gsm_lchan2chan_nr(): separate RSL specific variant of this API

The ip.access style dynamic timeslots are a bit special in a way that
on the A-bis/RSL we always use the Channel Number value of TCH/F,
even in PDCH mode.  This is why gsm_lchan2chan_nr() would always
return values corresponding to TCH/F for TCH/F_PDCH.

This behavior is only acceptable in the context of RSL messages, while
other parts of the code base may not work properly due to this trick.
A good example is the scheduler in osmo-bts-trx, where we have to
patch Channel Number value to make channel activation work.

  DPCU INFO pcu_sock.c:853 Activate request received: TRX=0 TS=5
  DL1C INFO l1sap.c:2043 (bts=0,trx=0,ts=5,ss=0) Activating channel TCH/F on TS5
  DL1C NOTICE scheduler.c:1097 (bts=0,trx=0,ts=5,ss=0) Activating PDTCH
  DL1C NOTICE scheduler.c:1097 (bts=0,trx=0,ts=5,ss=0) Activating PTCCH

In the code branch responsible for channel deactivation, we somehow
forgot to add the same workaround, so deactivation does not work:

  DL1C INFO l1sap.c:2076 (bts=0,trx=0,ts=5,ss=0) Deactivating channel TCH/F on TS5
  DTRX INFO trx_if.c:255 phy0.0: Enqueuing TRX control command 'CMD NOHANDOVER 5 0'
  DRSL NOTICE rsl.c:1286 (bts=0,trx=0,ts=5,ss=0) (bts=0,trx=0,ts=5,ss=0) not sending REL ACK

Because of that, TCH/F_PDCH timeslots actually remain active after
deactivation, so the scheduler keeps producing L1SAP DATA.ind.

  DL1P NOTICE l1sap.c:126 (bts=0,trx=0,ts=5,ss=0) assuming active lchan, but state is NONE
  DL1P ERROR l1sap.c:732 1583426/1194/00/29/14 No lchan for DATA MEAS IND (chan_nr=PDCH on TS5)
  DPCU NOTICE pcu_sock.c:973 PCU socket not connected, dropping message
  DL1P NOTICE l1sap.c:126 (bts=0,trx=0,ts=5,ss=0) assuming active lchan, but state is NONE
  DPCU NOTICE pcu_sock.c:973 PCU socket not connected, dropping message
  DL1P NOTICE l1sap.c:126 (bts=0,trx=0,ts=5,ss=0) assuming active lchan, but state is NONE
  DL1P ERROR l1sap.c:732 1583430/1194/04/33/18 No lchan for DATA MEAS IND (chan_nr=PDCH on TS5)
  DPCU NOTICE pcu_sock.c:973 PCU socket not connected, dropping message
  DL1P NOTICE l1sap.c:126 (bts=0,trx=0,ts=5,ss=0) assuming active lchan, but state is NONE
  DPCU NOTICE pcu_sock.c:973 PCU socket not connected, dropping message

Instead of patching Channel Number in various places, let's rather
make the RSL specific behavior configurable by having two variants
of gsm_lchan2chan_nr().

Change-Id: I01680140c7201bf5284b278bceaea8ae01c122b2
Fixes: OS#5238

1 files changed, 1 insertions, 0 deletions

diff --git a/include/osmo-bts/gsm_data.h b/include/osmo-bts/gsm_data.h
index 9fe68d63..19689e54 100644
--- a/include/osmo-bts/gsm_data.h
+++ b/include/osmo-bts/gsm_data.h
@@ -568,6 +568,7 @@ static inline char *gsm_lchan_name(const struct gsm_lchan *lchan)
 }
 
 uint8_t gsm_lchan2chan_nr(const struct gsm_lchan *lchan);
+uint8_t gsm_lchan2chan_nr_rsl(const struct gsm_lchan *lchan);
 uint8_t gsm_lchan_as_pchan2chan_nr(const struct gsm_lchan *lchan,
 				   enum gsm_phys_chan_config as_pchan);