Android Camera FW到Camera Hal调用流程

2.       接着会调用到JNI层的android_hardware_Camera.cpp(frameworks\base\core\jni)的android_hardware_Camera_takePicture方法，其中会通过get_native_camera获取一个Camera对象。

3.       上述Camera对象的定义在Camera.h(frameworks\av\include\camera)，camera.h同时定义了CameraInfo。Camera对象继承自publicBnCameraClient,DeathRecipient。Camera对象的真正实现是在Camera.cpp(frameworks\av\camera)   。BnCameraClient是作为CameraService回调而存在的。Camera对象内含有一个mCameraService变量用于保存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);}

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定义内部类Client，CameraClient继承此类，在CameraService中持有对mClient对象的一个数组，这个数组也是Camera.cpp客户端调用connect方法后需要返回的Binder引用对象

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());

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 defaultenableMsgType(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 defaultenableMsgType(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，会加载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);}}
}