[PATCH] SMP rewrite of mkiss

Rewrite the mkiss driver to make it SMP-proof following the example of
6pack.c.

Signed-off-by: Ralf Baechle DL5RB <ralf@linux-mips.org>
Signed-off-by: Jeff Garzik <jgarzik@pobox.com>

drivers/net/hamradio/Kconfig

@@ -1,6 +1,6 @@
 config MKISS
 	tristate "Serial port KISS driver"
-	depends on AX25 && BROKEN_ON_SMP
+	depends on AX25
 	---help---
 	  KISS is a protocol used for the exchange of data between a computer
 	  and a Terminal Node Controller (a small embedded system commonly

drivers/net/hamradio/mkiss.c

@@ -1,30 +1,19 @@
 /*
- *	MKISS Driver
+ *  This program is free software; you can distribute it and/or modify it
+ *  under the terms of the GNU General Public License (Version 2) as
+ *  published by the Free Software Foundation.
  *
- *	This module:
- *		This module is free software; you can redistribute it and/or
- *		modify it under the terms of the GNU General Public License
- *		as published by the Free Software Foundation; either version
- *		2 of the License, or (at your option) any later version.
+ *  This program is distributed in the hope it will be useful, but WITHOUT
+ *  ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ *  FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ *  for more details.
  *
- * 		This module implements the AX.25 protocol for kernel-based
- *		devices like TTYs. It interfaces between a raw TTY, and the
- *		kernel's AX.25 protocol layers, just like slip.c.
- *		AX.25 needs to be separated from slip.c while slip.c is no
- *		longer a static kernel device since it is a module.
- *		This method clears the way to implement other kiss protocols
- *		like mkiss smack g8bpq ..... so far only mkiss is implemented.
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  59 Temple Place - Suite 330, Boston MA 02111-1307, USA.
  *
- * Hans Alblas <hans@esrac.ele.tue.nl>
- *
- *	History
- *	Jonathan (G4KLX)	Fixed to match Linux networking changes - 2.1.15.
- *	Matthias (DG2FEF)       Added support for FlexNet CRC (on special request)
- *                              Fixed bug in ax25_close(): dev_lock_wait() was
- *                              called twice, causing a deadlock.
- *	Jeroen (PE1RXQ)		Removed old MKISS_MAGIC stuff and calls to
- *				MOD_*_USE_COUNT
- *				Remove cli() and fix rtnl lock usage.
+ * Copyright (C) Hans Alblas PE1AYX <hans@esrac.ele.tue.nl>
+ * Copyright (C) 2004, 05 Ralf Baechle DL5RB <ralf@linux-mips.org>
  */
 
 #include <linux/config.h>
@@ -50,174 +39,296 @@
 
 #include <net/ax25.h>
 
-#include "mkiss.h"
-
 #ifdef CONFIG_INET
 #include <linux/ip.h>
 #include <linux/tcp.h>
 #endif
 
-static char banner[] __initdata = KERN_INFO "mkiss: AX.25 Multikiss, Hans Albas PE1AYX\n";
-
-typedef struct ax25_ctrl {
-	struct ax_disp ctrl;	/* 				*/
-	struct net_device  dev;	/* the device			*/
-} ax25_ctrl_t;
-
-static ax25_ctrl_t **ax25_ctrls;
-
-int ax25_maxdev = AX25_MAXDEV;		/* Can be overridden with insmod! */
-
-static struct tty_ldisc	ax_ldisc;
-
-static int ax25_init(struct net_device *);
-static int kiss_esc(unsigned char *, unsigned char *, int);
-static int kiss_esc_crc(unsigned char *, unsigned char *, unsigned short, int);
-static void kiss_unesc(struct ax_disp *, unsigned char);
+#define AX_MTU		236
+
+/* SLIP/KISS protocol characters. */
+#define END             0300		/* indicates end of frame	*/
+#define ESC             0333		/* indicates byte stuffing	*/
+#define ESC_END         0334		/* ESC ESC_END means END 'data'	*/
+#define ESC_ESC         0335		/* ESC ESC_ESC means ESC 'data'	*/
+
+struct mkiss {
+	struct tty_struct	*tty;	/* ptr to TTY structure		*/
+	struct net_device	*dev;	/* easy for intr handling	*/
+
+	/* These are pointers to the malloc()ed frame buffers. */
+	spinlock_t		buflock;/* lock for rbuf and xbuf */
+	unsigned char		*rbuff;	/* receiver buffer		*/
+	int			rcount;	/* received chars counter       */
+	unsigned char		*xbuff;	/* transmitter buffer		*/
+	unsigned char		*xhead;	/* pointer to next byte to XMIT */
+	int			xleft;	/* bytes left in XMIT queue     */
+
+	struct net_device_stats	stats;
+
+	/* Detailed SLIP statistics. */
+	int		mtu;		/* Our mtu (to spot changes!)   */
+	int		buffsize;	/* Max buffers sizes            */
+
+	unsigned long	flags;		/* Flag values/ mode etc	*/
+					/* long req'd: used by set_bit --RR */
+#define AXF_INUSE	0		/* Channel in use               */
+#define AXF_ESCAPE	1               /* ESC received                 */
+#define AXF_ERROR	2               /* Parity, etc. error           */
+#define AXF_KEEPTEST	3		/* Keepalive test flag		*/
+#define AXF_OUTWAIT	4		/* is outpacket was flag	*/
+
+	int		mode;
+        int		crcmode;	/* MW: for FlexNet, SMACK etc.  */
+#define CRC_MODE_NONE   0
+#define CRC_MODE_FLEX   1
+#define CRC_MODE_SMACK  2
+
+	atomic_t		refcnt;
+	struct semaphore	dead_sem;
+};
 
 /*---------------------------------------------------------------------------*/
 
-static const unsigned short Crc_flex_table[] = {
-  0x0f87, 0x1e0e, 0x2c95, 0x3d1c, 0x49a3, 0x582a, 0x6ab1, 0x7b38,
-  0x83cf, 0x9246, 0xa0dd, 0xb154, 0xc5eb, 0xd462, 0xe6f9, 0xf770,
-  0x1f06, 0x0e8f, 0x3c14, 0x2d9d, 0x5922, 0x48ab, 0x7a30, 0x6bb9,
-  0x934e, 0x82c7, 0xb05c, 0xa1d5, 0xd56a, 0xc4e3, 0xf678, 0xe7f1,
-  0x2e85, 0x3f0c, 0x0d97, 0x1c1e, 0x68a1, 0x7928, 0x4bb3, 0x5a3a,
-  0xa2cd, 0xb344, 0x81df, 0x9056, 0xe4e9, 0xf560, 0xc7fb, 0xd672,
-  0x3e04, 0x2f8d, 0x1d16, 0x0c9f, 0x7820, 0x69a9, 0x5b32, 0x4abb,
-  0xb24c, 0xa3c5, 0x915e, 0x80d7, 0xf468, 0xe5e1, 0xd77a, 0xc6f3,
-  0x4d83, 0x5c0a, 0x6e91, 0x7f18, 0x0ba7, 0x1a2e, 0x28b5, 0x393c,
-  0xc1cb, 0xd042, 0xe2d9, 0xf350, 0x87ef, 0x9666, 0xa4fd, 0xb574,
-  0x5d02, 0x4c8b, 0x7e10, 0x6f99, 0x1b26, 0x0aaf, 0x3834, 0x29bd,
-  0xd14a, 0xc0c3, 0xf258, 0xe3d1, 0x976e, 0x86e7, 0xb47c, 0xa5f5,
-  0x6c81, 0x7d08, 0x4f93, 0x5e1a, 0x2aa5, 0x3b2c, 0x09b7, 0x183e,
-  0xe0c9, 0xf140, 0xc3db, 0xd252, 0xa6ed, 0xb764, 0x85ff, 0x9476,
-  0x7c00, 0x6d89, 0x5f12, 0x4e9b, 0x3a24, 0x2bad, 0x1936, 0x08bf,
-  0xf048, 0xe1c1, 0xd35a, 0xc2d3, 0xb66c, 0xa7e5, 0x957e, 0x84f7,
-  0x8b8f, 0x9a06, 0xa89d, 0xb914, 0xcdab, 0xdc22, 0xeeb9, 0xff30,
-  0x07c7, 0x164e, 0x24d5, 0x355c, 0x41e3, 0x506a, 0x62f1, 0x7378,
-  0x9b0e, 0x8a87, 0xb81c, 0xa995, 0xdd2a, 0xcca3, 0xfe38, 0xefb1,
-  0x1746, 0x06cf, 0x3454, 0x25dd, 0x5162, 0x40eb, 0x7270, 0x63f9,
-  0xaa8d, 0xbb04, 0x899f, 0x9816, 0xeca9, 0xfd20, 0xcfbb, 0xde32,
-  0x26c5, 0x374c, 0x05d7, 0x145e, 0x60e1, 0x7168, 0x43f3, 0x527a,
-  0xba0c, 0xab85, 0x991e, 0x8897, 0xfc28, 0xeda1, 0xdf3a, 0xceb3,
-  0x3644, 0x27cd, 0x1556, 0x04df, 0x7060, 0x61e9, 0x5372, 0x42fb,
-  0xc98b, 0xd802, 0xea99, 0xfb10, 0x8faf, 0x9e26, 0xacbd, 0xbd34,
-  0x45c3, 0x544a, 0x66d1, 0x7758, 0x03e7, 0x126e, 0x20f5, 0x317c,
-  0xd90a, 0xc883, 0xfa18, 0xeb91, 0x9f2e, 0x8ea7, 0xbc3c, 0xadb5,
-  0x5542, 0x44cb, 0x7650, 0x67d9, 0x1366, 0x02ef, 0x3074, 0x21fd,
-  0xe889, 0xf900, 0xcb9b, 0xda12, 0xaead, 0xbf24, 0x8dbf, 0x9c36,
-  0x64c1, 0x7548, 0x47d3, 0x565a, 0x22e5, 0x336c, 0x01f7, 0x107e,
-  0xf808, 0xe981, 0xdb1a, 0xca93, 0xbe2c, 0xafa5, 0x9d3e, 0x8cb7,
-  0x7440, 0x65c9, 0x5752, 0x46db, 0x3264, 0x23ed, 0x1176, 0x00ff
+static const unsigned short crc_flex_table[] = {
+	0x0f87, 0x1e0e, 0x2c95, 0x3d1c, 0x49a3, 0x582a, 0x6ab1, 0x7b38,
+	0x83cf, 0x9246, 0xa0dd, 0xb154, 0xc5eb, 0xd462, 0xe6f9, 0xf770,
+	0x1f06, 0x0e8f, 0x3c14, 0x2d9d, 0x5922, 0x48ab, 0x7a30, 0x6bb9,
+	0x934e, 0x82c7, 0xb05c, 0xa1d5, 0xd56a, 0xc4e3, 0xf678, 0xe7f1,
+	0x2e85, 0x3f0c, 0x0d97, 0x1c1e, 0x68a1, 0x7928, 0x4bb3, 0x5a3a,
+	0xa2cd, 0xb344, 0x81df, 0x9056, 0xe4e9, 0xf560, 0xc7fb, 0xd672,
+	0x3e04, 0x2f8d, 0x1d16, 0x0c9f, 0x7820, 0x69a9, 0x5b32, 0x4abb,
+	0xb24c, 0xa3c5, 0x915e, 0x80d7, 0xf468, 0xe5e1, 0xd77a, 0xc6f3,
+	0x4d83, 0x5c0a, 0x6e91, 0x7f18, 0x0ba7, 0x1a2e, 0x28b5, 0x393c,
+	0xc1cb, 0xd042, 0xe2d9, 0xf350, 0x87ef, 0x9666, 0xa4fd, 0xb574,
+	0x5d02, 0x4c8b, 0x7e10, 0x6f99, 0x1b26, 0x0aaf, 0x3834, 0x29bd,
+	0xd14a, 0xc0c3, 0xf258, 0xe3d1, 0x976e, 0x86e7, 0xb47c, 0xa5f5,
+	0x6c81, 0x7d08, 0x4f93, 0x5e1a, 0x2aa5, 0x3b2c, 0x09b7, 0x183e,
+	0xe0c9, 0xf140, 0xc3db, 0xd252, 0xa6ed, 0xb764, 0x85ff, 0x9476,
+	0x7c00, 0x6d89, 0x5f12, 0x4e9b, 0x3a24, 0x2bad, 0x1936, 0x08bf,
+	0xf048, 0xe1c1, 0xd35a, 0xc2d3, 0xb66c, 0xa7e5, 0x957e, 0x84f7,
+	0x8b8f, 0x9a06, 0xa89d, 0xb914, 0xcdab, 0xdc22, 0xeeb9, 0xff30,
+	0x07c7, 0x164e, 0x24d5, 0x355c, 0x41e3, 0x506a, 0x62f1, 0x7378,
+	0x9b0e, 0x8a87, 0xb81c, 0xa995, 0xdd2a, 0xcca3, 0xfe38, 0xefb1,
+	0x1746, 0x06cf, 0x3454, 0x25dd, 0x5162, 0x40eb, 0x7270, 0x63f9,
+	0xaa8d, 0xbb04, 0x899f, 0x9816, 0xeca9, 0xfd20, 0xcfbb, 0xde32,
+	0x26c5, 0x374c, 0x05d7, 0x145e, 0x60e1, 0x7168, 0x43f3, 0x527a,
+	0xba0c, 0xab85, 0x991e, 0x8897, 0xfc28, 0xeda1, 0xdf3a, 0xceb3,
+	0x3644, 0x27cd, 0x1556, 0x04df, 0x7060, 0x61e9, 0x5372, 0x42fb,
+	0xc98b, 0xd802, 0xea99, 0xfb10, 0x8faf, 0x9e26, 0xacbd, 0xbd34,
+	0x45c3, 0x544a, 0x66d1, 0x7758, 0x03e7, 0x126e, 0x20f5, 0x317c,
+	0xd90a, 0xc883, 0xfa18, 0xeb91, 0x9f2e, 0x8ea7, 0xbc3c, 0xadb5,
+	0x5542, 0x44cb, 0x7650, 0x67d9, 0x1366, 0x02ef, 0x3074, 0x21fd,
+	0xe889, 0xf900, 0xcb9b, 0xda12, 0xaead, 0xbf24, 0x8dbf, 0x9c36,
+	0x64c1, 0x7548, 0x47d3, 0x565a, 0x22e5, 0x336c, 0x01f7, 0x107e,
+	0xf808, 0xe981, 0xdb1a, 0xca93, 0xbe2c, 0xafa5, 0x9d3e, 0x8cb7,
+	0x7440, 0x65c9, 0x5752, 0x46db, 0x3264, 0x23ed, 0x1176, 0x00ff
 };
 
