/* r3964 linediscipline for linux
   *
   * -----------------------------------------------------------
   * Copyright by 
   * Philips Automation Projects
   * Kassel (Germany)

   * -----------------------------------------------------------
   * This software may be used and distributed according to the terms of
   * the GNU General Public License, incorporated herein by reference.
   *
   * Author:
   * L. Haag
   *
   * $Log: n_r3964.c,v $
   * Revision 1.10  2001/03/18 13:02:24  dwmw2
   * Fix timer usage, use spinlocks properly.
   *
   * Revision 1.9  2001/03/18 12:52:14  dwmw2
   * Merge changes in 2.4.2
   *
   * Revision 1.8  2000/03/23 14:14:54  dwmw2
   * Fix race in sleeping in r3964_read()
   *
   * Revision 1.7  1999/28/08 11:41:50  dwmw2
   * Port to 2.3 kernel
   *
   * Revision 1.6  1998/09/30 00:40:40  dwmw2
   * Fixed compilation on 2.0.x kernels
   * Updated to newly registered tty-ldisc number 9
   *
   * Revision 1.5  1998/09/04 21:57:36  dwmw2
   * Signal handling bug fixes, port to 2.1.x.
   *
   * Revision 1.4  1998/04/02 20:26:59  lhaag
   * select, blocking, ...
   *
   * Revision 1.3  1998/02/12 18:58:43  root
   * fixed some memory leaks
   * calculation of checksum characters
   *
   * Revision 1.2  1998/02/07 13:03:34  root
   * ioctl read_telegram
   *
   * Revision 1.1  1998/02/06 19:21:03  root
   * Initial revision
   *
   *
   */
  
  #include <linux/module.h>
  #include <linux/kernel.h>
  #include <linux/sched.h>
  #include <linux/types.h>
  #include <linux/fcntl.h>
  #include <linux/interrupt.h>
  #include <linux/ptrace.h>
  #include <linux/ioport.h>
  #include <linux/in.h>
  #include <linux/slab.h>
  #include <linux/tty.h>
  #include <linux/errno.h>

  #include <linux/string.h>	/* used in new tty drivers */
  #include <linux/signal.h>	/* used in new tty drivers */

  #include <linux/ioctl.h>
  #include <linux/n_r3964.h>
  #include <linux/poll.h>
  #include <linux/init.h>
  #include <asm/uaccess.h>

  /*#define DEBUG_QUEUE*/

  
  /* Log successful handshake and protocol operations  */

  /*#define DEBUG_PROTO_S*/

  
  /* Log handshake and protocol errors: */

  /*#define DEBUG_PROTO_E*/

  
  /* Log Linediscipline operations (open, close, read, write...): */

  /*#define DEBUG_LDISC*/

  
  /* Log module and memory operations (init, cleanup; kmalloc, kfree): */

  /*#define DEBUG_MODUL*/

  
  /* Macro helpers for debug output: */

  #define TRACE(format, args...) printk("r3964: " format "
  " , ## args)

  
  #ifdef DEBUG_MODUL

  #define TRACE_M(format, args...) printk("r3964: " format "
  " , ## args)

  #else

  #define TRACE_M(fmt, arg...) do {} while (0)

  #endif

  #ifdef DEBUG_PROTO_S

  #define TRACE_PS(format, args...) printk("r3964: " format "
  " , ## args)

  #else

  #define TRACE_PS(fmt, arg...) do {} while (0)

  #endif

  #ifdef DEBUG_PROTO_E

  #define TRACE_PE(format, args...) printk("r3964: " format "
  " , ## args)

  #else

  #define TRACE_PE(fmt, arg...) do {} while (0)

  #endif

  #ifdef DEBUG_LDISC

  #define TRACE_L(format, args...) printk("r3964: " format "
  " , ## args)

  #else

  #define TRACE_L(fmt, arg...) do {} while (0)

  #endif

  #ifdef DEBUG_QUEUE

  #define TRACE_Q(format, args...) printk("r3964: " format "
  " , ## args)

  #else

  #define TRACE_Q(fmt, arg...) do {} while (0)

