2 is the latest approved patch-set.
No files were changed between the latest approved patch-set and the submitted one.


csd_v110_rtp_decode: preserve E2 & E3 bits for RLP alignment

Modify CSD RTP input path code so incoming bits E2 & E3 from V.110
frames reach the TCH-RTS.ind handler in l1sap.  These bits will be
used in the next patch to ensure proper alignment of DL RLP frames
in non-transparent CSD modes.

Related: OS#6579
Change-Id: I43b97caa6030b9401779998ca5dddc4cfe636e2f
---
M include/osmo-bts/csd_v110.h
M include/osmo-bts/msg_utils.h
M src/common/csd_v110.c
M src/common/l1sap.c
M tests/csd/csd_test.c
5 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/include/osmo-bts/csd_v110.h b/include/osmo-bts/csd_v110.h
index a7c3a1b..7d67ff0 100644
--- a/include/osmo-bts/csd_v110.h
+++ b/include/osmo-bts/csd_v110.h
@@ -17,4 +17,4 @@
 			const uint8_t *data, size_t data_len,
 			uint8_t nt48_half_num);
 int csd_v110_rtp_decode(const struct gsm_lchan *lchan, uint8_t *data,
-			const uint8_t *rtp, size_t rtp_len);
+			uint8_t *align_bits, const uint8_t *rtp, size_t rtp_len);
diff --git a/include/osmo-bts/msg_utils.h b/include/osmo-bts/msg_utils.h
index fb8e11a..db7142d 100644
--- a/include/osmo-bts/msg_utils.h
+++ b/include/osmo-bts/msg_utils.h
@@ -25,6 +25,9 @@
 /* Access 4th part of msgb control buffer */
 #define rtpmsg_is_rfc5993_sid(x) ((x)->cb[3])
 
+/* Access 5th part of msgb control buffer */
+#define rtpmsg_csd_align_bits(x) ((x)->cb[4])
+
 /**
  * Classification of OML message. ETSI for plain GSM 12.21
  * messages and IPA/Osmo for manufacturer messages.
diff --git a/src/common/csd_v110.c b/src/common/csd_v110.c
index b2d2b42..e307a6e 100644
--- a/src/common/csd_v110.c
+++ b/src/common/csd_v110.c
@@ -166,10 +166,11 @@
 }
 
 int csd_v110_rtp_decode(const struct gsm_lchan *lchan, uint8_t *data,
-			const uint8_t *rtp, size_t rtp_len)
+			uint8_t *align_bits, const uint8_t *rtp, size_t rtp_len)
 {
 	const struct csd_v110_lchan_desc *desc;
 	ubit_t ra_bits[80 * 4];
+	uint8_t align_accum = 0;
 
 	OSMO_ASSERT(lchan->tch_mode < ARRAY_SIZE(csd_v110_lchan_desc));
 	desc = &csd_v110_lchan_desc[lchan->tch_mode];
@@ -207,7 +208,13 @@
 			osmo_csd_12k_6k_encode_frame(&data[i * 60], 60, &df);
 		else /* desc->num_bits == 36 */
 			osmo_csd_3k6_encode_frame(&data[i * 36], 36, &df);
+		/* save bits E2 & E3 that may be needed for RLP alignment */
+		align_accum <<= 2;
+		align_accum |= df.e_bits[1] << 1;
+		align_accum |= df.e_bits[2] << 0;
 	}
 
+	if (align_bits)
+		*align_bits = align_accum;
 	return desc->num_blocks * desc->num_bits;
 }
diff --git a/src/common/l1sap.c b/src/common/l1sap.c
index 65ebf35..1abc409 100644
--- a/src/common/l1sap.c
+++ b/src/common/l1sap.c
@@ -2597,6 +2597,7 @@
 	struct gsm_bts *bts = lchan->ts->trx->bts;
 	struct msgb *msg;
 	bool rfc5993_sid = false;
+	uint8_t csd_align_bits = 0;
 
 	rate_ctr_inc2(bts->ctrs, BTS_CTR_RTP_RX_TOTAL);
 	if (marker)
@@ -2631,7 +2632,7 @@
 		return;
 
 	if (lchan->rsl_cmode == RSL_CMOD_SPD_DATA) {
-		int rc = csd_v110_rtp_decode(lchan, msg->tail,
+		int rc = csd_v110_rtp_decode(lchan, msg->tail, &csd_align_bits,
 					     rtp_pl, rtp_pl_len);
 		if (rc > 0) {
 			/* 'fake' tch_ind containing all-zero so gsmtap code can be shared
@@ -2664,6 +2665,8 @@
 	rtpmsg_ts(msg) = timestamp;
 	/* Store RFC 5993 SID flag likewise */
 	rtpmsg_is_rfc5993_sid(msg) = rfc5993_sid;
+	/* ditto with CSD alignment bits */
+	rtpmsg_csd_align_bits(msg) = csd_align_bits;
 
 	/* make sure the queue doesn't get too long */
 	lchan_dl_tch_queue_enqueue(lchan, msg, 1);
diff --git a/tests/csd/csd_test.c b/tests/csd/csd_test.c
index 15ee84f..e52bde2 100644
--- a/tests/csd/csd_test.c
+++ b/tests/csd/csd_test.c
@@ -133,7 +133,7 @@
 		fprintf(stderr, "    %s\n", osmo_hexdump(&rtp[i * 16], 16));
 
 	/* decode the encoded RTP frame */
-	rc = csd_v110_rtp_decode(&lchan, &data_dec[0], &rtp[0], sizeof(rtp));
+	rc = csd_v110_rtp_decode(&lchan, &data_dec[0], NULL, &rtp[0], sizeof(rtp));
 	fprintf(stderr, "[i] csd_v110_rtp_decode() returns %d\n", rc);
 	if (rc != bit_num)
 		return;

