1000字范文 > android_驱动_qcom_【高通SDM660平台】(4) --- Camera Init 初始化流程

android_驱动_qcom_【高通SDM660平台】(4) --- Camera Init 初始化流程

时间：2023-10-19 19:51:54

【高通SDM660平台】Camera Init 初始化流程

一、Camera 系统架构二、Camera Init 初始化流程2.1 CameraService 启动2.2 CameraService::instantiate()2.3 CameraService.cpp2.4 CameraService::CameraService()2.5 CameraService::onFirstRef()2.6 获取Camera数量 mModule->getNumberOfCameras()2.7 hardware层调用 get_num_of_cameras()2.8 Camera Init 初始化流程总结三、hw_get_module()3.1 camera.sdm660.so

《【高通SDM660平台】(1) — Camera 驱动 Bringup Guide》

《【高通SDM660平台】(2) — Camera Kernel 驱动层代码逻辑分析》

《【高通SDM660平台】(3) — Camera V4L2 驱动层分析》

《【高通SDM660平台】(4) — Camera Init 初始化流程》

《【高通SDM660平台】(5) — Camera Open 流程》

《【高通SDM660平台】(6) — Camera getParameters 及 setParameters 流程》

《【高通SDM660平台】(7) — Camera onPreview 代码流程》

《【高通SDM660平台】(8) — Camera MetaData介绍》

《【高通SDM660平台 Android 10.0】(9) — Qcom Camera Daemon 代码分析》

《【高通SDM660平台 Android 10.0】(10) — Camera Sensor lib 与 Kernel Camera Probe 代码分析》

《【高通SDM660平台】Camera Capture 流程》

《【高通SDM660平台】Camera mm-qcamera-app 代码分析》

Open Camera是Preview、TakePicture、Record的基础，Open Camera会初始化很多对象，

而Preview、TakePicture、Record等操作是围绕着这些对象进行操作的，所以这里用Open Camera来理清各个对象间的交互关系

一、Camera 系统架构

看到一张好图，自：《sdm660–opencamera流程详细分析》

Camera模块的系统架构分为四层，从上到下分别是

Package 文件夹下的 Java 层

Framework 文件夹下的 Framework 层

Framework层下细分为：Java Framework、JNI Framework、Hardware Interface Framework 。

Hardware 文件夹下的 Hal 层

HAL 层下又细分为 Hardware Interface 与 mm-camera 层

ADIL 是 JNI Framework 层与 Hardware Interface Framework 层交互的接口，即 CameraClient 进程与 CameraService 进程的交互。

HIDL 是发生在 Framework 层与 HAL层交互的接口。

Kernel 文件夹下的 Driver 层

接下来，我们进代码分析下 Camera Init 初始化流程

二、Camera Init 初始化流程

2.1 CameraService 启动

CameraService 是一个可执行程序放在/system/bin/cameraserver，开机时通过init.rc 文件自启动。

@ frameworks/av/camera/cameraserver/cameraserver.rc

service cameraserver /system/bin/cameraserver

class main

user cameraserver

group audio camera input drmrpc

ioprio rt 4

writepid /dev/cpuset/camera-daemon/tasks /dev/stune/foreground/tasks

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cameraserver 可执行程序代码如下：

@ frameworks/av/camera/cameraserver/main_cameraserver.cpp

#define LOG_TAG “cameraserver”

//#define LOG_NDEBUG 0

#include “CameraService.h”

using namespace android;

int main(int argc __unused, charargv __unused)

{

signal(SIGPIPE, SIG_IGN);

sp<ProcessState> proc(ProcessState::self());sp<IServiceManager> sm = defaultServiceManager();ALOGI("ServiceManager: %p", sm.get());CameraService::instantiate();ProcessState::self()->startThreadPool();IPCThreadState::self()->disableBackgroundScheduling(true);IPCThreadState::self()->joinThreadPool();

}

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2.2 CameraService::instantiate()

@ frameworks/native/include/binder/BinderService.h

public:

static status_t publish(bool allowIsolated = false) {

sp<IServiceManager> sm(defaultServiceManager());

return sm->addService( String16(SERVICE::getServiceName()), new SERVICE(), allowIsolated);

}

static void instantiate() {publish(); }

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这段代码的意思是，向ServiceManager添加 name 为"media.camera"的service 。

