Linux-2.6.12-rc2

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!

1 files changed, 1051 insertions, 0 deletions

diff --git a/drivers/net/hamradio/6pack.c b/drivers/net/hamradio/6pack.c
new file mode 100644
index 000000000000..067b353e1cbd
--- /dev/null
+++ b/drivers/net/hamradio/6pack.c
@@ -0,0 +1,1051 @@
+/*
+ * 6pack.c	This module implements the 6pack protocol for kernel-based
+ *		devices like TTY. It interfaces between a raw TTY and the
+ *		kernel's AX.25 protocol layers.
+ *
+ * Authors:	Andreas Könsgen <ajk@iehk.rwth-aachen.de>
+ *              Ralf Baechle DL5RB <ralf@linux-mips.org>
+ *
+ * Quite a lot of stuff "stolen" by Joerg Reuter from slip.c, written by
+ *
+ *		Laurence Culhane, <loz@holmes.demon.co.uk>
+ *		Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
+ */
+
+#include <linux/config.h>
+#include <linux/module.h>
+#include <asm/system.h>
+#include <asm/uaccess.h>
+#include <linux/bitops.h>
+#include <linux/string.h>
+#include <linux/mm.h>
+#include <linux/interrupt.h>
+#include <linux/in.h>
+#include <linux/tty.h>
+#include <linux/errno.h>
+#include <linux/netdevice.h>
+#include <linux/timer.h>
+#include <net/ax25.h>
+#include <linux/etherdevice.h>
+#include <linux/skbuff.h>
+#include <linux/rtnetlink.h>
+#include <linux/spinlock.h>
+#include <linux/if_arp.h>
+#include <linux/init.h>
+#include <linux/ip.h>
+#include <linux/tcp.h>
+#include <asm/semaphore.h>
+#include <asm/atomic.h>
+
+#define SIXPACK_VERSION    "Revision: 0.3.0"
+
+/* sixpack priority commands */
+#define SIXP_SEOF		0x40	/* start and end of a 6pack frame */
+#define SIXP_TX_URUN		0x48	/* transmit overrun */
+#define SIXP_RX_ORUN		0x50	/* receive overrun */
+#define SIXP_RX_BUF_OVL		0x58	/* receive buffer overflow */
+
+#define SIXP_CHKSUM		0xFF	/* valid checksum of a 6pack frame */
+
+/* masks to get certain bits out of the status bytes sent by the TNC */
+
+#define SIXP_CMD_MASK		0xC0
+#define SIXP_CHN_MASK		0x07
+#define SIXP_PRIO_CMD_MASK	0x80
+#define SIXP_STD_CMD_MASK	0x40
+#define SIXP_PRIO_DATA_MASK	0x38
+#define SIXP_TX_MASK		0x20
+#define SIXP_RX_MASK		0x10
+#define SIXP_RX_DCD_MASK	0x18
+#define SIXP_LEDS_ON		0x78
+#define SIXP_LEDS_OFF		0x60
+#define SIXP_CON		0x08
+#define SIXP_STA		0x10
+
+#define SIXP_FOUND_TNC		0xe9
+#define SIXP_CON_ON		0x68
+#define SIXP_DCD_MASK		0x08
+#define SIXP_DAMA_OFF		0
+
+/* default level 2 parameters */
+#define SIXP_TXDELAY			(HZ/4)	/* in 1 s */
+#define SIXP_PERSIST			50	/* in 256ths */
+#define SIXP_SLOTTIME			(HZ/10)	/* in 1 s */
+#define SIXP_INIT_RESYNC_TIMEOUT	(3*HZ/2) /* in 1 s */
+#define SIXP_RESYNC_TIMEOUT		5*HZ	/* in 1 s */
+
+/* 6pack configuration. */
+#define SIXP_NRUNIT			31      /* MAX number of 6pack channels */
+#define SIXP_MTU			256	/* Default MTU */
+
+enum sixpack_flags {
+	SIXPF_ERROR,	/* Parity, etc. error	*/
+};
+
+struct sixpack {
+	/* Various fields. */
+	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. */
+	unsigned char		*rbuff;		/* receiver buffer	*/
+	int			rcount;         /* received chars counter  */
+	unsigned char		*xbuff;		/* transmitter buffer	*/
+	unsigned char		*xhead;         /* next byte to XMIT */
+	int			xleft;          /* bytes left in XMIT queue  */
+
+	unsigned char		raw_buf[4];
+	unsigned char		cooked_buf[400];
+
+	unsigned int		rx_count;
+	unsigned int		rx_count_cooked;
+
+	/* 6pack interface statistics. */
+	struct net_device_stats stats;
+
+	int			mtu;		/* Our mtu (to spot changes!) */
+	int			buffsize;       /* Max buffers sizes */
+
+	unsigned long		flags;		/* Flag values/ mode etc */
+	unsigned char		mode;		/* 6pack mode */
+
+	/* 6pack stuff */
+	unsigned char		tx_delay;
+	unsigned char		persistence;
+	unsigned char		slottime;
+	unsigned char		duplex;
+	unsigned char		led_state;
+	unsigned char		status;
+	unsigned char		status1;
+	unsigned char		status2;
+	unsigned char		tx_enable;
+	unsigned char		tnc_state;
+
+	struct timer_list	tx_t;
+	struct timer_list	resync_t;
+	atomic_t		refcnt;
+	struct semaphore	dead_sem;
+	spinlock_t		lock;
+};
+
+#define AX25_6PACK_HEADER_LEN 0
+
+static void sp_start_tx_timer(struct sixpack *);
+static void sixpack_decode(struct sixpack *, unsigned char[], int);
+static int encode_sixpack(unsigned char *, unsigned char *, int, unsigned char);
+
+/*
+ * perform the persistence/slottime algorithm for CSMA access. If the
+ * persistence check was successful, write the data to the serial driver.
+ * Note that in case of DAMA operation, the data is not sent here.
+ */
+
+static void sp_xmit_on_air(unsigned long channel)
+{
+	struct sixpack *sp = (struct sixpack *) channel;
+	int actual;
+	static unsigned char random;
+
+	random = random * 17 + 41;
+
+	if (((sp->status1 & SIXP_DCD_MASK) == 0) && (random < sp->persistence)) {
+		sp->led_state = 0x70;
+		sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+		sp->tx_enable = 1;
+		actual = sp->tty->driver->write(sp->tty, sp->xbuff, sp->status2);
+		sp->xleft -= actual;
+		sp->xhead += actual;
+		sp->led_state = 0x60;
+		sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+		sp->status2 = 0;
+	} else
+		sp_start_tx_timer(sp);
+}
+
+/* ----> 6pack timer interrupt handler and friends. <---- */
+static void sp_start_tx_timer(struct sixpack *sp)
+{
+	int when = sp->slottime;
+
+	del_timer(&sp->tx_t);
+	sp->tx_t.data = (unsigned long) sp;
+	sp->tx_t.function = sp_xmit_on_air;
+	sp->tx_t.expires = jiffies + ((when + 1) * HZ) / 100;
+	add_timer(&sp->tx_t);
+}
+
+/* Encapsulate one AX.25 frame and stuff into a TTY queue. */
+static void sp_encaps(struct sixpack *sp, unsigned char *icp, int len)
+{
+	unsigned char *msg, *p = icp;
+	int actual, count;
+
+	if (len > sp->mtu) {	/* sp->mtu = AX25_MTU = max. PACLEN = 256 */
+		msg = "oversized transmit packet!";
+		goto out_drop;
+	}
+
+	if (len > sp->mtu) {	/* sp->mtu = AX25_MTU = max. PACLEN = 256 */
+		msg = "oversized transmit packet!";
+		goto out_drop;
+	}
+
+	if (p[0] > 5) {
+		msg = "invalid KISS command";
+		goto out_drop;
+	}
+
+	if ((p[0] != 0) && (len > 2)) {
+		msg = "KISS control packet too long";
+		goto out_drop;
+	}
+
+	if ((p[0] == 0) && (len < 15)) {
+		msg = "bad AX.25 packet to transmit";
+		goto out_drop;
+	}
+
+	count = encode_sixpack(p, sp->xbuff, len, sp->tx_delay);
+	set_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags);
+
+	switch (p[0]) {
+	case 1:	sp->tx_delay = p[1];
+		return;
+	case 2:	sp->persistence = p[1];
+		return;
+	case 3:	sp->slottime = p[1];
+		return;
+	case 4:	/* ignored */
+		return;
+	case 5:	sp->duplex = p[1];
+		return;
+	}
+
+	if (p[0] != 0)
+		return;
+
+	/*
+	 * In case of fullduplex or DAMA operation, we don't take care about the
+	 * state of the DCD or of any timers, as the determination of the
+	 * correct time to send is the job of the AX.25 layer. We send
+	 * immediately after data has arrived.
