diff --git a/openbsc/include/openbsc/gsm_data_shared.h b/openbsc/include/openbsc/gsm_data_shared.h
index 4516aba..ceb5398 100644
--- a/openbsc/include/openbsc/gsm_data_shared.h
+++ b/openbsc/include/openbsc/gsm_data_shared.h
@@ -584,15 +584,15 @@
 struct gsm_bts *gsm_bts_alloc(void *talloc_ctx);
 struct gsm_bts_trx *gsm_bts_trx_alloc(struct gsm_bts *bts);
 
-struct gsm_bts_trx *gsm_bts_trx_num(struct gsm_bts *bts, int num);
+struct gsm_bts_trx *gsm_bts_trx_num(const struct gsm_bts *bts, int num);
 
 const char *gsm_pchan_name(enum gsm_phys_chan_config c);
 enum gsm_phys_chan_config gsm_pchan_parse(const char *name);
 const char *gsm_lchant_name(enum gsm_chan_t c);
 const char *gsm_chreq_name(enum gsm_chreq_reason_t c);
-char *gsm_trx_name(struct gsm_bts_trx *trx);
-char *gsm_ts_name(struct gsm_bts_trx_ts *ts);
-char *gsm_lchan_name(struct gsm_lchan *lchan);
+char *gsm_trx_name(const struct gsm_bts_trx *trx);
+char *gsm_ts_name(const struct gsm_bts_trx_ts *ts);
+char *gsm_lchan_name(const struct gsm_lchan *lchan);
 const char *gsm_lchans_name(enum gsm_lchan_state s);
 
 
@@ -600,14 +600,14 @@
 
 struct gsm_abis_mo *
 gsm_objclass2mo(struct gsm_bts *bts, uint8_t obj_class,
-	    struct abis_om_obj_inst *obj_inst);
+	    const struct abis_om_obj_inst *obj_inst);
 
 struct gsm_nm_state *
 gsm_objclass2nmstate(struct gsm_bts *bts, uint8_t obj_class,
-		 struct abis_om_obj_inst *obj_inst);
+		 const struct abis_om_obj_inst *obj_inst);
 void *
 gsm_objclass2obj(struct gsm_bts *bts, uint8_t obj_class,
-	     struct abis_om_obj_inst *obj_inst);
+	     const struct abis_om_obj_inst *obj_inst);
 
 /* reset the state of all MO in the BTS */
 void gsm_bts_mo_reset(struct gsm_bts *bts);
diff --git a/openbsc/src/libcommon/gsm_data_shared.c b/openbsc/src/libcommon/gsm_data_shared.c
index b52d58a..06a095e 100644
--- a/openbsc/src/libcommon/gsm_data_shared.c
+++ b/openbsc/src/libcommon/gsm_data_shared.c
@@ -245,7 +245,7 @@
 	}
 }
 
-struct gsm_bts_trx *gsm_bts_trx_num(struct gsm_bts *bts, int num)
+struct gsm_bts_trx *gsm_bts_trx_num(const struct gsm_bts *bts, int num)
 {
 	struct gsm_bts_trx *trx;
 
@@ -262,7 +262,7 @@
 
 static char ts2str[255];
 
-char *gsm_trx_name(struct gsm_bts_trx *trx)
+char *gsm_trx_name(const struct gsm_bts_trx *trx)
 {
 	snprintf(ts2str, sizeof(ts2str), "(bts=%d,trx=%d)",
 		 trx->bts->nr, trx->nr);
@@ -271,7 +271,7 @@
 }
 
 
-char *gsm_ts_name(struct gsm_bts_trx_ts *ts)
+char *gsm_ts_name(const struct gsm_bts_trx_ts *ts)
 {
 	snprintf(ts2str, sizeof(ts2str), "(bts=%d,trx=%d,ts=%d)",
 		 ts->trx->bts->nr, ts->trx->nr, ts->nr);
@@ -279,7 +279,7 @@
 	return ts2str;
 }
 
-char *gsm_lchan_name(struct gsm_lchan *lchan)
+char *gsm_lchan_name(const struct gsm_lchan *lchan)
 {
 	struct gsm_bts_trx_ts *ts = lchan->ts;
 
@@ -292,7 +292,7 @@
 /* obtain the MO structure for a given object instance */
 struct gsm_abis_mo *
 gsm_objclass2mo(struct gsm_bts *bts, uint8_t obj_class,
-	    struct abis_om_obj_inst *obj_inst)
+	    const struct abis_om_obj_inst *obj_inst)
 {
 	struct gsm_bts_trx *trx;
 	struct gsm_abis_mo *mo = NULL;
@@ -373,7 +373,7 @@
 /* obtain the gsm_nm_state data structure for a given object instance */
 struct gsm_nm_state *
 gsm_objclass2nmstate(struct gsm_bts *bts, uint8_t obj_class,
-		 struct abis_om_obj_inst *obj_inst)
+		 const struct abis_om_obj_inst *obj_inst)
 {
 	struct gsm_abis_mo *mo;
 
@@ -387,7 +387,7 @@
 /* obtain the in-memory data structure of a given object instance */
 void *
 gsm_objclass2obj(struct gsm_bts *bts, uint8_t obj_class,
-	     struct abis_om_obj_inst *obj_inst)
+	     const struct abis_om_obj_inst *obj_inst)
 {
 	struct gsm_bts_trx *trx;
 	void *obj = NULL;