/*
 * driver.c - driver support
 *
 * (C) 2006-2007 Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
 *               Shaohua Li <shaohua.li@intel.com>
 *               Adam Belay <abelay@novell.com>
 *
 * This code is licenced under the GPL.
 */

#include <linux/mutex.h>
#include <linux/module.h>
#include <linux/cpuidle.h>

#include "cpuidle.h"

static struct cpuidle_driver *cpuidle_curr_driver;
DEFINE_SPINLOCK(cpuidle_driver_lock);
int cpuidle_driver_refcount;

/**
 * cpuidle_register_driver - registers a driver
 * @drv: the driver
 */
int cpuidle_register_driver(struct cpuidle_driver *drv)
{
	if (!drv)
		return -EINVAL;

	if (cpuidle_disabled())
		return -ENODEV;

	spin_lock(&cpuidle_driver_lock);
	if (cpuidle_curr_driver) {
		spin_unlock(&cpuidle_driver_lock);
		return -EBUSY;
	}
	cpuidle_curr_driver = drv;
	spin_unlock(&cpuidle_driver_lock);

	return 0;
}

EXPORT_SYMBOL_GPL(cpuidle_register_driver);

/**
 * cpuidle_get_driver - return the current driver
 */
struct cpuidle_driver *cpuidle_get_driver(void)
{
	return cpuidle_curr_driver;
}
EXPORT_SYMBOL_GPL(cpuidle_get_driver);

/**
 * cpuidle_unregister_driver - unregisters a driver
 * @drv: the driver
 */
void cpuidle_unregister_driver(struct cpuidle_driver *drv)
{
	if (drv != cpuidle_curr_driver) {
		WARN(1, "invalid cpuidle_unregister_driver(%s)\n",
			drv->name);
		return;
	}

	spin_lock(&cpuidle_driver_lock);

	if (!WARN_ON(cpuidle_driver_refcount > 0))
		cpuidle_curr_driver = NULL;

	spin_unlock(&cpuidle_driver_lock);
}

EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);

struct cpuidle_driver *cpuidle_driver_ref(void)
{
	struct cpuidle_driver *drv;

	spin_lock(&cpuidle_driver_lock);

	drv = cpuidle_curr_driver;
	cpuidle_driver_refcount++;

	spin_unlock(&cpuidle_driver_lock);
	return drv;
}

void cpuidle_driver_unref(void)
{
	spin_lock(&cpuidle_driver_lock);

	if (!WARN_ON(cpuidle_driver_refcount <= 0))
		cpuidle_driver_refcount--;

	spin_unlock(&cpuidle_driver_lock);
}