本来想用这一篇博客把cameraHAL的实现和流程都给写完的.搞了半天,东西实在是太多了.这篇先写cameraHAL的基本实现框架,下一篇在具体写camerahal的流程吧.

cameraHAL的实现:

对于初学者来说,最大的疑问是系统是如何调用hardware的.

这里就以camera来举例说明.

调用hardware的程序是cameraservice,我们就去它里面看看它是如何找到hardware的

先把源码贴上来:

/***** Copyright (C) 2008, The Android Open Source Project**** Licensed under the Apache License, Version 2.0 (the "License");** you may not use this file except in compliance with the License.** You may obtain a copy of the License at****     http://www.apache.org/licenses/LICENSE-2.0**** Unless required by applicable law or agreed to in writing, software** distributed under the License is distributed on an "AS IS" BASIS,** WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.** See the License for the specific language governing permissions and** limitations under the License.*/#define LOG_TAG "CameraService"//#define LOG_NDEBUG 0#include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          #include 
          
           #include 
           
            #include 
            
             #include 
             
              #include 
              
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                #include 
                
                 #include 
                 
                  #include 
                  
                   #include 
                   
                    #include 
                    
                     #include 
                     
                      #include "CameraService.h"#include "CameraHardwareInterface.h"namespace android {// ----------------------------------------------------------------------------// Logging support -- this is for debugging only// Use "adb shell dumpsys media.camera -v 1" to change it.static volatile int32_t gLogLevel = 0;#define LOG1(...) LOGD_IF(gLogLevel >= 1, __VA_ARGS__);#define LOG2(...) LOGD_IF(gLogLevel >= 2, __VA_ARGS__);static void setLogLevel(int level) { android_atomic_write(level, &gLogLevel);}// ----------------------------------------------------------------------------static int getCallingPid() { return IPCThreadState::self()->getCallingPid();}static int getCallingUid() { return IPCThreadState::self()->getCallingUid();}// ----------------------------------------------------------------------------// This is ugly and only safe if we never re-create the CameraService, but// should be ok for now.static CameraService *gCameraService;CameraService::CameraService():mSoundRef(0), mModule(0){ LOGI("CameraService started (pid=%d)", getpid()); gCameraService = this;}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); } } // Read the system property to determine if we have to use the // AUDIO_STREAM_ENFORCED_AUDIBLE type. char value[PROPERTY_VALUE_MAX]; property_get("ro.camera.sound.forced", value, "0"); if (strcmp(value, "0") != 0) { mAudioStreamType = AUDIO_STREAM_ENFORCED_AUDIBLE; } else { mAudioStreamType = AUDIO_STREAM_MUSIC; }}CameraService::~CameraService() { for (int i = 0; i < mNumberOfCameras; i++) { if (mBusy[i]) { LOGE("camera %d is still in use in destructor!", i); } } gCameraService = NULL;}int32_t CameraService::getNumberOfCameras() { return mNumberOfCameras;}status_t CameraService::getCameraInfo(int cameraId, struct CameraInfo* cameraInfo) { if (!mModule) { return NO_INIT; } if (cameraId < 0 || cameraId >= mNumberOfCameras) { return BAD_VALUE; } struct camera_info info; status_t rc = mModule->get_camera_info(cameraId, &info); cameraInfo->facing = info.facing; cameraInfo->orientation = info.orientation; return rc;}sp
                      
                        CameraService::connect( const sp
                       
                        & cameraClient, int cameraId) { int callingPid = getCallingPid(); sp
                        
                          hardware = NULL; LOG1("CameraService::connect E (pid %d, id %d)", callingPid, cameraId); if (!mModule) { LOGE("Camera HAL module not loaded"); return NULL; } sp
                         
                           client; if (cameraId < 0 || cameraId >= mNumberOfCameras) { LOGE("CameraService::connect X (pid %d) rejected (invalid cameraId %d).", callingPid, cameraId); return NULL; } char value[PROPERTY_VALUE_MAX]; property_get("sys.secpolicy.camera.disabled", value, "0"); if (strcmp(value, "1") == 0) { // Camera is disabled by DevicePolicyManager. LOGI("Camera is disabled. connect X (pid %d) rejected", callingPid); return NULL; } Mutex::Autolock lock(mServiceLock); if (mClient[cameraId] != 0) { client = mClient[cameraId].promote(); if (client != 0) { if (cameraClient->asBinder() == client->getCameraClient()->asBinder()) { LOG1("CameraService::connect X (pid %d) (the same client)", callingPid); return client; } else { LOGW("CameraService::connect X (pid %d) rejected (existing client).", callingPid); return NULL; } } mClient[cameraId].clear(); } if (mBusy[cameraId]) { LOGW("CameraService::connect X (pid %d) rejected" " (camera %d is still busy).", callingPid, cameraId); return NULL; } struct camera_info info; if (mModule->get_camera_info(cameraId, &info) != OK) { LOGE("Invalid camera id %d", cameraId); return NULL; } char camera_device_name[10]; snprintf(camera_device_name, sizeof(camera_device_name), "%d", cameraId); hardware = new CameraHardwareInterface(camera_device_name); if (hardware->initialize(&mModule->common) != OK) { hardware.clear(); return NULL; } client = new Client(this, cameraClient, hardware, cameraId, info.facing, callingPid); mClient[cameraId] = client; LOG1("CameraService::connect X"); return client;}void CameraService::removeClient(const sp
                          
                           & cameraClient) { int callingPid = getCallingPid(); LOG1("CameraService::removeClient E (pid %d)", callingPid); for (int i = 0; i < mNumberOfCameras; i++) { // Declare this before the lock to make absolutely sure the // destructor won't be called with the lock held. sp
                           
                             client; Mutex::Autolock lock(mServiceLock); // This happens when we have already disconnected (or this is // just another unused camera). if (mClient[i] == 0) continue; // Promote mClient. It can fail if we are called from this path: // Client::~Client() -> disconnect() -> removeClient(). client = mClient[i].promote(); if (client == 0) { mClient[i].clear(); continue; } if (cameraClient->asBinder() == client->getCameraClient()->asBinder()) { // Found our camera, clear and leave. LOG1("removeClient: clear camera %d", i); mClient[i].clear(); break; } } LOG1("CameraService::removeClient X (pid %d)", callingPid);}sp
                            
