Change in osmo-bsc[master]: lchan and assignment FSMs: make Channel Mode Modify more sane

neels gerrit-no-reply at
Fri Apr 30 14:26:58 UTC 2021

Hello Jenkins Builder, fixeria, 

I'd like you to reexamine a change. Please visit

to look at the new patch set (#3).

Change subject: lchan and assignment FSMs: make Channel Mode Modify more sane

lchan and assignment FSMs: make Channel Mode Modify more sane

The Channel Mode Modify procedure is currently implemented for changing
a TCH lchan from signalling to voice mode. For that, however, it is
re-using (abusing) the channel activation structs and state transitions,
and thus always implies activating a voice stream when the mode
modification is done.

I will add a Channel Mode Modify to enable VAMOS mode soon, so I require
separate structs and state transitions which also work on an lchan that
already has a voice stream established: a struct lchan_modify_info and
LCHAN_EV_REQUEST_MODE_MODIFY, and dedicated assignment FSM state

For the part where a Channel Mode Modify enables a voice stream after
switching from signalling to speech mode, still use the channel
activation code path, but only once the mode modification is done.

General improvements:
- To ask for a mode modification, emit an FSM event that ensures a mode
  modify only happens when the lchan state allows it.
- The new lchan_modify_info struct reflects only those parts that have
  an effect during a mode modification (before the lchan_activate_info
  was fully populated, many values not having an effect).
- More accurate logging, indicating "Mode Modify" instead of "Channel

A TTCN3 test for the Channel Mode Modify procedure is added in
Idf4efaed986de0bbd2b663313e837352cc139f0f, and the test passes both
before and after this patch is applied.

Related: SYS#4895
Change-Id: I4986844f839b1c9672c61d916eb3d33d0042d747
M doc/
M include/osmocom/bsc/assignment_fsm.h
M include/osmocom/bsc/gsm_data.h
M include/osmocom/bsc/lchan_fsm.h
M src/osmo-bsc/assignment_fsm.c
M src/osmo-bsc/lchan_fsm.c
6 files changed, 202 insertions(+), 67 deletions(-)

  git pull ssh:// refs/changes/43/23943/3
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Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Change-Id: I4986844f839b1c9672c61d916eb3d33d0042d747
Gerrit-Change-Number: 23943
Gerrit-PatchSet: 3
Gerrit-Owner: neels <nhofmeyr at>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: fixeria <vyanitskiy at>
Gerrit-MessageType: newpatchset
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