android电话接通状态下，关机铃声无法从外放输出

AudioMTKPolicyManager.cpp的startOutput方法中，将在newDevic获取到的后面添加：
if(stream==AudioSystem::BOOT)newDevice|=AUDIO_DEVICE_OUT_SPEAKER;
 
status_t AudioMTKPolicyManager::startOutput(audio_io_handle_t output,
                                             AudioSystem::stream_type stream,
                                             int session)
{
    ALOGD("startOutput() output %d, stream %d, session %d", output, stream, session);
    ......
    if (outputDesc->mRefCount[stream] == 1) {
        audio_devices_t newDevice = getNewDevice(output, false /*fromCache*/);
        routing_strategy strategy = getStrategy(stream);
        bool shouldWait = (strategy == STRATEGY_SONIFICATION) ||
                            (strategy == STRATEGY_SONIFICATION_RESPECTFUL);
        uint32_t waitMs = 0;
        bool force = false;
        if(stream==AudioSystem::BOOT) newDevice|=AUDIO_DEVICE_OUT_SPEAKER;
        for (size_t i = 0; i < mOutputs.size(); i++) {
            AudioOutputDescriptor *desc = mOutputs.valueAt(i);
            if (desc != outputDesc) {
                // force a device change if any other output is managed by the same hw
                // module and has a current device selection that differs from selected device.
                // In this case, the audio HAL must receive the new device selection so that it can
                // change the device currently selected by the other active output.
                if (outputDesc->sharesHwModuleWith(desc) &&
                    desc->device() != newDevice) {
                    force = true;
                }
                // wait for audio on other active outputs to be presented when starting
                // a notification so that audio focus effect can propagate.
                uint32_t latency = desc->latency();
                if (shouldWait && desc->isActive(latency * 2) && (waitMs < latency)) {
                    waitMs = latency;
                }
            }
        }
      ......      
    }
    return NO_ERROR;
}