String16(SERVICE::getServiceName())=============>// Implementation of BinderService<T>static char const* getServiceName() {return "media.camera"; }

new SERVICE()

相当于调用 new CameraService()

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2.3 CameraService.cpp

由于是还强指针的引用类型，代码new CameraService()，

在调用CameraService::CameraService()同时还会调用void CameraService::onFirstRef()

2.4 CameraService::CameraService()

主要工作如下：

定义全局 CameraService 指针对象 gCameraService初始化变量mNumberOfCameras = 0、mNumberOfNormalCameras = 0、mModule = NULL将当前对象保存在全局 CameraService 指针 gCameraService 中

@ frameworks/av/services/camera/libcameraservice/CameraService.cpp

static CameraService *gCameraService; // 1. 定义全局 CameraService 指针对象

CameraService::CameraService() :

mEventLog(DEFAULT_EVENT_LOG_LENGTH),

mNumberOfCameras(0), mNumberOfNormalCameras(0),

mSoundRef(0), mModule(nullptr) {

ALOGI(“CameraService started (pid=%d)”, getpid());

gCameraService = this; // 2. 将当前对象保存在全局 CameraService 指针中

this->camera_device_status_change = android::camera_device_status_change;this->torch_mode_status_change = android::torch_mode_status_change;mServiceLockWrapper = std::make_shared<WaitableMutexWrapper>(&mServiceLock);

}

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2.5 CameraService::onFirstRef()

主要工作如下：

加载 hal 层 camera module，保存在rawModule中，module定义在hardware/libhardware/include/hardware/camera_common.h初始化CameraModule对像，将camera_module_t *rawModule保存在mModule中调用 Camera HAL module 的init方法，调用mModule->get_number_of_cameras()，用来设置mCameraInfoMapvector 的容量打印hardware camera module的 name ，hal 层代码定义在hardware/qcom/camera/QCamera2/QCamera2Hal.cpp获取 camera 个数，保存在CameraService的私有变量mNumberOfCameras及mNumberOfNormalCameras中初始化CameraFlashlight模块，根据 camera number 初始化mHasFlashlightMapvector 数组变量调用mModule->getCameraInfo()返回hal 层mHalDescriptors 的信息，保存在 info 中通过 BpCameraServiceProxy 远程调用 BnCameraService 的 pingForUserUpdate() 函数

@ frameworks/av/services/camera/libcameraservice/CameraService.cppvoid CameraService::onFirstRef(){ALOGI("CameraService process starting");BnCameraService::onFirstRef();

