Camera API2.0 HAL

在上一篇文章对Camera API2.0的框架进行了简单的介绍，其中Camera HAL屏蔽了底层的实现细节，并且为上层提供了相应的接口，具体的HAL的原理，个人觉得老罗的文章Android硬件抽象层（HAL）概要介绍和学习计划分析的很详细，这里不做分析，本文将只分析Camera HAL的初始化等相关流程。
以下是Camera2的相关文章目录：
android6.0源码分析之Camera API2.0简介
android6.0源码分析之Camera2 HAL分析
android6.0源码分析之Camera API2.0下的初始化流程分析
android6.0源码分析之Camera API2.0下的Preview(预览)流程分析
android6.0源码分析之Camera API2.0下的Capture流程分析
android6.0源码分析之Camera API2.0下的video流程分析
Camera API2.0的应用

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1、Camera HAL的初始化

Camera HAL的初始加载是在Native的CameraService初始化流程中的，而CameraService初始化是在Main_mediaServer.cpp的main方法开始的：

//Main_mediaServer.cppint main(int argc __unused, char** argv){    …    sp<ProcessState> proc(ProcessState::self());    //获取ServieManager    sp<IServiceManager> sm = defaultServiceManager();    ALOGI("ServiceManager: %p", sm.get());    AudioFlinger::instantiate();    //初始化media服务    MediaPlayerService::instantiate();    //初始化资源管理服务    ResourceManagerService::instantiate();    //初始化Camera服务    CameraService::instantiate();    //初始化音频服务    AudioPolicyService::instantiate();    SoundTriggerHwService::instantiate();    //初始化Radio服务    RadioService::instantiate();    registerExtensions();    //开始线程池    ProcessState::self()->startThreadPool();    IPCThreadState::self()->joinThreadPool();}
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其中，CameraService继承自BinderService，instantiate也是在BinderService中定义的，此方法就是调用publish方法，所以来看publish方法：

// BinderService.hstatic status_t publish(bool allowIsolated = false) {    sp<IServiceManager> sm(defaultServiceManager());    //将服务添加到ServiceManager    return sm->addService(String16(SERVICE::getServiceName()),new SERVICE(), allowIsolated);}
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这里，将会把CameraService服务加入到ServiceManager进行管理。
而在前面的文章android6.0源码分析之Camera API2.0简介中，需要通过Java层的IPC Binder来获取此CameraService对象，在此过程中会初始CameraService的sp类型的对象，而对于sp，此处不做过多的分析，具体的可以查看深入理解Android卷Ⅰ中的第五章中的相关内容。此处，在CameraService的构造时，会调用CameraService的onFirstRef方法：

//CameraService.cppvoid CameraService::onFirstRef(){    BnCameraService::onFirstRef();    ...    camera_module_t *rawModule;    //根据CAMERA_HARDWARE_MODULE_ID(字符串camera)来获取camera_module_t对象    int err = hw_get_module(CAMERA_HARDWARE_MODULE_ID,            (const hw_module_t **)&rawModule);    //创建CameraModule对象    mModule = new CameraModule(rawModule);    //模块初始化    err = mModule->init();    ...    //通过Module获取Camera的数量    mNumberOfCameras = mModule->getNumberOfCameras();    mNumberOfNormalCameras = mNumberOfCameras;    //初始化闪光灯    mFlashlight = new CameraFlashlight(*mModule, *this);    status_t res = mFlashlight->findFlashUnits();    int latestStrangeCameraId = INT_MAX;    for (int i = 0; i < mNumberOfCameras; i++) {        //初始化CameraID        String8 cameraId = String8::format("%d", i);        struct camera_info info;        bool haveInfo = true;        //获取Camera信息        status_t rc = mModule->getCameraInfo(i, &info);        ...        //如果Module版本高于2.4，找出冲突的设备参数        if (mModule->getModuleApiVersion() >= CAMERA_MODULE_API_VERSION_2_4 && haveInfo) {            cost = info.resource_cost;            conflicting_devices = info.conflicting_devices;            conflicting_devices_length = info.conflicting_devices_length;        }        //将冲突设备加入冲突set集中        std::set<String8> conflicting;        for (size_t i = 0; i < conflicting_devices_length; i++) {            conflicting.emplace(String8(conflicting_devices[i]));        }        ...    }    //如果Module的API大于2.1，则设置回调    if (mModule->getModuleApiVersion() >= CAMERA_MODULE_API_VERSION_2_1) {        mModule->setCallbacks(this);    }    //若大于2.2，则设置供应商的Tag    if (mModule->getModuleApiVersion() >= CAMERA_MODULE_API_VERSION_2_2) {        setUpVendorTags();    }    //将此服务注册到CameraDeviceFactory    CameraDeviceFactory::registerService(this);    CameraService::pingCameraServiceProxy();}
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onFirstRef方法中，首先会通过HAL框架的hw_get_module来获取CameraModule对象，然后会对其进行相应的初始化，并会进行一些参数的设置，如camera的数量，闪光灯的初始化，以及回调函数的设置等，到这里，Camera2 HAL的模块就初始化结束了，下面给出初始化时序图：