+	 */
+	if (sp->duplex == 1) {
+		sp->led_state = 0x70;
+		sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+		sp->tx_enable = 1;
+		actual = sp->tty->driver->write(sp->tty, sp->xbuff, count);
+		sp->xleft = count - actual;
+		sp->xhead = sp->xbuff + actual;
+		sp->led_state = 0x60;
+		sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+	} else {
+		sp->xleft = count;
+		sp->xhead = sp->xbuff;
+		sp->status2 = count;
+		if (sp->duplex == 0)
+			sp_start_tx_timer(sp);
+	}
+
+	return;
+
+out_drop:
+	sp->stats.tx_dropped++;
+	netif_start_queue(sp->dev);
+	if (net_ratelimit())
+		printk(KERN_DEBUG "%s: %s - dropped.\n", sp->dev->name, msg);
+}
+
+/* Encapsulate an IP datagram and kick it into a TTY queue. */
+
+static int sp_xmit(struct sk_buff *skb, struct net_device *dev)
+{
+	struct sixpack *sp = netdev_priv(dev);
+
+	spin_lock_bh(&sp->lock);
+	/* We were not busy, so we are now... :-) */
+	netif_stop_queue(dev);
+	sp->stats.tx_bytes += skb->len;
+	sp_encaps(sp, skb->data, skb->len);
+	spin_unlock_bh(&sp->lock);
+
+	dev_kfree_skb(skb);
+
+	return 0;
+}
+
+static int sp_open_dev(struct net_device *dev)
+{
+	struct sixpack *sp = netdev_priv(dev);
+
+	if (sp->tty == NULL)
+		return -ENODEV;
+	return 0;
+}
+
+/* Close the low-level part of the 6pack channel. */
+static int sp_close(struct net_device *dev)
+{
+	struct sixpack *sp = netdev_priv(dev);
+
+	spin_lock_bh(&sp->lock);
+	if (sp->tty) {
+		/* TTY discipline is running. */
+		clear_bit(TTY_DO_WRITE_WAKEUP, &sp->tty->flags);
+	}
+	netif_stop_queue(dev);
+	spin_unlock_bh(&sp->lock);
+
+	return 0;
+}
+
+/* Return the frame type ID */
+static int sp_header(struct sk_buff *skb, struct net_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 struct net_device_stats *sp_get_stats(struct net_device *dev)
+{
+	struct sixpack *sp = netdev_priv(dev);
+	return &sp->stats;
+}
+
+static int sp_set_mac_address(struct net_device *dev, void *addr)
+{
+	struct sockaddr_ax25 *sa = addr;
+
+	if (sa->sax25_family != AF_AX25)
+		return -EINVAL;
+
+	if (!sa->sax25_ndigis)
+		return -EINVAL;
+
+	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 int sp_rebuild_header(struct sk_buff *skb)
+{
+#ifdef CONFIG_INET
+	return ax25_rebuild_header(skb);
+#else
+	return 0;
+#endif
+}
+
+static void sp_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		= SIXP_MTU;
+	dev->hard_start_xmit	= sp_xmit;
+	dev->open		= sp_open_dev;
+	dev->destructor		= free_netdev;
+	dev->stop		= sp_close;
+	dev->hard_header	= sp_header;
+	dev->get_stats	        = sp_get_stats;
+	dev->set_mac_address    = sp_set_mac_address;
+	dev->hard_header_len	= AX25_MAX_HEADER_LEN;
+	dev->addr_len		= AX25_ADDR_LEN;
+	dev->type		= ARPHRD_AX25;
+	dev->tx_queue_len	= 10;
+	dev->rebuild_header	= sp_rebuild_header;
+	dev->tx_timeout		= NULL;
+
+	/* Only activated in AX.25 mode */
+	memcpy(dev->broadcast, ax25_bcast, AX25_ADDR_LEN);
+	memcpy(dev->dev_addr, ax25_test, AX25_ADDR_LEN);
+
+	SET_MODULE_OWNER(dev);
+
+	dev->flags		= 0;
+}
+
+/* Send one completely decapsulated IP datagram to the IP layer. */
+
+/*
+ * This is the routine that sends the received data to the kernel AX.25.