// 1. 加载 hal 层 camera module，保存在 rawModule 中// #define CAMERA_HARDWARE_MODULE_ID "camera"// module定义在 hardware/libhardware/include/hardware/camera_common.h camera_module_t *rawModule; int err = hw_get_module(CAMERA_HARDWARE_MODULE_ID,(const hw_module_t **)&rawModule);// 2. 初始化 CameraModule 对像，将 camera_module_t *rawModule 保存在 mModule 中mModule = new CameraModule(rawModule);// 3. 调用 Camera HAL module 的 init 方法// 从 hardware/libhardware/include/hardware/camera_common.h 中得知 // #define CAMERA_MODULE_API_VERSION_CURRENT CAMERA_MODULE_API_VERSION_2_4// 因此，hal 层代码位于 hardware/qcom/camera/QCamera2/QCamera2Hal.cpperr = mModule->init();================>+@ frameworks/frameworks-new/av/services/camera/libcameraservice/common/CameraModule.cpp+int CameraModule::init() {+ if (getModuleApiVersion() >= CAMERA_MODULE_API_VERSION_2_4 && mModule->init != NULL) {+ ATRACE_BEGIN("camera_module->init");+ res = mModule->init(); // 从 QCamera2Hal.cpp 中得知，init = NULL+ }+ mCameraInfoMap.setCapacity(getNumberOfCameras());// 设置CameraInfoMap vector的大小+==========>+numCameras = mModule->get_number_of_cameras();+ return res;+}<================// 4. 打印 hardware camera module 的name ，定义在 hardware/qcom/camera/QCamera2/QCamera2Hal.cppALOGI("Loaded \"%s\" camera module", mModule->getModuleName()); // "QCamera Module"// 5. 获取 camera 个数，保存在CameraService 的私有变量 mNumberOfCameras 及 mNumberOfNormalCameras 中mNumberOfCameras = mModule->getNumberOfCameras();mNumberOfNormalCameras = mNumberOfCameras;// 6. 初始化 CameraFlashlight 模块，根据 camera number 初始化 mHasFlashlightMap vector 数组变量mFlashlight = new CameraFlashlight(*mModule, *this);status_t res = mFlashlight->findFlashUnits();// 7. 调用mModule->getCameraInfo()int latestStrangeCameraId = INT_MAX;for (int i = 0; i < mNumberOfCameras; i++) {String8 cameraId = String8::format("%d", i);// Get camera infostruct camera_info info;bool haveInfo = true;status_t rc = mModule->getCameraInfo(i, &info); // 8. 返回 hardware 层 mHalDescriptors 的信息，保存在 info 中// Defaults to use for cost and conflicting devicesint cost = 100;char** conflicting_devices = nullptr;size_t conflicting_devices_length = 0;// If using post-2.4 module version, query the cost + conflicting devices from the HALif (mModule->getModuleApiVersion() >= CAMERA_MODULE_API_VERSION_2_4 && haveInfo) {cost = info.resource_cost;conflicting_devices = info.conflicting_devices;conflicting_devices_length = info.conflicting_devices_length;}std::set<String8> conflicting;for (size_t i = 0; i < conflicting_devices_length; i++) {conflicting.emplace(String8(conflicting_devices[i]));}// Initialize state for each camera device{Mutex::Autolock lock(mCameraStatesLock);mCameraStates.emplace(cameraId, std::make_shared<CameraState>(cameraId, cost, conflicting));}if (mFlashlight->hasFlashUnit(cameraId)) {mTorchStatusMap.add(cameraId, ICameraServiceListener::TORCH_STATUS_AVAILABLE_OFF);}}if (mModule->getModuleApiVersion() >= CAMERA_MODULE_API_VERSION_2_1) {mModule->setCallbacks(this);}// 9. 通过 BpCameraServiceProxy 远程调用 BnCameraService 的 pingForUserUpdate() 函数// 远程函数位于 IMPLEMENT_META_INTERFACE(CameraServiceProxy, "android.hardware.ICameraServiceProxy");CameraService::pingCameraServiceProxy();

}

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2.6 获取Camera数量 mModule->getNumberOfCameras()

进入hardware 层代码中：

@ hardware/qcom/camera/QCamera2/QCamera2Hal.cpp

camera_module_t HAL_MODULE_INFO_SYM = {

.common = camera_common,

.get_number_of_cameras = qcamera::QCamera2Factory::get_number_of_cameras,

.get_camera_info = qcamera::QCamera2Factory::get_camera_info,

.set_callbacks = qcamera::QCamera2Factory::set_callbacks,

.get_vendor_tag_ops = qcamera::QCamera3VendorTags::get_vendor_tag_ops,

.open_legacy = qcamera::QCamera2Factory::open_legacy,

.set_torch_mode = qcamera::QCamera2Factory::set_torch_mode,

.init = NULL,

.reserved = {0}

};

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首先初始化gQCamera2Factory对像，接着判断当前camera hal 层走 HAL1 还是 HAL3，调用对应的接口。

camera 个数是直接返回的变量mNumOfCameras_expose，

而mNumOfCameras_expose变量是在gQCamera2Factory()中赋值的。

接着，通过判定是否支持双摄，来调用不同的getNumberOfCameras()函数

@ hardware/qcom/camera/QCamera2/QCamera2Factory.cpp

int QCamera2Factory::get_number_of_cameras()

{

int numCameras = 0;

if (!gQCamera2Factory) {

gQCamera2Factory = new QCamera2Factory();

}

#ifdef QCAMERA_HAL1_SUPPORT

if(gQCameraMuxer)

numCameras = gQCameraMuxer->get_number_of_cameras();

else

#endif

numCameras = gQCamera2Factory->getNumberOfCameras();

===> return mNumOfCameras_expose;

LOGH("num of cameras: %d", numCameras);return numCameras;

