kernel/pm_qos_params.c - maze/linux - Git at Google

 /*
  * This module exposes the interface to kernel space for specifying
  * QoS dependencies.  It provides infrastructure for registration of:
  *
  * Dependents on a QoS value : register requirements
  * Watchers of QoS value : get notified when target QoS value changes
  *
  * This QoS design is best effort based.  Dependents register their QoS needs.
  * Watchers register to keep track of the current QoS needs of the system.
  *
  * There are 3 basic classes of QoS parameter: latency, timeout, throughput
  * each have defined units:
  * latency: usec
  * timeout: usec <-- currently not used.
  * throughput: kbs (kilo byte / sec)
  *
  * There are lists of pm_qos_objects each one wrapping requirements, notifiers
  *
  * User mode requirements on a QOS parameter register themselves to the
  * subsystem by opening the device node /dev/... and writing there request to
  * the node.  As long as the process holds a file handle open to the node the
  * client continues to be accounted for.  Upon file release the usermode
  * requirement is removed and a new qos target is computed.  This way when the
  * requirement that the application has is cleaned up when closes the file
  * pointer or exits the pm_qos_object will get an opportunity to clean up.
  *
  * mark gross mgross@linux.intel.com
  */

 #include <linux/pm_qos_params.h>
 #include <linux/sched.h>
 #include <linux/spinlock.h>
 #include <linux/slab.h>
 #include <linux/time.h>
 #include <linux/fs.h>
 #include <linux/device.h>
 #include <linux/miscdevice.h>
 #include <linux/string.h>
 #include <linux/platform_device.h>
 #include <linux/init.h>

 #include <linux/uaccess.h>

 /*
  * locking rule: all changes to target_value or requirements or notifiers lists
  * or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
  * held, taken with _irqsave.  One lock to rule them all
  */
 struct requirement_list {
 	struct list_head list;
 	union {
 		s32 value;
 		s32 usec;
 		s32 kbps;
 	};
 	char *name;
 };

 static s32 max_compare(s32 v1, s32 v2);
 static s32 min_compare(s32 v1, s32 v2);

 struct pm_qos_object {
 	struct requirement_list requirements;
 	struct blocking_notifier_head *notifiers;
 	struct miscdevice pm_qos_power_miscdev;
 	char *name;
 	s32 default_value;
 	s32 target_value;
 	s32 (*comparitor)(s32, s32);
 };

 static struct pm_qos_object null_pm_qos;
 static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
 static struct pm_qos_object cpu_dma_pm_qos = {
 	.requirements = {LIST_HEAD_INIT(cpu_dma_pm_qos.requirements.list)},
 	.notifiers = &cpu_dma_lat_notifier,
 	.name = "cpu_dma_latency",
 	.default_value = 2000 * USEC_PER_SEC,
 	.target_value = 2000 * USEC_PER_SEC,
 	.comparitor = min_compare
 };

 static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
 static struct pm_qos_object network_lat_pm_qos = {
 	.requirements = {LIST_HEAD_INIT(network_lat_pm_qos.requirements.list)},
 	.notifiers = &network_lat_notifier,
 	.name = "network_latency",
 	.default_value = 2000 * USEC_PER_SEC,
 	.target_value = 2000 * USEC_PER_SEC,
 	.comparitor = min_compare
 };


 static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
 static struct pm_qos_object network_throughput_pm_qos = {
 	.requirements =
 		{LIST_HEAD_INIT(network_throughput_pm_qos.requirements.list)},
 	.notifiers = &network_throughput_notifier,
 	.name = "network_throughput",
 	.default_value = 0,
 	.target_value = 0,
 	.comparitor = max_compare
 };


 static struct pm_qos_object *pm_qos_array[] = {
 	&null_pm_qos,
 	&cpu_dma_pm_qos,
 	&network_lat_pm_qos,
 	&network_throughput_pm_qos
 };

 static DEFINE_SPINLOCK(pm_qos_lock);

