273 lines
10 KiB
C
273 lines
10 KiB
C
/*
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* Copyright (C) 2016 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef _CHRE_EVENT_H_
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#define _CHRE_EVENT_H_
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/**
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* Context Hub Runtime Environment API dealing with events and messages.
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*/
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#include <stdbool.h>
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#include <stdint.h>
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#include <stdlib.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/**
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* The CHRE implementation is required to provide the following
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* preprocessor defines via the build system.
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*
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* CHRE_MESSAGE_TO_HOST_MAX_SIZE: The maximum size, in bytes, allowed for
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* a message sent to chreSendMessageToHost(). This must be at least
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* CHRE_MESSAGE_TO_HOST_MINIMUM_MAX_SIZE.
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*/
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#ifndef CHRE_MESSAGE_TO_HOST_MAX_SIZE
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#error CHRE_MESSAGE_TO_HOST_MAX_SIZE must be defined by the Context Hub Runtime Environment implementation
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#endif
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/**
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* The minimum size, in bytes, any CHRE implementation will
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* use for CHRE_MESSAGE_TO_HOST_MAX_SIZE.
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*/
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#define CHRE_MESSAGE_TO_HOST_MINIMUM_MAX_SIZE 128
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#if CHRE_MESSAGE_TO_HOST_MAX_SIZE < CHRE_MESSAGE_TO_HOST_MINIMUM_MAX_SIZE
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#error CHRE_MESSAGE_TO_HOST_MAX_SIZE is too small.
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#endif
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/**
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* The lowest numerical value legal for a user-defined event.
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*
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* The system reserves all event values from 0 to 0x7FFF, inclusive.
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* User events may use any value in the range 0x8000 to 0xFFFF, inclusive.
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*
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* Note that the same event values might be used by different nanoapps
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* for different meanings. This is not a concern, as these values only
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* have meaning when paired with the originating nanoapp.
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*/
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#define CHRE_EVENT_FIRST_USER_VALUE UINT16_C(0x8000)
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/**
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* nanoappHandleEvent argument: struct chreMessageFromHostData
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*
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* The format of the 'message' part of this structure is left undefined,
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* and it's up to the nanoapp and host to have an established protocol
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* beforehand.
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*/
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#define CHRE_EVENT_MESSAGE_FROM_HOST UINT16_C(0x0001)
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/**
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* nanoappHandleEvent argument: 'cookie' given to chreTimerSet() method.
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*
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* Indicates that a timer has elapsed, in accordance with how chreTimerSet() was
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* invoked.
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*/
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#define CHRE_EVENT_TIMER UINT16_C(0x0002)
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/**
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* First possible value for CHRE_EVENT_SENSOR events.
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*
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* This allows us to separately define our CHRE_EVENT_SENSOR_* events in
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* chre_sensor.h, without fear of collision with other event values.
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*/
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#define CHRE_EVENT_SENSOR_FIRST_EVENT UINT16_C(0x0100)
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/**
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* Last possible value for CHRE_EVENT_SENSOR events.
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*
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* This allows us to separately define our CHRE_EVENT_SENSOR_* events in
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* chre_sensor.h, without fear of collision with other event values.
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*/
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#define CHRE_EVENT_SENSOR_LAST_EVENT UINT16_C(0x02FF)
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/**
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* First in a range of values dedicated for internal CHRE implementation usage.
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*
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* If a CHRE wishes to use events internally, any values within this range
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* are assured not to be taken by future CHRE API additions.
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*/
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#define CHRE_EVENT_INTERNAL_FIRST_EVENT UINT16_C(0x7E00)
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/**
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* Last in a range of values dedicated for internal CHRE implementation usage.
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*
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* If a CHRE wishes to use events internally, any values within this range
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* are assured not to be taken by future CHRE API additions.
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*/
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#define CHRE_EVENT_INTERNAL_LAST_EVENT UINT16_C(0x7FFF)
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/**
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* CHRE_EVENT_MESSAGE_FROM_HOST
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*/
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struct chreMessageFromHostData {
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/**
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* Message type (NOTE: not implemented correctly in the Android N release).
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*
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* In future releases, this will be a message type provided by the host.
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*/
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uint32_t reservedMessageType;
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/**
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* The size, in bytes of the following 'message'.
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*
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* This can be 0.
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*/
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uint32_t messageSize;
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/**
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* The message from the host.
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*
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* These contents are of a format that the host and nanoapp must have
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* established beforehand.
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*
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* This data is 'messageSize' bytes in length. Note that if 'messageSize'
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* is 0, this might be NULL.
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*/
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const void *message;
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};
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/**
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* Callback which frees data associated with an event.
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*
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* This callback is (optionally) provided to the chreSendEvent() method as
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* a means for freeing the event data and performing any other cleanup
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* necessary when the event is completed. When this callback is invoked,
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* 'eventData' is no longer needed and can be released.
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*
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* @param eventType The 'eventType' argument from chreSendEvent().
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* @param eventData The 'eventData' argument from chreSendEvent().
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*
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* @see chreSendEvent
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*/
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typedef void (chreEventCompleteFunction)(uint16_t eventType, void *eventData);
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/**
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* Callback which frees a message.
