diff --git a/include/ecrt.h b/include/ecrt.h
index 315d4883..82138d7f 100644
--- a/include/ecrt.h
+++ b/include/ecrt.h
@@ -2078,6 +2078,9 @@ ec_request_state_t ecrt_sdo_request_state(
  *
  * \ingroup ApplicationInterfaceRT
  * \return 0 on success, otherwise negative error code.
+ * \retval -EINVAL Invalid input data, e.g. data size == 0.
+ * \retval -ENOMEM Reserved memory in ecrt_slave_config_create_sdo_request()
+ *              too small.
  */
 EC_PUBLIC_API int ecrt_sdo_request_write(
         ec_sdo_request_t *req /**< SDO request. */
@@ -2117,8 +2120,9 @@ EC_PUBLIC_API int ecrt_sdo_request_read(
  * set via ecrt_slave_config_create_soe_request().
  *
  * \ingroup ApplicationInterfaceRT
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_soe_request_idn(
+EC_PUBLIC_API int ecrt_soe_request_idn(
         ec_soe_request_t *req, /**< IDN request. */
         uint8_t drive_no, /**< SDO index. */
         uint16_t idn /**< SoE IDN. */
@@ -2134,8 +2138,9 @@ EC_PUBLIC_API void ecrt_soe_request_idn(
  *
  * The timeout should be defined in non-realtime context, but can also be
  * changed afterwards.
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_soe_request_timeout(
+EC_PUBLIC_API int ecrt_soe_request_timeout(
         ec_soe_request_t *req, /**< SoE request. */
         uint32_t timeout /**< Timeout in milliseconds. Zero means no
                            timeout. */
@@ -2213,8 +2218,12 @@ EC_PUBLIC_API ec_request_state_t ecrt_soe_request_state(
  * activation).
  *
  * \ingroup ApplicationInterfaceRT
+ * \return 0 on success, otherwise negative error code.
+ * \retval -EINVAL Invalid input data, e.g. data size == 0.
+ * \retval -ENOMEM Reserved memory in ecrt_slave_config_create_soe_request()
+ *              too small.
  */
-EC_PUBLIC_API void ecrt_soe_request_write(
+EC_PUBLIC_API int ecrt_soe_request_write(
         ec_soe_request_t *req /**< SoE request. */
         );
 
@@ -2231,8 +2240,9 @@ EC_PUBLIC_API void ecrt_soe_request_write(
  * activation).
  *
  * \ingroup ApplicationInterfaceRT
+ * \return 0 on success, otherwise negative error code.
  */
-EC_PUBLIC_API void ecrt_soe_request_read(
+EC_PUBLIC_API int ecrt_soe_request_read(
         ec_soe_request_t *req /**< SoE request. */
         );
 
diff --git a/lib/soe_request.c b/lib/soe_request.c
index d95a4ef1..822e3c1e 100644
--- a/lib/soe_request.c
+++ b/lib/soe_request.c
@@ -48,7 +48,7 @@ void ec_soe_request_clear(ec_soe_request_t *req)
  * Application interface.
  ****************************************************************************/
 
-void ecrt_soe_request_idn(ec_soe_request_t *req, uint8_t drive_no,
+int ecrt_soe_request_idn(ec_soe_request_t *req, uint8_t drive_no,
         uint16_t idn)
 {
     ec_ioctl_soe_request_t data;
@@ -61,14 +61,14 @@ void ecrt_soe_request_idn(ec_soe_request_t *req, uint8_t drive_no,
 
     ret = ioctl(req->config->master->fd, EC_IOCTL_SOE_REQUEST_IDN, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to set SoE request IDN: %s\n",
-                strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
 
-void ecrt_soe_request_timeout(ec_soe_request_t *req, uint32_t timeout)
+int ecrt_soe_request_timeout(ec_soe_request_t *req, uint32_t timeout)
 {
     ec_ioctl_soe_request_t data;
     int ret;
@@ -79,9 +79,9 @@ void ecrt_soe_request_timeout(ec_soe_request_t *req, uint32_t timeout)
 
     ret = ioctl(req->config->master->fd, EC_IOCTL_SOE_REQUEST_TIMEOUT, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to set SoE request timeout: %s\n",
-                strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
@@ -139,7 +139,7 @@ ec_request_state_t ecrt_soe_request_state(ec_soe_request_t *req)
 
 /****************************************************************************/
 
-void ecrt_soe_request_read(ec_soe_request_t *req)
+int ecrt_soe_request_read(ec_soe_request_t *req)
 {
     ec_ioctl_soe_request_t data;
     int ret;
@@ -149,14 +149,14 @@ void ecrt_soe_request_read(ec_soe_request_t *req)
 
     ret = ioctl(req->config->master->fd, EC_IOCTL_SOE_REQUEST_READ, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to command an SoE read operation : %s\n",
-                strerror(EC_IOCTL_ERRNO(ret)));
+        return -EC_IOCTL_ERRNO(ret);
     }
+    return 0;
 }
 