 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 		size_t count, loff_t *f_pos);
 static int pm_qos_power_open(struct inode *inode, struct file *filp);
 static int pm_qos_power_release(struct inode *inode, struct file *filp);

 static const struct file_operations pm_qos_power_fops = {
 	.write = pm_qos_power_write,
 	.open = pm_qos_power_open,
 	.release = pm_qos_power_release,
 };

 /* static helper functions */
 static s32 max_compare(s32 v1, s32 v2)
 {
 	return max(v1, v2);
 }

 static s32 min_compare(s32 v1, s32 v2)
 {
 	return min(v1, v2);
 }


 static void update_target(int target)
 {
 	s32 extreme_value;
 	struct requirement_list *node;
 	unsigned long flags;
 	int call_notifier = 0;

 	spin_lock_irqsave(&pm_qos_lock, flags);
 	extreme_value = pm_qos_array[target]->default_value;
 	list_for_each_entry(node,
 			&pm_qos_array[target]->requirements.list, list) {
 		extreme_value = pm_qos_array[target]->comparitor(
 				extreme_value, node->value);
 	}
 	if (pm_qos_array[target]->target_value != extreme_value) {
 		call_notifier = 1;
 		pm_qos_array[target]->target_value = extreme_value;
 		pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
 			pm_qos_array[target]->target_value);
 	}
 	spin_unlock_irqrestore(&pm_qos_lock, flags);

 	if (call_notifier)
 		blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
 			(unsigned long) extreme_value, NULL);
 }

 static int register_pm_qos_misc(struct pm_qos_object *qos)
 {
 	qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
 	qos->pm_qos_power_miscdev.name = qos->name;
 	qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;

 	return misc_register(&qos->pm_qos_power_miscdev);
 }

 static int find_pm_qos_object_by_minor(int minor)
 {
 	int pm_qos_class;

 	for (pm_qos_class = 0;
 		pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
 		if (minor ==
 			pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
 			return pm_qos_class;
 	}
 	return -1;
 }

 /**
  * pm_qos_requirement - returns current system wide qos expectation
  * @pm_qos_class: identification of which qos value is requested
  *
  * This function returns the current target value in an atomic manner.
  */
 int pm_qos_requirement(int pm_qos_class)
 {
 	int ret_val;
 	unsigned long flags;

 	spin_lock_irqsave(&pm_qos_lock, flags);
 	ret_val = pm_qos_array[pm_qos_class]->target_value;
 	spin_unlock_irqrestore(&pm_qos_lock, flags);

 	return ret_val;
 }
 EXPORT_SYMBOL_GPL(pm_qos_requirement);

 /**
  * pm_qos_add_requirement - inserts new qos request into the list
  * @pm_qos_class: identifies which list of qos request to us
  * @name: identifies the request
  * @value: defines the qos request
  *
  * This function inserts a new entry in the pm_qos_class list of requested qos
  * performance charactoistics.  It recomputes the agregate QoS expectations for
  * the pm_qos_class of parrameters.
  */
 int pm_qos_add_requirement(int pm_qos_class, char *name, s32 value)
 {
 	struct requirement_list *dep;
 	unsigned long flags;

 	dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
 	if (dep) {
 		if (value == PM_QOS_DEFAULT_VALUE)
 			dep->value = pm_qos_array[pm_qos_class]->default_value;
 		else
 			dep->value = value;
 		dep->name = kstrdup(name, GFP_KERNEL);
 		if (!dep->name)
 			goto cleanup;

 		spin_lock_irqsave(&pm_qos_lock, flags);
 		list_add(&dep->list,
 			&pm_qos_array[pm_qos_class]->requirements.list);
 		spin_unlock_irqrestore(&pm_qos_lock, flags);
 		update_target(pm_qos_class);

 		return 0;
 	}

 cleanup:
 	kfree(dep);
 	return -ENOMEM;
 }
 EXPORT_SYMBOL_GPL(pm_qos_add_requirement);