  #endif

  static void add_tx_queue(struct r3964_info *, struct r3964_block_header *);
  static void remove_from_tx_queue(struct r3964_info *pInfo, int error_code);
  static void put_char(struct r3964_info *pInfo, unsigned char ch);
  static void trigger_transmit(struct r3964_info *pInfo);
  static void retry_transmit(struct r3964_info *pInfo);
  static void transmit_block(struct r3964_info *pInfo);
  static void receive_char(struct r3964_info *pInfo, const unsigned char c);
  static void receive_error(struct r3964_info *pInfo, const char flag);
  static void on_timeout(unsigned long priv);

  static int enable_signals(struct r3964_info *pInfo, struct pid *pid, int arg);

  static int read_telegram(struct r3964_info *pInfo, struct pid *pid,
  		unsigned char __user * buf);

  static void add_msg(struct r3964_client_info *pClient, int msg_id, int arg,

  		int error_code, struct r3964_block_header *pBlock);
  static struct r3964_message *remove_msg(struct r3964_info *pInfo,
  		struct r3964_client_info *pClient);
  static void remove_client_block(struct r3964_info *pInfo,
  		struct r3964_client_info *pClient);

  static int r3964_open(struct tty_struct *tty);

  static void r3964_close(struct tty_struct *tty);
  static ssize_t r3964_read(struct tty_struct *tty, struct file *file,

  		unsigned char __user * buf, size_t nr);
  static ssize_t r3964_write(struct tty_struct *tty, struct file *file,
  		const unsigned char *buf, size_t nr);
  static int r3964_ioctl(struct tty_struct *tty, struct file *file,
  		unsigned int cmd, unsigned long arg);
  static void r3964_set_termios(struct tty_struct *tty, struct ktermios *old);
  static unsigned int r3964_poll(struct tty_struct *tty, struct file *file,
  		struct poll_table_struct *wait);

  static void r3964_receive_buf(struct tty_struct *tty, const unsigned char *cp,
  		char *fp, int count);

  static struct tty_ldisc_ops tty_ldisc_N_R3964 = {

  	.owner = THIS_MODULE,
  	.magic = TTY_LDISC_MAGIC,
  	.name = "R3964",
  	.open = r3964_open,
  	.close = r3964_close,
  	.read = r3964_read,
  	.write = r3964_write,
  	.ioctl = r3964_ioctl,

  	.set_termios = r3964_set_termios,

  	.poll = r3964_poll,

  	.receive_buf = r3964_receive_buf,

  };

  static void dump_block(const unsigned char *block, unsigned int length)
  {

  	unsigned int i, j;
  	char linebuf[16 * 3 + 1];
  
  	for (i = 0; i < length; i += 16) {
  		for (j = 0; (j < 16) && (j + i < length); j++) {
  			sprintf(linebuf + 3 * j, "%02x ", block[i + j]);
  		}
  		linebuf[3 * j] = '\0';
  		TRACE_PS("%s", linebuf);
  	}

  }

  /*************************************************************
   * Driver initialisation
   *************************************************************/

  /*************************************************************
   * Module support routines
   *************************************************************/
  
  static void __exit r3964_exit(void)
  {

  	int status;
  
  	TRACE_M("cleanup_module()");
  
  	status = tty_unregister_ldisc(N_R3964);
  
  	if (status != 0) {
  		printk(KERN_ERR "r3964: error unregistering linediscipline: "
  				"%d
  ", status);
  	} else {
  		TRACE_L("linediscipline successfully unregistered");
  	}

  }
  
  static int __init r3964_init(void)
  {

  	int status;
  
  	printk("r3964: Philips r3964 Driver $Revision: 1.10 $
  ");
  
  	/*
  	 * Register the tty line discipline
  	 */
  
  	status = tty_register_ldisc(N_R3964, &tty_ldisc_N_R3964);
  	if (status == 0) {
  		TRACE_L("line discipline %d registered", N_R3964);
  		TRACE_L("flags=%x num=%x", tty_ldisc_N_R3964.flags,
  			tty_ldisc_N_R3964.num);
  		TRACE_L("open=%p", tty_ldisc_N_R3964.open);
  		TRACE_L("tty_ldisc_N_R3964 = %p", &tty_ldisc_N_R3964);
  	} else {
  		printk(KERN_ERR "r3964: error registering line discipline: "
  				"%d
  ", status);
  	}
  	return status;

  }
  
  module_init(r3964_init);
  module_exit(r3964_exit);

  /*************************************************************
   * Protocol implementation routines
   *************************************************************/

  static void add_tx_queue(struct r3964_info *pInfo,
  			 struct r3964_block_header *pHeader)

  {

  	unsigned long flags;
  
  	spin_lock_irqsave(&pInfo->lock, flags);
  
  	pHeader->next = NULL;
  
  	if (pInfo->tx_last == NULL) {
  		pInfo->tx_first = pInfo->tx_last = pHeader;
  	} else {
  		pInfo->tx_last->next = pHeader;
  		pInfo->tx_last = pHeader;
  	}
  
  	spin_unlock_irqrestore(&pInfo->lock, flags);
  
