man/man4/gpio.4

.\" $NetBSD: gpio.4,v 1.38 2024/12/16 16:42:22 brad Exp $
.\"	$OpenBSD: gpio.4,v 1.5 2004/11/23 09:39:29 reyk Exp $
.\"
.\" 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 May 4, 2021
.Dt GPIO 4
.Os
.Sh NAME
.Nm gpio
.Nd General Purpose Input/Output
.Sh SYNOPSIS
.Cd "gpio* at elansc?"
.Cd "gpio* at epgpio?"
.Cd "gpio* at gcscpcib?"
.Cd "gpio* at gpiosim?"
.Cd "gpio* at gscpcib?"
.Cd "gpio* at ichlpcib?"
.Cd "gpio* at nsclpcsio?"
.Cd "gpio* at soekrisgpio?"
.Cd "gpio* at ppbus?"
.Cd "gpio* at ptcd?"
.Cd "gpio* at umcpmio?"
.Cd "gpio* at wbsio?"
.Pp
.In sys/types.h
.In sys/gpio.h
.In sys/ioctl.h
.Sh DESCRIPTION
The
.Nm
device attaches to the GPIO controller and provides a uniform
programming interface to its pins.
.Pp
Each GPIO controller with an attached
.Nm
device has an associated device file under the
.Pa /dev
directory, e.g.\&
.Pa /dev/gpio0 .
Access from userland is performed through
.Xr ioctl 2
calls on these devices.
.Pp
Whether the layout of the GPIO device can be configured is subject to
authorization by the
.Xr kauth 9
framework.
.Pp
If for example
.Xr 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
.Nm
device at a securelevel less than 1.
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
.In sys/gpio.h
header file:
.Pp
.Bl -tag -width XXXX -compact
.It Dv GPIOINFO ( struct gpio_info )
Returns information about the GPIO controller in the
.Fa gpio_info
structure:
.Bd -literal
struct gpio_info {
	int gpio_npins;		/* total number of pins available */
};
.Ed
.Pp
.It Dv GPIOREAD ( struct gpio_req )
Returns the input pin value in the
.Fa gpio_req
structure:
.Bd -literal
#define GPIOMAXNAME		64

struct gpio_req {
	char gp_name[GPIOMAXNAME];	/* pin name */
	int gp_pin;			/* pin number */
	int gp_value;			/* value */
};
.Ed
.Pp
The
.Fa gp_name
or
.Fa gp_pin
field must be set before calling.
If both are set, gp_name takes precedence.
On return, the
.Fa gp_name
field contains the current name of the pin, if set by the controller driver
or an earlier call to
.Dv GPIOSET .
.Pp
.It Dv GPIOWRITE ( struct gpio_req )
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.
.Pp
.It Dv GPIOTOGGLE ( struct gpio_req )
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.
.Pp
.It Dv GPIOSET ( struct gpio_set )
Changes pin configuration flags with the new ones provided in the
.Fa gpio_set
structure:
.Bd -literal
#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 */
};
.Ed
.Pp
The
.Fa gp_flags
field is a combination of the following flags:
.Pp
.Bl -tag -width GPIO_PIN_OPENDRAIN -compact
.It Dv GPIO_PIN_INPUT
input direction
.It Dv GPIO_PIN_OUTPUT
output direction
.It Dv GPIO_PIN_INOUT
bi-directional
.It Dv GPIO_PIN_OPENDRAIN
open-drain output
.It Dv GPIO_PIN_PUSHPULL
push-pull output
.It Dv GPIO_PIN_TRISTATE
output disabled
.It Dv GPIO_PIN_PULLUP
internal pull-up enabled
.It Dv GPIO_PIN_PULLDOWN
internal pull-down enabled
.It Dv GPIO_PIN_INVIN
invert input
.It Dv GPIO_PIN_INVOUT
invert output
.It Dv GPIO_PIN_PULSATE
pulsate output
.It Dv GPIO_PIN_ALT0 -
.It Dv GPIO_PIN_ALT7
select alternate pin function 0 to 7
.El
.Pp
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.
.Pp
Only GPIO pins that have been set using
.Ar GPIOSET
will be accessible at securelevels greater than 0.
.Pp
.It Dv GPIOUNSET ( struct gpio_set )
Unset the specified pin, i.e. clear its name and make it inaccessible
at securelevels greater than 0.
.Pp
.It Dv GPIOATTACH ( struct gpio_attach )
Attach the device described in the
.Fa gpio_attach
structure on this gpio device.
.Bd -literal
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 */
};
.Ed
.Pp
The
.Xr drvctl 8
command can be used to detach a device from a gpio pin.
.El
.Sh FILES
.Bl -tag -width "/dev/gpiou" -compact
.It /dev/gpio Ns Ar u
GPIO device unit
.Ar u
file.
.El
.Sh SEE ALSO
.Xr ioctl 2 ,
.Xr drvctl 8 ,
.Xr gpioctl 8
.Sh HISTORY
The
.Nm
device first appeared in
.Ox 3.6
and
.Nx 4.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Alexander Yurchenko Aq Mt grange@openbsd.org .
.Nm
was ported to
.Nx
by
.An Jared D. McNeill Aq Mt jmcneill@NetBSD.org .
Runtime device attachment was added by
.An Marc Balmer Aq Mt marc@msys.ch .
.Sh BUGS
Event capabilities are not supported.