zephyr/include/kernel.h

/*
 * Copyright (c) 2016, Wind River Systems, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

/**
 * @file
 *
 * @brief Public kernel APIs.
 */

#ifndef _kernel__h_
#define _kernel__h_

#include <stddef.h>
#include <stdint.h>
#include <toolchain.h>
#include <sections.h>
#include <atomic.h>
#include <errno.h>
#include <misc/__assert.h>
#include <misc/dlist.h>
#include <misc/slist.h>

#ifdef __cplusplus
extern "C" {
#endif

#ifdef CONFIG_KERNEL_V2_DEBUG
#define K_DEBUG(fmt, ...) printk("[%s]  " fmt, __func__, ##__VA_ARGS__)
#else
#define K_DEBUG(fmt, ...)
#endif

#define K_PRIO_COOP(x) (-(CONFIG_NUM_COOP_PRIORITIES - (x)))
#define K_PRIO_PREEMPT(x) (x)

#define K_FOREVER (-1)
#define K_NO_WAIT 0

#define K_ANY NULL
#define K_END NULL

#if CONFIG_NUM_COOP_PRIORITIES > 0
#define K_HIGHEST_THREAD_PRIO (-CONFIG_NUM_COOP_PRIORITIES)
#else
#define K_HIGHEST_THREAD_PRIO 0
#endif

#if CONFIG_NUM_PREEMPT_PRIORITIES > 0
#define K_LOWEST_THREAD_PRIO CONFIG_NUM_PREEMPT_PRIORITIES
#else
#define K_LOWEST_THREAD_PRIO -1
#endif

#define K_HIGHEST_APPLICATION_THREAD_PRIO (K_HIGHEST_THREAD_PRIO)
#define K_LOWEST_APPLICATION_THREAD_PRIO (K_LOWEST_THREAD_PRIO - 1)

typedef sys_dlist_t _wait_q_t;

#ifdef CONFIG_DEBUG_TRACING_KERNEL_OBJECTS
#define _DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(type) struct type *__next
#define _DEBUG_TRACING_KERNEL_OBJECTS_INIT .__next = NULL,
#else
#define _DEBUG_TRACING_KERNEL_OBJECTS_INIT
#define _DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(type)
#endif

#define k_thread tcs
struct tcs;
struct k_mutex;
struct k_sem;
struct k_alert;
struct k_msgq;
struct k_mbox;
struct k_pipe;
struct k_fifo;
struct k_lifo;
struct k_stack;
struct k_mem_slab;
struct k_mem_pool;
struct k_timer;

typedef struct k_thread *k_tid_t;

/* threads/scheduler/execution contexts */

enum execution_context_types {
	K_ISR = 0,
	K_COOP_THREAD,
	K_PREEMPT_THREAD,
};

typedef void (*k_thread_entry_t)(void *p1, void *p2, void *p3);

/**
 * @brief Initialize and start a thread with an optional delay
 *
 * This routine initializes a thread and optionally delays its execution.
 * It is not ISR-callable.
 *
 * If a thread of priority higher than the current thread is spawned, and the
 * current thread id preemptible, the current thread is preempted by the new
 * thread.
 *
 * @param stack Pointer to the stack space.
 * @param stack_size Stack size in bytes.
 * @param entry Thread entry function.
 * @param p1 1st entry point parameter.
 * @param p2 2nd entry point parameter.
 * @param p3 3rd entry point parameter.
 * @param prio The thread's priority.
 * @param options Not used currently.
 * @param delay Duration of execution delay in milliseconds
 *
 * @return Kernel thread identifier
 */
extern k_tid_t k_thread_spawn(char *stack, unsigned stack_size,
			      void (*entry)(void *, void *, void*),
			      void *p1, void *p2, void *p3,
			      int32_t prio, uint32_t options, int32_t delay);

/**
 * @brief Put the current thread to sleep
 *
 * This routine puts the currently thread to sleep for the specified
 * number of milliseconds.
 *
 * @param duration Number of milliseconds the thread is to sleep
 *
 * @return N/A
 */
extern void k_sleep(int32_t duration);

/**
 * @brief Cause the current thread to busy wait
 *
 * This routine causes the current thread to execute a "do nothing" loop for
 * a specified period of microseconds.
 *
 * @warning This routine utilizes the system clock, so it must not be invoked
 * until the system clock is fully operational or while interrupts are
 * locked.
 *
 * @return N/A
 */
extern void k_busy_wait(uint32_t usec_to_wait);

/**
 * @brief Yield the current thread
 *
 * Calling this routine results in the current thread yielding to another
 * thread of the same or higher priority. If there are no other ready threads
 * of the same or higher priority, the routine will return immediately.
 *
 * @return N/A
 */
extern void k_yield(void);

/**
 * @brief Wake the specified thread from sleep
 *
 * This routine wakes the thread specified by @a thread from its sleep.
 *
 * @param thread Identifies thread to wake
 *
 * @return N/A
 */
extern void k_wakeup(k_tid_t thread);

/**
 * @brief Obtain the thread ID of the currently executing thread
 *
 * @return Current thread ID
 */
extern k_tid_t k_current_get(void);

/**
 * @brief Cancel a delayed thread start
 *
 * @param thread Delayed thread ID
 *
 * @retval 0 on success
 * @retval -EINVAL Thread has already started or not delayed
 */
extern int k_thread_cancel(k_tid_t thread);

/**
 * @brief Abort a thread
 *
 * Execution of @a thread is immediately permanently cancelled. @a thread is
 * taken off the ready queue if ready, or out of any wait queues and/or
 * timeout queues it might be currently queued on. However, objects it might
 * currently owned, such as mutexes, are not released. It is up to the
 * subsystems managing the objects to handle this.
 *
 * @param thread Thread to abort
 *
 * @return N/A
 */
extern void k_thread_abort(k_tid_t thread);

#define K_THREAD_GROUP_EXE 0x1
#define K_THREAD_GROUP_SYS 0x2
#define K_THREAD_GROUP_FPU 0x4

/* XXX - doesn't work because CONFIG_ARCH is a string */
#if 0
/* arch-specific groups */
#if CONFIG_ARCH == "x86"
#define K_THREAD_GROUP_SSE 0x4
#endif
#endif

#ifdef CONFIG_SYS_CLOCK_EXISTS
#define _THREAD_TIMEOUT_INIT(obj) \
	(obj).nano_timeout = { \
	.node = { {0}, {0} }, \
	.thread = NULL, \
	.wait_q = NULL, \
	.delta_ticks_from_prev = -1, \
	},
#else
#define _THREAD_TIMEOUT_INIT(obj)
#endif

#ifdef CONFIG_ERRNO
#define _THREAD_ERRNO_INIT(obj) (obj).errno_var = 0,
#else
#define _THREAD_ERRNO_INIT(obj)
#endif

struct _static_thread_data {
	union {
		char *init_stack;
		struct k_thread *thread;
	};
	unsigned int init_stack_size;
	void (*init_entry)(void *, void *, void *);
	void *init_p1;
	void *init_p2;
	void *init_p3;
	int init_prio;
	uint32_t init_options;
	int32_t init_delay;
	void (*init_abort)(void);
	uint32_t init_groups;
};

#define _THREAD_INITIALIZER(stack, stack_size,                   \
			    entry, p1, p2, p3,                   \
			    prio, options, delay, abort, groups) \
	{                                                        \
	.init_stack = (stack),                                   \
	.init_stack_size = (stack_size),                         \
	.init_entry = (void (*)(void *, void *, void *))entry,   \
	.init_p1 = (void *)p1,                                   \
	.init_p2 = (void *)p2,                                   \
	.init_p3 = (void *)p3,                                   \
	.init_prio = (prio),                                     \
	.init_options = (options),                               \
	.init_delay = (delay),                                   \
	.init_abort = (abort),                                   \
	.init_groups = (groups),                                 \
	}

/**
 * @brief Define a static thread.
 *
 * @internal It has been observed that the x86 compiler by default aligns
 * these _static_thread_data structures to 32-byte boundaries, thereby
 * wasting space. To work around this, force a 4-byte alignment.
 */
#define K_THREAD_DEFINE(name, stack_size,                                \
			entry, p1, p2, p3,                               \
			prio, options, delay)                            \
	char __noinit __stack _k_thread_obj_##name[stack_size];          \
	struct _static_thread_data _k_thread_data_##name __aligned(4)    \
		__in_section(_static_thread_data, static, name) =        \
		_THREAD_INITIALIZER(_k_thread_obj_##name, stack_size,    \
				entry, p1, p2, p3, prio, options, delay, \
				NULL, 0); \
	const k_tid_t name = (k_tid_t)_k_thread_obj_##name

/**
 * @brief Get a thread's priority
 *
 * @param thread ID of thread to query
 *
 * @return Specified thread's priority
 */
extern int  k_thread_priority_get(k_tid_t thread);

/**
 * @brief Set the priority of a thread
 *
 * This routine immediately changes the priority of the specified thread.
 *
 * Rescheduling can occur immediately depending on the priority @a thread is
 * set to:
 *
 * - If its priority is raised above the priority of the caller of this
 * function, and the caller is preemptible, @a thread will be scheduled in.
 *
 * - If the caller operates on itself, it lowers its priority below that of
 * other threads in the system, and the caller is preemptible, the thread of
 * highest priority will be scheduled in.
 *
 * Priority can be assigned in the range of -CONFIG_NUM_COOP_PRIORITIES to
 * CONFIG_NUM_PREEMPT_PRIORITIES-1, where -CONFIG_NUM_COOP_PRIORITIES is the
 * highest priority.
 *
 * @param thread Thread whose priority is to be set.
 * @param prio New priority.
 *
 * @warning Changing the priority of a thread currently involved in mutex
 * priority inheritance may result in undefined behavior.
 *
 * @return N/A
 */
extern void k_thread_priority_set(k_tid_t thread, int prio);

