patch-2.3.21 linux/drivers/net/wan/x25_asy.c

• Lines: 944
• Date: Mon Oct 11 10:13:25 1999
• Orig file: v2.3.20/linux/drivers/net/wan/x25_asy.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.20/linux/drivers/net/wan/x25_asy.c linux/drivers/net/wan/x25_asy.c
@@ -0,0 +1,943 @@
+/*
+ *	Things to sort out:
+ *
+ *	o	tbusy handling
+ *	o	allow users to set the parameters
+ *	o	sync/async switching ?
+ *
+ *	Note: This does _not_ implement CCITT X.25 asynchronous framing
+ *	recommendations. Its primarily for testing purposes. If you wanted
+ *	to do CCITT then in theory all you need is to nick the HDLC async
+ *	checksum routines from ppp.c
+ */
+
+#include <linux/module.h>
+
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <asm/bitops.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/in.h>
+#include <linux/tty.h>
+#include <linux/errno.h>
+#include <linux/netdevice.h>
+#include <linux/etherdevice.h>
+#include <linux/skbuff.h>
+#include <linux/if_arp.h>
+#include <linux/x25.h>
+#include <linux/lapb.h>
+#include <linux/init.h>
+#include "x25_asy.h"
+
+typedef struct x25_ctrl {
+	char		if_name[8];	/* "xasy0\0" .. "xasy99999\0"	*/
+	struct x25_asy	ctrl;		/* X.25 things			*/
+	struct net_device	dev;		/* the device			*/
+} x25_asy_ctrl_t;
+
+static x25_asy_ctrl_t	**x25_asy_ctrls = NULL;
+
+int x25_asy_maxdev = SL_NRUNIT;		/* Can be overridden with insmod! */
+MODULE_PARM(x25_asy_maxdev, "i");
+
+static struct tty_ldisc	x25_ldisc;
+
+static int x25_asy_esc(unsigned char *p, unsigned char *d, int len);
+static void x25_asy_unesc(struct x25_asy *sl, unsigned char c);
+
+/* Find a free X.25 channel, and link in this `tty' line. */
+static inline struct x25_asy *x25_asy_alloc(void)
+{
+	x25_asy_ctrl_t *slp = NULL;
+	int i;
+
+	if (x25_asy_ctrls == NULL)
+		return NULL;	/* Master array missing ! */
+
+	for (i = 0; i < x25_asy_maxdev; i++) 
+	{
+		slp = x25_asy_ctrls[i];
+		/* Not allocated ? */
+		if (slp == NULL)
+			break;
+		/* Not in use ? */
+		if (!test_and_set_bit(SLF_INUSE, &slp->ctrl.flags))
+			break;
+	}
+	/* SLP is set.. */
+
+	/* Sorry, too many, all slots in use */
+	if (i >= x25_asy_maxdev)
+		return NULL;
+
+	/* If no channels are available, allocate one */
+	if (!slp &&
+	    (x25_asy_ctrls[i] = (x25_asy_ctrl_t *)kmalloc(sizeof(x25_asy_ctrl_t),
+						    GFP_KERNEL)) != NULL) {
+		slp = x25_asy_ctrls[i];
+		memset(slp, 0, sizeof(x25_asy_ctrl_t));
+
+		/* Initialize channel control data */
+		set_bit(SLF_INUSE, &slp->ctrl.flags);
+		slp->ctrl.tty         = NULL;
+		sprintf(slp->if_name, "x25asy%d", i);
+		slp->dev.name         = slp->if_name;
+		slp->dev.base_addr    = i;
+		slp->dev.priv         = (void*)&(slp->ctrl);
+		slp->dev.next         = NULL;
+		slp->dev.init         = x25_asy_init;
+	}
+	if (slp != NULL) 
+	{
+
+		/* register device so that it can be ifconfig'ed       */
+		/* x25_asy_init() will be called as a side-effect      */
+		/* SIDE-EFFECT WARNING: x25_asy_init() CLEARS slp->ctrl ! */
+
+		if (register_netdev(&(slp->dev)) == 0) 
+		{
+			/* (Re-)Set the INUSE bit.   Very Important! */
+			set_bit(SLF_INUSE, &slp->ctrl.flags);
+			slp->ctrl.dev = &(slp->dev);