-/*---------------------------------------------------------------------------*/
-
 static unsigned short calc_crc_flex(unsigned char *cp, int size)
 {
-    unsigned short crc = 0xffff;
-    
-    while (size--)
-	crc = (crc << 8) ^ Crc_flex_table[((crc >> 8) ^ *cp++) & 0xff];
+	unsigned short crc = 0xffff;
 
-    return crc;
-}
+	while (size--)
+		crc = (crc << 8) ^ crc_flex_table[((crc >> 8) ^ *cp++) & 0xff];
 
-/*---------------------------------------------------------------------------*/
+	return crc;
+}
 
 static int check_crc_flex(unsigned char *cp, int size)
 {
-  unsigned short crc = 0xffff;
+	unsigned short crc = 0xffff;
 
-  if (size < 3)
-      return -1;
+	if (size < 3)
+		return -1;
 
-  while (size--)
-      crc = (crc << 8) ^ Crc_flex_table[((crc >> 8) ^ *cp++) & 0xff];
+	while (size--)
+		crc = (crc << 8) ^ crc_flex_table[((crc >> 8) ^ *cp++) & 0xff];
 
-  if ((crc & 0xffff) != 0x7070) 
-      return -1;
+	if ((crc & 0xffff) != 0x7070)
+		return -1;
 
-  return 0;
+	return 0;
 }
 
-/*---------------------------------------------------------------------------*/
+/*
+ * Standard encapsulation
+ */
 
-/* Find a free channel, and link in this `tty' line. */
-static inline struct ax_disp *ax_alloc(void)
+static int kiss_esc(unsigned char *s, unsigned char *d, int len)
 {
-	ax25_ctrl_t *axp=NULL;
-	int i;
+	unsigned char *ptr = d;
+	unsigned char c;
 
-	for (i = 0; i < ax25_maxdev; i++) {
-		axp = ax25_ctrls[i];
+	/*
+	 * Send an initial END character to flush out any data that may have
+	 * accumulated in the receiver due to line noise.
+	 */
 
-		/* Not allocated ? */
-		if (axp == NULL)
-			break;
+	*ptr++ = END;
 
-		/* Not in use ? */
-		if (!test_and_set_bit(AXF_INUSE, &axp->ctrl.flags))
+	while (len-- > 0) {
+		switch (c = *s++) {
+		case END:
+			*ptr++ = ESC;
+			*ptr++ = ESC_END;
 			break;
+		case ESC:
+			*ptr++ = ESC;
+			*ptr++ = ESC_ESC;
+			break;
+		default:
+			*ptr++ = c;
+			break;
+		}
 	}
 
-	/* Sorry, too many, all slots in use */
-	if (i >= ax25_maxdev)
-		return NULL;
+	*ptr++ = END;
+
+	return ptr - d;
+}
+
+/*
+ * MW:
+ * OK its ugly, but tell me a better solution without copying the
+ * packet to a temporary buffer :-)
+ */
+static int kiss_esc_crc(unsigned char *s, unsigned char *d, unsigned short crc,
+	int len)
+{
+	unsigned char *ptr = d;
+	unsigned char c=0;
+
+	*ptr++ = END;
+	while (len > 0) {
+		if (len > 2)
+			c = *s++;
+		else if (len > 1)
+			c = crc >> 8;
+		else if (len > 0)
+			c = crc & 0xff;
+
+		len--;
 
-	/* If no channels are available, allocate one */
-	if (axp == NULL && (ax25_ctrls[i] = kmalloc(sizeof(ax25_ctrl_t), GFP_KERNEL)) != NULL) {
-		axp = ax25_ctrls[i];
+		switch (c) {
+		case END:
+			*ptr++ = ESC;
+			*ptr++ = ESC_END;
+			break;
+		case ESC:
+			*ptr++ = ESC;
+			*ptr++ = ESC_ESC;
+			break;
+		default:
+			*ptr++ = c;
+			break;
+		}
 	}
-	memset(axp, 0, sizeof(ax25_ctrl_t));
-
-	/* Initialize channel control data */
-	set_bit(AXF_INUSE, &axp->ctrl.flags);
-	sprintf(axp->dev.name, "ax%d", i++);
-	axp->ctrl.tty      = NULL;
-	axp->dev.base_addr = i;
-	axp->dev.priv      = (void *)&axp->ctrl;
-	axp->dev.next      = NULL;
-	axp->dev.init      = ax25_init;
-
-	if (axp != NULL) {
-		/*
-		 * register device so that it can be ifconfig'ed
-		 * ax25_init() will be called as a side-effect
-		 * SIDE-EFFECT WARNING: ax25_init() CLEARS axp->ctrl !
-		 */
-		if (register_netdev(&axp->dev) == 0) {
-			/* (Re-)Set the INUSE bit.   Very Important! */
-			set_bit(AXF_INUSE, &axp->ctrl.flags);
-			axp->ctrl.dev = &axp->dev;
-			axp->dev.priv = (void *) &axp->ctrl;
-
-			return &axp->ctrl;
-		} else {
-			clear_bit(AXF_INUSE,&axp->ctrl.flags);
-			printk(KERN_ERR "mkiss: ax_alloc() - register_netdev() failure.\n");
+	*ptr++ = END;
+
+	return ptr - d;
+}
+
+/* Send one completely decapsulated AX.25 packet to the AX.25 layer. */
+static void ax_bump(struct mkiss *ax)
+{
+	struct sk_buff *skb;
+	int count;
+
+	spin_lock_bh(&ax->buflock);
+	if (ax->rbuff[0] > 0x0f) {
+		if (ax->rbuff[0] & 0x20) {
+		        ax->crcmode = CRC_MODE_FLEX;
+			if (check_crc_flex(ax->rbuff, ax->rcount) < 0) {
+			        ax->stats.rx_errors++;
+				return;
+			}
+			ax->rcount -= 2;
+                        /* dl9sau bugfix: the trailling two bytes flexnet crc
+                         * will not be passed to the kernel. thus we have
+                         * to correct the kissparm signature, because it
+                         * indicates a crc but there's none
+			 */
+                        *ax->rbuff &= ~0x20;
 		}
+ 	}
+	spin_unlock_bh(&ax->buflock);
+
+	count = ax->rcount;
+
+	if ((skb = dev_alloc_skb(count)) == NULL) {
+		printk(KERN_ERR "mkiss: %s: memory squeeze, dropping packet.\n",
+		       ax->dev->name);
+		ax->stats.rx_dropped++;
+		return;
 	}
 
