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/*
 *	MKISS Driver
 *
 *	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 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 seperated 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.
 *
 * Hans Alblas <hans@esrac.ele.tue.nl>
 *
 *	History
 */
 
#include <linux/config.h>
#include <linux/module.h>
#include <asm/system.h>
#include <asm/segment.h>
#include <asm/bitops.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/in.h>
#include <linux/inet.h>
#include <linux/tty.h>
#include <linux/errno.h>
#include <linux/netdevice.h>
#include <linux/major.h>
 
#include <linux/timer.h>
 
#include <linux/etherdevice.h>
#include <linux/skbuff.h>
#include <linux/if_arp.h>
 
#include <net/ax25.h>
 
#include "mkiss.h"
 
#ifdef CONFIG_INET
#include <linux/ip.h>
#include <linux/tcp.h>
#endif
 
#ifdef MODULE
#define AX25_VERSION    "AX25-MODULAR-NET3.019-NEWTTY"
#define	min(a,b)	(a < b ? a : b)
#else
#define	AX25_VERSION	"AX25-NET3.019-NEWTTY"
#endif
 
#define NR_MKISS 4
#define MKISS_SERIAL_TYPE_NORMAL 1
 
struct mkiss_channel {
	int magic;		/* magic word */
	int init;		/* channel exists? */
	struct tty_struct *tty; /* link to tty control structure */
};
 
typedef struct ax25_ctrl {
	char if_name[8];	/* "ax0\0" .. "ax99999\0"	*/
	struct ax_disp ctrl;	/* 				*/
	struct device  dev;	/* the device			*/
} ax25_ctrl_t;
 
static ax25_ctrl_t **ax25_ctrls = NULL;
int ax25_maxdev = AX25_MAXDEV;		/* Can be overridden with insmod! */
 
static struct tty_ldisc	ax_ldisc;
static struct tty_driver mkiss_driver;
static int mkiss_refcount;
static struct tty_struct *mkiss_table[NR_MKISS];
static struct termios *mkiss_termios[NR_MKISS];
static struct termios *mkiss_termios_locked[NR_MKISS];
struct mkiss_channel MKISS_Info[NR_MKISS];
 
static int ax25_init(struct device *);
static int mkiss_init(void);
static int mkiss_write(struct tty_struct *, int, const unsigned char *, int);
static int kiss_esc(unsigned char *, unsigned char *, int);
static void kiss_unesc(struct ax_disp *, unsigned char);
 
/* Find a free channel, and link in this `tty' line. */
static inline struct ax_disp *ax_alloc(void)
{
	ax25_ctrl_t *axp;
	int i;
 
	if (ax25_ctrls == NULL)		/* Master array missing ! */
		return NULL;
 
	for (i = 0; i < ax25_maxdev; i++) {
		axp = ax25_ctrls[i];
 
		/* Not allocated ? */
		if (axp == NULL)
			break;
 
		/* Not in use ? */
		if (!set_bit(AXF_INUSE, &axp->ctrl.flags))
			break;
	}
 
	/* Sorry, too many, all slots in use */
	if (i >= ax25_maxdev)
		return NULL;
 
	/* If no channels are available, allocate one */
	if (axp == NULL && (ax25_ctrls[i] = (ax25_ctrl_t *)kmalloc(sizeof(ax25_ctrl_t), GFP_KERNEL)) != NULL) {
		axp = ax25_ctrls[i];
		memset(axp, 0, sizeof(ax25_ctrl_t));
 
		/* Initialize channel control data */
		set_bit(AXF_INUSE, &axp->ctrl.flags);
		sprintf(axp->if_name, "ax%d", i++);
		axp->ctrl.tty      = NULL;
		axp->dev.name      = axp->if_name;
		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 "ax_alloc() - register_netdev() failure.\n");
		}
	}
 
	return NULL;
}
 
/* Free an AX25 channel. */
static inline void ax_free(struct ax_disp *ax)
{
	/* Free all AX25 frame buffers. */
	if (ax->rbuff)
		kfree(ax->rbuff);
	ax->rbuff = NULL;
	if (ax->xbuff)
		kfree(ax->xbuff);
	ax->xbuff = NULL;
	if (!clear_bit(AXF_INUSE, &ax->flags))
		printk(KERN_ERR "%s: ax_free for already free unit.\n", ax->dev->name);
}
 
static void ax_changedmtu(struct ax_disp *ax)
{
	struct device *dev = ax->dev;
	unsigned char *xbuff, *rbuff, *oxbuff, *orbuff;
	int len;
	unsigned long flags;
 
	len = dev->mtu * 2;
 
