audiopolicy

//framework/av/media/audioserver/main_audioserver.cpp

int main(int argc __unused, char **argv)
{
    .....
    AudioFlinger::instantiate();
    AudioPolicyService::instantiate();

void AudioPolicyService::onFirstRef()
{
    {
        Mutex::Autolock _l(mLock);

        ......
        /** 将自身封装为一个客户端传递个Manager，好处是可以隐藏Service自身内部的逻辑，
        * 只暴露给Manager需要的接口即可，同时也降低耦合       * */
        mAudioPolicyClient = new AudioPolicyClient(this);
        //createAudioPolicyManager方法创建Manager
  mAudioPolicyManager =createAudioPolicyManager(mAudioPolicyClient);
    }
   ......
}
 

AudioPolicyManager::AudioPolicyManager(AudioPolicyClientInterface *clientInterface, bool /*forTesting*/)
    :
    ........
 mpClientInterface(clientInterface),   //参数是AudioPolicyService的this指针
    ........
{
    loadConfig();     //加载音频配置文件
    initialize();         //初始化音频设备信息
}

AudioFlinger::AudioFlinger()
    : BnAudioFlinger(),
      ....
{
    ......
    //创建hal层音频访问hal引用
    mDevicesFactoryHal = DevicesFactoryHalInterface::create();
    //创建hal层音效访问hal层引用
    mEffectsFactoryHal = EffectsFactoryHalInterface::create();
    ......
}

// static
sp<DevicesFactoryHalInterface> DevicesFactoryHalInterface::create() {
    //IDevicesFactory是hal层的HIDL接口，这里先查询hal层支持的版本号，在针对性创建hidl的客户端
    if (hardware::audio::V5_0::IDevicesFactory::getService() != nullptr) {
        return V5_0::createDevicesFactoryHal();
    }
    if (hardware::audio::V4_0::IDevicesFactory::getService() != nullptr) {
        return V4_0::createDevicesFactoryHal();
    }
    if (hardware::audio::V2_0::IDevicesFactory::getService() != nullptr) {
        return V2_0::createDevicesFactoryHal();
    }
    return nullptr;
}

sp<DevicesFactoryHalInterface> createDevicesFactoryHal() {
    return new DevicesFactoryHalHybrid();
}

DevicesFactoryHalHybrid::DevicesFactoryHalHybrid()
        : mLocalFactory(new DevicesFactoryHalLocal()),
        //关注以下成员
          mHidlFactory(new DevicesFactoryHalHidl()) {
}