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2、Camera HAL的open流程分析

通过阅读android6.0源码发现，它提供了高通的Camera实现，并且提供了高通的Camera库，也实现了高通的Camera HAL的相应接口，对于高通的Camera，它在后台会有一个守护进程daemon，daemon是介于应用和驱动之间翻译ioctl的中间层(委托处理)。本节将以Camera中的open流程为例，来分析Camera HAL的工作过程，在应用对硬件发出open请求后，会通过Camera HAL来发起open请求，而Camera HAL的open入口在QCamera2Hal.cpp进行了定义：

//QCamera2Hal.cppcamera_module_t HAL_MODULE_INFO_SYM = {    //它里面包含模块的公共方法信息    common: camera_common,    get_number_of_cameras: qcamera::QCamera2Factory::get_number_of_cameras,    get_camera_info: qcamera::QCamera2Factory::get_camera_info,    set_callbacks: qcamera::QCamera2Factory::set_callbacks,    get_vendor_tag_ops: qcamera::QCamera3VendorTags::get_vendor_tag_ops,    open_legacy: qcamera::QCamera2Factory::open_legacy,    set_torch_mode: NULL,    init : NULL,    reserved: {0}};static hw_module_t camera_common = {    tag: HARDWARE_MODULE_TAG,    module_api_version: CAMERA_MODULE_API_VERSION_2_3,    hal_api_version: HARDWARE_HAL_API_VERSION,    id: CAMERA_HARDWARE_MODULE_ID,    name: "QCamera Module",    author: "Qualcomm Innovation Center Inc",    //它的方法数组里绑定了open接口    methods: &qcamera::QCamera2Factory::mModuleMethods,    dso: NULL,    reserved: {0}};struct hw_module_methods_t QCamera2Factory::mModuleMethods = {    //open方法的绑定    open: QCamera2Factory::camera_device_open,};
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Camera HAL层的open入口其实就是camera_device_open方法：

// QCamera2Factory.cppint QCamera2Factory::camera_device_open(const struct hw_module_t *module, const char *id,        struct hw_device_t **hw_device){    ...    return gQCamera2Factory->cameraDeviceOpen(atoi(id), hw_device);}
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它调用了cameraDeviceOpen方法，而其中的hw_device就是最后要返回给应用层的CameraDeviceImpl在Camera HAL层的对象，继续分析cameraDeviceOpen方法：

// QCamera2Factory.cppint QCamera2Factory::cameraDeviceOpen(int camera_id, struct hw_device_t **hw_device){    ...    //Camera2采用的Camera HAL版本为HAL3.0    if ( mHalDescriptors[camera_id].device_version == CAMERA_DEVICE_API_VERSION_3_0 ) {        //初始化QCamera3HardwareInterface对象，这里构造函数里将会进行configure_streams以及        //process_capture_result等的绑定        QCamera3HardwareInterface *hw = new QCamera3HardwareInterface(            mHalDescriptors[camera_id].cameraId, mCallbacks);        //通过QCamera3HardwareInterface来打开Camera        rc = hw->openCamera(hw_device);        ...    } else if (mHalDescriptors[camera_id].device_version == CAMERA_DEVICE_API_VERSION_1_0) {        //HAL API为2.0        QCamera2HardwareInterface *hw = new QCamera2HardwareInterface((uint32_t)camera_id);        rc = hw->openCamera(hw_device);        ...    } else {        ...    }    return rc;}
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此方法有两个关键点：一个是QCamera3HardwareInterface对象的创建，它是用户空间与内核空间进行交互的接口；另一个是调用它的openCamera方法来打开Camera，下面将分别进行分析。

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2.1 QCamera3HardwareInterface构造函数分析

