Android Q Audio 自上而下的调用逻辑和各模块相关初始化（AudioFlinger通信、Audio hal 加载、AudioDevice 选择）
随手笔记系列，内容较多较繁琐，用于结合目录快速查询
本文将通过AudioManger的setMastermute Api的通信传递实现逻辑，自上而下梳理一下调用顺序和各模块相关初始化，最终到的audio_hw.c来实现静音
文章目录
- Android Q Audio 自上而下的调用逻辑和各模块相关初始化（AudioFlinger通信、Audio hal 加载、AudioDevice 选择）
- 二、native层通信
- 2.1 AudioFlinger
- 2.1.1 AudioServce启动
- 2.1.2 AudioFlinger初始化
- 2.1.3 AudioFlinger的获取
- 2.1.4 IAudioFlinger 介绍
- 2.1.5 BpAudioFlinger
- 2.1.6 BnAudioFlinger
- 2.1.7 AudioFlinger setMasterMute逻辑
- 2.2 AudioHAL加载
- 2.2.1 DevicesFactoryHalInterface create()
- 2.2.2 DevicesFactoryHalHybrid device工厂
- 2.2.3 DevicesFactoryHalHidl 实例化
二、native层通信
2.1 AudioFlinger
AudioFlinger是两个audio nativeservice中的一个，用于管理声音的播放和录制，volume和硬件相关设置也在audioFlinger中进行
AudioSystem到AudioFlinger大概流程为
AudioSystem -> BpAudioFlinger -> binder -> BnAudioFlinger -> AudioFlinger
2.1.1 AudioServce启动
解析 AudioServer.rc
Audioserver.rc (f:\q\frameworks\av\media\audioserver) 794 2020/2/22
service audioserver /system/bin/audioserver
class core
user audioserver
# media gid needed for /dev/fm (radio) and for /data/misc/media (tee)
group audio camera drmrpc inet media mediadrm net_bt net_bt_admin net_bw_acct wakelock
capabilities BLOCK_SUSPEND
ioprio rt 4
writepid /dev/cpuset/foreground/tasks /dev/stune/foreground/tasks
onrestart restart vendor.audio-hal-2-0
onrestart restart vendor.audio-hal-4-0-msd
# Keep the original service name for backward compatibility when upgrading
# O-MR1 devices with framework-only.
onrestart restart audio-hal-2-0
on property:vts.native_server.on=1
stop audioserver
on property:vts.native_server.on=0
start audioserver
on init
mkdir /dev/socket/audioserver 0775 audioserver audioserverAndroid.mk
rameworks/av/media/audioserver/Android.mk
LOCAL_SRC_FILES := \
main_audioserver.cpp \
LOCAL_C_INCLUDES := \
frameworks/av/services/audioflinger \
frameworks/av/services/audiopolicy \
LOCAL_MODULE := audioserver
LOCAL_INIT_RC := audioserver.rcMain_audioserver.cpp (f:\q\frameworks\av\media\audioserver) 5892 2020/2/22
int main(int argc __unused, char **argv)
{
AudioFlinger::instantiate();
AudioPolicyService::instantiate();
}2.1.2 AudioFlinger初始化
AudioFlinger::instantiate(); 实际上是BinderService的instantiate
template<typename SERVICE>
class BinderService
{
static status_t publish(bool allowIsolated = false,
int dumpFlags = IServiceManager::DUMP_FLAG_PRIORITY_DEFAULT) {
sp<IServiceManager> sm(defaultServiceManager());
//实例化 并add到 service_manager里
return sm->addService(String16(SERVICE::getServiceName()), new SERVICE(), allowIsolated,
dumpFlags);
}
static void instantiate() { publish(); }
}
//AudioFlinger 继承BinderService SERVICE为AudioFlinger
