X25: Add if_x25.h and x25 to device identifiers

V2 Feedback from John Hughes.
- Add header for userspace implementations such as xot/xoe to use
- Use explicit values for interface stability
- No changes to driver patches

V1
- Use identifiers instead of magic numbers for X25 layer 3 to device interface.
- Also fixed checkpatch notes on updated code.

[ Add new user header to include/linux/Kbuild  -DaveM ]

Signed-off-by: Andrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/x25/x25_dev.c b/net/x25/x25_dev.c
index b9ef682..9005f6d 100644
--- a/net/x25/x25_dev.c
+++ b/net/x25/x25_dev.c
@@ -24,6 +24,7 @@
 #include <net/sock.h>
 #include <linux/if_arp.h>
 #include <net/x25.h>
+#include <net/x25device.h>
 
 static int x25_receive_data(struct sk_buff *skb, struct x25_neigh *nb)
 {
@@ -115,19 +116,22 @@
 	}
 
 	switch (skb->data[0]) {
-		case 0x00:
-			skb_pull(skb, 1);
-			if (x25_receive_data(skb, nb)) {
-				x25_neigh_put(nb);
-				goto out;
-			}
-			break;
-		case 0x01:
-			x25_link_established(nb);
-			break;
-		case 0x02:
-			x25_link_terminated(nb);
-			break;
+
+	case X25_IFACE_DATA:
+		skb_pull(skb, 1);
+		if (x25_receive_data(skb, nb)) {
+			x25_neigh_put(nb);
+			goto out;
+		}
+		break;
+
+	case X25_IFACE_CONNECT:
+		x25_link_established(nb);
+		break;
+
+	case X25_IFACE_DISCONNECT:
+		x25_link_terminated(nb);
+		break;
 	}
 	x25_neigh_put(nb);
 drop:
@@ -148,7 +152,7 @@
 				return;
 			}
 			ptr  = skb_put(skb, 1);
-			*ptr = 0x01;
+			*ptr = X25_IFACE_CONNECT;
 			break;
 
 #if defined(CONFIG_LLC) || defined(CONFIG_LLC_MODULE)
@@ -184,7 +188,7 @@
 	}
 
 	ptr  = skb_put(skb, 1);
-	*ptr = 0x02;
+	*ptr = X25_IFACE_DISCONNECT;
 
 	skb->protocol = htons(ETH_P_X25);
 	skb->dev      = nb->dev;
@@ -200,7 +204,7 @@
 	switch (nb->dev->type) {
 		case ARPHRD_X25:
 			dptr  = skb_push(skb, 1);
-			*dptr = 0x00;
+			*dptr = X25_IFACE_DATA;
 			break;
 
 #if defined(CONFIG_LLC) || defined(CONFIG_LLC_MODULE)