}

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接下来进入函数QCamera2Factory()看下：

打开/dev/mediax节点获取camera 的个数，保存在g_cam_ctrl.num_cam返回g_cam_ctrl.num_cam_to_expose = g_cam_ctrl.num_cam - is_secure;，此处我们没有 secure ，所就它就是camera 个数判断当前Camera系统是否支待 HAL3，且如果没有定义QCAMERA_HAL1_SUPPORT,则默认支持 HAL3判断当前Camera系统是否支持双摄，如果是走HAL3 ，即未定义QCAMERA_HAL1_SUPPORT，默认不支待双摄判断当前Camera系统中所有camera是否走的是HAL3， YUV sensor是只能走HAL1 了更新 mHalDescriptors 中每个camear id 所对应的 HAL API VERSION

QCamera2Factory::QCamera2Factory(){mHalDescriptors = NULL;mCallbacks = NULL;mNumOfCameras = get_num_of_cameras();// 1. 打开/dev/mediax 节点获取camera 的个数，保存在g_cam_ctrl.num_cammNumOfCameras_expose = get_num_of_cameras_to_expose(); // 2. 返回 g_cam_ctrl.num_cam_to_expose = g_cam_ctrl.num_cam - is_secure; ，此处我们没有 secure ，所就它就是camera 个数int bDualCamera = 0;char propDefault[PROPERTY_VALUE_MAX];char prop[PROPERTY_VALUE_MAX];// 3. 判断当前Camera系统是否支待 HAL3，且如果没有定义QCAMERA_HAL1_SUPPORT ,则默认支持 HAL3property_get("persist.camera.HAL3.enabled", prop, "0");int isHAL3Enabled = atoi(prop);#ifndef QCAMERA_HAL1_SUPPORTisHAL3Enabled = 1;#endif

// 4. 判断当前Camera系统是否支持双摄，如果是走HAL3 ，即未定义QCAMERA_HAL1_SUPPORT ，默认不支待双摄// Signifies whether system has to enable dual camera modesnprintf(propDefault, PROPERTY_VALUE_MAX, "%d", isDualCamAvailable(isHAL3Enabled));property_get("persist.camera.dual.camera", prop, "0");bDualCamera = atoi(prop);LOGH("dualCamera:%d ", bDualCamera);

#ifndef QCAMERA_HAL1_SUPPORT

bDualCamera = 0;

#endif

if(bDualCamera) {LOGI("Enabling QCamera Muxer");

#ifdef QCAMERA_HAL1_SUPPORT

if (!gQCameraMuxer) {

QCameraMuxer::getCameraMuxer(&gQCameraMuxer, mNumOfCameras);

if (!gQCameraMuxer) {

LOGE(“Error !! Failed to get QCameraMuxer”);

}

#endif

}

#ifdef QCAMERA_HAL1_SUPPORT

if (!gQCameraMuxer && (mNumOfCameras > 0) &&(mNumOfCameras <= MM_CAMERA_MAX_NUM_SENSORS)) {

#else

if ((mNumOfCameras > 0) &&(mNumOfCameras <= MM_CAMERA_MAX_NUM_SENSORS)) {

#endif

mHalDescriptors = new hal_desc[mNumOfCameras];

if ( NULL != mHalDescriptors) {

uint32_t cameraId = 0;

// 5. 判断当前Camera系统中所有camera是否走的是HAL3， YUV sensor是只能走HAL1 了// 6. 更新 mHalDescriptors 中每个camear id 所对应的 HAL API VERSIONfor (int i = 0; i < mNumOfCameras ; i++, cameraId++) {mHalDescriptors[i].cameraId = cameraId;// Set Device version to 3.x when both HAL3 is enabled & its BAYER sensorif (isHAL3Enabled && !(is_yuv_sensor(cameraId))) {mHalDescriptors[i].device_version = CAMERA_DEVICE_API_VERSION_3_0;} else {mHalDescriptors[i].device_version = CAMERA_DEVICE_API_VERSION_1_0;}}}}

}

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2.7 hardware层调用 get_num_of_cameras()

打开/dev/media0 -->（msm_config）msm_sensor_init/dev/media1 ---->（msm_camera）v4l2调用MEDIA_IOC_DEVICE_INFO获取设备信息如果判断不是msm_config则直接continue寻找entity.id = 2的所有subdev，且type=MEDIA_ENT_T_V4L2_SUBDEV , group_id=14 , name = "msm_sensor_init"找开/dev/media0 /dev/media1 ...，开始查找camear 个数，保存在g_cam_ctrl.num_cam中如果判断不是msm_config则直接continue遍历 V4L2 下camear 的个数获取所有信息，保存在g_cam_ctrl中

hardware/qcom/camera/QCamera2/stack/mm-camera-interface/src/mm_camera_interface.c

uint8_t get_num_of_cameras()

