之前在 Android Camera 的执行流程http://blog.chinaunix.net/uid-26765074-id-3499537.html 这篇文章中已经详细介绍了 Android Camera app到调用open打开camera 设备的完成过程，但是只是到此为止，并未对较底层的操作控制等做任何分析， 今天就要进入这个环节了 
这里就直接从open那个方法开始了，先说一下这个open是怎么被调用的
实例化Camera Hal接口 hardware，hardware调用initialize()进入HAL层打开Camear驱动。 CameraHardwareInterface中initialize()定义在以下路径:frameworks/base/services/camera/libcameraservice/CameraHardwareInterface.h
代码如下：
status_t initialize(hw_module_t *module) { LOGI("Opening camera %s", mName.string()); int rc = module->methods->open(module, mName.string(),(hw_device_t **)&mDevice); if (rc != OK) { LOGE("Could not open camera %s: %d", mName.string(), rc); return rc; } #ifdef OMAP_ENHANCEMENT_CPCAM initHalPreviewWindow(&mHalPreviewWindow); initHalPreviewWindow(&mHalTapin); initHalPreviewWindow(&mHalTapout); #else initHalPreviewWindow(); #endif return rc; } 此处通过module->method->open()方法真正打开Camera设备,
其中module的定义在以下路径:frameworks/base/services/camera/libcameraservice/CameraService.h
class CameraService : public BinderService<CameraService>, public BnCameraService {
class Client : public BnCamera
{
public:
......
private:
.....
};
camera_module_t *mModule;
};
此处还必须找到camera_module_t 的定义,以更好的理解整个运行流程,通过追根溯源找到了camera_module_t 定义,
camera_module_t的定义在以下路径:hardware/libhardware/include/hardware/camera.h
typedef struct camera_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; 其中包含get_number_of_cameras方法和get_camera_info方法用于获取camera info
另外hw_module_t common;这个选项十分重要,此处应重点关注,因为是使用hw_module_t结构体中的open()方法打开设备文件的
继续找到hw_module_t 结构体的定义.在以下路径:hardware/libhardware/include/hardware/hardware.h
typedef struct hw_module_t {
/** tag must be initialized to HARDWARE_MODULE_TAG */
uint32_t tag;
/** major version number for the module */
uint16_t version_major;
/** minor version number of the module */
uint16_t version_minor;
/** Identifier of module */
const char *id;
/** Name of this module */
const char *name;
/** Author/owner/implementor of the module */
const char *author;
/** Modules methods */
struct hw_module_methods_t* methods;
/** module's dso */
void* dso;
/** padding to 128 bytes, reserved for future use */
uint32_t reserved[32-7];
} hw_module_t;
typedef struct hw_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;
这里的这个open方法才是我们真正调用的open方法，那么这里只是定义，他又是在哪里实现的呢？？ 这个问题我们还是需要往前面追溯啊，当然这在上一篇文章中也没有提到，不卖关子了，其实重点就是我们调用了这个module->methods->open(module, mName.string(),(hw_device_t **)&mDevice)方法 但是这个module是在哪里初始化的呢？看看CameraService类里的这个方法吧，路径：frameworks/base/services/camera/libcameraservice/CameraService.cpp
void CameraService::onFirstRef()
{
BnCameraService::onFirstRef();
if (hw_get_module(CAMERA_HARDWARE_MODULE_ID,
(const hw_module_t **)&mModule) < 0) {
LOGE("Could not load camera HAL module");
mNumberOfCameras = 0;
}
else {
mNumberOfCameras = mModule->get_number_of_cameras();
if (mNumberOfCameras > MAX_CAMERAS) {
LOGE("Number of cameras(%d) > MAX_CAMERAS(%d).",
mNumberOfCameras, MAX_CAMERAS);
mNumberOfCameras = MAX_CAMERAS;
}
for (int i = 0; i < mNumberOfCameras; i++) {
setCameraFree(i);
}
}
}
不错，这个module正是通过这个hw_get_module方法获得的，其实他是通过方法中的CAMERA_HARDWARE_MODULE_ID作为flag最终找到已经定义好的module，那么这个已经定义好的module又在哪呢，是什么样子的呢？ 这里我就直接放在这里，不在拐弯抹角了，方法路径：hardware/ti/omap4xxx/camera/CameraHal_Module.cpp
static int camera_device_open(const hw_module_t* module, const char* name,
hw_device_t** device);
static int camera_device_close(hw_device_t* device);
static int camera_get_number_of_cameras(void);
static int camera_get_camera_info(int camera_id, struct camera_info *info);
static struct hw_module_methods_t camera_module_methods = {
open: camera_device_open
};
camera_module_t HAL_MODULE_INFO_SYM = {
common: {
tag: HARDWARE_MODULE_TAG,
version_major: 1,
version_minor: 0,
id: CAMERA_HARDWARE_MODULE_ID,
name: "TI OMAP CameraHal Module",
author: "TI",
methods: &camera_module_methods,
dso: NULL, /* remove compilation warnings */
reserved: {0}, /* remove compilation warnings */
},
get_number_of_cameras: camera_get_number_of_cameras,
get_camera_info: camera_get_camera_info,
};
这里还是很关键的，通过id：CAMERA_HARDWARE_MODULE_ID作为识别码找到这个module，get module完成任务，大家可以看到，这个定义好的module实现了methods中的open方法， 实现了camera_get_number_of_cameras和camera_get_camera_info，当然还包括了其他一些变量的初始化 这里开始我们找到了我们真正需要的open方法，万里长征走完一大步了，现在就去看看这个open方法干了些什么吧
/* open device handle to one of the cameras
*
* assume camera service will keep singleton of each camera