 /****************************************************************************/
 
-void ecrt_soe_request_write(ec_soe_request_t *req)
+int ecrt_soe_request_write(ec_soe_request_t *req)
 {
     ec_ioctl_soe_request_t data;
     int ret;
@@ -168,9 +168,9 @@ void ecrt_soe_request_write(ec_soe_request_t *req)
 
     ret = ioctl(req->config->master->fd, EC_IOCTL_SOE_REQUEST_WRITE, &data);
     if (EC_IOCTL_IS_ERROR(ret)) {
-        fprintf(stderr, "Failed to command an SDO write operation : %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 04afb142..134b2edc 100644
--- a/master/ioctl.c
+++ b/master/ioctl.c
@@ -3703,8 +3703,7 @@ static ATTRIBUTES int ec_ioctl_soe_request_index(
         return -ENOENT;
     }
 
-    ecrt_soe_request_idn(req, data.drive_no, data.idn);
-    return 0;
+    return ecrt_soe_request_idn(req, data.drive_no, data.idn);
 }
 
 /****************************************************************************/
@@ -3740,8 +3739,7 @@ static ATTRIBUTES int ec_ioctl_soe_request_timeout(
         return -ENOENT;
     }
 
-    ecrt_soe_request_timeout(req, data.timeout);
-    return 0;
+    return ecrt_soe_request_timeout(req, data.timeout);
 }
 
 /****************************************************************************/
@@ -3824,8 +3822,7 @@ static ATTRIBUTES int ec_ioctl_soe_request_read(
         return -ENOENT;
     }
 
-    ecrt_soe_request_read(req);
-    return 0;
+    return ecrt_soe_request_read(req);
 }
 
 /****************************************************************************/
@@ -3874,8 +3871,7 @@ static ATTRIBUTES int ec_ioctl_soe_request_write(
         return -EFAULT;
 
     req->data_size = data.size;
-    ecrt_soe_request_write(req);
-    return 0;
+    return ecrt_soe_request_write(req);
 }
 
 /****************************************************************************/
diff --git a/master/soe_request.c b/master/soe_request.c
index 3960d2b4..ef90124b 100644
--- a/master/soe_request.c
+++ b/master/soe_request.c
@@ -223,7 +223,7 @@ int ec_soe_request_append_data(
 
 /** Request a read operation.
  */
-void ec_soe_request_read(
+int ec_soe_request_read(
         ec_soe_request_t *req /**< SoE request. */
        )
 {
@@ -231,13 +231,14 @@ void ec_soe_request_read(
     req->state = EC_INT_REQUEST_QUEUED;
     req->error_code = 0x0000;
     req->jiffies_start = jiffies;
+    return 0;
 }
 
 /****************************************************************************/
 
 /** Request a write operation.
  */
-void ec_soe_request_write(
+int ec_soe_request_write(
         ec_soe_request_t *req /**< SoE request. */
         )
 {
@@ -245,6 +246,7 @@ void ec_soe_request_write(
     req->state = EC_INT_REQUEST_QUEUED;
     req->error_code = 0x0000;
     req->jiffies_start = jiffies;
+    return 0;
 }
 
 /****************************************************************************/
@@ -263,18 +265,20 @@ int ec_soe_request_timed_out(const ec_soe_request_t *req /**< SDO request. */)
  * Application interface.
  ****************************************************************************/
 
-void ecrt_soe_request_idn(ec_soe_request_t *req, uint8_t drive_no,
+int ecrt_soe_request_idn(ec_soe_request_t *req, uint8_t drive_no,
         uint16_t idn)
 {
     req->drive_no = drive_no;
     req->idn = idn;
+    return 0;
 }
 
 /****************************************************************************/
 
-void ecrt_soe_request_timeout(ec_soe_request_t *req, uint32_t timeout)
+int ecrt_soe_request_timeout(ec_soe_request_t *req, uint32_t timeout)
 {
     req->issue_timeout = timeout;
+    return 0;
 }
 
 /****************************************************************************/
@@ -300,16 +304,16 @@ ec_request_state_t ecrt_soe_request_state(const ec_soe_request_t *req)
 
 /****************************************************************************/
 
-void ecrt_soe_request_read(ec_soe_request_t *req)
+int ecrt_soe_request_read(ec_soe_request_t *req)
 {
-    ec_soe_request_read(req);
+    return ec_soe_request_read(req);
 }
 
 /****************************************************************************/
 
-void ecrt_soe_request_write(ec_soe_request_t *req)
+int ecrt_soe_request_write(ec_soe_request_t *req)
 {
-    ec_soe_request_write(req);
+    return ec_soe_request_write(req);
 }
 
 /****************************************************************************/
diff --git a/master/soe_request.h b/master/soe_request.h
index 67422ff7..ced4c9a1 100644
--- a/master/soe_request.h
+++ b/master/soe_request.h
@@ -67,8 +67,8 @@ void ec_soe_request_set_idn(ec_soe_request_t *, uint16_t);
 int ec_soe_request_alloc(ec_soe_request_t *, size_t);
 int ec_soe_request_copy_data(ec_soe_request_t *, const uint8_t *, size_t);
 int ec_soe_request_append_data(ec_soe_request_t *, const uint8_t *, size_t);
-void ec_soe_request_read(ec_soe_request_t *);
-void ec_soe_request_write(ec_soe_request_t *);
+int ec_soe_request_read(ec_soe_request_t *);
+int ec_soe_request_write(ec_soe_request_t *);
 int ec_soe_request_timed_out(const ec_soe_request_t *);
 
 /****************************************************************************/