laforge has submitted this change. ( https://gerrit.osmocom.org/c/osmo-bts/+/27621 )

Change subject: fix gsm_bts_get_cbch(): CBCH can be allocated on Cn ......................................................................

fix gsm_bts_get_cbch(): CBCH can be allocated on Cn

According to 3GPP TS 45.002, table 3, unlike the CCCH+SDCCH/4+CBCH combination, which can only be allocated on C0/TS0, the SDCCH/8+CBCH can be allocated on C0..n/TS0..3. In other words, having CBCH on e.g. C1/TS2 is perfectly legal. This is why in gsm_bts_get_cbch() we should check all transceivers, not just the C0.

Without this change osmo-bts does not send CBCH Load Indications at all if the CBCH is allocated on C1..n.

Change-Id: Ib5976783b53521047fbdfc18e0e236e8bce8eaae Related: osmo-bsc.git Ie79ccff4f8f0f1134757ec0c35e18b58081cc158 Related: SYS#5905 --- M src/common/bts.c 1 file changed, 11 insertions(+), 10 deletions(-)

Approvals: Jenkins Builder: Verified pespin: Looks good to me, but someone else must approve laforge: Looks good to me, approved

diff --git a/src/common/bts.c b/src/common/bts.c index 4e49c45..0608df1 100644 --- a/src/common/bts.c +++ b/src/common/bts.c @@ -883,22 +883,23 @@ /* return the gsm_lchan for the CBCH (if it exists at all) */ struct gsm_lchan *gsm_bts_get_cbch(struct gsm_bts *bts) { - struct gsm_lchan *lchan = NULL; struct gsm_bts_trx *trx = bts->c0;

+ /* According to 3GPP TS 45.002, table 3, CBCH can be allocated + * either on C0/TS0 (CCCH+SDCCH4) or on C0..n/TS0..3 (SDCCH/8). */ if (trx->ts[0].pchan == GSM_PCHAN_CCCH_SDCCH4_CBCH) - lchan = &trx->ts[0].lchan[2]; - else { - int i; - for (i = 0; i < 8; i++) { - if (trx->ts[i].pchan == GSM_PCHAN_SDCCH8_SACCH8C_CBCH) { - lchan = &trx->ts[i].lchan[2]; - break; - } + return &trx->ts[0].lchan[2]; /* C0/TS0 */ + + llist_for_each_entry(trx, &bts->trx_list, list) { /* C0..n */ + unsigned int tn; + for (tn = 0; tn <= 3; tn++) { /* TS0..3 */ + struct gsm_bts_trx_ts *ts = &trx->ts[tn]; + if (ts->pchan == GSM_PCHAN_SDCCH8_SACCH8C_CBCH) + return &ts->lchan[2]; } }

- return lchan; + return NULL; }

/* BCCH carrier power reduction (see 3GPP TS 45.008, section 7.1) */