diff --git a/include/ecrt.h b/include/ecrt.h
index 016a1441..0eeeddc6 100644
--- a/include/ecrt.h
+++ b/include/ecrt.h
@@ -1291,8 +1291,10 @@ EC_PUBLIC_API int ecrt_slave_config_sync_manager(
  *
  * This method has to be called in non-realtime context before
  * ecrt_master_activate().
+ *
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_slave_config_watchdog(
+EC_PUBLIC_API int ecrt_slave_config_watchdog(
         ec_slave_config_t *sc, /**< Slave configuration. */
         uint16_t watchdog_divider, /**< Number of 40 ns intervals (register
                                      0x0400). Used as a base unit for all
@@ -1330,8 +1332,9 @@ EC_PUBLIC_API int ecrt_slave_config_pdo_assign_add(
  * ecrt_master_activate().
  *
  * \see ecrt_slave_config_pdos()
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_slave_config_pdo_assign_clear(
+EC_PUBLIC_API int ecrt_slave_config_pdo_assign_clear(
         ec_slave_config_t *sc, /**< Slave configuration. */
         uint8_t sync_index /**< Sync manager index. Must be less
                               than #EC_MAX_SYNC_MANAGERS. */
@@ -1364,8 +1367,9 @@ EC_PUBLIC_API int ecrt_slave_config_pdo_mapping_add(
  * ecrt_master_activate().
  *
  * \see ecrt_slave_config_pdos()
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_slave_config_pdo_mapping_clear(
+EC_PUBLIC_API int ecrt_slave_config_pdo_mapping_clear(
         ec_slave_config_t *sc, /**< Slave configuration. */
         uint16_t pdo_index /**< Index of the PDO. */
         );
@@ -1512,8 +1516,9 @@ EC_PUBLIC_API int ecrt_slave_config_reg_pdo_entry_pos(
  * ecrt_master_activate().
  *
  * \attention The \a sync1_shift time is ignored.
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_slave_config_dc(
+EC_PUBLIC_API int ecrt_slave_config_dc(
         ec_slave_config_t *sc, /**< Slave configuration. */
         uint16_t assign_activate, /**< AssignActivate word. */
         uint32_t sync0_cycle, /**< SYNC0 cycle time [ns]. */
@@ -1780,7 +1785,7 @@ EC_PUBLIC_API ec_reg_request_t *ecrt_slave_config_create_reg_request(
  *
  * \ingroup ApplicationInterfaceRT
  */
-EC_PUBLIC_API void ecrt_slave_config_state(
+EC_PUBLIC_API int ecrt_slave_config_state(
         const ec_slave_config_t *sc, /**< Slave configuration */
         ec_slave_config_state_t *state /**< State object to write to. */
         );
diff --git a/lib/slave_config.c b/lib/slave_config.c
index 132158df..aa2da090 100644
--- a/lib/slave_config.c
+++ b/lib/slave_config.c
@@ -109,7 +109,7 @@ int ecrt_slave_config_sync_manager(ec_slave_config_t *sc, uint8_t sync_index,
 
 /****************************************************************************/
 
-void ecrt_slave_config_watchdog(ec_slave_config_t *sc,
+int ecrt_slave_config_watchdog(ec_slave_config_t *sc,
         uint16_t divider, uint16_t intervals)
 {
     ec_ioctl_config_t data;
@@ -124,7 +124,9 @@ void ecrt_slave_config_watchdog(ec_slave_config_t *sc,
     if (EC_IOCTL_IS_ERROR(ret)) {
         fprintf(stderr, "Failed to config watchdog: %s\n",
                 strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
@@ -151,7 +153,7 @@ int ecrt_slave_config_pdo_assign_add(ec_slave_config_t *sc,
 
 /****************************************************************************/
 
-void ecrt_slave_config_pdo_assign_clear(ec_slave_config_t *sc,
+int ecrt_slave_config_pdo_assign_clear(ec_slave_config_t *sc,
         uint8_t sync_index)
 {
     ec_ioctl_config_pdo_t data;
@@ -164,7 +166,9 @@ void ecrt_slave_config_pdo_assign_clear(ec_slave_config_t *sc,
     if (EC_IOCTL_IS_ERROR(ret)) {
         fprintf(stderr, "Failed to clear PDOs: %s\n",
                 strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
@@ -194,7 +198,7 @@ int ecrt_slave_config_pdo_mapping_add(ec_slave_config_t *sc,
 
