Improve doxygen comments

include/ucore/iomux.h

@@ -43,6 +43,9 @@ struct IOMuxFD {
 };
 
 /** Creates a new IOMux. 
+ *
+ * @param type the underlying implementation to use @see IOMUX_TYPE
+ * @return Newly allocated IOMux. NULL if memory allocation fails.
  */
 struct IOMux *iomux_create(enum IOMUX_TYPE type);
 
@@ -58,19 +61,27 @@ struct IOMux *iomux_create_ex(enum IOMUX_TYPE type, struct UCoreClock *uclock);
 void iomux_delete(struct IOMux *mux);
 
 /** Runs the event loop of the mux
- * returns if the number of file descriptors and timers are 0 or 
+ *
+ * @return if the number of file descriptors and timers are 0 or 
  * an error occurs */
 int iomux_run(struct IOMux *mux);
 
-/* Adds a file descriptor to the watch set,
+/* Adds a file descriptor to the watch set.
- * returns 0 on success, an errno value on error */
+ * The file descriptor integer value must reside in only
+ * one struct IOMuxFD. Adding e.g. the same file descriptor
+ * in 2 different struct IOMuxFD, one for read events and one for
+ * write events is not supported.
+ *
+ * @return 0 on success, an errno value on error
+ */
 int iomux_register_fd(struct IOMux *mux, struct IOMuxFD *fd);
 
 /** Removes the file descriptor*/
 int iomux_unregister_fd(struct IOMux *mux, struct IOMuxFD *fd);
 
 /** Updates the events to watch for in fd->what
- * returns 0 on success, an errno value on error */
+ * @return 0 on success, an errno value on error
+ */
 int iomux_update_events(struct IOMux *mux, struct IOMuxFD *fd);
 
 
@@ -100,7 +111,7 @@ int iomux_update_events(struct IOMux *mux, struct IOMuxFD *fd);
     iomux_update_events((mux), (fd));\
 })
 
-/** Returns a UCTimer instance tied to this mux.
+/** @return a UCTimer instance tied to this mux.
  *  Used to schedule timers within this mux.
  */
 struct UCTimers *iomux_get_timers(struct IOMux *mux);