Comment 2 for bug 1209124

This bug seems to be affecting me as well. I have the same laptop as kanor mentions, the ASUS UX301LA. When the bluetooth device is blocked via rfkill, the hci0 device shows up properly under hciconfig. However, when the bluetooth device is unblocked, hci0 vanishes.

For example:

$ sudo rfkill block bluetooth
$ sudo rfkill list
0: phy0: Wireless LAN
 Soft blocked: no
 Hard blocked: no
1: asus-wlan: Wireless LAN
 Soft blocked: no
 Hard blocked: no
2: asus-bluetooth: Bluetooth
 Soft blocked: yes
 Hard blocked: no
5: hci0: Bluetooth
 Soft blocked: yes
 Hard blocked: no
$ sudo hciconfig -a
hci0: Type: BR/EDR Bus: USB
 BD Address: 5C:51:4F:0F:42:4E ACL MTU: 1021:5 SCO MTU: 96:5
 DOWN
 RX bytes:1016 acl:0 sco:0 events:104 errors:0
 TX bytes:16335 acl:0 sco:0 commands:103 errors:0
 Features: 0xff 0xfe 0x0f 0xfe 0xdb 0xff 0x7b 0x87
 Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3
 Link policy: RSWITCH HOLD SNIFF
 Link mode: SLAVE ACCEPT

$ sudo rfkill unblock bluetooth
$ sudo rfkill list
0: phy0: Wireless LAN
 Soft blocked: no
 Hard blocked: no
1: asus-wlan: Wireless LAN
 Soft blocked: no
 Hard blocked: no
2: asus-bluetooth: Bluetooth
 Soft blocked: no
 Hard blocked: no
$ sudo hciconfig -a
[no output]

What's even more interesting is that the device disappears from lsusb output:

$ sudo rfkill block bluetooth
$ sudo lsusb -d 8087:07dc
Bus 002 Device 007: ID 8087:07dc Intel Corp.
$ sudo rfkill unblock bluetooth
$ sudo lsusb -d 8087:07dc
[no output]

Relevant information:

$ dmesg | grep -i bluetooth
[ 9.128331] Bluetooth: Core ver 2.16
[ 9.128723] Bluetooth: HCI device and connection manager initialized
[ 9.128731] Bluetooth: HCI socket layer initialized
[ 9.128734] Bluetooth: L2CAP socket layer initialized
[ 9.128741] Bluetooth: SCO socket layer initialized
[ 9.135096] Bluetooth: BNEP (Ethernet Emulation) ver 1.3
[ 9.135100] Bluetooth: BNEP filters: protocol multicast
[ 9.135107] Bluetooth: BNEP socket layer initialized
[ 9.143738] Bluetooth: RFCOMM TTY layer initialized
[ 9.143751] Bluetooth: RFCOMM socket layer initialized
[ 9.143753] Bluetooth: RFCOMM ver 1.11
[ 10.067400] Bluetooth: hci0: read Intel version: 370710018002030d2e
[ 10.067404] Bluetooth: hci0: Intel device is already patched. patch num: 2e
[ 1112.489206] Bluetooth: hci0: read Intel version: 370710018002030d00
[ 1112.493990] Bluetooth: hci0: Intel Bluetooth firmware file: intel/ibt-hw-37.7.10-fw-1.80.2.3.d.bseq
[ 1112.645191] Bluetooth: hci0: Intel Bluetooth firmware patch completed and activated

$ uname -a
Linux zadkiel 3.11.0-15-generic #23-Ubuntu SMP Mon Dec 9 18:17:04 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux