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Neels Hofmeyr nhofmeyr at sysmocom.deOn Thu, Jul 21, 2016 at 12:38:25PM +0200, Harald Welte wrote: > Hi Neels, > > [posting to the openbsc mailing list, as this discussion is not GPRS > related] > > On Thu, Jul 21, 2016 at 12:25:25PM +0200, Neels Hofmeyr wrote: > > On Wed, Jul 20, 2016 at 06:50:24PM +0200, Max wrote: > > > It's called from lchan_act_compl_cb() via sapi_queue_send() which is > > > also in mph_send_activate_req() - I have hard time understanding how > > > this works at all. Do we have this documented somewhere? > > > > Both the TCH/F_TCH/H_PDCH timeslot feature and the TCH/F_PDCH on osmo-trx > > are stuck on some post-lchan_act_compl SAPI stuff. > > can you be more specific about what "stuff"? It's hard to be of > assistance without details. Well, I kind of feel that I should be able to find out myself, so I kept my remark at a distance. But since you were so fast to reply and I am indeed a bit stuck in a stupid way... I'll focus on TCH/F_TCH/H_PDCH: GPRS works, but placing a TCH/H call doesn't. The pchan switchover dance is complete, but then the new TCH/H channel is not working. I notice that on a dyn TS just after switchover, log entries starting with "SAPI=0" are missing *on the BSC side*, when compared to a pure TCH/H: DRSL <0004> abis_rsl.c:1462 (bts=0,trx=0,ts=2,ss=0) CHANNEL ACTIVATE ACK DRSL <0004> abis_rsl.c:1133 (bts=0,trx=0,ts=2,ss=0) state ACTIVATION REQUESTED -> ACTIVE DRLL <0000> abis_rsl.c:1913 (bts=0,trx=0,ts=2,ss=0) SAPI=0 ESTABLISH INDICATION ^ missing for dyn TS DRLL <0000> gsm_04_08.c:3667 Dispatching 04.08 message, pdisc=5 DMM <0002> gsm_04_08.c:987 <- CM SERVICE REQUEST serv_type=0x01 MI(TMSI)=300151278 DMM <0002> gsm_04_08_utils.c:681 -> CM SERVICE ACK DRLL <0000> abis_rsl.c:1913 (bts=0,trx=0,ts=2,ss=0) SAPI=0 DATA INDICATION DRLL <0000> abis_rsl.c:1913 (bts=0,trx=0,ts=2,ss=0) SAPI=0 DATA INDICATION DRR <0003> bsc_api.c:647 BSC: Passing unknown 04.08 RR message type 0x60 to MSC DRLL <0000> gsm_04_08.c:3667 Dispatching 04.08 message, pdisc=6 DRR <0003> gsm_04_08.c:1281 MSC: Unimplemented GSM 04.08 RR msg type 0x60 DRLL <0000> abis_rsl.c:1913 (bts=0,trx=0,ts=2,ss=0) SAPI=0 DATA INDICATION DRLL <0000> abis_rsl.c:1913 (bts=0,trx=0,ts=2,ss=0) SAPI=0 DATA INDICATION The first one missing for a dyn TS is: DRLL <0000> abis_rsl.c:1913 (bts=0,trx=0,ts=2,ss=0) SAPI=0 ESTABLISH INDICATION So I tried to find its root. The log on the BSC is from receiving an RLL message from the BTS, so I tried to find out where it's sent in the BTS: * BSC: abis_rsl_rx_rll(): case RSL_MT_EST_IND * libosmocore/src/gsm/lapdm.c:421: send_rslms_dlsap(): case OSMO_PRIM(PRIM_DL_EST, PRIM_OP_INDICATION): [...] rll_msg = RSL_MT_EST_IND; * libosmocore/src/gsm/lapd_core.c:788: prim = PRIM_DL_EST; And there I seem to be in a very general area with lots of callers. I feel a bit stupid not to be able to see it, and my knowledge is really lacking... so I could use a noob nudge in the right direction there, or maybe a really coarse picture of what I'm talking about in the first place. My guess goes at sapi_queue_exeute() at the moment, but I'm not seeing the connections yet. BTW, the second TCH/H on a dynamic channel seems to be established successfully, so I'm probably clearing some lchan state during pchan switchover, but can't put my finger on it yet. Thanks, ~Neels > > > So, I would also benefit from better understanding the actions after > > lchan_act. > > I actually think the L1 SAPI activation/deactivation is rather simple. > You have the tables that list the SAPI+Direction combinations needed for > every lchan type (what I just quoted for PDCH in my recent mail), and > then the code iterates over the list of SAPI+Direction at time of lchan > activation or deactivation. > > > Apparently related: libosmocore/gsm/lapd*.c > > How are the SAPIs of the data link layer should be related to SAPIs of > the physical layer? > > LAPDm is establishing reliable channels over the already established > physical layer, and LAPDm is not by iself activating/deactivating any > channels, i.e. not talking to the MPH-SAP. > > -- > - Harald Welte <laforge at gnumonks.org> http://laforge.gnumonks.org/ > ============================================================================ > "Privacy in residential applications is a desirable marketing option." > (ETSI EN 300 175-7 Ch. A6) -- - Neels Hofmeyr <nhofmeyr at sysmocom.de> http://www.sysmocom.de/ ======================================================================= * sysmocom - systems for mobile communications GmbH * Alt-Moabit 93 * 10559 Berlin, Germany * Sitz / Registered office: Berlin, HRB 134158 B * Geschäftsführer / Managing Directors: Harald Welte -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 819 bytes Desc: Digital signature URL: <http://lists.osmocom.org/pipermail/openbsc/attachments/20160721/a07f0a13/attachment.bin>