+			slp->dev.priv = (void*)&(slp->ctrl);
+			return (&(slp->ctrl));
+		}
+		else
+		{
+			clear_bit(SLF_INUSE,&(slp->ctrl.flags));
+			printk("x25_asy_alloc() - register_netdev() failure.\n");
+		}
+	}
+	return NULL;
+}
+
+
+/* Free an X.25 channel. */
+
+static inline void x25_asy_free(struct x25_asy *sl)
+{
+	/* Free all X.25 frame buffers. */
+	if (sl->rbuff)  {
+		kfree(sl->rbuff);
+	}
+	sl->rbuff = NULL;
+	if (sl->xbuff)  {
+		kfree(sl->xbuff);
+	}
+	sl->xbuff = NULL;
+
+	if (!test_and_clear_bit(SLF_INUSE, &sl->flags)) {
+		printk("%s: x25_asy_free for already free unit.\n", sl->dev->name);
+	}
+}
+
+/* MTU has been changed by the IP layer. Unfortunately we are not told
+   about this, but we spot it ourselves and fix things up. We could be
+   in an upcall from the tty driver, or in an ip packet queue. */
+
+static void x25_asy_changed_mtu(struct x25_asy *sl)
+{
+	struct net_device *dev = sl->dev;
+	unsigned char *xbuff, *rbuff, *oxbuff, *orbuff;
+	int len;
+	unsigned long flags;
+
+	len = dev->mtu * 2;
+
+	xbuff = (unsigned char *) kmalloc (len + 4, GFP_ATOMIC);
+	rbuff = (unsigned char *) kmalloc (len + 4, GFP_ATOMIC);
+
+	if (xbuff == NULL || rbuff == NULL)  
+	{
+		printk("%s: unable to grow X.25 buffers, MTU change cancelled.\n",
+		       sl->dev->name);
+		dev->mtu = sl->mtu;
+		if (xbuff != NULL)  
+			kfree(xbuff);
+		if (rbuff != NULL)  
+			kfree(rbuff);
+		return;
+	}
+
+	save_flags(flags); 
+	cli();
+
+	oxbuff    = sl->xbuff;
+	sl->xbuff = xbuff;
+	orbuff    = sl->rbuff;
+	sl->rbuff = rbuff;
+
+	if (sl->xleft)  {
+		if (sl->xleft <= len)  {
+			memcpy(sl->xbuff, sl->xhead, sl->xleft);
+		} else  {
+			sl->xleft = 0;
+			sl->tx_dropped++;
+		}
+	}
+	sl->xhead = sl->xbuff;
+
+	if (sl->rcount)  {
+		if (sl->rcount <= len) {
+			memcpy(sl->rbuff, orbuff, sl->rcount);
+		} else  {
+			sl->rcount = 0;
+			sl->rx_over_errors++;
+			set_bit(SLF_ERROR, &sl->flags);
+		}
+	}
+	sl->mtu      = dev->mtu;
+
+	sl->buffsize = len;
+
+	restore_flags(flags);
+
+	if (oxbuff != NULL) 
+		kfree(oxbuff);
+	if (orbuff != NULL)
+		kfree(orbuff);
+}
+
+
+/* Set the "sending" flag.  This must be atomic, hence the ASM. */
+
+static inline void x25_asy_lock(struct x25_asy *sl)
+{
+	if (test_and_set_bit(0, (void *) &sl->dev->tbusy))
+		printk("%s: trying to lock already locked device!\n", sl->dev->name);
+}
+
+
+/* Clear the "sending" flag.  This must be atomic, hence the ASM. */
+
+static inline void x25_asy_unlock(struct x25_asy *sl)
+{
+	if (!test_and_clear_bit(0, (void *)&sl->dev->tbusy))
+		printk("%s: trying to unlock already unlocked device!\n", sl->dev->name);
+}
+
+/* Send one completely decapsulated IP datagram to the IP layer. */
+
+static void x25_asy_bump(struct x25_asy *sl)
+{
+	struct sk_buff *skb;
+	int count;
+	int err;
+
+	count = sl->rcount;
+	sl->rx_bytes+=count;
+	
+	skb = dev_alloc_skb(count+1);
+	if (skb == NULL)  
+	{
+		printk("%s: memory squeeze, dropping packet.\n", sl->dev->name);
+		sl->rx_dropped++;
+		return;
+	}
+	skb_push(skb,1);	/* LAPB internal control */
+	skb->dev = sl->dev;
+	memcpy(skb_put(skb,count), sl->rbuff, count);
+	skb->mac.raw=skb->data;
+	skb->protocol=htons(ETH_P_X25);