 /****************************************************************************/
 
-void ecrt_slave_config_pdo_mapping_clear(ec_slave_config_t *sc,
+int ecrt_slave_config_pdo_mapping_clear(ec_slave_config_t *sc,
         uint16_t pdo_index)
 {
     ec_ioctl_config_pdo_t data;
@@ -207,7 +211,9 @@ void ecrt_slave_config_pdo_mapping_clear(ec_slave_config_t *sc,
     if (EC_IOCTL_IS_ERROR(ret)) {
         fprintf(stderr, "Failed to clear PDO entries: %s\n",
                 strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
@@ -356,7 +362,7 @@ int ecrt_slave_config_reg_pdo_entry_pos(
 
 /****************************************************************************/
 
-void ecrt_slave_config_dc(ec_slave_config_t *sc, uint16_t assign_activate,
+int ecrt_slave_config_dc(ec_slave_config_t *sc, uint16_t assign_activate,
         uint32_t sync0_cycle_time, int32_t sync0_shift_time,
         uint32_t sync1_cycle_time, int32_t sync1_shift_time)
 {
@@ -372,9 +378,9 @@ void ecrt_slave_config_dc(ec_slave_config_t *sc, uint16_t assign_activate,
 
     ret = ioctl(sc->master->fd, EC_IOCTL_SC_DC, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to set DC parameters: %s\n",
-                strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
@@ -813,7 +819,7 @@ ec_voe_handler_t *ecrt_slave_config_create_voe_handler(ec_slave_config_t *sc,
 
 /****************************************************************************/
 
-void ecrt_slave_config_state(const ec_slave_config_t *sc,
+int ecrt_slave_config_state(const ec_slave_config_t *sc,
         ec_slave_config_state_t *state)
 {
     ec_ioctl_sc_state_t data;
@@ -824,9 +830,9 @@ void ecrt_slave_config_state(const ec_slave_config_t *sc,
 
     ret = ioctl(sc->master->fd, EC_IOCTL_SC_STATE, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to get slave configuration state: %s\n",
-                strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
diff --git a/master/ioctl.c b/master/ioctl.c
index f0440e50..4282bf85 100644
--- a/master/ioctl.c
+++ b/master/ioctl.c
@@ -2392,7 +2392,7 @@ static ATTRIBUTES int ec_ioctl_sc_watchdog(
         goto out_up;
     }
 
-    ecrt_slave_config_watchdog(sc,
+    ret = ecrt_slave_config_watchdog(sc,
             data.watchdog_divider, data.watchdog_intervals);
 
 out_up:
@@ -2466,8 +2466,7 @@ static ATTRIBUTES int ec_ioctl_sc_clear_pdos(
 
     up(&master->master_sem); /** \todo sc could be invalidated */
 
-    ecrt_slave_config_pdo_assign_clear(sc, data.sync_index);
-    return 0;
+    return ecrt_slave_config_pdo_assign_clear(sc, data.sync_index);
 }
 
 /****************************************************************************/
@@ -2536,8 +2535,7 @@ static ATTRIBUTES int ec_ioctl_sc_clear_entries(
 
     up(&master->master_sem); /** \todo sc could be invalidated */
 
-    ecrt_slave_config_pdo_mapping_clear(sc, data.index);
-    return 0;
+    return ecrt_slave_config_pdo_mapping_clear(sc, data.index);
 }
 
 /****************************************************************************/
@@ -2651,6 +2649,7 @@ static ATTRIBUTES int ec_ioctl_sc_dc(
 {
     ec_ioctl_config_t data;
     ec_slave_config_t *sc;
+    int ret;
 
     if (unlikely(!ctx->requested))
         return -EPERM;
@@ -2666,7 +2665,7 @@ static ATTRIBUTES int ec_ioctl_sc_dc(
         return -ENOENT;
     }
 
-    ecrt_slave_config_dc(sc, data.dc_assign_activate,
+    ret = ecrt_slave_config_dc(sc, data.dc_assign_activate,
             data.dc_sync[0].cycle_time,
             data.dc_sync[0].shift_time,
             data.dc_sync[1].cycle_time,
@@ -2674,7 +2673,7 @@ static ATTRIBUTES int ec_ioctl_sc_dc(
 
     up(&master->master_sem);
 
-    return 0;
+    return ret;
 }
 
 /****************************************************************************/
@@ -3119,6 +3118,7 @@ static ATTRIBUTES int ec_ioctl_sc_state(
     ec_ioctl_sc_state_t data;
     const ec_slave_config_t *sc;
     ec_slave_config_state_t state;
+    int ret;
 
     if (unlikely(!ctx->requested))
         return -EPERM;
@@ -3134,7 +3134,9 @@ static ATTRIBUTES int ec_ioctl_sc_state(
         return -ENOENT;
     }
 