/**
 * @brief Suspend a thread
 *
 * Remove @a thread from scheduling decisions. All other internal operations
 * on @a thread will still be performed: any timeout it is on keeps ticking
 * and delivered upon expiry, objects it is waiting on are still handed to it,
 * etc.
 *
 * @param thread Thread to suspend
 *
 * @return N/A
 */
extern void k_thread_suspend(k_tid_t thread);

/**
 * @brief Resume a previously suspended thread
 *
 * Resume using @a thread in scheduling decisions.
 *
 * @param thread Thread to resume
 *
 * @return N/A
 */
extern void k_thread_resume(k_tid_t thread);

/**
 * @brief Set time-slicing period and scope
 *
 * This routine controls how thread time slicing is performed by the scheduler
 * on preemptible threads; it specifes the maximum time slice length (in
 * milliseconds) and the highest thread priority level for which time slicing
 * is performed.
 *
 * To enable time slicing, a non-zero time slice length must be specified.
 * The scheduler then ensures that no executing thread runs for more than the
 * specified number of milliseconds before giving other threads of that priority
 * a chance to execute. (However, any thread whose priority is higher than the
 * specified thread priority level is exempted, and may execute as long as
 * desired without being pre-empted due to time slicing.)
 *
 * Time slicing limits only the maximum amount of time a thread may continuously
 * execute. Once the scheduler selects a thread for execution, there is no
 * minimum guaranteed time the thread will execute before threads of greater or
 * equal priority are scheduled.
 *
 * When the currently-executing thread is the only one of that priority eligible
 * for execution, this routine has no effect; the thread is immediately
 * rescheduled after the slice period expires.
 *
 * To disable timeslicing, call the API with both parameters set to zero.
 *
 * @return N/A
 */
extern void k_sched_time_slice_set(int32_t slice, int prio);

/**
 * @brief Determine if code is running at interrupt level
 *
 * @return 0 if invoked by a thread, or non-zero if invoked by an ISR
 */
extern int k_am_in_isr(void);

/**
 * @brief Set thread's custom data
 *
 * This routine sets the custom data value for the current thread. Custom
 * data is not used by the kernel itself, and is freely available for the
 * thread to use as it sees fit.
 *
 * This provides a skeleton upon which to build thread-local storage.
 *
 * @param value New value to set the thread's custom data to.
 *
 * @return N/A
 */
extern void k_thread_custom_data_set(void *value);

/**
 * @brief Get thread's custom data
 *
 * This function returns the custom data value for the current thread.
 *
 * @return current custom data value
 */
extern void *k_thread_custom_data_get(void);

/**
 *  kernel timing
 */

#include <sys_clock.h>

/* private internal time manipulation (users should never play with ticks) */

/* added tick needed to account for tick in progress */
#define _TICK_ALIGN 1

static int64_t __ticks_to_ms(int64_t ticks)
{
#if CONFIG_SYS_CLOCK_EXISTS
	return (MSEC_PER_SEC * (uint64_t)ticks) / sys_clock_ticks_per_sec;
#else
	__ASSERT(ticks == 0, "");
	return 0;
#endif
}


/* timeouts */

struct _timeout;
typedef void (*_timeout_func_t)(struct _timeout *t);

struct _timeout {
	sys_dlist_t node;
	struct k_thread *thread;
	sys_dlist_t *wait_q;
	int32_t delta_ticks_from_prev;
	_timeout_func_t func;
};


/* timers */

struct k_timer {
	/*
	 * _timeout structure must be first here if we want to use
	 * dynamic timer allocation. timeout.node is used in the double-linked
	 * list of free timers
	 */
	struct _timeout timeout;

	/* wait queue for the (single) thread waiting on this timer */
	_wait_q_t wait_q;

	/* runs in ISR context */
	void (*expiry_fn)(struct k_timer *);

	/* runs in the context of the thread that calls k_timer_stop() */
	void (*stop_fn)(struct k_timer *);

	/* timer period */
	int32_t period;

	/* timer status */
	uint32_t status;

	/* used to support legacy timer APIs */
	void *_legacy_data;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_timer);
};

#define K_TIMER_INITIALIZER(obj, expiry, stop) \
	{ \
	.timeout.delta_ticks_from_prev = -1, \
	.timeout.wait_q = NULL, \
	.timeout.thread = NULL, \
	.timeout.func = _timer_expiration_handler, \
	.wait_q = SYS_DLIST_STATIC_INIT(&obj.wait_q), \
	.expiry_fn = expiry, \
	.stop_fn = stop, \
	.status = 0, \
	._legacy_data = NULL, \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @brief Statically define a timer and initialize it
 *
 * If the timer is to be accessed outside the module where it is defined, it
 * can be declared via
 *
 *    extern struct k_timer @a name;
 *
 * @param name Name of the timer variable.
 * @param expiry_fn Function to invoke each time timer expires.
 * @param stop_fn   Function to invoke if timer is stopped while running.
 */
#define K_TIMER_DEFINE(name, expiry_fn, stop_fn) \
	struct k_timer name \
		__in_section(_k_timer, static, name) = \
		K_TIMER_INITIALIZER(name, expiry_fn, stop_fn)

/**
 * @brief Initialize a timer.
 *
 * This routine must be called before the timer is used.
 *
 * @param timer     Address of timer.
 * @param expiry_fn Function to invoke each time timer expires.
 * @param stop_fn   Function to invoke if timer is stopped while running.
 *
 * @return N/A
 */
extern void k_timer_init(struct k_timer *timer,
			 void (*expiry_fn)(struct k_timer *),
			 void (*stop_fn)(struct k_timer *));

/**
 * @brief Start a timer.
 *
 * This routine starts a timer, and resets its status to zero. The timer
 * begins counting down using the specified duration and period values.
 *
 * Attempting to start a timer that is already running is permitted.
 * The timer's status is reset to zero and the timer begins counting down
 * using the new duration and period values.
 *
 * @param timer     Address of timer.
 * @param duration  Initial timer duration (in milliseconds).
 * @param period    Timer period (in milliseconds).
 *
 * @return N/A
 */
extern void k_timer_start(struct k_timer *timer,
			  int32_t duration, int32_t period);

/**
 * @brief Stop a timer.
 *
 * This routine stops a running timer prematurely. The timer's stop function,
 * if one exists, is invoked by the caller.
 *
 * Attempting to stop a timer that is not running is permitted, but has no
 * effect on the timer since it is already stopped.
 *
 * @param timer     Address of timer.
 *
 * @return N/A
 */
extern void k_timer_stop(struct k_timer *timer);

/**
 * @brief Read timer status.
 *
 * This routine reads the timer's status, which indicates the number of times
 * it has expired since its status was last read.
 *
 * Calling this routine resets the timer's status to zero.
 *
 * @param timer     Address of timer.
 *
 * @return Timer status.
 */
extern uint32_t k_timer_status_get(struct k_timer *timer);

/**
 * @brief Synchronize thread to timer expiration.
 *
 * This routine blocks the calling thread until the timer's status is non-zero
 * (indicating that it has expired at least once since it was last examined)
 * or the timer is stopped. If the timer status is already non-zero,
 * or the timer is already stopped, the caller continues without waiting.
 *
 * Calling this routine resets the timer's status to zero.
 *
 * This routine must not be used by interrupt handlers, since they are not
 * allowed to block.
 *
 * @param timer     Address of timer.
 *
 * @return Timer status.
 */
extern uint32_t k_timer_status_sync(struct k_timer *timer);

/**
 * @brief Get timer remaining before next timer expiration.
 *
 * This routine computes the (approximate) time remaining before a running
 * timer next expires. If the timer is not running, it returns zero.
 *
 * @param timer     Address of timer.
 *
 * @return Remaining time (in milliseconds).
 */
extern int32_t k_timer_remaining_get(struct k_timer *timer);


/* kernel clocks */

/**
 * @brief Get the time elapsed since the system booted (uptime)
 *
 * @return The current uptime of the system in ms
 */
extern int64_t k_uptime_get(void);

/**
 * @brief Get the lower 32-bit of time elapsed since the system booted (uptime)
 *
 * This function is potentially less onerous in both the time it takes to
 * execute, the interrupt latency it introduces and the amount of 64-bit math
 * it requires than k_uptime_get(), but it only provides an uptime value of
 * 32-bits. The user must handle possible rollovers/spillovers.
 *
 * At a rate of increment of 1000 per second, it rolls over approximately every
 * 50 days.
 *
 * @return The current uptime of the system in ms
 */
extern uint32_t k_uptime_get_32(void);

/**
 * @brief Get the difference between a reference time and the current uptime
 *
 * @param reftime A pointer to a reference time. It is updated with the current
 * uptime upon return.
 *
 * @return The delta between the reference time and the current uptime.
 */
extern int64_t k_uptime_delta(int64_t *reftime);

/**
 * @brief Get the difference between a reference time and the current uptime
 *
 * The 32-bit version of k_uptime_delta(). It has the same perks and issues as
 * k_uptime_get_32().
 *
 * @param reftime A pointer to a reference time. It is updated with the current
 * uptime upon return.
 *
 * @return The delta between the reference time and the current uptime.
 */
extern uint32_t k_uptime_delta_32(int64_t *reftime);

/**
 * @brief Read the platform's timer hardware
 *
 * This routine returns the current time in terms of timer hardware clock
 * cycles.
 *
 * @return up counter of elapsed clock cycles
 */
extern uint32_t k_cycle_get_32(void);

