AudioFlinger与AudioPoliceManager初始化流程

最新推荐文章于 2025-04-22 10:01:53 发布

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最新推荐文章于 2025-04-22 10:01:53 发布 · 1.4k 阅读

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#AudioFlinger #APM #Android

AF/APF启动流程

在启动AudioSeriver服务的过程中会对启动AF/APF。main_audioserver.cpp有如下代码：

    AudioFlinger::instantiate();
    AudioPolicyService::instantiate();

AF初始化流程

1.AudioFlinger::instantiate()

1.1 AudioFlinger构造函数

void AudioFlinger::instantiate() {
   
   
    sp<IServiceManager> sm(defaultServiceManager());
    sm->addService(String16(IAudioFlinger::DEFAULT_SERVICE_NAME),
                   new AudioFlingerServerAdapter(new AudioFlinger()), false,
                   IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT);
}

创建AudioFlingerServerAdapter对象，然后将AudioFlinger对象传入在AudioFlingerr中会调用onFirstRef()函数。

AudioFlinger::AudioFlinger() {
   
   
    mDevicesFactoryHal = DevicesFactoryHalInterface::create();
    mEffectsFactoryHal = EffectsFactoryHalInterface::create();
}

在AudioFlinger的构造函数中会创建DevicesFactoryHalInterface和EffectsFactoryHalInterface对象，DevicesFactoryHalInterface对象会调用HIDL的getDevicesFactory()函数，EffectsFactoryHalInterface对象会调用HIDL的getEffectsFactory()函数。
DevicesFactoryHalInterface.h：

sp<DevicesFactoryHalInterface> DevicesFactoryHalInterface::create() {
   
   
    return createPreferredImpl<DevicesFactoryHalInterface>(
            "android.hardware.audio", "IDevicesFactory");
}

FactoryHalHidl.h

template <class Interface>
static sp<Interface> createPreferredImpl(const std::string& package, const std::string& interface) {
   
   
    return sp<Interface>{
   
   static_cast<Interface*>(detail::createPreferredImpl(package, interface))};
}
void* createPreferredImpl(const std::string& package, const std::string& interface) {
   
   
    for (auto version = detail::sAudioHALVersions; version != nullptr; ++version) {
   
   
        void* rawInterface = nullptr;
        if (hasHalService(package, *version, interface)
                && createHalService(*version, interface, &rawInterface)) {
   
   
            return rawInterface;
        }
    }
    return nullptr;
}
const char* sAudioHALVersions[] = {
   
   
    "7.0",
    "6.0",
    "5.0",
    "4.0",
    nullptr
};

函数hasHalService功能为将"android.hardware.audio"与sAudioHALVersions拼接从7.0开始循环，从serviceManager中查找是否存在当前的服务比如android.hardware.audio@7.0::IDevicesFactory当查到有相关的hidl接口那么就调用函数createHalService
createHalService功能如下：
1.拼接libName =“libaudiohal@”+7.0+“.so” factoryFunctionName = “create”+IDevicesFactory
2.dlopen打开库libaudiohal@7.0.so"
3.dlsym获取函数createIDevicesFactory
4.调用函数createIDevicesFactory
5.返回rawInterface
6.将rawInterface强转成IDevicesFactory类型
DevicesFactoryHalHybrid.cpp

extern "C" __attribute__((visibility("default"))) void* createIDevicesFactory() {
   
   
    auto service = hardware::audio::CPP_VERSION::IDevicesFactory::getService();
    return service ? new CPP_VERSION::DevicesFactoryHalHybrid(service) : nullptr;
}
DevicesFactoryHalHybrid::DevicesFactoryHalHybrid(sp<IDevicesFactory> hidlFactory)
        : mLocalFactory(new DevicesFactoryHalLocal()),
          mHidlFactory(new DevicesFactoryHalHidl(hidlFactory)) {
   
   
}

函数DevicesFactoryHalHybrid功能如下：
1.创建DevicesFactoryHalLocal对象
2.创建DevicesFactoryHalHidl对象
3.将DevicesFactoryHalHidl对象传入DevicesFactoryHalLocal对象

1.2 AudioFlinger::onFirstRef解析

void AudioFlinger::onFirstRef()
{
   
   
 mMode = AUDIO_MODE_NORMAL;

    gAudioFlinger = this;  // we are already refcounted, store into atomic pointer.

    mDevicesFactoryHalCallback = new DevicesFactoryHalCallbackImpl;
    mDevicesFactoryHal->setCallbackOnce(mDevicesFactoryHalCallback);
}