                              CameraService::getClientById(int cameraId) { if (cameraId < 0 || cameraId >= mNumberOfCameras) return NULL; return mClient[cameraId].promote();}status_t CameraService::onTransact( uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags) { // Permission checks switch (code) { case BnCameraService::CONNECT: const int pid = getCallingPid(); const int self_pid = getpid(); if (pid != self_pid) { // we're called from a different process, do the real check if (!checkCallingPermission( String16("android.permission.CAMERA"))) { const int uid = getCallingUid(); LOGE("Permission Denial: " "can't use the camera pid=%d, uid=%d", pid, uid); return PERMISSION_DENIED; } } break; } return BnCameraService::onTransact(code, data, reply, flags);}// The reason we need this busy bit is a new CameraService::connect() request// may come in while the previous Client's destructor has not been run or is// still running. If the last strong reference of the previous Client is gone// but the destructor has not been finished, we should not allow the new Client// to be created because we need to wait for the previous Client to tear down// the hardware first.void CameraService::setCameraBusy(int cameraId) { android_atomic_write(1, &mBusy[cameraId]);}void CameraService::setCameraFree(int cameraId) { android_atomic_write(0, &mBusy[cameraId]);}// We share the media players for shutter and recording sound for all clients.// A reference count is kept to determine when we will actually release the// media players.MediaPlayer* CameraService::newMediaPlayer(const char *file) { MediaPlayer* mp = new MediaPlayer(); if (mp->setDataSource(file, NULL) == NO_ERROR) { mp->setAudioStreamType(mAudioStreamType); mp->prepare(); } else { LOGE("Failed to load CameraService sounds: %s", file); return NULL; } return mp;}void CameraService::loadSound() { Mutex::Autolock lock(mSoundLock); LOG1("CameraService::loadSound ref=%d", mSoundRef); if (mSoundRef++) return; mSoundPlayer[SOUND_SHUTTER] = newMediaPlayer("/system/media/audio/ui/camera_click.ogg"); mSoundPlayer[SOUND_RECORDING] = newMediaPlayer("/system/media/audio/ui/VideoRecord.ogg");}void CameraService::releaseSound() { Mutex::Autolock lock(mSoundLock); LOG1("CameraService::releaseSound ref=%d", mSoundRef); if (--mSoundRef) return; for (int i = 0; i < NUM_SOUNDS; i++) { if (mSoundPlayer[i] != 0) { mSoundPlayer[i]->disconnect(); mSoundPlayer[i].clear(); } }}void CameraService::playSound(sound_kind kind) { LOG1("playSound(%d)", kind); Mutex::Autolock lock(mSoundLock); sp
                             
                               player = mSoundPlayer[kind]; if (player != 0) { player->seekTo(0); player->start(); }}// ----------------------------------------------------------------------------CameraService::Client::Client(const sp
                              
                               & cameraService, const sp
                               
                                & cameraClient, const sp
                                
                                 & hardware, int cameraId, int cameraFacing, int clientPid) { int callingPid = getCallingPid(); LOG1("Client::Client E (pid %d)", callingPid); mCameraService = cameraService; mCameraClient = cameraClient; mHardware = hardware; mCameraId = cameraId; mCameraFacing = cameraFacing; mClientPid = clientPid; mMsgEnabled = 0; mSurface = 0; mPreviewWindow = 0; mHardware->setCallbacks(notifyCallback, dataCallback, dataCallbackTimestamp, (void *)cameraId); // Enable zoom, error, focus, and metadata messages by default enableMsgType(CAMERA_MSG_ERROR | CAMERA_MSG_ZOOM | CAMERA_MSG_FOCUS | CAMERA_MSG_PREVIEW_METADATA); // Callback is disabled by default mPreviewCallbackFlag = CAMERA_FRAME_CALLBACK_FLAG_NOOP; mOrientation = getOrientation(0, mCameraFacing == CAMERA_FACING_FRONT); mPlayShutterSound = true; cameraService->setCameraBusy(cameraId); cameraService->loadSound(); LOG1("Client::Client X (pid %d)", callingPid);}// tear down the clientCameraService::Client::~Client() { int callingPid = getCallingPid(); LOG1("Client::~Client E (pid %d, this %p)", callingPid, this); // set mClientPid to let disconnet() tear down the hardware mClientPid = callingPid; disconnect(); mCameraService->releaseSound(); LOG1("Client::~Client X (pid %d, this %p)", callingPid, this);}// ----------------------------------------------------------------------------status_t CameraService::Client::checkPid() const { int callingPid = getCallingPid(); if (callingPid == mClientPid) return NO_ERROR; LOGW("attempt to use a locked camera from a different process" " (old pid %d, new pid %d)", mClientPid, callingPid); return EBUSY;}status_t CameraService::Client::checkPidAndHardware() const { status_t result = checkPid(); if (result != NO_ERROR) return result; if (mHardware == 0) { LOGE("attempt to use a camera after disconnect() (pid %d)", getCallingPid()); return INVALID_OPERATION; } return NO_ERROR;}status_t CameraService::Client::lock() { int callingPid = getCallingPid(); LOG1("lock (pid %d)", callingPid); Mutex::Autolock lock(mLock); // lock camera to this client if the the camera is unlocked if (mClientPid == 0) { mClientPid = callingPid; return NO_ERROR; } // returns NO_ERROR if the client already owns the camera, EBUSY otherwise return checkPid();}status_t CameraService::Client::unlock() { int callingPid = getCallingPid(); LOG1("unlock (pid %d)", callingPid); Mutex::Autolock lock(mLock); // allow anyone to use camera (after they lock the camera) status_t result = checkPid(); if (result == NO_ERROR) { if (mHardware->recordingEnabled()) { LOGE("Not allowed to unlock camera during recording."); return INVALID_OPERATION; } mClientPid = 0; LOG1("clear mCameraClient (pid %d)", callingPid); // we need to remove the reference to ICameraClient so that when the app // goes away, the reference count goes to 0. mCameraClient.clear(); } return result;}// connect a new client to the camerastatus_t CameraService::Client::connect(const sp
                                 
                                  & client) { int callingPid = getCallingPid(); LOG1("connect E (pid %d)", callingPid); Mutex::Autolock lock(mLock); if (mClientPid != 0 && checkPid() != NO_ERROR) { LOGW("Tried to connect to a locked camera (old pid %d, new pid %d)", mClientPid, callingPid); return EBUSY; } if (mCameraClient != 0 && (client->asBinder() == mCameraClient->asBinder())) { LOG1("Connect to the same client"); return NO_ERROR; } mPreviewCallbackFlag = CAMERA_FRAME_CALLBACK_FLAG_NOOP; mClientPid = callingPid; mCameraClient = client; LOG1("connect X (pid %d)", callingPid); return NO_ERROR;}static void disconnectWindow(const sp
                                  