/**
 *  data transfers (basic)
 */

/* fifos */

struct k_fifo {
	_wait_q_t wait_q;
	sys_slist_t data_q;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_fifo);
};

/**
 * @brief Initialize a kernel FIFO object.
 *
 * This routine initializes a kernel FIFO object structure. It must not be
 * called from an ISR.
 *
 * @param fifo FIFO to initialize.
 *
 * @return N/A
 */
extern void k_fifo_init(struct k_fifo *fifo);

/**
 * @brief Add an element to the end of a FIFO.
 *
 * This routine adds an element to the end of a FIFO. FIFO data items must be
 * aligned on a 4-byte boundary, as the kernel reserves the first 32 bits of
 * each item for use as a pointer to the next data item in the FIFO's link
 * list. Each data item added to the FIFO must include and reserve these first
 * 32 bits.
 *
 * @param fifo FIFO on which to interact.
 * @param data Data to send.
 *
 * @return N/A
 */
extern void k_fifo_put(struct k_fifo *fifo, void *data);

/**
 * @brief Atomically add a list of elements to the end of a FIFO.
 *
 * This routine adds a list of elements in one shot to the end of a FIFO
 * object. If threads are pending on the FIFO object, they become ready to run.
 * If this API is called from a preemptible thread, the highest priority one
 * will preempt the running thread once the put operation is complete.
 *
 * If enough threads are waiting on the FIFO, the address of each element given
 * to threads is returned to the waiting thread. The remaining elements are
 * linked to the end of the list.
 *
 * The list must be a singly-linked list, where each element only has a pointer
 * to the next one. The list must be NULL-terminated.
 *
 * @param fifo FIFO on which to interact.
 * @param head head of singly-linked list
 * @param tail tail of singly-linked list
 *
 * @return N/A
 */
extern void k_fifo_put_list(struct k_fifo *fifo, void *head, void *tail);

/**
 * @brief Atomically add a list of elements to the end of a FIFO.
 *
 * See k_fifo_put_list for the description of the behaviour.
 *
 * It takes a pointer to a sys_slist_t object instead of the head and tail of
 * a custom singly-linked list. The sys_slist_t object is invalid afterwards
 * and must be re-initialized via sys_slist_init().
 *
 * @param fifo FIFO on which to interact.
 * @param list pointer to singly-linked list
 *
 * @return N/A
 */
extern void k_fifo_put_slist(struct k_fifo *fifo, sys_slist_t *list);

/**
 * @brief Get an element from the head of a FIFO.
 *
 * If no element is available, the function returns NULL. The first word in
 * the element contains invalid data because its memory location was used to
 * store a pointer to the next element in the linked list.
 *
 * @param fifo FIFO on which to interact.
 * @param timeout Number of milliseconds to wait for item if FIFO is empty,
 *                or one of the special values K_NO_WAIT and K_FOREVER.
 *
 * @warning If it is to be called from the context of an ISR, then @a
 * timeout must be set to K_NO_WAIT.
 *
 * @return Pointer to head element in the list when available.
 *         NULL Otherwise.
 *
 * @sa K_NO_WAIT, K_FOREVER
 */
extern void *k_fifo_get(struct k_fifo *fifo, int32_t timeout);

#define K_FIFO_INITIALIZER(obj) \
	{ \
	.wait_q = SYS_DLIST_STATIC_INIT(&obj.wait_q), \
	.data_q = SYS_SLIST_STATIC_INIT(&obj.data_q), \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @brief Statically define a FIFO and initialize it
 *
 * If the FIFO is to be accessed outside the module where it is defined, it
 * can be declared via
 *
 *    extern struct k_fifo @a name;
 *
 * @param name Name of the FIFO variable.
 */
#define K_FIFO_DEFINE(name) \
	struct k_fifo name \
		__in_section(_k_fifo, static, name) = \
		K_FIFO_INITIALIZER(name)

/* lifos */

struct k_lifo {
	_wait_q_t wait_q;
	void *list;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_lifo);
};

/**
 * @brief Initialize a kernel linked list LIFO object.
 *
 * This routine initializes a kernel LIFO object structure. It must not be
 * called from an ISR.
 *
 * @param lifo LIFO to initialize.
 *
 * @return N/A
 */
extern void k_lifo_init(struct k_lifo *lifo);

/**
 * @brief Prepend an element to a LIFO
 *
 * This routine prepends an element to a LIFO. LIFO data items must be
 * aligned on a 4-byte boundary, as the kernel reserves the first 32 bits of
 * each item for use as a pointer to the next data item in the LIFO's link
 * list. Each data item added to the LIFO must include and reserve these first
 * 32 bits.
 *
 * @param lifo LIFO on which to interact.
 * @param data Data to send.
 *
 * @return N/A
 */
extern void k_lifo_put(struct k_lifo *lifo, void *data);

/**
 * @brief Get the first element from a LIFO.
 *
 * If no element is available, the function returns NULL. The first word in
 * the element contains invalid data because its memory location was used to
 * store a pointer to the next element in the linked list.
 *
 * @param lifo LIFO on which to interact.
 * @param timeout Number of milliseconds to wait for item if LIFO is empty,
 *                or one of the special values K_NO_WAIT and K_FOREVER.
 *
 * @warning If it is to be called from the context of an ISR, then @a
 * timeout must be set to K_NO_WAIT.
 *
 * @return Pointer to head element in the list when available.
 *         NULL Otherwise.
 *
 * @sa K_NO_WAIT, K_FOREVER
 */
extern void *k_lifo_get(struct k_lifo *lifo, int32_t timeout);

#define K_LIFO_INITIALIZER(obj) \
	{ \
	.wait_q = SYS_DLIST_STATIC_INIT(&obj.wait_q), \
	.list = NULL, \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @brief Statically define a LIFO and initialize it
 *
 * If the LIFO is to be accessed outside the module where it is defined, it
 * can be declared via
 *
 *    extern struct k_lifo @a name;
 *
 * @param name Name of the LIFO variable.
 */
#define K_LIFO_DEFINE(name) \
	struct k_lifo name \
		__in_section(_k_lifo, static, name) = \
		K_LIFO_INITIALIZER(name)

/* stacks */

struct k_stack {
	_wait_q_t wait_q;
	uint32_t *base, *next, *top;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_stack);
};

extern void k_stack_init(struct k_stack *stack,
			 uint32_t *buffer, int num_entries);
extern void k_stack_push(struct k_stack *stack, uint32_t data);
extern int k_stack_pop(struct k_stack *stack, uint32_t *data, int32_t timeout);

#define K_STACK_INITIALIZER(obj, stack_buffer, stack_num_entries) \
	{ \
	.wait_q = SYS_DLIST_STATIC_INIT(&obj.wait_q), \
	.base = stack_buffer, \
	.next = stack_buffer, \
	.top = stack_buffer + stack_num_entries, \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @brief Statically define a stack object and initialize it
 *
 * If the stack is to be accessed outside the module where it is defined, it
 * can be declared via
 *
 *    extern struct k_stack @a name;
 *
 * @param name Name of the stack object variable.
 * @param stack_num_entries Number of entries in the stack object
 */
#define K_STACK_DEFINE(name, stack_num_entries)                \
	uint32_t __noinit                                      \
		_k_stack_buf_##name[stack_num_entries];        \
	struct k_stack name                                    \
		__in_section(_k_stack, static, name) =    \
		K_STACK_INITIALIZER(name, _k_stack_buf_##name, \
				    stack_num_entries)

/**
 *  workqueues
 */

struct k_work;

typedef void (*k_work_handler_t)(struct k_work *);

/**
 * A workqueue is a thread that executes @ref k_work items that are
 * queued to it.  This is useful for drivers which need to schedule
 * execution of code which might sleep from ISR context.  The actual
 * thread identifier is not stored in the structure in order to save
 * space.
 */
struct k_work_q {
	struct k_fifo fifo;
};

/**
 * @brief Work flags.
 */
enum {
	K_WORK_STATE_PENDING,	/* Work item pending state */
};

/**
 * @brief An item which can be scheduled on a @ref k_work_q.
 */
struct k_work {
	void *_reserved;		/* Used by k_fifo implementation. */
	k_work_handler_t handler;
	atomic_t flags[1];
};

/**
 * @brief Statically initialize work item
 */
#define K_WORK_INITIALIZER(work_handler) \
	{ \
	._reserved = NULL, \
	.handler = work_handler, \
	.flags = { 0 } \
	}

/**
 * @brief Dynamically initialize work item
 */
static inline void k_work_init(struct k_work *work, k_work_handler_t handler)
{
	atomic_clear_bit(work->flags, K_WORK_STATE_PENDING);
	work->handler = handler;
}

/**
 * @brief Submit a work item to a workqueue.
 *
 * This procedure schedules a work item to be processed.
 * In the case where the work item has already been submitted and is pending
 * execution, calling this function will result in a no-op. In this case, the
 * work item must not be modified externally (e.g. by the caller of this
 * function), since that could cause the work item to be processed in a
 * corrupted state.
 *
 * @param work_q to schedule the work item
 * @param work work item
 *
 * @return N/A
 */
static inline void k_work_submit_to_queue(struct k_work_q *work_q,
					  struct k_work *work)
{
	if (!atomic_test_and_set_bit(work->flags, K_WORK_STATE_PENDING)) {
		k_fifo_put(&work_q->fifo, work);
	}
}

/**
 * @brief Check if work item is pending.
 *
 * @param work Work item to query
 *
 * @return K_WORK_STATE_PENDING if pending, 0 if not
 */
static inline int k_work_pending(struct k_work *work)
{
	return atomic_test_bit(work->flags, K_WORK_STATE_PENDING);
}

