diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 3f3489c..a0c0365 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -209,6 +209,17 @@ config ACPI_PROCESSOR
 
 	  To compile this driver as a module, choose M here:
 	  the module will be called processor.
+config ACPI_IPMI
+	tristate "IPMI"
+	depends on EXPERIMENTAL && IPMI_SI && IPMI_HANDLER
+	default n
+	help
+	  This driver enables the ACPI to access the BMC controller. And it
+	  uses the IPMI request/response message to communicate with BMC
+	  controller, which can be found on on the server.
+
+	  To compile this driver as a module, choose M here:
+	  the module will be called as acpi_ipmi.
 
 config ACPI_HOTPLUG_CPU
 	bool
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 3d031d0..df4c4f0 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -69,5 +69,6 @@ processor-y			+= processor_idle.o processor_thermal.o
 processor-$(CONFIG_CPU_FREQ)	+= processor_perflib.o
 
 obj-$(CONFIG_ACPI_PROCESSOR_AGGREGATOR) += acpi_pad.o
+obj-$(CONFIG_ACPI_IPMI)		+= acpi_ipmi.o
 
 obj-$(CONFIG_ACPI_APEI)		+= apei/
diff --git a/drivers/acpi/acpi_ipmi.c b/drivers/acpi/acpi_ipmi.c
new file mode 100644
index 0000000..f40acef
--- /dev/null
+++ b/drivers/acpi/acpi_ipmi.c
@@ -0,0 +1,525 @@
+/*
+ *  acpi_ipmi.c - ACPI IPMI opregion
+ *
+ *  Copyright (C) 2010 Intel Corporation
+ *  Copyright (C) 2010 Zhao Yakui <yakui.zhao@intel.com>
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation; either version 2 of the License, or (at
+ *  your option) any later version.
+ *
+ *  This program is distributed in the hope that it will be useful, but
+ *  WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ *  General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place, Suite 330, Boston, MA 02111-1307 USA.
+ *
+ * ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+ */
+
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/init.h>
+#include <linux/types.h>
+#include <linux/delay.h>
+#include <linux/proc_fs.h>
+#include <linux/seq_file.h>
+#include <linux/interrupt.h>
+#include <linux/list.h>
+#include <linux/spinlock.h>
+#include <linux/io.h>
+#include <acpi/acpi_bus.h>
+#include <acpi/acpi_drivers.h>
+#include <linux/ipmi.h>
+#include <linux/device.h>
+#include <linux/pnp.h>
+
+MODULE_AUTHOR("Zhao Yakui");
+MODULE_DESCRIPTION("ACPI IPMI Opregion driver");
+MODULE_LICENSE("GPL");
+
+#define IPMI_FLAGS_HANDLER_INSTALL	0
+
+#define ACPI_IPMI_OK			0
+#define ACPI_IPMI_TIMEOUT		0x10
+#define ACPI_IPMI_UNKNOWN		0x07
+/* the IPMI timeout is 5s */
+#define IPMI_TIMEOUT			(5 * HZ)
+
+struct acpi_ipmi_device {
+	/* the device list attached to driver_data.ipmi_devices */
+	struct list_head head;
+	/* the IPMI request message list */
+	struct list_head tx_msg_list;
+	struct mutex	tx_msg_lock;
+	acpi_handle handle;
+	struct pnp_dev *pnp_dev;
+	ipmi_user_t	user_interface;
+	int ipmi_ifnum; /* IPMI interface number */
+	long curr_msgid;
+	unsigned long flags;
+	struct ipmi_smi_info smi_data;
+};
+
+struct ipmi_driver_data {
+	struct list_head	ipmi_devices;
+	struct ipmi_smi_watcher	bmc_events;
+	struct ipmi_user_hndl	ipmi_hndlrs;
+	struct mutex		ipmi_lock;
+};
+
+struct acpi_ipmi_msg {
+	struct list_head head;
+	/*
+	 * General speaking the addr type should be SI_ADDR_TYPE. And
+	 * the addr channel should be BMC.
+	 * In fact it can also be IPMB type. But we will have to
+	 * parse it from the Netfn command buffer. It is so complex
+	 * that it is skipped.
