PNPBIOS: remove include/linux/pnpbios.h
[linux-2.6.git] / drivers / cpuidle / governor.c
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
17 LIST_HEAD(cpuidle_governors);
18 struct 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 aquired.
25  */
26 static 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 (!strnicmp(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 aquired.
43  */
44 int 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  */
77 int cpuidle_register_governor(struct cpuidle_governor *gov)
78 {
79         int ret = -EEXIST;
80
81         if (!gov || !gov->select)
82                 return -EINVAL;
83
84         mutex_lock(&cpuidle_lock);
85         if (__cpuidle_find_governor(gov->name) == NULL) {
86                 ret = 0;
87                 list_add_tail(&gov->governor_list, &cpuidle_governors);
88                 if (!cpuidle_curr_governor ||
89                     cpuidle_curr_governor->rating < gov->rating)
90                         cpuidle_switch_governor(gov);
91         }
92         mutex_unlock(&cpuidle_lock);
93
94         return ret;
95 }
96
97 /**
98  * cpuidle_replace_governor - find a replacement governor
99  * @exclude_rating: the rating that will be skipped while looking for
100  * new governor.
101  */
102 static struct cpuidle_governor *cpuidle_replace_governor(int exclude_rating)
103 {
104         struct cpuidle_governor *gov;
105         struct cpuidle_governor *ret_gov = NULL;
106         unsigned int max_rating = 0;
107
108         list_for_each_entry(gov, &cpuidle_governors, governor_list) {
109                 if (gov->rating == exclude_rating)
110                         continue;
111                 if (gov->rating > max_rating) {
112                         max_rating = gov->rating;
113                         ret_gov = gov;
114                 }
115         }
116
117         return ret_gov;
118 }
119
120 /**
121  * cpuidle_unregister_governor - unregisters a governor
122  * @gov: the governor
123  */
124 void cpuidle_unregister_governor(struct cpuidle_governor *gov)
125 {
126         if (!gov)
127                 return;
128
129         mutex_lock(&cpuidle_lock);
130         if (gov == cpuidle_curr_governor) {
131                 struct cpuidle_governor *new_gov;
132                 new_gov = cpuidle_replace_governor(gov->rating);
133                 cpuidle_switch_governor(new_gov);
134         }
135         list_del(&gov->governor_list);
136         mutex_unlock(&cpuidle_lock);
137 }
138