ASCI: Add Notification CHannel (NCH) support

The location of the NCH is defined by the rest octet of System
Information 1. If NCH is defined, the given CCCH blocks are used for NCH
instead of AGCH/PCH.

The current list of VGCS/VBS call notifications is transmitted on the
NCH. If there is no notification, an empty notification is transmitted
on the NCH.

The Notification List Number (NLN) is used to indicated new
notificaitons. Only the last notification (or empty notification)
indicates NLN. This way the MS can determine after two equal NLN that
the complete list has been recevied.

Change-Id: I82fdaba3faaced76267a99ae14a5458a1b41fdaa
Related: OS#5781

1 files changed, 21 insertions, 6 deletions

diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index 1c43f8ff..268486e0 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -902,15 +902,32 @@ static int lchan_pdtch_ph_rts_ind_loop(struct gsm_lchan *lchan,
 	return 0;
 }
 
-/* Check if given CCCH frame number is for a PCH or for an AGCH (this function is
+/* Check if given CCCH frame number is for a NCH, PCH or for an AGCH (this function is
  * only used internally, it is public to call it from unit-tests) */
-int is_ccch_for_agch(struct gsm_bts_trx *trx, uint32_t fn) {
+enum ccch_msgt get_ccch_msgt(struct gsm_bts_trx *trx, uint32_t fn)
+{
+	uint8_t block, first_block, num_blocks;
+	int rc;
+
+	block = l1sap_fn2ccch_block(fn);
+
+	/* If there is an NCH, check if the block number matches. It has priority over PCH/AGCH. */
+	if (trx->bts->asci.pos_nch >= 0) {
+		rc = osmo_gsm48_si1ro_nch_pos_decode(trx->bts->asci.pos_nch, &num_blocks, &first_block);
+		if (rc >= 0 && block >= first_block && block < first_block + num_blocks)
+			return CCCH_MSGT_NCH;
+	}
+
 	/* Note: The number of available access grant channels is set by the
 	 * parameter BS_AG_BLKS_RES via system information type 3. This SI is
 	 * transferred to osmo-bts via RSL */
-        return l1sap_fn2ccch_block(fn) < num_agch(trx, "PH-RTS-IND");
+	if (l1sap_fn2ccch_block(fn) < num_agch(trx, "PH-RTS-IND"))
+		return CCCH_MSGT_AGCH;
+
+	return CCCH_MSGT_PCH;
 }
 
+
 /* return the measured average of frame numbers that the RTS clock is running in advance */
 int32_t bts_get_avg_fn_advance(const struct gsm_bts *bts)
 {
@@ -1048,7 +1065,6 @@ static int l1sap_ph_rts_ind(struct gsm_bts_trx *trx,
 	struct msgb *pp_msg;
 	bool dtxd_facch = false;
 	int rc;
-	int is_ag_res;
 
 	chan_nr = rts_ind->chan_nr;
 	link_id = rts_ind->link_id;
@@ -1183,8 +1199,7 @@ static int l1sap_ph_rts_ind(struct gsm_bts_trx *trx,
 		}
 	} else if (L1SAP_IS_CHAN_AGCH_PCH(chan_nr)) {
 		p = msgb_put(msg, GSM_MACBLOCK_LEN);
-		is_ag_res = is_ccch_for_agch(trx, fn);
-		rc = bts_ccch_copy_msg(trx->bts, p, &g_time, is_ag_res);
+		rc = bts_ccch_copy_msg(trx->bts, p, &g_time, get_ccch_msgt(trx, fn));
 		if (rc <= 0)
 			memcpy(p, fill_frame, GSM_MACBLOCK_LEN);
 	}