/**
 * @brief Start a new workqueue.
 *
 * This routine must not be called from an ISR.
 *
 * @param work_q Pointer to Work queue
 * @param stack Pointer to work queue thread's stack
 * @param stack_size Size of the work queue thread's stack
 * @param prio Priority of the work queue's thread
 *
 * @return N/A
 */
extern void k_work_q_start(struct k_work_q *work_q, char *stack,
			   unsigned stack_size, unsigned prio);

#if defined(CONFIG_SYS_CLOCK_EXISTS)

/**
 * @brief An item which can be scheduled on a @ref k_work_q with a delay
 */
struct k_delayed_work {
	struct k_work work;
	struct _timeout timeout;
	struct k_work_q *work_q;
};

/**
 * @brief Initialize delayed work
 *
 * Initialize a delayed work item.
 *
 * @param work Delayed work item
 * @param handler Routine invoked when processing delayed work item
 *
 * @return N/A
 */
extern void k_delayed_work_init(struct k_delayed_work *work,
				k_work_handler_t handler);

/**
 * @brief Submit a delayed work item to a workqueue.
 *
 * This routine schedules a work item to be processed after a delay.
 * Once the delay has passed, the work item is submitted to the work queue:
 * at this point, it is no longer possible to cancel it. Once the work item's
 * handler is about to be executed, the work is considered complete and can be
 * resubmitted.
 *
 * Care must be taken if the handler blocks or yield as there is no implicit
 * mutual exclusion mechanism. Such usage is not recommended and if necessary,
 * it should be explicitly done between the submitter and the handler.
 *
 * @param work_q Workqueue to schedule the work item
 * @param work Delayed work item
 * @param delay Delay before scheduling the work item (in milliseconds)
 *
 * @return 0 in case of success or negative value in case of error.
 */
extern int k_delayed_work_submit_to_queue(struct k_work_q *work_q,
					  struct k_delayed_work *work,
					  int32_t delay);

/**
 * @brief Cancel a delayed work item
 *
 * This routine cancels a scheduled work item. If the work has been completed
 * or is idle, this will do nothing. The only case where this can fail is when
 * the work has been submitted to the work queue, but the handler has not run
 * yet.
 *
 * @param work Delayed work item to be canceled
 *
 * @return 0 in case of success or negative value in case of error.
 */
extern int k_delayed_work_cancel(struct k_delayed_work *work);

#endif /* CONFIG_SYS_CLOCK_EXISTS */

#if defined(CONFIG_SYSTEM_WORKQUEUE)

extern struct k_work_q k_sys_work_q;

/**
 * @brief Submit a work item to the system workqueue.
 *
 * @ref k_work_submit_to_queue
 *
 * When using the system workqueue it is not recommended to block or yield
 * on the handler since its thread is shared system wide it may cause
 * unexpected behavior.
 */
static inline void k_work_submit(struct k_work *work)
{
	k_work_submit_to_queue(&k_sys_work_q, work);
}

#if defined(CONFIG_SYS_CLOCK_EXISTS)
/**
 * @brief Submit a delayed work item to the system workqueue.
 *
 * @ref k_delayed_work_submit_to_queue
 *
 * When using the system workqueue it is not recommended to block or yield
 * on the handler since its thread is shared system wide it may cause
 * unexpected behavior.
 */
static inline int k_delayed_work_submit(struct k_delayed_work *work,
					   int32_t delay)
{
	return k_delayed_work_submit_to_queue(&k_sys_work_q, work, delay);
}

#endif /* CONFIG_SYS_CLOCK_EXISTS */
#endif /* CONFIG_SYSTEM_WORKQUEUE */

/**
 * synchronization
 */

/* mutexes */

struct k_mutex {
	_wait_q_t wait_q;
	struct k_thread *owner;
	uint32_t lock_count;
	int owner_orig_prio;
#ifdef CONFIG_OBJECT_MONITOR
	int num_lock_state_changes;
	int num_conflicts;
#endif

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_mutex);
};

#ifdef CONFIG_OBJECT_MONITOR
#define _MUTEX_INIT_OBJECT_MONITOR \
	.num_lock_state_changes = 0, .num_conflicts = 0,
#else
#define _MUTEX_INIT_OBJECT_MONITOR
#endif

#define K_MUTEX_INITIALIZER(obj) \
	{ \
	.wait_q = SYS_DLIST_STATIC_INIT(&obj.wait_q), \
	.owner = NULL, \
	.lock_count = 0, \
	.owner_orig_prio = K_LOWEST_THREAD_PRIO, \
	_MUTEX_INIT_OBJECT_MONITOR \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @brief Statically define a mutex object and initialize it
 *
 * If the mutex is to be accessed outside the module where it is defined, it
 * can be declared via
 *
 *    extern struct k_mutex @a name;
 *
 * @param name Name of the mutex object variable.
 */
#define K_MUTEX_DEFINE(name) \
	struct k_mutex name \
		__in_section(_k_mutex, static, name) = \
		K_MUTEX_INITIALIZER(name)

/**
 * @brief Initialize a mutex
 *
 * Upon initialization, the mutex is available and does not have an owner.
 *
 * @param mutex Mutex to initialize
 *
 * @return N/A
 */
extern void k_mutex_init(struct k_mutex *mutex);

/**
 * @brief Lock a mutex
 *
 * This routine locks mutex @a mutex. When the mutex is locked by another
 * thread, the thread calling this function will either wait until the mutex
 * becomes available, or until a specified timeout expires.
 *
 * A thread is permitted to lock a mutex it has already locked; in such a case,
 * this routine immediately succeeds and the lock count is increased by 1.
 *
 * @param mutex Pointer to a mutex object.
 * @param timeout Number of milliseconds to wait if mutex is unavailable,
 *                or one of the special values K_NO_WAIT and K_FOREVER.
 *
 * @retval 0 When semaphore is obtained successfully.
 * @retval -EBUSY Failed to immediately lock mutex when @a timeout is K_NO_WAIT.
 * @retval -EAGAIN When timeout expires.
 *
 * @sa K_NO_WAIT, K_FOREVER
 */
extern int k_mutex_lock(struct k_mutex *mutex, int32_t timeout);

/**
 * @brief Unlock a mutex
 *
 * This routine unlocks mutex @a mutex. The mutex must already be locked by the
 * requesting thread.
 *
 * The mutex cannot be claimed by another thread until it has been unlocked by
 * the requesting thread as many times as it was previously locked by that
 * thread.
 *
 * @param mutex Mutex name.
 *
 * @return N/A
 */

extern void k_mutex_unlock(struct k_mutex *mutex);

/* semaphores */

struct k_sem {
	_wait_q_t wait_q;
	unsigned int count;
	unsigned int limit;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_sem);
};

/**
 * @brief Initialize a semaphore object.
 *
 * An initial count and a count limit can be specified. The count will never go
 * over the count limit if the semaphore is given multiple times without being
 * taken.
 *
 * Cannot be called from ISR.
 *
 * @param sem Pointer to a semaphore object.
 * @param initial_count Initial count.
 * @param limit Highest value the count can take during operation.
 *
 * @return N/A
 */
extern void k_sem_init(struct k_sem *sem, unsigned int initial_count,
			unsigned int limit);

/**
 * @brief Take a semaphore, possibly pending if not available.
 *
 * The current execution context tries to obtain the semaphore. If the
 * semaphore is unavailable and a timeout other than K_NO_WAIT is specified,
 * the context will pend.
 *
 * @param sem Pointer to a semaphore object.
 * @param timeout Number of milliseconds to wait if semaphore is unavailable,
 *                or one of the special values K_NO_WAIT and K_FOREVER.
 *
 * @warning If it is called from the context of an ISR, then the only legal
 * value for @a timeout is K_NO_WAIT.
 *
 * @retval 0 When semaphore is obtained successfully.
 * @retval -EAGAIN When timeout expires.
 * @retval -EBUSY When unavailable and the timeout is K_NO_WAIT.
 *
 * @sa K_NO_WAIT, K_FOREVER
 */
extern int k_sem_take(struct k_sem *sem, int32_t timeout);

/**
 * @brief Give a semaphore.
 *
 * Increase the semaphore's internal count by 1, up to its limit, if no thread
 * is waiting on the semaphore; otherwise, wake up the first thread in the
 * semaphore's waiting queue.
 *
 * If the latter case, and if the current context is preemptible, the thread
 * that is taken off the wait queue will be scheduled in and will preempt the
 * current thread.
 *
 * @param sem Pointer to a semaphore object.
 *
 * @return N/A
 */
extern void k_sem_give(struct k_sem *sem);

/**
 * @brief Reset a semaphore's count to zero.
 *
 * The only effect is that the count is set to zero. There is no other
 * side-effect to calling this function.
 *
 * @param sem Pointer to a semaphore object.
 *
 * @return N/A
 */
static inline void k_sem_reset(struct k_sem *sem)
{
	sem->count = 0;
}

/**
 * @brief Get a semaphore's count.
 *
 * Note there is no guarantee the count has not changed by the time this
 * function returns.
 *
 * @param sem Pointer to a semaphore object.
 *
 * @return The current semaphore count.
 */
static inline unsigned int k_sem_count_get(struct k_sem *sem)
{
	return sem->count;
}