class AudioFlinger :
public BinderService<AudioFlinger>,
public BnAudioFlingernew SERVICE() 实际上是AudioFlinger的构造函数，就存在一个AF的类实例，可以通过service_manager的getService访问，再之后onFirstRef会被执行。onFirstRef（）属于其父类RefBase，该函数在强引用sp新增引用计数时调用。就是当 有sp包装的类初始化的时候调用。
AudioFinger继承BnAudioFlinger
AudioFlinger::AudioFlinger()
: BnAudioFlinger(),
mMediaLogNotifier(new AudioFlinger::MediaLogNotifier()),
mPrimaryHardwareDev(NULL),
mAudioHwDevs(NULL),
mHardwareStatus(AUDIO_HW_IDLE),
mMasterVolume(1.0f),
mMasterMute(false),
// mNextUniqueId(AUDIO_UNIQUE_ID_USE_MAX),
mMode(AUDIO_MODE_INVALID),
mBtNrecIsOff(false),
mIsLowRamDevice(true),
mIsDeviceTypeKnown(false),
mTotalMemory(0),
mClientSharedHeapSize(kMinimumClientSharedHeapSizeBytes),
mGlobalEffectEnableTime(0),
mPatchPanel(this),
mSystemReady(false)
{
//device hal 加载
mDevicesFactoryHal = DevicesFactoryHalInterface::create();
//effect hal 加载
mEffectsFactoryHal = EffectsFactoryHalInterface::create();
mMediaLogNotifier->run("MediaLogNotifier");
}
void AudioFlinger::onFirstRef()
{
//初始化audio mode
mMode = AUDIO_MODE_NORMAL;
gAudioFlinger = this;
}BnAudioFlinger
BnAudioFlinger 作为AudioSystem -> AF 的客户端接口
IAudioFlinger.h (f:\q\frameworks\av\media\libaudioclient\include\media) 22638 2020/2/22
class BnAudioFlinger : public BnInterface<IAudioFlinger>
{
public:
virtual status_t onTransact( uint32_t code,
const Parcel& data,
Parcel* reply,
uint32_t flags = 0);
// Requests media.log to start merging log buffers
virtual void requestLogMerge() = 0;
};2.1.3 AudioFlinger的获取
AudioSystem中有get_audio_flinger()方法获取BpAudioFlinger，通过binder与audioFlinger进行通信的
const sp<IAudioFlinger> AudioSystem::get_audio_flinger()
{
sp<IAudioFlinger> af;
sp<AudioFlingerClient> afc;
{
Mutex::Autolock _l(gLock);
if (gAudioFlinger == 0) {
//通过handle 0 binder通信 获取service_manager
sp<IServiceManager> sm = defaultServiceManager();
sp<IBinder> binder;
do {
//get 之前add的service
binder = sm->getService(String16("media.audio_flinger"));
if (binder != 0)
break;
ALOGW("AudioFlinger not published, waiting...");
usleep(500000); // 0.5 s
} while (true);
if (gAudioFlingerClient == NULL) {
//创建AudioFlingerClient bn端 用于 audioFlinger ->audioSystem的通信
gAudioFlingerClient = new AudioFlingerClient();
} else {
if (gAudioErrorCallback) {
gAudioErrorCallback(NO_ERROR);
}
}
binder->linkToDeath(gAudioFlingerClient);
//强转
gAudioFlinger = interface_cast<IAudioFlinger>(binder);
LOG_ALWAYS_FATAL_IF(gAudioFlinger == 0);
afc = gAudioFlingerClient;
// Make sure callbacks can be received by gAudioFlingerClient
//启动binder线程池，用于af能找到这个AudioFlingerClient bn端
ProcessState::self()->startThreadPool();
}