	/*
	 * allow for arrival of larger UDP packets, even if we say not to
	 * also fixes a bug in which SunOS sends 512-byte packets even with
	 * an MSS of 128
	 */
	if (len < 576 * 2)
		len = 576 * 2;
 
	xbuff = (unsigned char *)kmalloc(len + 4, GFP_ATOMIC);
	rbuff = (unsigned char *)kmalloc(len + 4, GFP_ATOMIC);
 
	if (xbuff == NULL || rbuff == NULL)  {
		printk(KERN_ERR "%s: unable to grow ax25 buffers, MTU change cancelled.\n",
		       ax->dev->name);
		dev->mtu = ax->mtu;
		if (xbuff != NULL)
			kfree(xbuff);
		if (rbuff != NULL)
			kfree(rbuff);
		return;
	}
 
	save_flags(flags);
	cli();
 
	oxbuff    = ax->xbuff;
	ax->xbuff = xbuff;
	orbuff    = ax->rbuff;
	ax->rbuff = rbuff;
 
	if (ax->xleft) {
		if (ax->xleft <= len) {
			memcpy(ax->xbuff, ax->xhead, ax->xleft);
		} else  {
			ax->xleft = 0;
			ax->tx_dropped++;
		}
	}
 
	ax->xhead = ax->xbuff;
 
	if (ax->rcount) {
		if (ax->rcount <= len) {
			memcpy(ax->rbuff, orbuff, ax->rcount);
		} else  {
			ax->rcount = 0;
			ax->rx_over_errors++;
			set_bit(AXF_ERROR, &ax->flags);
		}
	}
 
	ax->mtu      = dev->mtu + 73;
	ax->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 ax_lock(struct ax_disp *ax)
{
	if (set_bit(0, (void *)&ax->dev->tbusy))
		printk(KERN_ERR "%s: trying to lock already locked device!\n", ax->dev->name);
}
 
 
/* Clear the "sending" flag.  This must be atomic, hence the ASM. */
static inline void ax_unlock(struct ax_disp *ax)
{
	if (!clear_bit(0, (void *)&ax->dev->tbusy))
		printk(KERN_ERR "%s: trying to unlock already unlocked device!\n", ax->dev->name);
}
 
/* Send one completely decapsulated AX.25 packet to the AX.25 layer. */
static void ax_bump(struct ax_disp *ax)
{
	struct ax_disp *tmp_ax;
	struct sk_buff *skb;
	struct mkiss_channel *mkiss;
	int count;
 
        tmp_ax = ax;
 
	if (ax->rbuff[0] > 0x0f) {
		if (ax->mkiss != NULL) {
			mkiss= ax->mkiss->tty->driver_data;
			if (mkiss->magic == MKISS_DRIVER_MAGIC)
				tmp_ax = ax->mkiss;
		}
 	}
 
	count = ax->rcount;
 
	if ((skb = dev_alloc_skb(count)) == NULL) {
		printk(KERN_ERR "%s: memory squeeze, dropping packet.\n", ax->dev->name);
		ax->rx_dropped++;
		return;
	}
 
	skb->dev      = tmp_ax->dev;
	memcpy(skb_put(skb,count), ax->rbuff, count);
	skb->mac.raw  = skb->data;
	skb->protocol = htons(ETH_P_AX25);
	netif_rx(skb);
	tmp_ax->rx_packets++;
}
 
/* Encapsulate one AX.25 packet and stuff into a TTY queue. */
static void ax_encaps(struct ax_disp *ax, unsigned char *icp, int len)
{
	unsigned char *p;
	int actual, count;
	struct mkiss_channel *mkiss = ax->tty->driver_data;
 
	if (ax->mtu != ax->dev->mtu + 73)	/* Someone has been ifconfigging */
		ax_changedmtu(ax);
 
	if (len > ax->mtu) {		/* Sigh, shouldn't occur BUT ... */
		len = ax->mtu;
		printk(KERN_ERR "%s: truncating oversized transmit packet!\n", ax->dev->name);
		ax->tx_dropped++;
		ax_unlock(ax);
		return;
	}
 
	p = icp;
 
