linux/drivers/hwmon/acpi_power_meter.c

/*
 * 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/slab.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		"pwr_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 const struct acpi_device_id power_meter_ids[] = {
	{"ACPI000D", 0},
	{"", 0},
};
MODULE_DEVICE_TABLE(acpi, power_meter_ids);

struct acpi_power_meter_capabilities {
	u64		flags;
	u64		units;
	u64		type;
	u64		accuracy;
	u64		sampling_time;
	u64		min_avg_interval;
	u64		max_avg_interval;
	u64		hysteresis;
	u64		configurable_cap;
	u64		min_cap;
	u64		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;
	u64		power;
	u64		cap;
	u64		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;
	}

	/* _PTP returns 0 on success, nonzero otherwise */
	if (data)
		return -EINVAL;

	return 0;
}

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;
	u64 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);
	resource->num_domain_devices = 0;
}

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_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);