BlueZ which layer get reason of Bluetooth disconnection

Question

I am using BlueZ stack for Bluetooth connection between Smart-phone(AG-Audio Gateway) and Embedded board(HF-Handsfree).

On which layer of Bluez ( HCI, L2CAP, RFCOMM) we will get reason of Bluetooth disconnection. So we can differentiate following type of disconnection:

1. Smart-Phone SIMPLE DISCONNECT, but phone is still have HF Embedded device in its paired list.
2. Smart-Phone FORGET HF device during bluetooth connection.
3. Disconnection because HF device went out of Smart-Phone bluetooth Range

Answer 1

HCI: Disconnection Complete Event, check the Reason byte.