	if (mkiss->magic  != MKISS_DRIVER_MAGIC) {
		count = kiss_esc(p, (unsigned char *)ax->xbuff, len);
		ax->tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
		actual = ax->tty->driver.write(ax->tty, 0, ax->xbuff, count);
		ax->tx_packets++;
		ax->dev->trans_start = jiffies;
		ax->xleft = count - actual;
		ax->xhead = ax->xbuff + actual;
	} else {
		count = kiss_esc(p, (unsigned char *) ax->mkiss->xbuff, len);
		ax->mkiss->tty->flags |= (1 << TTY_DO_WRITE_WAKEUP);
		actual = ax->mkiss->tty->driver.write(ax->mkiss->tty, 0, ax->mkiss->xbuff, count);
		ax->tx_packets++;
		ax->mkiss->dev->trans_start = jiffies;
		ax->mkiss->xleft = count - actual;
		ax->mkiss->xhead = ax->mkiss->xbuff + actual;
	}
}
 
/*
 * 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;
	struct mkiss_channel *mkiss;
 
	/* First make sure we're connected. */
	if (ax == NULL || ax->magic != AX25_MAGIC || !ax->dev->start)
		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);
 
		if (ax->mkiss != NULL) {
			mkiss= ax->mkiss->tty->driver_data;
	        	if (mkiss->magic  == MKISS_DRIVER_MAGIC)
				ax_unlock(ax->mkiss);
	        }
 
		ax_unlock(ax);
		mark_bh(NET_BH);
		return;
	}
 
	actual = tty->driver.write(tty, 0, 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 device *dev)
{
	struct ax_disp *ax = (struct ax_disp*)dev->priv;
	struct mkiss_channel *mkiss = ax->tty->driver_data;
	struct ax_disp *tmp_ax;
 
	tmp_ax = NULL;
 
	if (mkiss->magic  == MKISS_DRIVER_MAGIC) {
		if (skb->data[0] < 0x10)
			skb->data[0] = skb->data[0] + 0x10;
		tmp_ax = ax->mkiss;
	}
 
	if (!dev->start)  {
		printk(KERN_ERR "%s: xmit call when iface is down\n", dev->name);
		return 1;
	}
 
	if (tmp_ax != NULL)
		if (tmp_ax->dev->tbusy)
			return 1;
 
	if (tmp_ax != NULL)
		if (dev->tbusy) {
			printk(KERN_ERR "mkiss: dev busy while serial dev is free\n");
			ax_unlock(ax);
	        }
 
	if (dev->tbusy) {
		/*
		 * May be we must check transmitter timeout here ?
		 *      14 Oct 1994 Dmitry Gorodchanin.
		 */
		if (jiffies - dev->trans_start  < 20 * HZ) {
			/* 20 sec timeout not reached */
			return 1;
		}
 
		printk(KERN_ERR "%s: transmit timed out, %s?\n", dev->name,
		       (ax->tty->driver.chars_in_buffer(ax->tty) || ax->xleft) ?
		       "bad line quality" : "driver error");
 
		ax->xleft = 0;
		ax->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
		ax_unlock(ax);
	}
 
	/* We were not busy, so we are now... :-) */
	if (skb != NULL) {
		ax_lock(ax);
		if (tmp_ax != NULL)
			ax_lock(tmp_ax);
		ax_encaps(ax, skb->data, skb->len);
		dev_kfree_skb(skb, FREE_WRITE);
	}
 
	return 0;
}
 
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
 
/* Return the frame type ID */
static int ax_header(struct sk_buff *skb, struct device *dev, unsigned short type,
	  void *daddr, void *saddr, unsigned len)
{
#ifdef CONFIG_INET
	if (type != htons(ETH_P_AX25))
		return ax25_encapsulate(skb, dev, type, daddr, saddr, len);
#endif
	return 0;
}
 
 
static int ax_rebuild_header(void *buff, struct device *dev, unsigned long raddr, struct sk_buff *skb)
{
#ifdef CONFIG_INET
	return ax25_rebuild_header(buff, dev, raddr, skb);
#else
	return 0;
#endif
}
 
#endif /* CONFIG_{AX25,AX25_MODULE} */
 
/* Open the low-level part of the AX25 channel. Easy! */
static int ax_open(struct device *dev)
{
	struct ax_disp *ax = (struct ax_disp*)dev->priv;
	unsigned long len;
 
	if (ax->tty == NULL)
		return -ENODEV;
 
