diff --git a/drivers/isdn/i4l/isdn_x25iface.c b/drivers/isdn/i4l/isdn_x25iface.c
new file mode 100644
index 0000000..4ab7600
--- /dev/null
+++ b/drivers/isdn/i4l/isdn_x25iface.c
@@ -0,0 +1,328 @@
+/* $Id: isdn_x25iface.c,v 1.1.2.2 2004/01/12 22:37:19 keil Exp $
+ *
+ * Linux ISDN subsystem, X.25 related functions
+ *
+ * This software may be used and distributed according to the terms
+ * of the GNU General Public License, incorporated herein by reference.
+ *
+ * stuff needed to support the Linux X.25 PLP code on top of devices that
+ * can provide a lab_b service using the concap_proto mechanism.
+ * This module supports a network interface wich provides lapb_sematics
+ * -- as defined in Documentation/networking/x25-iface.txt -- to
+ * the upper layer and assumes that the lower layer provides a reliable
+ * data link service by means of the concap_device_ops callbacks.
+ *
+ * Only protocol specific stuff goes here. Device specific stuff
+ * goes to another -- device related -- concap_proto support source file.
+ *
+ */
+
+/* #include <linux/isdn.h> */
+#include <linux/netdevice.h>
+#include <linux/concap.h>
+#include <linux/wanrouter.h>
+#include <net/x25device.h>
+#include "isdn_x25iface.h"
+
+/* for debugging messages not to cause an oops when device pointer is NULL*/
+#define MY_DEVNAME(dev)  ( (dev) ? (dev)->name : "DEVICE UNSPECIFIED" )
+
+
+typedef struct isdn_x25iface_proto_data {
+	int magic;
+	enum wan_states state;
+	/* Private stuff, not to be accessed via proto_data. We provide the
+	   other storage for the concap_proto instance here as well,
+	   enabling us to allocate both with just one kmalloc(): */ 
+	struct concap_proto priv;
+} ix25_pdata_t;
+
+
+
+/* is now in header file (extern): struct concap_proto * isdn_x25iface_proto_new(void); */
+void isdn_x25iface_proto_del( struct concap_proto * );
+int isdn_x25iface_proto_close( struct concap_proto * );
+int isdn_x25iface_proto_restart( struct concap_proto *,
+				 struct net_device *,
+				 struct concap_device_ops *);
+int isdn_x25iface_xmit( struct concap_proto *, struct sk_buff * );
+int isdn_x25iface_receive( struct concap_proto *, struct sk_buff * );
+int isdn_x25iface_connect_ind( struct concap_proto * );
+int isdn_x25iface_disconn_ind( struct concap_proto * );
+
+
+static struct concap_proto_ops ix25_pops = {
+	&isdn_x25iface_proto_new,
+	&isdn_x25iface_proto_del,
+	&isdn_x25iface_proto_restart,
+	&isdn_x25iface_proto_close,
+	&isdn_x25iface_xmit,
+	&isdn_x25iface_receive,
+	&isdn_x25iface_connect_ind,
+	&isdn_x25iface_disconn_ind
+};
+
+/* error message helper function */
+static void illegal_state_warn( unsigned state, unsigned char firstbyte) 
+{
+	printk( KERN_WARNING "isdn_x25iface: firstbyte %x illegal in"
+		"current state %d\n",firstbyte, state );
+}
+
+/* check protocol data field for consistency */
+static int pdata_is_bad( ix25_pdata_t * pda ){
+
+	if( pda  &&  pda -> magic == ISDN_X25IFACE_MAGIC ) return 0;
+	printk( KERN_WARNING
+		"isdn_x25iface_xxx: illegal pointer to proto data\n" );
+	return 1;
+}
+
+/* create a new x25 interface protocol instance
+ */
+struct concap_proto * isdn_x25iface_proto_new(void)
+{
+	ix25_pdata_t * tmp = kmalloc(sizeof(ix25_pdata_t),GFP_KERNEL);
+	IX25DEBUG("isdn_x25iface_proto_new\n");
+	if( tmp ){
+		tmp -> magic = ISDN_X25IFACE_MAGIC;
+		tmp -> state = WAN_UNCONFIGURED;
+		/* private data space used to hold the concap_proto data.
