[PATCH V3 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>
---
 drivers/cpuidle/driver.c |  128 +++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 120 insertions(+), 8 deletions(-)

diff --git a/drivers/cpuidle/driver.c b/drivers/cpuidle/driver.c
index 745adae..0268346 100644
--- a/drivers/cpuidle/driver.c
+++ b/drivers/cpuidle/driver.c
@@ -22,11 +22,28 @@ DEFINE_SPINLOCK(cpuidle_driver_lock);
 
 static DEFINE_PER_CPU(struct cpuidle_driver *, cpuidle_drivers);
 
+/**
+ * __cpuidle_get_cpu_driver: returns the cpuidle driver tied with the specified
+ * cpu.
+ *
+ * @cpu: an integer specifying the cpu number
+ *
+ * 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_set_driver: assign to the per cpu variable the driver pointer for
+ * each cpu the driver is assigned to with the cpumask.
+ *
+ * @drv: a pointer to a struct cpuidle_driver
+ *
+ * Returns 0 on success, < 0 otherwise
+ */
 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 {
 	int cpu;
@@ -42,6 +59,12 @@ static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 	return 0;
 }
 
+/**
+ * __cpuidle_unset_driver: for each cpu the driver is handling, set the per cpu
+ * variable driver to NULL.
+ *
+ * @drv: a pointer to a struct cpuidle_driver
+ */
 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 {
 	int cpu;
@@ -59,11 +82,27 @@ static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 
 static struct cpuidle_driver *cpuidle_curr_driver;
 
+/**
+ * __cpuidle_get_cpu_driver: returns the global cpuidle driver pointer.
+ *
+ * @cpu: an integer specifying the cpu number, this parameter is ignored
+ *
+ * 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 cpuidle driver pointer to the global cpuidle
+ * driver variable.
+ *
+ * @drv: a pointer to a struct cpuidle_driver
+ *
+ * Returns 0 on success, < 0 otherwise
+ */
 static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 {
 	if (cpuidle_curr_driver)
@@ -74,6 +113,12 @@ static inline int __cpuidle_set_driver(struct cpuidle_driver *drv)
 	return 0;
 }
 
+/**
+ * __cpuidle_unset_driver: reset the global cpuidle driver variable if the
+ * cpuidle driver pointer match it.
+ *
+ * @drv: a pointer to a struct cpuidle_driver
+ */
 static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 {
 	if (drv == cpuidle_curr_driver)
@@ -82,21 +127,49 @@ static inline void __cpuidle_unset_driver(struct cpuidle_driver *drv)
 
 #endif
 
+/**
+ * cpuidle_setup_broadcast_timer: set the broadcast timer notification for the
+ * current cpu. This function is called per cpu context invoked by a smp cross
+ * call. It is not supposed to be called directly.
+ *
+ * @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
+ */
 static void cpuidle_setup_broadcast_timer(void *arg)
 {
 	int cpu = smp_processor_id();
 	clockevents_notify((long)(arg), &cpu);
 }
 
+/**
+ * __cpuidle_driver_init: initialize the driver internal data.
+ *
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * Returns 0 on success, < 0 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))
@@ -109,6 +182,16 @@ static int __cpuidle_driver_init(struct cpuidle_driver *drv)
 	return 0;
 }
 
+/**
+ * __cpuidle_register_driver: do some sanity checks, initializes the driver,
+ * assign 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.
+ *
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
+ * Returns 0 on success, < 0 otherwise
+ */
 static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 {
 	int ret;
@@ -135,8 +218,12 @@ static int __cpuidle_register_driver(struct cpuidle_driver *drv)
 }
 
 /**
- * cpuidle_unregister_driver - unregisters a driver
- * @drv: the driver
+ * __cpuidle_unregister_driver: checks 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.
+ *
+ * @drv: a valid pointer to a struct cpuidle_driver
+ *
  */
 static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 {
@@ -153,8 +240,12 @@ static void __cpuidle_unregister_driver(struct cpuidle_driver *drv)
 }
 
 /**
- * cpuidle_register_driver - registers a driver
- * @drv: the driver
+ * cpuidle_register_driver: registers a driver by taking a lock to prevent
+ * multiple callers to [un]register a driver at the same time.
+ *
+ * @drv: a pointer to a valid struct cpuidle_driver
+ *
+ * Returns 0 on success, < 0 otherwise
  */
 int cpuidle_register_driver(struct cpuidle_driver *drv)
 {
@@ -169,8 +260,11 @@ int cpuidle_register_driver(struct cpuidle_driver *drv)
 EXPORT_SYMBOL_GPL(cpuidle_register_driver);
 
 /**
- * cpuidle_unregister_driver - unregisters a driver
- * @drv: the driver
+ * cpuidle_unregister_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.
+ *
+ * @drv: a pointer to a valid struct cpuidle_driver
  */
 void cpuidle_unregister_driver(struct cpuidle_driver *drv)
 {
@@ -181,7 +275,9 @@ 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)
 {
@@ -197,7 +293,12 @@ 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)
 {
@@ -208,6 +309,13 @@ 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. Note 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;
@@ -221,6 +329,10 @@ struct cpuidle_driver *cpuidle_driver_ref(void)
 	return drv;
 }
 
+/**
+ * cpuidle_driver_unref: puts down the refcount for the driver. Note this
+ * function decrement 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