	/*
	 * Allocate the frame buffers:
	 *
	 * rbuff	Receive buffer.
	 * xbuff	Transmit buffer.
	 * cbuff        Temporary compression buffer.
	 */
	len = dev->mtu * 2;
 
	/*
	 * allow for arrival of larger UDP packets, even if we say not to
	 * also fixes a bug in which SunOS sends 512-byte packets even with
	 * an MSS of 128
	 */
	if (len < 576 * 2)
		len = 576 * 2;
 
	if ((ax->rbuff = (unsigned char *) kmalloc(len + 4, GFP_KERNEL)) == NULL)
		goto norbuff;
 
	if ((ax->xbuff = (unsigned char *) kmalloc(len + 4, GFP_KERNEL)) == NULL)
		goto noxbuff;
 
	ax->mtu	     = dev->mtu + 73;
	ax->buffsize = len;
	ax->rcount   = 0;
	ax->xleft    = 0;
 
	ax->flags   &= (1 << AXF_INUSE);      /* Clear ESCAPE & ERROR flags */
	/* Needed because address '0' is special */
	if (dev->pa_addr == 0)
		dev->pa_addr = ntohl(0xC0A80001);
	dev->tbusy  = 0;
	dev->start  = 1;
 
	return 0;
 
	/* Cleanup */
	kfree(ax->xbuff);
 
noxbuff:
	kfree(ax->rbuff);
 
norbuff:
	return -ENOMEM;
}
 
 
/* Close the low-level part of the AX25 channel. Easy! */
static int ax_close(struct device *dev)
{
	struct ax_disp *ax = (struct ax_disp*)dev->priv;
 
	if (ax->tty == NULL)
		return -EBUSY;
 
	ax->tty->flags &= ~(1 << TTY_DO_WRITE_WAKEUP);
 
	dev->tbusy = 1;
	dev->start = 0;
 
	return 0;
}
 
static int ax25_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 data has been received, which can now be decapsulated
 * and sent on to the AX.25 layer for further processing.
 */
static void ax25_receive_buf(struct tty_struct *tty, const unsigned char *cp, char *fp, int count)
{
	struct ax_disp *ax = (struct ax_disp *)tty->disc_data;
 
	if (ax == NULL || ax->magic != AX25_MAGIC || !ax->dev->start)
		return;
 
	/*
	 * 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 (!set_bit(AXF_ERROR, &ax->flags))
				ax->rx_errors++;
			cp++;
			continue;
		}
 
		kiss_unesc(ax, *cp++);
	}
}
 
static int ax25_open(struct tty_struct *tty)
{
	struct ax_disp *ax = (struct ax_disp *)tty->disc_data;
	struct ax_disp *tmp_ax;
	struct mkiss_channel *mkiss;
	int err, cnt;
 
	/* First make sure we're not already connected. */
	if (ax && ax->magic == AX25_MAGIC)
		return -EEXIST;
 
	/* OK.  Find a free AX25 channel to use. */
	if ((ax = ax_alloc()) == NULL)
		return -ENFILE;
 
	ax->tty = tty;
	tty->disc_data = ax;
 
	ax->mkiss = NULL;
	tmp_ax    = NULL;
 
	if (tty->driver.flush_buffer)
		tty->driver.flush_buffer(tty);
	if (tty->ldisc.flush_buffer)
		tty->ldisc.flush_buffer(tty);
 
	/* Restore default settings */
	ax->dev->type = ARPHRD_AX25;
 
	/* Perform the low-level AX25 initialization. */
	if ((err = ax_open(ax->dev)))
		return err;
 
	mkiss= ax->tty->driver_data;
 
	if (mkiss->magic  == MKISS_DRIVER_MAGIC) {
		for (cnt = 1; cnt < ax25_maxdev; cnt++) {
			if (ax25_ctrls[cnt]) {
				if (ax25_ctrls[cnt]->dev.start) {
					if (ax == &ax25_ctrls[cnt]->ctrl) {
						cnt--;
						tmp_ax = &ax25_ctrls[cnt]->ctrl;
						break;
					}
				}
			}
		}
	}
 
	if (tmp_ax != NULL) {
		ax->mkiss     = tmp_ax;
		tmp_ax->mkiss = ax;
	}
 
	MOD_INC_USE_COUNT;
 
	/* Done.  We have linked the TTY line to a channel. */
	return ax->dev->base_addr;
}
 
static void ax25_close(struct tty_struct *tty)
{
	struct ax_disp *ax = (struct ax_disp *)tty->disc_data;
	int mkiss ;
 
