Wi-Fi framework for P2P in android

1.Settings (packages/apps/Settings)
2.Wi-Fi service framework (frameworks/base/wifi/java/android/net/wifi, frameworks/base/services/java/com/android/server)
3.Wi-Fi HAL (hardware/libhardware_legacy/wifi)
4.wpa_supplicant_8 (external/wpa_supplicant_8)
5.netlink library (external/libnl_2)
6.nl80211/cfg80211 driver

volume control

frameworks/base/media/libmedia/AudioSystem.cpp

status_t AudioSystem::setStreamVolumeIndex(stream_type stream, int index)
{
    const sp& aps = AudioSystem::get_audio_policy_service();
    if (aps == 0) return PERMISSION_DENIED;
    return aps->setStreamVolumeIndex(stream, index);
}