-	return NULL;
+	spin_lock_bh(&ax->buflock);
+	memcpy(skb_put(skb,count), ax->rbuff, count);
+	spin_unlock_bh(&ax->buflock);
+	skb->protocol = ax25_type_trans(skb, ax->dev);
+	netif_rx(skb);
+	ax->dev->last_rx = jiffies;
+	ax->stats.rx_packets++;
+	ax->stats.rx_bytes += count;
 }
 
-/* Free an AX25 channel. */
-static inline void ax_free(struct ax_disp *ax)
+static void kiss_unesc(struct mkiss *ax, unsigned char s)
 {
-	/* Free all AX25 frame buffers. */
-	if (ax->rbuff)
-		kfree(ax->rbuff);
-	ax->rbuff = NULL;
-	if (ax->xbuff)
-		kfree(ax->xbuff);
-	ax->xbuff = NULL;
-	if (!test_and_clear_bit(AXF_INUSE, &ax->flags))
-		printk(KERN_ERR "mkiss: %s: ax_free for already free unit.\n", ax->dev->name);
+	switch (s) {
+	case END:
+		/* drop keeptest bit = VSV */
+		if (test_bit(AXF_KEEPTEST, &ax->flags))
+			clear_bit(AXF_KEEPTEST, &ax->flags);
+
+		if (!test_and_clear_bit(AXF_ERROR, &ax->flags) && (ax->rcount > 2))
+			ax_bump(ax);
+
+		clear_bit(AXF_ESCAPE, &ax->flags);
+		ax->rcount = 0;
+		return;
+
+	case ESC:
+		set_bit(AXF_ESCAPE, &ax->flags);
+		return;
+	case ESC_ESC:
+		if (test_and_clear_bit(AXF_ESCAPE, &ax->flags))
+			s = ESC;
+		break;
+	case ESC_END:
+		if (test_and_clear_bit(AXF_ESCAPE, &ax->flags))
+			s = END;
+		break;
+	}
+
+	spin_lock_bh(&ax->buflock);
+	if (!test_bit(AXF_ERROR, &ax->flags)) {
+		if (ax->rcount < ax->buffsize) {
+			ax->rbuff[ax->rcount++] = s;
+			spin_unlock_bh(&ax->buflock);
+			return;
+		}
+
+		ax->stats.rx_over_errors++;
+		set_bit(AXF_ERROR, &ax->flags);
+	}
+	spin_unlock_bh(&ax->buflock);
+}
+
+static int ax_set_mac_address(struct net_device *dev, void *addr)
+{
+	struct sockaddr_ax25 *sa = addr;
+
+	spin_lock_irq(&dev->xmit_lock);
+	memcpy(dev->dev_addr, &sa->sax25_call, AX25_ADDR_LEN);
+	spin_unlock_irq(&dev->xmit_lock);
+
+	return 0;
 }
 
-static void ax_changedmtu(struct ax_disp *ax)
+/*---------------------------------------------------------------------------*/
+
+static void ax_changedmtu(struct mkiss *ax)
 {
 	struct net_device *dev = ax->dev;
 	unsigned char *xbuff, *rbuff, *oxbuff, *orbuff;
@@ -237,7 +348,8 @@ static void ax_changedmtu(struct ax_disp *ax)
 	rbuff = kmalloc(len + 4, GFP_ATOMIC);
 
 	if (xbuff == NULL || rbuff == NULL)  {
-		printk(KERN_ERR "mkiss: %s: unable to grow ax25 buffers, MTU change cancelled.\n",
+		printk(KERN_ERR "mkiss: %s: unable to grow ax25 buffers, "
+		       "MTU change cancelled.\n",
 		       ax->dev->name);
 		dev->mtu = ax->mtu;
 		if (xbuff != NULL)
@@ -259,7 +371,7 @@ static void ax_changedmtu(struct ax_disp *ax)
 			memcpy(ax->xbuff, ax->xhead, ax->xleft);
 		} else  {
 			ax->xleft = 0;
-			ax->tx_dropped++;
+			ax->stats.tx_dropped++;
 		}
 	}
 
@@ -270,7 +382,7 @@ static void ax_changedmtu(struct ax_disp *ax)
 			memcpy(ax->rbuff, orbuff, ax->rcount);
 		} else  {
 			ax->rcount = 0;
-			ax->rx_over_errors++;
+			ax->stats.rx_over_errors++;
 			set_bit(AXF_ERROR, &ax->flags);
 		}
 	}
@@ -280,72 +392,14 @@ static void ax_changedmtu(struct ax_disp *ax)
 
 	spin_unlock_bh(&ax->buflock);
 
-	if (oxbuff != NULL)
-		kfree(oxbuff);
-	if (orbuff != NULL)
-		kfree(orbuff);
-}
-
-
-/* Set the "sending" flag.  This must be atomic. */
-static inline void ax_lock(struct ax_disp *ax)
-{
-	netif_stop_queue(ax->dev);
-}
-
-
-/* Clear the "sending" flag.  This must be atomic. */
-static inline void ax_unlock(struct ax_disp *ax)
-{
-	netif_start_queue(ax->dev);
-}
-
-/* Send one completely decapsulated AX.25 packet to the AX.25 layer. */
-static void ax_bump(struct ax_disp *ax)
-{
-	struct sk_buff *skb;
-	int count;
-
-	spin_lock_bh(&ax->buflock);
-	if (ax->rbuff[0] > 0x0f) {
-		if (ax->rbuff[0] & 0x20) {
-		        ax->crcmode = CRC_MODE_FLEX;
-			if (check_crc_flex(ax->rbuff, ax->rcount) < 0) {
-			        ax->rx_errors++;
-				return;
-			}
-			ax->rcount -= 2;
-                        /* dl9sau bugfix: the trailling two bytes flexnet crc
-                         * will not be passed to the kernel. thus we have
-                         * to correct the kissparm signature, because it
-                         * indicates a crc but there's none
-			 */
-                        *ax->rbuff &= ~0x20;
-		}
- 	}
-	spin_unlock_bh(&ax->buflock);
-
-	count = ax->rcount;
-
-	if ((skb = dev_alloc_skb(count)) == NULL) {
-		printk(KERN_ERR "mkiss: %s: memory squeeze, dropping packet.\n", ax->dev->name);
-		ax->rx_dropped++;
-		return;
-	}
-
-	spin_lock_bh(&ax->buflock);
-	memcpy(skb_put(skb,count), ax->rbuff, count);
-	spin_unlock_bh(&ax->buflock);
-	skb->protocol = ax25_type_trans(skb, ax->dev);
-	netif_rx(skb);
-	ax->dev->last_rx = jiffies;
-	ax->rx_packets++;
-	ax->rx_bytes+=count;
+	kfree(oxbuff);
+	kfree(orbuff);
 }
 
 /* Encapsulate one AX.25 packet and stuff into a TTY queue. */
-static void ax_encaps(struct ax_disp *ax, unsigned char *icp, int len)
+static void ax_encaps(struct net_device *dev, unsigned char *icp, int len)
 {
+	struct mkiss *ax = netdev_priv(dev);
 	unsigned char *p;
 	int actual, count;
 
@@ -355,8 +409,8 @@ static void ax_encaps(struct ax_disp *ax, unsigned char *icp, int len)
 	if (len > ax->mtu) {		/* Sigh, shouldn't occur BUT ... */
 		len = ax->mtu;
 		printk(KERN_ERR "mkiss: %s: truncating oversized transmit packet!\n", ax->dev->name);
-		ax->tx_dropped++;
-		ax_unlock(ax);
+		ax->stats.tx_dropped++;
+		netif_start_queue(dev);
 		return;
 	}
 
@@ -377,10 +431,11 @@ static void ax_encaps(struct ax_disp *ax, unsigned char *icp, int len)
 		 break;
 	}
 	
-	ax->tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
+	set_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags);
 	actual = ax->tty->driver->write(ax->tty, ax->xbuff, count);
-	ax->tx_packets++;
-	ax->tx_bytes+=actual;
+	ax->stats.tx_packets++;
+	ax->stats.tx_bytes += actual;
+
 	ax->dev->trans_start = jiffies;
 	ax->xleft = count - actual;
 	ax->xhead = ax->xbuff + actual;
@@ -388,37 +443,10 @@ static void ax_encaps(struct ax_disp *ax, unsigned char *icp, int len)
 	spin_unlock_bh(&ax->buflock);
 }
 
-/*
- * Called by the driver when there's room for more data.  If we have
- * more packets to send, we send them here.
- */
-static void ax25_write_wakeup(struct tty_struct *tty)
-{
-	int actual;
-	struct ax_disp *ax = (struct ax_disp *) tty->disc_data;
-
-	/* First make sure we're connected. */
-	if (ax == NULL || ax->magic != AX25_MAGIC || !netif_running(ax->dev))
-		return;
-	if (ax->xleft <= 0)  {
-		/* Now serial buffer is almost free & we can start
-		 * transmission of another packet
-		 */
-		tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
-
-		netif_wake_queue(ax->dev);
-		return;
-	}
-
-	actual = tty->driver->write(tty, ax->xhead, ax->xleft);
-	ax->xleft -= actual;
-	ax->xhead += actual;
-}
-
 /* Encapsulate an AX.25 packet and kick it into a TTY queue. */
 static int ax_xmit(struct sk_buff *skb, struct net_device *dev)
 {
-	struct ax_disp *ax = netdev_priv(dev);
+	struct mkiss *ax = netdev_priv(dev);
 
 	if (!netif_running(dev))  {
 		printk(KERN_ERR "mkiss: %s: xmit call when iface is down\n", dev->name);
@@ -440,20 +468,30 @@ static int ax_xmit(struct sk_buff *skb, struct net_device *dev)
 		       "bad line quality" : "driver error");
 
 		ax->xleft = 0;
-		ax->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
-		ax_unlock(ax);
+		clear_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags);
+		netif_start_queue(dev);
 	}
 
 	/* We were not busy, so we are now... :-) */
 	if (skb != NULL) {
-		ax_lock(ax);
-		ax_encaps(ax, skb->data, skb->len);
+		netif_stop_queue(dev);
+		ax_encaps(dev, skb->data, skb->len);
 		kfree_skb(skb);
 	}
 
 	return 0;
 }
 
+static int ax_open_dev(struct net_device *dev)
+{
+	struct mkiss *ax = netdev_priv(dev);
+
+	if (ax->tty == NULL)
+		return -ENODEV;
+
+	return 0;
+}
+
 #if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
 
 /* Return the frame type ID */
@@ -482,7 +520,7 @@ static int ax_rebuild_header(struct sk_buff *skb)
 /* Open the low-level part of the AX25 channel. Easy! */
 static int ax_open(struct net_device *dev)
 {
-	struct ax_disp *ax = netdev_priv(dev);
+	struct mkiss *ax = netdev_priv(dev);
 	unsigned long len;
 
 	if (ax->tty == NULL)
@@ -519,7 +557,6 @@ static int ax_open(struct net_device *dev)
 
 	spin_lock_init(&ax->buflock);
 
-	netif_start_queue(dev);
 	return 0;
 
 noxbuff:
@@ -533,68 +570,100 @@ norbuff:
 /* Close the low-level part of the AX25 channel. Easy! */
 static int ax_close(struct net_device *dev)
 {
-	struct ax_disp *ax = netdev_priv(dev);
+	struct mkiss *ax = netdev_priv(dev);
 
-	if (ax->tty == NULL)
-		return -EBUSY;
-
-	ax->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
+	if (ax->tty)
+		clear_bit(TTY_DO_WRITE_WAKEUP, &ax->tty->flags);
 
 	netif_stop_queue(dev);
 
 	return 0;
 }
 
-static int ax25_receive_room(struct tty_struct *tty)
+static struct net_device_stats *ax_get_stats(struct net_device *dev)
 {
-	return 65536;  /* We can handle an infinite amount of data. :-) */
+	struct mkiss *ax = netdev_priv(dev);
+
+	return &ax->stats;
+}
+
+static void ax_setup(struct net_device *dev)
+{
+	static char ax25_bcast[AX25_ADDR_LEN] =
+		{'Q'<<1,'S'<<1,'T'<<1,' '<<1,' '<<1,' '<<1,'0'<<1};
+	static char ax25_test[AX25_ADDR_LEN] =
+		{'L'<<1,'I'<<1,'N'<<1,'U'<<1,'X'<<1,' '<<1,'1'<<1};
+
+	/* Finish setting up the DEVICE info. */
+	dev->mtu             = AX_MTU;
+	dev->hard_start_xmit = ax_xmit;
+	dev->open            = ax_open_dev;
+	dev->stop            = ax_close;
+	dev->get_stats	     = ax_get_stats;
+	dev->set_mac_address = ax_set_mac_address;
+	dev->hard_header_len = 0;
+	dev->addr_len        = 0;
+	dev->type            = ARPHRD_AX25;
+	dev->tx_queue_len    = 10;
+	dev->hard_header     = ax_header;
+	dev->rebuild_header  = ax_rebuild_header;
+
+	memcpy(dev->broadcast, ax25_bcast, AX25_ADDR_LEN);
+	memcpy(dev->dev_addr,  ax25_test,  AX25_ADDR_LEN);
+
+	dev->flags      = IFF_BROADCAST | IFF_MULTICAST;
 }
 
