diff -puN /dev/null Documentation/hwmon/acpi_power_meter
--- /dev/null
+++ a/Documentation/hwmon/acpi_power_meter
@@ -0,0 +1,51 @@
+Kernel driver power_meter
+=========================
+
+This driver talks to ACPI 4.0 power meters.
+
+Supported systems:
+  * Any recent system with ACPI 4.0.
+    Prefix: 'power_meter'
+    Datasheet: http://acpi.info/, section 10.4.
+
+Author: Darrick J. Wong
+
+Description
+-----------
+
+This driver implements sensor reading support for the power meters exposed in
+the ACPI 4.0 spec (Chapter 10.4).  These devices have a simple set of
+features--a power meter that returns average power use over a configurable
+interval, an optional capping mechanism, and a couple of trip points.  The
+sysfs interface conforms with the specification outlined in the "Power" section
+of Documentation/hwmon/sysfs-interface.
+
+Special Features
+----------------
+
+The power[1-*]_is_battery knob indicates if the power supply is a battery.
+Both power[1-*]_average_{min,max} must be set before the trip points will work.
+When both of them are set, an ACPI event will be broadcast on the ACPI netlink
+socket and a poll notification will be sent to the appropriate
+power[1-*]_average sysfs file.
+
+The power[1-*]_{model_number, serial_number, oem_info} fields display arbitrary
+strings that ACPI provides with the meter.  The measures/ directory contains
+symlinks to the devices that this meter measures.
+
+Some computers have the ability to enforce a power cap in hardware.  If this is
+the case, the power[1-*]_cap and related sysfs files will appear.  When the
+average power consumption exceeds the cap, an ACPI event will be broadcast on
+the netlink event socket and a poll notification will be sent to the
+appropriate power[1-*]_alarm file to indicate that capping has begun, and the
+hardware has taken action to reduce power consumption.  Most likely this will
+result in reduced performance.
+
+There are a few other ACPI notifications that can be sent by the firmware.  In
+all cases the ACPI event will be broadcast on the ACPI netlink event socket as
+well as sent as a poll notification to a sysfs file.  The events are as
+follows:
+
+power[1-*]_cap will be notified if the firmware changes the power cap.
+power[1-*]_interval will be notified if the firmware changes the averaging
+interval.
diff -puN drivers/acpi/Kconfig~hwmon-driver-for-acpi-40-power-meters drivers/acpi/Kconfig
--- a/drivers/acpi/Kconfig~hwmon-driver-for-acpi-40-power-meters
+++ a/drivers/acpi/Kconfig
@@ -86,6 +86,17 @@ config ACPI_PROCFS_POWER
 
 	  Say N to delete power /proc/acpi/ directories that have moved to /sys/
 
+config ACPI_POWER_METER
+	tristate "ACPI 4.0 power meter"
+	depends on HWMON
+	help
+	  This driver exposes ACPI 4.0 power meters as hardware monitoring
+	  devices.  Say Y (or M) if you have a computer with ACPI 4.0 firmware
+	  and a power meter.
+
+	  To compile this driver as a module, choose M here:
+	  the module will be called power-meter.