在它的构造函数里面有一个关键的初始化，即mCameraDevice.ops = &mCameraOps，它会定义Device操作的接口：

//QCamera3HWI.cppcamera3_device_ops_t QCamera3HardwareInterface::mCameraOps = {    initialize:                         QCamera3HardwareInterface::initialize,    //配置流数据的相关处理    configure_streams:                  QCamera3HardwareInterface::configure_streams,    register_stream_buffers:            NULL,    construct_default_request_settings:         QCamera3HardwareInterface::construct_default_request_settings,    //处理结果的接口    process_capture_request:                    QCamera3HardwareInterface::process_capture_request,    get_metadata_vendor_tag_ops:        NULL,    dump:                               QCamera3HardwareInterface::dump,    flush:                              QCamera3HardwareInterface::flush,    reserved:                           {0},};  
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其中，会在configure_streams中配置好流的处理handle：

//QCamera3HWI.cppint QCamera3HardwareInterface::configure_streams(const struct camera3_device *device,        camera3_stream_configuration_t *stream_list){    //获得QCamera3HardwareInterface对象    QCamera3HardwareInterface *hw =reinterpret_cast<QCamera3HardwareInterface *>(device->priv);    ...    //调用它的configureStreams进行配置    int rc = hw->configureStreams(stream_list);    ..    return rc;}
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继续追踪configureStream方法：