+	if((err=lapb_data_received(sl,skb))!=LAPB_OK)
+	{
+		kfree_skb(skb);
+		printk(KERN_DEBUG "x25_asy: data received err - %d\n",err);
+	}
+	else
+	{
+		netif_rx(skb);
+		sl->rx_packets++;
+	}
+}
+
+/* Encapsulate one IP datagram and stuff into a TTY queue. */
+static void x25_asy_encaps(struct x25_asy *sl, unsigned char *icp, int len)
+{
+	unsigned char *p;
+	int actual, count;
+
+
+	if (sl->mtu != sl->dev->mtu) {	/* Someone has been ifconfigging */
+
+		x25_asy_changed_mtu(sl);
+	}
+
+	if (len > sl->mtu) 
+	{		/* Sigh, shouldn't occur BUT ... */
+		len = sl->mtu;
+		printk ("%s: truncating oversized transmit packet!\n", sl->dev->name);
+		sl->tx_dropped++;
+		x25_asy_unlock(sl);
+		return;
+	}
+
+	p = icp;
+	count = x25_asy_esc(p, (unsigned char *) sl->xbuff, len);
+
+	/* Order of next two lines is *very* important.
+	 * When we are sending a little amount of data,
+	 * the transfer may be completed inside driver.write()
+	 * routine, because it's running with interrupts enabled.
+	 * In this case we *never* got WRITE_WAKEUP event,
+	 * if we did not request it before write operation.
+	 *       14 Oct 1994  Dmitry Gorodchanin.
+	 */
+	sl->tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
+	actual = sl->tty->driver.write(sl->tty, 0, sl->xbuff, count);
+	sl->xleft = count - actual;
+	sl->xhead = sl->xbuff + actual;
+	/* VSV */
+	clear_bit(SLF_OUTWAIT, &sl->flags);	/* reset outfill flag */
+}
+
+/*
+ * Called by the driver when there's room for more data.  If we have
+ * more packets to send, we send them here.
+ */
+static void x25_asy_write_wakeup(struct tty_struct *tty)
+{
+	int actual;
+	struct x25_asy *sl = (struct x25_asy *) tty->disc_data;
+
+	/* First make sure we're connected. */
+	if (!sl || sl->magic != X25_ASY_MAGIC || !sl->dev->start)
+		return;
+
+	if (sl->xleft <= 0)  
+	{
+		/* Now serial buffer is almost free & we can start
+		 * transmission of another packet */
+		sl->tx_packets++;
+		tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
+		x25_asy_unlock(sl);
+		mark_bh(NET_BH);
+		return;
+	}
+
+	actual = tty->driver.write(tty, 0, sl->xhead, sl->xleft);
+	sl->xleft -= actual;
+	sl->xhead += actual;
+}
+
+/* Encapsulate an IP datagram and kick it into a TTY queue. */
+
+static int x25_asy_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct x25_asy *sl = (struct x25_asy*)(dev->priv);
+	int err;
+
+	if (!dev->start)  
+	{
+		printk("%s: xmit call when iface is down\n", dev->name);
+		return 1;
+	}
+	
+	switch(skb->data[0])
+	{
+		case 0x00:break;
+		case 0x01: /* Connection request .. do nothing */
+			if((err=lapb_connect_request(sl))!=LAPB_OK)
+				printk(KERN_ERR "x25_asy: lapb_connect_request error - %d\n", err);
+			kfree_skb(skb);
+			return 0;
+		case 0x02: /* Disconnect request .. do nothing - hang up ?? */
+			if((err=lapb_disconnect_request(sl))!=LAPB_OK)
+				printk(KERN_ERR "x25_asy: lapb_disconnect_request error - %d\n", err);
+		default:
+			kfree_skb(skb);
+			return  0;
+	}
+	skb_pull(skb,1);	/* Remove control byte */
+	/*
+	 * If we are busy already- too bad.  We ought to be able
+	 * to queue things at this point, to allow for a little
+	 * frame buffer.  Oh well...