+ * 'cmd' is the KISS command. For AX.25 data, it is zero.
+ */
+
+static void sp_bump(struct sixpack *sp, char cmd)
+{
+	struct sk_buff *skb;
+	int count;
+	unsigned char *ptr;
+
+	count = sp->rcount + 1;
+
+	sp->stats.rx_bytes += count;
+
+	if ((skb = dev_alloc_skb(count)) == NULL)
+		goto out_mem;
+
+	skb->dev = sp->dev;
+	ptr = skb_put(skb, count);
+	*ptr++ = cmd;	/* KISS command */
+
+	memcpy(ptr, sp->cooked_buf + 1, count);
+	skb->mac.raw = skb->data;
+	skb->protocol = htons(ETH_P_AX25);
+	netif_rx(skb);
+	sp->dev->last_rx = jiffies;
+	sp->stats.rx_packets++;
+
+	return;
+
+out_mem:
+	sp->stats.rx_dropped++;
+}
+
+
+/* ----------------------------------------------------------------------- */
+
+/*
+ * 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 DEFINE_RWLOCK(disc_data_lock);
+                                                                                
+static struct sixpack *sp_get(struct tty_struct *tty)
+{
+	struct sixpack *sp;
+
+	read_lock(&disc_data_lock);
+	sp = tty->disc_data;
+	if (sp)
+		atomic_inc(&sp->refcnt);
+	read_unlock(&disc_data_lock);
+
+	return sp;
+}
+
+static void sp_put(struct sixpack *sp)
+{
+	if (atomic_dec_and_test(&sp->refcnt))
+		up(&sp->dead_sem);
+}
+
+/*
+ * Called by the TTY driver when there's room for more data.  If we have
+ * more packets to send, we send them here.
+ */
+static void sixpack_write_wakeup(struct tty_struct *tty)
+{
+	struct sixpack *sp = sp_get(tty);
+	int actual;
+
+	if (!sp)
+		return;
+	if (sp->xleft <= 0)  {
+		/* Now serial buffer is almost free & we can start
+		 * transmission of another packet */
+		sp->stats.tx_packets++;
+		clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
+		sp->tx_enable = 0;
+		netif_wake_queue(sp->dev);
+		goto out;
+	}
+
+	if (sp->tx_enable) {
+		actual = tty->driver->write(tty, sp->xhead, sp->xleft);
+		sp->xleft -= actual;
+		sp->xhead += actual;
+	}
+
+out:
+	sp_put(sp);
+}
+
+/* ----------------------------------------------------------------------- */
+
+static int sixpack_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 6pack data has been received, which can now be decapsulated
+ * and sent on to some IP layer for further processing.
+ */
+static void sixpack_receive_buf(struct tty_struct *tty,
+	const unsigned char *cp, char *fp, int count)
+{
+	struct sixpack *sp;
+	unsigned char buf[512];
+	int count1;
+
+	if (!count)
+		return;
+
+	sp = sp_get(tty);
+	if (!sp)
+		return;
+
+	memcpy(buf, cp, count < sizeof(buf) ? count : sizeof(buf));
+
+	/* Read the characters out of the buffer */
+
+	count1 = count;
+	while (count) {
+		count--;
+		if (fp && *fp++) {
+			if (!test_and_set_bit(SIXPF_ERROR, &sp->flags))
+				sp->stats.rx_errors++;
+			continue;
+		}
+	}
+	sixpack_decode(sp, buf, count1);
+
+	sp_put(sp);
+	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags)
+	    && tty->driver->unthrottle)
+		tty->driver->unthrottle(tty);
+}
+
+/*
+ * Try to resync the TNC. Called by the resync timer defined in
+ * decode_prio_command
+ */
+
+#define TNC_UNINITIALIZED	0
+#define TNC_UNSYNC_STARTUP	1
+#define TNC_UNSYNCED		2
+#define TNC_IN_SYNC		3
+
+static void __tnc_set_sync_state(struct sixpack *sp, int new_tnc_state)
+{
+	char *msg;
+
+	switch (new_tnc_state) {
+	default:			/* gcc oh piece-o-crap ... */
+	case TNC_UNSYNC_STARTUP:
+		msg = "Synchronizing with TNC";
+		break;
+	case TNC_UNSYNCED:
+		msg = "Lost synchronization with TNC\n";
+		break;
+	case TNC_IN_SYNC:
+		msg = "Found TNC";
+		break;
+	}
+
+	sp->tnc_state = new_tnc_state;
+	printk(KERN_INFO "%s: %s\n", sp->dev->name, msg);
+}
+
+static inline void tnc_set_sync_state(struct sixpack *sp, int new_tnc_state)
+{
+	int old_tnc_state = sp->tnc_state;
+
+	if (old_tnc_state != new_tnc_state)
+		__tnc_set_sync_state(sp, new_tnc_state);
+}
+
+static void resync_tnc(unsigned long channel)
+{
+	struct sixpack *sp = (struct sixpack *) channel;
+	static char resync_cmd = 0xe8;
+
+	/* clear any data that might have been received */
+
+	sp->rx_count = 0;
+	sp->rx_count_cooked = 0;
+
+	/* reset state machine */
+
+	sp->status = 1;
+	sp->status1 = 1;
+	sp->status2 = 0;
+
+	/* resync the TNC */
+
+	sp->led_state = 0x60;
+	sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+	sp->tty->driver->write(sp->tty, &resync_cmd, 1);
+
+
+	/* Start resync timer again -- the TNC might be still absent */
+
+	del_timer(&sp->resync_t);
+	sp->resync_t.data	= (unsigned long) sp;
+	sp->resync_t.function	= resync_tnc;
+	sp->resync_t.expires	= jiffies + SIXP_RESYNC_TIMEOUT;
+	add_timer(&sp->resync_t);
+}
+
+static inline int tnc_init(struct sixpack *sp)
+{
+	unsigned char inbyte = 0xe8;
+
+	tnc_set_sync_state(sp, TNC_UNSYNC_STARTUP);
+
+	sp->tty->driver->write(sp->tty, &inbyte, 1);
+
+	del_timer(&sp->resync_t);
+	sp->resync_t.data = (unsigned long) sp;
+	sp->resync_t.function = resync_tnc;
+	sp->resync_t.expires = jiffies + SIXP_RESYNC_TIMEOUT;
+	add_timer(&sp->resync_t);
+
+	return 0;
+}
+
+/*
+ * Open the high-level part of the 6pack channel.
+ * This function is called by the TTY module when the
+ * 6pack line discipline is called for.  Because we are
+ * sure the tty line exists, we only have to link it to
+ * a free 6pcack channel...
+ */
+static int sixpack_open(struct tty_struct *tty)
+{
+	char *rbuff = NULL, *xbuff = NULL;
+	struct net_device *dev;
+	struct sixpack *sp;
+	unsigned long len;
+	int err = 0;
+
+	if (!capable(CAP_NET_ADMIN))
+		return -EPERM;
+
+	dev = alloc_netdev(sizeof(struct sixpack), "sp%d", sp_setup);
+	if (!dev) {
+		err = -ENOMEM;
+		goto out;
+	}
+
+	sp = netdev_priv(dev);
+	sp->dev = dev;
+
+	spin_lock_init(&sp->lock);
+	atomic_set(&sp->refcnt, 1);
+	init_MUTEX_LOCKED(&sp->dead_sem);
+
+	/* !!! length of the buffers. MTU is IP MTU, not PACLEN!  */
+
+	len = dev->mtu * 2;
+
+	rbuff = kmalloc(len + 4, GFP_KERNEL);
+	xbuff = kmalloc(len + 4, GFP_KERNEL);
+
+	if (rbuff == NULL || xbuff == NULL) {
+		err = -ENOBUFS;
+		goto out_free;
+	}
+
+	spin_lock_bh(&sp->lock);
+
+	sp->tty = tty;
+
+	sp->rbuff	= rbuff;
+	sp->xbuff	= xbuff;
+
+	sp->mtu		= AX25_MTU + 73;
+	sp->buffsize	= len;
+	sp->rcount	= 0;
+	sp->rx_count	= 0;
+	sp->rx_count_cooked = 0;
+	sp->xleft	= 0;
+
+	sp->flags	= 0;		/* Clear ESCAPE & ERROR flags */
+
+	sp->duplex	= 0;
+	sp->tx_delay    = SIXP_TXDELAY;
+	sp->persistence = SIXP_PERSIST;
+	sp->slottime    = SIXP_SLOTTIME;
+	sp->led_state   = 0x60;
+	sp->status      = 1;
+	sp->status1     = 1;
+	sp->status2     = 0;
+	sp->tx_enable   = 0;
+
+	netif_start_queue(dev);
+
+	init_timer(&sp->tx_t);
+	init_timer(&sp->resync_t);
+
+	spin_unlock_bh(&sp->lock);
+
+	/* Done.  We have linked the TTY line to a channel. */
+	tty->disc_data = sp;
+
+	/* Now we're ready to register. */
+	if (register_netdev(dev))
+		goto out_free;
+
+	tnc_init(sp);
+
+	return 0;
+
+out_free:
+	kfree(xbuff);
+	kfree(rbuff);
+
+	if (dev)
+		free_netdev(dev);
+
+out:
+	return err;
+}
+
+
+/*
+ * Close down a 6pack channel.
