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+/*

+    ChibiOS/RT - Copyright (C) 2006-2007 Giovanni Di Sirio.

+

+    This file is part of ChibiOS/RT.

+

+    ChibiOS/RT is free software; you can redistribute it and/or modify

+    it under the terms of the GNU General Public License as published by

+    the Free Software Foundation; either version 3 of the License, or

+    (at your option) any later version.

+

+    ChibiOS/RT is distributed in the hope that it will be useful,

+    but WITHOUT ANY WARRANTY; without even the implied warranty of

+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

+    GNU General Public License for more details.

+

+    You should have received a copy of the GNU General Public License

+    along with this program.  If not, see <http://www.gnu.org/licenses/>.

+*/

+

+/**

+ * @defgroup kernel Kernel

+ * The kernel is the portable part of ChibiOS/RT, this section documents the

+ * various kernel subsystems.

+ */

+

+/**

+ * @defgroup kernel_info Version Numbers and Identification

+ * Kernel related settings and hooks.

+ * @ingroup kernel

+ */

+

+/**

+ * @defgroup config Configuration

+ * Kernel related settings and hooks.

+ * @ingroup kernel

+ */

+

+/**

+ * @defgroup types Types

+ * System types and macros.

+ * @ingroup kernel

+ */

+

+/**

+ * @defgroup base Base Kernel Services

+ * Base kernel services, the base subsystems are always included in the

+ * OS builds.

+ * @ingroup kernel

+ */

+

+/**

+ * @defgroup system System Management

+ * Initialization, Locks, Interrupt Handling, Power Management, Abnormal

+ * Termination.

+ * @ingroup base

+ */

+

+/**

+ * @defgroup time Time and Virtual Timers

+ * Time and Virtual Timers related APIs.

+ * @ingroup base

+ */

+

+/**

+ * @defgroup scheduler Scheduler

+ * ChibiOS/RT scheduler APIs and macros.

+ * @ingroup base

+ */

+

+/**

+ * @defgroup threads Threads

+ * Threads related APIs.

+ * @ingroup base

+ */

+

+/**

+ * @defgroup synchronization Synchronization

+ * Synchronization services.

+ * @ingroup kernel

+ */

+

+/**

+ * @defgroup semaphores Semaphores

+ * Semaphores and threads synchronization.

+ * <h2>Operation mode</h2>

+ * A semaphore is a threads synchronization object, some operations

+ * are defined on semaphores:

+ * - <b>Signal</b>: The semaphore counter is increased and if the result

+ *   is non-positive then a waiting thread is removed from the semaphore

+ *   queue and made ready for execution.

+ * - <b>Wait</b>: The semaphore counter is decreased and if the result

+ *   becomes negative the thread is queued in the semaphore and suspended.

+ * - <b>Reset</b>: The semaphore counter is reset to a non-negative value

+ *   and all the threads in the queue are released.

+ * .

+ * Semaphores can be used as guards for mutual exclusion code zones (note that

+ * mutexes are recommended for this kind of use) but also have other uses,

+ * queues guards and counters as example.<br>

+ * Semaphores usually use FIFO queues but it is possible to make them

+ * order threads by priority by specifying CH_USE_SEMAPHORES_PRIORITY in

+ * @p chconf.h.<br>

+ * In order to use the Semaphores APIs the @p CH_USE_SEMAPHORES

+ * option must be specified in @p chconf.h.<br><br>

+ * @ingroup synchronization

+ */

+

+/**

+ * @defgroup mutexes Mutexes

+ * Mutexes and threads synchronization.

+ * <h2>Operation mode</h2>

+ * A mutex is a threads synchronization object, some operations are defined

+ * on mutexes:

+ * - <b>Lock</b>: The mutex is checked, if the mutex is not owned by some

+ *   other thread then it is locked else the current thread is queued on the

+ *   mutex in a list ordered by priority.

+ * - <b>Unlock</b>: The mutex is released by the owner and the highest

+ *   priority thread waiting in the queue, if any, is resumed and made owner

+ *   of the mutex.

+ * .