* so this function will always only be called once per camera instance
*/
int camera_device_open(const hw_module_t* module, const char* name,
hw_device_t** device)
{
int rv = 0;
int num_cameras = 0;
int cameraid;
ti_camera_device_t* camera_device = NULL;
camera_device_ops_t* camera_ops = NULL;
android::CameraHal* camera = NULL;
android::CameraProperties::Properties* properties = NULL;
android::Mutex::Autolock lock(gCameraHalDeviceLock);
CAMHAL_LOGI("camera_device open");
if (name != NULL) {
cameraid = atoi(name);
num_cameras = gCameraProperties.camerasSupported();
if(cameraid > num_cameras)
{
LOGE("camera service provided cameraid out of bounds, "
"cameraid = %d, num supported = %d",
cameraid, num_cameras);
rv = -EINVAL;
goto fail;
}
if(gCamerasOpen >= MAX_SIMUL_CAMERAS_SUPPORTED)
{
LOGE("maximum number of cameras already open");
rv = -ENOMEM;
goto fail;
}
camera_device = (ti_camera_device_t*)malloc(sizeof(*camera_device));
if(!camera_device)
{
LOGE("camera_device allocation fail");
rv = -ENOMEM;
goto fail;
}
camera_ops = (camera_device_ops_t*)malloc(sizeof(*camera_ops));
if(!camera_ops)
{
LOGE("camera_ops allocation fail");
rv = -ENOMEM;
goto fail;
}
memset(camera_device, 0, sizeof(*camera_device));
memset(camera_ops, 0, sizeof(*camera_ops));
camera_device->base.common.tag = HARDWARE_DEVICE_TAG;
camera_device->base.common.version = 0;
camera_device->base.common.module = (hw_module_t *)(module);
camera_device->base.common.close = camera_device_close;
camera_device->base.ops = camera_ops;
camera_ops->set_preview_window = camera_set_preview_window;
#ifdef OMAP_ENHANCEMENT_CPCAM
camera_ops->set_buffer_source = camera_set_buffer_source;
#endif
camera_ops->set_callbacks = camera_set_callbacks;
camera_ops->enable_msg_type = camera_enable_msg_type;
camera_ops->disable_msg_type = camera_disable_msg_type;
camera_ops->msg_type_enabled = camera_msg_type_enabled;
camera_ops->start_preview = camera_start_preview;
camera_ops->stop_preview = camera_stop_preview;
camera_ops->preview_enabled = camera_preview_enabled;
camera_ops->store_meta_data_in_buffers = camera_store_meta_data_in_buffers;
camera_ops->start_recording = camera_start_recording;
camera_ops->stop_recording = camera_stop_recording;
camera_ops->recording_enabled = camera_recording_enabled;
camera_ops->release_recording_frame = camera_release_recording_frame;
camera_ops->auto_focus = camera_auto_focus;
camera_ops->cancel_auto_focus = camera_cancel_auto_focus;
camera_ops->take_picture = camera_take_picture;
camera_ops->cancel_picture = camera_cancel_picture;
camera_ops->set_parameters = camera_set_parameters;
camera_ops->get_parameters = camera_get_parameters;
camera_ops->put_parameters = camera_put_parameters;
camera_ops->send_command = camera_send_command;
camera_ops->release = camera_release;
camera_ops->dump = camera_dump;
#ifdef OMAP_ENHANCEMENT_CPCAM
camera_ops->reprocess = camera_reprocess;
camera_ops->cancel_reprocess = camera_cancel_reprocess;
#endif
*device = &camera_device->base.common;
// -------- TI specific stuff --------
camera_device->cameraid = cameraid;
if(gCameraProperties.getProperties(cameraid, &properties) < 0)
{
LOGE("Couldn't get camera properties");
rv = -ENOMEM;
goto fail;
}
camera = new android::CameraHal(cameraid);
if(!camera)
{
LOGE("Couldn't create instance of CameraHal class");
rv = -ENOMEM;
goto fail;
}
if(properties && (camera->initialize(properties) != android::NO_ERROR))
{
LOGE("Couldn't initialize camera instance");
rv = -ENODEV;
goto fail;
}
gCameraHals[cameraid] = camera;
gCamerasOpen++;
}
return rv;
fail:
if(camera_device) {
free(camera_device);
camera_device = NULL;
}
if(camera_ops) {
free(camera_ops);
camera_ops = NULL;
}
if(camera) {
delete camera;
camera = NULL;
}
*device = NULL;
return rv;
}
看看这么长的代码，open的任务还是比较中的，没办法，能者多劳嘛，红色部分是最重点的部分 从这里可以知道，这里就像一个控制中心，上传调用到这里被分发出去，实现各自的操作，我们就以startPreview为例进行分析
int camera_start_preview(struct camera_device * device)
{
int rv = -EINVAL;
ti_camera_device_t* ti_dev = NULL;
LOGV("%s", __FUNCTION__);
if(!device)
return rv;
ti_dev = (ti_camera_device_t*) device;
rv = gCameraHals[ti_dev->cameraid]->startPreview();
return rv;
}
这里每open一个device就会相应的创建并且初始化一个CameraHal 对象，定义在：hardware/ti/omap4xxx/camera/CameraHal.cpp 并且把这个对象保存在gCameraHals这个数组中，正因为这样这里camera_start_preview才可以通过这个数据检索对象调用方法 现在我们就看看这个startPreview()方法是怎样实现的
/**
@brief Start preview mode.