+ * This means flushing out any pending queues, and then restoring the
+ * TTY line discipline to what it was before it got hooked to 6pack
+ * (which usually is TTY again).
+ */
+static void sixpack_close(struct tty_struct *tty)
+{
+	struct sixpack *sp;
+
+	write_lock(&disc_data_lock);
+	sp = tty->disc_data;
+	tty->disc_data = NULL;
+	write_unlock(&disc_data_lock);
+	if (sp == 0)
+		return;
+
+	/*
+	 * 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(&sp->refcnt))
+		down(&sp->dead_sem);
+
+	unregister_netdev(sp->dev);
+
+	del_timer(&sp->tx_t);
+	del_timer(&sp->resync_t);
+
+	/* Free all 6pack frame buffers. */
+	kfree(sp->rbuff);
+	kfree(sp->xbuff);
+}
+
+/* Perform I/O control on an active 6pack channel. */
+static int sixpack_ioctl(struct tty_struct *tty, struct file *file,
+	unsigned int cmd, unsigned long arg)
+{
+	struct sixpack *sp = sp_get(tty);
+	struct net_device *dev = sp->dev;
+	unsigned int tmp, err;
+
+	if (!sp)
+		return -ENXIO;
+
+	switch(cmd) {
+	case SIOCGIFNAME:
+		err = copy_to_user((void __user *) arg, dev->name,
+		                   strlen(dev->name) + 1) ? -EFAULT : 0;
+		break;
+
+	case SIOCGIFENCAP:
+		err = put_user(0, (int __user *) arg);
+		break;
+
+	case SIOCSIFENCAP:
+		if (get_user(tmp, (int __user *) arg)) {
+			err = -EFAULT;
+			break;
+		}
+
+		sp->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;
+
+		err = 0;
+		break;
+
+	 case SIOCSIFHWADDR: {
+		char addr[AX25_ADDR_LEN];
+
+		if (copy_from_user(&addr,
+		                   (void __user *) arg, AX25_ADDR_LEN)) {
+			err = -EFAULT;
+			break;
+		}
+
+		spin_lock_irq(&dev->xmit_lock);
+		memcpy(dev->dev_addr, &addr, AX25_ADDR_LEN);
+		spin_unlock_irq(&dev->xmit_lock);
+
+		err = 0;
+		break;
+	}
+
+	/* Allow stty to read, but not set, the serial port */
+	case TCGETS:
+	case TCGETA:
+		err = n_tty_ioctl(tty, (struct file *) file, cmd, arg);
+		break;
+
+	default:
+		err = -ENOIOCTLCMD;
+	}
+
+	sp_put(sp);
+
+	return err;
+}
+
+static struct tty_ldisc sp_ldisc = {
+	.owner		= THIS_MODULE,
+	.magic		= TTY_LDISC_MAGIC,
+	.name		= "6pack",
+	.open		= sixpack_open,
+	.close		= sixpack_close,
+	.ioctl		= sixpack_ioctl,
+	.receive_buf	= sixpack_receive_buf,
+	.receive_room	= sixpack_receive_room,
+	.write_wakeup	= sixpack_write_wakeup,
+};
+
+/* Initialize 6pack control device -- register 6pack line discipline */
+
+static char msg_banner[]  __initdata = KERN_INFO \
+	"AX.25: 6pack driver, " SIXPACK_VERSION "\n";
+static char msg_regfail[] __initdata = KERN_ERR  \
+	"6pack: can't register line discipline (err = %d)\n";
+
+static int __init sixpack_init_driver(void)
+{
+	int status;
+
+	printk(msg_banner);
+
+	/* Register the provided line protocol discipline */
+	if ((status = tty_register_ldisc(N_6PACK, &sp_ldisc)) != 0)
+		printk(msg_regfail, status);
+
+	return status;
+}
+
+static const char msg_unregfail[] __exitdata = KERN_ERR \
+	"6pack: can't unregister line discipline (err = %d)\n";
+
