---
name: "smbus"
section: "4"
platform: "freebsd"
package: "base"
version: "16.0-CURRENT-20261027-61c70dc16a79"
release: "FreeBSD 16.0-CURRENT (2026-10-27)"
platforms: ["linux", "freebsd"]
url: "https://new.carta.tech/smbus"
---

# smbus(4)

System Management Bus

## NAME

**smbus** – System Management Bus

## SYNOPSIS

**device smbus**

**device iicsmb**

## DESCRIPTION

The *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, vm86...).

## System Management Bus

The *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 [iicbus(4)](/iicbus/4.md)).

A system using SMB passes messages to and from devices instead of tripping individual control lines.

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.

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.

## SEE ALSO

[iicbus(4)](/iicbus/4.md), [iicsmb(4)](/iicsmb/4.md), [smb(4)](/smb/4.md), [smbmsg(8)](/smbmsg/8.md) *The SMBus specification*, https://www.smbus.org/specs/.

## HISTORY

The **smbus** manual page first appeared in FreeBSD 3.0.

## AUTHORS

This manual page was written by Nicolas Souchu.