	/* First make sure we're connected. */
	if (ax == NULL || ax->magic != AX25_MAGIC)
		return;
 
	mkiss = ax->mode;
	dev_close(ax->dev);
 
	tty->disc_data = 0;
	ax->tty        = NULL;
 
	/* VSV = very important to remove timers */
	ax_free(ax);
	unregister_netdev(ax->dev);
 
	MOD_DEC_USE_COUNT;
}
 
 
static struct enet_statistics *ax_get_stats(struct device *dev)
{
	static struct enet_statistics stats;
	struct ax_disp *ax = (struct ax_disp*)dev->priv;
 
	memset(&stats, 0, sizeof(struct enet_statistics));
 
	stats.rx_packets     = ax->rx_packets;
	stats.tx_packets     = ax->tx_packets;
	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;
}
 
 
/************************************************************************
 *			   STANDARD ENCAPSULATION	        	 *
 ************************************************************************/
 
int kiss_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++ = 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;
		}
	}
 
	*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);
 
			if (!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 (clear_bit(AXF_ESCAPE, &ax->flags))
				s = ESC;
			break;
		case ESC_END:
			if (clear_bit(AXF_ESCAPE, &ax->flags))
				s = END;
			break;
	}
 
	if (!test_bit(AXF_ERROR, &ax->flags)) {
		if (ax->rcount < ax->buffsize) {
			ax->rbuff[ax->rcount++] = s;
			return;
		}
 
		ax->rx_over_errors++;
		set_bit(AXF_ERROR, &ax->flags);
	}
}
 
 
int ax_set_mac_address(struct device *dev, void *addr)
{
	int err;
 
	if ((err = verify_area(VERIFY_READ, addr, AX25_ADDR_LEN)) != 0)
		return err;
 
	/* addr is an AX.25 shifted ASCII mac address */
	memcpy_fromfs(dev->dev_addr, addr, AX25_ADDR_LEN);
 
	return 0;
}
 
static int ax_set_dev_mac_address(struct device *dev, void *addr)
{
	struct sockaddr *sa = addr;
 
	memcpy(dev->dev_addr, sa->sa_data, AX25_ADDR_LEN);
 
	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 *arg)
{
	struct ax_disp *ax = (struct ax_disp *)tty->disc_data;
	int err;
	unsigned int tmp;
 
	/* First make sure we're connected. */
	if (ax == NULL || ax->magic != AX25_MAGIC)
		return -EINVAL;
 
	switch (cmd) {
	 	case SIOCGIFNAME:
			if ((err = verify_area(VERIFY_WRITE, arg, strlen(ax->dev->name) + 1)) != 0)
				return err;
			memcpy_tofs(arg, ax->dev->name, strlen(ax->dev->name) + 1);
			return 0;
 
		case SIOCGIFENCAP:
			if ((err = verify_area(VERIFY_WRITE, arg, sizeof(int))) != 0)
				return err;
			put_user(4, (int *)arg);
			return 0;
 
		case SIOCSIFENCAP:
			if ((err = verify_area(VERIFY_READ, arg, sizeof(int))) != 0)
				return err;
			tmp = get_user((int *)arg);
	 		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);
 
		default:
			return -ENOIOCTLCMD;
	}
}
 
static int ax_open_dev(struct device *dev)
{
	struct ax_disp *ax = (struct ax_disp*)dev->priv;
 
	if (ax->tty==NULL)
		return -ENODEV;
 
	return 0;
}
 
/* Initialize AX25 control device -- register AX25 line discipline */
int mkiss_init_ctrl_dev(void)
{
	int status;
 
	if (ax25_maxdev < 4) ax25_maxdev = 4; /* Sanity */
 
	if ((ax25_ctrls = (ax25_ctrl_t **)kmalloc(sizeof(void*) * ax25_maxdev, GFP_KERNEL)) == NULL) {
		printk(KERN_ERR "mkiss: Can't allocate ax25_ctrls[] array !  No mkiss available\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 */
	memset(&ax_ldisc, 0, sizeof(ax_ldisc));
	ax_ldisc.magic  = TTY_LDISC_MAGIC;
	ax_ldisc.flags  = 0;
	ax_ldisc.open   = ax25_open;
	ax_ldisc.close  = ax25_close;
	ax_ldisc.read   = NULL;
	ax_ldisc.write  = NULL;
	ax_ldisc.ioctl  = (int (*)(struct tty_struct *, struct file *, unsigned int, unsigned long))ax25_disp_ioctl;
	ax_ldisc.select = NULL;
 
