[PATCH] osmo-bsc[master]: HO: Assign SDCCH on channel request

[Neels Hofmeyr]

Review at  https://gerrit.osmocom.org/5898

HO: Assign SDCCH on channel request

This is needed, so channel can be negotiated before the actual channel
type is assigned.

In case there is no SDCCH available, try to assign what ever the MS requested.
If this is not possible try to assign TCH/F. If this is still not possible,
reject channel request.

Change-Id: I10fc9f60c58c6b7ed424a86ce23bf6b9802c9eb1
---
M src/libbsc/abis_rsl.c
1 file changed, 20 insertions(+), 2 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/osmo-bsc refs/changes/98/5898/1

diff --git a/src/libbsc/abis_rsl.c b/src/libbsc/abis_rsl.c
index 980b3e6..cb28287 100644
--- a/src/libbsc/abis_rsl.c
+++ b/src/libbsc/abis_rsl.c
@@ -1890,8 +1890,26 @@
 	 */
 	is_lu = !!(chreq_reason == GSM_CHREQ_REASON_LOCATION_UPD);
 
-	/* check availability / allocate channel */
-	lchan = lchan_alloc(bts, lctype, is_lu);
+	/* check availability / allocate channel
+	 *
+	 * - First try to allocate SDCCH. 
+	 * - If SDCCH is not available, try whatever MS requested, if not SDCCH.
+	 * - If there is still no channel available, reject channel request.
+	 *
+	 * lchan_alloc() possibly tries to allocate larger lchans.
+	 *
+	 * Note: If the MS requests not TCH/H, we don't know if the phone
+	 *       supports TCH/H, so we must assign TCH/F or SDCCH.
+	 */
+	lchan = lchan_alloc(bts, GSM_LCHAN_SDCCH, 0);
+	if (!lchan && lctype != GSM_LCHAN_SDCCH) {
+		LOGP(DRSL, LOGL_NOTICE, "BTS %d CHAN RQD: no resources for %s "
+			"0x%x, retrying with %s\n",
+			msg->lchan->ts->trx->bts->nr,
+			gsm_lchant_name(GSM_LCHAN_SDCCH), rqd_ref->ra,
+			gsm_lchant_name(lctype));
+		lchan = lchan_alloc(bts, lctype, 0);
+	}
 	if (!lchan) {
 		LOGP(DRSL, LOGL_NOTICE, "BTS %d CHAN RQD: no resources for %s 0x%x\n",
 		     msg->lchan->ts->trx->bts->nr, gsm_lchant_name(lctype), rqd_ref->ra);

-- 
To view, visit https://gerrit.osmocom.org/5898
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I10fc9f60c58c6b7ed424a86ce23bf6b9802c9eb1
Gerrit-PatchSet: 1
Gerrit-Project: osmo-bsc
Gerrit-Branch: master
Gerrit-Owner: Neels Hofmeyr <nhofmeyr at sysmocom.de>