Workaround for buggy BT dongles

Workaround for buggy BT dongles

[Andrei Emeltchenko]

Hi,

We have experienced L2CAP disconnections with A-Link BT dongles (lsusb
shows Broadcom Corp. BCM2046B1 chip).

There is race condition in a controller so that sometimes "L2CAP
Connect Req" is received after "HCI Encryption Change":
...
2308 *REF*                                                   HCI_EVT
Simple Pairing Complete
2309 0.089720                                                HCI_EVT
Link Key Notification
2310 0.126607                                                L2CAP
Rcvd Connection Request
2311 0.126721                                                L2CAP
Sent Connection Response
2312 0.127278                                                HCI_EVT
Encrypt Change
...

This is correct behavior since all non-SDP connections shall be
encrypted for SSP devices.

If we send "L2CAP Connect Request" with a little delay the problem
disappears (this is of course too hackish way).

Shall we address this problem? I do not see good way of dealing with the chip.

Regards,
Andrei

Re: Workaround for buggy BT dongles

[Marcel Holtmann]

Hi Andrei,

> We have experienced L2CAP disconnections with A-Link BT dongles (lsusb
> shows Broadcom Corp. BCM2046B1 chip).
> 
> There is race condition in a controller so that sometimes "L2CAP
> Connect Req" is received after "HCI Encryption Change":
> ...
> 2308 *REF*                                                   HCI_EVT
> Simple Pairing Complete
> 2309 0.089720                                                HCI_EVT
> Link Key Notification
> 2310 0.126607                                                L2CAP
> Rcvd Connection Request
> 2311 0.126721                                                L2CAP
> Sent Connection Response
> 2312 0.127278                                                HCI_EVT
> Encrypt Change
> ...
> 
> This is correct behavior since all non-SDP connections shall be
> encrypted for SSP devices.
> 
> If we send "L2CAP Connect Request" with a little delay the problem
> disappears (this is of course too hackish way).
> 
> Shall we address this problem? I do not see good way of dealing with the chip.

I would prefer to address this problem as follows. Open your window and
through the dongle out that same window ;)

Regards

Marcel