1/*
2 * governor.c - governor support
3 *
4 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
5 *               Shaohua Li <shaohua.li@intel.com>
6 *               Adam Belay <abelay@novell.com>
7 *
8 * This code is licenced under the GPL.
9 */
10
11#include <linux/mutex.h>
12#include <linux/module.h>
13#include <linux/cpuidle.h>
14
15#include "cpuidle.h"
16
17LIST_HEAD(cpuidle_governors);
18struct cpuidle_governor *cpuidle_curr_governor;
19
20/**
21 * __cpuidle_find_governor - finds a governor of the specified name
22 * @str: the name
23 *
24 * Must be called with cpuidle_lock acquired.
25 */
26static struct cpuidle_governor * __cpuidle_find_governor(const char *str)
27{
28	struct cpuidle_governor *gov;
29
30	list_for_each_entry(gov, &cpuidle_governors, governor_list)
31		if (!strncasecmp(str, gov->name, CPUIDLE_NAME_LEN))
32			return gov;
33
34	return NULL;
35}
36
37/**
38 * cpuidle_switch_governor - changes the governor
39 * @gov: the new target governor
40 *
41 * NOTE: "gov" can be NULL to specify disabled
42 * Must be called with cpuidle_lock acquired.
43 */
44int cpuidle_switch_governor(struct cpuidle_governor *gov)
45{
46	struct cpuidle_device *dev;
47
48	if (gov == cpuidle_curr_governor)
49		return 0;
50
51	cpuidle_uninstall_idle_handler();
52
53	if (cpuidle_curr_governor) {
54		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
55			cpuidle_disable_device(dev);
56		module_put(cpuidle_curr_governor->owner);
57	}
58
59	cpuidle_curr_governor = gov;
60
61	if (gov) {
62		if (!try_module_get(cpuidle_curr_governor->owner))
63			return -EINVAL;
64		list_for_each_entry(dev, &cpuidle_detected_devices, device_list)
65			cpuidle_enable_device(dev);
66		cpuidle_install_idle_handler();
67		printk(KERN_INFO "cpuidle: using governor %s\n", gov->name);
68	}
69
70	return 0;
71}
72
73/**
74 * cpuidle_register_governor - registers a governor
75 * @gov: the governor
76 */
77int cpuidle_register_governor(struct cpuidle_governor *gov)
78{
79	int ret = -EEXIST;
80
81	if (!gov || !gov->select)
82		return -EINVAL;
83
84	if (cpuidle_disabled())
85		return -ENODEV;
86
87	mutex_lock(&cpuidle_lock);
88	if (__cpuidle_find_governor(gov->name) == NULL) {
89		ret = 0;
90		list_add_tail(&gov->governor_list, &cpuidle_governors);
91		if (!cpuidle_curr_governor ||
92		    cpuidle_curr_governor->rating < gov->rating)
93			cpuidle_switch_governor(gov);
94	}
95	mutex_unlock(&cpuidle_lock);
96
97	return ret;
98}
99