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Diffstat (limited to 'cpukit/include/rtems/regulator.h')
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diff --git a/cpukit/include/rtems/regulator.h b/cpukit/include/rtems/regulator.h new file mode 100644 index 0000000000..442040a180 --- /dev/null +++ b/cpukit/include/rtems/regulator.h @@ -0,0 +1,502 @@ +/* SPDX-License-Identifier: BSD-2-Clause */ + +/** + * @file + * + * @ingroup RegulatorAPI + * + * @brief This header file defines the Regulator API. + * + */ + +/* + * Copyright (C) 2023 On-Line Applications Research Corporation (OAR) + * + * Redistribution and use in source and binary forms, with or without + * modification, are permitted provided that the following conditions + * are met: + * 1. Redistributions of source code must retain the above copyright + * notice, this list of conditions and the following disclaimer. + * 2. Redistributions in binary form must reproduce the above copyright + * notice, this list of conditions and the following disclaimer in the + * documentation and/or other materials provided with the distribution. + * + * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" + * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE + * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE + * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE + * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR + * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF + * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS + * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN + * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) + * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE + * POSSIBILITY OF SUCH DAMAGE. + */ + +/** + * @defgroup RegulatorAPI Regulator API + * + * @brief Regulator APIs + * + * The Regulator provides a set of APIs to manage input sources which + * produces bursts of message traffic. + * + * The regulator is designed to sit logically between two entities -- a + * source and a destination, where it limits the traffic sent to the + * destination to prevent it from being flooded with messages from the + * source. This can be used to accommodate bursts of input from a source + * and meter it out to a destination. The maximum number of messages + * which can be buffered in the regulator is specified by the + * @a maximum_messages field in the @a rtems_regulator_attributes + * structure passed as an argument to @a rtems_regulator_create(). + * + * The regulator library accepts an input stream of messages from a + * source and delivers them to a destination. The regulator assumes that the + * input stream from the source contains sporadic bursts of data which can + * exceed the acceptable rate of the destination. By limiting the message rate, + * the regulator prevents an overflow of messages. + * + * The regulator can be configured for the input buffering required to manage + * the maximum burst and for the metering rate for the output. The output rate + * is in messages per second. If the sender produces data too fast, the + * regulator will buffer the configured number of messages. + * + * A configuration capability is provided to allow for adaptation to different + * message streams. The regulator can also support running multiple instances, + * which could be used on independent message streams. + * + * The regulator provides a simple interface to the application for avoiding + * bursts of input from a fast source overflowing a slower destination. + * + * It is assumed that the application has a design limit on the number of + * messages which may be buffered. All messages accepted by the regulator, + * assuming no overflow on input, will eventually be output by the Delivery + * thread. + * + * A regulator instance is used as follows from the producer/source side: + * + * @code + * while (1) + * use rtems_regulator_obtain_buffer to obtain a buffer + * input operation to fetch data into the buffer + * rtems_regulator_send(buffer, size of message) + * @endcode + * + * The delivery of message buffers to the Destination and subsequent + * release is performed in the context of the delivery thread by either + * the delivery function or delivery thread. Details are below. + * + * The sequence diagram below shows the interaction between a message Source, + * a Regulator instance, and RTEMS, given the usage described in the above + * paragraphs. + * + * \startuml "Regulator Application Input Source Usage" + * Source -> Regulator : rtems_regulator_obtain_buffer(regulator, buffer) + * Regulator -> RTEMS : rtems_partition_get_buffer(id, buffer) + * RTEMS --> Regulator : rtems_status_code + * Regulator --> Source : rtems_status_code + * Source -> Regulator : rtems_regulator_send(regulator, message, length) + * Regulator -> RTEMS : rtems_message_queue_send(id, message, size) + * RTEMS --> Regulator : rtems_status_code + * Regulator --> Source : rtems_status_code + * \enduml + * + * As illustrated in the sequence diagram, the Source usually corresponds + * to application software reading a system input. The Source obtains a + * buffer from the Regulator instance and fills it with incoming data. + * The application explicitly obtaining a buffer and filling it in allows + * for zero copy operations on the Source side. + * + * The Source then sends the buffer to the Regulator instance. The Regulator + * the sends the buffer via a message queue which to the Delivery thread. + * The Delivery thread executes periodically at a rate specified at + * Regulation creation. At each period, the Delivery thread attempts to + * receive up to a configured number of buffers and invoke the Delivery + * function to deliver them to the Destination. + * + * The Delivery function is provided by the application for this + * specific Regulator instance. Depending on the Destination, it may use + * a function which copies the buffer contents (e.g., write()) or which + * operates directly on the buffer contents (e.g. DMA from buffer). In + * the case of a Destination which copies the buffer contents, the buffer + * can be released via @a rtems_regulator_release_buffer() as soon as the + * function or copying completes. In the case where the delivery uses the + * buffer and returns, the call to @a rtems_regulator_release_buffer() + * will occur when the use of the buffer is complete (e.g. completion + * of DMA transfer). This explicit and deliberate exposure of buffering + * provides the application with the ability to avoid copying the contents. + * + * After the Source has sent the message to the Regulator instance, + * the Source is free to process another input and the Regulator + * instance will ensure that the buffer is delivered to the Delivery + * function and Destination. + * + * The Regulator implementation uses the RTEMS Classic API Partition Manager + * to manage the buffer pool and the RTEMS Classic API Message Queue + * Manager to send the buffer to the Delivery thread. + */ + +#ifndef REGULATOR_H +#define REGULATOR_H + +#include <stdlib.h> + +#include <rtems.h> + +/** + * @ingroup RegulatorAPI + * + * @brief Regulator Delivery Function Type + * + * The user provides a function which is invoked to deliver a message + * to the output. It is invoked by the Delivery thread created as part + * of @a rtems_regulator_create(). The priority and stack size of the + * Delivery thread are specified in the regulator attribute set. + * + * It takes three parameters: + * + * @param[in] context is an untyped pointer to a user context + * @param[in] message points to the message + * @param[in] length is the message size + * + * The following is an example deliverer function. It assumes that the + * application has defined the my_context_t structure and it has at least + * the socket field. The @a message passed in originated with an + * application source which obtained the @a message buffer using + * @a rtems_regulator_obtain_buffer(), filled it in with source data, + * and used @a rtems_regulator_send() to hand to the regulator instance + * for later delivery. + * + * @code + * bool my_deliverer( + * void *context, + * void *message, + * size_t length + * ) + * { + * my_context_t *my_context; + * + * my_context = (my_context_t *)context; + * + * write(my_context->socket, message, length); + * rtems_regulator_release_buffer(message); + * // return false to indicate we released the buffer + * return false; + * } + * @endcode + * + * The delivery function returns true to indicate that the delivery thread + * should release the buffer or false to indicate that it released the + * buffer. If the delivery function invokes a function like @a write() + * to deliver the message to the destination, then the buffer can be + * released immediately after the call. If the delivery function does + * something like setting up a DMA transfer of the buffer, it cannot be + * released until after the DMA is complete. + * + * The following sequence diagram shows the behavior of the Delivery thread + * body and its interaction with the user-supplied deliverer() function. + * + * \startuml "Regulator Delivery Thread Body" + * loop while (1) + * "Delivery Thread" -> RTEMS : rtems_rate_monotonic_period(id, delivery_thread_period) + * loop for 0 : maximum_to_dequeue_per_period + * "Delivery Thread" -> RTEMS : rtems_message_queue_receive(id, message, size, wait, 0) + * RTEMS --> "Delivery Thread" : rtems_status_code + * group if [rtems_status_code != RTEMS_SUCCESSFUL] + * RTEMS -> "Delivery Thread" : break + * end + * "Delivery Thread" -> Application : deliverer(context, buffer, length) + * "Delivery Thread" -> RTEMS : rtems_partition_return_buffer(id, buffer) + * RTEMS --> "Delivery Thread" : rtems_status_code + * end + * end + * \enduml + * + * In the above sequence diagram, the