                                   & window) { if (window != 0) { status_t result = native_window_api_disconnect(window.get(), NATIVE_WINDOW_API_CAMERA); if (result != NO_ERROR) { LOGW("native_window_api_disconnect failed: %s (%d)", strerror(-result), result); } }}void CameraService::Client::disconnect() { int callingPid = getCallingPid(); LOG1("disconnect E (pid %d)", callingPid); Mutex::Autolock lock(mLock); if (checkPid() != NO_ERROR) { LOGW("different client - don't disconnect"); return; } if (mClientPid <= 0) { LOG1("camera is unlocked (mClientPid = %d), don't tear down hardware", mClientPid); return; } // Make sure disconnect() is done once and once only, whether it is called // from the user directly, or called by the destructor. if (mHardware == 0) return; LOG1("hardware teardown"); // Before destroying mHardware, we must make sure it's in the // idle state. // Turn off all messages. disableMsgType(CAMERA_MSG_ALL_MSGS); mHardware->stopPreview(); mHardware->cancelPicture(); // Release the hardware resources. mHardware->release(); // Release the held ANativeWindow resources. if (mPreviewWindow != 0) { disconnectWindow(mPreviewWindow); mPreviewWindow = 0; mHardware->setPreviewWindow(mPreviewWindow); } mHardware.clear(); mCameraService->removeClient(mCameraClient); mCameraService->setCameraFree(mCameraId); LOG1("disconnect X (pid %d)", callingPid);}// ----------------------------------------------------------------------------status_t CameraService::Client::setPreviewWindow(const sp
                                   
                                    & binder, const sp
                                    
                                     & window) { Mutex::Autolock lock(mLock); status_t result = checkPidAndHardware(); if (result != NO_ERROR) return result; // return if no change in surface. if (binder == mSurface) { return NO_ERROR; } if (window != 0) { result = native_window_api_connect(window.get(), NATIVE_WINDOW_API_CAMERA); if (result != NO_ERROR) { LOGE("native_window_api_connect failed: %s (%d)", strerror(-result), result); return result; } } // If preview has been already started, register preview buffers now. if (mHardware->previewEnabled()) { if (window != 0) { native_window_set_scaling_mode(window.get(), NATIVE_WINDOW_SCALING_MODE_SCALE_TO_WINDOW); native_window_set_buffers_transform(window.get(), mOrientation); result = mHardware->setPreviewWindow(window); } } if (result == NO_ERROR) { // Everything has succeeded. Disconnect the old window and remember the // new window. disconnectWindow(mPreviewWindow); mSurface = binder; mPreviewWindow = window; } else { // Something went wrong after we connected to the new window, so // disconnect here. disconnectWindow(window); } return result;}// set the Surface that the preview will usestatus_t CameraService::Client::setPreviewDisplay(const sp
                                     
                                      & surface) { LOG1("setPreviewDisplay(%p) (pid %d)", surface.get(), getCallingPid()); sp
                                      
                                        binder(surface != 0 ? surface->asBinder() : 0); sp
                                       
                                         window(surface); return setPreviewWindow(binder, window);}// set the SurfaceTexture that the preview will usestatus_t CameraService::Client::setPreviewTexture( const sp
                                        
                                         & surfaceTexture) { LOG1("setPreviewTexture(%p) (pid %d)", surfaceTexture.get(), getCallingPid()); sp
                                         
                                           binder; sp
                                          
                                            window; if (surfaceTexture != 0) { binder = surfaceTexture->asBinder(); window = new SurfaceTextureClient(surfaceTexture); } return setPreviewWindow(binder, window);}// set the preview callback flag to affect how the received frames from// preview are handled.void CameraService::Client::setPreviewCallbackFlag(int callback_flag) { LOG1("setPreviewCallbackFlag(%d) (pid %d)", callback_flag, getCallingPid()); Mutex::Autolock lock(mLock); if (checkPidAndHardware() != NO_ERROR) return; mPreviewCallbackFlag = callback_flag; if (mPreviewCallbackFlag & CAMERA_FRAME_CALLBACK_FLAG_ENABLE_MASK) { enableMsgType(CAMERA_MSG_PREVIEW_FRAME); } else { disableMsgType(CAMERA_MSG_PREVIEW_FRAME); }}// start preview modestatus_t CameraService::Client::startPreview() { LOG1("startPreview (pid %d)", getCallingPid()); return startCameraMode(CAMERA_PREVIEW_MODE);}// start recording modestatus_t CameraService::Client::startRecording() { LOG1("startRecording (pid %d)", getCallingPid()); return startCameraMode(CAMERA_RECORDING_MODE);}// start preview or recordingstatus_t CameraService::Client::startCameraMode(camera_mode mode) { LOG1("startCameraMode(%d)", mode); Mutex::Autolock lock(mLock); status_t result = checkPidAndHardware(); if (result != NO_ERROR) return result; switch(mode) { case CAMERA_PREVIEW_MODE: if (mSurface == 0 && mPreviewWindow == 0) { LOG1("mSurface is not set yet."); // still able to start preview in this case. } return startPreviewMode(); case CAMERA_RECORDING_MODE: if (mSurface == 0 && mPreviewWindow == 0) { LOGE("mSurface or mPreviewWindow must be set before startRecordingMode."); return INVALID_OPERATION; } return startRecordingMode(); default: return UNKNOWN_ERROR; }}status_t CameraService::Client::startPreviewMode() { LOG1("startPreviewMode"); status_t result = NO_ERROR; // if preview has been enabled, nothing needs to be done if (mHardware->previewEnabled()) { return NO_ERROR; } if (mPreviewWindow != 0) { native_window_set_scaling_mode(mPreviewWindow.get(), NATIVE_WINDOW_SCALING_MODE_SCALE_TO_WINDOW); native_window_set_buffers_transform(mPreviewWindow.get(), mOrientation); } mHardware->setPreviewWindow(mPreviewWindow); result = mHardware->startPreview(); return result;}status_t CameraService::Client::startRecordingMode() { LOG1("startRecordingMode"); status_t result = NO_ERROR; // if recording has been enabled, nothing needs to be done if (mHardware->recordingEnabled()) { return NO_ERROR; } // if preview has not been started, start preview first if (!mHardware->previewEnabled()) { result = startPreviewMode(); if (result != NO_ERROR) { return result; } } // start recording mode enableMsgType(CAMERA_MSG_VIDEO_FRAME); mCameraService->playSound(SOUND_RECORDING); result = mHardware->startRecording(); if (result != NO_ERROR) { LOGE("mHardware->startRecording() failed with status %d", result); } return result;}// stop preview modevoid CameraService::Client::stopPreview() { LOG1("stopPreview (pid %d)", getCallingPid()); Mutex::Autolock lock(mLock); if (checkPidAndHardware() != NO_ERROR) return; disableMsgType(CAMERA_MSG_PREVIEW_FRAME); mHardware->stopPreview(); mPreviewBuffer.clear();}// stop recording modevoid CameraService::Client::stopRecording() { LOG1("stopRecording (pid %d)", getCallingPid()); Mutex::Autolock lock(mLock); if (checkPidAndHardware() != NO_ERROR) return; mCameraService->playSound(SOUND_RECORDING); disableMsgType(CAMERA_MSG_VIDEO_FRAME); mHardware->stopRecording(); mPreviewBuffer.clear();}// release a recording framevoid CameraService::Client::releaseRecordingFrame(const sp
                                           
                                            & mem) { Mutex::Autolock lock(mLock); if (checkPidAndHardware() != NO_ERROR) return; mHardware->releaseRecordingFrame(mem);}status_t CameraService::Client::storeMetaDataInBuffers(bool enabled){ LOG1("storeMetaDataInBuffers: %s", enabled? "true": "false"); Mutex::Autolock lock(mLock); if (checkPidAndHardware() != NO_ERROR) { return UNKNOWN_ERROR; } return mHardware->storeMetaDataInBuffers(enabled);}bool CameraService::Client::previewEnabled() { LOG1("previewEnabled (pid %d)", getCallingPid()); Mutex::Autolock lock(mLock); if (checkPidAndHardware() != NO_ERROR) return false; return mHardware->previewEnabled();}bool CameraService::Client::recordingEnabled() { LOG1("recordingEnabled (pid %d)", getCallingPid()); Mutex::Autolock lock(mLock); if (checkPidAndHardware() != NO_ERROR) return false; return mHardware->recordingEnabled();}status_t CameraService::Client::autoFocus() { LOG1("autoFocus (pid %d)", getCallingPid()); Mutex::Autolock lock(mLock); status_t result = checkPidAndHardware(); if (result != NO_ERROR) return result; return mHardware->autoFocus();}status_t CameraService::Client::cancelAutoFocus() { LOG1("cancelAutoFocus (pid %d)", getCallingPid()); Mutex::Autolock lock(mLock); status_t result = checkPidAndHardware(); if (result != NO_ERROR) return result; return mHardware->cancelAutoFocus();}// take a picture - image is returned in callbackstatus_t CameraService::Client::takePicture(int msgType) { LOG1("takePicture (pid %d): 0x%x", getCallingPid(), msgType); Mutex::Autolock lock(mLock); status_t result = checkPidAndHardware(); if (result != NO_ERROR) return result; if ((msgType & CAMERA_MSG_RAW_IMAGE) && (msgType & CAMERA_MSG_RAW_IMAGE_NOTIFY)) { LOGE("CAMERA_MSG_RAW_IMAGE and CAMERA_MSG_RAW_IMAGE_NOTIFY" " cannot be both enabled"); return BAD_VALUE; } // We only accept picture related message types // and ignore other types of messages for takePicture(). int picMsgType = msgType & (CAMERA_MSG_SHUTTER | CAMERA_MSG_POSTVIEW_FRAME | CAMERA_MSG_RAW_IMAGE | CAMERA_MSG_RAW_IMAGE_NOTIFY | CAMERA_MSG_COMPRESSED_IMAGE); enableMsgType(picMsgType); return mHardware->takePicture();}// set preview/capture parameters - key/value pairsstatus_t CameraService::Client::setParameters(const String8& params) { LOG1("setParameters (pid %d) (%s)", getCallingPid(), params.string()); Mutex::Autolock lock(mLock); status_t result = checkPidAndHardware(); if (result != NO_ERROR) return result; CameraParameters p(params); return mHardware->setParameters(p);}// get preview/capture parameters - key/value pairsString8 CameraService::Client::getParameters() const { Mutex::Autolock lock(mLock); if (checkPidAndHardware() != NO_ERROR) return String8(); String8 params(mHardware->getParameters().flatten()); LOG1("getParameters (pid %d) (%s)", getCallingPid(), params.string()); return params;}// enable shutter soundstatus_t CameraService::Client::enableShutterSound(bool enable) { LOG1("enableShutterSound (pid %d)", getCallingPid()); status_t result = checkPidAndHardware(); if (result != NO_ERROR) return result; if (enable) { mPlayShutterSound = true; return OK; } // Disabling shutter sound may not be allowed. In that case only // allow the mediaserver process to disable the sound. char value[PROPERTY_VALUE_MAX]; property_get("ro.camera.sound.forced", value, "0"); if (strcmp(value, "0") != 0) { // Disabling shutter sound is not allowed. Deny if the current // process is not mediaserver. if (getCallingPid() != getpid()) { LOGE("Failed to disable shutter sound. Permission denied (pid %d)", getCallingPid()); return PERMISSION_DENIED; } } mPlayShutterSound = false; return OK;}status_t CameraService::Client::sendCommand(int32_t cmd, int32_t arg1, int32_t arg2) { LOG1("sendCommand (pid %d)", getCallingPid()); int orientation; Mutex::Autolock lock(mLock); status_t result = checkPidAndHardware(); if (result != NO_ERROR) return result; if (cmd == CAMERA_CMD_SET_DISPLAY_ORIENTATION) { // Mirror the preview if the camera is front-facing. orientation = getOrientation(arg1, mCameraFacing == CAMERA_FACING_FRONT); if (orientation == -1) return BAD_VALUE; if (mOrientation != orientation) { mOrientation = orientation; if (mPreviewWindow != 0) { native_window_set_buffers_transform(mPreviewWindow.get(), mOrientation); } } return OK; } else if (cmd == CAMERA_CMD_ENABLE_SHUTTER_SOUND) { switch (arg1) { case 0: enableShutterSound(false); break; case 1: enableShutterSound(true); break; default: return BAD_VALUE; } return OK; } else if (cmd == CAMERA_CMD_PLAY_RECORDING_SOUND) { mCameraService->playSound(SOUND_RECORDING); } return mHardware->sendCommand(cmd, arg1, arg2);}// ----------------------------------------------------------------------------void CameraService::Client::enableMsgType(int32_t msgType) { android_atomic_or(msgType, &mMsgEnabled); mHardware->enableMsgType(msgType);}void CameraService::Client::disableMsgType(int32_t msgType) { android_atomic_and(~msgType, &mMsgEnabled); mHardware->disableMsgType(msgType);}#define CHECK_MESSAGE_INTERVAL 10 // 10msbool CameraService::Client::lockIfMessageWanted(int32_t msgType) { int sleepCount = 0; while (mMsgEnabled & msgType) { if (mLock.tryLock() == NO_ERROR) { if (sleepCount > 0) { LOG1("lockIfMessageWanted(%d): waited for %d ms", msgType, sleepCount * CHECK_MESSAGE_INTERVAL); } return true; } if (sleepCount++ == 0) { LOG1("lockIfMessageWanted(%d): enter sleep", msgType); } usleep(CHECK_MESSAGE_INTERVAL * 1000); } LOGW("lockIfMessageWanted(%d): dropped unwanted message", msgType); return false;}// ----------------------------------------------------------------------------// Converts from a raw pointer to the client to a strong pointer during a// hardware callback. This requires the callbacks only happen when the client// is still alive.sp
                                            