+
 config ACPI_SYSFS_POWER
 	bool "Future power /sys interface"
 	select POWER_SUPPLY
diff -puN drivers/acpi/Makefile~hwmon-driver-for-acpi-40-power-meters drivers/acpi/Makefile
--- a/drivers/acpi/Makefile~hwmon-driver-for-acpi-40-power-meters
+++ a/drivers/acpi/Makefile
@@ -56,6 +56,7 @@ obj-$(CONFIG_ACPI_HOTPLUG_MEMORY) += acp
 obj-$(CONFIG_ACPI_BATTERY)	+= battery.o
 obj-$(CONFIG_ACPI_SBS)		+= sbshc.o
 obj-$(CONFIG_ACPI_SBS)		+= sbs.o
+obj-$(CONFIG_ACPI_POWER_METER)	+= power_meter.o
 
 # processor has its own "processor." module_param namespace
 processor-y			:= processor_core.o processor_throttling.o
diff -puN /dev/null drivers/acpi/power_meter.c
--- /dev/null
+++ a/drivers/acpi/power_meter.c
@@ -0,0 +1,1018 @@
+/*
+ * A hwmon driver for ACPI 4.0 power meters
+ * Copyright (C) 2009 IBM
+ *
+ * Author: Darrick J. Wong <djwong@us.ibm.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/module.h>
+#include <linux/hwmon.h>
+#include <linux/hwmon-sysfs.h>
+#include <linux/jiffies.h>
+#include <linux/mutex.h>
+#include <linux/dmi.h>
+#include <linux/kdev_t.h>
+#include <linux/sched.h>
+#include <linux/time.h>
+#include <acpi/acpi_drivers.h>
+#include <acpi/acpi_bus.h>
+
+#define ACPI_POWER_METER_NAME		"power_meter"
+ACPI_MODULE_NAME(ACPI_POWER_METER_NAME);
+#define ACPI_POWER_METER_DEVICE_NAME	"Power Meter"
+#define ACPI_POWER_METER_CLASS		"power_meter_resource"
+
+#define NUM_SENSORS			17
+
+#define POWER_METER_CAN_MEASURE	(1 << 0)
+#define POWER_METER_CAN_TRIP	(1 << 1)
+#define POWER_METER_CAN_CAP	(1 << 2)
+#define POWER_METER_CAN_NOTIFY	(1 << 3)
+#define POWER_METER_IS_BATTERY	(1 << 8)
+#define UNKNOWN_HYSTERESIS	0xFFFFFFFF
+
+#define METER_NOTIFY_CONFIG	0x80
+#define METER_NOTIFY_TRIP	0x81
+#define METER_NOTIFY_CAP	0x82
+#define METER_NOTIFY_CAPPING	0x83
+#define METER_NOTIFY_INTERVAL	0x84
+
+#define POWER_AVERAGE_NAME	"power1_average"
+#define POWER_CAP_NAME		"power1_cap"
+#define POWER_AVG_INTERVAL_NAME	"power1_average_interval"
+#define POWER_ALARM_NAME	"power1_alarm"
+
+static int cap_in_hardware;
+static int force_cap_on;
+
+static int can_cap_in_hardware(void)
+{
+	return force_cap_on || cap_in_hardware;
+}
+
+static struct acpi_device_id power_meter_ids[] = {
+	{"ACPI000D", 0},
+	{"", 0},
+};
+MODULE_DEVICE_TABLE(acpi, power_meter_ids);
+
+struct acpi_power_meter_capabilities {
+	acpi_integer		flags;
+	acpi_integer		units;
+	acpi_integer		type;
+	acpi_integer		accuracy;
+	acpi_integer		sampling_time;
+	acpi_integer		min_avg_interval;
+	acpi_integer		max_avg_interval;
+	acpi_integer		hysteresis;
+	acpi_integer		configurable_cap;
+	acpi_integer		min_cap;
+	acpi_integer		max_cap;
+};
+
+struct acpi_power_meter_resource {
+	struct acpi_device	*acpi_dev;
+	acpi_bus_id		name;
+	struct mutex		lock;
+	struct device		*hwmon_dev;
+	struct acpi_power_meter_capabilities	caps;
+	acpi_string		model_number;
+	acpi_string		serial_number;
+	acpi_string		oem_info;
+	acpi_integer		power;
+	acpi_integer		cap;
+	acpi_integer		avg_interval;
+	int			sensors_valid;
+	unsigned long		sensors_last_updated;
+	struct sensor_device_attribute	sensors[NUM_SENSORS];
+	int			num_sensors;
+	int			trip[2];
+	int			num_domain_devices;
+	struct acpi_device	**domain_devices;
+	struct kobject		*holders_dir;
+};
+
+struct ro_sensor_template {
+	char *label;
+	ssize_t (*show)(struct device *dev,
+			struct device_attribute *devattr,
+			char *buf);
+	int index;
+};
+
+struct rw_sensor_template {
+	char *label;
+	ssize_t (*show)(struct device *dev,
+			struct device_attribute *devattr,
+			char *buf);
+	ssize_t (*set)(struct device *dev,
