net/rdcli_simple: improved doc and error handling

sys/include/net/rdcli_simple.h

 /*
- * Copyright (C) 2017 Freie Universität Berlin
+ * Copyright (C) 2017-2018 Freie Universität Berlin
  *
  * This file is subject to the terms and conditions of the GNU Lesser
  * General Public License v2.1. See the file LICENSE in the top level
@@ -26,9 +26,21 @@
 extern "C" {
 #endif
 
+/**
+ * @brief   Error codes used by the rdcli_simple implementation
+ */
+enum {
+    RDCLI_SIMPLE_OK  = 0,       /**< all ok */
+    RDCLI_SIMPLE_ERR = -1,      /**< return for formatting and network errors */
+};
+
 /**
  * @brief   Initiate the node registration by sending an empty CoAP POST message
  *          to the RD server's /.well-known/core resource
+ *
+ * @return  RDCLI_SIMPLE_OK on success
+ * @return  RDCLI_ERROR if something goes wrong preparing or sending the
+ *          initial request
  */
 int rdcli_simple_register(void);
 

sys/net/application_layer/rdcli_simple/rdcli_simple.c

@@ -42,19 +42,21 @@ static const sock_udp_ep_t remote = {
 int rdcli_simple_register(void)
 {
     /* build the initial CON packet */
-    int res = gcoap_req_init(&pkt, buf, sizeof(buf), COAP_METHOD_POST,
-                             "/.well-known/core");
-    if (res < 0) {
-        return res;
+    if (gcoap_req_init(&pkt, buf, sizeof(buf), COAP_METHOD_POST,
+                             "/.well-known/core") < 0) {
+        return RDCLI_SIMPLE_ERR;
     }
     /* make packet confirmable */
     coap_hdr_set_type(pkt.hdr, COAP_TYPE_CON);
     /* add Uri-Query options */
-    res = rdcli_common_add_qstring(&pkt);
-    if (res < 0) {
-        return res;
+    if (rdcli_common_add_qstring(&pkt) < 0) {
+        return RDCLI_SIMPLE_ERR;
     }
     /* finish, we don't have any payload */
     ssize_t len = gcoap_finish(&pkt, 0, COAP_FORMAT_LINK);
-    return (int)gcoap_req_send2(buf, len, &remote, NULL);
+    if (gcoap_req_send2(buf, len, &remote, NULL) == 0) {
+        return RDCLI_SIMPLE_ERR;
+    }
+
+    return RDCLI_SIMPLE_OK;
 }

sys/net/application_layer/rdcli_simple/rdcli_simple_standalone.c

@@ -38,8 +38,7 @@ static void *reg_runner(void *arg)
     xtimer_sleep(RDCLI_STARTUP_DELAY);
 
     while (1) {
-        int res = rdcli_simple_register();
-        if (res < 0) {
+        if (rdcli_simple_register() != RDCLI_SIMPLE_OK) {
             LOG_ERROR("[rdcli_simple] error: unable to trigger registration\n");
         }
         xtimer_sleep(RDCLI_UPDATE_INTERVAL);