net: x25: Remove unimplemented X.25-over-LLC code stubs

According to the X.25 documentation, there was a plan to implement
X.25-over-802.2-LLC. It never finished but left various code stubs in the
X.25 code. At this time it is unlikely that it would ever finish so it
may be better to remove those code stubs.

Also change the documentation to make it clear that this is not a ongoing
plan anymore. Change words like "will" to "could", "would", etc.

Cc: Martin Schiller <ms@dev.tdt.de>
Signed-off-by: Xie He <xie.he.0141@gmail.com>
Link: https://lore.kernel.org/r/20201209033346.83742-1-xie.he.0141@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

Documentation/networking/x25.rst

@@ -19,13 +19,11 @@ implementation of LAPB. Therefore the LAPB modules would be called by
 unintelligent X.25 card drivers and not by intelligent ones, this would
 provide a uniform device driver interface, and simplify configuration.
 
-To confuse matters a little, an 802.2 LLC implementation for Linux is being
-written which will allow X.25 to be run over an Ethernet (or Token Ring) and
-conform with the JNT "Pink Book", this will have a different interface to
-the Packet Layer but there will be no confusion since the class of device
-being served by the LLC will be completely separate from LAPB. The LLC
-implementation is being done as part of another protocol project (SNA) and
-by a different author.
+To confuse matters a little, an 802.2 LLC implementation is also possible
+which could allow X.25 to be run over an Ethernet (or Token Ring) and
+conform with the JNT "Pink Book", this would have a different interface to
+the Packet Layer but there would be no confusion since the class of device
+being served by the LLC would be completely separate from LAPB.
 
 Just when you thought that it could not become more confusing, another
 option appeared, XOT. This allows X.25 Packet Layer frames to operate over

net/x25/af_x25.c

@@ -211,11 +211,7 @@ static int x25_device_event(struct notifier_block *this, unsigned long event,
 	if (!net_eq(dev_net(dev), &init_net))
 		return NOTIFY_DONE;
 
-	if (dev->type == ARPHRD_X25
-#if IS_ENABLED(CONFIG_LLC)
-	 || dev->type == ARPHRD_ETHER
-#endif
-	 ) {
+	if (dev->type == ARPHRD_X25) {
 		switch (event) {
 		case NETDEV_REGISTER:
 		case NETDEV_POST_TYPE_CHANGE:

net/x25/x25_dev.c

@@ -160,10 +160,6 @@ void x25_establish_link(struct x25_neigh *nb)
 		*ptr = X25_IFACE_CONNECT;
 		break;
 
-#if IS_ENABLED(CONFIG_LLC)
-	case ARPHRD_ETHER:
-		return;
-#endif
 	default:
 		return;
 	}
@@ -179,10 +175,6 @@ void x25_terminate_link(struct x25_neigh *nb)
 	struct sk_buff *skb;
 	unsigned char *ptr;
 
-#if IS_ENABLED(CONFIG_LLC)
-	if (nb->dev->type == ARPHRD_ETHER)
-		return;
-#endif
 	if (nb->dev->type != ARPHRD_X25)
 		return;
 
@@ -212,11 +204,6 @@ void x25_send_frame(struct sk_buff *skb, struct x25_neigh *nb)
 		*dptr = X25_IFACE_DATA;
 		break;
 
-#if IS_ENABLED(CONFIG_LLC)
-	case ARPHRD_ETHER:
-		kfree_skb(skb);
-		return;
-#endif
 	default:
 		kfree_skb(skb);
 		return;

net/x25/x25_route.c

@@ -124,12 +124,7 @@ struct net_device *x25_dev_get(char *devname)
 {
 	struct net_device *dev = dev_get_by_name(&init_net, devname);
 
-	if (dev &&
-	    (!(dev->flags & IFF_UP) || (dev->type != ARPHRD_X25
-#if IS_ENABLED(CONFIG_LLC)
-					&& dev->type != ARPHRD_ETHER
-#endif
-					))){
+	if (dev && (!(dev->flags & IFF_UP) || dev->type != ARPHRD_X25)) {
 		dev_put(dev);
 		dev = NULL;
 	}