Enable specifying no events when registring with the iomux

src/iomux_epoll.c

@@ -59,16 +59,6 @@ static int iomux_epoll_update_events(struct IOMux *mux_, struct IOMuxFD *fd)
     struct epoll_event e_event = {0, {0}};
     int rc;
    
-    //if we EPOLL_CTL_MOD with events of 0, epoll
-    //will still wait for HUP/ERR , which can lead to
-    //strange things. (e.g. updating fd->what to 0 on a pipe
-    //in order to try to "pause" reading can lead to missing or false
-    //read events.
-    assert(fd->what != 0);
-    if (fd->what == 0)
-        return EINVAL;
-
-
     e_event.events = mux_2_epoll_events(fd->what);
     e_event.data.ptr = fd;
     
@@ -86,7 +76,7 @@ static int iomux_epoll_register_fd(struct IOMux *mux_, struct IOMuxFD *fd)
     struct epoll_event e_event = {0, {0}};
     int rc;
 
-    if (fd->what == 0 || fd->callback == NULL)
+    if (fd->callback == NULL)
         return EINVAL;
 
     e_event.events = mux_2_epoll_events(fd->what);

src/iomux_select.c

@@ -65,7 +65,7 @@ static int iomux_select_register_fd(struct IOMux *mux_, struct IOMuxFD *fd)
     struct IOMuxSelect *mux = mux_->instance;
     int rc;
 
-    if ((fd->what & MUX_EV_MASK) == 0 || fd->callback == NULL)
+    if (fd->callback == NULL)
         return EINVAL;
 
     rc = iomux_select_update_events(mux_, fd);