+	 */
+	struct ipmi_addr addr;
+	long tx_msgid;
+	/* it is used to track whether the IPMI message is finished */
+	struct completion tx_complete;
+	struct kernel_ipmi_msg tx_message;
+	int	msg_done;
+	/* tx data . And copy it from ACPI object buffer */
+	u8	tx_data[64];
+	int	tx_len;
+	u8	rx_data[64];
+	int	rx_len;
+	struct acpi_ipmi_device *device;
+};
+
+/* IPMI request/response buffer per ACPI 4.0, sec 5.5.2.4.3.2 */
+struct acpi_ipmi_buffer {
+	u8 status;
+	u8 length;
+	u8 data[64];
+};
+
+static void ipmi_register_bmc(int iface, struct device *dev);
+static void ipmi_bmc_gone(int iface);
+static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data);
+static void acpi_add_ipmi_device(struct acpi_ipmi_device *ipmi_device);
+static void acpi_remove_ipmi_device(struct acpi_ipmi_device *ipmi_device);
+
+static struct ipmi_driver_data driver_data = {
+	.ipmi_devices = LIST_HEAD_INIT(driver_data.ipmi_devices),
+	.bmc_events = {
+		.owner = THIS_MODULE,
+		.new_smi = ipmi_register_bmc,
+		.smi_gone = ipmi_bmc_gone,
+	},
+	.ipmi_hndlrs = {
+		.ipmi_recv_hndl = ipmi_msg_handler,
+	},
+};
+
+static struct acpi_ipmi_msg *acpi_alloc_ipmi_msg(struct acpi_ipmi_device *ipmi)
+{
+	struct acpi_ipmi_msg *ipmi_msg;
+	struct pnp_dev *pnp_dev = ipmi->pnp_dev;
+
+	ipmi_msg = kzalloc(sizeof(struct acpi_ipmi_msg), GFP_KERNEL);
+	if (!ipmi_msg)	{
+		dev_warn(&pnp_dev->dev, "Can't allocate memory for ipmi_msg\n");
+		return NULL;
+	}
+	init_completion(&ipmi_msg->tx_complete);
+	INIT_LIST_HEAD(&ipmi_msg->head);
+	ipmi_msg->device = ipmi;
+	return ipmi_msg;
+}
+
+#define		IPMI_OP_RGN_NETFN(offset)	((offset >> 8) & 0xff)
+#define		IPMI_OP_RGN_CMD(offset)		(offset & 0xff)
+static void acpi_format_ipmi_msg(struct acpi_ipmi_msg *tx_msg,
+				acpi_physical_address address,
+				acpi_integer *value)
+{
+	struct kernel_ipmi_msg *msg;
+	struct acpi_ipmi_buffer *buffer;
+	struct acpi_ipmi_device *device;
+
+	msg = &tx_msg->tx_message;
+	/*
+	 * IPMI network function and command are encoded in the address
+	 * within the IPMI OpRegion; see ACPI 4.0, sec 5.5.2.4.3.
+	 */
+	msg->netfn = IPMI_OP_RGN_NETFN(address);
+	msg->cmd = IPMI_OP_RGN_CMD(address);
+	msg->data = tx_msg->tx_data;
+	/*
+	 * value is the parameter passed by the IPMI opregion space handler.
+	 * It points to the IPMI request message buffer
+	 */
+	buffer = (struct acpi_ipmi_buffer *)value;
+	/* copy the tx message data */
+	msg->data_len = buffer->length;
+	memcpy(tx_msg->tx_data, buffer->data, msg->data_len);
+	/*
+	 * now the default type is SYSTEM_INTERFACE and channel type is BMC.
+	 * If the netfn is APP_REQUEST and the cmd is SEND_MESSAGE,
+	 * the addr type should be changed to IPMB. Then we will have to parse
+	 * the IPMI request message buffer to get the IPMB address.
+	 * If so, please fix me.
+	 */
+	tx_msg->addr.addr_type = IPMI_SYSTEM_INTERFACE_ADDR_TYPE;
+	tx_msg->addr.channel = IPMI_BMC_CHANNEL;
+	tx_msg->addr.data[0] = 0;
+
+	/* Get the msgid */
+	device = tx_msg->device;
+	mutex_lock(&device->tx_msg_lock);
+	device->curr_msgid++;
+	tx_msg->tx_msgid = device->curr_msgid;
+	mutex_unlock(&device->tx_msg_lock);
+}
+
+static void acpi_format_ipmi_response(struct acpi_ipmi_msg *msg,
+		acpi_integer *value, int rem_time)
+{
+	struct acpi_ipmi_buffer *buffer;
+
+	/*
+	 * value is also used as output parameter. It represents the response
+	 * IPMI message returned by IPMI command.
