.\"	$NetBSD: gpioiic.4,v 1.6 2014/03/18 18:20:39 riastradh Exp $
.\"	$OpenBSD: gpioiic.4,v 1.6 2008/11/24 15:30:21 jmc Exp $
.\"
.\" Copyright (c) 2006 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 October 2, 2011
.Dt GPIOIIC 4
.Os
.Sh NAME
.Nm gpioiic
.Nd GPIO I2C controller
.Sh SYNOPSIS
.Cd "gpioiic* at gpio? offset 0 mask 0x3 flag 0x0"
.Cd "gpioiic* at gpio?"
.Cd "iic* at gpioiic?"
.Sh DESCRIPTION
The
.Nm
driver allows bit-banging an I2C bus as a master using two GPIO pins.
By default the first pin is used as a serial data (SDA) signal and the
second as a serial clock (SCL).
If the flag locator is set to 0x01, the order of the SDA and SCL signals
is reversed.
Both GPIO pins must be able to drive an output and the SDA pin must be
also able to read an input.
.Pp
The pins can be specified in the kernel configuration with the
.Ar offset
and the
.Ar mask
locators.
The
.Ar offset
and
.Ar mask
can also be specified when
.Nm
is attached at runtime using the
.Dv GPIOATTACH
.Xr ioctl 2
on the
.Xr gpio 4
device.
Each bit in the
.Ar mask
locator defines one pin; the pin number is calculated as an addition of
the bit position and the
.Ar offset
locator.
For example,
.Ar offset 17
and
.Ar mask 0x5
defines pin numbers 17 and 19.
.Sh SEE ALSO
.Xr gpio 4 ,
.Xr iic 4 ,
.Xr intro 4
.Sh HISTORY
The
.Nm
driver first appeared in
.Ox 3.9
and
.Nx 5.0 .
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Alexander Yurchenko Aq Mt grange@openbsd.org
and was ported to
.Nx
by
.An Marc Balmer Aq Mt marc@msys.ch .
.Sh CAVEATS
A
.Nm
device can not be detached from the
.Xr gpio 4
bus at runtime due to the fact that
.Xr iic 4
busses can not detach once attached.