/* 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 . */ /** * @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. *

Operation mode

* A semaphore is a threads synchronization object, some operations * are defined on semaphores: * - Signal: 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. * - Wait: The semaphore counter is decreased and if the result * becomes negative the thread is queued in the semaphore and suspended. * - Reset: 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.
* 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.
* In order to use the Semaphores APIs the @p CH_USE_SEMAPHORES * option must be specified in @p chconf.h.

* @ingroup synchronization */ /** * @defgroup mutexes Mutexes * Mutexes and threads synchronization. *

Operation mode

* A mutex is a threads synchronization object, some operations are defined * on mutexes: * - Lock: 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. * - Unlock: 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.
* *

Constraints

* 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. * *

The priority inversion problem

* The mutexes in ChibiOS/RT implements the full priority * inheritance mechanism in order handle the priority inversion problem.
* 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. *

Operation mode

* 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.
* In order to use the Condition Variables APIs the @p CH_USE_CONDVARS * option must be specified in @p chconf.h.

* @ingroup synchronization */ /** * @defgroup events Event Flags * @brief Event Flags, Event Sources and Event Listeners. *

Operation mode

* Each thread has a mask of pending event flags inside its Thread structure. * Several operations are defined: * - Wait, the invoking thread goes to sleep until a certain AND/OR * combination of event flags becomes pending. * - Clear, 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). * - Signal, an event mask is directly ORed to the mask of the signaled * thread. * - Broadcast, each thread registered on an Event Source is signaled * with the event flags specified in its Event Listener. * - Dispatch, 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.
* An unlimited number of Event Sources can exists in a system and each * thread can listen on an unlimited number of them.

* 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. *

Operation Mode

* 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.
* 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.
* 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).
* 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. *

Operation mode

* A mailbox is an asynchronous communication mechanism.
* The following operations are possible on a mailbox: * - Post: Posts a message on the mailbox in FIFO order. * - Post Ahead: Posts a message on the mailbox with high priority. * - Fetch: A message is fetched from the mailbox and removed from * the queue. * - Reset: 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. *

Operation mode

* 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.
* 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.
* 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. *

Operation mode

* The Memory Pools APIs allow to allocate/free fixed size objects in * constant time and reliably without memory fragmentation problems.
* 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.
* 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).
* There are several kind of queues:
* - Input queue, unidirectional queue where the writer is the * lower side and the reader is the upper side. * - Output queue, unidirectional queue where the writer is the * upper side and the reader is the lower side. * - Full duplex queue, 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.
* * @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 */