#ifdef CONFIG_SEMAPHORE_GROUPS
/**
 * @brief Take the first available semaphore
 *
 * Given a list of semaphore pointers, this routine will attempt to take one
 * of them, waiting up to a maximum of @a timeout ms to do so. The taken
 * semaphore is identified by @a sem (set to NULL on error).
 *
 * Be aware that the more semaphores specified in the group, the more stack
 * space is required by the waiting thread.
 *
 * @param sem_array Array of semaphore pointers terminated by a K_END entry
 * @param sem Identifies the semaphore that was taken
 * @param timeout Number of milliseconds to wait if semaphores are unavailable,
 *                or one of the special values K_NO_WAIT and K_FOREVER.
 *
 * @retval 0 A semaphore was successfully taken
 * @retval -EBUSY No semaphore was available (@a timeout = K_NO_WAIT)
 * @retval -EAGAIN Time out occurred while waiting for semaphore
 *
 * @sa K_NO_WAIT, K_FOREVER
 */

extern int k_sem_group_take(struct k_sem *sem_array[], struct k_sem **sem,
			    int32_t timeout);

/**
 * @brief Give all the semaphores in the group
 *
 * This routine will give each semaphore in the array of semaphore pointers.
 *
 * @param sem_array Array of semaphore pointers terminated by a K_END entry
 *
 * @return N/A
 */
extern void k_sem_group_give(struct k_sem *sem_array[]);

/**
 * @brief Reset the count to zero on each semaphore in the array
 *
 * This routine resets the count of each semaphore in the group to zero.
 * Note that it does NOT have any impact on any thread that might have
 * been previously pending on any of the semaphores.
 *
 * @param sem_array Array of semaphore pointers terminated by a K_END entry
 *
 * @return N/A
 */
extern void k_sem_group_reset(struct k_sem *sem_array[]);
#endif

#define K_SEM_INITIALIZER(obj, initial_count, count_limit) \
	{ \
	.wait_q = SYS_DLIST_STATIC_INIT(&obj.wait_q), \
	.count = initial_count, \
	.limit = count_limit, \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @def K_SEM_DEFINE
 *
 * @brief Statically define and initialize a global semaphore.
 *
 * Create a global semaphore named @a name. It is initialized as if k_sem_init()
 * was called on it. If the semaphore is to be accessed outside the module
 * where it is defined, it can be declared via
 *
 *    extern struct k_sem @a name;
 *
 * @param name Name of the semaphore variable.
 * @param initial_count Initial count.
 * @param count_limit Highest value the count can take during operation.
 */
#define K_SEM_DEFINE(name, initial_count, count_limit) \
	struct k_sem name \
		__in_section(_k_sem, static, name) = \
		K_SEM_INITIALIZER(name, initial_count, count_limit)

/* alerts */

#define K_ALERT_DEFAULT NULL
#define K_ALERT_IGNORE ((void *)(-1))

typedef int (*k_alert_handler_t)(struct k_alert *);

struct k_alert {
	k_alert_handler_t handler;
	atomic_t send_count;
	struct k_work work_item;
	struct k_sem sem;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_alert);
};

extern void _alert_deliver(struct k_work *work);

#define K_ALERT_INITIALIZER(obj, alert_handler, max_num_pending_alerts) \
	{ \
	.handler = (k_alert_handler_t)alert_handler, \
	.send_count = ATOMIC_INIT(0), \
	.work_item = K_WORK_INITIALIZER(_alert_deliver), \
	.sem = K_SEM_INITIALIZER(obj.sem, 0, max_num_pending_alerts), \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @brief Statically define and initialize a global alert
 *
 * Create a global alert named @a name. It is initialized as if k_alert_init()
 * was called on it. If the alert is to be accessed outside the module
 * where it is defined, it can be declared via
 *
 *    extern struct k_alert @a name;
 *
 * @param name Alert name
 * @param alert_handler Handler to invoke after the delivery of the alert
 * @param max_num_pending_alerts Maximum number of concurrent pending alerts
 */
#define K_ALERT_DEFINE(name, alert_handler, max_num_pending_alerts) \
	struct k_alert name \
		__in_section(_k_alert, static, name) = \
		K_ALERT_INITIALIZER(name, alert_handler, \
				    max_num_pending_alerts)

/**
 * @brief Initialize an alert object.
 *
 * This routine initializes a kernel alert object structure. It must not be
 * called from an ISR.
 *
 * @param alert Pointer to the alert object
 * @param handler Routine to invoke after delivery of alert
 * @param max_num_pending_alerts Maximum number of concurrent pending alerts
 *
 * @return N/A
 */
extern void k_alert_init(struct k_alert *alert, k_alert_handler_t handler,
			 unsigned int max_num_pending_alerts);

/**
 * @brief Receive an alert
 *
 * The current execution context tries to receive the alert. If the
 * semaphore is unavailable and a timeout other than K_NO_WAIT is specified,
 * the context will pend.
 *
 * @param alert Pointer to a alert object.
 * @param timeout Number of milliseconds to wait if alert is unavailable,
 *                or one of the special values K_NO_WAIT and K_FOREVER.
 *
 * @warning If it is called from the context of an ISR, then the only legal
 * value for @a timeout is K_NO_WAIT.
 *
 * @retval 0 When alert is received successfully.
 * @retval -EAGAIN When timeout expires.
 * @retval -EBUSY When unavailable and the timeout is K_NO_WAIT.
 *
 * @sa K_NO_WAIT, K_FOREVER
 */
extern int k_alert_recv(struct k_alert *alert, int32_t timeout);

/**
 * @brief Signal an alert
 *
 * This routine signals the specified alert. If an alert handler is installed
 * for that alert, it will run. If no alert handler is installed, any thread
 * waiting on the alert is released.
 *
 * @param alert Alert to signal
 *
 * @return N/A
 */
extern void k_alert_send(struct k_alert *alert);

/**
 *  data transfers (complex)
 */

/* message queues */

struct k_msgq {
	_wait_q_t wait_q;
	size_t msg_size;
	uint32_t max_msgs;
	char *buffer_start;
	char *buffer_end;
	char *read_ptr;
	char *write_ptr;
	uint32_t used_msgs;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_msgq);
};

#define K_MSGQ_INITIALIZER(obj, q_buffer, q_msg_size, q_max_msgs) \
	{ \
	.wait_q = SYS_DLIST_STATIC_INIT(&obj.wait_q), \
	.max_msgs = q_max_msgs, \
	.msg_size = q_msg_size, \
	.buffer_start = q_buffer, \
	.buffer_end = q_buffer + (q_max_msgs * q_msg_size), \
	.read_ptr = q_buffer, \
	.write_ptr = q_buffer, \
	.used_msgs = 0, \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @brief Define a message queue
 *
 * This declares and initializes a message queue whose buffer is aligned to
 * a @a q_align -byte boundary. The new message queue can be passed to the
 * kernel's message queue functions.
 *
 * Note that for each of the mesages in the message queue to be aligned to
 * @a q_align bytes, then @a q_msg_size must be a multiple of @a q_align.
 *
 * If the message queue is to be accessed outside the module where it is
 * defined, it can be declared via
 *
 *    extern struct k_msgq @a name;
 *
 * @param q_name Name of the message queue
 * @param q_msg_size The size in bytes of each message
 * @param q_max_msgs Maximum number of messages the queue can hold
 * @param q_align Alignment of the message queue's buffer (power of 2)
 */
#define K_MSGQ_DEFINE(q_name, q_msg_size, q_max_msgs, q_align)      \
	static char __noinit __aligned(q_align)                     \
		_k_fifo_buf_##q_name[(q_max_msgs) * (q_msg_size)];  \
	struct k_msgq q_name                                        \
		__in_section(_k_msgq, static, q_name) =        \
	       K_MSGQ_INITIALIZER(q_name, _k_fifo_buf_##q_name,     \
				  q_msg_size, q_max_msgs)

/**
 * @brief Initialize a message queue.
 *
 * @param q Pointer to the message queue object.
 * @param buffer Pointer to memory area that holds queued messages.
 * @param msg_size Message size, in bytes.
 * @param max_msgs Maximum number of messages that can be queued.
 *
 * @return N/A
 */
extern void k_msgq_init(struct k_msgq *q, char *buffer,
			size_t msg_size, uint32_t max_msgs);

/**
 * @brief Add a message to a message queue.
 *
 * This routine adds an item to the message queue. When the message queue is
 * full, the routine will wait either for space to become available, or until
 * the specified time limit is reached.
 *
 * @param q Pointer to the message queue object.
 * @param data Pointer to message data area.
 * @param timeout Number of milliseconds to wait until space becomes available
 *                to add the message into the message queue, or one of the
 *                special values K_NO_WAIT and K_FOREVER.
 *
 * @return 0 if successful, -ENOMSG if failed immediately or after queue purge,
 *         -EAGAIN if timed out
 *
 * @sa K_NO_WAIT, K_FOREVER
 */
extern int k_msgq_put(struct k_msgq *q, void *data, int32_t timeout);

/**
 * @brief Obtain a message from a message queue.
 *
 * This routine fetches the oldest item from the message queue. When the message
 * queue is found empty, the routine will wait either until an item is added to
 * the message queue or until the specified time limit is reached.
 *
 * @param q Pointer to the message queue object.
 * @param data Pointer to message data area.
 * @param timeout Number of milliseconds to wait to obtain message, or one of
 *                the special values K_NO_WAIT and K_FOREVER.
 *
 * @return 0 if successful, -ENOMSG if failed immediately, -EAGAIN if timed out
 *
 * @sa K_NO_WAIT, K_FOREVER
 */
extern int k_msgq_get(struct k_msgq *q, void *data, int32_t timeout);

/**
 * @brief Purge contents of a message queue.
 *
 * Discards all messages currently in the message queue, and cancels
 * any "add message" operations initiated by waiting threads.
 *
 * @param q Pointer to the message queue object.
 *
 * @return N/A
 */
extern void k_msgq_purge(struct k_msgq *q);