+static void __exit sixpack_exit_driver(void)
+{
+	int ret;
+
+	if ((ret = tty_register_ldisc(N_6PACK, NULL)))
+		printk(msg_unregfail, ret);
+}
+
+/* encode an AX.25 packet into 6pack */
+
+static int encode_sixpack(unsigned char *tx_buf, unsigned char *tx_buf_raw,
+	int length, unsigned char tx_delay)
+{
+	int count = 0;
+	unsigned char checksum = 0, buf[400];
+	int raw_count = 0;
+
+	tx_buf_raw[raw_count++] = SIXP_PRIO_CMD_MASK | SIXP_TX_MASK;
+	tx_buf_raw[raw_count++] = SIXP_SEOF;
+
+	buf[0] = tx_delay;
+	for (count = 1; count < length; count++)
+		buf[count] = tx_buf[count];
+
+	for (count = 0; count < length; count++)
+		checksum += buf[count];
+	buf[length] = (unsigned char) 0xff - checksum;
+
+	for (count = 0; count <= length; count++) {
+		if ((count % 3) == 0) {
+			tx_buf_raw[raw_count++] = (buf[count] & 0x3f);
+			tx_buf_raw[raw_count] = ((buf[count] >> 2) & 0x30);
+		} else if ((count % 3) == 1) {
+			tx_buf_raw[raw_count++] |= (buf[count] & 0x0f);
+			tx_buf_raw[raw_count] =	((buf[count] >> 2) & 0x3c);
+		} else {
+			tx_buf_raw[raw_count++] |= (buf[count] & 0x03);
+			tx_buf_raw[raw_count++] = (buf[count] >> 2);
+		}
+	}
+	if ((length % 3) != 2)
+		raw_count++;
+	tx_buf_raw[raw_count++] = SIXP_SEOF;
+	return raw_count;
+}
+
+/* decode 4 sixpack-encoded bytes into 3 data bytes */
+
+static void decode_data(struct sixpack *sp, unsigned char inbyte)
+{
+	unsigned char *buf;
+
+	if (sp->rx_count != 3) {
+		sp->raw_buf[sp->rx_count++] = inbyte;
+
+		return;
+	}
+
+	buf = sp->raw_buf;
+	sp->cooked_buf[sp->rx_count_cooked++] =
+		buf[0] | ((buf[1] << 2) & 0xc0);
+	sp->cooked_buf[sp->rx_count_cooked++] =
+		(buf[1] & 0x0f) | ((buf[2] << 2) & 0xf0);
+	sp->cooked_buf[sp->rx_count_cooked++] =
+		(buf[2] & 0x03) | (inbyte << 2);
+	sp->rx_count = 0;
+}
+
+/* identify and execute a 6pack priority command byte */
+
+static void decode_prio_command(struct sixpack *sp, unsigned char cmd)
+{
+	unsigned char channel;
+	int actual;
+
+	channel = cmd & SIXP_CHN_MASK;
+	if ((cmd & SIXP_PRIO_DATA_MASK) != 0) {     /* idle ? */
+
+	/* RX and DCD flags can only be set in the same prio command,
+	   if the DCD flag has been set without the RX flag in the previous
+	   prio command. If DCD has not been set before, something in the
+	   transmission has gone wrong. In this case, RX and DCD are
+	   cleared in order to prevent the decode_data routine from
+	   reading further data that might be corrupt. */
+
+		if (((sp->status & SIXP_DCD_MASK) == 0) &&
+			((cmd & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK)) {
+				if (sp->status != 1)
+					printk(KERN_DEBUG "6pack: protocol violation\n");
+				else
+					sp->status = 0;
+				cmd &= !SIXP_RX_DCD_MASK;
+		}
+		sp->status = cmd & SIXP_PRIO_DATA_MASK;
+	} else { /* output watchdog char if idle */
+		if ((sp->status2 != 0) && (sp->duplex == 1)) {
+			sp->led_state = 0x70;
+			sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+			sp->tx_enable = 1;
