android8 Camera2 从 CameraService 到 HAL Service

上回讲到，在 CameraService::makeClient 中，实例化了一个 CameraDeviceClient。现在我们就从它的构造函数开始，继续探索打开相机的流程。

这一部分主要活动在 Runtime 层，这里分成 CameraService 与 HAL Service 两侧来分析。

接前一章节， CameraService 在创建 CameraDeviceClient 之后，会调用它的初始化函数

err = client->initialize(mCameraProviderManager);

​
status_t CameraDeviceClient::initialize(sp<CameraProviderManager> manager) {
    return initializeImpl(manager);
} // 即是对外提供调用的初始化函数接口 initialize

//初始化的具体实现函数，模板 TProviderPtr 在此处即是 CameraProviderManager 类。

template<typename TProviderPtr>
status_t CameraDeviceClient::initializeImpl(TProviderPtr providerPtr) {
    ATRACE_CALL();
    status_t res;

// 首先将父类初始化，注意此处传入了 CameraProviderManager

//CameraService::enumerateProviders() 方法中会初始化

//mCameraProviderManager = new CameraProviderManager();

    res = Camera2ClientBase::initialize(providerPtr);
    if (res != OK) {
        return res;
    }

  //这里是关于 FrameProcessor 的创建与初始化配置等等，这个东西可能是用于处理上传的每帧数据的，

//暂时不深入分析

    String8 threadName;
    mFrameProcessor = new FrameProcessorBase(mDevice);
    threadName = String8::format("CDU-%s-FrameProc", mCameraIdStr.string());
    mFrameProcessor->run(threadName.string());

    mFrameProcessor->registerListener(FRAME_PROCESSOR_LISTENER_MIN_ID,
                                      FRAME_PROCESSOR_LISTENER_MAX_ID,
                                      /*listener*/this,
                                      /*sendPartials*/true);

    return OK;
}

​

接前一篇文章，最后部分

*client = new CameraDeviceClient(cameraService, tmp, packageName, cameraId,
                        facing, clientPid, clientUid, servicePid);

来到文件CameraDeviceClient.cpp

CameraDeviceClient::CameraDeviceClient(const sp<CameraService>& cameraService,
        const sp<hardware::camera2::ICameraDeviceCallbacks>& remoteCallback,
        const String16& clientPackageName,
        const String8& cameraId,
        int cameraFacing,
        int clientPid,
        uid_t clientUid,
        int servicePid) :
    Camera2ClientBase(cameraService, remoteCallback, clientPackageName,
                cameraId, cameraFacing, clientPid, clientUid, servicePid),
    mInputStream(),
    mStreamingRequestId(REQUEST_ID_NONE),
    mRequestIdCounter(0) {

    ATRACE_CALL();
    ALOGI("CameraDeviceClient %s: Opened", cameraId.string());
}

注意第9行代码调用

Camera2ClientBase(cameraService, remoteCallback, clientPackageName,
                cameraId, cameraFacing, clientPid, clientUid, servicePid)

往下看

template <typename TClientBase>
Camera2ClientBase<TClientBase>::Camera2ClientBase(
        const sp<CameraService>& cameraService,
        const sp<TCamCallbacks>& remoteCallback,
        const String16& clientPackageName,
        const String8& cameraId,
        int cameraFacing,
        int clientPid,
        uid_t clientUid,
        int servicePid):
        TClientBase(cameraService, remoteCallback, clientPackageName,
                cameraId, cameraFacing, clientPid, clientUid, servicePid),
        mSharedCameraCallbacks(remoteCallback),
        mDeviceVersion(cameraService->getDeviceVersion(TClientBase::mCameraIdStr)),
        mDeviceActive(false)
{
    ALOGI("Camera %s: Opened. Client: %s (PID %d, UID %d)", cameraId.string(),
            String8(clientPackageName).string(), clientPid, clientUid);

    mInitialClientPid = clientPid;
    mDevice = new Camera3Device(cameraId);
    LOG_ALWAYS_FATAL_IF(mDevice == 0, "Device should never be NULL here.");
}