 /**
  * pm_qos_update_requirement - modifies an existing qos request
  * @pm_qos_class: identifies which list of qos request to us
  * @name: identifies the request
  * @value: defines the qos request
  *
  * Updates an existing qos requierement for the pm_qos_class of parameters along
  * with updating the target pm_qos_class value.
  *
  * If the named request isn't in the lest then no change is made.
  */
 int pm_qos_update_requirement(int pm_qos_class, char *name, s32 new_value)
 {
 	unsigned long flags;
 	struct requirement_list *node;
 	int pending_update = 0;

 	spin_lock_irqsave(&pm_qos_lock, flags);
 	list_for_each_entry(node,
 		&pm_qos_array[pm_qos_class]->requirements.list, list) {
 		if (strcmp(node->name, name) == 0) {
 			if (new_value == PM_QOS_DEFAULT_VALUE)
 				node->value =
 				pm_qos_array[pm_qos_class]->default_value;
 			else
 				node->value = new_value;
 			pending_update = 1;
 			break;
 		}
 	}
 	spin_unlock_irqrestore(&pm_qos_lock, flags);
 	if (pending_update)
 		update_target(pm_qos_class);

 	return 0;
 }
 EXPORT_SYMBOL_GPL(pm_qos_update_requirement);

 /**
  * pm_qos_remove_requirement - modifies an existing qos request
  * @pm_qos_class: identifies which list of qos request to us
  * @name: identifies the request
  *
  * Will remove named qos request from pm_qos_class list of parrameters and
  * recompute the current target value for the pm_qos_class.
  */
 void pm_qos_remove_requirement(int pm_qos_class, char *name)
 {
 	unsigned long flags;
 	struct requirement_list *node;
 	int pending_update = 0;

 	spin_lock_irqsave(&pm_qos_lock, flags);
 	list_for_each_entry(node,
 		&pm_qos_array[pm_qos_class]->requirements.list, list) {
 		if (strcmp(node->name, name) == 0) {
 			kfree(node->name);
 			list_del(&node->list);
 			kfree(node);
 			pending_update = 1;
 			break;
 		}
 	}
 	spin_unlock_irqrestore(&pm_qos_lock, flags);
 	if (pending_update)
 		update_target(pm_qos_class);
 }
 EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);

 /**
  * pm_qos_add_notifier - sets notification entry for changes to target value
  * @pm_qos_class: identifies which qos target changes should be notified.
  * @notifier: notifier block managed by caller.
  *
  * will register the notifier into a notification chain that gets called
  * uppon changes to the pm_qos_class target value.
  */
  int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
 {
 	int retval;

 	retval = blocking_notifier_chain_register(
 			pm_qos_array[pm_qos_class]->notifiers, notifier);

 	return retval;
 }
 EXPORT_SYMBOL_GPL(pm_qos_add_notifier);

 /**
  * pm_qos_remove_notifier - deletes notification entry from chain.
  * @pm_qos_class: identifies which qos target changes are notified.
  * @notifier: notifier block to be removed.
  *
  * will remove the notifier from the notification chain that gets called
  * uppon changes to the pm_qos_class target value.
  */
 int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
 {
 	int retval;

 	retval = blocking_notifier_chain_unregister(
 			pm_qos_array[pm_qos_class]->notifiers, notifier);

 	return retval;
 }
 EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);