@param none
@return NO_ERROR Camera switched to VF mode
@todo Update function header with the different errors that are possible
*/
status_t CameraHal::startPreview() {
LOG_FUNCTION_NAME;
// When tunneling is enabled during VTC, startPreview happens in 2 steps:
// When the application sends the command CAMERA_CMD_PREVIEW_INITIALIZATION,
// cameraPreviewInitialization() is called, which in turn causes the CameraAdapter
// to move from loaded to idle state. And when the application calls startPreview,
// the CameraAdapter moves from idle to executing state.
//
// If the application calls startPreview() without sending the command
// CAMERA_CMD_PREVIEW_INITIALIZATION, then the function cameraPreviewInitialization()
// AND startPreview() are executed. In other words, if the application calls
// startPreview() without sending the command CAMERA_CMD_PREVIEW_INITIALIZATION,
// then the CameraAdapter moves from loaded to idle to executing state in one shot.
status_t ret = cameraPreviewInitialization();
// The flag mPreviewInitializationDone is set to true at the end of the function
// cameraPreviewInitialization(). Therefore, if everything goes alright, then the
// flag will be set. Sometimes, the function cameraPreviewInitialization() may
// return prematurely if all the resources are not available for starting preview.
// For example, if the preview window is not set, then it would return NO_ERROR.
// Under such circumstances, one should return from startPreview as well and should
// not continue execution. That is why, we check the flag and not the return value.
if (!mPreviewInitializationDone) return ret;
// Once startPreview is called, there is no need to continue to remember whether
// the function cameraPreviewInitialization() was called earlier or not. And so
// the flag mPreviewInitializationDone is reset here. Plus, this preserves the
// current behavior of startPreview under the circumstances where the application
// calls startPreview twice or more.
mPreviewInitializationDone = false;
///Enable the display adapter if present, actual overlay enable happens when we post the buffer
if(mDisplayAdapter.get() != NULL) {
CAMHAL_LOGDA("Enabling display");
int width, height;
mParameters.getPreviewSize(&width, &height);
#if PPM_INSTRUMENTATION || PPM_INSTRUMENTATION_ABS
ret = mDisplayAdapter->enableDisplay(width, height, &mStartPreview);
#else
ret = mDisplayAdapter->enableDisplay(width, height, NULL);
#endif
if ( ret != NO_ERROR ) {
CAMHAL_LOGEA("Couldn't enable display");
// FIXME: At this stage mStateSwitchLock is locked and unlock is supposed to be called
// only from mCameraAdapter->sendCommand(CameraAdapter::CAMERA_START_PREVIEW)
// below. But this will never happen because of goto error. Thus at next
// startPreview() call CameraHAL will be deadlocked.
// Need to revisit mStateSwitch lock, for now just abort the process.
CAMHAL_ASSERT_X(false,
"At this stage mCameraAdapter->mStateSwitchLock is still locked, "
"deadlock is guaranteed");
goto error;
}
}
///Send START_PREVIEW command to adapter
CAMHAL_LOGDA("Starting CameraAdapter preview mode");
ret = mCameraAdapter->sendCommand(CameraAdapter::CAMERA_START_PREVIEW);
if(ret!=NO_ERROR) {
CAMHAL_LOGEA("Couldn't start preview w/ CameraAdapter");
goto error;
}
CAMHAL_LOGDA("Started preview");
mPreviewEnabled = true;
mPreviewStartInProgress = false;
return ret;
error:
CAMHAL_LOGEA("Performing cleanup after error");
//Do all the cleanup
freePreviewBufs();
mCameraAdapter->sendCommand(CameraAdapter::CAMERA_STOP_PREVIEW);
if(mDisplayAdapter.get() != NULL) {
mDisplayAdapter->disableDisplay(false);
}
mAppCallbackNotifier->stop();
mPreviewStartInProgress = false;
mPreviewEnabled = false;
LOG_FUNCTION_NAME_EXIT;
return ret;
}
在我的理解看来上面标注的部分是这个方法的关键，这个地方可是会让初次研究这里的人晕头转向的，因为我就在这里犯了错误，走岔道了，下面会说明到底是怎么走岔道的： 先说一下吧，这里调用mCameraAdapter对象的sendCommand方法
status_t BaseCameraAdapter::sendCommand(CameraCommands operation, int value1, int value2, int value3, int value4) {
status_t ret = NO_ERROR;
struct timeval *refTimestamp;
BuffersDescriptor *desc = NULL;
CameraFrame *frame = NULL;
LOG_FUNCTION_NAME;
switch ( operation ) {
case：
...............
