 4, 2021                      NetBSD 10.1