//QCamera3HWI.cppint QCamera3HardwareInterface::configureStreams(camera3_stream_configuration_t *streamList){    ...    //初始化Camera版本    al_version = CAM_HAL_V3;    ...    //开始配置stream    ...    //初始化相关Channel为NULL    if (mMetadataChannel) {        delete mMetadataChannel;        mMetadataChannel = NULL;    }    if (mSupportChannel) {        delete mSupportChannel;        mSupportChannel = NULL;    }    if (mAnalysisChannel) {        delete mAnalysisChannel;        mAnalysisChannel = NULL;    }    //创建Metadata Channel，并对其进行初始化    mMetadataChannel = new QCamera3MetadataChannel(mCameraHandle->camera_handle,        mCameraHandle->ops, captureResultCb,&gCamCapability[mCameraId]->padding_info,         CAM_QCOM_FEATURE_NONE, this);    ...    //初始化    rc = mMetadataChannel->initialize(IS_TYPE_NONE);    ...    //如果h/w support可用，则创建分析stream的Channel    if (gCamCapability[mCameraId]->hw_analysis_supported) {        mAnalysisChannel = new QCamera3SupportChannel(mCameraHandle->camera_handle,                mCameraHandle->ops,&gCamCapability[mCameraId]->padding_info,                CAM_QCOM_FEATURE_PP_SUPERSET_HAL3,CAM_STREAM_TYPE_ANALYSIS,                &gCamCapability[mCameraId]->analysis_recommended_res,this);        ...    }    bool isRawStreamRequested = false;    //清空stream配置信息    memset(&mStreamConfigInfo, 0, sizeof(cam_stream_size_info_t));    //为requested stream分配相关的channel对象    for (size_t i = 0; i < streamList->num_streams; i++) {        camera3_stream_t *newStream = streamList->streams[i];        uint32_t stream_usage = newStream->usage;        mStreamConfigInfo.stream_sizes[mStreamConfigInfo.num_streams].width = (int32_t)newStream-                >width;        mStreamConfigInfo.stream_sizes[mStreamConfigInfo.num_streams].height = (int32_t)newStream-                >height;        if ((newStream->stream_type == CAMERA3_STREAM_BIDIRECTIONAL||newStream->usage &                 GRALLOC_USAGE_HW_CAMERA_ZSL) &&newStream->format ==                 HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED && jpegStream){            mStreamConfigInfo.type[mStreamConfigInfo.num_streams] = CAM_STREAM_TYPE_SNAPSHOT;            mStreamConfigInfo.postprocess_mask[mStreamConfigInfo.num_streams] =                 CAM_QCOM_FEATURE_NONE;        } else if(newStream->stream_type == CAMERA3_STREAM_INPUT) {        } else {            switch (newStream->format) {                //为非zsl streams查找他们的format                ...            }        }        if (newStream->priv == NULL) {            //为新的stream构造Channel            switch (newStream->stream_type) {//分类型构造            case CAMERA3_STREAM_INPUT:                newStream->usage |= GRALLOC_USAGE_HW_CAMERA_READ;                newStream->usage |= GRALLOC_USAGE_HW_CAMERA_WRITE;//WR for inplace algo's                break;            case CAMERA3_STREAM_BIDIRECTIONAL:                ...                break;            case CAMERA3_STREAM_OUTPUT:                ...                break;            default:                break;            }            //根据前面的得到的stream的参数类型以及format分别对各类型的channel进行构造            if (newStream->stream_type == CAMERA3_STREAM_OUTPUT ||                    newStream->stream_type == CAMERA3_STREAM_BIDIRECTIONAL) {                QCamera3Channel *channel = NULL;                switch (newStream->format) {                case HAL_PIXEL_FORMAT_IMPLEMENTATION_DEFINED:                    /* use higher number of buffers for HFR mode */                    ...                    //创建Regular Channel                    channel = new QCamera3RegularChannel(mCameraHandle->camera_handle,                        mCameraHandle->ops, captureResultCb,&gCamCapability[mCameraId]-                        >padding_info,this,newStream,(cam_stream_type_t)mStreamConfigInfo.type[                        mStreamConfigInfo.num_streams],mStreamConfigInfo.postprocess_mask[                        mStreamConfigInfo.num_streams],mMetadataChannel,numBuffers);                    ...                    newStream->max_buffers = channel->getNumBuffers();                    newStream->priv = channel;                    break;                case HAL_PIXEL_FORMAT_YCbCr_420_888:                    //创建YWV Channel                    ...                    break;                case HAL_PIXEL_FORMAT_RAW_OPAQUE:                case HAL_PIXEL_FORMAT_RAW16:                case HAL_PIXEL_FORMAT_RAW10:                    //创建Raw Channel                    ...                    break;                case HAL_PIXEL_FORMAT_BLOB:                    //创建QCamera3PicChannel                    ...                    break;                default:                    break;                }            } else if (newStream->stream_type == CAMERA3_STREAM_INPUT) {                newStream->max_buffers = MAX_INFLIGHT_REPROCESS_REQUESTS;            } else {            }            for (List<stream_info_t*>::iterator it=mStreamInfo.begin();it != mStreamInfo.end();                     it++) {                if ((*it)->stream == newStream) {                    (*it)->channel = (QCamera3Channel*) newStream->priv;                    break;                }            }        } else {        }        if (newStream->stream_type != CAMERA3_STREAM_INPUT)            mStreamConfigInfo.num_streams++;        }    }    if (isZsl) {        if (mPictureChannel) {           mPictureChannel->overrideYuvSize(zslStream->width, zslStream->height);        }    } else if (mPictureChannel && m_bIs4KVideo) {        mPictureChannel->overrideYuvSize(videoWidth, videoHeight);    }    //RAW DUMP channel    if (mEnableRawDump && isRawStreamRequested == false){        cam_dimension_t rawDumpSize;        rawDumpSize = getMaxRawSize(mCameraId);        mRawDumpChannel = new QCamera3RawDumpChannel(mCameraHandle->camera_handle,            mCameraHandle->ops,rawDumpSize,&gCamCapability[mCameraId]->padding_info,            this, CAM_QCOM_FEATURE_NONE);        ...    }    //进行相关Channel的配置    ...    /* Initialize mPendingRequestInfo and mPendnigBuffersMap */    for (List<PendingRequestInfo>::iterator i = mPendingRequestsList.begin();                i != mPendingRequestsList.end(); i++) {        clearInputBuffer(i->input_buffer);        i = mPendingRequestsList.erase(i);    }    mPendingFrameDropList.clear();    // Initialize/Reset the pending buffers list    mPendingBuffersMap.num_buffers = 0;    mPendingBuffersMap.mPendingBufferList.clear();    mPendingReprocessResultList.clear();    return rc;}
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此方法内容比较多，只抽取其中核心的代码进行说明，它首先会根据HAL的版本来对stream进行相应的配置初始化，然后再根据stream类型对stream_list的stream创建相应的Channel，主要有QCamera3MetadataChannel，QCamera3SupportChannel等，然后再进行相应的配置，其中QCamera3MetadataChannel在后面的处理capture request的时候会用到，这里就不做分析，而Camerametadata则是Java层和CameraService之间传递的元数据，见android6.0源码分析之Camera API2.0简介中的Camera2架构图，至此，QCamera3HardwareInterface构造结束，与本文相关的就是配置了mCameraDevice.ops。