case CameraAdapter::CAMERA_START_PREVIEW: { CAMHAL_LOGDA("Start Preview"); if ( ret == NO_ERROR ) { ret = setState(operation); }
if ( ret == NO_ERROR ) { ret = startPreview(); }
if ( ret == NO_ERROR ) { ret = commitState(); }else{ ret |= rollbackState(); } break; }
}
}
status_t BaseCameraAdapter::setState(CameraCommands operation)
{
status_t ret = NO_ERROR;
LOG_FUNCTION_NAME;
const char *printState = getLUTvalue_translateHAL(operation, CamCommandsLUT);
mLock.lock();
switch ( mAdapterState )
{
case INTIALIZED_STATE:
............
case LOADED_PREVIEW_STATE:
switch ( operation )
{
case CAMERA_START_PREVIEW:
CAMHAL_LOGDB("Adapter state switch LOADED_PREVIEW_STATE->PREVIEW_STATE event = %s",
printState);
mNextState = PREVIEW_STATE;
break;
}
}
}
status_t BaseCameraAdapter::startPreview()
{
status_t ret = NO_ERROR;
LOG_FUNCTION_NAME;
LOG_FUNCTION_NAME_EXIT;
return ret;
}
就是这里了，所以我用可很醒目的颜色标注出来，很多人会想当然的理解，你不是调用了startPreview方法嘛，那就是他了啊！可是这里为什么什么动作都没做呢？？ 于是就卡在这里不知所措了，那个纠结啊
现在就来解开这个谜团吧！！！
这个我们还是要往前追溯了，追溯到哪里呢？？那就从这里开始吧 mCameraAdapter->sendCommand(CameraAdapter::CAMERA_START_PREVIEW); 这个方式是在CameraHal的startPreview()方法中被调用的 所以我要知道这个mCameraAdapter对象原型是什么啊，他从哪里而来，原来他是CameraHal这个类的一个成员，定义在：hardware/ti/omap4xxx/camera/inc/CameraHal.h CameraAdapter *mCameraAdapter; 这里必须打破砂锅追到底，找到CameraAdapter 这个类的定义，他的定义同样这这个.h文件中
/**
* CameraAdapter interface class
* Concrete classes derive from this class and provide implementations based on the specific camera h/w interface
*/
class CameraAdapter: public FrameNotifier, public virtual RefBase
{
protected:
enum AdapterActiveStates {
INTIALIZED_ACTIVE = 1 << 0,
LOADED_PREVIEW_ACTIVE = 1 << 1,
PREVIEW_ACTIVE = 1 << 2,
LOADED_CAPTURE_ACTIVE = 1 << 3,
CAPTURE_ACTIVE = 1 << 4,
BRACKETING_ACTIVE = 1 << 5,
AF_ACTIVE = 1 << 6,
ZOOM_ACTIVE = 1 << 7,
VIDEO_ACTIVE = 1 << 8,
LOADED_REPROCESS_ACTIVE = 1 << 9,
REPROCESS_ACTIVE = 1 << 10,
};
public:
typedef struct
{
CameraBuffer *mBuffers;
uint32_t *mOffsets;
int mFd;
size_t mLength;
size_t mCount;
size_t mMaxQueueable;
} BuffersDescriptor;
enum CameraCommands
{
CAMERA_START_PREVIEW = 0,
CAMERA_STOP_PREVIEW = 1,
CAMERA_START_VIDEO = 2,
CAMERA_STOP_VIDEO = 3,
CAMERA_START_IMAGE_CAPTURE = 4,
CAMERA_STOP_IMAGE_CAPTURE = 5,
CAMERA_PERFORM_AUTOFOCUS = 6,
CAMERA_CANCEL_AUTOFOCUS = 7,
CAMERA_PREVIEW_FLUSH_BUFFERS = 8,
CAMERA_START_SMOOTH_ZOOM = 9,
CAMERA_STOP_SMOOTH_ZOOM = 10,
CAMERA_USE_BUFFERS_PREVIEW = 11,
CAMERA_SET_TIMEOUT = 12,
CAMERA_CANCEL_TIMEOUT = 13,
CAMERA_START_BRACKET_CAPTURE = 14,
CAMERA_STOP_BRACKET_CAPTURE = 15,
CAMERA_QUERY_RESOLUTION_PREVIEW = 16,
CAMERA_QUERY_BUFFER_SIZE_IMAGE_CAPTURE = 17,
CAMERA_QUERY_BUFFER_SIZE_PREVIEW_DATA = 18,
CAMERA_USE_BUFFERS_IMAGE_CAPTURE = 19,
CAMERA_USE_BUFFERS_PREVIEW_DATA = 20,
CAMERA_TIMEOUT_EXPIRED = 21,
CAMERA_START_FD = 22,
CAMERA_STOP_FD = 23,
CAMERA_SWITCH_TO_EXECUTING = 24,
CAMERA_USE_BUFFERS_VIDEO_CAPTURE = 25,
#ifdef OMAP_ENHANCEMENT_CPCAM
CAMERA_USE_BUFFERS_REPROCESS = 26,
CAMERA_START_REPROCESS = 27,
#endif
#ifdef OMAP_ENHANCEMENT_VTC
CAMERA_SETUP_TUNNEL = 28,
CAMERA_DESTROY_TUNNEL = 29,
#endif
CAMERA_PREVIEW_INITIALIZATION = 30,
};
enum CameraMode
{
CAMERA_PREVIEW,
CAMERA_IMAGE_CAPTURE,
CAMERA_VIDEO,
CAMERA_MEASUREMENT,
CAMERA_REPROCESS,
};
enum AdapterState {
INTIALIZED_STATE = INTIALIZED_ACTIVE,
LOADED_PREVIEW_STATE = LOADED_PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
PREVIEW_STATE = PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