/**
 * @brief Get the number of unused messages
 *
 * @param q Message queue to query
 *
 * @return Number of unused messages
 */
static inline uint32_t k_msgq_num_free_get(struct k_msgq *q)
{
	return q->max_msgs - q->used_msgs;
}

/**
 * @brief Get the number of used messages
 *
 * @param q Message queue to query
 *
 * @return Number of used messages
 */
static inline uint32_t k_msgq_num_used_get(struct k_msgq *q)
{
	return q->used_msgs;
}

struct k_mem_block {
	struct k_mem_pool *pool_id;
	void *addr_in_pool;
	void *data;
	size_t req_size;
};

/* mailboxes */

struct k_mbox_msg {
	/** internal use only - needed for legacy API support */
	uint32_t _mailbox;
	/** size of message (in bytes) */
	size_t size;
	/** application-defined information value */
	uint32_t info;
	/** sender's message data buffer */
	void *tx_data;
	/** internal use only - needed for legacy API support */
	void *_rx_data;
	/** message data block descriptor */
	struct k_mem_block tx_block;
	/** source thread id */
	k_tid_t rx_source_thread;
	/** target thread id */
	k_tid_t tx_target_thread;
	/** internal use only - thread waiting on send (may be a dummy) */
	k_tid_t _syncing_thread;
#if (CONFIG_NUM_MBOX_ASYNC_MSGS > 0)
	/** internal use only - semaphore used during asynchronous send */
	struct k_sem *_async_sem;
#endif
};

struct k_mbox {
	_wait_q_t tx_msg_queue;
	_wait_q_t rx_msg_queue;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_mbox);
};

#define K_MBOX_INITIALIZER(obj) \
	{ \
	.tx_msg_queue = SYS_DLIST_STATIC_INIT(&obj.tx_msg_queue), \
	.rx_msg_queue = SYS_DLIST_STATIC_INIT(&obj.rx_msg_queue), \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @brief Define a mailbox
 *
 * This declares and initializes a mailbox. The new mailbox can be passed to
 * the kernel's mailbox functions.
 *
 * If the mailbox is to be accessed outside the module where it is defined, it
 * can be declared via
 *
 *    extern struct k_mbox @a name;
 *
 * @param name Name of the mailbox
 */
#define K_MBOX_DEFINE(name) \
	struct k_mbox name \
		__in_section(_k_mbox, static, name) = \
		K_MBOX_INITIALIZER(name) \

/**
 * @brief Initialize a mailbox.
 *
 * @param mbox Pointer to the mailbox object
 *
 * @return N/A
 */
extern void k_mbox_init(struct k_mbox *mbox);

/**
 * @brief Send a mailbox message in a synchronous manner.
 *
 * Sends a message to a mailbox and waits for a receiver to process it.
 * The message data may be in a buffer, in a memory pool block, or non-existent
 * (i.e. empty message).
 *
 * @param mbox Pointer to the mailbox object.
 * @param tx_msg Pointer to transmit message descriptor.
 * @param timeout Maximum time (milliseconds) to wait for the message to be
 *        received (although not necessarily completely processed).
 *        Use K_NO_WAIT to return immediately, or K_FOREVER to wait as long
 *        as necessary.
 *
 * @return 0 if successful, -ENOMSG if failed immediately, -EAGAIN if timed out
 */
extern int k_mbox_put(struct k_mbox *mbox, struct k_mbox_msg *tx_msg,
		      int32_t timeout);

#if (CONFIG_NUM_MBOX_ASYNC_MSGS > 0)
/**
 * @brief Send a mailbox message in an asynchronous manner.
 *
 * Sends a message to a mailbox without waiting for a receiver to process it.
 * The message data may be in a buffer, in a memory pool block, or non-existent
 * (i.e. an empty message). Optionally, the specified semaphore will be given
 * by the mailbox when the message has been both received and disposed of
 * by the receiver.
 *
 * @param mbox Pointer to the mailbox object.
 * @param tx_msg Pointer to transmit message descriptor.
 * @param sem Semaphore identifier, or NULL if none specified.
 *
 * @return N/A
 */
extern void k_mbox_async_put(struct k_mbox *mbox, struct k_mbox_msg *tx_msg,
			     struct k_sem *sem);
#endif

/**
 * @brief Receive a mailbox message.
 *
 * Receives a message from a mailbox, then optionally retrieves its data
 * and disposes of the message.
 *
 * @param mbox Pointer to the mailbox object.
 * @param rx_msg Pointer to receive message descriptor.
 * @param buffer Pointer to buffer to receive data.
 *        (Use NULL to defer data retrieval and message disposal until later.)
 * @param timeout Maximum time (milliseconds) to wait for a message.
 *        Use K_NO_WAIT to return immediately, or K_FOREVER to wait as long as
 *        necessary.
 *
 * @return 0 if successful, -ENOMSG if failed immediately, -EAGAIN if timed out
 */
extern int k_mbox_get(struct k_mbox *mbox, struct k_mbox_msg *rx_msg,
		      void *buffer, int32_t timeout);

/**
 * @brief Retrieve mailbox message data into a buffer.
 *
 * Completes the processing of a received message by retrieving its data
 * into a buffer, then disposing of the message.
 *
 * Alternatively, this routine can be used to dispose of a received message
 * without retrieving its data.
 *
 * @param rx_msg Pointer to receive message descriptor.
 * @param buffer Pointer to buffer to receive data. (Use NULL to discard data.)
 *
 * @return N/A
 */
extern void k_mbox_data_get(struct k_mbox_msg *rx_msg, void *buffer);

/**
 * @brief Retrieve mailbox message data into a memory pool block.
 *
 * Completes the processing of a received message by retrieving its data
 * into a memory pool block, then disposing of the message. The memory pool
 * block that results from successful retrieval must be returned to the pool
 * once the data has been processed, even in cases where zero bytes of data
 * are retrieved.
 *
 * Alternatively, this routine can be used to dispose of a received message
 * without retrieving its data. In this case there is no need to return a
 * memory pool block to the pool.
 *
 * This routine allocates a new memory pool block for the data only if the
 * data is not already in one. If a new block cannot be allocated, the routine
 * returns a failure code and the received message is left unchanged. This
 * permits the caller to reattempt data retrieval at a later time or to dispose
 * of the received message without retrieving its data.
 *
 * @param rx_msg Pointer to receive message descriptor.
 * @param pool Memory pool identifier. (Use NULL to discard data.)
 * @param block Pointer to area to hold memory pool block info.
 * @param timeout Maximum time (milliseconds) to wait for a memory pool block.
 *        Use K_NO_WAIT to return immediately, or K_FOREVER to wait as long as
 *        necessary.
 *
 * @return 0 if successful, -ENOMEM if failed immediately, -EAGAIN if timed out
 */
extern int k_mbox_data_block_get(struct k_mbox_msg *rx_msg,
				 struct k_mem_pool *pool,
				 struct k_mem_block *block, int32_t timeout);

/* pipes */

struct k_pipe {
	unsigned char *buffer;          /* Pipe buffer: may be NULL */
	size_t         size;            /* Buffer size */
	size_t         bytes_used;      /* # bytes used in buffer */
	size_t         read_index;      /* Where in buffer to read from */
	size_t         write_index;     /* Where in buffer to write */

	struct {
		_wait_q_t      readers; /* Reader wait queue */
		_wait_q_t      writers; /* Writer wait queue */
	} wait_q;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_pipe);
};

#define K_PIPE_INITIALIZER(obj, pipe_buffer, pipe_buffer_size)        \
	{                                                             \
	.buffer = pipe_buffer,                                        \
	.size = pipe_buffer_size,                                     \
	.bytes_used = 0,                                              \
	.read_index = 0,                                              \
	.write_index = 0,                                             \
	.wait_q.writers = SYS_DLIST_STATIC_INIT(&obj.wait_q.writers), \
	.wait_q.readers = SYS_DLIST_STATIC_INIT(&obj.wait_q.readers), \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT                            \
	}

/**
 * @brief Define a pipe
 *
 * This declares and initializes a pipe. The new pipe can be passed to
 * the kernel's pipe functions.
 *
 * If the pipe is to be accessed outside the module where it is defined, it
 * can be declared via
 *
 *    extern struct k_pipe @a name;
 *
 * @param name Name of the mailbox
 * @param pipe_buffer_size Size of the pipe's buffer (may be zero)
 * @param pipe_align Alignment of the pipe's buffer
 */
#define K_PIPE_DEFINE(name, pipe_buffer_size, pipe_align)     \
	static unsigned char __noinit __aligned(pipe_align)   \
		_k_pipe_buf_##name[pipe_buffer_size];         \
	struct k_pipe name                                    \
		__in_section(_k_pipe, static, name) =    \
		K_PIPE_INITIALIZER(name, _k_pipe_buf_##name, pipe_buffer_size)

/**
 * @brief Runtime initialization of a pipe
 *
 * @param pipe Pointer to pipe to initialize
 * @param buffer Pointer to buffer to use for pipe's ring buffer
 * @param size Size of the pipe's ring buffer
 *
 * @return N/A
 */
extern void k_pipe_init(struct k_pipe *pipe, unsigned char *buffer,
			size_t size);

