Android Camera(三) CameraService启动流程 (androidP)

最新推荐文章于 2025-10-30 19:38:14 发布

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最新推荐文章于 2025-10-30 19:38:14 发布 · 3.2k 阅读

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本文解析了Android Camera Service的启动过程，从cameraserver.rc配置文件开始，详细跟踪了CameraService的创建、CameraProvider的初始化及服务注册，展示了关键函数如instantiate()和onFirstRef()的作用。

cameraserver.rc

路径 frameworks/av/camera/cameraserver/cameraserver.rc

CameraService是由这个.rc文件启动的关于rc文件参见流程1

service cameraserver /system/bin/cameraserver
    class main
    user cameraserver
    group audio camera input drmrpc readproc
    ioprio rt 4
    writepid /dev/cpuset/camera-daemon/tasks /dev/stune/top-app/tasks
    rlimit rtprio 10 10

main_cameraserver.cpp

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

CameraService::instantiate() 接口定义在 BinderService 中，CameraService继承它，instantiate() 函数定义在

路径 android/frameworks/native/libs/binder/include/binder/BinderService.h

创建一个new CameraService，名为media.camera并将其加入到 ServiceManager 中。

getServiceName() = "media.camera"

因为SP指针的原因下一步调用到的是CameraService::onFirstRef()

int main(int argc __unused, char** argv __unused)
{
    signal(SIGPIPE, SIG_IGN);

    // Set 3 threads for HIDL calls
    hardware::configureRpcThreadpool(3, /*willjoin*/ false);

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


//路径  android/frameworks/native/libs/binder/include/binder/BinderService.h

static void instantiate() { publish(); }

static status_t publish(bool allowIsolated = false,
                            int dumpFlags = IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT) {
        sp<IServiceManager> sm(defaultServiceManager());
        return sm->addService(String16(SERVICE::getServiceName()), new SERVICE(), allowIsolated,
                              dumpFlags);
    }

//路径  frameworks/av/services/camera/libcameraservice/CameraService.h
static char const* getServiceName() { return "media.camera"; }

onFirstRef

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

在 CameraService::onFirstRef() 函数中，主要是调用 enumerateProviders() 函数获取CameraProvider信息

new CameraProviderManager() 之后调用 initialize(), 并将CameraService作为 CameraProviderManager 的成员变量传递进去

void CameraService::onFirstRef()
{
    res = enumerateProviders();
    ...
}

status_t CameraService::enumerat

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