 /*
- * Handle the 'receiver data ready' interrupt.
- * This function is called by the 'tty_io' module in the kernel when
- * a block of data has been received, which can now be decapsulated
- * and sent on to the AX.25 layer for further processing.
+ * We have a potential race on dereferencing tty->disc_data, because the tty
+ * layer provides no locking at all - thus one cpu could be running
+ * sixpack_receive_buf while another calls sixpack_close, which zeroes
+ * tty->disc_data and frees the memory that sixpack_receive_buf is using.  The
+ * best way to fix this is to use a rwlock in the tty struct, but for now we
+ * use a single global rwlock for all ttys in ppp line discipline.
  */
-static void ax25_receive_buf(struct tty_struct *tty, const unsigned char *cp, char *fp, int count)
+static rwlock_t disc_data_lock = RW_LOCK_UNLOCKED;
+
+static struct mkiss *mkiss_get(struct tty_struct *tty)
 {
-	struct ax_disp *ax = (struct ax_disp *) tty->disc_data;
+	struct mkiss *ax;
 
-	if (ax == NULL || ax->magic != AX25_MAGIC || !netif_running(ax->dev))
-		return;
+	read_lock(&disc_data_lock);
+	ax = tty->disc_data;
+	if (ax)
+		atomic_inc(&ax->refcnt);
+	read_unlock(&disc_data_lock);
 
-	/*
-	 * Argh! mtu change time! - costs us the packet part received
-	 * at the change
-	 */
-	if (ax->mtu != ax->dev->mtu + 73)
-		ax_changedmtu(ax);
-
-	/* Read the characters out of the buffer */
-	while (count--) {
-		if (fp != NULL && *fp++) {
-			if (!test_and_set_bit(AXF_ERROR, &ax->flags))
-				ax->rx_errors++;
-			cp++;
-			continue;
-		}
+	return ax;
+}
 
-		kiss_unesc(ax, *cp++);
-	}
+static void mkiss_put(struct mkiss *ax)
+{
+	if (atomic_dec_and_test(&ax->refcnt))
+		up(&ax->dead_sem);
 }
 
-static int ax25_open(struct tty_struct *tty)
+static int mkiss_open(struct tty_struct *tty)
 {
-	struct ax_disp *ax = (struct ax_disp *) tty->disc_data;
+	struct net_device *dev;
+	struct mkiss *ax;
 	int err;
 
-	/* First make sure we're not already connected. */
-	if (ax && ax->magic == AX25_MAGIC)
-		return -EEXIST;
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
 
-	/* OK.  Find a free AX25 channel to use. */
-	if ((ax = ax_alloc()) == NULL)
-		return -ENFILE;
+	dev = alloc_netdev(sizeof(struct mkiss), "ax%d", ax_setup);
+	if (!dev) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	ax = netdev_priv(dev);
+	ax->dev = dev;
+
+	spin_lock_init(&ax->buflock);
+	atomic_set(&ax->refcnt, 1);
+	init_MUTEX_LOCKED(&ax->dead_sem);
 
 	ax->tty = tty;
 	tty->disc_data = ax;
@@ -603,283 +672,212 @@ static int ax25_open(struct tty_struct *tty)
 		tty->driver->flush_buffer(tty);
 
 	/* Restore default settings */
-	ax->dev->type = ARPHRD_AX25;
+	dev->type = ARPHRD_AX25;
 
 	/* Perform the low-level AX25 initialization. */
-	if ((err = ax_open(ax->dev)))
-		return err;
+	if ((err = ax_open(ax->dev))) {
+		goto out_free_netdev;
+	}
 
-	/* Done.  We have linked the TTY line to a channel. */
-	return ax->dev->base_addr;
-}
+	if (register_netdev(dev))
+		goto out_free_buffers;
 
-static void ax25_close(struct tty_struct *tty)
-{
-	struct ax_disp *ax = (struct ax_disp *) tty->disc_data;
+	netif_start_queue(dev);
 
-	/* First make sure we're connected. */
-	if (ax == NULL || ax->magic != AX25_MAGIC)
-		return;
+	/* Done.  We have linked the TTY line to a channel. */
+	return 0;
 
-	unregister_netdev(ax->dev);
+out_free_buffers:
+	kfree(ax->rbuff);
+	kfree(ax->xbuff);
 
-	tty->disc_data = NULL;
-	ax->tty        = NULL;
+out_free_netdev:
+	free_netdev(dev);
 
-	ax_free(ax);
+out:
+	return err;
 }
 
-
-static struct net_device_stats *ax_get_stats(struct net_device *dev)
+static void mkiss_close(struct tty_struct *tty)
 {
-	static struct net_device_stats stats;
-	struct ax_disp *ax = netdev_priv(dev);
-
-	memset(&stats, 0, sizeof(struct net_device_stats));
-
-	stats.rx_packets     = ax->rx_packets;
-	stats.tx_packets     = ax->tx_packets;
-	stats.rx_bytes	     = ax->rx_bytes;
-	stats.tx_bytes       = ax->tx_bytes;
-	stats.rx_dropped     = ax->rx_dropped;
-	stats.tx_dropped     = ax->tx_dropped;
-	stats.tx_errors      = ax->tx_errors;
-	stats.rx_errors      = ax->rx_errors;
-	stats.rx_over_errors = ax->rx_over_errors;
-
-	return &stats;
-}
+	struct mkiss *ax;
 
+	write_lock(&disc_data_lock);
+	ax = tty->disc_data;
+	tty->disc_data = NULL;
+	write_unlock(&disc_data_lock);
 
-/************************************************************************
- *			   STANDARD ENCAPSULATION	        	 *
- ************************************************************************/
-
-static int kiss_esc(unsigned char *s, unsigned char *d, int len)
-{
-	unsigned char *ptr = d;
-	unsigned char c;
+	if (ax == 0)
+		return;
 
 	/*
-	 * Send an initial END character to flush out any
-	 * data that may have accumulated in the receiver
-	 * due to line noise.
+	 * We have now ensured that nobody can start using ap from now on, but
+	 * we have to wait for all existing users to finish.
 	 */
+	if (!atomic_dec_and_test(&ax->refcnt))
+		down(&ax->dead_sem);
 
-	*ptr++ = END;
-
-	while (len-- > 0) {
-		switch (c = *s++) {
-			case END:
-				*ptr++ = ESC;
-				*ptr++ = ESC_END;
-				break;
-			case ESC:
-				*ptr++ = ESC;
-				*ptr++ = ESC_ESC;
-				break;
-			default:
-				*ptr++ = c;
-				break;
-		}
-	}
+	unregister_netdev(ax->dev);
 
-	*ptr++ = END;
+	/* Free all AX25 frame buffers. */
+	kfree(ax->rbuff);
+	kfree(ax->xbuff);
 
