poll again; if fd is less than zero, it should set revents to zero, not POLLNVAL

ChangeLog

@@ -4777,8 +4777,7 @@
 	* net/net_poll.c: When readahead data is availalbe, the network poll
 	  logic should set POLLIN (or POLLRDNORM), not POLLOUT.  Max Holtzberg
 	  (2013-5-23)
-	* fs/fs_poll.c:  Actually, it should not ignore invlid descriptors, it
-	  should set the POLLNVAL event and return immediately (2013-5-23).
+	* fs/fs_poll.c:  Actually, it should also set revents == 0. (2013-5-23).
 	* libc/misc/lib_slcdencode.c and lib_slcddecode.c:  Add logic to marshal
 	  and serialized special SLCD intermixed with normal ASCII data (2013-5-23)
 	* configs/stm32ldiscovery/src/stm32_lcd.c:  STM32L-Discovery's segment LCD

fs/fs_poll.c

@@ -166,28 +166,22 @@ static inline int poll_setup(FAR struct pollfd *fds, nfds_t nfds, sem_t *sem)
       /* Setup the poll descriptor */
 
       fds[i].sem     = sem;
+      fds[i].revents = 0;
       fds[i].priv    = NULL;
 
-      /* Check for invalid descriptors */
+      /* Check for invalid descriptors. "If the value of fd is less than 0,
+       * events shall be ignored, and revents shall be set to 0 in that entry
+       * on return from poll()."
+       *
+       * NOTE:  There is a potential problem here.  If there is only one fd
+       * and if it is negative, then poll will hang.  From my reading of the
+       * spec, that appears to be the correct behavior.
+       */
 
-      if (fds[i].fd < 0)
-        {
-          /* Set POLLNVAL to indicate the invalid fd member */
-
-          fds[i].revents = POLLNVAL;
-
-          /* And increment the semaphore so that poll will return
-           * immediately (but with a successful return value).
-           */
-
-          sem_post(sem);
-        }
-      else
+      if (fds[i].fd >= 0)
         {
           /* Set up the poll on this valid file descriptor */
 
-          fds[i].revents = 0;
-
           ret = poll_fdsetup(fds[i].fd, &fds[i], true);
           if (ret < 0)
             {