LOADED_CAPTURE_STATE = LOADED_CAPTURE_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
CAPTURE_STATE = CAPTURE_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
BRACKETING_STATE = BRACKETING_ACTIVE | CAPTURE_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE ,
AF_STATE = AF_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
ZOOM_STATE = ZOOM_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
VIDEO_STATE = VIDEO_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
VIDEO_AF_STATE = VIDEO_ACTIVE | AF_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
VIDEO_ZOOM_STATE = VIDEO_ACTIVE | ZOOM_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
VIDEO_LOADED_CAPTURE_STATE = VIDEO_ACTIVE | LOADED_CAPTURE_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
VIDEO_CAPTURE_STATE = VIDEO_ACTIVE | CAPTURE_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
AF_ZOOM_STATE = AF_ACTIVE | ZOOM_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
BRACKETING_ZOOM_STATE = BRACKETING_ACTIVE | ZOOM_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
LOADED_REPROCESS_STATE = LOADED_REPROCESS_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
LOADED_REPROCESS_CAPTURE_STATE = LOADED_REPROCESS_ACTIVE | LOADED_CAPTURE_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
REPROCESS_STATE = REPROCESS_ACTIVE | CAPTURE_ACTIVE | PREVIEW_ACTIVE | INTIALIZED_ACTIVE,
};
public:
///Initialzes the camera adapter creates any resources required
virtual int initialize(CameraProperties::Properties*) = 0;
virtual int setErrorHandler(ErrorNotifier *errorNotifier) = 0;
//Message/Frame notification APIs
virtual void enableMsgType(int32_t msgs,
frame_callback callback = NULL,
event_callback eventCb = NULL,
void *cookie = NULL) = 0;
virtual void disableMsgType(int32_t msgs, void* cookie) = 0;
virtual void returnFrame(CameraBuffer* frameBuf, CameraFrame::FrameType frameType) = 0;
virtual void addFramePointers(CameraBuffer *frameBuf, void *buf) = 0;
virtual void removeFramePointers() = 0;
//APIs to configure Camera adapter and get the current parameter set
virtual int setParameters(const CameraParameters& params) = 0;
virtual void getParameters(CameraParameters& params) = 0;
//Registers callback for returning image buffers back to CameraHAL
virtual int registerImageReleaseCallback(release_image_buffers_callback callback, void *user_data) = 0;
//Registers callback, which signals a completed image capture
virtual int registerEndCaptureCallback(end_image_capture_callback callback, void *user_data) = 0;
//API to send a command to the camera
virtual status_t sendCommand(CameraCommands operation, int value1=0, int value2=0, int value3=0, int value4=0) = 0;
virtual ~CameraAdapter() {};
//Retrieves the current Adapter state
virtual AdapterState getState() = 0;
//Retrieves the next Adapter state
virtual AdapterState getNextState() = 0;
// Receive orientation events from CameraHal
virtual void onOrientationEvent(uint32_t orientation, uint32_t tilt) = 0;
// Rolls the state machine back to INTIALIZED_STATE from the current state
virtual status_t rollbackToInitializedState() = 0;
// Retrieves the current Adapter state - for internal use (not locked)
virtual status_t getState(AdapterState &state) = 0;
// Retrieves the next Adapter state - for internal use (not locked)
virtual status_t getNextState(AdapterState &state) = 0;
protected:
//The first two methods will try to switch the adapter state.
