AudioFlinger启动过程分析(android_audio)

Posted 2021-08-02 we1less

参考 https://blog.csdn.net/zyuanyun/article/details/60890534#t4

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首先来分析一下AudioFlinger

  里面存在一个数组mPlaybackThreads里面的每一个线程都对应一个output

1.加载哪个so文件? 文件名是什么? 文件名从何而来? 

参考上一篇https://blog.csdn.net/we1less/article/details/118424539

openDevice  hardware/interfaces/audio/2.0/default/DevicesFactory.cpp  环节

  audio.primary.xxx.so

  audio.primary.goldfish.so

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 2.该so文件由什么源文件组成?    (此部分有待验证)

    audio.primary.$(TARGET_DEVICE) : device/friendly-arm/common/libaudio/AudioHardware.cpp
                                     libhardware_legacy
    libhardware_legacy :     hardware/libhardware_legacy/audio/audio_hw_hal.cpp

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 3.对硬件的封装:

AudioHwDevice  frameworks/av/services/audioflinger/AudioHwDevice.cpp

  每一个AudioHwDevice对应一个.so动态库所支持的设备

  再把这些支持的硬件加入到mAudioHwDevs里面

audio_module_handle_t AudioFlinger::loadHwModule_l(const char *name){
    ...
    sp<DeviceHalInterface> dev;
    int rc = mDevicesFactoryHal->openDevice(name, &dev);
    ...
    mAudioHwDevs.add(handle, new AudioHwDevice(handle, name, dev, flags));
}

loadAudioInterface  hardware/interfaces/audio/2.0/default/DevicesFactory.cpp 

   audio_hw_device_t 结构体在 

   libhardware  hardware/libhardware/include/hardware/audio.h

int DevicesFactory::loadAudioInterface(const char *if_name, audio_hw_device_t **dev)
{
    const hw_module_t *mod;
    int rc;
    rc = hw_get_module_by_class(AUDIO_HARDWARE_MODULE_ID, if_name, &mod);
    ...
    rc = audio_hw_device_open(mod, dev);
    ...
out:
    *dev = NULL;
    return rc;
}

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main  frameworks/av/media/audioserver/main_audioserver.cpp

int main(int argc __unused, char **argv)
{    
    sp<ProcessState> proc(ProcessState::self());
    sp<IServiceManager> sm = defaultServiceManager();
    ALOGI("ServiceManager: %p", sm.get());

    AudioFlinger::instantiate();

    AudioPolicyService::instantiate();
    ProcessState::self()->startThreadPool();
    android::hardware::ProcessState::self()->startThreadPool();
    IPCThreadState::self()->joinThreadPool();
}