xref: /linux/Documentation/driver-api/ipmb.rst (revision 2da68a77) 
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                    i2c-protocol;
75            };
76     };
77
78If xmit of data to be done using raw i2c block vs smbus
79then "i2c-protocol" needs to be defined as above.
80
812) Manually from Linux::
82
83     modprobe ipmb-dev-int
84
85
86Instantiate the device
87----------------------
88
89After loading the driver, you can instantiate the device as
90described in 'Documentation/i2c/instantiating-devices.rst'.
91If you have multiple BMCs, each connected to your Satellite MC via
92a different I2C bus, you can instantiate a device for each of
93those BMCs.
94
95The name of the instantiated device contains the I2C bus number
96associated with it as follows::
97
98  BMC1 ------ IPMB/I2C bus 1 ---------|   /dev/ipmb-1
99				Satellite MC
100  BMC1 ------ IPMB/I2C bus 2 ---------|   /dev/ipmb-2
101
102For instance, you can instantiate the ipmb-dev-int device from
103user space at the 7 bit address 0x10 on bus 2::
104
105  # echo ipmb-dev 0x1010 > /sys/bus/i2c/devices/i2c-2/new_device
106
107This will create the device file /dev/ipmb-2, which can be accessed
108by the user space program. The device needs to be instantiated
109before running the user space program.
110