回头再看Camera2ClientBase::initialize(providerPtr);

template <typename TClientBase>
status_t Camera2ClientBase<TClientBase>::initialize(sp<CameraProviderManager> manager) {
    return initializeImpl(manager);
}

template <typename TClientBase>
template <typename TProviderPtr>
status_t Camera2ClientBase<TClientBase>::initializeImpl(TProviderPtr providerPtr) {
    ATRACE_CALL();
    ALOGV("%s: Initializing client for camera %s", __FUNCTION__,
          TClientBase::mCameraIdStr.string());
    status_t res;

    // Verify ops permissions
    res = TClientBase::startCameraOps();
    if (res != OK) {
        return res;
    }

    if (mDevice == NULL) {
        ALOGE("%s: Camera %s: No device connected",
                __FUNCTION__, TClientBase::mCameraIdStr.string());
        return NO_INIT;
    }

    res = mDevice->initialize(providerPtr);
    if (res != OK) {
        ALOGE("%s: Camera %s: unable to initialize device: %s (%d)",
                __FUNCTION__, TClientBase::mCameraIdStr.string(), strerror(-res), res);
        return res;
    }

    wp<CameraDeviceBase::NotificationListener> weakThis(this);
    res = mDevice->setNotifyCallback(weakThis);

    return OK;
}

再看mDevice = new Camera3Device(cameraId);

Camera3Device.cpp 文件

Camera3Device::Camera3Device(const String8 &id):
        mId(id),
        mOperatingMode(NO_MODE),
        mIsConstrainedHighSpeedConfiguration(false),
        mStatus(STATUS_UNINITIALIZED),
        mStatusWaiters(0),
        mUsePartialResult(false),
        mNumPartialResults(1),
        mTimestampOffset(0),
        mNextResultFrameNumber(0),
        mNextReprocessResultFrameNumber(0),
        mNextShutterFrameNumber(0),
        mNextReprocessShutterFrameNumber(0),
        mListener(NULL),
        mVendorTagId(CAMERA_METADATA_INVALID_VENDOR_ID)
{
    ATRACE_CALL();
    camera3_callback_ops::notify = &sNotify;
    camera3_callback_ops::process_capture_result = &sProcessCaptureResult;
    ALOGV("%s: Created device for camera %s", __FUNCTION__, mId.string());
}

继续往下看初始化res = mDevice->initialize(providerPtr);

status_t Camera3Device::initialize(sp<CameraProviderManager> manager) {
    ATRACE_CALL();
    Mutex::Autolock il(mInterfaceLock);
    Mutex::Autolock l(mLock);

    ALOGV("%s: Initializing HIDL device for camera %s", __FUNCTION__, mId.string());
    if (mStatus != STATUS_UNINITIALIZED) {
        CLOGE("Already initialized!");
        return INVALID_OPERATION;
    }
    if (manager == nullptr) return INVALID_OPERATION;

    sp<ICameraDeviceSession> session;
    ATRACE_BEGIN("CameraHal::openSession");
    status_t res = manager->openSession(mId.string(), this,
            /*out*/ &session);
    ATRACE_END();
    if (res != OK) {
        SET_ERR_L("Could not open camera session: %s (%d)", strerror(-res), res);
        return res;
    }

    res = manager->getCameraCharacteristics(mId.string(), &mDeviceInfo);
    if (res != OK) {
        SET_ERR_L("Could not retrive camera characteristics: %s (%d)", strerror(-res), res);
        session->close();
        return res;
    }

    std::shared_ptr<RequestMetadataQueue> queue;
    auto requestQueueRet = session->getCaptureRequestMetadataQueue(
        [&queue](const auto& descriptor) {
            queue = std::make_shared<RequestMetadataQueue>(descriptor);
            if (!queue->isValid() || queue->availableToWrite() <= 0) {