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2.2 openCamera分析

本节主要分析Module是如何打开Camera的，openCamera的代码如下：

//QCamera3HWI.cppint QCamera3HardwareInterface::openCamera(struct hw_device_t **hw_device){    int rc = 0;    if (mCameraOpened) {//如果Camera已经被打开，则此次打开的设备为NULL，并且打开结果为PERMISSION_DENIED        *hw_device = NULL;        return PERMISSION_DENIED;    }    //调用openCamera方法来打开    rc = openCamera();    //打开结果处理    if (rc == 0) {        //获取打开成功的hw_device_t对象        *hw_device = &mCameraDevice.common;    } else        *hw_device = NULL;    }    return rc;}
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它调用了openCamera()方法来打开Camera:

//  QCamera3HWI.cppint QCamera3HardwareInterface::openCamera(){    ...    //打开camera，获取mCameraHandle    mCameraHandle = camera_open((uint8_t)mCameraId);    ...    mCameraOpened = true;    //注册mm-camera-interface里的事件处理,其中camEctHandle为事件处理Handle    rc = mCameraHandle->ops->register_event_notify(mCameraHandle->camera_handle,camEvtHandle            ,(void *)this);    return NO_ERROR;}
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它调用camera_open方法来打开Camera，并且向CameraHandle注册了Camera 时间处理的Handle–camEvtHandle，首先分析camera_open方法，这里就将进入高通的Camera的实现了，而Mm_camera_interface.c是高通提供的相关操作的接口，接下来分析高通Camera的camera_open方法：

//Mm_camera_interface.cmm_camera_vtbl_t * camera_open(uint8_t camera_idx){    int32_t rc = 0;    mm_camera_obj_t* cam_obj = NULL;    /* opened already 如果已经打开*/    if(NULL != g_cam_ctrl.cam_obj[camera_idx]) {        /* Add reference */        g_cam_ctrl.cam_obj[camera_idx]->ref_count++;        pthread_mutex_unlock(&g_intf_lock);        return &g_cam_ctrl.cam_obj[camera_idx]->vtbl;    }    cam_obj = (mm_camera_obj_t *)malloc(sizeof(mm_camera_obj_t));    ...    /* initialize camera obj */    memset(cam_obj, 0, sizeof(mm_camera_obj_t));    cam_obj->ctrl_fd = -1;    cam_obj->ds_fd = -1;    cam_obj->ref_count++;    cam_obj->my_hdl = mm_camera_util_generate_handler(camera_idx);    cam_obj->vtbl.camera_handle = cam_obj->my_hdl; /* set handler */    //mm_camera_ops里绑定了相关的操作接口    cam_obj->vtbl.ops = &mm_camera_ops;    pthread_mutex_init(&cam_obj->cam_lock, NULL);    pthread_mutex_lock(&cam_obj->cam_lock);    pthread_mutex_unlock(&g_intf_lock);    //调用mm_camera_open方法来打开camera    rc = mm_camera_open(cam_obj);    pthread_mutex_lock(&g_intf_lock);    ...    //结果处理，并返回    ...}
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由代码可知，这里将会初始化一个mm_camera_obj_t对象，其中，ds_fd为socket fd，而mm_camera_ops则绑定了相关的接口，最后调用mm_camera_open来打开Camera，首先来看看mm_camera_ops绑定了哪些方法：

//Mm_camera_interface.cstatic mm_camera_ops_t mm_camera_ops = {    .query_capability = mm_camera_intf_query_capability,    //注册事件通知的方法    .register_event_notify = mm_camera_intf_register_event_notify,    .close_camera = mm_camera_intf_close,    .set_parms = mm_camera_intf_set_parms,    .get_parms = mm_camera_intf_get_parms,    .do_auto_focus = mm_camera_intf_do_auto_focus,    .cancel_auto_focus = mm_camera_intf_cancel_auto_focus,    .prepare_snapshot = mm_camera_intf_prepare_snapshot,    .start_zsl_snapshot = mm_camera_intf_start_zsl_snapshot,    .stop_zsl_snapshot = mm_camera_intf_stop_zsl_snapshot,    .map_buf = mm_camera_intf_map_buf,    .unmap_buf = mm_camera_intf_unmap_buf,    .add_channel = mm_camera_intf_add_channel,    .delete_channel = mm_camera_intf_del_channel,    .get_bundle_info = mm_camera_intf_get_bundle_info,    .add_stream = mm_camera_intf_add_stream,    .link_stream = mm_camera_intf_link_stream,    .delete_stream = mm_camera_intf_del_stream,    //配置stream的方法    .config_stream = mm_camera_intf_config_stream,    .qbuf = mm_camera_intf_qbuf,    .get_queued_buf_count = mm_camera_intf_get_queued_buf_count,    .map_stream_buf = mm_camera_intf_map_stream_buf,    .unmap_stream_buf = mm_camera_intf_unmap_stream_buf,    .set_stream_parms = mm_camera_intf_set_stream_parms,    .get_stream_parms = mm_camera_intf_get_stream_parms,    .start_channel = mm_camera_intf_start_channel,    .stop_channel = mm_camera_intf_stop_channel,    .request_super_buf = mm_camera_intf_request_super_buf,    .cancel_super_buf_request = mm_camera_intf_cancel_super_buf_request,    .flush_super_buf_queue = mm_camera_intf_flush_super_buf_queue,    .configure_notify_mode = mm_camera_intf_configure_notify_mode,    //处理capture的方法    .process_advanced_capture = mm_camera_intf_process_advanced_capture};
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接着分析mm_camera_open方法：