+		       struct device_attribute *devattr,
+		       const char *buf, size_t count);
+	int index;
+};
+
+/* Averaging interval */
+static int update_avg_interval(struct acpi_power_meter_resource *resource)
+{
+	unsigned long long data;
+	acpi_status status;
+
+	status = acpi_evaluate_integer(resource->acpi_dev->handle, "_GAI",
+				       NULL, &data);
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _GAI"));
+		return -ENODEV;
+	}
+
+	resource->avg_interval = data;
+	return 0;
+}
+
+static ssize_t show_avg_interval(struct device *dev,
+				 struct device_attribute *devattr,
+				 char *buf)
+{
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_power_meter_resource *resource = acpi_dev->driver_data;
+
+	mutex_lock(&resource->lock);
+	update_avg_interval(resource);
+	mutex_unlock(&resource->lock);
+
+	return sprintf(buf, "%llu\n", resource->avg_interval);
+}
+
+static ssize_t set_avg_interval(struct device *dev,
+				struct device_attribute *devattr,
+				const char *buf, size_t count)
+{
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_power_meter_resource *resource = acpi_dev->driver_data;
+	union acpi_object arg0 = { ACPI_TYPE_INTEGER };
+	struct acpi_object_list args = { 1, &arg0 };
+	int res;
+	unsigned long temp;
+	unsigned long long data;
+	acpi_status status;
+
+	res = strict_strtoul(buf, 10, &temp);
+	if (res)
+		return res;
+
+	if (temp > resource->caps.max_avg_interval ||
+	    temp < resource->caps.min_avg_interval)
+		return -EINVAL;
+	arg0.integer.value = temp;
+
+	mutex_lock(&resource->lock);
+	status = acpi_evaluate_integer(resource->acpi_dev->handle, "_PAI",
+				       &args, &data);
+	if (!ACPI_FAILURE(status))
+		resource->avg_interval = temp;
+	mutex_unlock(&resource->lock);
+
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _PAI"));
+		return -EINVAL;
+	}
+
+	/* _PAI returns 0 on success, nonzero otherwise */
+	if (data)
+		return -EINVAL;
+
+	return count;
+}
+
+/* Cap functions */
+static int update_cap(struct acpi_power_meter_resource *resource)
+{
+	unsigned long long data;
+	acpi_status status;
+
+	status = acpi_evaluate_integer(resource->acpi_dev->handle, "_GHL",
+				       NULL, &data);
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _GHL"));
+		return -ENODEV;
+	}
+
+	resource->cap = data;
+	return 0;
+}
+
+static ssize_t show_cap(struct device *dev,
+			struct device_attribute *devattr,
+			char *buf)
+{
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_power_meter_resource *resource = acpi_dev->driver_data;
+
+	mutex_lock(&resource->lock);
+	update_cap(resource);
+	mutex_unlock(&resource->lock);
+
+	return sprintf(buf, "%llu\n", resource->cap * 1000);
+}
+
+static ssize_t set_cap(struct device *dev, struct device_attribute *devattr,
+		       const char *buf, size_t count)
+{
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_power_meter_resource *resource = acpi_dev->driver_data;
+	union acpi_object arg0 = { ACPI_TYPE_INTEGER };
+	struct acpi_object_list args = { 1, &arg0 };
+	int res;
+	unsigned long temp;
+	unsigned long long data;
+	acpi_status status;
+
+	res = strict_strtoul(buf, 10, &temp);
+	if (res)
+		return res;
+
+	temp /= 1000;
+	if (temp > resource->caps.max_cap || temp < resource->caps.min_cap)
+		return -EINVAL;
+	arg0.integer.value = temp;
+
+	mutex_lock(&resource->lock);
+	status = acpi_evaluate_integer(resource->acpi_dev->handle, "_SHL",
+				       &args, &data);
+	if (!ACPI_FAILURE(status))
+		resource->cap = temp;
+	mutex_unlock(&resource->lock);
+
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _SHL"));