-    ecrt_slave_config_state(sc, &state);
+    ret = ecrt_slave_config_state(sc, &state);
+    if (ret)
+        return ret;
 
     if (ec_copy_to_user((void __user *) data.state,
                         &state, sizeof(state), ctx))
diff --git a/master/slave_config.c b/master/slave_config.c
index 16f5fe99..a2cbf2ce 100644
--- a/master/slave_config.c
+++ b/master/slave_config.c
@@ -647,7 +647,7 @@ int ecrt_slave_config_sync_manager(ec_slave_config_t *sc, uint8_t sync_index,
 
 /****************************************************************************/
 
-void ecrt_slave_config_watchdog(ec_slave_config_t *sc,
+int ecrt_slave_config_watchdog(ec_slave_config_t *sc,
         uint16_t divider, uint16_t intervals)
 {
     EC_CONFIG_DBG(sc, 1, "%s(sc = 0x%p, divider = %u, intervals = %u)\n",
@@ -655,6 +655,7 @@ void ecrt_slave_config_watchdog(ec_slave_config_t *sc,
 
     sc->watchdog_divider = divider;
     sc->watchdog_intervals = intervals;
+    return 0;
 }
 
 /****************************************************************************/
@@ -689,7 +690,7 @@ int ecrt_slave_config_pdo_assign_add(ec_slave_config_t *sc,
 
 /****************************************************************************/
 
-void ecrt_slave_config_pdo_assign_clear(ec_slave_config_t *sc,
+int ecrt_slave_config_pdo_assign_clear(ec_slave_config_t *sc,
         uint8_t sync_index)
 {
     EC_CONFIG_DBG(sc, 1, "%s(sc = 0x%p, sync_index = %u)\n",
@@ -697,12 +698,13 @@ void ecrt_slave_config_pdo_assign_clear(ec_slave_config_t *sc,
 
     if (sync_index >= EC_MAX_SYNC_MANAGERS) {
         EC_CONFIG_ERR(sc, "Invalid sync manager index %u!\n", sync_index);
-        return;
+        return -EINVAL;
     }
 
     down(&sc->master->master_sem);
     ec_pdo_list_clear_pdos(&sc->sync_configs[sync_index].pdos);
     up(&sc->master->master_sem);
+    return 0;
 }
 
 /****************************************************************************/
@@ -744,7 +746,7 @@ int ecrt_slave_config_pdo_mapping_add(ec_slave_config_t *sc,
 
 /****************************************************************************/
 
-void ecrt_slave_config_pdo_mapping_clear(ec_slave_config_t *sc,
+int ecrt_slave_config_pdo_mapping_clear(ec_slave_config_t *sc,
         uint16_t pdo_index)
 {
     uint8_t sync_index;
@@ -765,6 +767,7 @@ void ecrt_slave_config_pdo_mapping_clear(ec_slave_config_t *sc,
     } else {
         EC_CONFIG_WARN(sc, "PDO 0x%04X is not assigned.\n", pdo_index);
     }
+    return 0;
 }
 
 /****************************************************************************/
@@ -956,7 +959,7 @@ int ecrt_slave_config_reg_pdo_entry_pos(
 
 /****************************************************************************/
 
-void ecrt_slave_config_dc(ec_slave_config_t *sc, uint16_t assign_activate,
+int ecrt_slave_config_dc(ec_slave_config_t *sc, uint16_t assign_activate,
         uint32_t sync0_cycle_time, int32_t sync0_shift_time,
         uint32_t sync1_cycle_time, int32_t sync1_shift_time)
 {
@@ -971,6 +974,7 @@ void ecrt_slave_config_dc(ec_slave_config_t *sc, uint16_t assign_activate,
     sc->dc_sync[0].shift_time = sync0_shift_time;
     sc->dc_sync[1].cycle_time = sync1_cycle_time;
     sc->dc_sync[1].shift_time = sync1_shift_time;
+    return 0;
 }
 
 /****************************************************************************/
@@ -1317,7 +1321,7 @@ ec_voe_handler_t *ecrt_slave_config_create_voe_handler(
 
 /****************************************************************************/
 
-void ecrt_slave_config_state(const ec_slave_config_t *sc,
+int ecrt_slave_config_state(const ec_slave_config_t *sc,
         ec_slave_config_state_t *state)
 {
     const ec_slave_t *slave = sc->slave;
@@ -1331,6 +1335,7 @@ void ecrt_slave_config_state(const ec_slave_config_t *sc,
         state->operational = 0;
         state->al_state = EC_SLAVE_STATE_UNKNOWN;
     }
+    return 0;
 }
 
 /****************************************************************************/