  	TRACE_Q("add_tx_queue %p, length %d, tx_first = %p",
  		pHeader, pHeader->length, pInfo->tx_first);

  }
  
  static void remove_from_tx_queue(struct r3964_info *pInfo, int error_code)
  {

  	struct r3964_block_header *pHeader;
  	unsigned long flags;

  #ifdef DEBUG_QUEUE

  	struct r3964_block_header *pDump;

  #endif

  	pHeader = pInfo->tx_first;
  
  	if (pHeader == NULL)
  		return;

  
  #ifdef DEBUG_QUEUE

  	printk("r3964: remove_from_tx_queue: %p, length %u - ",
  		pHeader, pHeader->length);
  	for (pDump = pHeader; pDump; pDump = pDump->next)
  		printk("%p ", pDump);
  	printk("
  ");

  #endif

  	if (pHeader->owner) {
  		if (error_code) {
  			add_msg(pHeader->owner, R3964_MSG_ACK, 0,
  				error_code, NULL);
  		} else {
  			add_msg(pHeader->owner, R3964_MSG_ACK, pHeader->length,
  				error_code, NULL);
  		}
  		wake_up_interruptible(&pInfo->read_wait);
  	}
  
  	spin_lock_irqsave(&pInfo->lock, flags);
  
  	pInfo->tx_first = pHeader->next;
  	if (pInfo->tx_first == NULL) {
  		pInfo->tx_last = NULL;
  	}
  
  	spin_unlock_irqrestore(&pInfo->lock, flags);
  
  	kfree(pHeader);
  	TRACE_M("remove_from_tx_queue - kfree %p", pHeader);

  	TRACE_Q("remove_from_tx_queue: tx_first = %p, tx_last = %p",
  		pInfo->tx_first, pInfo->tx_last);

  }

  static void add_rx_queue(struct r3964_info *pInfo,
  			 struct r3964_block_header *pHeader)

  {

  	unsigned long flags;
  
  	spin_lock_irqsave(&pInfo->lock, flags);
  
  	pHeader->next = NULL;
  
  	if (pInfo->rx_last == NULL) {
  		pInfo->rx_first = pInfo->rx_last = pHeader;
  	} else {
  		pInfo->rx_last->next = pHeader;
  		pInfo->rx_last = pHeader;
  	}
  	pInfo->blocks_in_rx_queue++;
  
  	spin_unlock_irqrestore(&pInfo->lock, flags);
  
  	TRACE_Q("add_rx_queue: %p, length = %d, rx_first = %p, count = %d",
  		pHeader, pHeader->length,
  		pInfo->rx_first, pInfo->blocks_in_rx_queue);

  }
  
  static void remove_from_rx_queue(struct r3964_info *pInfo,

  				 struct r3964_block_header *pHeader)

  {

  	unsigned long flags;
  	struct r3964_block_header *pFind;
  
  	if (pHeader == NULL)
  		return;
  
  	TRACE_Q("remove_from_rx_queue: rx_first = %p, rx_last = %p, count = %d",
  		pInfo->rx_first, pInfo->rx_last, pInfo->blocks_in_rx_queue);
  	TRACE_Q("remove_from_rx_queue: %p, length %u",
  		pHeader, pHeader->length);
  
  	spin_lock_irqsave(&pInfo->lock, flags);
  
  	if (pInfo->rx_first == pHeader) {
  		/* Remove the first block in the linked list: */
  		pInfo->rx_first = pHeader->next;
  
  		if (pInfo->rx_first == NULL) {
  			pInfo->rx_last = NULL;
  		}
  		pInfo->blocks_in_rx_queue--;
  	} else {
  		/* Find block to remove: */
  		for (pFind = pInfo->rx_first; pFind; pFind = pFind->next) {
  			if (pFind->next == pHeader) {
  				/* Got it. */
  				pFind->next = pHeader->next;
  				pInfo->blocks_in_rx_queue--;
  				if (pFind->next == NULL) {
  					/* Oh, removed the last one! */
  					pInfo->rx_last = pFind;
  				}
  				break;
  			}
  		}
  	}
  
  	spin_unlock_irqrestore(&pInfo->lock, flags);
  
  	kfree(pHeader);
  	TRACE_M("remove_from_rx_queue - kfree %p", pHeader);
  
