Android Camera FW到Camera Hal调用流程

来源：互联网发布：ubuntu vim设置编辑：程序博客网时间：2024/05/29 13:21

1. 首先是调用framework层的Camera.java(frameworks\base\core\java\android\hardware)的takePicture方法

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::DeathRecipientconstsp<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都继承自IInterface，也就是Binder通信的基础，此外ICamera.h也继承自IInterface

class ICameraClient:public IInterface

class ICameraService :public IInterface

class ICamera: publicIInterface

然后发现BnCameraClient继承自BnInterface<ICameraClient>，作为ICameraClient的服务器端存在：

class BnCameraClient: publicBnInterface<ICameraClient>

BnCameraService继承自BnInterface<ICameraService>，作为ICameraService的服务器端存在：

class BnCameraService: publicBnInterface<ICameraService>

BnCamera继承自BnInterface<ICamera>，作为ICamera的服务器端存在：

class BnCamera: public BnInterface<ICamera>

对应的上述三个分别存在一个作为Binder客户端的类存在，为Bp***：

class BpCameraClient:public BpInterface<ICameraClient>

class BpCameraService:public BpInterface<ICameraService>

class BpCamera: publicBpInterface<ICamera>

上述三个的实现分别在ICameraClient.cpp、ICameraService.cpp、ICamera.cpp,在这三支文件中分别实现了三组Binder的Server端和Client端，Camera常用的方法都在ICamera中实现。

5. Camera.cpp文件connect方法在JNI层去setupCamera的时候会调用，JNI层是在上层opencamera的时候被调用的，在camera.cpp的connect方法中获取一个ICamera对象来完成对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 BnCameraclass CameraClient : public CameraService::Clientwp<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());

并且Google好像有开发新的API2.0，在此处通过判断不同的version实例化不同的CameraClient的Binder引用对象回去，目前Camera2文件夹有Burst等实现

7. 在CameraService层的CameraClient对象的定义中，持有CameraHardwareInterface对象的引用mHardware.在CameraClient的initilize方法中会创建此对象，在对象的构造方法中传入需要打开的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，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);        }    }}

hw_get_module方法的实现在hardware/libhardware/Hardware.c文件中实现

int hw_get_module(constchar *id, const struct hw_module_t **module)

{

return hw_get_module_by_class(id, NULL,module);

}

Camera_module_t的结构体定义在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的定义在hardware.h文件中，hw_module_t持有对hw_module_methods_t引用，其中有定义一个open指针

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;

而加载CamDevice的操作是在CameraHardwareInterface的init方法中调用open

int rc =module->methods->open(module, mName.string(),

(hw_device_t **)&mDevice);

转载：http://www.2cto.com/kf/201303/196681.html

可参考：http://blog.163.com/shawpin@126/blog/static/116663752201092394147937/

0 0