doc/timeslot.msc

msc {
	hscale=2;
	bts [label="MS/BTS"], bsc[label="BSC"], bsc_ts[label="BSC timeslot FSM"], bsc_lchan[label="BSC lchan FSM"];

	bsc_ts abox bsc_ts [label="NOT_INITIALIZED (no timeout)"];

	...;
	bsc note bsc_ts [label="OML and RSL may be established in any order"];
	bts => bsc_ts [label="OML: Channel OPSTART ACK"];
	bsc -> bsc_ts [label="RSL bootstrapped"];
	bsc_ts abox bsc_ts [label="UNUSED (no timeout)"];

	|||;
	bts rbox bsc_lchan [label="UNUSED, onenter"];
	bsc_ts abox bsc_ts [label="UNUSED"];
	--- [label="GPRS enabled?"];
	--- [label="IF: dedicated PDCH?"];
	bsc_ts abox bsc_ts [label="PDCH (no timeout)"];

	|||;
	--- [label="IF: dynamic timeslot"];
	bsc_ts abox bsc_ts [label="WAIT_PDCH_ACT (?s, Tnnnn)"];
	bts <= bsc_ts [label="RSL Chan Activ of PDCH",ID="Osmocom style"];
	bts <= bsc_ts [label="RSL PDCH Act",ID="ip.access style"];
	...;
	--- [label="timeout:"];
	bsc_ts abox bsc_ts [label="BORKEN"];
	---;
	...;
	bts => bsc_ts [label="RSL RF Chan Activ ACK",ID="Osmocom style"];
	bts => bsc_ts [label="RSL PDCH Act ACK",ID="ip.access style"];
	bsc_ts abox bsc_ts [label="PDCH (no timeout)"];

	--- [label="END: GPRS enabled?"];
	...;
	...;

	bts rbox bsc_lchan [label="UNUSED, on event"];
	bsc_ts abox bsc_ts [label="UNUSED"];
	bsc_ts <- bsc_lchan [label="TS_EV_LCHAN_REQUESTED (data=lchan)"];
	bsc_ts abox bsc_ts [label="IN_USE"];
	bsc_ts -> bsc_lchan [label="LCHAN_EV_TS_READY"];
	bts <= bsc_lchan [label="RSL Chan Activ (and so on)"];
	...;
	bts rbox bsc_lchan [label="IN_USE, second lchan"];
	bsc_ts <- bsc_lchan [label="TS_EV_LCHAN_REQUESTED (data=lchan)"];
	bsc_ts -> bsc_lchan [label="LCHAN_EV_TS_READY"];
	bts <= bsc_lchan [label="RSL Chan Activ (and so on)"];
	...;
	...;
	bts rbox bsc_lchan [label="IN_USE, when lchan FSM releases (both regularly, or due to error)"];
	bsc_ts <- bsc_lchan [label="TS_EV_LCHAN_UNUSED (data=lchan)"];
	--- [label="IF all lchan->fi->state == LCHAN_ST_UNUSED"];
	bsc_ts abox bsc_ts [label="UNUSED"];
	---;
	...;
	...;


	bts rbox bsc_lchan [label="PDCH on lchan request"];
	bsc_ts note bsc_lchan [label="TS_EV_LCHAN_REQUESTED should only come in on
		lchans where it makes sense, both from TS kind as well as not
		conflicting with other users of the lchan."];

	bsc_ts <- bsc_lchan [label="TS_EV_LCHAN_REQUESTED"];
	bsc_ts abox bsc_ts [label="WAIT_PDCH_DEACT (?s, Tnnnn)"];
	bts <= bsc_ts [label="RSL RF Chan Release of PDCH",ID="Osmocom style"];
	bts <= bsc_ts [label="RSL PDCH Deact",ID="ip.access style"];
	...;
	--- [label="timeout:"];
	bsc_ts abox bsc_ts [label="BORKEN"];
	bsc_ts -> bsc_lchan [label="LCHAN_EV_TS_ERROR"];
	---;
	...;
	bts => bsc_ts [label="RSL RF Chan Release ACK",ID="Osmocom style"];
	bts => bsc_ts [label="RSL PDCH Deact ACK",ID="ip.access style"];
	--- [label="IF all lchan->fi->state == LCHAN_ST_UNUSED"];
	bsc_ts note bsc_lchan [label="If the lchan FSM decided to give up in the
		meantime, nr of active lchans might have dropped back to zero."];
	bsc_ts abox bsc_ts [label="UNUSED"];
	bsc_ts note bsc_ts [label="onenter at UNUSED state will trigger back to
		PDCH mode"];
	|||;
	--- [label="IF at least one lchan->state != LCHAN_ST_UNUSED"];
	bsc_ts abox bsc_ts [label="IN_USE"];
	bsc_ts rbox bsc_ts [label="Continue at 'IN_USE' above"];
	...;
	...;

	bts rbox bsc_lchan [label="on erratic event"];
	bsc_ts -> bsc_lchan [label="LCHAN_EV_TS_ERROR"];
	bsc_lchan box bsc_lchan [label="release lchan"];
	...;
	bsc_ts <- bsc_lchan [label="TS_EV_LCHAN_UNUSED"];
	bsc_ts note bsc_ts [label="log error but ignore"];
	...;

}