cpuidle: Comment the driver's framework code
Add kerneldoc (and other) comments to the cpuidle driver's framework
code.
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index e75fa54..3ac499d 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -22,11 +22,26 @@
static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
+/**
+ * __cpuidle_get_cpu_driver - return the cpuidle driver tied to a CPU.
+ * @cpu: the CPU handled by the driver
+ *
+ * Returns a pointer to struct cpuidle_driver or NULL if no driver has been
+ * registered for @cpu.
+ */
static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
{
return per_cpu(cpuidle_drivers, cpu);
}
+/**
+ * __cpuidle_unset_driver - unset per CPU driver variables.
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * For each CPU in the driver's CPU mask, unset the registered driver per CPU
+ * variable. If @drv is different from the registered driver, the corresponding
+ * variable is not cleared.
+ */
static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
{
int cpu;
@@ -40,6 +55,15 @@
}
}
+/**
+ * __cpuidle_set_driver - set per CPU driver variables the the given driver.
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * For each CPU in the driver's cpumask, unset the registered driver per CPU
+ * to @drv.
+ *
+ * Returns 0 on success, -EBUSY if the CPUs have driver(s) already.
+ */
static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
{
int cpu;
@@ -61,11 +85,24 @@
static struct cpuidle_driver *cpuidle_curr_driver;
+/**
+ * __cpuidle_get_cpu_driver - return the global cpuidle driver pointer.
+ * @cpu: ignored without the multiple driver support
+ *
+ * Return a pointer to a struct cpuidle_driver object or NULL if no driver was
+ * previously registered.
+ */
static inline struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
{
return cpuidle_curr_driver;
}
+/**
+ * __cpuidle_set_driver - assign the global cpuidle driver variable.
+ * @drv: pointer to a struct cpuidle_driver object
+ *
+ * Returns 0 on success, -EBUSY if the driver is already registered.
+ */
static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
{
if (cpuidle_curr_driver)
@@ -76,6 +113,13 @@
return 0;
}
+/**
+ * __cpuidle_unset_driver - unset the global cpuidle driver variable.
+ * @drv: a pointer to a struct cpuidle_driver
+ *
+ * Reset the global cpuidle variable to NULL. If @drv does not match the
+ * registered driver, do nothing.
+ */
static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
{
if (drv == cpuidle_curr_driver)
@@ -84,21 +128,49 @@
#endif
+/**
+ * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer
+ * @arg: a void pointer used to match the SMP cross call API
+ *
+ * @arg is used as a value of type 'long' with on of the two values:
+ * - CLOCK_EVT_NOTIFY_BROADCAST_ON
+ * - CLOCK_EVT_NOTIFY_BROADCAST_OFF
+ *
+ * Set the broadcast timer notification for the current CPU. This function
+ * is executed per CPU by an SMP cross call. It not supposed to be called
+ * directly.
+ */
static void cpuidle_setup_broadcast_timer(void *arg)
{
int cpu = smp_processor_id();
clockevents_notify((long)(arg), &cpu);
}
+/**
+ * __cpuidle_driver_init - initialize the driver's internal data
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * Returns 0 on success, a negative error code otherwise.
+ */
static int __cpuidle_driver_init(struct cpuidle_driver *drv)
{
int i;
drv->refcnt = 0;
+ /*
+ * Use all possible CPUs as the default, because if the kernel boots
+ * with some CPUs offline and then we online one of them, the CPU
+ * notifier has to know which driver to assign.
+ */
if (!drv->cpumask)
drv->cpumask = (struct cpumask *)cpu_possible_mask;
+ /*
+ * Look for the timer stop flag in the different states, so that we know
+ * if the broadcast timer has to be set up. The loop is in the reverse
+ * order, because usually on of the the deeper states has this flag set.
+ */
for (i = drv->state_count - 1; i >= 0 ; i--) {
if (!(drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP))
@@ -111,6 +183,19 @@
return 0;
}
+/**
+ * __cpuidle_register_driver: register the driver
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * Do some sanity checks, initialize the driver, assign the driver to the
+ * global cpuidle driver variable(s) and set up the broadcast timer if the
+ * cpuidle driver has some states that shut down the local timer.
+ *
+ * Returns 0 on success, a negative error code otherwise:
+ * * -EINVAL if the driver pointer is NULL or no idle states are available
+ * * -ENODEV if the cpuidle framework is disabled
+ * * -EBUSY if the driver is already assigned to the global variable(s)
+ */
static int __cpuidle_register_driver(struct cpuidle_driver *drv)
{
int ret;
@@ -137,8 +222,13 @@
}
/**
- * cpuidle_unregister_driver - unregisters a driver
- * @drv: the driver
+ * __cpuidle_unregister_driver - unregister the driver
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * Check if the driver is no longer in use, reset the global cpuidle driver
+ * variable(s) and disable the timer broadcast notification mechanism if it was
+ * in use.
+ *
*/
static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
{
@@ -156,7 +246,13 @@
/**
* cpuidle_register_driver - registers a driver
- * @drv: the driver
+ * @drv: a pointer to a valid struct cpuidle_driver
+ *
+ * Register the driver under a lock to prevent concurrent attempts to
+ * [un]register the driver from occuring at the same time.
+ *
+ * Returns 0 on success, a negative error code (returned by
+ * __cpuidle_register_driver()) otherwise.
*/
int cpuidle_register_driver(struct cpuidle_driver *drv)
{
@@ -172,7 +268,11 @@
/**
* cpuidle_unregister_driver - unregisters a driver
- * @drv: the driver
+ * @drv: a pointer to a valid struct cpuidle_driver
+ *
+ * Unregisters the cpuidle driver under a lock to prevent concurrent attempts
+ * to [un]register the driver from occuring at the same time. @drv has to
+ * match the currently registered driver.
*/
void cpuidle_unregister_driver(struct cpuidle_driver *drv)
{
@@ -183,7 +283,9 @@
EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
/**
- * cpuidle_get_driver - return the current driver
+ * cpuidle_get_driver - return the driver tied to the current CPU.
+ *
+ * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered.
*/
struct cpuidle_driver *cpuidle_get_driver(void)
{
@@ -199,7 +301,11 @@
EXPORT_SYMBOL_GPL(cpuidle_get_driver);
/**
- * cpuidle_get_cpu_driver - return the driver tied with a cpu
+ * cpuidle_get_cpu_driver - return the driver registered for a CPU.
+ * @dev: a valid pointer to a struct cpuidle_device
+ *
+ * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
+ * for the CPU associated with @dev.
*/
struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
{
@@ -210,6 +316,14 @@
}
EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
+/**
+ * cpuidle_driver_ref - get a reference to the driver.
+ *
+ * Increment the reference counter of the cpuidle driver associated with
+ * the current CPU.
+ *
+ * Returns a pointer to the driver, or NULL if the current CPU has no driver.
+ */
struct cpuidle_driver *cpuidle_driver_ref(void)
{
struct cpuidle_driver *drv;
@@ -223,6 +337,12 @@
return drv;
}
+/**
+ * cpuidle_driver_unref - puts down the refcount for the driver
+ *
+ * Decrement the reference counter of the cpuidle driver associated with
+ * the current CPU.
+ */
void cpuidle_driver_unref(void)
{
struct cpuidle_driver *drv = cpuidle_get_driver();