1==============================
  2IPMB Driver for a Satellite MC
  3==============================
  4
  5The Intelligent Platform Management Bus or IPMB, is an
  6I2C bus that provides a standardized interconnection between
  7different boards within a chassis. This interconnection is
  8between the baseboard management (BMC) and chassis electronics.
  9IPMB is also associated with the messaging protocol through the
 10IPMB bus.
 11
 12The devices using the IPMB are usually management
 13controllers that perform management functions such as servicing
 14the front panel interface, monitoring the baseboard,
 15hot-swapping disk drivers in the system chassis, etc...
 16
 17When an IPMB is implemented in the system, the BMC serves as
 18a controller to give system software access to the IPMB. The BMC
 19sends IPMI requests to a device (usually a Satellite Management
 20Controller or Satellite MC) via IPMB and the device
 21sends a response back to the BMC.
 22
 23For more information on IPMB and the format of an IPMB message,
 24refer to the IPMB and IPMI specifications.
 25
 26IPMB driver for Satellite MC
 27----------------------------
 28
 29ipmb-dev-int - This is the driver needed on a Satellite MC to
 30receive IPMB messages from a BMC and send a response back.
 31This driver works with the I2C driver and a userspace
 32program such as OpenIPMI:
 33
 341) It is an I2C slave backend driver. So, it defines a callback
 35   function to set the Satellite MC as an I2C slave.
 36   This callback function handles the received IPMI requests.
 37
 382) It defines the read and write functions to enable a user
 39   space program (such as OpenIPMI) to communicate with the kernel.
 40
 41
 42Load the IPMB driver
 43--------------------
 44
 45The driver needs to be loaded at boot time or manually first.
 46First, make sure you have the following in your config file:
 47CONFIG_IPMB_DEVICE_INTERFACE=y
 48
 491) If you want the driver to be loaded at boot time:
 50
 51a) Add this entry to your ACPI table, under the appropriate SMBus::
 52
 53     Device (SMB0) // Example SMBus host controller
 54     {
 55     Name (_HID, "<Vendor-Specific HID>") // Vendor-Specific HID
 56     Name (_UID, 0) // Unique ID of particular host controller
 57     :
 58     :
 59       Device (IPMB)
 60       {
 61         Name (_HID, "IPMB0001") // IPMB device interface
 62         Name (_UID, 0) // Unique device identifier
 63       }
 64     }
 65
 66b) Example for device tree::
 67
 68     &i2c2 {
 69            status = "okay";
 70
 71            ipmb@10 {
 72                    compatible = "ipmb-dev";
 73                    reg = <0x10>;
 74            };
 75     };
 76
 772) Manually from Linux::
 78
 79     modprobe ipmb-dev-int
 80
 81
 82Instantiate the device
 83----------------------
 84
 85After loading the driver, you can instantiate the device as
 86described in 'Documentation/i2c/instantiating-devices.rst'.
 87If you have multiple BMCs, each connected to your Satellite MC via
 88a different I2C bus, you can instantiate a device for each of
 89those BMCs.
 90
 91The name of the instantiated device contains the I2C bus number
 92associated with it as follows::
 93
 94  BMC1 ------ IPMB/I2C bus 1 ---------|   /dev/ipmb-1
 95				Satellite MC
 96  BMC1 ------ IPMB/I2C bus 2 ---------|   /dev/ipmb-2
 97
 98For instance, you can instantiate the ipmb-dev-int device from
 99user space at the 7 bit address 0x10 on bus 2::
100
101  # echo ipmb-dev 0x1010 > /sys/bus/i2c/devices/i2c-2/new_device
102
103This will create the device file /dev/ipmb-2, which can be accessed
104by the user space program. The device needs to be instantiated
105before running the user space program.