//Mm_camera.cint32_t mm_camera_open(mm_camera_obj_t *my_obj){    ...    do{        n_try--;        //根据设备名字，打开相应的设备驱动fd        my_obj->ctrl_fd = open(dev_name, O_RDWR | O_NONBLOCK);        if((my_obj->ctrl_fd >= 0) || (errno != EIO) || (n_try <= 0 )) {            break;        }        usleep(sleep_msec * 1000U);    }while (n_try > 0);    ...    //打开domain socket    n_try = MM_CAMERA_DEV_OPEN_TRIES;    do {        n_try--;        my_obj->ds_fd = mm_camera_socket_create(cam_idx, MM_CAMERA_SOCK_TYPE_UDP);        usleep(sleep_msec * 1000U);    } while (n_try > 0);    ...    //初始化锁    pthread_mutex_init(&my_obj->msg_lock, NULL);    pthread_mutex_init(&my_obj->cb_lock, NULL);    pthread_mutex_init(&my_obj->evt_lock, NULL);    pthread_cond_init(&my_obj->evt_cond, NULL);    //开启线程，它的线程体在mm_camera_dispatch_app_event方法中    mm_camera_cmd_thread_launch(&my_obj->evt_thread,                                mm_camera_dispatch_app_event,                                (void *)my_obj);    mm_camera_poll_thread_launch(&my_obj->evt_poll_thread,                                 MM_CAMERA_POLL_TYPE_EVT);    mm_camera_evt_sub(my_obj, TRUE);    return rc;    ...}
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由代码可知，它会打开Camera的设备文件，然后开启dispatch_app_event线程，线程方法体mm_camera_dispatch_app_event方法代码如下：

//Mm_camera.cstatic void mm_camera_dispatch_app_event(mm_camera_cmdcb_t *cmd_cb,void* user_data){    mm_camera_cmd_thread_name("mm_cam_event");    int i;    mm_camera_event_t *event = &cmd_cb->u.evt;    mm_camera_obj_t * my_obj = (mm_camera_obj_t *)user_data;    if (NULL != my_obj) {        pthread_mutex_lock(&my_obj->cb_lock);        for(i = 0; i < MM_CAMERA_EVT_ENTRY_MAX; i++) {            if(my_obj->evt.evt[i].evt_cb) {                //调用camEvtHandle方法                my_obj->evt.evt[i].evt_cb(                    my_obj->my_hdl,                    event,                    my_obj->evt.evt[i].user_data);            }        }        pthread_mutex_unlock(&my_obj->cb_lock);    }}
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最后会调用mm-camera-interface中注册好的事件处理evt_cb，它就是在前面注册好的camEvtHandle：

//QCamera3HWI.cppvoid QCamera3HardwareInterface::camEvtHandle(uint32_t /*camera_handle*/,mm_camera_event_t *evt,        void *user_data){    //获取QCamera3HardwareInterface接口指针    QCamera3HardwareInterface *obj = (QCamera3HardwareInterface *)user_data;    if (obj && evt) {        switch(evt->server_event_type) {            case CAM_EVENT_TYPE_DAEMON_DIED:                camera3_notify_msg_t notify_msg;                memset(&notify_msg, 0, sizeof(camera3_notify_msg_t));                notify_msg.type = CAMERA3_MSG_ERROR;                notify_msg.message.error.error_code = CAMERA3_MSG_ERROR_DEVICE;                notify_msg.message.error.error_stream = NULL;                notify_msg.message.error.frame_number = 0;                obj->mCallbackOps->notify(obj->mCallbackOps, &notify_msg);                break;            case CAM_EVENT_TYPE_DAEMON_PULL_REQ:                pthread_mutex_lock(&obj->mMutex);                obj->mWokenUpByDaemon = true;                //开启process_capture_request                obj->unblockRequestIfNecessary();                pthread_mutex_unlock(&obj->mMutex);                break;              default:                break;        }    } else {    }}
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由代码可知，它会调用QCamera3HardwareInterface的unblockRequestIfNecessary来发起结果处理请求：