{

struct media_device_info mdev_info;

int num_media_devices = 0;

int8_t num_cameras = 0;

char subdev_name[32];

char prop[PROPERTY_VALUE_MAX];

LOGD(“E”);

memset (&g_cam_ctrl, 0, sizeof (g_cam_ctrl));while (1) {uint32_t num_entities = 1U;char dev_name[32];// 1. 打开 /dev/media0 -->（msm_config）msm_sensor_init/dev/media1 ---->（msm_camera）v4l2snprintf(dev_name, sizeof(dev_name), "/dev/media%d", num_media_devices);dev_fd = open(dev_name, O_RDWR | O_NONBLOCK);num_media_devices++;// 2. 调用 MEDIA_IOC_DEVICE_INFO 获取设备信息rc = ioctl(dev_fd, MEDIA_IOC_DEVICE_INFO, &mdev_info);===============>+// kernel/msm-4.4/drivers/media/media-device.c+static long media_device_ioctl(struct file *filp, unsigned int cmd, unsigned long arg){+switch (cmd) {+case MEDIA_IOC_DEVICE_INFO:+ret = media_device_get_info(dev, (struct media_device_info __user *)arg);+============>+-strlcpy(info.driver, dev->dev->driver->name, sizeof(info.driver));+-strlcpy(info.model, dev->model, sizeof(info.model));+-strlcpy(info.serial, dev->serial, sizeof(info.serial));+-strlcpy(info.bus_info, dev->bus_info, sizeof(info.bus_info));+-+-info.media_version = MEDIA_API_VERSION;+-info.hw_revision = dev->hw_revision;+-info.driver_version = dev->driver_version;+-copy_to_user(__info, &info, sizeof(*__info))+<============+break;++case MEDIA_IOC_ENUM_ENTITIES:+ret = media_device_enum_entities(dev, (struct media_entity_desc __user *)arg);+break;+}<===============// 3. 如果判断不是 msm_config 则直接continue if (strncmp(mdev_info.model, MSM_CONFIGURATION_NAME, sizeof(mdev_info.model)) != 0) {close(dev_fd);dev_fd = -1;continue;}while (1) {struct media_entity_desc entity;memset(&entity, 0, sizeof(entity));entity.id = num_entities++;// 2LOGD("entity id %d", entity.id);// 4. 寻找 entity.id = 2 的所有subdev ，且 type=MEDIA_ENT_T_V4L2_SUBDEV , group_id=14 , name = "msm_sensor_init"rc = ioctl(dev_fd, MEDIA_IOC_ENUM_ENTITIES, &entity);===========>+ media_device_enum_entities(dev, (struct media_entity_desc __user *)arg);+------->+pvdev->vdev->entity.type = MEDIA_ENT_T_DEVNODE_V4L; // V4L+pvdev->vdev->entity.group_id = QCAMERA_VNODE_GROUP_ID; // #define QCAMERA_VNODE_GROUP_ID 2+<-------<===========LOGD("entity name %s type %d group id %d", entity.name, entity.type, entity.group_id);if (entity.type == MEDIA_ENT_T_V4L2_SUBDEV && entity.group_id == MSM_CAMERA_SUBDEV_SENSOR_INIT) {snprintf(subdev_name, sizeof(dev_name), "/dev/%s", entity.name);break;}}close(dev_fd);dev_fd = -1;}num_media_devices = 0;while (1) {uint32_t num_entities = 1U;char dev_name[32];// 5. 找开 /dev/media0 /dev/media1 ... ，开始查找camear 个数snprintf(dev_name, sizeof(dev_name), "/dev/media%d", num_media_devices);dev_fd = open(dev_name, O_RDWR | O_NONBLOCK);num_media_devices++;memset(&mdev_info, 0, sizeof(mdev_info));rc = ioctl(dev_fd, MEDIA_IOC_DEVICE_INFO, &mdev_info);// 6. 如果判断不是 `msm_camera` 则直接`continue` if(strncmp(mdev_info.model, MSM_CAMERA_NAME, sizeof(mdev_info.model)) != 0) {close(dev_fd);dev_fd = -1;continue;}while (1) {struct media_entity_desc entity;memset(&entity, 0, sizeof(entity));entity.id = num_entities++;rc = ioctl(dev_fd, MEDIA_IOC_ENUM_ENTITIES, &entity);// 7. 遍历 V4L2 下camear 的个数if(entity.type == MEDIA_ENT_T_DEVNODE_V4L && entity.group_id == QCAMERA_VNODE_GROUP_ID) {strlcpy(g_cam_ctrl.video_dev_name[num_cameras], entity.name, sizeof(entity.name));LOGI("dev_info[id=%d,name='%s']\n", (int)num_cameras, g_cam_ctrl.video_dev_name[num_cameras]);num_cameras++;break;}}close(dev_fd);dev_fd = -1;if (num_cameras >= MM_CAMERA_MAX_NUM_SENSORS) {LOGW("Maximum number of camera reached %d", num_cameras);break;}}g_cam_ctrl.num_cam = num_cameras;// 8. 获取所有信息，保存在 g_cam_ctrl 中get_sensor_info();// 9. 重新整理 g_cam_ctrl 中的camear 顺序，确保后摄inx 比前摄大/* Order of the camera exposed is0 - Back Main Camera1 - Front Main Camera++ - Back Aux Camera++ - Front Aux Camera++ - Back Main + Back Aux camera++ - Front Main + Front Aux camera++ - Secure Camera*/sort_camera_info(g_cam_ctrl.num_cam);/* unlock the mutex */LOGI("num_cameras=%d\n", (int)g_cam_ctrl.num_cam);return(uint8_t)g_cam_ctrl.num_cam;