//Every call to setState() should be followed by a corresponding
//call to commitState(). If the state switch fails, then it will
//get reset to the previous state via rollbackState().
virtual status_t setState(CameraCommands operation) = 0;
virtual status_t commitState() = 0;
virtual status_t rollbackState() = 0;
};
看一下我标出的这是红色部分啊，为什么我要把它们标注成红色呢？？ 懂C++面向对象思想应该都知道virtual这个关键字是干什么的， 如果一个类的方法被定义为virtual，如果该类的子类实现了同样的方法，则这个方法被调用的时候，会忽略父类的实现，而直接调用子类的实现，前提是方法名，包括变量类型，个数必须一致 那么这里有没有类继承了CameraAdapter 这个类，并且实现了其中的一些虚拟函数呢？？答案是肯定的，我可是吃了苦头才发现的 不过也是赖自己，这是只有定义是没有实现的，肯定是由子类来实现这是方法的，不，还是不赖自己，让我吃苦头的是这里是双层继承的，双层继承啊，我怎么知道 不卖关子了，那么谁继承了CameraAdapter 这个类呢？ 先给路径：hardware/ti/omap4xxx/camera/inc/BaseCameraAdapter.h
class BaseCameraAdapter : public CameraAdapter
{
public:
BaseCameraAdapter();
virtual ~BaseCameraAdapter();
///Initialzes the camera adapter creates any resources required
virtual status_t initialize(CameraProperties::Properties*) = 0;
virtual int setErrorHandler(ErrorNotifier *errorNotifier);
//Message/Frame notification APIs
virtual void enableMsgType(int32_t msgs, frame_callback callback=NULL, event_callback eventCb=NULL, void* cookie=NULL);
virtual void disableMsgType(int32_t msgs, void* cookie);
virtual void returnFrame(CameraBuffer * frameBuf, CameraFrame::FrameType frameType);
virtual void addFramePointers(CameraBuffer *frameBuf, void *y_uv);
virtual void removeFramePointers();
//APIs to configure Camera adapter and get the current parameter set
virtual status_t setParameters(const CameraParameters& params) = 0;
virtual void getParameters(CameraParameters& params) = 0;
//API to send a command to the camera
virtual status_t sendCommand(CameraCommands operation, int value1 = 0, int value2 = 0, int value3 = 0, int value4 = 0 );
virtual status_t registerImageReleaseCallback(release_image_buffers_callback callback, void *user_data);
virtual status_t registerEndCaptureCallback(end_image_capture_callback callback, void *user_data);
//Retrieves the current Adapter state
virtual AdapterState getState();
//Retrieves the next Adapter state
virtual AdapterState getNextState();
// Rolls the state machine back to INTIALIZED_STATE from the current state
virtual status_t rollbackToInitializedState();
protected:
//The first two methods will try to switch the adapter state.
//Every call to setState() should be followed by a corresponding
//call to commitState(). If the state switch fails, then it will
//get reset to the previous state via rollbackState().
virtual status_t setState(CameraCommands operation);
virtual status_t commitState();
virtual status_t rollbackState();
// Retrieves the current Adapter state - for internal use (not locked)
virtual status_t getState(AdapterState &state);
// Retrieves the next Adapter state - for internal use (not locked)
virtual status_t getNextState(AdapterState &state);
//-----------Interface that needs to be implemented by deriving classes --------------------
//Should be implmented by deriving classes in order to start image capture
virtual status_t takePicture();
//Should be implmented by deriving classes in order to start image capture
virtual status_t stopImageCapture();
//Should be implmented by deriving classes in order to start temporal bracketing
virtual status_t startBracketing(int range);
//Should be implemented by deriving classes in order to stop temporal bracketing
virtual status_t stopBracketing();
//Should be implemented by deriving classes in oder to initiate autoFocus
virtual status_t autoFocus();
//Should be implemented by deriving classes in oder to initiate autoFocus
virtual status_t cancelAutoFocus();
//Should be called by deriving classes in order to do some bookkeeping
virtual status_t startVideoCapture();
//Should be called by deriving classes in order to do some bookkeeping
virtual status_t stopVideoCapture();
//Should be implemented by deriving classes in order to start camera preview
virtual status_t startPreview();
//Should be implemented by deriving classes in order to stop camera preview
virtual status_t stopPreview();
//Should be implemented by deriving classes in order to start smooth zoom
virtual status_t startSmoothZoom(int targetIdx);
//Should be implemented by deriving classes in order to stop smooth zoom
