MSC split: is_siemens_bts() in libmsc/gsm_04_08.c / conn->bts vs. lchan->ts->trx->bts

[Neels Hofmeyr]

I'm trying to get rid of all BTS backpointers in libmsc.

In libmsc/gsm_04_08.c, in gsm48_rx_mm_serv_req(), I find:

        if (is_siemens_bts(bts))
                        send_siemens_mrpci(msg->lchan, classmark2-1);

My conclusion so far is that this "hook" should move to the BSC code, but
I could use some comforting approval by more apt contenders... Some
detail:


send_siemens_mrpci() is found in libbsc/gsm_04_08_utils.c:


  int send_siemens_mrpci(struct gsm_lchan *lchan,
                         uint8_t *classmark2_lv)
  {
          struct rsl_mrpci mrpci;

          if (classmark2_lv[0] < 2)
                  return -EINVAL;

          mrpci.power_class = classmark2_lv[1] & 0x7;
          mrpci.vgcs_capable = classmark2_lv[2] & (1 << 1);
          mrpci.vbs_capable = classmark2_lv[2] & (1 <<2);
          mrpci.gsm_phase = (classmark2_lv[1]) >> 5 & 0x3;

          return rsl_siemens_mrpci(lchan, &mrpci);
  }


IIUC the Siemens BS11 BTS needs to be tickled with a vendor-specific RSL
message as soon as a CM service request (GSM48_MT_MM_CM_SERV_REQ) or a paging
response is received from a subscriber.

Only the BSC knows which BTS is involved, so I'd try to find some place in
libbsc/ or osmo-bsc/ to move this away to.

The same function is called from gsm48_handle_paging_resp() in libbsc.

Any shortcuts / workarounds or could this also be dropped entirely?
It does look like that particular case is indeed missing from osmo-bsc.
Who is this Mister PCI anyway? ;)


The gsm48_handle_paging_resp() function leads me to another, more general
question: often, there are two bts pointers around, namely the
  gsm_subscriber_connection->bts
as well as the
  lchan->ts->trx->bts
Are these typically/always/never expected to be the same bts struct?
(In this function, both bts pointers are used, and I'd like to understand why.)


Thanks!
~Neels


-- 
- Neels Hofmeyr <nhofmeyr at sysmocom.de>          http://www.sysmocom.de/
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