release/src-rt-6.x.4708/linux/linux-2.6.36/drivers/cpuidle/driver.c

   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
  17 static struct cpuidle_driver *cpuidle_curr_driver;
  18 DEFINE_SPINLOCK(cpuidle_driver_lock);
  19
  20 /**
  21  * cpuidle_register_driver - registers a driver
  22  * @drv: the driver
  23  */
  24 int cpuidle_register_driver(struct cpuidle_driver *drv)
  25 {
  26         if (!drv)
  27                 return -EINVAL;
  28
  29         spin_lock(&cpuidle_driver_lock);
  30         if (cpuidle_curr_driver) {
  31                 spin_unlock(&cpuidle_driver_lock);
  32                 return -EBUSY;
  33         }
  34         cpuidle_curr_driver = drv;
  35         spin_unlock(&cpuidle_driver_lock);
  36
  37         return 0;
  38 }
  39
  40 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
  41
  42 /**
  43  * cpuidle_get_driver - return the current driver
  44  */
  45 struct cpuidle_driver *cpuidle_get_driver(void)
  46 {
  47         return cpuidle_curr_driver;
  48 }
  49 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
  50
  51 /**
  52  * cpuidle_unregister_driver - unregisters a driver
  53  * @drv: the driver
  54  */
  55 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
  56 {
  57         if (drv != cpuidle_curr_driver) {
  58                 WARN(1, "invalid cpuidle_unregister_driver(%s)\n",
  59                         drv->name);
  60                 return;
  61         }
  62
  63         spin_lock(&cpuidle_driver_lock);
  64         cpuidle_curr_driver = NULL;
  65         spin_unlock(&cpuidle_driver_lock);
  66 }
  67
  68 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);