.\" Copyright (c) 1998, Nicolas Souchu
.\" All rights reserved.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\"    notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\"    notice, this list of conditions and the following disclaimer in the
.\"    documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
.\" ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
.\" SUCH DAMAGE.
.\"
.\" $FreeBSD: src/share/man/man4/smbus.4,v 1.9.2.3 2001/08/17 13:08:39 ru Exp $
.\" $DragonFly: src/share/man/man4/smbus.4,v 1.2 2003/06/17 04:36:59 dillon Exp $
.\"
.Dd August 10, 1998
.Dt SMBUS 4
.Os
.Sh NAME
.Nm smbus
.Nd System Management Bus
.Sh SYNOPSIS
.Cd "device smbus"
.Pp
.Cd "device iicsmb"
.Cd "device bktr"
.Sh DESCRIPTION
The
.Em smbus
system provides a uniform, modular and architecture-independent
system for the implementation of drivers to control various SMB devices
and to utilize different SMB controllers (I2C, PIIX4, Brooktree848, vm86...).
.Sh System Management Bus
The
.Em System Management Bus
is a two-wire interface through which simple power-related chips can communicate
with rest of the system.
It uses I2C as its backbone (see
.Xr iicbus 4 ) .
.Pp
A system using SMB passes messages to and from devices instead of tripping
individual control lines.
.Pp
With the SMBus, a device can provide manufacturer information, tell the
system what its model/part number is, save its state for a suspend event,
report different types of errors, accept control parameters, and return its
status.
.Pp
The SMBus may share the same host device and physical bus as ACCESS bus
components provided that an appropriate electrical bridge is provided
between the internal SMB devices and external ACCESS bus devices.
.Sh SEE ALSO
.Xr bktr 4 ,
.Xr iicbus 4 ,
.Xr iicsmb 4 ,
.Xr smb 4
.Sh HISTORY
The
.Nm
manual page first appeared in
.Fx 3.0 .
.Sh AUTHORS
This
manual page was written by
.An Nicolas Souchu .