}

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2.8 Camera Init 初始化流程总结

在Init 整个过程中，主要做了如下事情：

定义全局 CameraService 指针对象 gCameraService。加载 hal 层 camera module，保存在rawModule中，module定义在hardware/libhardware/include/hardware/camera_common.h。调用Camera hardware module 的mModule->get_number_of_cameras()，获得Camera Number。调用 MEDIA_IOC_DEVICE_INFO 获取驱动层 Camera V4L2 的所有设备信息。同时初始化 hardware 层的 mHalDescriptors 数组，更新每个Camera 使用的 camera hal1 还是 hal3。

三、hw_get_module()

在前面代码中，主要是通过hw_get_module(CAMERA_HARDWARE_MODULE_ID,(const hw_module_t **)&rawModule)来获取到驱动层的相关接口。

接下来，我们来看下hw_get_module具体做了什么操作：

@ hardware/libhardware/hardware.c

int hw_get_module(const charid, const struct hw_module_t *module)

{

return hw_get_module_by_class(id, NULL, module);

}

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由此可知，CameraService.cpp中调用hw_get_module，传递的参数为CAMERA_HARDWARE_MODULE_ID和&rawModule

#define CAMERA_HARDWARE_MODULE_ID "camera"

进入hw_get_module_by_class()分析下:

id = "camera"、inst = NULL、module = &rawModule拼凑出 PATH_MAX = "camera"

@ hardware/libhardware/hardware.c

int hw_get_module_by_class(const charclass_id, const char inst, const struct hw_module_tmodule)

{

int i = 0;

char prop[PATH_MAX] = {0};

char path[PATH_MAX] = {0};

char name[PATH_MAX] = {0};

char prop_name[PATH_MAX] = {0};

// 1. 拼凑出 PATH_MAX = "camera"if (inst)snprintf(name, PATH_MAX, "%s.%s", class_id, inst);elsestrlcpy(name, class_id, PATH_MAX);// 2. 拼凑出 prop_name = "ro.hardware.camera"/* First try a property specific to the class and possibly instance */snprintf(prop_name, sizeof(prop_name), "ro.hardware.%s", name);if (property_get(prop_name, prop, NULL) > 0) {if (hw_module_exists(path, sizeof(path), name, prop) == 0) {goto found;}}/* Loop through the configuration variants looking for a module */for (i=0 ; i<HAL_VARIANT_KEYS_COUNT; i++) {if (property_get(variant_keys[i], prop, NULL) == 0) {continue;}if (hw_module_exists(path, sizeof(path), name, prop) == 0) {goto found;}}/* Nothing found, try the default */if (hw_module_exists(path, sizeof(path), name, "default") == 0) {goto found;}return -ENOENT;

found:

