libmsc/gsm_04_08.c: expose gsm48_tx_simple()

This function could be also used by other parts of code, e.g.
by gsm_04_11.c or by gsm_09_11.c, during initialization of
a new transaction. No need to hide it.

Change-Id: I9a9d17fca4901163dae10d76455aa4cf54497156

include/osmocom/msc/gsm_04_08.h

@@ -34,6 +34,8 @@ int gsm0408_rcvmsg(struct msgb *msg, uint8_t link_id);
 /* don't use "enum gsm_chreq_reason_t" to avoid circular dependency */
 void gsm_net_update_ctype(struct gsm_network *net);
 
+int gsm48_tx_simple(struct gsm_subscriber_connection *conn,
+		    uint8_t pdisc, uint8_t msg_type);
 int gsm48_tx_mm_info(struct gsm_subscriber_connection *conn);
 int gsm48_tx_mm_auth_req(struct gsm_subscriber_connection *conn, uint8_t *rand,
 			 uint8_t *autn, int key_seq);

src/libmsc/gsm_04_08.c

@@ -79,8 +79,6 @@ void *tall_authciphop_ctx;
 
 static int gsm0408_loc_upd_acc(struct gsm_subscriber_connection *conn,
 			       uint32_t send_tmsi);
-static int gsm48_tx_simple(struct gsm_subscriber_connection *conn,
-			   uint8_t pdisc, uint8_t msg_type);
 
 static uint32_t new_callref = 0x80000001;
 
@@ -1345,8 +1343,14 @@ static int gsm48_cc_tx_status(struct gsm_trans *trans, void *arg)
 	return gsm48_conn_sendmsg(msg, trans->conn, trans);
 }
 
-static int gsm48_tx_simple(struct gsm_subscriber_connection *conn,
-			   uint8_t pdisc, uint8_t msg_type)
+/*! Send a simple GSM 04.08 message without any payload
+ * \param      conn      Active subscriber connection
+ * \param[in]  pdisc     Protocol discriminator
+ * \param[in]  msg_type  Message type
+ * \return     result of \ref gsm48_conn_sendmsg
+ */
+int gsm48_tx_simple(struct gsm_subscriber_connection *conn,
+		    uint8_t pdisc, uint8_t msg_type)
 {
 	struct msgb *msg = gsm48_msgb_alloc_name("GSM 04.08 TX SIMPLE");
 	struct gsm48_hdr *gh = (struct gsm48_hdr *) msgb_put(msg, sizeof(*gh));