 #define PID_NAME_LEN sizeof("process_1234567890")
 static char name[PID_NAME_LEN];

 static int pm_qos_power_open(struct inode *inode, struct file *filp)
 {
 	int ret;
 	long pm_qos_class;

 	pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
 	if (pm_qos_class >= 0) {
 		filp->private_data = (void *)pm_qos_class;
 		sprintf(name, "process_%d", current->pid);
 		ret = pm_qos_add_requirement(pm_qos_class, name,
 					PM_QOS_DEFAULT_VALUE);
 		if (ret >= 0)
 			return 0;
 	}

 	return -EPERM;
 }

 static int pm_qos_power_release(struct inode *inode, struct file *filp)
 {
 	int pm_qos_class;

 	pm_qos_class = (long)filp->private_data;
 	sprintf(name, "process_%d", current->pid);
 	pm_qos_remove_requirement(pm_qos_class, name);

 	return 0;
 }

 static ssize_t pm_qos_power_write(struct file *filp, const char __user *buf,
 		size_t count, loff_t *f_pos)
 {
 	s32 value;
 	int pm_qos_class;

 	pm_qos_class = (long)filp->private_data;
 	if (count != sizeof(s32))
 		return -EINVAL;
 	if (copy_from_user(&value, buf, sizeof(s32)))
 		return -EFAULT;
 	sprintf(name, "process_%d", current->pid);
 	pm_qos_update_requirement(pm_qos_class, name, value);

 	return  sizeof(s32);
 }


 static int __init pm_qos_power_init(void)
 {
 	int ret = 0;

 	ret = register_pm_qos_misc(&cpu_dma_pm_qos);
 	if (ret < 0) {
 		printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
 		return ret;
 	}
 	ret = register_pm_qos_misc(&network_lat_pm_qos);
 	if (ret < 0) {
 		printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
 		return ret;
 	}
 	ret = register_pm_qos_misc(&network_throughput_pm_qos);
 	if (ret < 0)
 		printk(KERN_ERR
 			"pm_qos_param: network_throughput setup failed\n");

 	return ret;
 }

 late_initcall(pm_qos_power_init);
	/*
	* This module exposes the interface to kernel space for specifying
	* QoS dependencies. It provides infrastructure for registration of:
	*
	* Dependents on a QoS value : register requirements
	* Watchers of QoS value : get notified when target QoS value changes
	*
	* This QoS design is best effort based. Dependents register their QoS needs.
	* Watchers register to keep track of the current QoS needs of the system.
	*
	* There are 3 basic classes of QoS parameter: latency, timeout, throughput
	* each have defined units:
	* latency: usec
	* timeout: usec <-- currently not used.
	* throughput: kbs (kilo byte / sec)
	*
	* There are lists of pm_qos_objects each one wrapping requirements, notifiers
	*
	* User mode requirements on a QOS parameter register themselves to the
	* subsystem by opening the device node /dev/... and writing there request to
	* the node. As long as the process holds a file handle open to the node the
	* client continues to be accounted for. Upon file release the usermode
	* requirement is removed and a new qos target is computed. This way when the
	* requirement that the application has is cleaned up when closes the file
	* pointer or exits the pm_qos_object will get an opportunity to clean up.
	*
	* mark gross mgross@linux.intel.com
	*/

	#include <linux/pm_qos_params.h>
	#include <linux/sched.h>
	#include <linux/spinlock.h>
	#include <linux/slab.h>
	#include <linux/time.h>
	#include <linux/fs.h>
	#include <linux/device.h>
	#include <linux/miscdevice.h>
	#include <linux/string.h>
	#include <linux/platform_device.h>
	#include <linux/init.h>

	#include <linux/uaccess.h>

	/*
	* locking rule: all changes to target_value or requirements or notifiers lists
	* or pm_qos_object list and pm_qos_objects need to happen with pm_qos_lock
	* held, taken with _irqsave. One lock to rule them all
	*/
	struct requirement_list {
	struct list_head list;
	union {
	s32 value;
	s32 usec;
	s32 kbps;
	};
	char *name;
	};

	static s32 max_compare(s32 v1, s32 v2);
	static s32 min_compare(s32 v1, s32 v2);

	struct pm_qos_object {
	struct requirement_list requirements;
	struct blocking_notifier_head *notifiers;
	struct miscdevice pm_qos_power_miscdev;
	char *name;
	s32 default_value;
	s32 target_value;
	s32 (*comparitor)(s32, s32);
	};

	static struct pm_qos_object null_pm_qos;
	static BLOCKING_NOTIFIER_HEAD(cpu_dma_lat_notifier);
	static struct pm_qos_object cpu_dma_pm_qos = {
	.requirements = {LIST_HEAD_INIT(cpu_dma_pm_qos.requirements.list)},
	.notifiers = &cpu_dma_lat_notifier,
	.name = "cpu_dma_latency",
	.default_value = 2000 * USEC_PER_SEC,
	.target_value = 2000 * USEC_PER_SEC,
	.comparitor = min_compare
	};

	static BLOCKING_NOTIFIER_HEAD(network_lat_notifier);
	static struct pm_qos_object network_lat_pm_qos = {
	.requirements = {LIST_HEAD_INIT(network_lat_pm_qos.requirements.list)},
	.notifiers = &network_lat_notifier,
	.name = "network_latency",
	.default_value = 2000 * USEC_PER_SEC,
	.target_value = 2000 * USEC_PER_SEC,
	.comparitor = min_compare
	};


	static BLOCKING_NOTIFIER_HEAD(network_throughput_notifier);
	static struct pm_qos_object network_throughput_pm_qos = {
	.requirements =
	{LIST_HEAD_INIT(network_throughput_pm_qos.requirements.list)},
	.notifiers = &network_throughput_notifier,
	.name = "network_throughput",
	.default_value = 0,
	.target_value = 0,
	.comparitor = max_compare
	};


	static struct pm_qos_object *pm_qos_array[] = {
	&null_pm_qos,
	&cpu_dma_pm_qos,
	&network_lat_pm_qos,
	&network_throughput_pm_qos
	};

	static DEFINE_SPINLOCK(pm_qos_lock);

	static ssize_t pm_qos_power_write(struct file filp, const char __user buf,
	size_t count, loff_t *f_pos);
	static int pm_qos_power_open(struct inode inode, struct file filp);
	static int pm_qos_power_release(struct inode inode, struct file filp);

	static const struct file_operations pm_qos_power_fops = {
	.write = pm_qos_power_write,
	.open = pm_qos_power_open,
	.release = pm_qos_power_release,
	};

	/* static helper functions */
	static s32 max_compare(s32 v1, s32 v2)
	{
	return max(v1, v2);
	}

	static s32 min_compare(s32 v1, s32 v2)
	{
	return min(v1, v2);
	}


	static void update_target(int target)
	{
	s32 extreme_value;
	struct requirement_list *node;
	unsigned long flags;
	int call_notifier = 0;

	spin_lock_irqsave(&pm_qos_lock, flags);
	extreme_value = pm_qos_array[target]->default_value;
	list_for_each_entry(node,
	&pm_qos_array[target]->requirements.list, list) {
	extreme_value = pm_qos_array[target]->comparitor(
	extreme_value, node->value);
	}
	if (pm_qos_array[target]->target_value != extreme_value) {
	call_notifier = 1;
	pm_qos_array[target]->target_value = extreme_value;
	pr_debug(KERN_ERR "new target for qos %d is %d\n", target,
	pm_qos_array[target]->target_value);
	}
	spin_unlock_irqrestore(&pm_qos_lock, flags);

	if (call_notifier)
	blocking_notifier_call_chain(pm_qos_array[target]->notifiers,
	(unsigned long) extreme_value, NULL);
	}

	static int register_pm_qos_misc(struct pm_qos_object *qos)
	{
	qos->pm_qos_power_miscdev.minor = MISC_DYNAMIC_MINOR;
	qos->pm_qos_power_miscdev.name = qos->name;
	qos->pm_qos_power_miscdev.fops = &pm_qos_power_fops;

	return misc_register(&qos->pm_qos_power_miscdev);
	}

	static int find_pm_qos_object_by_minor(int minor)
	{
	int pm_qos_class;

	for (pm_qos_class = 0;
	pm_qos_class < PM_QOS_NUM_CLASSES; pm_qos_class++) {
	if (minor ==
	pm_qos_array[pm_qos_class]->pm_qos_power_miscdev.minor)
	return pm_qos_class;
	}
	return -1;
	}