+	 * -----------------------------------------------------
+	 * I hate queues in X.25 driver. May be it's efficient,
+	 * but for me latency is more important. ;)
+	 * So, no queues !
+	 *        14 Oct 1994  Dmitry Gorodchanin.
+	 */
+	if (dev->tbusy) {
+		/* May be we must check transmitter timeout here ?
+		 *      14 Oct 1994 Dmitry Gorodchanin.
+		 */
+#ifdef SL_CHECK_TRANSMIT
+		if (jiffies - dev->trans_start  < 20 * HZ)  {
+			/* 20 sec timeout not reached */
+			return 1;
+		}
+		printk("%s: transmit timed out, %s?\n", dev->name,
+		       (sl->tty->driver.chars_in_buffer(sl->tty) || sl->xleft) ?
+		       "bad line quality" : "driver error");
+		sl->xleft = 0;
+		sl->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
+		x25_asy_unlock(sl);
+#else
+		return 1;
+#endif
+	}
+	
+	if((err=lapb_data_request(sl,skb))!=LAPB_OK)
+	{
+		printk(KERN_ERR "lapbeth: lapb_data_request error - %d\n", err);
+		kfree_skb(skb);
+		return 0;
+	}
+	return 0;
+}
+
+
+/*
+ *	LAPB interface boilerplate
+ */
+
+/*
+ *	Called when I frame data arrives. We did the work above - throw it
+ *	at the net layer.
+ */
+  
+static void x25_asy_data_indication(void *token, struct sk_buff *skb)
+{
+	netif_rx(skb);
+}
+
+/*
+ *	Data has emerged from the LAPB protocol machine. We don't handle
+ *	busy cases too well. Its tricky to see how to do this nicely -
+ *	perhaps lapb should allow us to bounce this ?
+ */
+ 
+static void x25_asy_data_transmit(void *token, struct sk_buff *skb)
+{
+	struct x25_asy *sl=token;
+	if(sl->dev->tbusy)
+	{
+		printk(KERN_ERR "x25_asy: tbusy drop\n");
+		kfree_skb(skb);
+		return;
+	}
+	/* We were not busy, so we are now... :-) */
+	if (skb != NULL) 
+	{
+		x25_asy_lock(sl);
+		sl->tx_bytes+=skb->len;
+		x25_asy_encaps(sl, skb->data, skb->len);
+		dev_kfree_skb(skb);
+	}
+}
+
+/*
+ *	LAPB connection establish/down information.