+		   Only to be accessed via the returned pointer */
+		spin_lock_init(&tmp->priv.lock);
+		tmp -> priv.dops       = NULL;
+		tmp -> priv.net_dev    = NULL;
+		tmp -> priv.pops       = &ix25_pops;
+		tmp -> priv.flags      = 0;
+		tmp -> priv.proto_data = tmp;
+		return( &(tmp -> priv) );
+	}
+	return NULL;
+};
+
+/* close the x25iface encapsulation protocol 
+ */
+int isdn_x25iface_proto_close(struct concap_proto *cprot){
+
+	ix25_pdata_t *tmp;
+        int ret = 0;
+	ulong flags;
+
+	if( ! cprot ){
+		printk( KERN_ERR "isdn_x25iface_proto_close: "
+			"invalid concap_proto pointer\n" );
+		return -1;
+	}
+	IX25DEBUG( "isdn_x25iface_proto_close %s \n", MY_DEVNAME(cprot -> net_dev) );
+	spin_lock_irqsave(&cprot->lock, flags);
+	cprot -> dops    = NULL;
+	cprot -> net_dev = NULL;
+	tmp = cprot -> proto_data;
+	if( pdata_is_bad( tmp ) ){
+		ret = -1;
+	} else {
+		tmp -> state = WAN_UNCONFIGURED;
+	}
+	spin_unlock_irqrestore(&cprot->lock, flags);
+	return ret;
+}
+
+/* Delete the x25iface encapsulation protocol instance
+ */
+void isdn_x25iface_proto_del(struct concap_proto *cprot){
+
+	ix25_pdata_t * tmp;
+ 
+	IX25DEBUG( "isdn_x25iface_proto_del \n" );
+	if( ! cprot ){
+		printk( KERN_ERR "isdn_x25iface_proto_del: "
+			"concap_proto pointer is NULL\n" );
+		return;
+	}
+	tmp = cprot -> proto_data;
+	if( tmp == NULL ){ 
+		printk( KERN_ERR "isdn_x25iface_proto_del: inconsistent "
+			"proto_data pointer (maybe already deleted?)\n"); 
+		return;
+	}
+	/* close if the protocol is still open */
+	if( cprot -> dops ) isdn_x25iface_proto_close(cprot);
+	/* freeing the storage should be sufficient now. But some additional
+	   settings might help to catch wild pointer bugs */
+	tmp -> magic = 0;
+	cprot -> proto_data = NULL;
+
+	kfree( tmp );
+	return;
+}
+
+/* (re-)initialize the data structures for x25iface encapsulation
+ */
+int isdn_x25iface_proto_restart(struct concap_proto *cprot,
+				struct net_device *ndev, 
+				struct concap_device_ops *dops)
+{
+	ix25_pdata_t * pda = cprot -> proto_data ;
+	ulong flags;
+
+	IX25DEBUG( "isdn_x25iface_proto_restart %s \n", MY_DEVNAME(ndev) );
+
+	if ( pdata_is_bad( pda ) ) return -1;
+
+	if( !( dops  && dops -> data_req && dops -> connect_req 
+	       && dops -> disconn_req )  ){
+		printk( KERN_WARNING "isdn_x25iface_restart: required dops"
+			" missing\n" );
+		isdn_x25iface_proto_close(cprot);
+		return -1;
+	}
+	spin_lock_irqsave(&cprot->lock, flags);
+	cprot -> net_dev = ndev;
+	cprot -> pops = &ix25_pops;
+	cprot -> dops = dops;
+	pda -> state = WAN_DISCONNECTED;
+	spin_unlock_irqrestore(&cprot->lock, flags);
+	return 0;
+}
+
+/* deliver a dl_data frame received from i4l HL driver to the network layer 
+ */
+int isdn_x25iface_receive(struct concap_proto *cprot, struct sk_buff *skb)
+{
+  	IX25DEBUG( "isdn_x25iface_receive %s \n", MY_DEVNAME(cprot->net_dev) );
+	if ( ( (ix25_pdata_t*) (cprot->proto_data) ) 
+	     -> state == WAN_CONNECTED ){
+		if( skb_push(skb, 1)){
+			skb -> data[0]=0x00;
+			skb->protocol = x25_type_trans(skb, cprot->net_dev);
+			netif_rx(skb);
+			return 0;
+		}
+	}
+	printk(KERN_WARNING "isdn_x25iface_receive %s: not connected, skb dropped\n", MY_DEVNAME(cprot->net_dev) );
+	dev_kfree_skb(skb);
+	return -1;
+}
+
+/* a connection set up is indicated by lower layer 
+ */
+int isdn_x25iface_connect_ind(struct concap_proto *cprot)
+{
+	struct sk_buff * skb = dev_alloc_skb(1);
+	enum wan_states *state_p 
+	  = &( ( (ix25_pdata_t*) (cprot->proto_data) ) -> state);
+	IX25DEBUG( "isdn_x25iface_connect_ind %s \n"