  	TRACE_Q("remove_from_rx_queue: rx_first = %p, rx_last = %p, count = %d",
  		pInfo->rx_first, pInfo->rx_last, pInfo->blocks_in_rx_queue);

  }
  
  static void put_char(struct r3964_info *pInfo, unsigned char ch)
  {

  	struct tty_struct *tty = pInfo->tty;

  	/* FIXME: put_char should not be called from an IRQ */

  	tty_put_char(tty, ch);

  	pInfo->bcc ^= ch;

  }
  
  static void flush(struct r3964_info *pInfo)
  {

  	struct tty_struct *tty = pInfo->tty;

  	if (tty == NULL || tty->ops->flush_chars == NULL)

  		return;

  	tty->ops->flush_chars(tty);

  }
  
  static void trigger_transmit(struct r3964_info *pInfo)
  {

  	unsigned long flags;

  	spin_lock_irqsave(&pInfo->lock, flags);

  	if ((pInfo->state == R3964_IDLE) && (pInfo->tx_first != NULL)) {
  		pInfo->state = R3964_TX_REQUEST;
  		pInfo->nRetry = 0;
  		pInfo->flags &= ~R3964_ERROR;
  		mod_timer(&pInfo->tmr, jiffies + R3964_TO_QVZ);

  		spin_unlock_irqrestore(&pInfo->lock, flags);

  		TRACE_PS("trigger_transmit - sent STX");

  		put_char(pInfo, STX);
  		flush(pInfo);

  		pInfo->bcc = 0;
  	} else {
  		spin_unlock_irqrestore(&pInfo->lock, flags);
  	}

  }
  
  static void retry_transmit(struct r3964_info *pInfo)
  {

  	if (pInfo->nRetry < R3964_MAX_RETRIES) {
  		TRACE_PE("transmission failed. Retry #%d", pInfo->nRetry);
  		pInfo->bcc = 0;
  		put_char(pInfo, STX);
  		flush(pInfo);
  		pInfo->state = R3964_TX_REQUEST;
  		pInfo->nRetry++;
  		mod_timer(&pInfo->tmr, jiffies + R3964_TO_QVZ);
  	} else {
  		TRACE_PE("transmission failed after %d retries",
  			 R3964_MAX_RETRIES);
  
  		remove_from_tx_queue(pInfo, R3964_TX_FAIL);
  
  		put_char(pInfo, NAK);
  		flush(pInfo);
  		pInfo->state = R3964_IDLE;
  
  		trigger_transmit(pInfo);
  	}

  }

  static void transmit_block(struct r3964_info *pInfo)
  {

  	struct tty_struct *tty = pInfo->tty;
  	struct r3964_block_header *pBlock = pInfo->tx_first;
  	int room = 0;

  	if (tty == NULL || pBlock == NULL) {

  		return;
  	}

  	room = tty_write_room(tty);

  
  	TRACE_PS("transmit_block %p, room %d, length %d",
  		 pBlock, room, pBlock->length);
  
  	while (pInfo->tx_position < pBlock->length) {
  		if (room < 2)
  			break;
  
  		if (pBlock->data[pInfo->tx_position] == DLE) {
  			/* send additional DLE char: */
  			put_char(pInfo, DLE);
  		}
  		put_char(pInfo, pBlock->data[pInfo->tx_position++]);
  
  		room--;
  	}
  
  	if ((pInfo->tx_position == pBlock->length) && (room >= 3)) {
  		put_char(pInfo, DLE);
  		put_char(pInfo, ETX);
  		if (pInfo->flags & R3964_BCC) {
  			put_char(pInfo, pInfo->bcc);
  		}
  		pInfo->state = R3964_WAIT_FOR_TX_ACK;
  		mod_timer(&pInfo->tmr, jiffies + R3964_TO_QVZ);
  	}
  	flush(pInfo);

  }
  
  static void on_receive_block(struct r3964_info *pInfo)
  {

  	unsigned int length;
  	struct r3964_client_info *pClient;
  	struct r3964_block_header *pBlock;
  
  	length = pInfo->rx_position;
  
  	/* compare byte checksum characters: */
  	if (pInfo->flags & R3964_BCC) {
  		if (pInfo->bcc != pInfo->last_rx) {
  			TRACE_PE("checksum error - got %x but expected %x",
  				 pInfo->last_rx, pInfo->bcc);
  			pInfo->flags |= R3964_CHECKSUM;
  		}
  	}
  
