no close call in I2C API anymore

- Not done in any examples or in official docs. This should not
  be an issue, but let's do it like it's recommended officially..

src/fsfw_hal/linux/i2c/I2cComIF.cpp

@@ -98,9 +98,9 @@ ReturnValue_t I2cComIF::sendMessage(CookieIF* cookie, const uint8_t* sendData, s
   }
 
   const auto& deviceFile = i2cCookie->getDeviceFile();
-  UnixFileGuard fileHelper(deviceFile, fd, O_RDWR, "I2cComIF::sendMessage");
-  if (fileHelper.getOpenResult() != returnvalue::OK) {
-    return fileHelper.getOpenResult();
+  result = openI2cDev(deviceFile, fd);
+  if(result != returnvalue::OK) {
+    return result;
   }
   result = openI2cSlave(deviceFile, i2cAddress, fd);
   if (result != returnvalue::OK) {
@@ -156,9 +156,9 @@ ReturnValue_t I2cComIF::requestReceiveMessage(CookieIF* cookie, size_t requestLe
   i2cDeviceMapIter->second.replyLen = 0;
 
   auto& deviceFile = i2cCookie->getDeviceFile();
-  UnixFileGuard fileHelper(deviceFile, fd, O_RDWR, "I2cComIF::requestReceiveMessage");
-  if (fileHelper.getOpenResult() != returnvalue::OK) {
-    return fileHelper.getOpenResult();
+  result = openI2cDev(deviceFile, fd);
+  if(result != returnvalue::OK) {
+    return result;
   }
   result = openI2cSlave(deviceFile, i2cAddress, fd);
   if (result != returnvalue::OK) {
@@ -235,3 +235,20 @@ ReturnValue_t I2cComIF::openI2cSlave(const std::string& deviceFile, address_t i2
   }
   return returnvalue::OK;
 }
+
+ReturnValue_t I2cComIF::openI2cDev(const std::string &dev, int &fd) {
+  fd = open(dev.c_str(), O_RDWR);
+  if(fd < 0) {
+#if FSFW_VERBOSE_LEVEL >= 1
+#if FSFW_CPP_OSTREAM_ENABLED == 1
+    sif::warning << "I2cComIF: Opening device failed with error code " << errno << ": "
+                 << strerror(errno) << std::endl;
+#else
+    sif::printWarning("I2cComIF: Opening device failed with error code %d: %s\n", errno,
+                      strerror(errno));
+#endif /* FSFW_CPP_OSTREAM_ENABLED == 1 */
+#endif /* FSFW_VERBOSE_LEVEL >= 1 */
+    return returnvalue::FAILED;
+  }
+  return returnvalue::OK;
+}

src/fsfw_hal/linux/i2c/I2cComIF.h

@@ -51,6 +51,8 @@ class I2cComIF : public DeviceCommunicationIF, public SystemObject {
    */
   ReturnValue_t openI2cSlave(const std::string &deviceFile, address_t i2cAddress,
                              int &fileDescriptor);
+  ReturnValue_t openI2cDev(const std::string& dev, int&fd);
+
 };
 
 #endif /* LINUX_I2C_I2COMIF_H_ */