Linux kernel mirror (for testing)
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linux
1/*
2 * driver.c - driver 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
17static struct cpuidle_driver *cpuidle_curr_driver;
18DEFINE_SPINLOCK(cpuidle_driver_lock);
19
20static void __cpuidle_register_driver(struct cpuidle_driver *drv)
21{
22 int i;
23 /*
24 * cpuidle driver should set the drv->power_specified bit
25 * before registering if the driver provides
26 * power_usage numbers.
27 *
28 * If power_specified is not set,
29 * we fill in power_usage with decreasing values as the
30 * cpuidle code has an implicit assumption that state Cn
31 * uses less power than C(n-1).
32 *
33 * With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
34 * an power value of -1. So we use -2, -3, etc, for other
35 * c-states.
36 */
37 if (!drv->power_specified) {
38 for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++)
39 drv->states[i].power_usage = -1 - i;
40 }
41}
42
43
44/**
45 * cpuidle_register_driver - registers a driver
46 * @drv: the driver
47 */
48int cpuidle_register_driver(struct cpuidle_driver *drv)
49{
50 if (!drv)
51 return -EINVAL;
52
53 if (cpuidle_disabled())
54 return -ENODEV;
55
56 spin_lock(&cpuidle_driver_lock);
57 if (cpuidle_curr_driver) {
58 spin_unlock(&cpuidle_driver_lock);
59 return -EBUSY;
60 }
61 __cpuidle_register_driver(drv);
62 cpuidle_curr_driver = drv;
63 spin_unlock(&cpuidle_driver_lock);
64
65 return 0;
66}
67
68EXPORT_SYMBOL_GPL(cpuidle_register_driver);
69
70/**
71 * cpuidle_get_driver - return the current driver
72 */
73struct cpuidle_driver *cpuidle_get_driver(void)
74{
75 return cpuidle_curr_driver;
76}
77EXPORT_SYMBOL_GPL(cpuidle_get_driver);
78
79/**
80 * cpuidle_unregister_driver - unregisters a driver
81 * @drv: the driver
82 */
83void cpuidle_unregister_driver(struct cpuidle_driver *drv)
84{
85 if (drv != cpuidle_curr_driver) {
86 WARN(1, "invalid cpuidle_unregister_driver(%s)\n",
87 drv->name);
88 return;
89 }
90
91 spin_lock(&cpuidle_driver_lock);
92 cpuidle_curr_driver = NULL;
93 spin_unlock(&cpuidle_driver_lock);
94}
95
96EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);