                                              CameraService::Client::getClientFromCookie(void* user) { sp
                                             
                                               client = gCameraService->getClientById((int) user); // This could happen if the Client is in the process of shutting down (the // last strong reference is gone, but the destructor hasn't finished // stopping the hardware). if (client == 0) return NULL; // The checks below are not necessary and are for debugging only. if (client->mCameraService.get() != gCameraService) { LOGE("mismatch service!"); return NULL; } if (client->mHardware == 0) { LOGE("mHardware == 0: callback after disconnect()?"); return NULL; } return client;}// Callback messages can be dispatched to internal handlers or pass to our// client's callback functions, depending on the message type.//// notifyCallback:// CAMERA_MSG_SHUTTER handleShutter// (others) c->notifyCallback// dataCallback:// CAMERA_MSG_PREVIEW_FRAME handlePreviewData// CAMERA_MSG_POSTVIEW_FRAME handlePostview// CAMERA_MSG_RAW_IMAGE handleRawPicture// CAMERA_MSG_COMPRESSED_IMAGE handleCompressedPicture// (others) c->dataCallback// dataCallbackTimestamp// (others) c->dataCallbackTimestamp//// NOTE: the *Callback functions grab mLock of the client before passing// control to handle* functions. So the handle* functions must release the// lock before calling the ICameraClient's callbacks, so those callbacks can// invoke methods in the Client class again (For example, the preview frame// callback may want to releaseRecordingFrame). The handle* functions must// release the lock after all accesses to member variables, so it must be// handled very carefully.void CameraService::Client::notifyCallback(int32_t msgType, int32_t ext1, int32_t ext2, void* user) { LOG2("notifyCallback(%d)", msgType); sp
                                              
                                                client = getClientFromCookie(user); if (client == 0) return; if (!client->lockIfMessageWanted(msgType)) return; switch (msgType) { case CAMERA_MSG_SHUTTER: // ext1 is the dimension of the yuv picture. client->handleShutter(); break; default: client->handleGenericNotify(msgType, ext1, ext2); break; }}void CameraService::Client::dataCallback(int32_t msgType, const sp
                                               
                                                & dataPtr, camera_frame_metadata_t *metadata, void* user) { LOG2("dataCallback(%d)", msgType); sp
                                                
                                                  client = getClientFromCookie(user); if (client == 0) return; if (!client->lockIfMessageWanted(msgType)) return; if (dataPtr == 0 && metadata == NULL) { LOGE("Null data returned in data callback"); client->handleGenericNotify(CAMERA_MSG_ERROR, UNKNOWN_ERROR, 0); return; } switch (msgType & ~CAMERA_MSG_PREVIEW_METADATA) { case CAMERA_MSG_PREVIEW_FRAME: client->handlePreviewData(msgType, dataPtr, metadata); break; case CAMERA_MSG_POSTVIEW_FRAME: client->handlePostview(dataPtr); break; case CAMERA_MSG_RAW_IMAGE: client->handleRawPicture(dataPtr); break; case CAMERA_MSG_COMPRESSED_IMAGE: client->handleCompressedPicture(dataPtr); break; default: client->handleGenericData(msgType, dataPtr, metadata); break; }}void CameraService::Client::dataCallbackTimestamp(nsecs_t timestamp, int32_t msgType, const sp
                                                 
                                                  & dataPtr, void* user) { LOG2("dataCallbackTimestamp(%d)", msgType); sp
                                                  
                                                    client = getClientFromCookie(user); if (client == 0) return; if (!client->lockIfMessageWanted(msgType)) return; if (dataPtr == 0) { LOGE("Null data returned in data with timestamp callback"); client->handleGenericNotify(CAMERA_MSG_ERROR, UNKNOWN_ERROR, 0); return; } client->handleGenericDataTimestamp(timestamp, msgType, dataPtr);}// snapshot taken callbackvoid CameraService::Client::handleShutter(void) { if (mPlayShutterSound) { mCameraService->playSound(SOUND_SHUTTER); } sp
                                                   
                                                     c = mCameraClient; if (c != 0) { mLock.unlock(); c->notifyCallback(CAMERA_MSG_SHUTTER, 0, 0); if (!lockIfMessageWanted(CAMERA_MSG_SHUTTER)) return; } disableMsgType(CAMERA_MSG_SHUTTER); mLock.unlock();}// preview callback - frame buffer updatevoid CameraService::Client::handlePreviewData(int32_t msgType, const sp
                                                    
                                                     & mem, camera_frame_metadata_t *metadata) { ssize_t offset; size_t size; sp
                                                     
                                                       heap = mem->getMemory(&offset, &size); // local copy of the callback flags int flags = mPreviewCallbackFlag; // is callback enabled? if (!(flags & CAMERA_FRAME_CALLBACK_FLAG_ENABLE_MASK)) { // If the enable bit is off, the copy-out and one-shot bits are ignored LOG2("frame callback is disabled"); mLock.unlock(); return; } // hold a strong pointer to the client sp
                                                      
                                                        c = mCameraClient; // clear callback flags if no client or one-shot mode if (c == 0 || (mPreviewCallbackFlag & CAMERA_FRAME_CALLBACK_FLAG_ONE_SHOT_MASK)) { LOG2("Disable preview callback"); mPreviewCallbackFlag &= ~(CAMERA_FRAME_CALLBACK_FLAG_ONE_SHOT_MASK | CAMERA_FRAME_CALLBACK_FLAG_COPY_OUT_MASK | CAMERA_FRAME_CALLBACK_FLAG_ENABLE_MASK); disableMsgType(CAMERA_MSG_PREVIEW_FRAME); } if (c != 0) { // Is the received frame copied out or not? if (flags & CAMERA_FRAME_CALLBACK_FLAG_COPY_OUT_MASK) { LOG2("frame is copied"); copyFrameAndPostCopiedFrame(msgType, c, heap, offset, size, metadata); } else { LOG2("frame is forwarded"); mLock.unlock(); c->dataCallback(msgType, mem, metadata); } } else { mLock.unlock(); }}// picture callback - postview image readyvoid CameraService::Client::handlePostview(const sp
                                                       
                                                        & mem) { disableMsgType(CAMERA_MSG_POSTVIEW_FRAME); sp
                                                        
                                                          c = mCameraClient; mLock.unlock(); if (c != 0) { c->dataCallback(CAMERA_MSG_POSTVIEW_FRAME, mem, NULL); }}// picture callback - raw image readyvoid CameraService::Client::handleRawPicture(const sp
                                                         
