Cellular Network Infrastructure » Radio Access Network » OsmoBSC

commit 6082a377f57901302816a2e57e75a3f262b7b7e6 in osmo-bsc (most probably from openbsc time since it's from 2013), change code in src/libbsc/abis_rsl.c function rsl_rx_chan_rqd:

commit 6082a377f57901302816a2e57e75a3f262b7b7e6
Author: Andreas Eversberg <jolly@eversberg.eu>
Date:   Fri May 31 15:05:52 2013 +0200

    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

diff --git a/src/libbsc/abis_rsl.c b/src/libbsc/abis_rsl.c
index 980b3e66..64e5c92c 100644
--- a/src/libbsc/abis_rsl.c
+++ b/src/libbsc/abis_rsl.c
@@ -1890,8 +1890,26 @@ static int rsl_rx_chan_rqd(struct msgb *msg)
         */
        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);
+       }

With that change, the variable is_lu stopped being used and now compiler warning warns about the variable being set but not used. Did the patch forget to drop the unused variable or should the is_lu var be passed as parameter to lchan_alloc as it used to do before the patch?