/**
 * @brief Put a message into the specified pipe
 *
 * This routine synchronously adds a message into the pipe specified by
 * @a pipe. It will wait up to @a timeout for the pipe to accept
 * @a bytes_to_write bytes of data. If by @a timeout, the pipe could not
 * accept @a min_xfer bytes of data, it fails. Fewer than @a min_xfer will
 * only ever be written to the pipe if K_NO_WAIT < @a timeout < K_FOREVER.
 *
 * @param pipe Pointer to the pipe
 * @param data Data to put into the pipe
 * @param bytes_to_write Desired number of bytes to put into the pipe
 * @param bytes_written Number of bytes the pipe accepted
 * @param min_xfer Minimum number of bytes accepted for success
 * @param timeout Maximum number of milliseconds to wait
 *
 * @retval 0 At least @a min_xfer were sent
 * @retval -EIO Request can not be satisfied (@a timeout is K_NO_WAIT)
 * @retval -EAGAIN Fewer than @a min_xfer were sent
 */
extern int k_pipe_put(struct k_pipe *pipe, void *data,
		      size_t bytes_to_write, size_t *bytes_written,
		      size_t min_xfer, int32_t timeout);

/**
 * @brief Get a message from the specified pipe
 *
 * This routine synchronously retrieves a message from the pipe specified by
 * @a pipe. It will wait up to @a timeout to retrieve @a bytes_to_read
 * bytes of data from the pipe. If by @a timeout, the pipe could not retrieve
 * @a min_xfer bytes of data, it fails. Fewer than @a min_xfer will
 * only ever be retrieved from the pipe if K_NO_WAIT < @a timeout < K_FOREVER.
 *
 * @param pipe Pointer to the pipe
 * @param data Location to place retrieved data
 * @param bytes_to_read Desired number of bytes to retrieve from the pipe
 * @param bytes_read Number of bytes retrieved from the pipe
 * @param min_xfer Minimum number of bytes retrieved for success
 * @param timeout Maximum number of milliseconds to wait
 *
 * @retval 0 At least @a min_xfer were transferred
 * @retval -EIO Request can not be satisfied (@a timeout is K_NO_WAIT)
 * @retval -EAGAIN Fewer than @a min_xfer were retrieved
 */
extern int k_pipe_get(struct k_pipe *pipe, void *data,
		      size_t bytes_to_read, size_t *bytes_read,
		      size_t min_xfer, int32_t timeout);

#if (CONFIG_NUM_PIPE_ASYNC_MSGS > 0)
/**
 * @brief Send a message to the specified pipe
 *
 * This routine asynchronously sends a message from the pipe specified by
 * @a pipe. Once all @a size bytes have been accepted by the pipe, it will
 * free the memory block @a block and give the semaphore @a sem (if specified).
 * Up to CONFIG_NUM_PIPE_ASYNC_MSGS asynchronous pipe messages can be in-flight
 * at any given time.
 *
 * @param pipe Pointer to the pipe
 * @param block Memory block containing data to send
 * @param size Number of data bytes in memory block to send
 * @param sem Semaphore to signal upon completion (else NULL)
 *
 * @retval N/A
 */
extern void k_pipe_block_put(struct k_pipe *pipe, struct k_mem_block *block,
			     size_t size, struct k_sem *sem);
#endif

/**
 *  memory management
 */

/* memory slabs */

struct k_mem_slab {
	_wait_q_t wait_q;
	uint32_t num_blocks;
	size_t block_size;
	char *buffer;
	char *free_list;
	uint32_t num_used;

	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_mem_slab);
};

#define K_MEM_SLAB_INITIALIZER(obj, slab_buffer, slab_block_size, \
			       slab_num_blocks) \
	{ \
	.wait_q = SYS_DLIST_STATIC_INIT(&obj.wait_q), \
	.num_blocks = slab_num_blocks, \
	.block_size = slab_block_size, \
	.buffer = slab_buffer, \
	.free_list = NULL, \
	.num_used = 0, \
	_DEBUG_TRACING_KERNEL_OBJECTS_INIT \
	}

/**
 * @brief Define a memory slab allocator
 *
 * This declares and initializes a slab allocator whose buffer is aligned to
 * a @a slab_align -byte boundary. The new slab allocator can be passed to the
 * kernel's memory slab functions.
 *
 * Note that for each of the blocks in the memory slab to be aligned to
 * @a slab_align bytes, then @a slab_block_size must be a multiple of
 * @a slab_align.
 *
 * If the slab allocator is to be accessed outside the module where it is
 * defined, it can be declared via
 *
 *    extern struct k_mem_slab @a name;
 *
 * @param name Name of the memory slab
 * @param slab_block_size Size of each block in the buffer (in bytes)
 * @param slab_num_blocks Number blocks in the buffer
 * @param slab_align Alignment of the memory slab's buffer (power of 2)
 */
#define K_MEM_SLAB_DEFINE(name, slab_block_size, slab_num_blocks, slab_align) \
	char __noinit __aligned(slab_align) \
		_k_mem_slab_buf_##name[(slab_num_blocks) * (slab_block_size)]; \
	struct k_mem_slab name \
		__in_section(_k_mem_slab, static, name) = \
		K_MEM_SLAB_INITIALIZER(name, _k_mem_slab_buf_##name, \
				      slab_block_size, slab_num_blocks)

/**
 * @brief Initialize a memory slab.
 *
 * Initializes the memory slab and creates its list of free blocks.
 *
 * @param slab Pointer to the memory slab object
 * @param buffer Pointer to buffer used for the blocks.
 * @param block_size Size of each block, in bytes.
 * @param num_blocks Number of blocks.
 *
 * @return N/A
 */
extern void k_mem_slab_init(struct k_mem_slab *slab, void *buffer,
			   size_t block_size, uint32_t num_blocks);

/**
 * @brief Allocate a memory slab block.
 *
 * Takes a block from the list of unused blocks.
 *
 * @param slab Pointer to memory slab object.
 * @param mem Pointer to area to receive block address.
 * @param timeout Maximum time (milliseconds) to wait for allocation to
 *        complete.  Use K_NO_WAIT to return immediately, or K_FOREVER to wait
 *        as long as necessary.
 *
 * @return 0 if successful, -ENOMEM if failed immediately, -EAGAIN if timed out
 */
extern int k_mem_slab_alloc(struct k_mem_slab *slab, void **mem,
			    int32_t timeout);

/**
 * @brief Free a memory slab block.
 *
 * Gives block to a waiting thread if there is one, otherwise returns it to
 * the list of unused blocks.
 *
 * @param slab Pointer to memory slab object.
 * @param mem Pointer to area to containing block address.
 *
 * @return N/A
 */
extern void k_mem_slab_free(struct k_mem_slab *slab, void **mem);

/**
 * @brief Get the number of used memory blocks
 *
 * This routine gets the current number of used memory blocks in the
 * specified pool. It should be used for stats purposes only as that
 * value may potentially be out-of-date by the time it is used.
 *
 * @param slab Memory slab to query
 *
 * @return Number of used memory blocks
 */
static inline uint32_t k_mem_slab_num_used_get(struct k_mem_slab *slab)
{
	return slab->num_used;
}

/**
 * @brief Get the number of unused memory blocks
 *
 * This routine gets the current number of unused memory blocks in the
 * specified pool. It should be used for stats purposes only as that value
 * may potentially be out-of-date by the time it is used.
 *
 * @param slab Memory slab to query
 *
 * @return Number of unused memory blocks
 */
static inline uint32_t k_mem_slab_num_free_get(struct k_mem_slab *slab)
{
	return slab->num_blocks - slab->num_used;
}

/* memory pools */

/*
 * Memory pool requires a buffer and two arrays of structures for the
 * memory block accounting:
 * A set of arrays of k_mem_pool_quad_block structures where each keeps a
 * status of four blocks of memory.
 */
struct k_mem_pool_quad_block {
	char *mem_blocks; /* pointer to the first of four memory blocks */
	uint32_t mem_status; /* four bits. If bit is set, memory block is
				allocated */
};
/*
 * Memory pool mechanism uses one array of k_mem_pool_quad_block for accounting
 * blocks of one size. Block sizes go from maximal to minimal. Next memory
 * block size is 4 times less than the previous one and thus requires 4 times
 * bigger array of k_mem_pool_quad_block structures to keep track of the
 * memory blocks.
 */

/*
 * The array of k_mem_pool_block_set keeps the information of each array of
 * k_mem_pool_quad_block structures
 */
struct k_mem_pool_block_set {
	size_t block_size; /* memory block size */
	uint32_t nr_of_entries; /* nr of quad block structures in the array */
	struct k_mem_pool_quad_block *quad_block;
	int count;
};

/* Memory pool descriptor */
struct k_mem_pool {
	size_t max_block_size;
	size_t min_block_size;
	uint32_t nr_of_maxblocks;
	uint32_t nr_of_block_sets;
	struct k_mem_pool_block_set *block_set;
	char *bufblock;
	_wait_q_t wait_q;
	_DEBUG_TRACING_KERNEL_OBJECTS_NEXT_PTR(k_mem_pool);
};

#ifdef CONFIG_ARM
#define _SECTION_TYPE_SIGN "%"
#else
#define _SECTION_TYPE_SIGN "@"
#endif

/*
 * Static memory pool initialization
 */
/*
 * Use .altmacro to be able to recalculate values and pass them as string
 * arguments when calling assembler macros resursively
 */
__asm__(".altmacro\n\t");

/*
 * Recursively calls a macro
 * The followig global symbols need to be initialized:
 * __memory_pool_max_block_size - maximal size of the memory block
 * __memory_pool_min_block_size - minimal size of the memory block
 * Notes:
 * Global symbols are used due the fact that assembler macro allows only
 * one argument be passed with the % conversion
 * Some assemblers do not get division operation ("/"). To avoid it >> 2
 * is used instead of / 4.
 * n_max argument needs to go first in the invoked macro, as some
 * assemblers concatenate \name and %(\n_max * 4) arguments
 * if \name goes first
 */
__asm__(".macro __do_recurse macro_name, name, n_max\n\t"
	".ifge __memory_pool_max_block_size >> 2 -"
	" __memory_pool_min_block_size\n\t\t"
	"__memory_pool_max_block_size = __memory_pool_max_block_size >> 2\n\t\t"
	"\\macro_name %(\\n_max * 4) \\name\n\t"
	".endif\n\t"
	".endm\n");