+ */
+ 
+static void x25_asy_connected(void *token, int reason)
+{
+	struct x25_asy *sl = token;
+	struct sk_buff *skb;
+	unsigned char *ptr;
+
+	if ((skb = dev_alloc_skb(1)) == NULL) {
+		printk(KERN_ERR "lapbeth: out of memory\n");
+		return;
+	}
+
+	ptr  = skb_put(skb, 1);
+	*ptr = 0x01;
+
+	skb->dev      = sl->dev;
+	skb->protocol = htons(ETH_P_X25);
+	skb->mac.raw  = skb->data;
+	skb->pkt_type = PACKET_HOST;
+
+	netif_rx(skb);
+}
+
+static void x25_asy_disconnected(void *token, int reason)
+{
+	struct x25_asy *sl = token;
+	struct sk_buff *skb;
+	unsigned char *ptr;
+
+	if ((skb = dev_alloc_skb(1)) == NULL) {
+		printk(KERN_ERR "x25_asy: out of memory\n");
+		return;
+	}
+
+	ptr  = skb_put(skb, 1);
+	*ptr = 0x02;
+
+	skb->dev      = sl->dev;
+	skb->protocol = htons(ETH_P_X25);
+	skb->mac.raw  = skb->data;
+	skb->pkt_type = PACKET_HOST;
+
+	netif_rx(skb);
+}
+
+
+/* Open the low-level part of the X.25 channel. Easy! */
+
+static int x25_asy_open(struct net_device *dev)
+{
+	struct lapb_register_struct x25_asy_callbacks;
+	struct x25_asy *sl = (struct x25_asy*)(dev->priv);
+	unsigned long len;
+	int err;
+
+	if (sl->tty == NULL)
+		return -ENODEV;
+
+	/*
+	 * Allocate the X.25 frame buffers:
+	 *
+	 * rbuff	Receive buffer.
+	 * xbuff	Transmit buffer.
+	 */
+
+	len = dev->mtu * 2;
+
+	sl->rbuff = (unsigned char *) kmalloc(len + 4, GFP_KERNEL);
+	if (sl->rbuff == NULL)   {
+		goto norbuff;
+	}
+	sl->xbuff = (unsigned char *) kmalloc(len + 4, GFP_KERNEL);
+	if (sl->xbuff == NULL)   {
+		goto noxbuff;
+	}
+	sl->mtu	     = dev->mtu;
+	sl->buffsize = len;
+	sl->rcount   = 0;
+	sl->xleft    = 0;
+	sl->flags   &= (1 << SLF_INUSE);      /* Clear ESCAPE & ERROR flags */
+
+	dev->tbusy  = 0;
+/*	dev->flags |= IFF_UP; */
+	dev->start  = 1;
+	
+	/*
+	 *	Now attach LAPB
+	 */
+	 
+	x25_asy_callbacks.connect_confirmation=x25_asy_connected;
+	x25_asy_callbacks.connect_indication=x25_asy_connected;
+	x25_asy_callbacks.disconnect_confirmation=x25_asy_disconnected;
+	x25_asy_callbacks.disconnect_indication=x25_asy_disconnected;
+	x25_asy_callbacks.data_indication=x25_asy_data_indication;
+	x25_asy_callbacks.data_transmit=x25_asy_data_transmit;
+
+	if((err=lapb_register(sl, &x25_asy_callbacks))==LAPB_OK)
+		return 0;
+
+	/* Cleanup */
+	kfree(sl->xbuff);
+noxbuff:
+	kfree(sl->rbuff);
+norbuff:
+	return -ENOMEM;
+}
+
+
+/* Close the low-level part of the X.25 channel. Easy! */
+static int x25_asy_close(struct net_device *dev)
+{
+	struct x25_asy *sl = (struct x25_asy*)(dev->priv);
+	int err;
+
+	if (sl->tty == NULL)
+		return -EBUSY;
+
+	sl->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
+	dev->tbusy = 1;
+	dev->start = 0;
+	if((err=lapb_unregister(sl))!=LAPB_OK)
+		printk(KERN_ERR "x25_asy_close: lapb_unregister error -%d\n",err);
+
+/*	dev->flags &= ~IFF_UP; */
+	return 0;
+}
+
+static int x25_asy_receive_room(struct tty_struct *tty)
+{
+	return 65536;  /* We can handle an infinite amount of data. :-) */
+}
+
+/*
+ * Handle the 'receiver data ready' interrupt.
+ * This function is called by the 'tty_io' module in the kernel when
+ * a block of X.25 data has been received, which can now be decapsulated
+ * and sent on to some IP layer for further processing.
