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         if (cpuidle_disabled())
  30                 return -ENODEV;
  31
  32         spin_lock(&cpuidle_driver_lock);
  33         if (cpuidle_curr_driver) {
  34                 spin_unlock(&cpuidle_driver_lock);
  35                 return -EBUSY;
  36         }
  37         cpuidle_curr_driver = drv;
  38         spin_unlock(&cpuidle_driver_lock);
  39
  40         return 0;
  41 }
  42
  43 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
  44
  45 /**
  46  * cpuidle_get_driver - return the current driver
  47  */
  48 struct cpuidle_driver *cpuidle_get_driver(void)
  49 {
  50         return cpuidle_curr_driver;
  51 }
  52 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
  53
  54 /**
  55  * cpuidle_unregister_driver - unregisters a driver
  56  * @drv: the driver
  57  */
  58 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
  59 {
  60         if (drv != cpuidle_curr_driver) {
  61                 WARN(1, "invalid cpuidle_unregister_driver(%s)\n",
  62                         drv->name);
  63                 return;
  64         }
  65
  66         spin_lock(&cpuidle_driver_lock);
  67         cpuidle_curr_driver = NULL;
  68         spin_unlock(&cpuidle_driver_lock);
  69 }
  70
  71 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);