services/audiopolicy/config/primary_audio_policy_configuration.xml

<?xml version="1.0" encoding="UTF-8"?>
<!-- Default Primary Audio HAL Module Audio Policy Configuration include flie -->
<module name="primary" halVersion="2.0">
    <attachedDevices>
        <item>Speaker</item>
        <item>Built-In Mic</item>
    </attachedDevices>
    <defaultOutputDevice>Speaker</defaultOutputDevice>
    <mixPorts>
        <mixPort name="primary output" role="source" flags="AUDIO_OUTPUT_FLAG_PRIMARY">
            <profile name="" format="AUDIO_FORMAT_PCM_16_BIT"
                     samplingRates="44100" channelMasks="AUDIO_CHANNEL_OUT_STEREO"/>
        </mixPort>
        <mixPort name="primary input" role="sink">
            <profile name="" format="AUDIO_FORMAT_PCM_16_BIT"
                     samplingRates="8000, 16000" channelMasks="AUDIO_CHANNEL_IN_MONO"/>
        </mixPort>
   </mixPorts>
   <devicePorts>
        <devicePort tagName="Speaker" type="AUDIO_DEVICE_OUT_SPEAKER" role="sink">
        </devicePort>

        <devicePort tagName="Built-In Mic" type="AUDIO_DEVICE_IN_BUILTIN_MIC" role="source">
        </devicePort>
    </devicePorts>
    <routes>
        <route type="mix" sink="Speaker"
               sources="primary output"/>
        <route type="mix" sink="primary input"
               sources="Built-In Mic"/>
    </routes>
</module>