Copyright (c) 2004 Alexander Yurchenko <grange@openbsd.org>
Permission to use, copy, modify, and distribute this software for any
purpose with or without fee is hereby granted, provided that the above
copyright notice and this permission notice appear in all copies.
THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
.Dd $Mdocdate: February 18 2022 $ .Dt GPIO 4 .Os .Sh NAME .Nm gpio .Nd General Purpose Input/Output .Sh SYNOPSIS .Cd "gpio* at ath?" .Cd "gpio* at bcmgpio?" Pq arm64, armv7 .Cd "gpio* at glxpcib?" Pq i386 .Cd "gpio* at gscpcib?" Pq i386 .Cd "gpio* at isagpio?" .Cd "gpio* at mpfgpio?" Pq riscv64 .Cd "gpio* at nsclpcsio?" .Cd "gpio* at omgpio?" Pq armv7 .Cd "gpio* at pcagpio?" .Cd "gpio* at pcaled?" .Cd "gpio* at skgpio?" Pq amd64, i386 .Cd "gpio* at sxipio?" Pq arm64, armv7 .Cd "gpio0 at voyager?" Pq loongson
p n sys/types.h n sys/gpio.h n sys/ioctl.h .Sh DESCRIPTION The .Nm device attaches to the GPIO controller and provides a uniform programming interface to its pins.
p Each GPIO controller with an attached .Nm device has an associated device file under the
a /dev directory, e.g.\&
a /dev/gpio0 . Access from userland is performed through .Xr ioctl 2 calls on these devices.
p 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 .Nm device at securelevel 0. All other pins will not be accessible once the runlevel has been raised. .Sh IOCTL INTERFACE The following structures and constants are defined in the n sys/gpio.h header file: l -tag -width XXXX t Dv GPIOINFO Fa "struct gpio_info" Returns information about the GPIO controller in the .Fa gpio_info structure: d -literal struct gpio_info { int gpio_npins; /* total number of pins available */ }; .Ed t Dv GPIOPINREAD Fa "struct gpio_pin_op" Returns the input pin value in the .Fa gpio_pin_op structure: d -literal #define GPIOPINMAXNAME 64 struct gpio_pin_op { char gp_name[GPIOPINMAXNAME]; /* pin name */ int gp_pin; /* pin number */ int gp_value; /* value */ }; .Ed
p The .Fa gp_name or .Fa gp_pin field must be set before calling. t Dv GPIOPINWRITE Fa "struct gpio_pin_op" Writes the output value to the pin. The value set in the .Fa gp_value field must be either .Dv GPIO_PIN_LOW (logical 0) or .Dv GPIO_PIN_HIGH (logical 1). On return, the .Fa gp_value field contains the old pin state. t Dv GPIOPINTOGGLE Fa "struct gpio_pin_op" Toggles the pin output value, i.e. changes it to the opposite. .Fa gp_value field is ignored and on return contains the old pin state. t Dv GPIOPINSET Fa "struct gpio_pin_set" Changes pin configuration flags with the new ones provided in the .Fa gpio_pin_set structure: d -literal #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 */ }; .Ed
p The .Fa gp_flags field is a combination of the following flags:
p l -tag -width GPIO_PIN_OPENDRAIN -compact t Dv GPIO_PIN_INPUT input direction t Dv GPIO_PIN_OUTPUT output direction t Dv GPIO_PIN_INOUT bi-directional t Dv GPIO_PIN_OPENDRAIN open-drain output t Dv GPIO_PIN_PUSHPULL push-pull output t Dv GPIO_PIN_TRISTATE output disabled t Dv GPIO_PIN_PULLUP internal pull-up enabled t Dv GPIO_PIN_PULLDOWN internal pull-down enabled t Dv GPIO_PIN_INVIN invert input t Dv GPIO_PIN_INVOUT invert output .El
p Note that the GPIO controller may not support all of these flags. On return the .Fa gp_caps field contains flags that are supported. If no flags are specified, the pin configuration stays unchanged.
p Only GPIO pins that have been set using .Ar GPIOPINSET will be accessible at securelevels greater than 0. t Dv GPIOPINUNSET Fa "struct gpio_pin_set" Unset the specified pin, i.e. clear its name and make it inaccessible at securelevels greater than 0. t Dv GPIOATTACH Fa "struct gpio_attach" Attach the device described in the .Fa gpio_attach structure on this gpio device. d -literal struct gpio_attach { char ga_dvname[16]; /* device name */ int ga_offset; /* pin number */ u_int32_t ga_mask; /* binary mask */ }; .Ed t Dv GPIODETACH Fa "struct gpio_attach" Detach a device from this gpio device that was previously attached using the .Dv GPIOATTACH .Xr ioctl 2 . The .Fa ga_offset and .Fa ga_mask fields of the .Fa gpio_attach structure are ignored. .El .Sh FILES l -tag -width "/dev/gpiou" -compact t /dev/gpio Ns Ar u GPIO device unit .Ar u file. .El .Sh SEE ALSO .Xr ioctl 2 , .Xr gpioctl 8 .Sh HISTORY The .Nm device first appeared in .Ox 3.6 . .Sh AUTHORS .An -nosplit The .Nm driver was written by .An Alexander Yurchenko Aq Mt grange@openbsd.org . Runtime device attachment was added by .An Marc Balmer Aq Mt mbalmer@openbsd.org . .Sh BUGS Event capabilities are not supported.