Networking: Add a test to see a device pointer is still valid

net/netdev/Make.defs

@@ -1,7 +1,7 @@
 ############################################################################
 # net/netdev/Make.defs
 #
-#   Copyright (C) 2014 Gregory Nutt. All rights reserved.
+#   Copyright (C) 2014-2015 Gregory Nutt. All rights reserved.
 #   Author: Gregory Nutt <gnutt@nuttx.org>
 #
 # Redistribution and use in source and binary forms, with or without
@@ -38,7 +38,7 @@
 NETDEV_CSRCS += netdev_register.c netdev_ioctl.c netdev_txnotify.c
 NETDEV_CSRCS += netdev_findbyname.c netdev_findbyaddr.c netdev_count.c
 NETDEV_CSRCS += netdev_foreach.c netdev_unregister.c netdev_sem.c
-NETDEV_CSRCS += netdev_carrier.c netdev_default.c
+NETDEV_CSRCS += netdev_carrier.c netdev_default.c netdev_verify.c
 
 ifeq ($(CONFIG_NET_RXAVAIL),y)
 NETDEV_CSRCS += netdev_rxnotify.c

net/netdev/netdev.h

@@ -43,6 +43,7 @@
 #include <nuttx/config.h>
 
 #include <sys/types.h>
+#include <stdbool.h>
 
 #include <nuttx/net/ip.h>
 
@@ -124,6 +125,19 @@ void netdev_semgive(void);
 void netdev_ifup(FAR struct net_driver_s *dev);
 void netdev_ifdown(FAR struct net_driver_s *dev);
 
+/****************************************************************************
+ * Function: netdev_verify
+ *
+ * Description:
+ *   Verify that the specified device still exists
+ *
+ * Assumptions:
+ *   The caller has locked the network.
+ *
+ ****************************************************************************/
+
+bool netdev_verify(FAR struct net_driver_s *dev);
+
 /****************************************************************************
  * Function: netdev_findbyname
  *

net/netdev/netdev_findbyname.c

@@ -89,9 +89,9 @@
  *
  ****************************************************************************/
 
-FAR struct net_driver_s *netdev_findbyname(const char *ifname)
+FAR struct net_driver_s *netdev_findbyname(FAR const char *ifname)
 {
-  struct net_driver_s *dev;
+  FAR struct net_driver_s *dev;
   if (ifname)
     {
       netdev_semtake();