BlueZ on i.MX25 : Can't connect RFCOMM socket: Operation now in progress

Question

I'm trying to connect to a bluetooth device on embedded linux.

• BlueZ version is 4.101.
• Local bluetooth adapter is an USB Bluetooth dongle Trendnet TBW-107UB, for all tests.
• I can't provide details about the target device, as it is a product of the company I work for, sorry.

Using the method described at this page works fine on Desktop Linux Mint 17 x64, and on RiotBoard (i.MX6) Linaro Ubuntu.

However, I can't get an i.MX25 board (embedded custom Linux) to connect to the target device. Only scan works.

rfcomm.conf

rfcomm0 {
    # Automatically bind the device at startup
    bind yes;

    # Bluetooth address of the device
    device 00:07:80:5A:48:93;

    # RFCOMM channel for the connection
    channel 1;

    # Description of the connection
    comment "Example Bluetooth device";
}

hciconfig -a output

hci0:   Type: BR/EDR  Bus: USB  
    BD Address: 00:15:83:44:39:E2  ACL MTU: 384:8  SCO MTU: 64:8  
    UP RUNNING PSCAN  
    RX bytes:28633 acl:0 sco:0 events:204 errors:0  
    TX bytes:899 acl:0 sco:0 commands:60 errors:0  
    Features: 0xff 0xff 0x8f 0xfe 0x9b 0xff 0x59 0x83  
    Packet type: DM1 DM3 DM5 DH1 DH3 DH5 HV1 HV2 HV3  
    Link policy: RSWITCH HOLD SNIFF PARK  
    Link mode: SLAVE ACCEPT  
    Name: 'Bluetooth2.1+EDR CLASS1'  
    Class: 0x000000  
    Service Classes: Unspecified  
    Device Class: Miscellaneous,  
    HCI Version: 2.1 (0x4)  Revision: 0x149c  
    LMP Version: 2.1 (0x4)  Subversion: 0x149c  
    Manufacturer: Cambridge Silicon Radio (10)  

rfcomm connect output

# rfcomm connect 0  
Can't connect RFCOMM socket: Operation now in progress  

hcitool cc output

# hcitool cc 00:07:80:5A:48:93  
Can't create connection: Connection timed out

l2ping output

# l2ping 00:07:80:5A:48:93  
Can't connect: Invalid exchange

While google searching, the only relevant thread I could find suggests that the rfcomm connect output could be due to a kernel 2.6.27 regression, but mine is 3.10.28 (used uname -r).
I tried with two other target bluetooth devices (of different type), the problem remains the same.

Any help is appreciated, thank you!

Edit
Rfkill block / unblock didn't seem to change anything.

Solution

It turns out the target device was requesting authentication from my i.MX25 board.
Usually, PIN code handling is done by using bluetooth-agent.
But this agent wasn't actually installed on the board (I thought it was...), so I had to manually provide the requested PIN code.

This is how I did it :

• edit /etc/bluetooth/rfcomm.conf, like I previously did
• "Up" the local bt adapter : hciconfig 0 up
• Enable page & inquiry scanning : hciconfig 0 piscan (I'm not sure about this one)
• Disable simple pairing : hciconfig 0 sspmode 0
• Edit (or create) /usr/var/lib/bluetooth/00:15:83:44:39:E2/pincodes
• In "pincodes" files, add line (no quotes) : "00:07:80:5A:48:93 045678"
• Manually start bluetooth daemon : bluetoothd

00:15:83:44:39:E2 is local device bluetooth address.
00:07:80:5A:48:93 is target device bluetooth address.
045678 is target device PIN code.

l2ping works :

# l2ping 00:07:80:5A:48:93
Ping: 00:07:80:5A:48:93 from 00:15:83:44:39:E2 (data size 44) ...
4 bytes from 00:07:80:5A:48:93 id 0 time 13.14ms
4 bytes from 00:07:80:5A:48:93 id 1 time 26.34ms

rfcomm connect works :

# rfcomm connect 0
Connected /dev/rfcomm0 to 00:07:80:5A:48:93 on channel 1
Press CTRL-C for hangup

Update 06.15.2015

Today I tried l2ping on that target device again, as previously described. For some reason, it would throw me a "Permission denied" error.
This is what I figured out as a workaround :

• Save /usr/var/lib/bluetooth/00:15:83:44:39:E2/pincodes somewhere else
• Remove everything under /usr/var/lib/bluetooth/00:15:83:44:39:E2
• Reboot
• Put your saved pincodes file back under /usr/var/lib/bluetooth/00:15:83:44:39:E2
• Retry pinging as previously described