+		return -EINVAL;
+	}
+
+	/* _SHL returns 0 on success, nonzero otherwise */
+	if (data)
+		return -EINVAL;
+
+	return count;
+}
+
+/* Power meter trip points */
+static int set_acpi_trip(struct acpi_power_meter_resource *resource)
+{
+	union acpi_object arg_objs[] = {
+		{ACPI_TYPE_INTEGER},
+		{ACPI_TYPE_INTEGER}
+	};
+	struct acpi_object_list args = { 2, arg_objs };
+	unsigned long long data;
+	acpi_status status;
+
+	/* Both trip levels must be set */
+	if (resource->trip[0] < 0 || resource->trip[1] < 0)
+		return 0;
+
+	/* This driver stores min, max; ACPI wants max, min. */
+	arg_objs[0].integer.value = resource->trip[1];
+	arg_objs[1].integer.value = resource->trip[0];
+
+	status = acpi_evaluate_integer(resource->acpi_dev->handle, "_PTP",
+				       &args, &data);
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _PTP"));
+		return -EINVAL;
+	}
+
+	return data;
+}
+
+static ssize_t set_trip(struct device *dev, struct device_attribute *devattr,
+			const char *buf, size_t count)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_power_meter_resource *resource = acpi_dev->driver_data;
+	int res;
+	unsigned long temp;
+
+	res = strict_strtoul(buf, 10, &temp);
+	if (res)
+		return res;
+
+	temp /= 1000;
+	if (temp < 0)
+		return -EINVAL;
+
+	mutex_lock(&resource->lock);
+	resource->trip[attr->index - 7] = temp;
+	res = set_acpi_trip(resource);
+	mutex_unlock(&resource->lock);
+
+	if (res)
+		return res;
+
+	return count;
+}
+
+/* Power meter */
+static int update_meter(struct acpi_power_meter_resource *resource)
+{
+	unsigned long long data;
+	acpi_status status;
+	unsigned long local_jiffies = jiffies;
+
+	if (time_before(local_jiffies, resource->sensors_last_updated +
+			msecs_to_jiffies(resource->caps.sampling_time)) &&
+			resource->sensors_valid)
+		return 0;
+
+	status = acpi_evaluate_integer(resource->acpi_dev->handle, "_PMM",
+				       NULL, &data);
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _PMM"));
+		return -ENODEV;
+	}
+
+	resource->power = data;
+	resource->sensors_valid = 1;
+	resource->sensors_last_updated = jiffies;
+	return 0;
+}
+
+static ssize_t show_power(struct device *dev,
+			  struct device_attribute *devattr,
+			  char *buf)
+{
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_power_meter_resource *resource = acpi_dev->driver_data;
+
+	mutex_lock(&resource->lock);
+	update_meter(resource);
+	mutex_unlock(&resource->lock);
+
+	return sprintf(buf, "%llu\n", resource->power * 1000);
+}
+
+/* Miscellaneous */
+static ssize_t show_str(struct device *dev,
+			struct device_attribute *devattr,
+			char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_power_meter_resource *resource = acpi_dev->driver_data;
+	acpi_string val;
+
+	switch (attr->index) {
+	case 0:
+		val = resource->model_number;
+		break;
+	case 1:
+		val = resource->serial_number;
+		break;
+	case 2:
+		val = resource->oem_info;
+		break;
+	default:
+		BUG();
+	}
+
+	return sprintf(buf, "%s\n", val);
+}
+
+static ssize_t show_val(struct device *dev,
+			struct device_attribute *devattr,
+			char *buf)
+{
+	struct sensor_device_attribute *attr = to_sensor_dev_attr(devattr);
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_power_meter_resource *resource = acpi_dev->driver_data;
+	acpi_integer val = 0;
+
+	switch (attr->index) {
+	case 0:
+		val = resource->caps.min_avg_interval;
+		break;
+	case 1:
+		val = resource->caps.max_avg_interval;
+		break;
+	case 2:
+		val = resource->caps.min_cap * 1000;
+		break;
+	case 3:
+		val = resource->caps.max_cap * 1000;
+		break;
+	case 4:
+		if (resource->caps.hysteresis == UNKNOWN_HYSTERESIS)
+			return sprintf(buf, "unknown\n");
+
+		val = resource->caps.hysteresis * 1000;
+		break;
+	case 5:
+		if (resource->caps.flags & POWER_METER_IS_BATTERY)
+			val = 1;
+		else
+			val = 0;
+		break;
+	case 6:
+		if (resource->power > resource->cap)
+			val = 1;
+		else
+			val = 0;
+		break;
+	case 7:
+	case 8:
+		if (resource->trip[attr->index - 7] < 0)
+			return sprintf(buf, "unknown\n");
+
+		val = resource->trip[attr->index - 7] * 1000;
+		break;
+	default:
+		BUG();
+	}
+
+	return sprintf(buf, "%llu\n", val);
+}
+
+static ssize_t show_accuracy(struct device *dev,
+			     struct device_attribute *devattr,
+			     char *buf)
+{
+	struct acpi_device *acpi_dev = to_acpi_device(dev);
+	struct acpi_power_meter_resource *resource = acpi_dev->driver_data;
+	unsigned int acc = resource->caps.accuracy;
+
+	return sprintf(buf, "%u.%u%%\n", acc / 1000, acc % 1000);
+}
+
+static ssize_t show_name(struct device *dev,
+			 struct device_attribute *devattr,
+			 char *buf)
+{
+	return sprintf(buf, "%s\n", ACPI_POWER_METER_NAME);
+}
+
+/* Sensor descriptions.  If you add a sensor, update NUM_SENSORS above! */
+static struct ro_sensor_template meter_ro_attrs[] = {
+{POWER_AVERAGE_NAME, show_power, 0},
+{"power1_accuracy", show_accuracy, 0},
+{"power1_average_interval_min", show_val, 0},
+{"power1_average_interval_max", show_val, 1},
+{"power1_is_battery", show_val, 5},
+{NULL, NULL, 0},
+};
+
+static struct rw_sensor_template meter_rw_attrs[] = {
+{POWER_AVG_INTERVAL_NAME, show_avg_interval, set_avg_interval, 0},
+{NULL, NULL, NULL, 0},
+};
+
+static struct ro_sensor_template misc_cap_attrs[] = {
+{"power1_cap_min", show_val, 2},
+{"power1_cap_max", show_val, 3},
+{"power1_cap_hyst", show_val, 4},
+{POWER_ALARM_NAME, show_val, 6},
+{NULL, NULL, 0},
+};
+
+static struct ro_sensor_template ro_cap_attrs[] = {
+{POWER_CAP_NAME, show_cap, 0},
+{NULL, NULL, 0},
+};
+
+static struct rw_sensor_template rw_cap_attrs[] = {
+{POWER_CAP_NAME, show_cap, set_cap, 0},
+{NULL, NULL, NULL, 0},
+};
+
+static struct rw_sensor_template trip_attrs[] = {
+{"power1_average_min", show_val, set_trip, 7},
+{"power1_average_max", show_val, set_trip, 8},
+{NULL, NULL, NULL, 0},
+};
+
+static struct ro_sensor_template misc_attrs[] = {
+{"name", show_name, 0},
+{"power1_model_number", show_str, 0},
+{"power1_oem_info", show_str, 2},
+{"power1_serial_number", show_str, 1},
+{NULL, NULL, 0},
+};
+
+/* Read power domain data */
+static void remove_domain_devices(struct acpi_power_meter_resource *resource)
+{
+	int i;
+
+	if (!resource->num_domain_devices)
+		return;
+
+	for (i = 0; i < resource->num_domain_devices; i++) {
+		struct acpi_device *obj = resource->domain_devices[i];
+		if (!obj)
+			continue;
+
+		sysfs_remove_link(resource->holders_dir,
+				  kobject_name(&obj->dev.kobj));
+		put_device(&obj->dev);
+	}
+
+	kfree(resource->domain_devices);
+	kobject_put(resource->holders_dir);
+}
+
+static int read_domain_devices(struct acpi_power_meter_resource *resource)
+{
+	int res = 0;
+	int i;
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	union acpi_object *pss;
+	acpi_status status;
+
+	status = acpi_evaluate_object(resource->acpi_dev->handle, "_PMD", NULL,
+				      &buffer);
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _PMD"));
+		return -ENODEV;
+	}
+
+	pss = buffer.pointer;
+	if (!pss ||
+	    pss->type != ACPI_TYPE_PACKAGE) {
+		dev_err(&resource->acpi_dev->dev, ACPI_POWER_METER_NAME
+			"Invalid _PMD data\n");
+		res = -EFAULT;
+		goto end;
+	}
+
+	if (!pss->package.count)