key points are: + * + * -# The Delivery Thread Body is periodically executed. + * -# During each period, up to the instance configuration parameter + * @a maximum_to_dequeue_per_period may be dequeued and + * passed the application's delivery function for processing. + * + * Note that the application explicitly obtains buffers from the + * regulator instance but that the release may be done by Delivery + * Thread, the Delivery function, or later when the buffer contents + * are transferred. + */ +typedef bool (*rtems_regulator_deliverer)( + void *context, + void *message, + size_t length +); + +/** + * @ingroup RegulatorAPI + * + * @brief Attributes for Regulator Instance + * + * An instance of this structure must be populated by the application + * before creating an instance of the regulator. These settings tailor + * the behavior of the regulator instance. + */ +typedef struct { + /** Application function to invoke to output a message to the destination*/ + rtems_regulator_deliverer deliverer; + + /** Context pointer to pass to deliver function */ + void *deliverer_context; + + /** Maximum size message to process */ + size_t maximum_message_size; + + /** Maximum number of messages to be able to buffer */ + size_t maximum_messages; + + /** Priority of Delivery thread */ + rtems_task_priority delivery_thread_priority; + + /** Stack size of Delivery thread */ + size_t delivery_thread_stack_size; + + /** Period (in ticks) of Delivery thread */ + rtems_interval delivery_thread_period; + + /** Maximum messages to dequeue per period */ + size_t maximum_to_dequeue_per_period; + +} rtems_regulator_attributes; + +/** + * @ingroup RegulatorAPI + * + * @brief Statistics for Regulator Instance + * + * An instance of this structure is provided to the directive + * @a rtems_regulator_get_statistics and is filled in by that service. + */ +typedef struct { + /** Number of successfully obtained buffers. */ + size_t obtained; + + /** Number of successfully released buffers. */ + size_t released; + + /** Number of successfully delivered buffers. */ + size_t delivered; + + /** Rate Monotonic Period statistics for Delivery Thread */ + rtems_rate_monotonic_period_statistics period_statistics; + +} rtems_regulator_statistics; + +/** + * @ingroup RegulatorAPI + * + * @brief Regulator Internal Structure + */ +struct _Regulator_Control; + +/** + * @ingroup RegulatorAPI + * + * @brief Regulator Instance + * + * This is used by the application as the handle to a Regulator instance. + */ +typedef struct _Regulator_Control *rtems_regulator_instance; + +/** + * @ingroup RegulatorAPI + * + * @brief Create a regulator + * + * This function creates an instance of a regulator. It uses the provided + * @a attributes to create the instance return in @a regulator. This instance + * will allocate the buffers associated with the regulator instance as well + * as the Delivery thread. + * + * The @a attributes structure defines the priority and stack size of + * the Delivery thread dedicated to this regulator instance. It also + * defines the period of the Delivery thread and the maximum number of + * messages that may be delivered per period via invocation of the + * delivery function. + * + * For each regulator instance, the following resources are allocated: + * + * - A memory area for the regulator control block using @a malloc(). + * - A RTEMS Classic API Message Queue is constructed with message + * buffer memory allocated using @a malloc(). Each message consists + * of a pointer and a length. + * - A RTEMS Classic API Partition. + * - A RTEMS Classic API Rate Monotonic Period. + * + * @param[in] attributes specify the regulator instance attributes + * @param[inout] regulator will point to the regulator instance + * + * @return an RTEMS status code indicating success or failure. + * + * @note This function allocates memory for the buffers holding messages, + * an Delivery thread and an RTEMS partition. When it executes, the + * Delivery thread will create an RTEMS rate monotonic period. + */ +rtems_status_code rtems_regulator_create( + rtems_regulator_attributes *attributes, + rtems_regulator_instance **regulator +); + +/** + * @ingroup RegulatorAPI + * + * @brief Delete a regulator + * + * This function is used to delete the specified @a regulator instance. + * + * It is the responsibility of the user to ensure that any resources + * such as sockets or open file descriptors used by the delivery + * function are also deleted. It is likely safer to delete those + * delivery resources after deleting the regulator instance rather than + * before. + * + * @param[in] regulator is the instance to delete + * @param[in] ticks is the maximum number of ticks to wait for + * the delivery thread to shutdown. + * + * @return an RTEMS status code indicating success or failure. + * + * @note This function deallocates the resources allocated during + * @a