+	 */
+	buffer = (struct acpi_ipmi_buffer *)value;
+	if (!rem_time && !msg->msg_done) {
+		buffer->status = ACPI_IPMI_TIMEOUT;
+		return;
+	}
+	/*
+	 * If the flag of msg_done is not set or the recv length is zero, it
+	 * means that the IPMI command is not executed correctly.
+	 * The status code will be ACPI_IPMI_UNKNOWN.
+	 */
+	if (!msg->msg_done || !msg->rx_len) {
+		buffer->status = ACPI_IPMI_UNKNOWN;
+		return;
+	}
+	/*
+	 * If the IPMI response message is obtained correctly, the status code
+	 * will be ACPI_IPMI_OK
+	 */
+	buffer->status = ACPI_IPMI_OK;
+	buffer->length = msg->rx_len;
+	memcpy(buffer->data, msg->rx_data, msg->rx_len);
+}
+
+static void ipmi_flush_tx_msg(struct acpi_ipmi_device *ipmi)
+{
+	struct acpi_ipmi_msg *tx_msg, *temp;
+	int count = HZ / 10;
+	struct pnp_dev *pnp_dev = ipmi->pnp_dev;
+
+	list_for_each_entry_safe(tx_msg, temp, &ipmi->tx_msg_list, head) {
+		/* wake up the sleep thread on the Tx msg */
+		complete(&tx_msg->tx_complete);
+	}
+
+	/* wait for about 100ms to flush the tx message list */
+	while (count--) {
+		if (list_empty(&ipmi->tx_msg_list))
+			break;
+		schedule_timeout(1);
+	}
+	if (!list_empty(&ipmi->tx_msg_list))
+		dev_warn(&pnp_dev->dev, "tx msg list is not NULL\n");
+}
+
+static void ipmi_msg_handler(struct ipmi_recv_msg *msg, void *user_msg_data)
+{
+	struct acpi_ipmi_device *ipmi_device = user_msg_data;
+	int msg_found = 0;
+	struct acpi_ipmi_msg *tx_msg;
+	struct pnp_dev *pnp_dev = ipmi_device->pnp_dev;
+
+	if (msg->user != ipmi_device->user_interface) {
+		dev_warn(&pnp_dev->dev, "Unexpected response is returned. "
+			"returned user %p, expected user %p\n",
+			msg->user, ipmi_device->user_interface);
+		ipmi_free_recv_msg(msg);
+		return;
+	}
+	mutex_lock(&ipmi_device->tx_msg_lock);
+	list_for_each_entry(tx_msg, &ipmi_device->tx_msg_list, head) {
+		if (msg->msgid == tx_msg->tx_msgid) {
+			msg_found = 1;
+			break;
+		}
+	}
+
+	mutex_unlock(&ipmi_device->tx_msg_lock);
+	if (!msg_found) {
+		dev_warn(&pnp_dev->dev, "Unexpected response (msg id %ld) is "
+			"returned.\n", msg->msgid);
+		ipmi_free_recv_msg(msg);
+		return;
+	}
+
+	if (msg->msg.data_len) {
+		/* copy the response data to Rx_data buffer */
+		memcpy(tx_msg->rx_data, msg->msg_data, msg->msg.data_len);
+		tx_msg->rx_len = msg->msg.data_len;
+		tx_msg->msg_done = 1;
+	}
+	complete(&tx_msg->tx_complete);
+	ipmi_free_recv_msg(msg);
+};
+
+static void ipmi_register_bmc(int iface, struct device *dev)
+{
+	struct acpi_ipmi_device *ipmi_device, *temp;
+	struct pnp_dev *pnp_dev;
+	ipmi_user_t		user;
+	int err;
+	struct ipmi_smi_info smi_data;
+	acpi_handle handle;
+
+	err = ipmi_get_smi_info(iface, &smi_data);
+
+	if (err)
+		return;
+
+	if (smi_data.addr_src != SI_ACPI) {
+		put_device(smi_data.dev);
+		return;
+	}
+
+	handle = smi_data.addr_info.acpi_info.acpi_handle;
+
+	mutex_lock(&driver_data.ipmi_lock);
+	list_for_each_entry(temp, &driver_data.ipmi_devices, head) {
+		/*
+		 * if the corresponding ACPI handle is already added
+		 * to the device list, don't add it again.