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*
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* This callback is (optionally) provided to the chreSendMessageToHost() method
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* as a means for freeing the message. When this callback is invoked,
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* 'message' is no longer needed and can be released. Note that this in
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* no way assures that said message did or did not make it to the host, simply
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* that this memory is no longer needed.
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*
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* @param message The 'message' argument from chreSendMessageToHost().
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* @param messageSize The 'messageSize' argument from chreSendMessageToHost().
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*
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* @see chreSendMessageToHost
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*/
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typedef void (chreMessageFreeFunction)(void *message, size_t messageSize);
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/**
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* Enqueue an event to be sent to another nanoapp.
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*
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* Note: This version of the API does not give an easy means to discover
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* another nanoapp's instance ID. For now, events will need to be sent to/from
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* the host to initially discover these IDs.
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*
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* @param eventType This is a user-defined event type, of at least the
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* value CHRE_EVENT_FIRST_USER_VALUE. It is illegal to attempt to use any
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* of the CHRE_EVENT_* values reserved for the CHRE.
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* @param eventData A pointer value that will be understood by the receiving
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* app. Note that NULL is perfectly acceptable. It also is not required
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* that this be a valid pointer, although if this nanoapp is intended to
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* work on arbitrary CHRE implementations, then the size of a
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* pointer cannot be assumed to be a certain size. Note that the caller
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* no longer owns this memory after the call.
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* @param freeCallback A pointer to a callback function. After the lifetime
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* of 'eventData' is over (either through successful delivery or the event
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* being dropped), this callback will be invoked. This argument is allowed
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* to be NULL, in which case no callback will be invoked.
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* @param targetInstanceId The ID of the instance we're delivering this event
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* to. Note that this is allowed to be our own instance.
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* @returns true if the event was enqueued, false otherwise. Note that even
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* if this method returns 'false', the 'freeCallback' will be invoked,
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* if non-NULL. Note in the 'false' case, the 'freeCallback' may be
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* invoked directly from within chreSendEvent(), so it's necessary
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* for nanoapp authors to avoid possible recursion with this.
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*
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* @see chreEventDataFreeFunction
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*/
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bool chreSendEvent(uint16_t eventType, void *eventData,
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chreEventCompleteFunction *freeCallback,
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uint32_t targetInstanceId);
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/**
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* Send a message to the host.
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*
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* This message is by definition arbitrarily defined. Since we're not
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* just a passing a pointer to memory around the system, but need to copy
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* this into various buffers to send it to the host, the CHRE
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* implementation cannot be asked to support an arbitrarily large message
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* size. As a result, we have the CHRE implementation define
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* CHRE_MESSAGE_TO_HOST_MAX_SIZE.
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*
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* CHRE_MESSAGE_TO_HOST_MAX_SIZE is not given a value by the Platform API. The
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* Platform API does define CHRE_MESSAGE_TO_HOST_MINIMUM_MAX_SIZE, and requires
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* that CHRE_MESSAGE_TO_HOST_MAX_SIZE is at least that value.
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*
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* As a result, if your message sizes are all less than
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* CHRE_MESSAGE_TO_HOST_MINIMUM_MAX_SIZE, then you have no concerns on any
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* CHRE implementation. If your message sizes are larger, you'll need to
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* come up with a strategy for splitting your message across several calls
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* to this method. As long as that strategy works for
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* CHRE_MESSAGE_TO_HOST_MINIMUM_MAX_SIZE, it will work across all CHRE
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* implementations (although on some implementations less calls to this
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* method may be necessary).
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*
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* @param message Pointer to a block of memory to send to the host.
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* NULL is acceptable only if messageSize is 0. If non-NULL, this
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* must be a legitimate pointer (that is, unlike chreSendEvent(), a small
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* integral value cannot be cast to a pointer for this). Note that the
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* caller no longer owns this memory after the call.
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* @param messageSize The size, in bytes, of the given message.
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* This cannot exceed CHRE_MESSAGE_TO_HOST_MAX_SIZE.
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* @param reservedMessageType Message type sent to the app on the host.
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* NOTE: In the N release, there is a bug in some HAL implementations
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* where this data does not make it to the app running on the host.
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* Nanoapps cannot trust this across all platforms for N, but that
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* will be fixed in O.
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* @param freeCallback A pointer to a callback function. After the lifetime
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* of 'message' is over (which does not assure that 'message' made it to
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* the host, just that the transport layer no longer needs this memory),
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* this callback will be invoked. This argument is allowed
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* to be NULL, in which case no callback will be invoked.
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* @returns true if the message was accepted for transmission, false otherwise.
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* Note that even if this method returns 'false', the 'freeCallback' will
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* be invoked, if non-NULL. Note in the 'false' case, the 'freeCallback'
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* may be invoked directly from within chreSendMessageToHost(), so it's
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* necessary for nanoapp authors to avoid possible recursion with this.
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*
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* @see chreMessageFreeFunction
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*/
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bool chreSendMessageToHost(void *message, uint32_t messageSize,
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uint32_t reservedMessageType,
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chreMessageFreeFunction *freeCallback);
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#ifdef __cplusplus
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}
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#endif
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#endif /* _CHRE_EVENT_H_ */
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