+ */
+ 
+static void x25_asy_receive_buf(struct tty_struct *tty, const unsigned char *cp, char *fp, int count)
+{
+	struct x25_asy *sl = (struct x25_asy *) tty->disc_data;
+
+	if (!sl || sl->magic != X25_ASY_MAGIC || !sl->dev->start)
+		return;
+
+	/*
+	 * Argh! mtu change time! - costs us the packet part received
+	 * at the change
+	 */
+	if (sl->mtu != sl->dev->mtu)  {
+
+		x25_asy_changed_mtu(sl);
+	}
+
+	/* Read the characters out of the buffer */
+	while (count--) {
+		if (fp && *fp++) {
+			if (!test_and_set_bit(SLF_ERROR, &sl->flags))  {
+				sl->rx_errors++;
+			}
+			cp++;
+			continue;
+		}
+		x25_asy_unesc(sl, *cp++);
+	}
+}
+
+/*
+ * Open the high-level part of the X.25 channel.
+ * This function is called by the TTY module when the
+ * X.25 line discipline is called for.  Because we are
+ * sure the tty line exists, we only have to link it to
+ * a free X.25 channel...
+ */
+
+static int x25_asy_open_tty(struct tty_struct *tty)
+{
+	struct x25_asy *sl = (struct x25_asy *) tty->disc_data;
+	int err;
+
+	/* First make sure we're not already connected. */
+	if (sl && sl->magic == X25_ASY_MAGIC) {
+		return -EEXIST;
+	}
+
+	/* OK.  Find a free X.25 channel to use. */
+	if ((sl = x25_asy_alloc()) == NULL) {
+		return -ENFILE;
+	}
+
+	sl->tty = tty;
+	tty->disc_data = sl;
+	if (tty->driver.flush_buffer)  {
+		tty->driver.flush_buffer(tty);
+	}
+	if (tty->ldisc.flush_buffer)  {
+		tty->ldisc.flush_buffer(tty);
+	}
+
+	/* Restore default settings */
+	sl->dev->type = ARPHRD_X25;
+	
+	/* Perform the low-level X.25 async init */
+	if ((err = x25_asy_open(sl->dev)))
+		return err;
+
+	MOD_INC_USE_COUNT;
+
+	/* Done.  We have linked the TTY line to a channel. */
+	return sl->dev->base_addr;
+}
+
+
+/*
+ * Close down an X.25 channel.
+ * This means flushing out any pending queues, and then restoring the
+ * TTY line discipline to what it was before it got hooked to X.25
+ * (which usually is TTY again).
+ */
+static void x25_asy_close_tty(struct tty_struct *tty)
+{
+	struct x25_asy *sl = (struct x25_asy *) tty->disc_data;
+
+	/* First make sure we're connected. */
+	if (!sl || sl->magic != X25_ASY_MAGIC)
+		return;
+
+	if (sl->dev->flags & IFF_UP)
+	{
+		(void) dev_close(sl->dev);
+	}
+
+	tty->disc_data = 0;
+	sl->tty = NULL;
+	x25_asy_free(sl);
+	unregister_netdev(sl->dev);
+	MOD_DEC_USE_COUNT;
+}
+
+
+static struct net_device_stats *x25_asy_get_stats(struct net_device *dev)
+{
+	static struct net_device_stats stats;
+	struct x25_asy *sl = (struct x25_asy*)(dev->priv);
+
+	memset(&stats, 0, sizeof(struct net_device_stats));
+
+	stats.rx_packets     = sl->rx_packets;
+	stats.tx_packets     = sl->tx_packets;
+	stats.rx_bytes	     = sl->rx_bytes;
+	stats.tx_bytes	     = sl->tx_bytes;
+	stats.rx_dropped     = sl->rx_dropped;
+	stats.tx_dropped     = sl->tx_dropped;
+	stats.tx_errors      = sl->tx_errors;
+	stats.rx_errors      = sl->rx_errors;
+	stats.rx_over_errors = sl->rx_over_errors;
+	return (&stats);
+}
+
+
+ /************************************************************************
+  *			STANDARD X.25 ENCAPSULATION		  	 *
+  ************************************************************************/
+
+int x25_asy_esc(unsigned char *s, unsigned char *d, int len)
+{
+	unsigned char *ptr = d;
+	unsigned char c;
+
+	/*
+	 * Send an initial END character to flush out any
+	 * data that may have accumulated in the receiver
+	 * due to line noise.
