I do some very simple LAPDm test.
Establishing link.
ms_to_bts_l1_cb: MS(us) -> BTS prim message
bts_to_ms_tx_cb: MS->BTS(us) message 29

Confirming
ms_to_bts_tx_cb: BTS->MS(us) message 9

Sending back to MS
ms_to_bts_tx_cb: BTS->MS(us) message 21
ms_to_bts_l1_cb: MS(us) -> BTS prim message

Sending back to BTS
ms_to_bts_l1_cb: MS(us) -> BTS prim message
bts_to_ms_tx_cb: MS->BTS(us) message 14
Success.