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/*
* governor.c - governor support
*
* (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
* Shaohua Li <shaohua.li@intel.com>
* Adam Belay <abelay@novell.com>
*
* This code is licenced under the GPL.
*/
#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/cpuidle.h>
#include "cpuidle.h"
LIST_HEAD(cpuidle_governors);
struct cpuidle_governor *cpuidle_curr_governor;
/**
* __cpuidle_find_governor - finds a governor of the specified name
* @str: the name
*
* Must be called with cpuidle_lock acquired.
*/
static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
{
struct cpuidle_governor *gov;
list_for_each_entry(gov, &cpuidle_governors, governor_list)
if (!strnicmp(str, gov->name, CPUIDLE_NAME_LEN))
return gov;
return NULL;
}
/**
* cpuidle_switch_governor - changes the governor
* @gov: the new target governor
*
* NOTE: "gov" can be NULL to specify disabled
* Must be called with cpuidle_lock acquired.
*/
int cpuidle_switch_governor(struct cpuidle_governor *gov)
{
struct cpuidle_device *dev;
if (gov == cpuidle_curr_governor)
return 0;
cpuidle_uninstall_idle_handler();
if (cpuidle_curr_governor) {
list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
cpuidle_disable_device(dev);
module_put(cpuidle_curr_governor->owner);
}
cpuidle_curr_governor = gov;
if (gov) {
if (!try_module_get(cpuidle_curr_governor->owner))
return -EINVAL;
list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
cpuidle_enable_device(dev);
cpuidle_install_idle_handler();
printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
}
return 0;
}
/**
* cpuidle_register_governor - registers a governor
* @gov: the governor
*/
int cpuidle_register_governor(struct cpuidle_governor *gov)
{
int ret = -EEXIST;
if (!gov || !gov->select)
return -EINVAL;
mutex_lock(&cpuidle_lock);
if (__cpuidle_find_governor(gov->name) == NULL) {
ret = 0;
list_add_tail(&gov->governor_list, &cpuidle_governors);
if (!cpuidle_curr_governor ||
cpuidle_curr_governor->rating < gov->rating)
cpuidle_switch_governor(gov);
}
mutex_unlock(&cpuidle_lock);
return ret;
}
/**
* cpuidle_replace_governor - find a replacement governor
* @exclude_rating: the rating that will be skipped while looking for
* new governor.
*/
static struct cpuidle_governor *cpuidle_replace_governor(int exclude_rating)
{
struct cpuidle_governor *gov;
struct cpuidle_governor *ret_gov = NULL;
unsigned int max_rating = 0;
list_for_each_entry(gov, &cpuidle_governors, governor_list) {
if (gov->rating == exclude_rating)
continue;
if (gov->rating > max_rating) {
max_rating = gov->rating;
ret_gov = gov;
}
}
return ret_gov;
}
/**
* cpuidle_unregister_governor - unregisters a governor
* @gov: the governor
*/
void cpuidle_unregister_governor(struct cpuidle_governor *gov)
{
if (!gov)
return;
mutex_lock(&cpuidle_lock);
if (gov == cpuidle_curr_governor) {
struct cpuidle_governor *new_gov;
new_gov = cpuidle_replace_governor(gov->rating);
cpuidle_switch_governor(new_gov);
}
list_del(&gov->governor_list);
mutex_unlock(&cpuidle_lock);
}
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