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1==============================2IPMB Driver for a Satellite MC3==============================4 5The Intelligent Platform Management Bus or IPMB, is an6I2C bus that provides a standardized interconnection between7different boards within a chassis. This interconnection is8between the baseboard management (BMC) and chassis electronics.9IPMB is also associated with the messaging protocol through the10IPMB bus.11 12The devices using the IPMB are usually management13controllers that perform management functions such as servicing14the 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 as18a controller to give system software access to the IPMB. The BMC19sends IPMI requests to a device (usually a Satellite Management20Controller or Satellite MC) via IPMB and the device21sends 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 MC27----------------------------28 29ipmb-dev-int - This is the driver needed on a Satellite MC to30receive IPMB messages from a BMC and send a response back.31This driver works with the I2C driver and a userspace32program such as OpenIPMI:33 341) It is an I2C slave backend driver. So, it defines a callback35 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 user39 space program (such as OpenIPMI) to communicate with the kernel.40 41 42Load the IPMB driver43--------------------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=y48 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 controller54 {55 Name (_HID, "<Vendor-Specific HID>") // Vendor-Specific HID56 Name (_UID, 0) // Unique ID of particular host controller57 :58 :59 Device (IPMB)60 {61 Name (_HID, "IPMB0001") // IPMB device interface62 Name (_UID, 0) // Unique device identifier63 }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 smbus79then "i2c-protocol" needs to be defined as above.80 812) Manually from Linux::82 83 modprobe ipmb-dev-int84 85 86Instantiate the device87----------------------88 89After loading the driver, you can instantiate the device as90described in 'Documentation/i2c/instantiating-devices.rst'.91If you have multiple BMCs, each connected to your Satellite MC via92a different I2C bus, you can instantiate a device for each of93those BMCs.94 95The name of the instantiated device contains the I2C bus number96associated with it as follows::97 98 BMC1 ------ IPMB/I2C bus 1 ---------| /dev/ipmb-199 Satellite MC100 BMC1 ------ IPMB/I2C bus 2 ---------| /dev/ipmb-2101 102For instance, you can instantiate the ipmb-dev-int device from103user space at the 7 bit address 0x10 on bus 2::104 105 # echo ipmb-dev 0x1010 > /sys/bus/i2c/devices/i2c-2/new_device106 107This will create the device file /dev/ipmb-2, which can be accessed108by the user space program. The device needs to be instantiated109before running the user space program.110