+			actual = sp->tty->driver->write(sp->tty, sp->xbuff, sp->status2);
+			sp->xleft -= actual;
+			sp->xhead += actual;
+			sp->led_state = 0x60;
+			sp->status2 = 0;
+
+		}
+	}
+
+	/* needed to trigger the TNC watchdog */
+	sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+
+        /* if the state byte has been received, the TNC is present,
+           so the resync timer can be reset. */
+
+	if (sp->tnc_state == TNC_IN_SYNC) {
+		del_timer(&sp->resync_t);
+		sp->resync_t.data	= (unsigned long) sp;
+		sp->resync_t.function	= resync_tnc;
+		sp->resync_t.expires	= jiffies + SIXP_INIT_RESYNC_TIMEOUT;
+		add_timer(&sp->resync_t);
+	}
+
+	sp->status1 = cmd & SIXP_PRIO_DATA_MASK;
+}
+
+/* identify and execute a standard 6pack command byte */
+
+static void decode_std_command(struct sixpack *sp, unsigned char cmd)
+{
+	unsigned char checksum = 0, rest = 0, channel;
+	short i;
+
+	channel = cmd & SIXP_CHN_MASK;
+	switch (cmd & SIXP_CMD_MASK) {     /* normal command */
+	case SIXP_SEOF:
+		if ((sp->rx_count == 0) && (sp->rx_count_cooked == 0)) {
+			if ((sp->status & SIXP_RX_DCD_MASK) ==
+				SIXP_RX_DCD_MASK) {
+				sp->led_state = 0x68;
+				sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+			}
+		} else {
+			sp->led_state = 0x60;
+			/* fill trailing bytes with zeroes */
+			sp->tty->driver->write(sp->tty, &sp->led_state, 1);
+			rest = sp->rx_count;
+			if (rest != 0)
+				 for (i = rest; i <= 3; i++)
+					decode_data(sp, 0);
+			if (rest == 2)
+				sp->rx_count_cooked -= 2;
+			else if (rest == 3)
+				sp->rx_count_cooked -= 1;
+			for (i = 0; i < sp->rx_count_cooked; i++)
+				checksum += sp->cooked_buf[i];
+			if (checksum != SIXP_CHKSUM) {
+				printk(KERN_DEBUG "6pack: bad checksum %2.2x\n", checksum);
+			} else {
+				sp->rcount = sp->rx_count_cooked-2;
+				sp_bump(sp, 0);
+			}
+			sp->rx_count_cooked = 0;
+		}
+		break;
+	case SIXP_TX_URUN: printk(KERN_DEBUG "6pack: TX underrun\n");
+		break;
+	case SIXP_RX_ORUN: printk(KERN_DEBUG "6pack: RX overrun\n");
+		break;
+	case SIXP_RX_BUF_OVL:
+		printk(KERN_DEBUG "6pack: RX buffer overflow\n");
+	}
+}
+
+/* decode a 6pack packet */
+
+static void
+sixpack_decode(struct sixpack *sp, unsigned char *pre_rbuff, int count)
+{
+	unsigned char inbyte;
+	int count1;
+
+	for (count1 = 0; count1 < count; count1++) {
+		inbyte = pre_rbuff[count1];
+		if (inbyte == SIXP_FOUND_TNC) {
+			tnc_set_sync_state(sp, TNC_IN_SYNC);
+			del_timer(&sp->resync_t);
+		}
+		if ((inbyte & SIXP_PRIO_CMD_MASK) != 0)
+			decode_prio_command(sp, inbyte);
+		else if ((inbyte & SIXP_STD_CMD_MASK) != 0)
+			decode_std_command(sp, inbyte);
+		else if ((sp->status & SIXP_RX_DCD_MASK) == SIXP_RX_DCD_MASK)
+			decode_data(sp, inbyte);
+	}
+}
+
+MODULE_AUTHOR("Ralf Baechle DO1GRB <ralf@linux-mips.org>");
+MODULE_DESCRIPTION("6pack driver for AX.25");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS_LDISC(N_6PACK);
+
+module_init(sixpack_init_driver);
+module_exit(sixpack_exit_driver);