//QCamera3HWI.cppvoid QCamera3HardwareInterface::unblockRequestIfNecessary(){   // Unblock process_capture_request   //开启process_capture_request   pthread_cond_signal(&mRequestCond);}
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在初始化QCamera3HardwareInterface对象的时候，就绑定了处理Metadata的回调captureResultCb方法：它主要是对数据源进行相应的处理，而具体的capture请求的结果处理还是由process_capture_request来进行处理的，而这里会调用方法unblockRequestIfNecessary来触发process_capture_request方法执行，而在Camera框架中，发起请求时会启动一个RequestThread线程，在它的threadLoop方法中，会不停的调用process_capture_request方法来进行请求的处理，而它最后会回调Camera3Device中的processCaptureResult方法来进行结果处理：

//Camera3Device.cppvoid Camera3Device::processCaptureResult(const camera3_capture_result *result) {    ...    {        ...        if (mUsePartialResult && result->result != NULL) {            if (mDeviceVersion >= CAMERA_DEVICE_API_VERSION_3_2) {                ...                if (isPartialResult) {                    request.partialResult.collectedResult.append(result->result);                }            } else {                camera_metadata_ro_entry_t partialResultEntry;                res = find_camera_metadata_ro_entry(result->result,                        ANDROID_QUIRKS_PARTIAL_RESULT, &partialResultEntry);                if (res != NAME_NOT_FOUND &&partialResultEntry.count > 0 &&                        partialResultEntry.data.u8[0] ==ANDROID_QUIRKS_PARTIAL_RESULT_PARTIAL) {                    isPartialResult = true;                    request.partialResult.collectedResult.append(                        result->result);                    request.partialResult.collectedResult.erase(                        ANDROID_QUIRKS_PARTIAL_RESULT);                }            }            if (isPartialResult) {                // Fire off a 3A-only result if possible                if (!request.partialResult.haveSent3A) {                    //处理3A结果                    request.partialResult.haveSent3A =processPartial3AResult(frameNumber,                        request.partialResult.collectedResult,request.resultExtras);                }            }        }        ...        //查找camera元数据入口        camera_metadata_ro_entry_t entry;        res = find_camera_metadata_ro_entry(result->result,                ANDROID_SENSOR_TIMESTAMP, &entry);        if (shutterTimestamp == 0) {            request.pendingOutputBuffers.appendArray(result->output_buffers,                result->num_output_buffers);        } else {            重要的分析//返回处理的outputbuffer            returnOutputBuffers(result->output_buffers,                result->num_output_buffers, shutterTimestamp);        }        if (result->result != NULL && !isPartialResult) {            if (shutterTimestamp == 0) {                request.pendingMetadata = result->result;                request.partialResult.collectedResult = collectedPartialResult;            } else {                CameraMetadata metadata;                metadata = result->result;                //发送Capture结构，即调用通知回调                sendCaptureResult(metadata, request.resultExtras,                    collectedPartialResult, frameNumber, hasInputBufferInRequest,                    request.aeTriggerCancelOverride);            }        }        removeInFlightRequestIfReadyLocked(idx);    } // scope for mInFlightLock    if (result->input_buffer != NULL) {        if (hasInputBufferInRequest) {            Camera3Stream *stream =                Camera3Stream::cast(result->input_buffer->stream);            重要的分析//返回处理的inputbuffer            res = stream->returnInputBuffer(*(result->input_buffer));        } else {}    }}
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分析returnOutputBuffers方法，inputbuffer的runturnInputBuffer方法流程类似：

//Camera3Device.cppvoid Camera3Device::returnOutputBuffers(const camera3_stream_buffer_t *outputBuffers, size_t         numBuffers, nsecs_t timestamp) {    for (size_t i = 0; i < numBuffers; i++)    {        Camera3Stream *stream = Camera3Stream::cast(outputBuffers[i].stream);        status_t res = stream->returnBuffer(outputBuffers[i], timestamp);        ...    }}
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方法里调用了returnBuffer方法：