                                                          & mem) { disableMsgType(CAMERA_MSG_RAW_IMAGE); ssize_t offset; size_t size; sp
                                                          
                                                            heap = mem->getMemory(&offset, &size); sp
                                                           
                                                             c = mCameraClient; mLock.unlock(); if (c != 0) { c->dataCallback(CAMERA_MSG_RAW_IMAGE, mem, NULL); }}// picture callback - compressed picture readyvoid CameraService::Client::handleCompressedPicture(const sp
                                                            
                                                             & mem) { disableMsgType(CAMERA_MSG_COMPRESSED_IMAGE); sp
                                                             
                                                               c = mCameraClient; mLock.unlock(); if (c != 0) { c->dataCallback(CAMERA_MSG_COMPRESSED_IMAGE, mem, NULL); }}void CameraService::Client::handleGenericNotify(int32_t msgType, int32_t ext1, int32_t ext2) { sp
                                                              
                                                                c = mCameraClient; mLock.unlock(); if (c != 0) { c->notifyCallback(msgType, ext1, ext2); }}void CameraService::Client::handleGenericData(int32_t msgType, const sp
                                                               
                                                                & dataPtr, camera_frame_metadata_t *metadata) { sp
                                                                
                                                                  c = mCameraClient; mLock.unlock(); if (c != 0) { c->dataCallback(msgType, dataPtr, metadata); }}void CameraService::Client::handleGenericDataTimestamp(nsecs_t timestamp, int32_t msgType, const sp
                                                                 
                                                                  & dataPtr) { sp
                                                                  
                                                                    c = mCameraClient; mLock.unlock(); if (c != 0) { c->dataCallbackTimestamp(timestamp, msgType, dataPtr); }}void CameraService::Client::copyFrameAndPostCopiedFrame( int32_t msgType, const sp
                                                                   
                                                                    & client, const sp
                                                                    
                                                                     & heap, size_t offset, size_t size, camera_frame_metadata_t *metadata) { LOG2("copyFrameAndPostCopiedFrame"); // It is necessary to copy out of pmem before sending this to // the callback. For efficiency, reuse the same MemoryHeapBase // provided it's big enough. Don't allocate the memory or // perform the copy if there's no callback. // hold the preview lock while we grab a reference to the preview buffer sp
                                                                     
                                                                       previewBuffer; if (mPreviewBuffer == 0) { mPreviewBuffer = new MemoryHeapBase(size, 0, NULL); } else if (size > mPreviewBuffer->virtualSize()) { mPreviewBuffer.clear(); mPreviewBuffer = new MemoryHeapBase(size, 0, NULL); } if (mPreviewBuffer == 0) { LOGE("failed to allocate space for preview buffer"); mLock.unlock(); return; } previewBuffer = mPreviewBuffer; memcpy(previewBuffer->base(), (uint8_t *)heap->base() + offset, size); sp
                                                                      
                                                                        frame = new MemoryBase(previewBuffer, 0, size); if (frame == 0) { LOGE("failed to allocate space for frame callback"); mLock.unlock(); return; } mLock.unlock(); client->dataCallback(msgType, frame, metadata);}int CameraService::Client::getOrientation(int degrees, bool mirror) { if (!mirror) { if (degrees == 0) return 0; else if (degrees == 90) return HAL_TRANSFORM_ROT_90; else if (degrees == 180) return HAL_TRANSFORM_ROT_180; else if (degrees == 270) return HAL_TRANSFORM_ROT_270; } else { // Do mirror (horizontal flip) if (degrees == 0) { // FLIP_H and ROT_0 return HAL_TRANSFORM_FLIP_H; } else if (degrees == 90) { // FLIP_H and ROT_90 return HAL_TRANSFORM_FLIP_H | HAL_TRANSFORM_ROT_90; } else if (degrees == 180) { // FLIP_H and ROT_180 return HAL_TRANSFORM_FLIP_V; } else if (degrees == 270) { // FLIP_H and ROT_270 return HAL_TRANSFORM_FLIP_V | HAL_TRANSFORM_ROT_90; } } LOGE("Invalid setDisplayOrientation degrees=%d", degrees); return -1;}// ----------------------------------------------------------------------------static const int kDumpLockRetries = 50;static const int kDumpLockSleep = 60000;static bool tryLock(Mutex& mutex){ bool locked = false; for (int i = 0; i < kDumpLockRetries; ++i) { if (mutex.tryLock() == NO_ERROR) { locked = true; break; } usleep(kDumpLockSleep); } return locked;}status_t CameraService::dump(int fd, const Vector
                                                                       
                                                                        & args) { static const char* kDeadlockedString = "CameraService may be deadlocked\n"; const size_t SIZE = 256; char buffer[SIZE]; String8 result; if (checkCallingPermission(String16("android.permission.DUMP")) == false) { snprintf(buffer, SIZE, "Permission Denial: " "can't dump CameraService from pid=%d, uid=%d\n", getCallingPid(), getCallingUid()); result.append(buffer); write(fd, result.string(), result.size()); } else { bool locked = tryLock(mServiceLock); // failed to lock - CameraService is probably deadlocked if (!locked) { String8 result(kDeadlockedString); write(fd, result.string(), result.size()); } bool hasClient = false; for (int i = 0; i < mNumberOfCameras; i++) { sp
                                                                        
                                                                          client = mClient[i].promote(); if (client == 0) continue; hasClient = true; sprintf(buffer, "Client[%d] (%p) PID: %d\n", i, client->getCameraClient()->asBinder().get(), client->mClientPid); result.append(buffer); write(fd, result.string(), result.size()); client->mHardware->dump(fd, args); } if (!hasClient) { result.append("No camera client yet.\n"); write(fd, result.string(), result.size()); } if (locked) mServiceLock.unlock(); // change logging level int n = args.size(); for (int i = 0; i + 1 < n; i++) { if (args[i] == String16("-v")) { String8 levelStr(args[i+1]); int level = atoi(levelStr.string()); sprintf(buffer, "Set Log Level to %d", level); result.append(buffer); setLogLevel(level); } } } return NO_ERROR;}}; // namespace android
                                                                        
                                                                       
                                                                      
                                                                     
                                                                    
                                                                   
                                                                  
                                                                 
                                                                
                                                               
                                                              
                                                             
                                                            
                                                           
                                                          
                                                         
                                                        
                                                       
                                                      
                                                     
                                                    
                                                   
                                                  
                                                 
                                                
                                               
                                              
                                             
                                            
                                           
                                          
                                         
                                        