+	 */
+
+	*ptr++ = X25_END;	/* Send 10111110 bit seq */
+
+	/*
+	 * For each byte in the packet, send the appropriate
+	 * character sequence, according to the X.25 protocol.
+	 */
+
+	while (len-- > 0) 
+	{
+		switch(c = *s++) 
+		{
+			case X25_END:
+				*ptr++ = X25_ESC;
+				*ptr++ = X25_ESCAPE(X25_END);
+				break;
+			case X25_ESC:
+				*ptr++ = X25_ESC;
+				*ptr++ = X25_ESCAPE(X25_ESC);
+				break;
+			 default:
+				*ptr++ = c;
+				break;
+		}
+	}
+	*ptr++ = X25_END;
+	return (ptr - d);
+}
+
+static void x25_asy_unesc(struct x25_asy *sl, unsigned char s)
+{
+
+	switch(s) 
+	{
+		case X25_END:
+			if (!test_and_clear_bit(SLF_ERROR, &sl->flags) && (sl->rcount > 2))  
+			{
+				x25_asy_bump(sl);
+			}
+			clear_bit(SLF_ESCAPE, &sl->flags);
+			sl->rcount = 0;
+			return;
+
+		case X25_ESC:
+			set_bit(SLF_ESCAPE, &sl->flags);
+			return;
+			
+		case X25_ESCAPE(X25_ESC):
+		case X25_ESCAPE(X25_END):
+			if (test_and_clear_bit(SLF_ESCAPE, &sl->flags))
+				s = X25_UNESCAPE(s);
+			break;
+	}
+	if (!test_bit(SLF_ERROR, &sl->flags))  
+	{
+		if (sl->rcount < sl->buffsize)  
+		{
+			sl->rbuff[sl->rcount++] = s;
+			return;
+		}
+		sl->rx_over_errors++;
+		set_bit(SLF_ERROR, &sl->flags);
+	}
+}
+
+
+/* Perform I/O control on an active X.25 channel. */
+static int x25_asy_ioctl(struct tty_struct *tty, void *file, int cmd, void *arg)
+{
+	struct x25_asy *sl = (struct x25_asy *) tty->disc_data;
+
+	/* First make sure we're connected. */
+	if (!sl || sl->magic != X25_ASY_MAGIC) {
+		return -EINVAL;
+	}
+
+	switch(cmd) 
+	{
+		case SIOCGIFNAME:
+			if(copy_to_user(arg, sl->dev->name, strlen(sl->dev->name) + 1))
+				return -EFAULT;
+			return 0;
+
+		case SIOCSIFHWADDR:
+			return -EINVAL;
+
+		/* Allow stty to read, but not set, the serial port */
+		case TCGETS:
+		case TCGETA:
+			return n_tty_ioctl(tty, (struct file *) file, cmd, (unsigned long) arg);
+
+		default:
+			return -ENOIOCTLCMD;
+	}
+}
+
+static int x25_asy_open_dev(struct net_device *dev)
+{
+	struct x25_asy *sl = (struct x25_asy*)(dev->priv);
+	if(sl->tty==NULL)
+		return -ENODEV;
+	return 0;
+}
+
+/* Initialize X.25 control device -- register X.25 line discipline */
+#ifdef MODULE
+static int x25_asy_init_ctrl_dev(void)
+#else	/* !MODULE */
+int __init x25_asy_init_ctrl_dev(struct net_device *dummy)
+#endif	/* !MODULE */
+{
+	int status;
+
+	if (x25_asy_maxdev < 4) x25_asy_maxdev = 4; /* Sanity */
+
+	printk(KERN_INFO "X.25 async: version 0.00 ALPHA (dynamic channels, max=%d).\n",
+		x25_asy_maxdev );
+	x25_asy_ctrls = (x25_asy_ctrl_t **) kmalloc(sizeof(void*)*x25_asy_maxdev, GFP_KERNEL);
+	if (x25_asy_ctrls == NULL)
+	{
+		printk("X25 async: Can't allocate x25_asy_ctrls[] array!  Uaargh! (-> No X.25 available)\n");
