From 5c137224160535573c5e830230eaebda4616893e Mon Sep 17 00:00:00 2001
From: Gregory Nutt <gnutt@nuttx.org>
Date: Fri, 27 Feb 2015 08:23:14 -0600
Subject: [PATCH] Networking:  Improve the network device registration logic. 
 When multiple link types are used, modify how each interface number is
 assigned to the device name by incrementing the device number individually
 for each interface link type.  From Max Neklyudov.

---
 net/netdev/netdev_register.c | 63 ++++++++++++++++++++++++++++++++++--
 1 file changed, 61 insertions(+), 2 deletions(-)

diff --git a/net/netdev/netdev_register.c b/net/netdev/netdev_register.c
index a1f5c12513..b051194004 100644
--- a/net/netdev/netdev_register.c
+++ b/net/netdev/netdev_register.c
@@ -1,7 +1,7 @@
 /****************************************************************************
  * net/netdev/netdev_register.c
  *
- *   Copyright (C) 2007-2012, 2014 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2012, 2014-2015 Gregory Nutt. All rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -77,7 +77,11 @@
  * Private Data
  ****************************************************************************/
 
+/* Then next available device number */
+
+#ifndef CONFIG_NET_MULTILINK
 static int g_next_devnum = 0;
+#endif
 
 /****************************************************************************
  * Public Data
@@ -91,6 +95,55 @@ struct net_driver_s *g_netdevices = NULL;
  * Private Functions
  ****************************************************************************/
 
+/****************************************************************************
+ * Function: find_devnum
+ *
+ * Description:
+ *   Given a device name format string, find the next device number for the
+ *   class of device represented by that format string.
+ *
+ * Parameters:
+ *   devfmt - The device format string
+ *
+ * Returned Value:
+ *   The next device number for that device class
+ *
+ ****************************************************************************/
+
+#ifdef CONFIG_NET_MULTILINK
+static int find_devnum(FAR const char *devfmt)
+{
+  FAR struct net_driver_s *curr;
+  size_t fmt_size;
+  int result = 0;
+
+  fmt_size = strlen(devfmt);
+
+  /* Assumed that devfmt is xxx%d */
+
+  DEBUGASSERT(fmt_size > 2);
+  fmt_size -= 2;
+
+  /* Search the list of currently registered network devices */
+
+  for (curr = g_netdevices; curr; curr = curr->flink )
+    {
+      /* Does this device name match the format we were given? */
+
+      if (strncmp(curr->d_ifname, devfmt, fmt_size) == 0)
+        {
+          /* Yes.. increment the candidate device number */
+
+          result++;
+        }
+    }
+
+  /* Return this next device number for this format */
+
+  return result;
+}
+#endif
+
 /****************************************************************************
  * Public Functions
  ****************************************************************************/
@@ -179,10 +232,16 @@ int netdev_register(FAR struct net_driver_s *dev, enum net_lltype_e lltype)
      devfmt = NETDEV_DEFAULT_FORMAT;
 #endif
 
-      /* Assign a device name to the interface */
+      /* Get the next available device number and sssign a device name to
+       * the interface
+       */
 
       netdev_semtake();
+#ifdef CONFIG_NET_MULTILINK
+      devnum = find_devnum(devfmt);
+#else
       devnum = g_next_devnum++;
+#endif
       snprintf(dev->d_ifname, IFNAMSIZ, devfmt, devnum );
 
       /* Add the device to the list of known network devices */