[PATCH V4 2/2] cpuidle: Comment the driver's framework code

[Daniel Lezcano <daniel.lezcano@linaro.org>]

Added kerneldoc and comments for the cpuidle framework driver's code.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
[V4]
 - fixed kerneldoc comment format

 drivers/cpuidle/driver.c |  134 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 128 insertions(+), 6 deletions(-)

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index e75fa54..4cc5bc4 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -22,11 +22,26 @@ DEFINE_SPINLOCK(cpuidle_driver_lock);
 
 static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
 
+/**
+ * __cpuidle_get_cpu_driver - returns the cpuidle driver tied with a cpu
+ * @cpu: the cpu handled by the driver
+ *
+ * Returns a pointer to struct cpuidle_driver, NULL if no driver has been
+ * registered for this driver
+ */
 static struct cpuidle_driver *__cpuidle_get_cpu_driver(int cpu)
 {
 	return per_cpu(cpuidle_drivers, cpu);
 }
 
+/**
+ * __cpuidle_unset_driver - set the per cpu variable driver to NULL.
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * For each cpu belonging to the driver's cpu mask, set the registered
+ * driver to NULL. If the specified driver is different from the registered
+ * one, the registered driver is untouched.
+ */
 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 {
 	int cpu;
@@ -40,6 +55,15 @@ static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 	}
 }
 
+/**
+ * __cpuidle_set_driver - assign to the per cpu variable the driver pointer
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * For each cpus handled by the driver, belonging to the driver's cpumask,
+ * assign to the per cpu variable the driver pointer
+ *
+ * Returns 0 on success, -EBUSY if a driver was already assigned to a cpu.
+ */
 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 {
 	int cpu;
@@ -61,11 +85,24 @@ static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 
 static struct cpuidle_driver *cpuidle_curr_driver;
 
+/**
+ * __cpuidle_get_cpu_driver - returns the global cpuidle driver pointer.
+ * @cpu: this parameter is ignored without the multiple driver support
+ *
+ * Returns a pointer to a struct cpuidle_driver, 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: a pointer to a struct cpuidle_driver
+ *
+ * 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 @@ static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 	return 0;
 }
 
+/**
+ * __cpuidle_unset_driver - reset the global cpuidle driver variable
+ * @drv: a pointer to a struct cpuidle_driver
+ *
+ * Sets the global cpuidle variable to NULL, if the specified driver
+ * does not match the registered driver, the function will have no effect.
+ */
 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 {
 	if (drv == cpuidle_curr_driver)
@@ -84,21 +128,49 @@ static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 
 #endif
 
+/**
+ * cpuidle_setup_broadcast_timer - enable/disable the broadcast timer
+ * @arg: a void pointer, actually used to match the smp cross call api but used
+ * as a long with two values:
+ * - CLOCK_EVT_NOTIFY_BROADCAST_ON
+ * - CLOCK_EVT_NOTIFY_BROADCAST_OFF
+ *
+ * Sets the broadcast timer notification for the current cpu. This function
+ * is called per cpu context invoked by a 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 otherwise.
+ */
 static int __cpuidle_driver_init(struct cpuidle_driver *drv)
 {
 	int i;
 
 	drv->refcnt = 0;
 
+	/*
+	 * we default here to all cpu possible because if the kernel
+	 * boots with some cpus offline and then we online one of them
+	 * the cpu notifier won't know which driver to assign
+	 */
 	if (!drv->cpumask)
 		drv->cpumask = (struct cpumask *)cpu_possible_mask;
 
+	/*
+	 * we look for the timer stop flag in the different states,
+	 * so know we have to setup the broadcast timer. The loop is
+	 * in reverse order, because usually the deeper state has this
+	 * flag set
+	 */
 	for (i = drv->state_count - 1; i >= 0 ; i--) {
 
 		if (!(drv->states[i].flags & CPUIDLE_FLAG_TIMER_STOP))
@@ -111,6 +183,21 @@ static int __cpuidle_driver_init(struct cpuidle_driver *drv)
 	return 0;
 }
 
+/**
+ * __cpuidle_register_driver: registers the driver
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * Does some sanity checks, initializes the driver, assigns the driver
+ * to the global cpuidle driver variable(s) and setup the broadcast
+ * timer if the cpuidle driver has some states which shutdown the
+ * local timer.
+ *
+ * Returns 0 on success, a negative error otherwise:
+ *  * -EINVAL if the driver pointer is NULL
+ *  * -EINVAL if the not idle states available
+ *  * -ENODEV if the cpuidle framework is disabled
+ *  * -EBUSY if the driver is already assigned to the global variables
+ */
 static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 {
 	int ret;
@@ -137,8 +224,13 @@ static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 }
 
 /**
- * cpuidle_unregister_driver - unregisters a driver
- * @drv: the driver
+ * __cpuidle_unregister_driver - unregister the driver
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * Checks the driver is no longer in use, resets 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 +248,13 @@ static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 
 /**
  * cpuidle_register_driver - registers a driver
- * @drv: the driver
+ * @drv: a pointer to a valid struct cpuidle_driver
+ *
+ * Registers the driver by taking a lock to prevent multiple callers
+ * to [un]register a driver at the same time.
+ *
+ * Returns 0 on success, a negative error otherwise (refer to the
+ *  __cpuidle_register_driver).
  */
 int cpuidle_register_driver(struct cpuidle_driver *drv)
 {
@@ -172,7 +270,11 @@ EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 
 /**
  * cpuidle_unregister_driver - unregisters a driver
- * @drv: the driver
+ * @drv: a pointer to a valid struct cpuidle_driver
+ *
+ * Unregisters a driver by taking a lock to prevent multiple callers
+ * to [un]register a driver at the same time. The specified driver
+ * must match the driver currently registered.
  */
 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 {
@@ -183,7 +285,9 @@ void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 EXPORT_SYMBOL_GPL(cpuidle_unregister_driver);
 
 /**
- * cpuidle_get_driver - return the current driver
+ * cpuidle_get_driver - returns the driver tied with 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 +303,11 @@ struct cpuidle_driver *cpuidle_get_driver(void)
 EXPORT_SYMBOL_GPL(cpuidle_get_driver);
 
 /**
- * cpuidle_get_cpu_driver - return the driver tied with a cpu
+ * cpuidle_get_cpu_driver - returns the driver registered with 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 specified cpu
  */
 struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
 {
@@ -210,6 +318,14 @@ struct cpuidle_driver *cpuidle_get_cpu_driver(struct cpuidle_device *dev)
 }
 EXPORT_SYMBOL_GPL(cpuidle_get_cpu_driver);
 
+/**
+ * cpuidle_driver_ref - gets a refcount for the driver
+ *
+ * This function takes a refcount for the driver assigned to the current cpu
+ *
+ * Returns a struct cpuidle_driver pointer, or NULL if no driver is registered
+ * for the current cpu
+ */
 struct cpuidle_driver *cpuidle_driver_ref(void)
 {
 	struct cpuidle_driver *drv;
@@ -223,6 +339,12 @@ struct cpuidle_driver *cpuidle_driver_ref(void)
 	return drv;
 }
 
+/**
+ * cpuidle_driver_unref - puts down the refcount for the driver
+ *
+ * This function decrements the refcount for the driver assigned to the current
+ * cpu.
+ */
 void cpuidle_driver_unref(void)
 {
 	struct cpuidle_driver *drv = cpuidle_get_driver();
-- 
1.7.9.5