                                       
                                      
                                     
                                    
                                   
                                  
                                 
                                
                               
                              
                             
                            
                           
                          
                         
                        
                       
                      
                     
                    
                   
                  
                 
                
               
              
             
            
           
          
         
        
       
      
     

 

 

void CameraService::onFirstRef()看这个函数:

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();            //获取camera设备的个数.对应下文中的获取camera个数函数.        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);        }        }        // Read the system property to determine if we have to use the    // AUDIO_STREAM_ENFORCED_AUDIBLE type.    char value[PROPERTY_VALUE_MAX];    property_get("ro.camera.sound.forced", value, "0");    if (strcmp(value, "0") != 0) {         mAudioStreamType = AUDIO_STREAM_ENFORCED_AUDIBLE;    } else {        mAudioStreamType = AUDIO_STREAM_MUSIC;    }    }

 

 

找了半天也就是它这个函数里边有hw_get_module()这个函数,一看名字就知道是获取hardware的,不找它找谁啊。那么onFirstRef()函数又是何时调用的？

onFirstRef（）属于其父类RefBase，该函数在强引用sp新增引用计数时调用，什么意思？就是当 有sp包装的类初始化的时候调用。这里在frameworks/base/services/camera/libcameraservice/CameraService.h 中class CameraService :中有定义

// these are initialized in the constructor.        sp
     
                     mCameraService;  // immutable after constructor        sp
      
                      mCameraClient;        int                             mCameraId;       // immutable after constructor        int                             mCameraFacing;   // immutable after constructor        pid_t                           mClientPid;        sp
       
             mHardware;       // cleared after disconnect()        int                             mPreviewCallbackFlag;        int                             mOrientation;     // Current display orientation        bool                            mPlayShutterSound;
       
      
     

 

很明显是这里来初始化的,当然这里不是重点,如果全部都写的话,那基本上就写不完了.

找到了hw_get_module()这个函数,让我们看它的具体实现.

hardware/libhardware/hardware.c

代码如下:

/* * Copyright (C) 2008 The Android Open Source Project * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * *      http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */#include 
     
      #include 
      
       #include 
       
        #include 
        
         #include 
         
          #include 
          
           #include 
           
            #define LOG_TAG "HAL"#include 
            
             /** Base path of the hal modules */#define HAL_LIBRARY_PATH1 "/system/lib/hw"#define HAL_LIBRARY_PATH2 "/vendor/lib/hw"/** * There are a set of variant filename for modules. The form of the filename * is "
             
              .variant.so" so for the led module the Dream variants * of base "ro.product.board", "ro.board.platform" and "ro.arch" would be: * * led.trout.so * led.msm7k.so * led.ARMV6.so * led.default.so */static const char *variant_keys[] = { "ro.hardware", /* This goes first so that it can pick up a different file on the emulator. */ "ro.product.board", "ro.board.platform", "ro.arch"};static const int HAL_VARIANT_KEYS_COUNT = (sizeof(variant_keys)/sizeof(variant_keys[0]));/** * Load the file defined by the variant and if successful * return the dlopen handle and the hmi. * @return 0 = success, !0 = failure. */static int load(const char *id, const char *path, const struct hw_module_t **pHmi){ int status; void *handle; struct hw_module_t *hmi; /* * load the symbols resolving undefined symbols before * dlopen returns. Since RTLD_GLOBAL is not or'd in with * RTLD_NOW the external symbols will not be global */ handle = dlopen(path, RTLD_NOW); if (handle == NULL) { char const *err_str = dlerror(); LOGE("load: module=%s\n%s", path, err_str?err_str:"unknown"); status = -EINVAL; goto done; } /* Get the address of the struct hal_module_info. */ const char *sym = HAL_MODULE_INFO_SYM_AS_STR; hmi = (struct hw_module_t *)dlsym(handle, sym); if (hmi == NULL) { LOGE("load: couldn't find symbol %s", sym); status = -EINVAL; goto done; } /* Check that the id matches */ if (strcmp(id, hmi->id) != 0) { LOGE("load: id=%s != hmi->id=%s", id, hmi->id); status = -EINVAL; goto done; } hmi->dso = handle; /* success */ status = 0; done: if (status != 0) { hmi = NULL; if (handle != NULL) { dlclose(handle); handle = NULL; } } else { LOGV("loaded HAL id=%s path=%s hmi=%p handle=%p", id, path, *pHmi, handle); } *pHmi = hmi; return status;}int hw_get_module_by_class(const char *class_id, const char *inst, const struct hw_module_t **module){ int status; int i; const struct hw_module_t *hmi = NULL; char prop[PATH_MAX]; char path[PATH_MAX]; char name[PATH_MAX]; if (inst) snprintf(name, PATH_MAX, "%s.%s", class_id, inst); else strlcpy(name, class_id, PATH_MAX); /* * Here we rely on the fact that calling dlopen multiple times on * the same .so will simply increment a refcount (and not load * a new copy of the library). * We also assume that dlopen() is thread-safe. */ /* Loop through the configuration variants looking for a module */ for (i=0 ; i
             
            
           
          
         
        
       
      
     

让我们看看它的流程:

int hw_get_module(const char *id, const struct hw_module_t **module)    int hw_get_module_by_class(const char *class_id, const char *inst,const struct hw_module_t **module)        static int load(const char *id,const char *path,const struct hw_module_t **pHmi)                /* Check that the id matches */                if (strcmp(id, hmi->id) != 0) {                    LOGE("load: id=%s != hmi->id=%s", id, hmi->id);                    status = -EINVAL;                    goto done;                }                ...

可以知道,真正来寻找hardware的桥梁是这个ID,在if (strcmp(id, hmi->id) != 0)中,id是frameworks/base/services/camera/libcameraservice/CameraService.cpp中直接赋值的

如下:

if (hw_get_module(CAMERA_HARDWARE_MODULE_ID,                (const hw_module_t **)&mModule) < 0) {        LOGE("Could not load camera HAL module");        mNumberOfCameras = 0;    }

 

而hmi->id中的这个id很明显是hardware中应该定义的了.

我们看hmi是怎么得来的.

/* Get the address of the struct hal_module_info. */    const char *sym = HAL_MODULE_INFO_SYM_AS_STR;    hmi = (struct hw_module_t *)dlsym(handle, sym);

 

不用跟踪这个函数就能看出来.hmi一定是从sym中来获取的.所以这里我们也就知道hardware中一定要有这个结构体.这也是实现一个hardware必须要做的事情,这里在hardware.h中也有说明:

/** * Every hardware module must have a data structure named HAL_MODULE_INFO_SYM * and the fields of this data structure must begin with hw_module_t * followed by module specific information. */

 

 

即hardware中一定要有这个叫HAL_MODULE_INFO_SYM的结构体.这也是实现一个hardware的第一步:Step-1:实现一个名字为HAL_MODULE_INFO_SYM的结构体,这个结构体必须以hw_module_t开头

好吧,来看一下camera的hardware中是怎么定义的.