/* load the module, if this fails, we’re doomed, and we should not try

* to load a different variant. */

return load(class_id, path, module);

}

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可以看出，在hardware.c 中，在如下三个目录依次查找 ”camera.sdm660.so“ ，找到后，

接下来load 库文件

// @ hardware/libhardware/hardware.c#define HAL_LIBRARY_PATH1 "/system/lib64/hw"#define HAL_LIBRARY_PATH2 "/vendor/lib64/hw"#define HAL_LIBRARY_PATH3 "/odm/lib64/hw"

Check if a HAL with given name and subname exists, if so return 0, otherwise

otherwise return negative. On success path will contain the path to the HAL.

static int hw_module_exists(charpath, size_t path_len, const charname, const char subname)

{

snprintf(path, path_len, “%s/%s.%s.so”, HAL_LIBRARY_PATH3, name, subname);

if (access(path, R_OK) == 0)

return 0;

snprintf(path, path_len, “%s/%s.%s.so”, HAL_LIBRARY_PATH2, name, subname);

if (access(path, R_OK) == 0)

return 0;

snprintf(path, path_len, “%s/%s.%s.so”, HAL_LIBRARY_PATH1, name, subname);

if (access(path, R_OK) == 0)

return 0;

return -ENOENT;

}

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3.1 camera.sdm660.so

camera.sdm660.so文件代码位于hardware/qcom/camera/QCamera2/

# Enable SDLLVM compiler option for build flavour >= N flavourPLATFORM_SDK_NPDK = 24

LOCAL_COPY_HEADERS_TO := qcom/camera

LOCAL_COPY_HEADERS := QCameraFormat.h

LOCAL_SRC_FILES :=

util/QCameraBufferMaps.cpp

util/QCameraCmdThread.cpp

util/QCameraFlash.cpp

util/QCameraPerf.cpp

util/QCameraQueue.cpp

util/QCameraCommon.cpp

util/QCameraTrace.cpp

util/camscope_packet_type.cpp

QCamera2Hal.cpp

QCamera2Factory.cpp

#HAL 3.0 source

LOCAL_SRC_FILES +=

HAL3/QCamera3HWI.cpp

HAL3/QCamera3Mem.cpp

HAL3/QCamera3Stream.cpp

HAL3/QCamera3Channel.cpp

HAL3/QCamera3VendorTags.cpp

HAL3/QCamera3PostProc.cpp

HAL3/QCamera3CropRegionMapper.cpp

HAL3/QCamera3StreamMem.cpp

LOCAL_CFLAGS := -Wall -Wextra -Werror

#HAL 1.0 source

ifeq ($(TARGET_SUPPORT_HAL1),false)

LOCAL_CFLAGS += -DQCAMERA_HAL3_SUPPORT

else

LOCAL_CFLAGS += -DQCAMERA_HAL1_SUPPORT

LOCAL_SRC_FILES +=

HAL/QCamera2HWI.cpp

HAL/QCameraMuxer.cpp

HAL/QCameraMem.cpp

HAL/QCameraStateMachine.cpp

util/QCameraDisplay.cpp

HAL/QCameraChannel.cpp

HAL/QCameraStream.cpp

HAL/QCameraPostProc.cpp

HAL/QCamera2HWICallbacks.cpp

HAL/QCameraParameters.cpp

HAL/QCameraParametersIntf.cpp

HAL/QCameraThermalAdapter.cpp

util/QCameraFOVControl.cpp

util/QCameraHALPP.cpp

util/QCameraDualFOVPP.cpp

util/QCameraExtZoomTranslator.cpp

util/QCameraPprocManager.cpp

util/QCameraBokeh.cpp

util/QCameraClearSight.cpp

endif

LOCAL_MODULE_RELATIVE_PATH := hw

LOCAL_MODULE := camera.$(TARGET_BOARD_PLATFORM)

LOCAL_MODULE_TAGS := optional

LOCAL_32_BIT_ONLY := $(BOARD_QTI_CAMERA_32BIT_ONLY)

include $(BUILD_SHARED_LIBRARY)

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参考：

《sdm660–opencamera流程详细分析》

《Android camera fw学习(二)-open camera操作过程&准备工作分析》

《高通平台Camera框架部分浅谈–Camera C/S 的init流程》

《Android6.0 camera初始化及预览流程》

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