[PATCH] osmocom-bb[fixeria/trx]: trxcon/sched_prim.c: fix: correct the first padding byte

[Vadim Yanitskiy]

Review at  https://gerrit.osmocom.org/7467

trxcon/sched_prim.c: fix: correct the first padding byte

According to TS 144.006, section 5.2, the first octet containing
fill bits shall be set to the binary value "00101011" == 0x2b.

Change-Id: I8f0304bf84613a2dc07cb78aff0cb8bb4c5adf6c
---
M src/host/trxcon/sched_prim.c
1 file changed, 10 insertions(+), 9 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/osmocom-bb refs/changes/67/7467/1

diff --git a/src/host/trxcon/sched_prim.c b/src/host/trxcon/sched_prim.c
index c17fb2a..e1c87bb 100644
--- a/src/host/trxcon/sched_prim.c
+++ b/src/host/trxcon/sched_prim.c
@@ -251,7 +251,7 @@
 	 * and with an information field of 0 octet length.
 	 */
 	static const uint8_t lapdm_fill_frame[] = {
-		0x01, 0x03, 0x01,
+		0x01, 0x03, 0x01, 0x2b,
 		/* Pending part is to be randomized */
 	};
 
@@ -275,15 +275,16 @@
 		/* FIXME: should we do anything for CSD? */
 		return 0;
 	} else {
-		/**
-		 * TS 144.006, section 8.1.2.3 "Fill frames"
-		 * A fill frame is a UI command frame for SAPI 0, P=0
-		 * and with an information field of 0 octet length.
-		 */
-		memcpy(prim_buffer, lapdm_fill_frame, 3);
+		/* Copy a fill frame payload */
+		memcpy(prim_buffer, lapdm_fill_frame, sizeof(lapdm_fill_frame));
 
-		/* Randomize pending unused bytes */
-		for (i = 3; i < GSM_MACBLOCK_LEN; i++)
+		/**
+		 * TS 144.006, section 5.2 "Frame delimitation and fill bits"
+		 * Except for the first octet containing fill bits which shall
+		 * be set to the binary value "00101011", each fill bit should
+		 * be set to a random value when sent by the network.
+		 */
+		for (i = sizeof(lapdm_fill_frame); i < GSM_MACBLOCK_LEN; i++)
 			prim_buffer[i] = (uint8_t) rand();
 
 		/* Define a prim length */

-- 
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I8f0304bf84613a2dc07cb78aff0cb8bb4c5adf6c
Gerrit-PatchSet: 1
Gerrit-Project: osmocom-bb
Gerrit-Branch: fixeria/trx
Gerrit-Owner: Vadim Yanitskiy <axilirator at gmail.com>