+		goto end;
+
+	resource->domain_devices = kzalloc(sizeof(struct acpi_device *) *
+					   pss->package.count, GFP_KERNEL);
+	if (!resource->domain_devices) {
+		res = -ENOMEM;
+		goto end;
+	}
+
+	resource->holders_dir = kobject_create_and_add("measures",
+					&resource->acpi_dev->dev.kobj);
+	if (!resource->holders_dir) {
+		res = -ENOMEM;
+		goto exit_free;
+	}
+
+	resource->num_domain_devices = pss->package.count;
+
+	for (i = 0; i < pss->package.count; i++) {
+		struct acpi_device *obj;
+		union acpi_object *element = &(pss->package.elements[i]);
+
+		/* Refuse non-references */
+		if (element->type != ACPI_TYPE_LOCAL_REFERENCE)
+			continue;
+
+		/* Create a symlink to domain objects */
+		resource->domain_devices[i] = NULL;
+		status = acpi_bus_get_device(element->reference.handle,
+					     &resource->domain_devices[i]);
+		if (ACPI_FAILURE(status))
+			continue;
+
+		obj = resource->domain_devices[i];
+		get_device(&obj->dev);
+
+		res = sysfs_create_link(resource->holders_dir, &obj->dev.kobj,
+				      kobject_name(&obj->dev.kobj));
+		if (res) {
+			put_device(&obj->dev);
+			resource->domain_devices[i] = NULL;
+		}
+	}
+
+	res = 0;
+	goto end;
+
+exit_free:
+	kfree(resource->domain_devices);
+end:
+	kfree(buffer.pointer);
+	return res;
+}
+
+/* Registration and deregistration */
+static int register_ro_attrs(struct acpi_power_meter_resource *resource,
+			     struct ro_sensor_template *ro)
+{
+	struct device *dev = &resource->acpi_dev->dev;
+	struct sensor_device_attribute *sensors =
+		&resource->sensors[resource->num_sensors];
+	int res = 0;
+
+	while (ro->label) {
+		sensors->dev_attr.attr.name = ro->label;
+		sensors->dev_attr.attr.mode = S_IRUGO;
+		sensors->dev_attr.show = ro->show;
+		sensors->index = ro->index;
+
+		res = device_create_file(dev, &sensors->dev_attr);
+		if (res) {
+			sensors->dev_attr.attr.name = NULL;
+			goto error;
+		}
+		sensors++;
+		resource->num_sensors++;
+		ro++;
+	}
+
+error:
+	return res;
+}
+
+static int register_rw_attrs(struct acpi_power_meter_resource *resource,
+			     struct rw_sensor_template *rw)
+{
+	struct device *dev = &resource->acpi_dev->dev;
+	struct sensor_device_attribute *sensors =
+		&resource->sensors[resource->num_sensors];
+	int res = 0;
+
+	while (rw->label) {
+		sensors->dev_attr.attr.name = rw->label;
+		sensors->dev_attr.attr.mode = S_IRUGO | S_IWUSR;
+		sensors->dev_attr.show = rw->show;
+		sensors->dev_attr.store = rw->set;
+		sensors->index = rw->index;
+
+		res = device_create_file(dev, &sensors->dev_attr);
+		if (res) {
+			sensors->dev_attr.attr.name = NULL;
+			goto error;
+		}
+		sensors++;
+		resource->num_sensors++;
+		rw++;
+	}
+
+error:
+	return res;
+}
+
+static void remove_attrs(struct acpi_power_meter_resource *resource)
+{
+	int i;
+
+	for (i = 0; i < resource->num_sensors; i++) {
+		if (!resource->sensors[i].dev_attr.attr.name)
+			continue;
+		device_remove_file(&resource->acpi_dev->dev,
+				   &resource->sensors[i].dev_attr);
+	}
+
+	remove_domain_devices(resource);
+
+	resource->num_sensors = 0;
+}
+
+static int setup_attrs(struct acpi_power_meter_resource *resource)
+{
+	int res = 0;
+
+	res = read_domain_devices(resource);
+	if (res)
+		return res;
+
+	if (resource->caps.flags & POWER_METER_CAN_MEASURE) {
+		res = register_ro_attrs(resource, meter_ro_attrs);
+		if (res)
+			goto error;
+		res = register_rw_attrs(resource, meter_rw_attrs);
+		if (res)
+			goto error;
+	}
+
+	if (resource->caps.flags & POWER_METER_CAN_CAP) {
+		if (!can_cap_in_hardware()) {
+			dev_err(&resource->acpi_dev->dev,