+		   , MY_DEVNAME(cprot->net_dev) );
+	if( *state_p == WAN_UNCONFIGURED ){ 
+		printk(KERN_WARNING 
+		       "isdn_x25iface_connect_ind while unconfigured %s\n"
+		       , MY_DEVNAME(cprot->net_dev) );
+		return -1;
+	}
+	*state_p = WAN_CONNECTED;
+	if( skb ){
+		*( skb_put(skb, 1) ) = 0x01;
+		skb->protocol = x25_type_trans(skb, cprot->net_dev);
+		netif_rx(skb);
+		return 0;
+	} else {
+		printk(KERN_WARNING "isdn_x25iface_connect_ind: "
+		       " out of memory -- disconnecting\n");
+		cprot -> dops -> disconn_req(cprot);
+		return -1;
+	}
+}
+	
+/* a disconnect is indicated by lower layer 
+ */
+int isdn_x25iface_disconn_ind(struct concap_proto *cprot)
+{
+	struct sk_buff *skb;
+	enum wan_states *state_p 
+	  = &( ( (ix25_pdata_t*) (cprot->proto_data) ) -> state);
+	IX25DEBUG( "isdn_x25iface_disconn_ind %s \n", MY_DEVNAME(cprot -> net_dev) );
+	if( *state_p == WAN_UNCONFIGURED ){ 
+		printk(KERN_WARNING 
+		       "isdn_x25iface_disconn_ind while unconfigured\n");
+		return -1;
+	}
+	if(! cprot -> net_dev) return -1;
+	*state_p = WAN_DISCONNECTED;
+	skb = dev_alloc_skb(1);
+	if( skb ){
+		*( skb_put(skb, 1) ) = 0x02;
+		skb->protocol = x25_type_trans(skb, cprot->net_dev);
+		netif_rx(skb);
+		return 0;
+	} else {
+		printk(KERN_WARNING "isdn_x25iface_disconn_ind:"
+		       " out of memory\n");
+		return -1;
+	}
+}
+
+/* process a frame handed over to us from linux network layer. First byte
+   semantics as defined in Documentation/networking/x25-iface.txt
+   */
+int isdn_x25iface_xmit(struct concap_proto *cprot, struct sk_buff *skb)
+{
+	unsigned char firstbyte = skb->data[0];
+	enum wan_states *state = &((ix25_pdata_t*)cprot->proto_data)->state;
+	int ret = 0;
+	IX25DEBUG( "isdn_x25iface_xmit: %s first=%x state=%d \n", MY_DEVNAME(cprot -> net_dev), firstbyte, *state );
+	switch ( firstbyte ){
+	case 0x00: /* dl_data request */
+		if( *state == WAN_CONNECTED ){
+			skb_pull(skb, 1);
+			cprot -> net_dev -> trans_start = jiffies;
+			ret = ( cprot -> dops -> data_req(cprot, skb) );
+			/* prepare for future retransmissions */
+			if( ret ) skb_push(skb,1);
+			return ret;
+		}
+		illegal_state_warn( *state, firstbyte ); 
+		break;
+	case 0x01: /* dl_connect request */
+		if( *state == WAN_DISCONNECTED ){
+			*state = WAN_CONNECTING;
+		        ret = cprot -> dops -> connect_req(cprot);
+			if(ret){
+				/* reset state and notify upper layer about
+				 * immidiatly failed attempts */
+				isdn_x25iface_disconn_ind(cprot);
+			}
+		} else {
+			illegal_state_warn( *state, firstbyte );
+		}
+		break;
+	case 0x02: /* dl_disconnect request */
+		switch ( *state ){
+		case WAN_DISCONNECTED: 
+			/* Should not happen. However, give upper layer a
+			   chance to recover from inconstistency  but don't
+			   trust the lower layer sending the disconn_confirm
+			   when already disconnected */
+			printk(KERN_WARNING "isdn_x25iface_xmit: disconnect "
+			       " requested while disconnected\n" );
+			isdn_x25iface_disconn_ind(cprot);
+			break; /* prevent infinite loops */
+		case WAN_CONNECTING:
+		case WAN_CONNECTED:
+			*state = WAN_DISCONNECTED;
+			cprot -> dops -> disconn_req(cprot);
+			break;
+		default:
+			illegal_state_warn( *state, firstbyte );
+		}
+		break;
+	case 0x03: /* changing lapb parameters requested */
+		printk(KERN_WARNING "isdn_x25iface_xmit: setting of lapb"
+		       " options not yet supported\n");
+		break;
+	default:
+		printk(KERN_WARNING "isdn_x25iface_xmit: frame with illegal"
+		       " first byte %x ignored:\n", firstbyte);
+	}
+	dev_kfree_skb(skb);
+	return 0;
+}