看一下common是不是结构体hw_module_t

hardware/libhardware/include/hardware/camera.h

好了,既然hardware要有结构体,那么必须要给他初始化.自定义的函数也得给实现了.

上文注释已经写出来了.这里只是粘贴一下函数的实现.

所以也就自然而然的调用到了实现hardware的第二步,Step-2:

open函数的实现及作用.还是看cameraHAL中对其的实现.

层层包装啊,再看HAL_camera_device_open:

static int HAL_camera_device_open(const struct hw_module_t* module,                                  const char *id,                                  struct hw_device_t** device){    int cameraId = atoi(id);    if (cameraId < 0 || cameraId >= HAL_getNumberOfCameras()) {        return -EINVAL;    }    if (g_cam_device) {                                //如果系统第二次打开摄像头,则此时g_cam_device已经填充完毕,可以不再填充了.        if (obj(g_cam_device)->getCameraId() == cameraId) {            goto done;        } else {            LOGE("Cannot open camera %d. camera %d is already running!",                    cameraId, obj(g_cam_device)->getCameraId());            return -ENOSYS;        }    }    g_cam_device = (camera_device_t *)malloc(sizeof(camera_device_t));    if (!g_cam_device)        return -ENOMEM;    g_cam_device->common.tag     = HARDWARE_DEVICE_TAG;    g_cam_device->common.version = 1;    g_cam_device->common.module  = const_cast
     
      (module);    g_cam_device->common.close   = HAL_camera_device_close;    g_cam_device->ops = &camera_device_ops;    LOGI("%s: open camera %s", __func__, id);    g_cam_device->priv = new CameraHardwareSec(cameraId, g_cam_device);done:    *device = (hw_device_t *)g_cam_device;    LOGI("%s: opened camera %s (%p)", __func__, id, *device);    return 0;}
     

 

这里我们知道.open的作用就是打开指定ID号的摄像头以及填充device结构体,供上层直接调用我们HAL的具体函数比如takePicture(),startPreview()等等.

但是应该怎么去填充这个结构体呢?

还是先看hardware/libhardware/include/hardware/hardware.h怎么说吧.

/** * Every device data structure must begin with hw_device_t * followed by module specific public methods and attributes. */

 

它说每一个设备都必须以hw_device_t开始,后面跟着methods和attributes.

那我们就在HAL中定义一个static的结构体,按着上边赋值完毕后返回这个指针就成了.看HAL

static camera_device_t *g_cam_device;            //定义设备的结构体具体如下.typedef struct camera_device {                hw_device_t common;                            //以hw_device_t开始    camera_device_ops_t *ops;                    //紧跟着methods    void *priv;                                 //私有数据.} camera_device_t;

看看是怎么填充的:

g_cam_device->common.tag     = HARDWARE_DEVICE_TAG;        //hardware.h中定义的.具体设备tag必须这样定义.g_cam_device->common.module  = const_cast
     
      (module);    //和module模块建立联系g_cam_device->common.close   = HAL_camera_device_close;        //设备关闭的函数g_cam_device->ops = &camera_device_ops;                        // 这个里边包含的就是那些操作摄像头所需要的具体实现.讲HAL的运行流程时细讲.g_cam_device->priv = new CameraHardwareSec(cameraId, g_cam_device);    //真正实现hardware初始化摄像头的函数,讲HAL的运行流程时细讲.
     

这里先看看camera_device_ops的具体实现,也牵扯到了HAL实现的第三步,Step-3:具体设备的函数实现.

#define SET_METHOD(m) m : HAL_camera_device_##m        //相当于m : HAL_camera_device_mstatic camera_device_ops_t camera_device_ops = {        SET_METHOD(set_preview_window),                //展开后相当于set_preview_window : HAL_camera_device_set_preview_window,即HAL_camera_device_set_preview_window是set_preview_window的具体实现        SET_METHOD(set_callbacks),                    //展开后相当于set_callbacks : HAL_camera_device_set_callbacks        SET_METHOD(enable_msg_type),                //同上        SET_METHOD(disable_msg_type),        SET_METHOD(msg_type_enabled),        SET_METHOD(start_preview),        SET_METHOD(stop_preview),        SET_METHOD(preview_enabled),        SET_METHOD(store_meta_data_in_buffers),        SET_METHOD(start_recording),        SET_METHOD(stop_recording),        SET_METHOD(recording_enabled),        SET_METHOD(release_recording_frame),        SET_METHOD(auto_focus),        SET_METHOD(cancel_auto_focus),        SET_METHOD(take_picture),        SET_METHOD(cancel_picture),        SET_METHOD(set_parameters),        SET_METHOD(get_parameters),        SET_METHOD(put_parameters),        SET_METHOD(send_command),        SET_METHOD(release),        SET_METHOD(dump),};

 

先不说HAL中调用函数的具体实现,看看是service怎么调用的.

以start_preview为例.

camera.start_preview()    //应用程序        public native final void startPreview();                                                   //此处调用JNI frameworks/base/core/java/android/hardware/Camera.java            static void android_hardware_Camera_startPreview(JNIEnv *env, jobject thiz)            //JNI frameworks/base/core/jni/android_hardware_Camera.cpp                sp
     
       camera = get_native_camera(env, thiz, NULL);                        //获取cameraClient    frameworks/base/core/jni/android_hardware_Camera.cpp                camera->startPreview();                                                        //执行cameraClient的函数    frameworks/base/libs/camera/Camera.cpp.                    status_t CameraService::Client::startPreview();                            //service中函数的实现    frameworks/base/services/camera/libcameraservice/CameraService.cpp                        status_t CameraService::Client::startCameraMode(camera_mode mode)     //service中的调用    frameworks/base/services/camera/libcameraservice/CameraService.cpp                            status_t CameraService::Client::startPreviewMode()                //service最终调用    frameworks/base/services/camera/libcameraservice/CameraService.cpp                                 status_t startPreview()                                    //调用到hardware的接口    frameworks/base/services/camera/libcameraservice/CameraHardwareInterface.h                                    mDevice->ops->start_preview(mDevice);                    //调用到HAL层的start_preview具体实现HAL_camera_device_start_preview.   device/magiclab/common/libcamera/SecCameraHWInterface_zoom.cpp
     

 

OK,函数调用到这里也就完成了应用程序调用hardware内具体设备函数的流程.HAL的实现其实也就是实现上面每个函数.使它们协同合作而已.

 

 

 

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