-	return ptr - d;
+	ax->tty = NULL;
 }
 
-/*
- * MW:
- * OK its ugly, but tell me a better solution without copying the
- * packet to a temporary buffer :-)
- */
-static int kiss_esc_crc(unsigned char *s, unsigned char *d, unsigned short crc, int len)
+/* Perform I/O control on an active ax25 channel. */
+static int mkiss_ioctl(struct tty_struct *tty, struct file *file,
+	unsigned int cmd, unsigned long arg)
 {
-	unsigned char *ptr = d;
-	unsigned char c=0;
-
-	*ptr++ = END;
-	while (len > 0) {
-		if (len > 2) 
-			c = *s++;
-		else if (len > 1)
-			c = crc >> 8;
-		else if (len > 0)
-			c = crc & 0xff;
+	struct mkiss *ax = mkiss_get(tty);
+	struct net_device *dev = ax->dev;
+	unsigned int tmp, err;
 
-		len--;
+	/* First make sure we're connected. */
+	if (ax == NULL)
+		return -ENXIO;
 
-		switch (c) {
-                        case END:
-                                *ptr++ = ESC;
-                                *ptr++ = ESC_END;
-                                break;
-                        case ESC:
-                                *ptr++ = ESC;
-                                *ptr++ = ESC_ESC;
-                                break;
-                        default:
-                                *ptr++ = c;
-                                break;
+	switch (cmd) {
+ 	case SIOCGIFNAME:
+		err = copy_to_user((void __user *) arg, ax->dev->name,
+		                   strlen(ax->dev->name) + 1) ? -EFAULT : 0;
+		break;
+
+	case SIOCGIFENCAP:
+		err = put_user(4, (int __user *) arg);
+		break;
+
+	case SIOCSIFENCAP:
+		if (get_user(tmp, (int __user *) arg)) {
+			err = -EFAULT;
+			break;
 		}
-	}
-	*ptr++ = END;
-	return ptr - d;		
-}
 
-static void kiss_unesc(struct ax_disp *ax, unsigned char s)
-{
-	switch (s) {
-		case END:
-			/* drop keeptest bit = VSV */
-			if (test_bit(AXF_KEEPTEST, &ax->flags))
-				clear_bit(AXF_KEEPTEST, &ax->flags);
+		ax->mode = tmp;
+		dev->addr_len        = AX25_ADDR_LEN;
+		dev->hard_header_len = AX25_KISS_HEADER_LEN +
+		                       AX25_MAX_HEADER_LEN + 3;
+		dev->type            = ARPHRD_AX25;
 
-			if (!test_and_clear_bit(AXF_ERROR, &ax->flags) && (ax->rcount > 2))
-				ax_bump(ax);
+		err = 0;
+		break;
 
-			clear_bit(AXF_ESCAPE, &ax->flags);
-			ax->rcount = 0;
-			return;
+	case SIOCSIFHWADDR: {
+		char addr[AX25_ADDR_LEN];
+printk(KERN_INFO "In SIOCSIFHWADDR");
 
-		case ESC:
-			set_bit(AXF_ESCAPE, &ax->flags);
-			return;
-		case ESC_ESC:
-			if (test_and_clear_bit(AXF_ESCAPE, &ax->flags))
-				s = ESC;
+		if (copy_from_user(&addr,
+		                   (void __user *) arg, AX25_ADDR_LEN)) {
+			err = -EFAULT;
 			break;
-		case ESC_END:
-			if (test_and_clear_bit(AXF_ESCAPE, &ax->flags))
-				s = END;
-			break;
-	}
-
-	spin_lock_bh(&ax->buflock);
-	if (!test_bit(AXF_ERROR, &ax->flags)) {
-		if (ax->rcount < ax->buffsize) {
-			ax->rbuff[ax->rcount++] = s;
-			spin_unlock_bh(&ax->buflock);
-			return;
 		}
 
-		ax->rx_over_errors++;
-		set_bit(AXF_ERROR, &ax->flags);
+		spin_lock_irq(&dev->xmit_lock);
+		memcpy(dev->dev_addr, addr, AX25_ADDR_LEN);
+		spin_unlock_irq(&dev->xmit_lock);
+
+		err = 0;
+		break;
+	}
+	default:
+		err = -ENOIOCTLCMD;
 	}
-	spin_unlock_bh(&ax->buflock);
-}
 
+	mkiss_put(ax);
 
-static int ax_set_mac_address(struct net_device *dev, void __user *addr)
-{
-	if (copy_from_user(dev->dev_addr, addr, AX25_ADDR_LEN))
-		return -EFAULT;
-	return 0;
+	return err;
 }
 
-static int ax_set_dev_mac_address(struct net_device *dev, void *addr)
+/*
+ * Handle the 'receiver data ready' interrupt.
+ * This function is called by the 'tty_io' module in the kernel when
+ * a block of data has been received, which can now be decapsulated
+ * and sent on to the AX.25 layer for further processing.
+ */
+static void mkiss_receive_buf(struct tty_struct *tty, const unsigned char *cp,
+	char *fp, int count)
 {
-	struct sockaddr *sa = addr;
-
-	memcpy(dev->dev_addr, sa->sa_data, AX25_ADDR_LEN);
+	struct mkiss *ax = mkiss_get(tty);
 
-	return 0;
-}
-
-
-/* Perform I/O control on an active ax25 channel. */
-static int ax25_disp_ioctl(struct tty_struct *tty, void *file, int cmd, void __user *arg)
-{
-	struct ax_disp *ax = (struct ax_disp *) tty->disc_data;
-	unsigned int tmp;
+	if (!ax)
+		return;
 
-	/* First make sure we're connected. */
-	if (ax == NULL || ax->magic != AX25_MAGIC)
-		return -EINVAL;
+	/*
+	 * Argh! mtu change time! - costs us the packet part received
+	 * at the change
+	 */
+	if (ax->mtu != ax->dev->mtu + 73)
+		ax_changedmtu(ax);
 
-	switch (cmd) {
-	 	case SIOCGIFNAME:
-			if (copy_to_user(arg, ax->dev->name, strlen(ax->dev->name) + 1))
-				return -EFAULT;
-			return 0;
-
-		case SIOCGIFENCAP:
-			return put_user(4, (int __user *)arg);
-
-		case SIOCSIFENCAP:
-			if (get_user(tmp, (int __user *)arg))
-				return -EFAULT;
-			ax->mode = tmp;
-			ax->dev->addr_len        = AX25_ADDR_LEN;	  /* sizeof an AX.25 addr */
-			ax->dev->hard_header_len = AX25_KISS_HEADER_LEN + AX25_MAX_HEADER_LEN + 3;
-			ax->dev->type            = ARPHRD_AX25;
-			return 0;
-
-		 case SIOCSIFHWADDR:
-			return ax_set_mac_address(ax->dev, arg);
+	/* Read the characters out of the buffer */
+	while (count--) {
+		if (fp != NULL && *fp++) {
+			if (!test_and_set_bit(AXF_ERROR, &ax->flags))
+				ax->stats.rx_errors++;
+			cp++;
+			continue;
+		}
 
-		default:
-			return -ENOIOCTLCMD;
+		kiss_unesc(ax, *cp++);
 	}
+
+	mkiss_put(ax);
+	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
+	    && tty->driver->unthrottle)
+		tty->driver->unthrottle(tty);
 }
 
