Comment 46 for bug 1221995

this bug cause kernel module btusb not autoload.

$ lsb_release --all
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 14.04.2 LTS
Release: 14.04
Codename: trusty

$ uname -r
3.16.0-31-generic

$ lsusb | grep Bluetooth
Bus 007 Device 002: ID 0a12:0001 Cambridge Silicon Radio, Ltd Bluetooth Dongle (HCI mode)

$ hciconfig

$ hcitool scan
Device is not available: No such device

$ lsmod |grep btusb

$ sudo modprobe btusb

$ lsmod |grep btusb
btusb 32497 0
bluetooth 446409 22 bnep,btusb,rfcomm

$ hcitool dev
Devices:
 hci0 00:1A:7D:DA:71:10

good luck .