/*
 * Build quad blocks
 * Macro allocates space in memory for the array of k_mem_pool_quad_block
 * structures and recursively calls itself for the next array, 4 times
 * larger.
 * The followig global symbols need to be initialized:
 * __memory_pool_max_block_size - maximal size of the memory block
 * __memory_pool_min_block_size - minimal size of the memory block
 * __memory_pool_quad_block_size - sizeof(struct k_mem_pool_quad_block)
 */
__asm__(".macro _build_quad_blocks n_max, name\n\t"
	".balign 4\n\t"
	"_mem_pool_quad_blocks_\\name\\()_\\n_max:\n\t"
	".skip __memory_pool_quad_block_size * \\n_max >> 2\n\t"
	".if \\n_max % 4\n\t\t"
	".skip __memory_pool_quad_block_size\n\t"
	".endif\n\t"
	"__do_recurse _build_quad_blocks \\name \\n_max\n\t"
	".endm\n");

/*
 * Build block sets and initialize them
 * Macro initializes the k_mem_pool_block_set structure and
 * recursively calls itself for the next one.
 * The followig global symbols need to be initialized:
 * __memory_pool_max_block_size - maximal size of the memory block
 * __memory_pool_min_block_size - minimal size of the memory block
 * __memory_pool_block_set_count, the number of the elements in the
 * block set array must be set to 0. Macro calculates it's real
 * value.
 * Since the macro initializes pointers to an array of k_mem_pool_quad_block
 * structures, _build_quad_blocks must be called prior it.
 */
__asm__(".macro _build_block_set n_max, name\n\t"
	".int __memory_pool_max_block_size\n\t" /* block_size */
	".if \\n_max % 4\n\t\t"
	".int \\n_max >> 2 + 1\n\t" /* nr_of_entries */
	".else\n\t\t"
	".int \\n_max >> 2\n\t"
	".endif\n\t"
	".int _mem_pool_quad_blocks_\\name\\()_\\n_max\n\t" /* quad_block */
	".int 0\n\t" /* count */
	"__memory_pool_block_set_count = __memory_pool_block_set_count + 1\n\t"
	"__do_recurse _build_block_set \\name \\n_max\n\t"
	".endm\n");

/*
 * Build a memory pool structure and initialize it
 * Macro uses __memory_pool_block_set_count global symbol,
 * block set addresses and buffer address, it may be called only after
 * _build_block_set
 */
__asm__(".macro _build_mem_pool name, min_size, max_size, n_max\n\t"
	".pushsection ._k_mem_pool.static.\\name,\"aw\","
	_SECTION_TYPE_SIGN "progbits\n\t"
	".globl \\name\n\t"
	"\\name:\n\t"
	".int \\max_size\n\t" /* max_block_size */
	".int \\min_size\n\t" /* min_block_size */
	".int \\n_max\n\t" /* nr_of_maxblocks */
	".int __memory_pool_block_set_count\n\t" /* nr_of_block_sets */
	".int _mem_pool_block_sets_\\name\n\t" /* block_set */
	".int _mem_pool_buffer_\\name\n\t" /* bufblock */
	".int 0\n\t" /* wait_q->head */
	".int 0\n\t" /* wait_q->next */
	".popsection\n\t"
	".endm\n");

#define _MEMORY_POOL_QUAD_BLOCK_DEFINE(name, min_size, max_size, n_max) \
	__asm__(".pushsection ._k_memory_pool.struct,\"aw\","		\
		_SECTION_TYPE_SIGN "progbits\n\t");			\
	__asm__("__memory_pool_min_block_size = " STRINGIFY(min_size) "\n\t"); \
	__asm__("__memory_pool_max_block_size = " STRINGIFY(max_size) "\n\t"); \
	__asm__("_build_quad_blocks " STRINGIFY(n_max) " "		\
		STRINGIFY(name) "\n\t");				\
	__asm__(".popsection\n\t")

#define _MEMORY_POOL_BLOCK_SETS_DEFINE(name, min_size, max_size, n_max) \
	__asm__("__memory_pool_block_set_count = 0\n\t");		\
	__asm__("__memory_pool_max_block_size = " STRINGIFY(max_size) "\n\t"); \
	__asm__(".pushsection ._k_memory_pool.struct,\"aw\","		\
		_SECTION_TYPE_SIGN "progbits\n\t");			\
	__asm__(".balign 4\n\t");			\
	__asm__("_mem_pool_block_sets_" STRINGIFY(name) ":\n\t");	\
	__asm__("_build_block_set " STRINGIFY(n_max) " "		\
		STRINGIFY(name) "\n\t");				\
	__asm__("_mem_pool_block_set_count_" STRINGIFY(name) ":\n\t");	\
	__asm__(".int __memory_pool_block_set_count\n\t");		\
	__asm__(".popsection\n\t");					\
	extern uint32_t _mem_pool_block_set_count_##name;		\
	extern struct k_mem_pool_block_set _mem_pool_block_sets_##name[]

#define _MEMORY_POOL_BUFFER_DEFINE(name, max_size, n_max, align)	\
	char __noinit __aligned(align)                                  \
		_mem_pool_buffer_##name[(max_size) * (n_max)]

/**
 * @brief Define a memory pool
 *
 * This declares and initializes a memory pool whose buffer is aligned to
 * a @a align -byte boundary. The new memory pool can be passed to the
 * kernel's memory pool functions.
 *
 * Note that for each of the minimum sized blocks to be aligned to @a align
 * bytes, then @a min_size must be a multiple of @a align.
 *
 * If the pool is to be accessed outside the module where it is defined, it
 * can be declared via
 *
 *    extern struct k_mem_pool @a name;
 *
 * @param name Name of the memory pool
 * @param min_size Minimum block size in the pool
 * @param max_size Maximum block size in the pool
 * @param n_max Number of maximum sized blocks in the pool
 * @param align Alignment of the memory pool's buffer
 */
#define K_MEM_POOL_DEFINE(name, min_size, max_size, n_max, align)     \
	_MEMORY_POOL_QUAD_BLOCK_DEFINE(name, min_size, max_size, n_max); \
	_MEMORY_POOL_BLOCK_SETS_DEFINE(name, min_size, max_size, n_max); \
	_MEMORY_POOL_BUFFER_DEFINE(name, max_size, n_max, align);        \
	__asm__("_build_mem_pool " STRINGIFY(name) " " STRINGIFY(min_size) " " \
	       STRINGIFY(max_size) " " STRINGIFY(n_max) "\n\t");	\
	extern struct k_mem_pool name

/*
 * Dummy function that assigns the value of sizeof(struct k_mem_pool_quad_block)
 * to __memory_pool_quad_block_size absolute symbol.
 * This function does not get called, but compiler calculates the value and
 * assigns it to the absolute symbol, that, in turn is used by assembler macros.
 */
static void __attribute__ ((used)) __k_mem_pool_quad_block_size_define(void)
{
	__asm__(".globl __memory_pool_quad_block_size\n\t"
#ifdef CONFIG_NIOS2
	    "__memory_pool_quad_block_size = %0\n\t"
#else
	    "__memory_pool_quad_block_size = %c0\n\t"
#endif
	    :
	    : "n"(sizeof(struct k_mem_pool_quad_block)));
}

/**
 * @brief Allocate memory from a memory pool
 *
 * @param pool Pointer to the memory pool object
 * @param block Pointer to the allocated memory's block descriptor
 * @param size Minimum number of bytes to allocate
 * @param timeout Maximum time (milliseconds) to wait for operation to
 *        complete. Use K_NO_WAIT to return immediately, or K_FOREVER
 *        to wait as long as necessary.
 *
 * @return 0 on success, -ENOMEM on failure
 */
extern int k_mem_pool_alloc(struct k_mem_pool *pool, struct k_mem_block *block,
			    size_t size, int32_t timeout);

/**
 * @brief Return previously allocated memory to its memory pool
 *
 * @param block Pointer to allocated memory's block descriptor
 *
 * @return N/A
 */
extern void k_mem_pool_free(struct k_mem_block *block);

/**
 * @brief Defragment the specified memory pool
 *
 * @param pool Pointer to the memory pool object
 *
 * @return N/A
 */
extern void k_mem_pool_defrag(struct k_mem_pool *pool);

/**
 * @brief Allocate memory from heap
 *
 * This routine provides traditional malloc() semantics. The memory is
 * allocated from the heap memory pool.
 *
 * @param size Size of memory requested by the caller (in bytes)
 *
 * @return Address of the allocated memory on success; otherwise NULL
 */
extern void *k_malloc(size_t size);

/**
 * @brief Free memory allocated from heap
 *
 * This routine provides traditional free() semantics. The memory being
 * returned must have been allocated from the heap memory pool.
 *
 * @param ptr Pointer to previously allocated memory
 *
 * @return N/A
 */
extern void k_free(void *ptr);

/*
 * legacy.h must be before arch/cpu.h to allow the ioapic/loapic drivers to
 * hook into the device subsystem, which itself uses nanokernel semaphores,
 * and thus currently requires the definition of nano_sem.
 */
#include <legacy.h>
#include <arch/cpu.h>

/*
 * private APIs that are utilized by one or more public APIs
 */

extern int _is_thread_essential(void);
extern void _init_static_threads(void);
extern void _timer_expiration_handler(struct _timeout *t);

#ifdef __cplusplus
}
#endif

#endif /* _kernel__h_ */