【Android Audio】4、音频设备管理 【基于Android Q 】_listaudioports

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audio policy xml里面有2种角色：source和sink，每种角色又分为devicePorts和mixPorts。

type为AUDIO_PORT_TYPE_DEVICE
devicePorts(source)：为实际的硬件输入设备，对应安卓的role为AUDIO_PORT_ROLE_SOURCE ；
devicePorts(sink)：为实际的硬件输出设备，对应安卓的role为AUDIO_PORT_ROLE_SINK ；

type为AUDIO_PORT_TYPE_MIX
mixPorts(source)：为AudioFlinger中的播放（AudioTrack）的线程，对应安卓的role为AUDIO_PORT_ROLE_SOURCE，mOutputs；
mixPorts(sink)：为AudioFlinger中的录音（AudioRecord）的线程，对应安卓的role为AUDIO_PORT_ROLE_SINK，mInputs

routes：定义devicePort和mixPorts的路由策略。

通过该接口AudioSystem.listAudioPorts可获取到当前所有的端口

status_t AudioPolicyManager::listAudioPorts(audio_port_role_t role,
                                            audio_port_type_t type,
                                            unsigned int *num_ports,
                                            struct audio_port *ports,
                                            unsigned int *generation)
{
   
...
    if (type == AUDIO_PORT_TYPE_NONE || type == AUDIO_PORT_TYPE_DEVICE) {
   
        // do not report devices with type AUDIO_DEVICE_IN_STUB or AUDIO_DEVICE_OUT_STUB
        // as they are used by stub HALs by convention
        if (role == AUDIO_PORT_ROLE_SINK || role == AUDIO_PORT_ROLE_NONE) {
   
            for (const auto& dev : mAvailableOutputDevices) {
   
                if (dev->type() == AUDIO_DEVICE_OUT_STUB) {
   
                    continue;
                }
                if (portsWritten < portsMax) {
   
                    dev->toAudioPort(&ports[portsWritten++]);
                    ALOGD("[%s:%d] output device role:%d, name:%s, type:%#x", __func__, __LINE__,
                        ports[portsWritten-1].role, ports[portsWritten-1].name, ports[portsWritten-1].ext.device.type);
                }
                (*num_ports)++;
            }
        }
        if (role == AUDIO_PORT_ROLE_SOURCE || role == AUDIO_PORT_ROLE_NONE) {
   
            for (const auto& dev : mAvailableInputDevices) {
   
                if (dev->type() == AUDIO_DEVICE_IN_STUB) {
   
                    continue;
                }
                if (portsWritten < portsMax) {
   
                    dev->toAudioPort(&ports[portsWritten++]);
                    ALOGD("[%s:%d] input device role:%d, name:%s, type:%#x", __func__, __LINE__,
                        ports[portsWritten-1].role, ports[portsWritten-1].name, ports[portsWritten-1].ext.device.type);
                }
                (
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