virtual status_t stopSmoothZoom();
//Should be implemented by deriving classes in order to stop smooth zoom
virtual status_t useBuffers(CameraMode mode, CameraBuffer* bufArr, int num, size_t length, unsigned int queueable);
//Should be implemented by deriving classes in order queue a released buffer in CameraAdapter
virtual status_t fillThisBuffer(CameraBuffer* frameBuf, CameraFrame::FrameType frameType);
//API to get the frame size required to be allocated. This size is used to override the size passed
//by camera service when VSTAB/VNF is turned ON for example
virtual status_t getFrameSize(size_t &width, size_t &height);
//API to get required data frame size
virtual status_t getFrameDataSize(size_t &dataFrameSize, size_t bufferCount);
//API to get required picture buffers size with the current configuration in CameraParameters
virtual status_t getPictureBufferSize(size_t &length, size_t bufferCount);
// Should be implemented by deriving classes in order to start face detection
// ( if supported )
virtual status_t startFaceDetection();
// Should be implemented by deriving classes in order to stop face detection
// ( if supported )
virtual status_t stopFaceDetection();
virtual status_t switchToExecuting();
virtual status_t setupTunnel(uint32_t SliceHeight, uint32_t EncoderHandle, uint32_t width, uint32_t height);
virtual status_t destroyTunnel();
virtual status_t cameraPreviewInitialization();
// Receive orientation events from CameraHal
virtual void onOrientationEvent(uint32_t orientation, uint32_t tilt);
// ---------------------Interface ends-----------------------------------
status_t notifyFocusSubscribers(CameraHalEvent::FocusStatus status);
status_t notifyShutterSubscribers();
status_t notifyZoomSubscribers(int zoomIdx, bool targetReached);
status_t notifyMetadataSubscribers(sp<CameraMetadataResult> &meta);
//Send the frame to subscribers
status_t sendFrameToSubscribers(CameraFrame *frame);
//Resets the refCount for this particular frame
status_t resetFrameRefCount(CameraFrame &frame);
//A couple of helper functions
void setFrameRefCount(CameraBuffer* frameBuf, CameraFrame::FrameType frameType, int refCount);
int getFrameRefCount(CameraBuffer* frameBuf, CameraFrame::FrameType frameType);
int setInitFrameRefCount(CameraBuffer* buf, unsigned int mask);
static const char* getLUTvalue_translateHAL(int Value, LUTtypeHAL LUT);
.................
.................
}
这里我只列出了一部分代码，不过大家清楚了，BaseCameraAdapter 继承CameraAdapter，不过这里还没完呢，看看这个类中定义的方法 那么多的virtual 方法，后来自己才发现的，他还是被别的类继承了，而且其中的很多方法被子类重新实现了 所以实现上上面调用的startPreview方法其实不是BaseCameraAdapter.cpp中实现的那个startPreview方法 那挺调用的startPreview方法在哪里呢，自然是继承了BaseCameraAdapter 类的那个子类实现的startPreview 现在就把这个罪魁祸首拉上来，先看定义：hardware/ti/omap4xxx/camera/inc/V4LCameraAdapter/V4LCameraAdapter.h
/**
* Class which completely abstracts the camera hardware interaction from camera hal
* TODO: Need to list down here, all the message types that will be supported by this class
Need to implement BufferProvider interface to use AllocateBuffer of OMX if needed
*/
class V4LCameraAdapter : public BaseCameraAdapter
{
public:
/*--------------------Constant declarations----------------------------------------*/
static const int32_t MAX_NO_BUFFERS = 20;
///@remarks OMX Camera has six ports - buffer input, time input, preview, image, video, and meta data
static const int MAX_NO_PORTS = 6;
///Five second timeout
static const int CAMERA_ADAPTER_TIMEOUT = 5000*1000;
public:
V4LCameraAdapter(size_t sensor_index);
~V4LCameraAdapter();
///Initialzes the camera adapter creates any resources required
virtual status_t initialize(CameraProperties::Properties*);
//APIs to configure Camera adapter and get the current parameter set
virtual status_t setParameters(const CameraParameters& params);
virtual void getParameters(CameraParameters& params);
// API
virtual status_t UseBuffersPreview(CameraBuffer *bufArr, int num);
virtual status_t UseBuffersCapture(CameraBuffer *bufArr, int num);
static status_t getCaps(const int sensorId, CameraProperties::Properties* params, V4L_HANDLETYPE handle);
protected:
//----------Parent class method implementation------------------------------------//看看人家这里说的很清楚，这是父类的方法
virtual status_t startPreview();