+ * In order to use the Event APIs the @p CH_USE_MUTEXES option must be

+ * specified in @p chconf.h.<br>

+ *

+ * <h2>Constraints</h2>

+ * In ChibiOS/RT the Unlock operations are always performed in Lock-reverse

+ * order. The Unlock API does not even have a parameter, the mutex to unlock

+ * is taken from an internal stack of owned mutexes.

+ * This both improves the performance and is required by an efficient

+ * implementation of the priority inheritance mechanism.

+ *

+ * <h2>The priority inversion problem</h2>

+ * The mutexes in ChibiOS/RT implements the <b>full</b> priority

+ * inheritance mechanism in order handle the priority inversion problem.<br>

+ * When a thread is queued on a mutex, any thread, directly or indirectly,

+ * holding the mutex gains the same priority of the waiting thread (if their

+ * priority was not already equal or higher). The mechanism works with any

+ * number of nested mutexes and any number of involved threads. The algorithm

+ * complexity (worst case) is N with N equal to the number of nested mutexes.

+ * @ingroup synchronization

+ */

+

+/**

+ * @defgroup condvars Condition Variables

+ * Condition Variables and threads synchronization.

+ * <h2>Operation mode</h2>

+ * The condition variable is a synchronization object meant to be used inside

+ * a zone protected by a @p Mutex. Mutexes and CondVars together can implement

+ * a Monitor construct.<br>

+ * In order to use the Condition Variables APIs the @p CH_USE_CONDVARS

+ * option must be specified in @p chconf.h.<br><br>

+ * @ingroup synchronization

+ */

+

+/**

+ * @defgroup events Event Flags

+ * @brief Event Flags, Event Sources and Event Listeners.

+ * <h2>Operation mode</h2>

+ * Each thread has a mask of pending event flags inside its Thread structure.

+ * Several operations are defined:

+ * - <b>Wait</b>, the invoking thread goes to sleep until a certain AND/OR

+ *   combination of event flags becomes pending.

+ * - <b>Clear</b>, a mask of event flags is cleared from the pending events

+ *   mask, the cleared event flags mask is returned (only the flags that were

+     actually pending and then cleared).

+ * - <b>Signal</b>, an event mask is directly ORed to the mask of the signaled

+ *   thread.

+ * - <b>Broadcast</b>, each thread registered on an Event Source is signaled

+ *   with the event flags specified in its Event Listener.

+ * - <b>Dispatch</b>, an events mask is scanned and for each bit set to one

+ *   an associated handler function is invoked. Bit masks are scanned from bit

+ *   zero upward.

+ * .

+ * An Event Source is a special object that can be "broadcasted" by a thread or

+ * an interrupt service routine. Broadcasting an Event Source has the effect

+ * that all the threads registered on the Event Source will be signaled with

+ * and events mask.<br>

+ * An unlimited number of Event Sources can exists in a system and each

+ * thread can listen on an unlimited number of them.<br><br>

+ * In order to use the Event APIs the @p CH_USE_EVENTS option must be

+ * specified in @p chconf.h.

+ * @ingroup synchronization

+ */

+

+/**

+ * @defgroup messages Synchronous Messages

+ * Synchronous inter-thread messages.

+ * <h2>Operation Mode</h2>

+ * Synchronous messages are an easy to use and fast IPC mechanism, threads

+ * can both serve messages and send messages to other threads, the mechanism

+ * allows data to be carried in both directions. Data is not copied between

+ * the client and server threads but just a pointer passed so the exchange

+ * is very time efficient.<br>

+ * Messages are usually processed in FIFO order but it is possible to process

+ * them in priority order by specifying CH_USE_MESSAGES_PRIORITY

+ * in @p chconf.h.<br>

+ * Threads do not need to allocate space for message queues, the mechanism

+ * just requires two extra pointers in the @p Thread structure (the message

+ * queue header).<br>

+ * In order to use the Messages APIs the @p CH_USE_MESSAGES option must be

+ * specified in @p chconf.h.

+ * @ingroup synchronization

+ */

+

+/**

+ * @defgroup mailboxes Mailboxes

+ * Asynchronous messages.

+ * <h2>Operation mode</h2>

+ * A mailbox is an asynchronous communication mechanism.<br>

+ * The following operations are possible on a mailbox:

+ * - <b>Post</b>: Posts a message on the mailbox in FIFO order.

+ * - <b>Post Ahead</b>: Posts a message on the mailbox with high priority.