	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);
 
	mkiss_init();
 
#ifdef MODULE
	return status;
#else
	/*
	 * Return "not found", so that dev_init() will unlink
	 * the placeholder device entry for us.
	 */
	return ENODEV;
#endif
}
 
 
/* Initialize the driver.  Called by network startup. */
 
static int ax25_init(struct device *dev)
{
	struct ax_disp *ax = (struct ax_disp*)dev->priv;
	int i;
 
	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;
 
	/* Set up the "AX25 Control Block". (And clear statistics) */
	memset(ax, 0, sizeof (struct ax_disp));
	ax->magic  = AX25_MAGIC;
	ax->dev	   = dev;
 
	/* 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;
#ifdef HAVE_SET_MAC_ADDR
	dev->set_mac_address = ax_set_dev_mac_address;
#endif
	dev->hard_header_len = 0;
	dev->addr_len        = 0;
	dev->type            = ARPHRD_AX25;
	dev->tx_queue_len    = 10;
 
	memcpy(dev->broadcast, ax25_bcast, AX25_ADDR_LEN);
	memcpy(dev->dev_addr,  ax25_test,  AX25_ADDR_LEN);
 
#if defined(CONFIG_AX25) || defined(CONFIG_AX25_MODULE)
	dev->hard_header     = ax_header;
	dev->rebuild_header  = ax_rebuild_header;
#endif
 
	for (i = 0; i < DEV_NUMBUFFS; i++)
		skb_queue_head_init(&dev->buffs[i]);
 
	/* New-style flags. */
	dev->flags      = 0;
	dev->family     = AF_INET;
 
#ifdef CONFIG_INET
	dev->pa_addr    = in_aton("192.168.0.1");
	dev->pa_brdaddr = in_aton("192.168.0.255");
	dev->pa_mask    = in_aton("255.255.255.0");
	dev->pa_alen    = 4;
#endif
 
	return 0;
}
 
static int mkiss_open(struct tty_struct *tty, struct file *filp)
{
	struct mkiss_channel *mkiss;
	int chan;
 
	chan = MINOR(tty->device) - tty->driver.minor_start;
 
	if (chan < 0 || chan >= NR_MKISS)
		return -ENODEV;
 
	mkiss = &MKISS_Info[chan];
 
	mkiss->magic =  MKISS_DRIVER_MAGIC;
	mkiss->init  = 1;
	mkiss->tty   = tty;
 
	tty->driver_data = mkiss;
 
	tty->termios->c_iflag  = IGNBRK | IGNPAR;
	tty->termios->c_cflag  = B9600 | CS8 | CLOCAL;
	tty->termios->c_cflag &= ~CBAUD;
 
	return 0;
}
 
static void mkiss_close(struct tty_struct *tty, struct file * filp)
{
	struct mkiss_channel *mkiss = tty->driver_data;
 
	if (mkiss == NULL || mkiss->magic != MKISS_DRIVER_MAGIC)
                return;
 
	mkiss->tty   = NULL;
	mkiss->init  = 0;
	tty->stopped = 0;
}
 
static int mkiss_write(struct tty_struct *tty, int from_user, const unsigned char *buf, int count)
{
	return 0;
}
 
static int mkiss_ioctl(struct tty_struct *tty, struct file *file, unsigned int cmd, unsigned long arg)
{
	/* Ignore serial ioctl's */
	switch (cmd) {
		case TCSBRK:
		case TIOCMGET:
		case TIOCMBIS:
		case TIOCMBIC:
		case TIOCMSET:
		case TCSETS:
		case TCSETSF:		/* should flush first, but... */
		case TCSETSW:		/* should wait until flush, but... */
			return 0;
		default:
			return -ENOIOCTLCMD;
	}
}
 
 
static void mkiss_dummy(struct tty_struct *tty)
{
	struct mkiss_channel *mkiss = tty->driver_data;
 
	if (tty == NULL)
		return;
 
	if (mkiss == NULL)
		return;
}
 
static void mkiss_dummy2(struct tty_struct *tty, unsigned char ch)
{
	struct mkiss_channel *mkiss = tty->driver_data;
 
	if (tty == NULL)
		return;
 