+		 */
+		if (temp->handle == handle)
+			goto out;
+	}
+
+	ipmi_device = kzalloc(sizeof(*ipmi_device), GFP_KERNEL);
+
+	if (!ipmi_device)
+		goto out;
+
+	pnp_dev = to_pnp_dev(smi_data.dev);
+	ipmi_device->handle = handle;
+	ipmi_device->pnp_dev = pnp_dev;
+
+	err = ipmi_create_user(iface, &driver_data.ipmi_hndlrs,
+					ipmi_device, &user);
+	if (err) {
+		dev_warn(&pnp_dev->dev, "Can't create IPMI user interface\n");
+		kfree(ipmi_device);
+		goto out;
+	}
+	acpi_add_ipmi_device(ipmi_device);
+	ipmi_device->user_interface = user;
+	ipmi_device->ipmi_ifnum = iface;
+	mutex_unlock(&driver_data.ipmi_lock);
+	memcpy(&ipmi_device->smi_data, &smi_data, sizeof(struct ipmi_smi_info));
+	return;
+
+out:
+	mutex_unlock(&driver_data.ipmi_lock);
+	put_device(smi_data.dev);
+	return;
+}
+
+static void ipmi_bmc_gone(int iface)
+{
+	struct acpi_ipmi_device *ipmi_device, *temp;
+
+	mutex_lock(&driver_data.ipmi_lock);
+	list_for_each_entry_safe(ipmi_device, temp,
+				&driver_data.ipmi_devices, head) {
+		if (ipmi_device->ipmi_ifnum != iface)
+			continue;
+
+		acpi_remove_ipmi_device(ipmi_device);
+		put_device(ipmi_device->smi_data.dev);
+		kfree(ipmi_device);
+		break;
+	}
+	mutex_unlock(&driver_data.ipmi_lock);
+}
+/* --------------------------------------------------------------------------
+ *			Address Space Management
+ * -------------------------------------------------------------------------- */
+/*
+ * This is the IPMI opregion space handler.
+ * @function: indicates the read/write. In fact as the IPMI message is driven
+ * by command, only write is meaningful.
+ * @address: This contains the netfn/command of IPMI request message.
+ * @bits   : not used.
+ * @value  : it is an in/out parameter. It points to the IPMI message buffer.
+ *	     Before the IPMI message is sent, it represents the actual request
+ *	     IPMI message. After the IPMI message is finished, it represents
+ *	     the response IPMI message returned by IPMI command.
+ * @handler_context: IPMI device context.
+ */
+
+static acpi_status
+acpi_ipmi_space_handler(u32 function, acpi_physical_address address,
+		      u32 bits, acpi_integer *value,
+		      void *handler_context, void *region_context)
+{
+	struct acpi_ipmi_msg *tx_msg;
+	struct acpi_ipmi_device *ipmi_device = handler_context;
+	int err, rem_time;
+	acpi_status status;
+	/*
+	 * IPMI opregion message.
+	 * IPMI message is firstly written to the BMC and system software
+	 * can get the respsonse. So it is unmeaningful for the read access
+	 * of IPMI opregion.
