driver.c
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/*
* 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;
static void set_power_states(struct cpuidle_driver *drv)
{
int i;
/*
* cpuidle driver should set the drv->power_specified bit
* before registering if the driver provides
* power_usage numbers.
*
* If power_specified is not set,
* we fill in power_usage with decreasing values as the
* cpuidle code has an implicit assumption that state Cn
* uses less power than C(n-1).
*
* With CONFIG_ARCH_HAS_CPU_RELAX, C0 is already assigned
* an power value of -1. So we use -2, -3, etc, for other
* c-states.
*/
for (i = CPUIDLE_DRIVER_STATE_START; i < drv->state_count; i++)
drv->states[i].power_usage = -1 - i;
}
/**
* cpuidle_register_driver - registers a driver
* @drv: the driver
*/
int cpuidle_register_driver(struct cpuidle_driver *drv)
{
if (!drv || !drv->state_count)
return -EINVAL;
if (cpuidle_disabled())
return -ENODEV;
spin_lock(&cpuidle_driver_lock);
if (cpuidle_curr_driver) {
spin_unlock(&cpuidle_driver_lock);
return -EBUSY;
}
if (!drv->power_specified)
set_power_states(drv);
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);
}