governor.c

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/*
 * governor.c - governor support
 *
 * (C) 2006-2007 Venkatesh Pallipadi <[email protected]>
 *               Shaohua Li <[email protected]>
 *               Adam Belay <[email protected]>
 *
 * 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;

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;
}

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;
}

int cpuidle_register_governor(struct cpuidle_governor *gov)
{
    int ret = -EEXIST;

    if (!gov || !gov->select)
        return -EINVAL;

    if (cpuidle_disabled())
        return -ENODEV;

    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;
}

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;
}

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);
}