+	 */
+	if ((function & ACPI_IO_MASK) == ACPI_READ)
+		return AE_TYPE;
+
+	if (!ipmi_device->user_interface)
+		return AE_NOT_EXIST;
+
+	tx_msg = acpi_alloc_ipmi_msg(ipmi_device);
+	if (!tx_msg)
+		return AE_NO_MEMORY;
+
+	acpi_format_ipmi_msg(tx_msg, address, value);
+	mutex_lock(&ipmi_device->tx_msg_lock);
+	list_add_tail(&tx_msg->head, &ipmi_device->tx_msg_list);
+	mutex_unlock(&ipmi_device->tx_msg_lock);
+	err = ipmi_request_settime(ipmi_device->user_interface,
+					&tx_msg->addr,
+					tx_msg->tx_msgid,
+					&tx_msg->tx_message,
+					NULL, 0, 0, 0);
+	if (err) {
+		status = AE_ERROR;
+		goto end_label;
+	}
+	rem_time = wait_for_completion_timeout(&tx_msg->tx_complete,
+					IPMI_TIMEOUT);
+	acpi_format_ipmi_response(tx_msg, value, rem_time);
+	status = AE_OK;
+
+end_label:
+	mutex_lock(&ipmi_device->tx_msg_lock);
+	list_del(&tx_msg->head);
+	mutex_unlock(&ipmi_device->tx_msg_lock);
+	kfree(tx_msg);
+	return status;
+}
+
+static void ipmi_remove_space_handler(struct acpi_ipmi_device *ipmi)
+{
+	if (!test_bit(IPMI_FLAGS_HANDLER_INSTALL, &ipmi->flags))
+		return;
+
+	acpi_remove_address_space_handler(ipmi->handle,
+				ACPI_ADR_SPACE_IPMI, &acpi_ipmi_space_handler);
+
+	clear_bit(IPMI_FLAGS_HANDLER_INSTALL, &ipmi->flags);
+}
+
+static int ipmi_install_space_handler(struct acpi_ipmi_device *ipmi)
+{
+	acpi_status status;
+
+	if (test_bit(IPMI_FLAGS_HANDLER_INSTALL, &ipmi->flags))
+		return 0;
+
+	status = acpi_install_address_space_handler(ipmi->handle,
+						    ACPI_ADR_SPACE_IPMI,
+						    &acpi_ipmi_space_handler,
+						    NULL, ipmi);
+	if (ACPI_FAILURE(status)) {
+		struct pnp_dev *pnp_dev = ipmi->pnp_dev;
+		dev_warn(&pnp_dev->dev, "Can't register IPMI opregion space "
+			"handle\n");
+		return -EINVAL;
+	}
+	set_bit(IPMI_FLAGS_HANDLER_INSTALL, &ipmi->flags);
+	return 0;
+}
+
+static void acpi_add_ipmi_device(struct acpi_ipmi_device *ipmi_device)
+{
+
+	INIT_LIST_HEAD(&ipmi_device->head);
+
+	mutex_init(&ipmi_device->tx_msg_lock);
+	INIT_LIST_HEAD(&ipmi_device->tx_msg_list);
+	ipmi_install_space_handler(ipmi_device);
+
+	list_add_tail(&ipmi_device->head, &driver_data.ipmi_devices);
+}
+
+static void acpi_remove_ipmi_device(struct acpi_ipmi_device *ipmi_device)
+{
+	/*
+	 * If the IPMI user interface is created, it should be
+	 * destroyed.
+	 */
+	if (ipmi_device->user_interface) {
+		ipmi_destroy_user(ipmi_device->user_interface);
+		ipmi_device->user_interface = NULL;
+	}
+	/* flush the Tx_msg list */
+	if (!list_empty(&ipmi_device->tx_msg_list))
+		ipmi_flush_tx_msg(ipmi_device);
+
+	list_del(&ipmi_device->head);
+	ipmi_remove_space_handler(ipmi_device);
+}
+
+static int __init acpi_ipmi_init(void)
+{
+	int result = 0;
+
+	if (acpi_disabled)
+		return result;
+
+	mutex_init(&driver_data.ipmi_lock);
+
+	result = ipmi_smi_watcher_register(&driver_data.bmc_events);
+
+	return result;
+}
+
+static void __exit acpi_ipmi_exit(void)
+{
+	struct acpi_ipmi_device *ipmi_device, *temp;
+
+	if (acpi_disabled)
+		return;
+
+	ipmi_smi_watcher_unregister(&driver_data.bmc_events);
+
+	/*
+	 * When one smi_watcher is unregistered, it is only deleted
+	 * from the smi_watcher list. But the smi_gone callback function
+	 * is not called. So explicitly uninstall the ACPI IPMI oregion
+	 * handler and free it.
+	 */
+	mutex_lock(&driver_data.ipmi_lock);
+	list_for_each_entry_safe(ipmi_device, temp,
+				&driver_data.ipmi_devices, head) {
+		acpi_remove_ipmi_device(ipmi_device);
+		put_device(ipmi_device->smi_data.dev);
+		kfree(ipmi_device);
+	}
+	mutex_unlock(&driver_data.ipmi_lock);
+}
+
+module_init(acpi_ipmi_init);
+module_exit(acpi_ipmi_exit);
