patch-2.1.71 linux/drivers/net/hamradio/mkiss.c

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diff -u --recursive --new-file v2.1.70/linux/drivers/net/hamradio/mkiss.c linux/drivers/net/hamradio/mkiss.c
@@ -0,0 +1,1134 @@
+/*
+ *	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
+ *	Jonathan (G4KLX)	Fixed to match Linux networking changes - 2.1.15.
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <asm/system.h>
+#include <asm/segment.h>
+#include <asm/bitops.h>
+#include <asm/uaccess.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/init.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 (!test_and_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] = 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 "mkiss: 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 (!test_and_clear_bit(AXF_INUSE, &ax->flags))
+		printk(KERN_ERR "mkiss: %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 = kmalloc(len + 4, GFP_ATOMIC);
+	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",
+		       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 (test_and_set_bit(0, (void *)&ax->dev->tbusy))
+		printk(KERN_ERR "mkiss: %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 (!test_and_clear_bit(0, (void *)&ax->dev->tbusy))
+		printk(KERN_ERR "mkiss: %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 "mkiss: %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 "mkiss: %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 "mkiss: %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 "mkiss: %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);
+		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(struct sk_buff *skb)
+{
+#ifdef CONFIG_INET
+	return ax25_rebuild_header(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 = kmalloc(len + 4, GFP_KERNEL)) == NULL)
+		goto norbuff;
+
+	if ((ax->xbuff = 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 */
+	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 (!test_and_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;
+	if (ax->dev->flags & IFF_UP)
+	{
+		dev_lock_wait();
+		dev_close(ax->dev);
+		dev_unlock_list();
+	}
+
+	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 net_device_stats *ax_get_stats(struct device *dev)
+{
+	static struct net_device_stats stats;
+	struct ax_disp *ax = (struct ax_disp*)dev->priv;
+
+	memset(&stats, 0, sizeof(struct net_device_stats));
+
+	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 (!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;
+	}
+
+	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 */
+	copy_from_user(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;
+			copy_to_user(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;
+			get_user(tmp, (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 */
+__initfunc(int mkiss_init_ctrl_dev(void))
+{
+	int status;
+
+	if (ax25_maxdev < 4) ax25_maxdev = 4; /* Sanity */
+
+	if ((ax25_ctrls = 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.name   = "mkiss";
+	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.poll   = 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;
+
+	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
+
+	dev_init_buffers(dev);
+
+	/* New-style flags. */
+	dev->flags      = 0;
+
+	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 			      * */
+/* ******************************************************************** */
+
+__initfunc(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 "mkiss: couldn't register Mkiss device\n");
+		return -EIO;
+	}
+
+	printk(KERN_INFO "AX.25 Multikiss device enabled\n");
+
+	return 0;
+}
+
+#ifdef MODULE
+EXPORT_NO_SYMBOLS;
+
+MODULE_PARM(ax25_maxdev, "i");
+MODULE_PARM_DESC(ax25_maxdev, "number of MKISS devices");
+
+MODULE_AUTHOR("Hans Albas PE1AYX <hans@esrac.ele.tue.nl>");
+MODULE_DESCRIPTION("KISS driver for AX.25 over TTYs");
+
+int init_module(void)
+{
+	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 */
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