Intelligent Platform Management Bus (IPMB) Device Driver

This is a linux driver for sending IPMI messages (requests and responses) over the IPMB bus.

Example Applications:

• Satellite MC that needs to be able to send IPMI requests
• BMC
• VITA 46.11 Chassis Manager
• VITA 46.11 Tier-2 IPMC

Table of Contents

• Intelligent Platform Management Bus (IPMB) Device Driver
  • Motivation
  • Requirements
  • Usage
  • Credits

Motivation

Currently, the mainline linux kernel doesn't have any drivers that can support sending both requests and responses over IPMB . The i2c-dev driver exposes the i2c bus to userspace, but only supports master i2c transactions. The ipmb-dev-int driver (intended for use in a satellite IPMC) is limited to receiving requests/sending responses. This driver is a modified version of the ipmb-dev-int driver that supports both sides of the IPMI transaction (requester and responder).

Requirements

• Linux kernel version 4.13 or higher.
• Kconfig
  • enable CONFIG_I2C_SLAVE
  • disable CONFIG_IPMB_DEVICE_INTERFACE
• I2C bus driver must support multimaster operation.

Usage

1. Add nodes to the device tree for each IPMB bus and specify the IPMI address (slave address) to use. (See the device_tree.dts.sample file for an example)
2. The /dev/ipmb-<i2c-bus-num> device can be used to read and write IPMB messages on an i2c bus.
   • read() will receive one message per call.
   • write() will write one message per call to the address in the message header.
3. ioctl() can be used to enable/disable optional functionality (see ipmb_device.h).
4. Consider using the select system call, boost.asio, or libevent to receive messages asynchronously.

(See the usage.c.sample for a simple example of using this driver to send an IPMB msg)

This is a relatively bare-bones implementation that doesn't make many assumptions about the structure of the underlying IPMI messages. Apart from extracting the destination address from the message header and optionally validating the header checksum (see ioctl interface), this driver simply exposes the raw i2c bus to userspace. The user is responsible for (de)serialization, validation, timeouts and retry logic, etc.

Credits

This is based on Mellanox's ipmb_dev_int driver in the mainline linux kernel.