	/**
	* pm_qos_requirement - returns current system wide qos expectation
	* @pm_qos_class: identification of which qos value is requested
	*
	* This function returns the current target value in an atomic manner.
	*/
	int pm_qos_requirement(int pm_qos_class)
	{
	int ret_val;
	unsigned long flags;

	spin_lock_irqsave(&pm_qos_lock, flags);
	ret_val = pm_qos_array[pm_qos_class]->target_value;
	spin_unlock_irqrestore(&pm_qos_lock, flags);

	return ret_val;
	}
	EXPORT_SYMBOL_GPL(pm_qos_requirement);

	/**
	* pm_qos_add_requirement - inserts new qos request into the list
	* @pm_qos_class: identifies which list of qos request to us
	* @name: identifies the request
	* @value: defines the qos request
	*
	* This function inserts a new entry in the pm_qos_class list of requested qos
	* performance charactoistics. It recomputes the agregate QoS expectations for
	* the pm_qos_class of parrameters.
	*/
	int pm_qos_add_requirement(int pm_qos_class, char *name, s32 value)
	{
	struct requirement_list *dep;
	unsigned long flags;

	dep = kzalloc(sizeof(struct requirement_list), GFP_KERNEL);
	if (dep) {
	if (value == PM_QOS_DEFAULT_VALUE)
	dep->value = pm_qos_array[pm_qos_class]->default_value;
	else
	dep->value = value;
	dep->name = kstrdup(name, GFP_KERNEL);
	if (!dep->name)
	goto cleanup;

	spin_lock_irqsave(&pm_qos_lock, flags);
	list_add(&dep->list,
	&pm_qos_array[pm_qos_class]->requirements.list);
	spin_unlock_irqrestore(&pm_qos_lock, flags);
	update_target(pm_qos_class);

	return 0;
	}

	cleanup:
	kfree(dep);
	return -ENOMEM;
	}
	EXPORT_SYMBOL_GPL(pm_qos_add_requirement);

	/**
	* pm_qos_update_requirement - modifies an existing qos request
	* @pm_qos_class: identifies which list of qos request to us
	* @name: identifies the request
	* @value: defines the qos request
	*
	* Updates an existing qos requierement for the pm_qos_class of parameters along
	* with updating the target pm_qos_class value.
	*
	* If the named request isn't in the lest then no change is made.
	*/
	int pm_qos_update_requirement(int pm_qos_class, char *name, s32 new_value)
	{
	unsigned long flags;
	struct requirement_list *node;
	int pending_update = 0;

	spin_lock_irqsave(&pm_qos_lock, flags);
	list_for_each_entry(node,
	&pm_qos_array[pm_qos_class]->requirements.list, list) {
	if (strcmp(node->name, name) == 0) {
	if (new_value == PM_QOS_DEFAULT_VALUE)
	node->value =
	pm_qos_array[pm_qos_class]->default_value;
	else
	node->value = new_value;
	pending_update = 1;
	break;
	}
	}
	spin_unlock_irqrestore(&pm_qos_lock, flags);
	if (pending_update)
	update_target(pm_qos_class);

	return 0;
	}
	EXPORT_SYMBOL_GPL(pm_qos_update_requirement);

	/**
	* pm_qos_remove_requirement - modifies an existing qos request
	* @pm_qos_class: identifies which list of qos request to us
	* @name: identifies the request
	*
	* Will remove named qos request from pm_qos_class list of parrameters and
	* recompute the current target value for the pm_qos_class.
	*/
	void pm_qos_remove_requirement(int pm_qos_class, char *name)
	{
	unsigned long flags;
	struct requirement_list *node;
	int pending_update = 0;

	spin_lock_irqsave(&pm_qos_lock, flags);
	list_for_each_entry(node,
	&pm_qos_array[pm_qos_class]->requirements.list, list) {
	if (strcmp(node->name, name) == 0) {
	kfree(node->name);
	list_del(&node->list);
	kfree(node);
	pending_update = 1;
	break;
	}
	}
	spin_unlock_irqrestore(&pm_qos_lock, flags);
	if (pending_update)
	update_target(pm_qos_class);
	}
	EXPORT_SYMBOL_GPL(pm_qos_remove_requirement);