//Camera3Stream.cppstatus_t Camera3Stream::returnBuffer(const camera3_stream_buffer &buffer,nsecs_t timestamp) {    //返回buffer    status_t res = returnBufferLocked(buffer, timestamp);    if (res == OK) {        fireBufferListenersLocked(buffer, /*acquired*/false, /*output*/true);        mOutputBufferReturnedSignal.signal();    }    return res;}
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再继续看returnBufferLocked,它调用了returnAnyBufferLocked方法，而returnAnyBufferLocked方法又调用了returnBufferCheckedLocked方法，现在分析returnBufferCheckedLocked：

// Camera3OutputStream.cppstatus_t Camera3OutputStream::returnBufferCheckedLocked(const camera3_stream_buffer &buffer,            nsecs_t timestamp,bool output,/*out*/sp<Fence> *releaseFenceOut) {    ...    // Fence management - always honor release fence from HAL    sp<Fence> releaseFence = new Fence(buffer.release_fence);    int anwReleaseFence = releaseFence->dup();    if (buffer.status == CAMERA3_BUFFER_STATUS_ERROR) {        // Cancel buffer        res = currentConsumer->cancelBuffer(currentConsumer.get(),                container_of(buffer.buffer, ANativeWindowBuffer, handle),                anwReleaseFence);        ...    } else {        ...        res = currentConsumer->queueBuffer(currentConsumer.get(),                container_of(buffer.buffer, ANativeWindowBuffer, handle),                anwReleaseFence);        ...    }    ...    return res;}
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由代码可知，如果Buffer没有出现状态错误，它会调用currentConsumer的queueBuffer方法，而具体的Consumer则是在应用层初始化Camera时进行绑定的，典型的Consumer有SurfaceTexture，ImageReader等，而在Native层中，它会调用BufferQueueProducer的queueBuffer方法：

// BufferQueueProducer.cppstatus_t BufferQueueProducer::queueBuffer(int slot,        const QueueBufferInput &input, QueueBufferOutput *output) {    ...    //初始化Frame可用的监听器    sp<IConsumerListener> frameAvailableListener;    sp<IConsumerListener> frameReplacedListener;    int callbackTicket = 0;    BufferItem item;    { // Autolock scope        ...        const sp<GraphicBuffer>& graphicBuffer(mSlots[slot].mGraphicBuffer);        Rect bufferRect(graphicBuffer->getWidth(), graphicBuffer->getHeight());        Rect croppedRect;        crop.intersect(bufferRect, &croppedRect);        ...        //如果队列为空        if (mCore->mQueue.empty()) {            mCore->mQueue.push_back(item);            frameAvailableListener = mCore->mConsumerListener;        } else {            //否则，不为空，对Buffer进行处理，并获取FrameAvailableListener监听            BufferQueueCore::Fifo::iterator front(mCore->mQueue.begin());            if (front->mIsDroppable) {                if (mCore->stillTracking(front)) {                    mSlots[front->mSlot].mBufferState = BufferSlot::FREE;                    mCore->mFreeBuffers.push_front(front->mSlot);                }                *front = item;                frameReplacedListener = mCore->mConsumerListener;            } else {                mCore->mQueue.push_back(item);                frameAvailableListener = mCore->mConsumerListener;            }        }        mCore->mBufferHasBeenQueued = true;        mCore->mDequeueCondition.broadcast();        output->inflate(mCore->mDefaultWidth, mCore->mDefaultHeight,mCore->mTransformHint,                static_cast<uint32_t>(mCore->mQueue.size()));        // Take a ticket for the callback functions        callbackTicket = mNextCallbackTicket++;        mCore->validateConsistencyLocked();    } // Autolock scope    ...    {        ...        if (frameAvailableListener != NULL) {            //回调SurfaceTexture中定义好的监听IConsumerListener的onFrameAvailable方法来对数据进行处理            frameAvailableListener->onFrameAvailable(item);        } else if (frameReplacedListener != NULL) {            frameReplacedListener->onFrameReplaced(item);        }        ++mCurrentCallbackTicket;        mCallbackCondition.broadcast();    }    return NO_ERROR;}
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由代码可知，它最后会调用Consumer的回调FrameAvailableListener的onFrameAvailable方法，到这里，就比较清晰为什么我们在写Camera应用，为其初始化Surface时，我们需要重写FrameAvailableListener了，因为在此方法里面，会进行结果的处理，至此，Camera HAL的Open流程就分析结束了。下面给出流程的时序图：

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