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Xiaobian to share with you android7 camera hardware acquisition process hal example analysis, I believe most people still do not know how to share this article for your reference, I hope you have a lot of harvest after reading this article, let us go to understand it together!

Analyze the acquisition process of mModule. This variable will be used in camera open.

The main function of this function is to find the address of the dynamic link library of the hardware module according to the module ID, and then call load to open the dynamic link library and obtain the address of the hardware module structure.

File CameraService.cpp

inlet

CameraService.cpp

{

ALOGI("CameraService process starting");

BnCameraService::onFirstRef();

// Update battery life tracking if service is restarting

BatteryNotifier& notifier(BatteryNotifier::getInstance());

notifier.noteResetCamera();

notifier.noteResetFlashlight();

camera_module_t *rawModule;

//The process of analysis is how rawModule obtains the required value (i.e. the final variable pHmi)

int err = hw_get_module(CAMERA_HARDWARE_MODULE_ID,

(const hw_module_t **)&rawModule);

if (err

< 0) { ALOGE("Could not load camera HAL module: %d (%s)", err, strerror(-err)); logServiceError("Could not load camera HAL module", err); mNumberOfCameras = 0; mNumberOfNormalCameras = 0; return; } mModule = new CameraModule(rawModule); err = mModule->

init();

if (err != OK) {

ALOGE("Could not initialize camera HAL module: %d (%s)", err,

strerror(-err));

logServiceError("Could not initialize camera HAL module", err);

mNumberOfCameras = 0;

delete mModule;

mModule = nullptr;

return;

}

ALOGI("Loaded \"%s\" camera module", mModule->getModuleName());

mNumberOfCameras = mModule->getNumberOfCameras();

mNumberOfNormalCameras = mNumberOfCameras;

// Setup vendor tags before we call get_camera_info the first time

// because HAL might need to setup static vendor keys in get_camera_info

VendorTagDescriptor::clearGlobalVendorTagDescriptor();

if (mModule->getModuleApiVersion() >= CAMERA_MODULE_API_VERSION_2_2) {

setUpVendorTags();

}

mFlashlight = new CameraFlashlight(*mModule, *this);

status_t res = mFlashlight->findFlashUnits();

if (res) {

// impossible because we haven't open any camera devices.

ALOGE("Failed to find flash units. ");

}

int latestStrangeCameraId = INT_MAX;

for (int i = 0; i

< mNumberOfCameras; i++) { String8 cameraId = String8::format("%d", i); // Get camera info struct camera_info info; bool haveInfo = true; status_t rc = mModule->

getCameraInfo(i, &info);

if (rc != NO_ERROR) {

ALOGE("%s: Received error loading camera info for device %d, cost and"

" conflicting devices fields set to defaults for this device. ",

__FUNCTION__, i);

haveInfo = false;

}

// Check for backwards-compatibility support

if (haveInfo) {

if (checkCameraCapabilities(i, info, &latestStrangeCameraId) != OK) {

delete mModule;

mModule = nullptr;

return;

}

}

// Defaults to use for cost and conflicting devices

int 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 HAL

if (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 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(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);

}

CameraDeviceFactory::registerService(this);

CameraService::pingCameraServiceProxy();

}

文件hardware.c

hw_get_module方法 很关键

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

{

return hw_get_module_by_class(id, NULL, module);

}

hw_get_module_by_class() 方法

读取库文件，尝试的顺序是：

ro.hardware

ro.product.board

ro.board.platform

ro.arch

default

通过 load 函数加载模块。

int hw_get_module_by_class(const char *class_id, const char *inst,

const struct hw_module_t **module)

{

int i = 0;

char prop[PATH_MAX] = {0};

char path[PATH_MAX] = {0};

char name[PATH_MAX] = {0};

char prop_name[PATH_MAX] = {0};

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.

*/

/* 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 ; iid) != 0) {

ALOGE("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 {

ALOGV("loaded HAL id=%s path=%s hmi=%p handle=%p",

id, path, *pHmi, handle);

}

//pHmi就是我们要的，最后指向 camera_module_t

*pHmi = hmi;

return status;

}

在回到文件CameraModule.cpp

注意，这里的 mModule 是 camera_module_t 类型。

CameraModule::CameraModule(camera_module_t *module) {

if (module == NULL) {

ALOGE("%s: camera hardware module must not be null", __FUNCTION__);

assert(0);

}

mModule = module;

}

继续init()函数

int CameraModule::init() {

ATRACE_CALL();

int res = OK;

if (getModuleApiVersion() >= CAMERA_MODULE_API_VERSION_2_4 &&

mModule->init != NULL) {

ATRACE_BEGIN("camera_module->init");

res = mModule->init();

ATRACE_END();

}

mCameraInfoMap.setCapacity(getNumberOfCameras());

return res;

}

文件camera_common.h

声明了 camera_module_t：

结构体中声明了许多函数指针。

其中就有 init 函数指针。

这个指针指向的具体函数，是根据具体的 Camera 设备确定的，其中我查看了 QCamera2Factory.cpp ，这里就实现了对应的函数

typedef struct camera_module {

hw_module_t common;

int (*get_number_of_cameras)(void);

int (*get_camera_info)(int camera_id, struct camera_info *info);

int (*set_callbacks)(const camera_module_callbacks_t *callbacks);

void (*get_vendor_tag_ops)(vendor_tag_ops_t* ops);

int (*open_legacy)(const struct hw_module_t* module, const char* id,

uint32_t halVersion, struct hw_device_t** device);

int (*set_torch_mode)(const char* camera_id, bool enabled);

int (*init)();

/* reserved for future use */

void* reserved[5];

} camera_module_t;

以上是"android7相机硬件设备获取过程hal的示例分析"这篇文章的所有内容，感谢各位的阅读!相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注行业资讯频道!

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