	if (mkiss == NULL)
		return;
}
 
 
static int mkiss_write_room(struct tty_struct * tty)
{
	struct mkiss_channel *mkiss = tty->driver_data;
 
	if (tty == NULL)
		return 0;
 
	if (mkiss == NULL)
		return 0;
 
	return 65536;  /* We can handle an infinite amount of data. :-) */
}
 
 
static int mkiss_chars_in_buffer(struct tty_struct *tty)
{
	struct mkiss_channel *mkiss = tty->driver_data;
 
	if (tty == NULL)
		return 0;
 
	if (mkiss == NULL)
		return 0;
 
	return 0;
}
 
 
static void mkiss_set_termios(struct tty_struct *tty, struct termios *old_termios)
{
	/* we don't do termios */
}
 
/* ******************************************************************** */
/* * 			Init MKISS driver 			      * */
/* ******************************************************************** */
 
static int mkiss_init(void)
{
	memset(&mkiss_driver, 0, sizeof(struct tty_driver));
 
	mkiss_driver.magic       = MKISS_DRIVER_MAGIC;
	mkiss_driver.name        = "mkiss";
	mkiss_driver.major       = MKISS_MAJOR;
	mkiss_driver.minor_start = 0;
	mkiss_driver.num         = NR_MKISS;
	mkiss_driver.type        = TTY_DRIVER_TYPE_SERIAL;
	mkiss_driver.subtype     = MKISS_SERIAL_TYPE_NORMAL;	/* not needed */
 
	mkiss_driver.init_termios         = tty_std_termios;
	mkiss_driver.init_termios.c_iflag = IGNBRK | IGNPAR;
	mkiss_driver.init_termios.c_cflag = B9600 | CS8 | CLOCAL;
 
	mkiss_driver.flags           = TTY_DRIVER_REAL_RAW;
	mkiss_driver.refcount        = &mkiss_refcount;
	mkiss_driver.table           = mkiss_table;
	mkiss_driver.termios         = (struct termios **)mkiss_termios;
	mkiss_driver.termios_locked  = (struct termios **)mkiss_termios_locked;
 
	mkiss_driver.ioctl           = mkiss_ioctl;
	mkiss_driver.open            = mkiss_open;
	mkiss_driver.close           = mkiss_close;
	mkiss_driver.write           = mkiss_write;
	mkiss_driver.write_room      = mkiss_write_room;
	mkiss_driver.chars_in_buffer = mkiss_chars_in_buffer;
	mkiss_driver.set_termios     = mkiss_set_termios;
 
	/* some unused functions */
	mkiss_driver.flush_buffer = mkiss_dummy;
	mkiss_driver.throttle     = mkiss_dummy;
	mkiss_driver.unthrottle   = mkiss_dummy;
	mkiss_driver.stop         = mkiss_dummy;
	mkiss_driver.start        = mkiss_dummy;
	mkiss_driver.hangup       = mkiss_dummy;
	mkiss_driver.flush_chars  = mkiss_dummy;
	mkiss_driver.put_char     = mkiss_dummy2;
 
	if (tty_register_driver(&mkiss_driver)) {
		printk(KERN_ERR "Couldn't register Mkiss device\n");
		return -EIO;
	}
 
	printk(KERN_INFO "AX.25 Multikiss device enabled\n");
 
	return 0;
}
 
#ifdef MODULE
 
int init_module(void)
{
	register_symtab(NULL);
 
	return mkiss_init_ctrl_dev();
}
 
void cleanup_module(void)
{
	int i;
 
	if (ax25_ctrls != NULL) {
		for (i = 0; i < ax25_maxdev; i++) {
			if (ax25_ctrls[i]) {
				/*
				 * VSV = if dev->start==0, then device
				 * unregistred while close proc.
				 */
				if (ax25_ctrls[i]->dev.start)
					unregister_netdev(&(ax25_ctrls[i]->dev));
 
				kfree(ax25_ctrls[i]);
				ax25_ctrls[i] = NULL;
			}
		}
 
		kfree(ax25_ctrls);
		ax25_ctrls = NULL;
	}
 
	if ((i = tty_register_ldisc(N_AX25, NULL)))
		printk(KERN_ERR "mkiss: can't unregister line discipline (err = %d)\n", i);
 
	if (tty_unregister_driver(&mkiss_driver))	/* remove devive */
		printk(KERN_ERR "mkiss: can't unregister MKISS device\n");
}
 
#endif /* MODULE */