mbed_shared_queues.h

00001 /*
00002  * Copyright (c) 2016-2019 ARM Limited
00003  *
00004  * Licensed under the Apache License, Version 2.0 (the "License");
00005  * you may not use this file except in compliance with the License.
00006  * You may obtain a copy of the License at
00007  *
00008  *     http://www.apache.org/licenses/LICENSE-2.0
00009  *
00010  * Unless required by applicable law or agreed to in writing, software
00011  * distributed under the License is distributed on an "AS IS" BASIS,
00012  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
00013  * See the License for the specific language governing permissions and
00014  * limitations under the License.
00015  */
00016 #ifndef MBED_SHARED_QUEUES_H
00017 #define MBED_SHARED_QUEUES_H
00018 
00019 #include "events/EventQueue.h"
00020 
00021 namespace mbed {
00022 /** \addtogroup events-public-api */
00023 /** @{*/
00024 
00025 /**
00026  * Return a pointer to an EventQueue, on which normal tasks can be queued.
00027  *
00028  * All calls to this return the same EventQueue - it and its dispatch thread
00029  * are created on the first call to this function. The dispatch thread
00030  * runs at default priority (currently osPriorityNormal).
00031  *
00032  * The EventQueue returned may be used to call() Events, or to chain() other
00033  * EventQueues so that they are run in the same context.
00034  *
00035  * Events (or chained EventQueues) executing on the normal event queue should
00036  * normally take less than 10ms to execute, to avoid starving other users. As
00037  * such, users can expect that event latency will typically be 10ms or less,
00038  * but could occasionally be significantly higher if many events are queued.
00039  *
00040  * If an RTOS is not present or the configuration option
00041  * `events.shared-dispatch-from-application` is set to true, then this
00042  * does not create a dedicated dispatch thread - instead the application is
00043  * expected to run the EventQueue's dispatch, for example from main. This is
00044  * necessary for the event loop to work without an RTOS, or an RTOS system can
00045  * save memory by reusing the main stack.
00046  *
00047  * @note
00048  * mbed_event_queue is not itself IRQ safe. To use the mbed_event_queue in
00049  * interrupt context, you must first call `mbed_event_queue()` in threaded
00050  * context and store the pointer for later use.
00051  *
00052  * @return pointer to event queue
00053  */
00054 events::EventQueue *mbed_event_queue();
00055 
00056 #ifdef MBED_CONF_RTOS_PRESENT
00057 /**
00058  * Return a pointer to an EventQueue, on which small high-priority tasks can
00059  * be queues, such as simple deferrals from interrupt.
00060  *
00061  * All calls to this return the same EventQueue - it and its thread are
00062  * created on the first call to this function. The dispatch thread
00063  * runs at a high priority (currently osPriorityHigh).
00064  *
00065  * The EventQueue returned may be used to call() Events, or to chain() other
00066  * EventQueues so that they are run in the same context.
00067  *
00068  * Events (or chained EventQueues) executing on the high-priority event queue
00069  * should normally take less than 100us to execute, to avoid starving other
00070  * users. As such, users can expect that event latency will typically be 100us
00071  * or less, but could occasionally be significantly higher if many events are
00072  * queued.
00073  *
00074  * @note
00075  * mbed_highprio_event_queue is not itself IRQ safe. To use the
00076  * mbed_highprio_event_queue in interrupt context, you must first call
00077  * `mbed_highprio_event_queue()` in threaded context and store the pointer for
00078  * later use.
00079  *
00080  * @return pointer to high-priority event queue
00081  */
00082 
00083 events::EventQueue *mbed_highprio_event_queue();
00084 
00085 #endif // MBED_CONF_RTOS_PRESENT
00086 
00087 /** @}*/
00088 
00089 }
00090 
00091 #endif