dyn TS: implement pchan switchover logic

In struct gsm_lchan, add dyn.rqd_ref and dyn.rqd_ta. These save the Channel
Requested details across the PDCH deactivation dance.

abis_rsl.c: add static functions:

* dyn_ts_switchover*() for the various stages of switchover between pchans.

* pchan_for_lchant() to derive the desired pchan from the lchan type that was
  set during lchan_alloc().

* rsl_chan_activate_lchan_as_pdch() to compose the simpler RSL CHAN ACT message
  without introducing numerous special cases to the normal RSL CHAN ACT code.

In rsl_chan_activate_lchan(), detect and initiate required pchan switchovers if
requested pchan on a dyn TS differs.

In rsl_rx_rf_chan_rel_ack(), initiate or continue pchan switchovers after a
channel was released.

In rsl_rx_chan_act_ack(), notice that a switchover is complete.

In chan_alloc.c, add ts_subslots(): abis_rsl.c will need to know the number of
subslots per pchan, to verify that all lchans are free before dyn TS
switchover. The subslots_per_pchan[] array is static to lchan_alloc.c, and
since we need a non-trivial check for dyn TS anyway, add public ts_subslots()
to lchan_alloc.c, which also checks the current dyn pchan type.

Change-Id: I5c6bce13092a10204113d84678c587c65e35e4fd

1 files changed, 9 insertions, 0 deletions

diff --git a/openbsc/src/libbsc/chan_alloc.c b/openbsc/src/libbsc/chan_alloc.c
index f502740a4..1e5dd74cd 100644
--- a/openbsc/src/libbsc/chan_alloc.c
+++ b/openbsc/src/libbsc/chan_alloc.c
@@ -88,6 +88,15 @@ static const uint8_t subslots_per_pchan[] = {
 	 */
 };
 
+/*! According to ts->pchan and possibly ts->dyn_pchan, return the number of
+ * logical channels available in the timeslot. */
+uint8_t ts_subslots(struct gsm_bts_trx_ts *ts)
+{
+	if (ts->pchan == GSM_PCHAN_TCH_F_TCH_H_PDCH)
+		return subslots_per_pchan[ts->dyn.pchan_is];
+	return subslots_per_pchan[ts->pchan];
+}
+
 static struct gsm_lchan *
 _lc_find_trx(struct gsm_bts_trx *trx, enum gsm_phys_chan_config pchan,
 	     enum gsm_phys_chan_config dyn_as_pchan)