android从应用到驱动之—camera(2)---cameraHAL的实现

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 <stdio.h> #include <sys/types.h> #include <pthread.h> #include <binder/IPCThreadState.h> #include <binder/IServiceManager.h> #include <binder/MemoryBase.h> #include <binder/MemoryHeapBase.h> #include <cutils/atomic.h> #include <cutils/properties.h> #include <gui/SurfaceTextureClient.h> #include <hardware/hardware.h> #include <media/AudioSystem.h> #include <media/mediaplayer.h> #include <surfaceflinger/ISurface.h> #include <utils/Errors.h> #include <utils/Log.h> #include <utils/String16.h> #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<ICamera> CameraService::connect( const sp<ICameraClient>& cameraClient, int cameraId) { int callingPid = getCallingPid(); sp<CameraHardwareInterface> hardware = NULL; LOG1("CameraService::connect E (pid %d, id %d)", callingPid, cameraId); if (!mModule) { LOGE("Camera HAL module not loaded"); return NULL; } sp<Client> 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<ICameraClient>& 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> 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::Client> 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<MediaPlayer> player = mSoundPlayer[kind]; if (player != 0) { player->seekTo(0); player->start(); } } // ---------------------------------------------------------------------------- CameraService::Client::Client(const sp<CameraService>& cameraService, const sp<ICameraClient>& cameraClient, const sp<CameraHardwareInterface>& 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 client CameraService::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 camera status_t CameraService::Client::connect(const sp<ICameraClient>& 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<ANativeWindow>& 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<IBinder>& binder, const sp<ANativeWindow>& 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 use status_t CameraService::Client::setPreviewDisplay(const sp<Surface>& surface) { LOG1("setPreviewDisplay(%p) (pid %d)", surface.get(), getCallingPid()); sp<IBinder> binder(surface != 0 ? surface->asBinder() : 0); sp<ANativeWindow> window(surface); return setPreviewWindow(binder, window); } // set the SurfaceTexture that the preview will use status_t CameraService::Client::setPreviewTexture( const sp<ISurfaceTexture>& surfaceTexture) { LOG1("setPreviewTexture(%p) (pid %d)", surfaceTexture.get(), getCallingPid()); sp<IBinder> binder; sp<ANativeWindow> 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 mode status_t CameraService::Client::startPreview() { LOG1("startPreview (pid %d)", getCallingPid()); return startCameraMode(CAMERA_PREVIEW_MODE); } // start recording mode status_t CameraService::Client::startRecording() { LOG1("startRecording (pid %d)", getCallingPid()); return startCameraMode(CAMERA_RECORDING_MODE); } // start preview or recording status_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 mode void 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 mode void 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 frame void CameraService::Client::releaseRecordingFrame(const sp<IMemory>& 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 callback status_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 pairs status_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 pairs String8 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 sound status_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 // 10ms bool 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> CameraService::Client::getClientFromCookie(void* user) { sp<Client> 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> 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<IMemory>& dataPtr, camera_frame_metadata_t *metadata, void* user) { LOG2("dataCallback(%d)", msgType); sp<Client> 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<IMemory>& dataPtr, void* user) { LOG2("dataCallbackTimestamp(%d)", msgType); sp<Client> 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 callback void CameraService::Client::handleShutter(void) { if (mPlayShutterSound) { mCameraService->playSound(SOUND_SHUTTER); } sp<ICameraClient> 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 update void CameraService::Client::handlePreviewData(int32_t msgType, const sp<IMemory>& mem, camera_frame_metadata_t *metadata) { ssize_t offset; size_t size; sp<IMemoryHeap> 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<ICameraClient> 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 ready void CameraService::Client::handlePostview(const sp<IMemory>& mem) { disableMsgType(CAMERA_MSG_POSTVIEW_FRAME); sp<ICameraClient> c = mCameraClient; mLock.unlock(); if (c != 0) { c->dataCallback(CAMERA_MSG_POSTVIEW_FRAME, mem, NULL); } } // picture callback - raw image ready void CameraService::Client::handleRawPicture(const sp<IMemory>& mem) { disableMsgType(CAMERA_MSG_RAW_IMAGE); ssize_t offset; size_t size; sp<IMemoryHeap> heap = mem->getMemory(&offset, &size); sp<ICameraClient> c = mCameraClient; mLock.unlock(); if (c != 0) { c->dataCallback(CAMERA_MSG_RAW_IMAGE, mem, NULL); } } // picture callback - compressed picture ready void CameraService::Client::handleCompressedPicture(const sp<IMemory>& mem) { disableMsgType(CAMERA_MSG_COMPRESSED_IMAGE); sp<ICameraClient> 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<ICameraClient> c = mCameraClient; mLock.unlock(); if (c != 0) { c->notifyCallback(msgType, ext1, ext2); } } void CameraService::Client::handleGenericData(int32_t msgType, const sp<IMemory>& dataPtr, camera_frame_metadata_t *metadata) { sp<ICameraClient> c = mCameraClient; mLock.unlock(); if (c != 0) { c->dataCallback(msgType, dataPtr, metadata); } } void CameraService::Client::handleGenericDataTimestamp(nsecs_t timestamp, int32_t msgType, const sp<IMemory>& dataPtr) { sp<ICameraClient> c = mCameraClient; mLock.unlock(); if (c != 0) { c->dataCallbackTimestamp(timestamp, msgType, dataPtr); } } void CameraService::Client::copyFrameAndPostCopiedFrame( int32_t msgType, const sp<ICameraClient>& client, const sp<IMemoryHeap>& 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<MemoryHeapBase> 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<MemoryBase> 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<String16>& 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> 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<CameraService> mCameraService; // immutable after constructor sp<ICameraClient> mCameraClient; int mCameraId; // immutable after constructor int mCameraFacing; // immutable after constructor pid_t mClientPid; sp<CameraHardwareInterface> 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 <hardware/hardware.h> #include <cutils/properties.h> #include <dlfcn.h> #include <string.h> #include <pthread.h> #include <errno.h> #include <limits.h> #define LOG_TAG "HAL" #include <utils/Log.h> /** 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 "<MODULE_ID>.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<HAL_VARIANT_KEYS_COUNT+1 ; i++) { if (i < HAL_VARIANT_KEYS_COUNT) { if (property_get(variant_keys[i], prop, NULL) == 0) { continue; } snprintf(path, sizeof(path), "%s/%s.%s.so", HAL_LIBRARY_PATH2, name, prop); if (access(path, R_OK) == 0) break; snprintf(path, sizeof(path), "%s/%s.%s.so", HAL_LIBRARY_PATH1, name, prop); if (access(path, R_OK) == 0) break; } else { snprintf(path, sizeof(path), "%s/%s.default.so", HAL_LIBRARY_PATH1, name); if (access(path, R_OK) == 0) break; } } status = -ENOENT; if (i < HAL_VARIANT_KEYS_COUNT+1) { /* load the module, if this fails, we're doomed, and we should not try * to load a different variant. */ status = load(class_id, path, module); } return status; } int hw_get_module(const char *id, const struct hw_module_t **module) { return hw_get_module_by_class(id, NULL, module); }

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<hw_module_t *>(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<hw_module_t *>(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_m static 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> 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.