rtems_regulator_create(). + */ +rtems_status_code rtems_regulator_delete( + rtems_regulator_instance *regulator, + rtems_interval ticks +); + +/** + * @ingroup RegulatorAPI + * + * @brief Obtain Buffer from Regulator + * + * This function is used to obtain a buffer from the regulator's pool. The + * @a buffer returned is assumed to be filled in with contents and used + * in a subsequent call to @a rtems_regulator_send(). When the @a buffer is + * delivered, it is expected to be released. If the @a buffer is not + * successfully accepted by this function, then it should be returned + * using @a rtems_regulator_release_buffer() or used to send another message. + * + * The @a buffer is of the maximum_message_size specified in the attributes + * passed in to @a rtems_regulator_create(). + * + * @param[in] regulator is the regulator instance to operate upon + * @param[out] buffer will point to the allocated buffer + * + * @return an RTEMS status code indicating success or failure. + * + * @note This function does not perform dynamic allocation. It obtains a + * buffer from the pool allocated during @a rtems_regulator_create(). + * + * @note Any attempt to write outside the buffer area is undefined. + */ +rtems_status_code rtems_regulator_obtain_buffer( + rtems_regulator_instance *regulator, + void **buffer +); + +/** + * @ingroup RegulatorAPI + * + * @brief Release Previously Obtained Regulator Buffer + * + * This function is used to release a buffer to the regulator's pool. It is + * assumed that the @a buffer returned will not be used by the application + * anymore. The @a buffer must have previously been allocated by + * @a rtems_regulator_obtain_buffer() and NOT passed to + * @a rtems_regulator_send(). + * + * If a subsequent @a rtems_regulator_send() using this @a buffer is + * successful, the @a buffer will eventually be processed by the delivery + * thread and released. + * + * @param[in] regulator is the regulator instance to operate upon + * @param[out] buffer will point to the buffer to release + * + * @return an RTEMS status code indicating success or failure. + * + * @note This function does not perform dynamic deallocation. It releases a + * buffer to the pool allocated during @a rtems_regulator_create(). + */ +rtems_status_code rtems_regulator_release_buffer( + rtems_regulator_instance *regulator, + void *buffer +); + +/** + * @ingroup RegulatorAPI + * + * @brief Send to regulator instance + * + * This function is used by the producer to send a @a message to the + * @a regulator for later delivery by the Delivery thread. The message is + * contained in the memory pointed to by @a message and is @a length + * bytes in length. + * + * It is required that the @a message buffer was obtained via + * @a rtems_regulator_obtain_buffer(). + * + * It is assumed that the @a message buffer has been filled in with + * application content to deliver. + * + * If the @a rtems_regulator_send() is successful, the buffer is enqueued + * inside the regulator instance for subsequent delivery. After the + * @a message is delivered, it may be released by either delivery + * function or the application code depending on the implementation. + * + * The status @a RTEMS_TOO_MANY is returned if the regulator's + * internal queue is full. This indicates that the configured + * maximum number of messages was insufficient. It is the + * responsibility of the caller to decide whether to hold messages, + * drop them, or print a message that the maximum number of messages + * should be increased. + * + * If @a rtems_regulator_send() is unsuccessful, it is the application's + * responsibility to release the buffer. If it is successfully sent, + * then it becomes the responsibility of the delivery function to + * release it. + * + * @param[in] regulator is the regulator instance to operate upon + * @param[out] message points to the message to deliver + * @param[out] length is the size of the message in bytes + * + * @return an RTEMS status code indicating success or failure. + * + */ +rtems_status_code rtems_regulator_send( + rtems_regulator_instance *regulator, + void *message, + size_t length +); + +/** + * @ingroup RegulatorAPI + * + * @brief Obtain statistics for regulator instance + * + * This function is used by the application to obtain statistics + * information about the regulator instance. + * + * If the @a obtained and @a released fields in the returned + * @a statistics structure are equal, then there are no buffers + * outstanding from this regulator instance. + * + * @param[in] regulator is the regulator instance to operate upon + * @param[inout] statistics points to the statistics structure to fill in + * + * @return an RTEMS status code indicating success or failure. + * + */ +rtems_status_code rtems_regulator_get_statistics( + rtems_regulator_instance *regulator, + rtems_regulator_statistics *statistics +); + +#endif /* REGULATOR_H */ |