Add support for IPMB driver

Support receiving IPMB requests on a Satellite MC from the BMC.
Once a response is ready, this driver will send back a response
to the BMC via the IPMB channel.

Signed-off-by: Asmaa Mnebhi <Asmaa@mellanox.com>
Acked-by: vadimp@mellanox.com
Message-Id: <319690553a0da2a1e80b400941341081b383e5f1.1560192707.git.Asmaa@mellanox.com>
[Move the config option to outside the ipmi msghandler, as it's not
 dependent on that.  Fixed one small whitespace issue.]
Signed-off-by: Corey Minyard <cminyard@mvista.com>

Documentation/IPMB.txt

@@ -0,0 +1,103 @@
+==============================
+IPMB Driver for a Satellite MC
+==============================
+
+The Intelligent Platform Management Bus or IPMB, is an
+I2C bus that provides a standardized interconnection between
+different boards within a chassis. This interconnection is
+between the baseboard management (BMC) and chassis electronics.
+IPMB is also associated with the messaging protocol through the
+IPMB bus.
+
+The devices using the IPMB are usually management
+controllers that perform management functions such as servicing
+the front panel interface, monitoring the baseboard,
+hot-swapping disk drivers in the system chassis, etc...
+
+When an IPMB is implemented in the system, the BMC serves as
+a controller to give system software access to the IPMB. The BMC
+sends IPMI requests to a device (usually a Satellite Management
+Controller or Satellite MC) via IPMB and the device
+sends a response back to the BMC.
+
+For more information on IPMB and the format of an IPMB message,
+refer to the IPMB and IPMI specifications.
+
+IPMB driver for Satellite MC
+----------------------------
+
+ipmb-dev-int - This is the driver needed on a Satellite MC to
+receive IPMB messages from a BMC and send a response back.
+This driver works with the I2C driver and a userspace
+program such as OpenIPMI:
+
+1) It is an I2C slave backend driver. So, it defines a callback
+function to set the Satellite MC as an I2C slave.
+This callback function handles the received IPMI requests.
+
+2) It defines the read and write functions to enable a user
+space program (such as OpenIPMI) to communicate with the kernel.
+
+
+Load the IPMB driver
+--------------------
+
+The driver needs to be loaded at boot time or manually first.
+First, make sure you have the following in your config file:
+CONFIG_IPMB_DEVICE_INTERFACE=y
+
+1) If you want the driver to be loaded at boot time:
+
+a) Add this entry to your ACPI table, under the appropriate SMBus:
+
+Device (SMB0) // Example SMBus host controller
+{
+  Name (_HID, "<Vendor-Specific HID>") // Vendor-Specific HID
+  Name (_UID, 0) // Unique ID of particular host controller
+  :
+  :
+    Device (IPMB)
+    {
+      Name (_HID, "IPMB0001") // IPMB device interface
+      Name (_UID, 0) // Unique device identifier
+    }
+}
+
+b) Example for device tree:
+
+&i2c2 {
+         status = "okay";
+
+         ipmb@10 {
+                 compatible = "ipmb-dev";
+                 reg = <0x10>;
+         };
+};
+
+2) Manually from Linux:
+modprobe ipmb-dev-int
+
+
+Instantiate the device
+----------------------
+
+After loading the driver, you can instantiate the device as
+described in 'Documentation/i2c/instantiating-devices'.
+If you have multiple BMCs, each connected to your Satellite MC via
+a different I2C bus, you can instantiate a device for each of
+those BMCs.
+The name of the instantiated device contains the I2C bus number
+associated with it as follows:
+
+BMC1 ------ IPMB/I2C bus 1 ---------|   /dev/ipmb-1
+				Satellite MC
+BMC1 ------ IPMB/I2C bus 2 ---------|   /dev/ipmb-2
+
+For instance, you can instantiate the ipmb-dev-int device from
+user space at the 7 bit address 0x10 on bus 2:
+
+  # echo ipmb-dev 0x1010 > /sys/bus/i2c/devices/i2c-2/new_device
+
+This will create the device file /dev/ipmb-2, which can be accessed
+by the user space program. The device needs to be instantiated
+before running the user space program.

drivers/char/ipmi/Kconfig

@@ -131,3 +131,11 @@ config ASPEED_BT_IPMI_BMC
 	  Provides a driver for the BT (Block Transfer) IPMI interface
 	  found on Aspeed SOCs (AST2400 and AST2500). The driver
 	  implements the BMC side of the BT interface.
+
+config IPMB_DEVICE_INTERFACE
+	tristate 'IPMB Interface handler'
+	depends on I2C_SLAVE
+	help
+	  Provides a driver for a device (Satellite MC) to
+	  receive requests and send responses back to the BMC via
+	  the IPMB interface. This module requires I2C support.

drivers/char/ipmi/Makefile

@@ -26,3 +26,4 @@ obj-$(CONFIG_IPMI_KCS_BMC) += kcs_bmc.o
 obj-$(CONFIG_ASPEED_BT_IPMI_BMC) += bt-bmc.o
 obj-$(CONFIG_ASPEED_KCS_IPMI_BMC) += kcs_bmc_aspeed.o
 obj-$(CONFIG_NPCM7XX_KCS_IPMI_BMC) += kcs_bmc_npcm7xx.o
+obj-$(CONFIG_IPMB_DEVICE_INTERFACE) += ipmb_dev_int.o