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
ASSIGNMENT_ST_WAIT_LCHAN_MODIFIED.
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
Activation"
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
d5cb0eb8fd