osmo-bsc/doc/ts-and-lchan-fsm-lifecycle.msc

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msc {
hscale=2;
bts [label="MS/BTS"], bsc[label="BSC"], bsc_ts[label="BSC timeslot FSM"], bsc_lchan[label="BSC lchan FSM"];
bsc box bsc [label="gsm_bts_alloc()"];
bsc box bsc [label="bts->c0 = gsm_bts_trx_alloc()"];
bsc -> bsc_ts;
bsc_ts box bsc_ts [label="trx->ts[*].fi = osmo_fsm_inst_alloc(timeslot_fsm)"];
bsc_ts abox bsc_ts [label="TS_ST_NOT_INITIALIZED"];
bsc -> bsc_lchan;
bsc_lchan box bsc_lchan [label="ts->lchan[*].ts = ts;\nts->lchan[*].nr = i;"];
bsc_lchan box bsc_lchan [label="ts->lchan[*].fi = NULL"];
bsc_ts note bsc_lchan [label="lchan_select() will only pick lchans from initialized timeslots of
the right pchan kind. lchan_select() shall OSMO_ASSERT(lchan->fi)."];
...;
...;
bts rbox bsc_lchan [label="reading config file"];
...;
bsc box bsc [label="timeslot N"];
bsc box bsc [label="phys_chan_config X"];
bsc_ts box bsc_ts [label="ts->pchan_from_config = X"];
bsc_ts note bsc_ts [label="still TS_ST_NOT_INITIALIZED"];
...;
bsc box bsc [label="trx 1..*"];
bsc box bsc [label="bts->trx_list add gsm_bts_trx_alloc()"];
bsc_ts rbox bsc_lchan [label="same as for c0 above"];
...;
...;
bts rbox bsc_lchan [label="Starting Operation"];
bts => bsc_ts [label="OML Channel OPSTART ACK"];
bsc_ts box bsc_ts [label="ts_on_oml_opstart()"];
bsc_ts box bsc_ts [label="ts->pchan_on_init = pchan_from_config"];
--- [label="IF dedicated TS"];
bsc_ts box bsc_ts [label="ts->pchan = ts->pchan_on_init"];
--- [label="ELSE: dyn TS"];
bsc_ts box bsc_ts [label="ts->pchan = NONE"];
--- [label="END: dyn TS"];
bsc_ts note bsc_lchan [label="Normally, the lchan FSM never terminates. Logic dictates that
the lchan is a child of the timeslot FSM, but it's not actually of functional importance
beyond basic sanity. Parent term event: TS_EV_LCHAN_UNUSED"];
bsc_ts box bsc_ts [label="Determine N = maximum number of lchans applicable to pchan_on_init"];
bsc_ts -> bsc_lchan;
bsc_lchan box bsc_lchan [label="ts->lchan[all N].type = osmo_fsm_inst_alloc(lchan_fsm)"];
bsc_lchan abox bsc_lchan [label="LCHAN_ST_UNUSED\n(initial state)"];
bsc_ts -> bsc_ts [label="ts_check_init()"];
...;
bsc -> bsc_ts [label="RSL bootstrapped"];
bsc_ts -> bsc_ts [label="ts_check_init()"];
...;
bsc_ts box bsc_ts [label="ts_check_init()"];
--- [label="as soon as both OML and RSL are ready:"];
bsc_ts box bsc_ts [label="ts_on_init()"];
bsc_ts abox bsc_ts [label="TS_ST_UNUSED"];
--- [label="dyn TS"];
bsc_ts box bsc_ts [label="onenter of TS_ST_UNUSED:"];
bsc_ts abox bsc_ts [label="TS_ST_WAIT_PDCH_ACT"];
... [label="..."];
bsc_ts abox bsc_ts [label="PDCH"];
--- [label="END: dyn TS"];
--- [label="END: OML and RSL ready"];
...;
bsc box bsc [label="lchan_select() picks an unused lchan"];
bsc -> bsc_lchan [label="lchan_allocate()"];
bsc_lchan -> bsc_ts [label="TS_EV_LCHAN_REQUESTED"];
--- [label="dyn TS"];
bsc_ts rbox bsc_ts [label="possibly switch from PDCH...\n(see timeslot FSM)"];
bsc_ts box bsc_ts [label="ts->pchan =\n requested GSM_PCHAN_XXX type"];
---;
bsc_ts -> bsc_lchan [label="LCHAN_EV_TS_READY"];
bsc_lchan note bsc_lchan [label="RSL Chan Alloc and so fort..."];
bsc_lchan abox bsc_lchan [label="LCHAN_ST_ESTABLISHED"];
...;
bsc -> bsc_lchan [label="LCHAN_EV_RELEASE"];
bsc_lchan note bsc_lchan [label="...RSL RF Chan Release..."];
bsc_lchan abox bsc_lchan [label="LCHAN_ST_UNUSED"];
bsc_ts <- bsc_lchan [label="TS_EV_LCHAN_UNUSED"];
bsc_ts abox bsc_ts [label="TS_ST_UNUSED"];
--- [label="dyn TS"];
bsc_ts rbox bsc_ts [label="possibly switch to PDCH"];
---;
...;
...;
bts rbox bsc_lchan [label="BTS RSL is dropped"];
bsc box bsc [label="ipaccess_drop_rsl()"];
bsc -> bsc_ts [label="ts[*]:"];
bsc_ts abox bsc_ts [label="TS_ST_NOT_INITIALIZED"];
bsc_ts note bsc_lchan [label="If it's just the RSL being dropped, transition lchan FSMs to
LCHAN_ST_UNUSED, but keep them allocated. Unless OML is re-established, any telnet
vty pchan modifications must not take effect."];
bsc_ts -> bsc_lchan [label="lchan[*]:"];
bsc_lchan abox bsc_lchan [label="LCHAN_ST_UNUSED"];
bsc_ts <- bsc_lchan [label="TS_EV_LCHAN_UNUSED (ignored)"];
...;
--- [label="when RSL comes back later:"];
bsc -> bsc_ts [label="RSL bootstrapped"];
bsc_ts box bsc_ts [label="ts_check_init()"];
bsc_ts rbox bsc_ts [label="see ts_check_init() above"];
...;
...;
bts rbox bsc_lchan [label="BTS OML is dropped"];
bsc note bsc [label="As part of OML drop, RSL is also dropped:"];
bsc box bsc [label="ipaccess_drop_rsl()"];
bsc -> bsc_ts [label="ts[*]:"];
bsc_ts abox bsc_ts [label="TS_ST_NOT_INITIALIZED"];
bsc rbox bsc [label="see 'BTS RSL is dropped' above"];
bsc -> bsc_ts [label="ts[*]:"];
bsc_ts -> bsc_lchan [label="lchan[*]:"];
bsc_lchan box bsc_lchan [label="osmo_fsm_inst_term()"];
bsc_ts <- bsc_lchan [label="TS_EV_LCHAN_UNUSED (ignored)"];
bsc_lchan box bsc_lchan [label="lchan->fi = NULL"];
bsc rbox bsc [label="Continue at 'Starting Operation'"];
}