+ * - <b>Fetch</b>: A message is fetched from the mailbox and removed from

+ *   the queue.

+ * - <b>Reset</b>: The mailbox is emptied and all the stored messages lost.

+ * .

+ * A message is a variable of type msg_t that is guaranteed to have the

+ * same size of and be compatible with pointers (an explicit cast is needed).

+ * If larger messages need to be exchanged then a pointer to a structure can

+ * be posted in the mailbox but the posting side has no predefined way to

+ * know when the message has been processed. A possible approach is to

+ * allocate memory (from a memory pool as example) from the posting side and

+ * free it on the fetching side. Another approach is to set a "done" flag into

+ * the structure pointed by the message.

+ * @ingroup synchronization

+ */

+

+/**

+ * @defgroup memory Memory Management

+ * Memory Management services.

+ * @ingroup kernel

+ */

+

+/**

+ * @defgroup heap Heap

+ * Heap Allocator related APIs.

+ * <h2>Operation mode</h2>

+ * The heap allocator implements a first-fit strategy and its APIs are

+ * functionally equivalent to the usual @p malloc() and @p free(). The main

+ * difference is that the heap APIs are thread safe.<br>

+ * By enabling the @p CH_USE_MALLOC_HEAP option the heap manager will use the

+ * runtime-provided @p malloc() and @p free() as backend for the heap APIs

+ * instead of the system provided allocator.<br>

+ * In order to use the heap APIs the @p CH_USE_HEAP option must be specified

+ * in @p chconf.h.

+ * @ingroup memory

+ */

+

+/**

+ * @defgroup pools Memory Pools

+ * Memory Pools related APIs.

+ * <h2>Operation mode</h2>

+ * The Memory Pools APIs allow to allocate/free fixed size objects in

+ * <b>constant time</b> and reliably without memory fragmentation problems.<br>

+ * In order to use the Time APIs the @p CH_USE_MEMPOOLS option must be

+ * specified in @p chconf.h.

+ * @ingroup memory

+ */

+

+ /**

+ * @defgroup io_support I/O Support

+ * I/O related services.

+ * @ingroup kernel

+ */

+

+/**

+ * @defgroup io_channels I/O Abstract Channels

+ * @brief Abstract I/O Channels.

+ * @details This module defines an abstract interface for I/O channels. Note

+ * that no code is present, I/O channels are just abstract classes-like

+ * structures, you should look at the systems as to a set of abstract C++

+ * classes (even if written in C). Specific device drivers can use/extend

+ * the interfaces and implement them.<br>

+ * This system has the advantage to make the access to channels

+ * independent from the implementation logic. As example, an I/O channel

+ * interface can hide the access to a serial driver, to a networking socket

+ * and so on.

+ *

+ * @ingroup io_support

+ */

+ 

+/**

+ * @defgroup io_queues I/O Queues

+ * @brief I/O queues.

+ * @details ChibiOS/RT supports several kinds of queues. The queues are mostly

+ * used in serial-like device drivers. The device drivers are usually designed

+ * to have a lower side (lower driver, it is usually an interrupt service

+ * routine) and an upper side (upper driver, accessed by the application

+ * threads).<br>

+ * There are several kind of queues:<br>

+ * - <b>Input queue</b>, unidirectional queue where the writer is the

+ *   lower side and the reader is the upper side.

+ * - <b>Output queue</b>, unidirectional queue where the writer is the

+ *   upper side and the reader is the lower side.

+ * - <b>Full duplex queue</b>, bidirectional queue where read and write

+ *   operations can happen at the same time. Full duplex queues

+ *   are implemented by pairing an input queue and an output queue together.

+ * .

+ * In order to use the I/O queues the @p CH_USE_QUEUES option must

+ * be specified in @p chconf.h.<br>

+ *

+ * @ingroup io_support

+ */

+

+/**

+ * @defgroup debug Debug

+ * Debug APIs and procedures.

+ * @ingroup kernel

+ */

+

+/**

+ * @defgroup core Port Templates

+ * Non portable code templates.

+ * @ingroup kernel

+ */

+

+/**

+ * @defgroup internals Internals

+ * Internal details, not APIs.

+ * @ingroup kernel

+ */

+ 
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