af = gAudioFlinger;
}
if (afc != 0) {
int64_t token = IPCThreadState::self()->clearCallingIdentity();
af->registerClient(afc);
IPCThreadState::self()->restoreCallingIdentity(token);
}
return af;
}2.1.4 IAudioFlinger 介绍
IAudioFlinger是继承了Interface，定义了 AudioSystem和AudioFlinger之间通信的接口，类似java层的aidl，其中参数数据使用Parcel进行传输
IAudioFlinger.h (f:\q\frameworks\av\media\libaudioclient\include\media) 22638 2020/2/22
class IAudioFlinger : public IInterface
{
virtual status_t setMasterVolume(float value) = 0;
virtual status_t setMasterMute(bool muted) = 0;
virtual float masterVolume() const = 0;
virtual bool masterMute() const = 0;
}2.1.5 BpAudioFlinger
通过Parcel 写入数据 remote可简单理解最后调用Bn端的 AudioFlinger，其实涉及到复杂的binder驱动
class BpAudioFlinger : public BpInterface<IAudioFlinger>
{
public:
explicit BpAudioFlinger(const sp<IBinder>& impl)
: BpInterface<IAudioFlinger>(impl)
{
}
virtual status_t setMasterMute(bool muted)
{
Parcel data, reply;
data.writeInterfaceToken(IAudioFlinger::getInterfaceDescriptor());
data.writeInt32(muted);
//remote
remote()->transact(SET_MASTER_MUTE, data, &reply);
return reply.readInt32();
}
}2.1.6 BnAudioFlinger
通过reply写入返回值，调用BnAudioFlinger的setMasterMute方法
status_t BnAudioFlinger::onTransact(
uint32_t code, const Parcel& data, Parcel* reply, uint32_t flags)
{
switch (code) {
case SET_MASTER_MUTE: {
CHECK_INTERFACE(IAudioFlinger, data, reply);
reply->writeInt32( setMasterMute(data.readInt32()) );
return NO_ERROR;
} break;
}2.1.7 AudioFlinger setMasterMute逻辑
如果 hal 支持 setMasterMute 用hal的 不支持通过设置volume 0来实现，接下来我们先分析 hal的逻辑，本文主要是通过这个setMaserMute API来介绍Audio 模块给层级间关系，volume方式后续补充
AudioHwDevice *dev dev->hwDevice()->setMasterMute(muted); 通过loadHwModule拿到DeviceFactory生成
class AudioFlinger :
public BinderService<AudioFlinger>,
public BnAudioFlinger
{
virtual bool streamMute(audio_stream_type_t stream) const;
}
status_t AudioFlinger::setMasterMute(bool muted)
{
Mutex::Autolock _l(mLock);
mMasterMute = muted;
//如果 hal 支持 setMasterMute 用hal的 不支持通过设置volume 0来实现
// Set master mute in the HALs which support it.
//循环查找所有的hwdevice
for (size_t i = 0; i < mAudioHwDevs.size(); i++) {
AutoMutex lock(mHardwareLock);
AudioHwDevice *dev = mAudioHwDevs.valueAt(i);
mHardwareStatus = AUDIO_HW_SET_MASTER_MUTE;
if (dev->canSetMasterMute()) {
//调用到hal的加载
dev->hwDevice()->setMasterMute(muted);
}
mHardwareStatus = AUDIO_HW_IDLE;
}
//不支持通过设置volume 0来实现
// Now set the master mute in each playback thread. Playback threads
// assigned to HALs which do not have master mute support will apply master
// mute during the mix operation. Threads with HALs which do support master
// mute will simply ignore the setting.