+		return -ENOMEM;
+	}
+
+	/* Clear the pointer array, we allocate devices when we need them */
+	memset(x25_asy_ctrls, 0, sizeof(void*)*x25_asy_maxdev); /* Pointers */
+
+	/* Fill in our line protocol discipline, and register it */
+	memset(&x25_ldisc, 0, sizeof(x25_ldisc));
+	x25_ldisc.magic  = TTY_LDISC_MAGIC;
+	x25_ldisc.name   = "X.25";
+	x25_ldisc.flags  = 0;
+	x25_ldisc.open   = x25_asy_open_tty;
+	x25_ldisc.close  = x25_asy_close_tty;
+	x25_ldisc.read   = NULL;
+	x25_ldisc.write  = NULL;
+	x25_ldisc.ioctl  = (int (*)(struct tty_struct *, struct file *,
+				   unsigned int, unsigned long)) x25_asy_ioctl;
+	x25_ldisc.poll   = NULL;
+	x25_ldisc.receive_buf = x25_asy_receive_buf;
+	x25_ldisc.receive_room = x25_asy_receive_room;
+	x25_ldisc.write_wakeup = x25_asy_write_wakeup;
+	if ((status = tty_register_ldisc(N_X25, &x25_ldisc)) != 0)  {
+		printk("X.25 async: can't register line discipline (err = %d)\n", status);
+	}
+
+#ifdef MODULE
+	return status;
+#else
+	/* Return "not found", so that dev_init() will unlink
+	 * the placeholder device entry for us.
+	 */
+	return ENODEV;
+#endif
+      }
+
+
+/* Initialise the X.25 driver.  Called by the device init code */
+
+int x25_asy_init(struct net_device *dev)
+{
+	struct x25_asy *sl = (struct x25_asy*)(dev->priv);
+
+	if (sl == NULL)		/* Allocation failed ?? */
+		return -ENODEV;
+
+	/* Set up the control block. (And clear statistics) */
+
+	memset(sl, 0, sizeof (struct x25_asy));
+	sl->magic  = X25_ASY_MAGIC;
+	sl->dev	   = dev;
+
+	/*
+	 *	Finish setting up the DEVICE info. 
+	 */
+	 
+	dev->mtu		= SL_MTU;
+	dev->hard_start_xmit	= x25_asy_xmit;
+	dev->open		= x25_asy_open_dev;
+	dev->stop		= x25_asy_close;
+	dev->get_stats	        = x25_asy_get_stats;
+	dev->hard_header_len	= 0;
+	dev->addr_len		= 0;
+	dev->type		= ARPHRD_X25;
+	dev->tx_queue_len	= 10;
+
+	dev_init_buffers(dev);
+	
+	/* New-style flags. */
+	dev->flags		= IFF_NOARP;
+
+	return 0;
+}
+#ifdef MODULE
+
+int
+init_module(void)
+{
+	return x25_asy_init_ctrl_dev();
+}
+
+void
+cleanup_module(void)
+{
+	int i;
+
+	if (x25_asy_ctrls != NULL)
+	{
+		for (i = 0; i < x25_asy_maxdev; i++)
+		{
+			if (x25_asy_ctrls[i])
+			{
+				/*
+				 * VSV = if dev->start==0, then device
+				 * unregistered while close proc.
+				 */
+				if (x25_asy_ctrls[i]->dev.start)
+					unregister_netdev(&(x25_asy_ctrls[i]->dev));
+
+				kfree(x25_asy_ctrls[i]);
+				x25_asy_ctrls[i] = NULL;
+			}
+		}
+		kfree(x25_asy_ctrls);
+		x25_asy_ctrls = NULL;
+	}
+	if ((i = tty_register_ldisc(N_X25, NULL)))
+	{
+		printk("X.25 async: can't unregister line discipline (err = %d)\n", i);
+	}
+}
+#endif /* MODULE */
+