Android Camera AP到Camera Hal調用流程

1.       首先是調用framework層的Camera.java(frameworks\base\core\java\android\hardware)的takePicture方法 2.       接著會調用到JNI層的android_hardware_Camera.cpp(frameworks\base\core\jni)的android_hardware_Camera_takePicture方法，其中會通過get_native_camera獲取一個Camera對象。 3.       上述Camera對象的定義在Camera.h(frameworks\av\include\camera)，camera.h同時定義了CameraInfo。Camera對象繼承自publicBnCameraClient,DeathRecipient。Camera對象的真正實現是在Camera.cpp(frameworks\av\camera)   。BnCameraClient是作為CameraService回調而存在的。Camera對象內含有一個mCameraService變量用於保存CameraService引用。 class Camera : public BnCameraClient,public IBinder::DeathRecipient constsp<ICameraService>& Camera::getCameraService() {     Mutex::Autolock _l(mLock);     if (mCameraService.get() == 0) {         sp<IServiceManager> sm = defaultServiceManager();         sp<IBinder> binder;         do {             binder =sm->getService(String16("media.camera"));             if (binder != 0)                 break;             ALOGW("CameraService notpublished, waiting...");             usleep(500000); // 0.5 s         } while(true);         if (mDeathNotifier == NULL) {             mDeathNotifier = newDeathNotifier();         }         binder->linkToDeath(mDeathNotifier);         mCameraService =interface_cast<ICameraService>(binder);     } 4.       在ICameraClient.h和ICameraService.h文件中，ICameraClient和ICameraService都繼承自IInterface，也就是Binder通信的基礎，此外ICamera.h也繼承自IInterface class ICameraClient:public IInterface class ICameraService :public IInterface class ICamera: publicIInterface 然後發現BnCameraClient繼承自BnInterface<ICameraClient>，作為ICameraClient的服務器端存在： class BnCameraClient: publicBnInterface<ICameraClient> BnCameraService繼承自BnInterface<ICameraService>，作為ICameraService的服務器端存在： class BnCameraService: publicBnInterface<ICameraService> BnCamera繼承自BnInterface<ICamera>，作為ICamera的服務器端存在： class BnCamera: public BnInterface<ICamera> 對應的上述三個分別存在一個作為Binder客戶端的類存在，為Bp***： class BpCameraClient:public BpInterface<ICameraClient> class BpCameraService:public BpInterface<ICameraService> class BpCamera: publicBpInterface<ICamera> 上述三個的實現分別在ICameraClient.cpp、ICameraService.cpp、ICamera.cpp,在這三支文件中分別實現了三組Binder的Server端和Client端，Camera常用的方法都在ICamera中實現。 5.       Camera.cpp文件connect方法在JNI層去setupCamera的時候會調用，JNI層是在上層opencamera的時候被調用的，在camera.cpp的connect方法中獲取一個ICamera對象來完成對Camera的真正操作。 sp<Camera>Camera::connect(int cameraId) {     ALOGV("connect");     sp<Camera> c = new Camera();     const sp<ICameraService>& cs =getCameraService();     if (cs != 0) {         c->mCamera = cs->connect(c, cameraId);     }     if (c->mCamera != 0) {        c->mCamera->asBinder()->linkToDeath(c);         c->mStatus = NO_ERROR;     } else {         c.clear();     }     return c; } 6.       在CameraService.h文件中可以看到CameraService定義內部類Client，CameraClient繼承此類，在CameraService中持有對mClient對象的一個數組，這個數組也是Camera.cpp客戶端調用connect方法後需要返回的Binder引用對象  class Client : public BnCamera class CameraClient : public CameraService::Client wp<Client>         mClient[MAX_CAMERAS];     switch(deviceVersion) {       case CAMERA_DEVICE_API_VERSION_1_0:         client = new CameraClient(this,cameraClient, cameraId,                 info.facing, callingPid, getpid());         break;       case CAMERA_DEVICE_API_VERSION_2_0:         client = new Camera2Client(this,cameraClient, cameraId,                 info.facing, callingPid,getpid()); 並且Google好像有開發新的API2.0，在此處通過判斷不同的version實例化不同的CameraClient的Binder引用對象回去，目前Camera2文件夾有Burst等實現 7.       在CameraService層的CameraClient對象的定義中，持有CameraHardwareInterface對象的引用mHardware.在CameraClient的initilize方法中會創建此對象，在對象的構造方法中傳入需要打開的Camera的ID。 sp<CameraHardwareInterface>     mHardware; status_t CameraClient::initialize(camera_module_t *module) {     int callingPid = getCallingPid();     LOG1("CameraClient::initialize E (pid%d, id %d)", callingPid, mCameraId);       char camera_device_name[10];     status_t res;     snprintf(camera_device_name, sizeof(camera_device_name),"%d", mCameraId);     mHardware = new CameraHardwareInterface(camera_device_name);     res = mHardware->initialize(&module->common);     if (res != OK) {         ALOGE("%s: Camera %d: unable toinitialize device: %s (%d)",                 __FUNCTION__, mCameraId,strerror(-res), res);         mHardware.clear();         return NO_INIT;     }     mHardware->setCallbacks(notifyCallback,            dataCallback,            dataCallbackTimestamp,             (void*)mCameraId);     //Enable zoom, error, focus, and metadata messages by default     enableMsgType(CAMERA_MSG_ERROR | CAMERA_MSG_ZOOM | CAMERA_MSG_FOCUS |                  CAMERA_MSG_PREVIEW_METADATA | CAMERA_MSG_FOCUS_MOVE); //!++ #ifdef  MTK_CAMERA_BSP_SUPPORT     // Enable MTK-extended messages by default     enableMsgType(MTK_CAMERA_MSG_EXT_NOTIFY |MTK_CAMERA_MSG_EXT_DATA); #endif //!--     LOG1("CameraClient::initialize X (pid%d, id %d)", callingPid, mCameraId);     return OK; } 8.       在CameraService的onFirstRef方法中，會加載CameraHal  Module void CameraService:: onFirstRef() {     BnCameraService::onFirstRef();       if (hw_get_module(CAMERA_HARDWARE_MODULE_ID,                 (const hw_module_t**)&mModule) < 0) {         ALOGE("Could not load camera HALmodule");         mNumberOfCameras = 0;     }     else {         mNumberOfCameras =mModule->get_number_of_cameras();         if (mNumberOfCameras > MAX_CAMERAS){             ALOGE("Number of cameras(%d)> MAX_CAMERAS(%d).",                     mNumberOfCameras, MAX_CAMERAS);             mNumberOfCameras = MAX_CAMERAS;         }         for (int i = 0; i <mNumberOfCameras; i++) {             setCameraFree(i);         }     } } hw_get_module方法的實現在hardware/libhardware/Hardware.c文件中實現 int hw_get_module(constchar *id, const struct hw_module_t **module) {     return hw_get_module_by_class(id, NULL,module); } Camera_module_t的結構體定義在camera_common.h文件中 typedef structcamera_module {     hw_module_t common;     int (*get_number_of_cameras)(void);     int (*get_camera_info)(int camera_id,struct camera_info *info); } camera_module_t; Hw_module_t的定義在hardware.h文件中，hw_module_t持有對hw_module_methods_t引用，其中有定義一個open指針 typedef structhw_module_methods_t {     /** Open a specific device */     int (*open)(const struct hw_module_t*module, const char* id,             struct hw_device_t** device);   } hw_module_methods_t; 而加載CamDevice的操作是在CameraHardwareInterface的init方法中調用open         int rc =module->methods->open(module, mName.string(),                                        (hw_device_t **)&mDevice);