	/**
	* pm_qos_add_notifier - sets notification entry for changes to target value
	* @pm_qos_class: identifies which qos target changes should be notified.
	* @notifier: notifier block managed by caller.
	*
	* will register the notifier into a notification chain that gets called
	* uppon changes to the pm_qos_class target value.
	*/
	int pm_qos_add_notifier(int pm_qos_class, struct notifier_block *notifier)
	{
	int retval;

	retval = blocking_notifier_chain_register(
	pm_qos_array[pm_qos_class]->notifiers, notifier);

	return retval;
	}
	EXPORT_SYMBOL_GPL(pm_qos_add_notifier);

	/**
	* pm_qos_remove_notifier - deletes notification entry from chain.
	* @pm_qos_class: identifies which qos target changes are notified.
	* @notifier: notifier block to be removed.
	*
	* will remove the notifier from the notification chain that gets called
	* uppon changes to the pm_qos_class target value.
	*/
	int pm_qos_remove_notifier(int pm_qos_class, struct notifier_block *notifier)
	{
	int retval;

	retval = blocking_notifier_chain_unregister(
	pm_qos_array[pm_qos_class]->notifiers, notifier);

	return retval;
	}
	EXPORT_SYMBOL_GPL(pm_qos_remove_notifier);

	#define PID_NAME_LEN sizeof("process_1234567890")
	static char name[PID_NAME_LEN];

	static int pm_qos_power_open(struct inode inode, struct file filp)
	{
	int ret;
	long pm_qos_class;

	pm_qos_class = find_pm_qos_object_by_minor(iminor(inode));
	if (pm_qos_class >= 0) {
	filp->private_data = (void *)pm_qos_class;
	sprintf(name, "process_%d", current->pid);
	ret = pm_qos_add_requirement(pm_qos_class, name,
	PM_QOS_DEFAULT_VALUE);
	if (ret >= 0)
	return 0;
	}

	return -EPERM;
	}

	static int pm_qos_power_release(struct inode inode, struct file filp)
	{
	int pm_qos_class;

	pm_qos_class = (long)filp->private_data;
	sprintf(name, "process_%d", current->pid);
	pm_qos_remove_requirement(pm_qos_class, name);

	return 0;
	}

	static ssize_t pm_qos_power_write(struct file filp, const char __user buf,
	size_t count, loff_t *f_pos)
	{
	s32 value;
	int pm_qos_class;

	pm_qos_class = (long)filp->private_data;
	if (count != sizeof(s32))
	return -EINVAL;
	if (copy_from_user(&value, buf, sizeof(s32)))
	return -EFAULT;
	sprintf(name, "process_%d", current->pid);
	pm_qos_update_requirement(pm_qos_class, name, value);

	return sizeof(s32);
	}


	static int __init pm_qos_power_init(void)
	{
	int ret = 0;

	ret = register_pm_qos_misc(&cpu_dma_pm_qos);
	if (ret < 0) {
	printk(KERN_ERR "pm_qos_param: cpu_dma_latency setup failed\n");
	return ret;
	}
	ret = register_pm_qos_misc(&network_lat_pm_qos);
	if (ret < 0) {
	printk(KERN_ERR "pm_qos_param: network_latency setup failed\n");
	return ret;
	}
	ret = register_pm_qos_misc(&network_throughput_pm_qos);
	if (ret < 0)
	printk(KERN_ERR
	"pm_qos_param: network_throughput setup failed\n");

	return ret;
	}

	late_initcall(pm_qos_power_init);