+				"Ignoring unsafe software power cap!\n");
+			goto skip_unsafe_cap;
+		}
+
+		if (resource->caps.configurable_cap) {
+			res = register_rw_attrs(resource, rw_cap_attrs);
+			if (res)
+				goto error;
+		} else {
+			res = register_ro_attrs(resource, ro_cap_attrs);
+			if (res)
+				goto error;
+		}
+		res = register_ro_attrs(resource, misc_cap_attrs);
+		if (res)
+			goto error;
+	}
+skip_unsafe_cap:
+
+	if (resource->caps.flags & POWER_METER_CAN_TRIP) {
+		res = register_rw_attrs(resource, trip_attrs);
+		if (res)
+			goto error;
+	}
+
+	res = register_ro_attrs(resource, misc_attrs);
+	if (res)
+		goto error;
+
+	return res;
+error:
+	remove_domain_devices(resource);
+	remove_attrs(resource);
+	return res;
+}
+
+static void free_capabilities(struct acpi_power_meter_resource *resource)
+{
+	acpi_string *str;
+	int i;
+
+	str = &resource->model_number;
+	for (i = 0; i < 3; i++, str++)
+		kfree(*str);
+}
+
+static int read_capabilities(struct acpi_power_meter_resource *resource)
+{
+	int res = 0;
+	int i;
+	struct acpi_buffer buffer = { ACPI_ALLOCATE_BUFFER, NULL };
+	struct acpi_buffer state = { 0, NULL };
+	struct acpi_buffer format = { sizeof("NNNNNNNNNNN"), "NNNNNNNNNNN" };
+	union acpi_object *pss;
+	acpi_string *str;
+	acpi_status status;
+
+	status = acpi_evaluate_object(resource->acpi_dev->handle, "_PMC", NULL,
+				      &buffer);
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Evaluating _PMC"));
+		return -ENODEV;
+	}
+
+	pss = buffer.pointer;
+	if (!pss ||
+	    pss->type != ACPI_TYPE_PACKAGE ||
+	    pss->package.count != 14) {
+		dev_err(&resource->acpi_dev->dev, ACPI_POWER_METER_NAME
+			"Invalid _PMC data\n");
+		res = -EFAULT;
+		goto end;
+	}
+
+	/* Grab all the integer data at once */
+	state.length = sizeof(struct acpi_power_meter_capabilities);
+	state.pointer = &resource->caps;
+
+	status = acpi_extract_package(pss, &format, &state);
+	if (ACPI_FAILURE(status)) {
+		ACPI_EXCEPTION((AE_INFO, status, "Invalid data"));
+		res = -EFAULT;
+		goto end;
+	}
+
+	if (resource->caps.units) {
+		dev_err(&resource->acpi_dev->dev, ACPI_POWER_METER_NAME
+			"Unknown units %llu.\n",
+			resource->caps.units);
+		res = -EINVAL;
+		goto end;
+	}
+
+	/* Grab the string data */
+	str = &resource->model_number;
+
+	for (i = 11; i < 14; i++) {
+		union acpi_object *element = &(pss->package.elements[i]);
+
+		if (element->type != ACPI_TYPE_STRING) {
+			res = -EINVAL;
+			goto error;
+		}
+
+		*str = kzalloc(sizeof(u8) * (element->string.length + 1),
+			       GFP_KERNEL);
+		if (!*str) {
+			res = -ENOMEM;
+			goto error;
+		}
+
+		strncpy(*str, element->string.pointer, element->string.length);
+		str++;
+	}
+
+	dev_info(&resource->acpi_dev->dev, "Found ACPI power meter.\n");
+	goto end;
+error:
+	str = &resource->model_number;
+	for (i = 0; i < 3; i++, str++)
+		kfree(*str);
+end:
+	kfree(buffer.pointer);
+	return res;
+}
+
+/* Handle ACPI event notifications */
+static void acpi_power_meter_notify(struct acpi_device *device, u32 event)
+{
+	struct acpi_power_meter_resource *resource;
+	int res;
+
+	if (!device || !acpi_driver_data(device))
+		return;
+
+	resource = acpi_driver_data(device);
+
+	mutex_lock(&resource->lock);
+	switch (event) {
+	case METER_NOTIFY_CONFIG:
+		free_capabilities(resource);
+		res = read_capabilities(resource);
+		if (res)
+			break;
+
+		remove_attrs(resource);
+		setup_attrs(resource);
+		break;
+	case METER_NOTIFY_TRIP:
+		sysfs_notify(&device->dev.kobj, NULL, POWER_AVERAGE_NAME);
+		update_meter(resource);
+		break;
+	case METER_NOTIFY_CAP:
+		sysfs_notify(&device->dev.kobj, NULL, POWER_CAP_NAME);
+		update_cap(resource);
+		break;
+	case METER_NOTIFY_INTERVAL:
+		sysfs_notify(&device->dev.kobj, NULL, POWER_AVG_INTERVAL_NAME);
+		update_avg_interval(resource);
+		break;
+	case METER_NOTIFY_CAPPING:
+		sysfs_notify(&device->dev.kobj, NULL, POWER_ALARM_NAME);
+		dev_info(&device->dev, "Capping in progress.\n");
+		break;
+	default:
+		BUG();
+	}
+	mutex_unlock(&resource->lock);
+
+	acpi_bus_generate_netlink_event(ACPI_POWER_METER_CLASS,
+					dev_name(&device->dev), event, 0);
+}
+
+static int acpi_power_meter_add(struct acpi_device *device)
+{
+	int res;
+	struct acpi_power_meter_resource *resource;
+
+	if (!device)
+		return -EINVAL;
+
+	resource = kzalloc(sizeof(struct acpi_power_meter_resource),
+			   GFP_KERNEL);
+	if (!resource)
+		return -ENOMEM;
+
+	resource->sensors_valid = 0;
+	resource->acpi_dev = device;
+	mutex_init(&resource->lock);
+	strcpy(acpi_device_name(device), ACPI_POWER_METER_DEVICE_NAME);
+	strcpy(acpi_device_class(device), ACPI_POWER_METER_CLASS);
+	device->driver_data = resource;
+
+	free_capabilities(resource);
+	res = read_capabilities(resource);
+	if (res)
+		goto exit_free;
+
+	resource->trip[0] = resource->trip[1] = -1;
+
+	res = setup_attrs(resource);
+	if (res)
+		goto exit_free;
+
+	resource->hwmon_dev = hwmon_device_register(&device->dev);
+	if (IS_ERR(resource->hwmon_dev)) {
+		res = PTR_ERR(resource->hwmon_dev);
+		goto exit_remove;
+	}
+
+	res = 0;
+	goto exit;
+
+exit_remove:
+	remove_attrs(resource);
+exit_free:
+	kfree(resource);
+exit:
+	return res;
+}
+
+static int acpi_power_meter_remove(struct acpi_device *device, int type)
+{
+	struct acpi_power_meter_resource *resource;
+
+	if (!device || !acpi_driver_data(device))
+		return -EINVAL;
+
+	resource = acpi_driver_data(device);
+	hwmon_device_unregister(resource->hwmon_dev);
+
+	free_capabilities(resource);
+	remove_attrs(resource);
+
+	kfree(resource);
+	return 0;
+}
+
+static int acpi_power_meter_resume(struct acpi_device *device)
+{
+	struct acpi_power_meter_resource *resource;
+
+	if (!device || !acpi_driver_data(device))
+		return -EINVAL;
+
+	resource = acpi_driver_data(device);
+	free_capabilities(resource);
+	read_capabilities(resource);
+
+	return 0;
+}
+
+static struct acpi_driver acpi_power_meter_driver = {
+	.name = "power_meter",
+	.class = ACPI_POWER_METER_CLASS,
+	.ids = power_meter_ids,
+	.ops = {
+		.add = acpi_power_meter_add,
+		.remove = acpi_power_meter_remove,
+		.resume = acpi_power_meter_resume,
+		.notify = acpi_power_meter_notify,
+		},
+};
+
+/* Module init/exit routines */
+static int __init enable_cap_knobs(const struct dmi_system_id *d)
+{
+	cap_in_hardware = 1;
+	return 0;
+}
+
+static struct dmi_system_id __initdata pm_dmi_table[] = {
+	{
+		enable_cap_knobs, "IBM Active Energy Manager",
+		{
+			DMI_MATCH(DMI_SYS_VENDOR, "IBM")
+		},
+	},
+	{}
+};
+
+static int __init acpi_power_meter_init(void)
+{
+	int result;
+
+	if (acpi_disabled)
+		return -ENODEV;
+
+	dmi_check_system(pm_dmi_table);
+
+	result = acpi_bus_register_driver(&acpi_power_meter_driver);
+	if (result < 0)
+		return -ENODEV;
+
+	return 0;
+}
+
+static void __exit acpi_power_meter_exit(void)
+{
+	acpi_bus_unregister_driver(&acpi_power_meter_driver);
+}
+
+MODULE_AUTHOR("Darrick J. Wong <djwong@us.ibm.com>");
+MODULE_DESCRIPTION("ACPI 4.0 power meter driver");
+MODULE_LICENSE("GPL");
+
+module_param(force_cap_on, bool, 0644);
+MODULE_PARM_DESC(force_cap_on, "Enable power cap even it is unsafe to do so.");
+
+module_init(acpi_power_meter_init);
+module_exit(acpi_power_meter_exit);