virtual status_t stopPreview();
virtual status_t takePicture();
virtual status_t stopImageCapture();
virtual status_t autoFocus();
virtual status_t useBuffers(CameraMode mode, CameraBuffer *bufArr, int num, size_t length, unsigned int queueable);
virtual status_t fillThisBuffer(CameraBuffer *frameBuf, CameraFrame::FrameType frameType);
virtual status_t getFrameSize(size_t &width, size_t &height);
virtual status_t getPictureBufferSize(size_t &length, size_t bufferCount);
virtual status_t getFrameDataSize(size_t &dataFrameSize, size_t bufferCount);
virtual void onOrientationEvent(uint32_t orientation, uint32_t tilt);
//-----------------------------------------------------------------------------
private:
class PreviewThread : public Thread {
V4LCameraAdapter* mAdapter;
public:
PreviewThread(V4LCameraAdapter* hw) :
Thread(false), mAdapter(hw) { }
virtual void onFirstRef() {
run("CameraPreviewThread", PRIORITY_URGENT_DISPLAY);
}
virtual bool threadLoop() {
mAdapter->previewThread();
// loop until we need to quit
return true;
}
};
//Used for calculation of the average frame rate during preview
status_t recalculateFPS();
char * GetFrame(int &index);
int previewThread();
public:
private:
//capabilities data
static const CapPixelformat mPixelformats [];
static const CapResolution mPreviewRes [];
static const CapFramerate mFramerates [];
static const CapResolution mImageCapRes [];
//camera defaults
static const char DEFAULT_PREVIEW_FORMAT[];
static const char DEFAULT_PREVIEW_SIZE[];
static const char DEFAULT_FRAMERATE[];
static const char DEFAULT_NUM_PREV_BUFS[];
static const char DEFAULT_PICTURE_FORMAT[];
static const char DEFAULT_PICTURE_SIZE[];
static const char DEFAULT_FOCUS_MODE[];
static const char * DEFAULT_VSTAB;
static const char * DEFAULT_VNF;
static status_t insertDefaults(CameraProperties::Properties*, V4L_TI_CAPTYPE&);
static status_t insertCapabilities(CameraProperties::Properties*, V4L_TI_CAPTYPE&);
static status_t insertPreviewFormats(CameraProperties::Properties* , V4L_TI_CAPTYPE&);
static status_t insertPreviewSizes(CameraProperties::Properties* , V4L_TI_CAPTYPE&);
static status_t insertImageSizes(CameraProperties::Properties* , V4L_TI_CAPTYPE&);
static status_t insertFrameRates(CameraProperties::Properties* , V4L_TI_CAPTYPE&);
static status_t sortAscend(V4L_TI_CAPTYPE&, uint16_t ) ;
status_t v4lIoctl(int, int, void*);
status_t v4lInitMmap(int&);
status_t v4lInitUsrPtr(int&);
status_t v4lStartStreaming();
status_t v4lStopStreaming(int nBufferCount);
status_t v4lSetFormat(int, int, uint32_t);
status_t restartPreview();
int mPreviewBufferCount;
int mPreviewBufferCountQueueable;
int mCaptureBufferCount;
int mCaptureBufferCountQueueable;
KeyedVector<CameraBuffer *, int> mPreviewBufs;
KeyedVector<CameraBuffer *, int> mCaptureBufs;
mutable Mutex mPreviewBufsLock;
mutable Mutex mCaptureBufsLock;
mutable Mutex mStopPreviewLock;
CameraParameters mParams;
bool mPreviewing;
bool mCapturing;
Mutex mLock;
int mFrameCount;
int mLastFrameCount;
unsigned int mIter;
nsecs_t mLastFPSTime;
//variables holding the estimated framerate
float mFPS, mLastFPS;
int mSensorIndex;
// protected by mLoc
大家看到了V4LCameraAdapter 又继承了BaseCameraAdapter，双层继承，实现了父类的一些方法 所有这里算是媳妇熬着婆了，终于找到了我们想要的startPreview 不过看到终于进入了V4LCameraAdapter 这个类，我知道，离成功已经很近了，V4L2就是直接去和driver谈判的 那么我们就看看V4LCameraAdapter 这个类中的startPreview方法吧，路径：ardware/ti/omap4xxx/camera/V4LCameraAdapter/V4LCameraAdapter.cpp
status_t V4LCameraAdapter::startPreview()
{
status_t ret = NO_ERROR;
LOG_FUNCTION_NAME;
Mutex::Autolock lock(mPreviewBufsLock);
if(mPreviewing) {
ret = BAD_VALUE;
goto EXIT;
}
for (int i = 0; i < mPreviewBufferCountQueueable; i++) {
mVideoInfo->buf.index = i;
mVideoInfo->buf.type = V4L2_BUF_TYPE_VIDEO_CAPTURE;
mVideoInfo->buf.memory = V4L2_MEMORY_MMAP;
ret = v4lIoctl(mCameraHandle, VIDIOC_QBUF, &mVideoInfo->buf);
if (ret < 0) {
CAMHAL_LOGEA("VIDIOC_QBUF Failed");
goto EXIT;
}
nQueued++;
}
ret = v4lStartStreaming();
// Create and start preview thread for receiving buffers from V4L Camera
if(!mCapturing) {
mPreviewThread = new PreviewThread(this);
CAMHAL_LOGDA("Created preview thread");
}
不错，这条语句就是我一直找寻的，真是众里寻他千百度，蓦然回首，那句就在灯火阑珊处 这样，其他的事情就全部由v4l2去做了，这些过程会单独分一章去学习 还有就是上面绿的部分，同样要分一章学习，很重要
待续。。。。。。。。。。。