-static int ax_open_dev(struct net_device *dev)
+static int mkiss_receive_room(struct tty_struct *tty)
 {
-	struct ax_disp *ax = netdev_priv(dev);
-
-	if (ax->tty == NULL)
-		return -ENODEV;
-
-	return 0;
+	return 65536;  /* We can handle an infinite amount of data. :-) */
 }
 
-
-/* Initialize the driver.  Called by network startup. */
-static int ax25_init(struct net_device *dev)
+/*
+ * Called by the driver when there's room for more data.  If we have
+ * more packets to send, we send them here.
+ */
+static void mkiss_write_wakeup(struct tty_struct *tty)
 {
-	struct ax_disp *ax = netdev_priv(dev);
-
-	static char ax25_bcast[AX25_ADDR_LEN] =
-		{'Q'<<1,'S'<<1,'T'<<1,' '<<1,' '<<1,' '<<1,'0'<<1};
-	static char ax25_test[AX25_ADDR_LEN] =
-		{'L'<<1,'I'<<1,'N'<<1,'U'<<1,'X'<<1,' '<<1,'1'<<1};
-
-	if (ax == NULL)		/* Allocation failed ?? */
-		return -ENODEV;
+	struct mkiss *ax = mkiss_get(tty);
+	int actual;
 
-	/* Set up the "AX25 Control Block". (And clear statistics) */
-	memset(ax, 0, sizeof (struct ax_disp));
-	ax->magic  = AX25_MAGIC;
-	ax->dev	   = dev;
+	if (!ax)
+		return;
 
-	/* Finish setting up the DEVICE info. */
-	dev->mtu             = AX_MTU;
-	dev->hard_start_xmit = ax_xmit;
-	dev->open            = ax_open_dev;
-	dev->stop            = ax_close;
-	dev->get_stats	     = ax_get_stats;
-	dev->set_mac_address = ax_set_dev_mac_address;
-	dev->hard_header_len = 0;
-	dev->addr_len        = 0;
-	dev->type            = ARPHRD_AX25;
-	dev->tx_queue_len    = 10;
-	dev->hard_header     = ax_header;
-	dev->rebuild_header  = ax_rebuild_header;
+	if (ax->xleft <= 0)  {
+		/* Now serial buffer is almost free & we can start
+		 * transmission of another packet
+		 */
+		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
 
-	memcpy(dev->broadcast, ax25_bcast, AX25_ADDR_LEN);
-	memcpy(dev->dev_addr,  ax25_test,  AX25_ADDR_LEN);
+		netif_wake_queue(ax->dev);
+		goto out;
+	}
 
-	/* New-style flags. */
-	dev->flags      = IFF_BROADCAST | IFF_MULTICAST;
+	actual = tty->driver->write(tty, ax->xhead, ax->xleft);
+	ax->xleft -= actual;
+	ax->xhead += actual;
 
-	return 0;
+out:
+	mkiss_put(ax);
 }
 
+static struct tty_ldisc ax_ldisc = {
+	.magic		= TTY_LDISC_MAGIC,
+	.name		= "mkiss",
+	.open		= mkiss_open,
+	.close		= mkiss_close,
+	.ioctl		= mkiss_ioctl,
+	.receive_buf	= mkiss_receive_buf,
+	.receive_room	= mkiss_receive_room,
+	.write_wakeup	= mkiss_write_wakeup
+};
 
-/* ******************************************************************** */
-/* *			Init MKISS driver			      * */
-/* ******************************************************************** */
+static char banner[] __initdata = KERN_INFO \
+	"mkiss: AX.25 Multikiss, Hans Albas PE1AYX\n";
+static char msg_regfail[] __initdata = KERN_ERR \
+	"mkiss: can't register line discipline (err = %d)\n";
 
 static int __init mkiss_init_driver(void)
 {
@@ -887,64 +885,27 @@ static int __init mkiss_init_driver(void)
 
 	printk(banner);
 
-	if (ax25_maxdev < 4)
-	  ax25_maxdev = 4; /* Sanity */
+	if ((status = tty_register_ldisc(N_AX25, &ax_ldisc)) != 0)
+		printk(msg_regfail);
 
-	if ((ax25_ctrls = kmalloc(sizeof(void *) * ax25_maxdev, GFP_KERNEL)) == NULL) {
-		printk(KERN_ERR "mkiss: Can't allocate ax25_ctrls[] array!\n");
-		return -ENOMEM;
-	}
-
-	/* Clear the pointer array, we allocate devices when we need them */
-	memset(ax25_ctrls, 0, sizeof(void*) * ax25_maxdev); /* Pointers */
-
-	/* Fill in our line protocol discipline, and register it */
-	ax_ldisc.magic		= TTY_LDISC_MAGIC;
-	ax_ldisc.name		= "mkiss";
-	ax_ldisc.open		= ax25_open;
-	ax_ldisc.close		= ax25_close;
-	ax_ldisc.ioctl		= (int (*)(struct tty_struct *, struct file *,
-					unsigned int, unsigned long))ax25_disp_ioctl;
-	ax_ldisc.receive_buf	= ax25_receive_buf;
-	ax_ldisc.receive_room	= ax25_receive_room;
-	ax_ldisc.write_wakeup	= ax25_write_wakeup;
-
-	if ((status = tty_register_ldisc(N_AX25, &ax_ldisc)) != 0) {
-		printk(KERN_ERR "mkiss: can't register line discipline (err = %d)\n", status);
-		kfree(ax25_ctrls);
-	}
 	return status;
 }
 
+static const char msg_unregfail[] __exitdata = KERN_ERR \
+	"mkiss: can't unregister line discipline (err = %d)\n";
+
 static void __exit mkiss_exit_driver(void)
 {
-	int i;
-
-	for (i = 0; i < ax25_maxdev; i++) {
-		if (ax25_ctrls[i]) {
-			/*
-			* VSV = if dev->start==0, then device
-			* unregistered while close proc.
-			*/
-			if (netif_running(&ax25_ctrls[i]->dev))
-				unregister_netdev(&ax25_ctrls[i]->dev);
-			kfree(ax25_ctrls[i]);
-		}
-	}
+	int ret;
 
-	kfree(ax25_ctrls);
-	ax25_ctrls = NULL;
-
-	if ((i = tty_unregister_ldisc(N_AX25)))
-		printk(KERN_ERR "mkiss: can't unregister line discipline (err = %d)\n", i);
+	if ((ret = tty_unregister_ldisc(N_AX25)))
+		printk(msg_unregfail, ret);
 }
 
-MODULE_AUTHOR("Hans Albas PE1AYX <hans@esrac.ele.tue.nl>");
+MODULE_AUTHOR("Ralf Baechle DL5RB <ralf@linux-mips.org>");
 MODULE_DESCRIPTION("KISS driver for AX.25 over TTYs");
-MODULE_PARM(ax25_maxdev, "i");
-MODULE_PARM_DESC(ax25_maxdev, "number of MKISS devices");
 MODULE_LICENSE("GPL");
 MODULE_ALIAS_LDISC(N_AX25);
+
 module_init(mkiss_init_driver);
 module_exit(mkiss_exit_driver);
-