Fixed default values for Ethernet Link Interface Control attribute (#6)

If the Ethernet Link Interface Control attribute has been configured as an
existing attribute (OPENER_ETHLINK_IFACE_CTRL_ENABLE) the default value
used for initialization was wrong.

If autonegotiation is enabled in the Control Bits member of the Interface
Control structure the forced_interface_speed member has to be zero. See
also Vol. 2, section 5-5.3.2.6.2: "If auto-negotiation is enabled,
attempting to set the Forced Interface Speed shall result in status
code 0x0C (Object State Conflict)."

Signed-off-by: Stefan Mätje <stefan.maetje@esd.eu>

source/src/cip/cipethernetlink.c

@@ -216,10 +216,10 @@ EipStatus CipEthernetLinkInit(void) {
 
   /* set attributes to initial values */
   for (size_t idx = 0;  idx < OPENER_ETHLINK_INSTANCE_CNT; ++idx) {
-    g_ethernet_link[idx].interface_speed = 100;
+    g_ethernet_link[idx].interface_speed = 100U;
     /* successful speed and duplex neg, full duplex active link.
      * TODO: in future it should be checked if link is active */
-    g_ethernet_link[idx].interface_flags = 0xF;
+    g_ethernet_link[idx].interface_flags = 0xFU;
 
     g_ethernet_link[idx].interface_type = kEthLinkIfTypeTwistedPair;
     if (2 == idx) {
@@ -232,8 +232,10 @@ EipStatus CipEthernetLinkInit(void) {
     g_ethernet_link[idx].interface_caps.speed_duplex_selector =
       kEthLinkSpeedDpx_100_FD;
 #if defined(OPENER_ETHLINK_IFACE_CTRL_ENABLE) && 0 != OPENER_ETHLINK_IFACE_CTRL_ENABLE
+    /* If auto-negotiation is enabled the forced_interface_speed must not be set, i. e.
+     *  be zero. See Vol. 2, section 5-5.3.2.6.2 */
     g_ethernet_link[idx].interface_control.control_bits = kEthLinkIfCntrlAutonegotiate;
-    g_ethernet_link[idx].interface_control.forced_interface_speed = 100;
+    g_ethernet_link[idx].interface_control.forced_interface_speed = 0U;
 #endif
   }