Vector<VolumeInterface *> volumeInterfaces = getAllVolumeInterfaces_l();
for (size_t i = 0; i < volumeInterfaces.size(); i++) {
volumeInterfaces[i]->setMasterMute(muted);
}
return NO_ERROR;
}
//getMasterMute 最后在这返回mute状态
bool AudioFlinger::masterMute_l() const
{
return mMasterMute;
}2.2 AudioHAL加载
libAudioHAL是用于初始化Hal 加载的
之前AudioFlinger在构造函数里创建了DeviceFactory，来看看这个DeviceFactory怎么和hal层挂钩的
AudioFlinger::AudioFlinger()
: BnAudioFlinger(),
{
mDevicesFactoryHal = DevicesFactoryHalInterface::create();
}2.2.1 DevicesFactoryHalInterface create()
//DevicesFactoryHalInterface.h (f:\q\frameworks\av\media\libaudiohal\include\media\audiohal)
class DevicesFactoryHalInterface : public RefBase
{
virtual status_t openDevice(const char *name, sp<DeviceHalInterface> *device) = 0;
static sp<DevicesFactoryHalInterface> create();
}
//DevicesFactoryHalInterface.cpp
//三个 hal文件 IDeviceFactory.hal
#include <android/hardware/audio/2.0/IDevicesFactory.h>
#include <android/hardware/audio/4.0/IDevicesFactory.h>
#include <android/hardware/audio/5.0/IDevicesFactory.h>
#include <libaudiohal/FactoryHalHidl.h>
//优先级 5.0》 4.0 》 2.0 通过getService（固定API） 获取hal层service
sp<DevicesFactoryHalInterface> DevicesFactoryHalInterface::create() {
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;
}
//FactoryHalHidl.h 定义了3个命名空间
namespace V2_0 {
sp<DevicesFactoryHalInterface> createDevicesFactoryHal();
} // namespace V2_0
namespace V4_0 {
sp<DevicesFactoryHalInterface> createDevicesFactoryHal();
} // namespace V4_0
namespace V5_0 {
sp<DevicesFactoryHalInterface> createDevicesFactoryHal();
} // namespace V5_02.2.2 DevicesFactoryHalHybrid device工厂
DevicesFactoryHalHybrid 包含Local 和 Hidl，8.0之后优先Hidl，兼容Local
在这base为Q，就不分析Local，只梳理Hidl
class DevicesFactoryHalHybrid : public DevicesFactoryHalInterface
{
sp<DevicesFactoryHalInterface> createDevicesFactoryHal() {
return new DevicesFactoryHalHybrid();
}
}
// DevicesFactoryHalHybrid.cpp
DevicesFactoryHalHybrid::DevicesFactoryHalHybrid()
: mLocalFactory(new DevicesFactoryHalLocal()),
mHidlFactory(new DevicesFactoryHalHidl()) {
}
// openDevice流程
status_t DevicesFactoryHalHybrid::openDevice(const char *name, sp<DeviceHalInterface> *device) {
if (mHidlFactory != 0 && strcmp(AUDIO_HARDWARE_MODULE_ID_A2DP, name) != 0 &&
strcmp(AUDIO_HARDWARE_MODULE_ID_HEARING_AID, name) != 0) {
return mHidlFactory->openDevice(name, device);
}
return mLocalFactory->openDevice(name, device);
}2.2.3 DevicesFactoryHalHidl 实例化
//DevicesFactoryHalHidl.cpp
DevicesFactoryHalHidl::DevicesFactoryHalHidl() {
//获取hal层service
sp<IDevicesFactory> defaultFactory{IDevicesFactory::getService()};
if (!defaultFactory) {
ALOGE("Failed to obtain IDevicesFactory/default service, terminating process.");
exit(1);
}
// 将hal层 的IDeviceFactory 放入集合
mDeviceFactories.push_back(defaultFactory);
if (MAJOR_VERSION >= 4) {
// The MSD factory is optional and only available starting at HAL 4.0
sp<IDevicesFactory> msdFactory{IDevicesFactory::getService(AUDIO_HAL_SERVICE_NAME_MSD)};
if (msdFactory) {
mDeviceFactories.push_back(msdFactory);
}
}
for (const auto& factory : mDeviceFactories) {
// It is assumed that the DevicesFactoryHalInterface instance is owned
// by AudioFlinger and thus have the same lifespan.
factory->linkToDeath(HalDeathHandler::getInstance(), 0 /*cookie*/);
}
}
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