  	/* check for errors (parity, overrun,...): */
  	if (pInfo->flags & R3964_ERROR) {
  		TRACE_PE("on_receive_block - transmission failed error %x",
  			 pInfo->flags & R3964_ERROR);
  
  		put_char(pInfo, NAK);
  		flush(pInfo);
  		if (pInfo->nRetry < R3964_MAX_RETRIES) {
  			pInfo->state = R3964_WAIT_FOR_RX_REPEAT;
  			pInfo->nRetry++;
  			mod_timer(&pInfo->tmr, jiffies + R3964_TO_RX_PANIC);
  		} else {
  			TRACE_PE("on_receive_block - failed after max retries");
  			pInfo->state = R3964_IDLE;
  		}
  		return;
  	}
  
  	/* received block; submit DLE: */
  	put_char(pInfo, DLE);
  	flush(pInfo);
  	del_timer_sync(&pInfo->tmr);
  	TRACE_PS(" rx success: got %d chars", length);
  
  	/* prepare struct r3964_block_header: */
  	pBlock = kmalloc(length + sizeof(struct r3964_block_header),
  			GFP_KERNEL);
  	TRACE_M("on_receive_block - kmalloc %p", pBlock);
  
  	if (pBlock == NULL)
  		return;
  
  	pBlock->length = length;
  	pBlock->data = ((unsigned char *)pBlock) +
  			sizeof(struct r3964_block_header);
  	pBlock->locks = 0;
  	pBlock->next = NULL;
  	pBlock->owner = NULL;
  
  	memcpy(pBlock->data, pInfo->rx_buf, length);
  
  	/* queue block into rx_queue: */
  	add_rx_queue(pInfo, pBlock);
  
  	/* notify attached client processes: */
  	for (pClient = pInfo->firstClient; pClient; pClient = pClient->next) {
  		if (pClient->sig_flags & R3964_SIG_DATA) {
  			add_msg(pClient, R3964_MSG_DATA, length, R3964_OK,
  				pBlock);
  		}
  	}
  	wake_up_interruptible(&pInfo->read_wait);

  	pInfo->state = R3964_IDLE;
  
  	trigger_transmit(pInfo);
  }

  
  static void receive_char(struct r3964_info *pInfo, const unsigned char c)
  {

  	switch (pInfo->state) {
  	case R3964_TX_REQUEST:
  		if (c == DLE) {
  			TRACE_PS("TX_REQUEST - got DLE");
  
  			pInfo->state = R3964_TRANSMITTING;
  			pInfo->tx_position = 0;
  
  			transmit_block(pInfo);
  		} else if (c == STX) {
  			if (pInfo->nRetry == 0) {
  				TRACE_PE("TX_REQUEST - init conflict");
  				if (pInfo->priority == R3964_SLAVE) {
  					goto start_receiving;
  				}
  			} else {
  				TRACE_PE("TX_REQUEST - secondary init "
  					"conflict!? Switching to SLAVE mode "
  					"for next rx.");
  				goto start_receiving;
  			}
  		} else {
  			TRACE_PE("TX_REQUEST - char != DLE: %x", c);
  			retry_transmit(pInfo);
  		}
  		break;
  	case R3964_TRANSMITTING:
  		if (c == NAK) {
  			TRACE_PE("TRANSMITTING - got NAK");
  			retry_transmit(pInfo);
  		} else {
  			TRACE_PE("TRANSMITTING - got invalid char");
  
  			pInfo->state = R3964_WAIT_ZVZ_BEFORE_TX_RETRY;
  			mod_timer(&pInfo->tmr, jiffies + R3964_TO_ZVZ);
  		}
  		break;
  	case R3964_WAIT_FOR_TX_ACK:
  		if (c == DLE) {
  			TRACE_PS("WAIT_FOR_TX_ACK - got DLE");
  			remove_from_tx_queue(pInfo, R3964_OK);
  
  			pInfo->state = R3964_IDLE;
  			trigger_transmit(pInfo);
  		} else {
  			retry_transmit(pInfo);
  		}
  		break;
  	case R3964_WAIT_FOR_RX_REPEAT:

  		/* FALLTHROUGH */

  	case R3964_IDLE:
  		if (c == STX) {
  			/* Prevent rx_queue from overflow: */
  			if (pInfo->blocks_in_rx_queue >=
  			    R3964_MAX_BLOCKS_IN_RX_QUEUE) {
  				TRACE_PE("IDLE - got STX but no space in "
  						"rx_queue!");
  				pInfo->state = R3964_WAIT_FOR_RX_BUF;
  				mod_timer(&pInfo->tmr,
  					  jiffies + R3964_TO_NO_BUF);
  				break;
  			}

  start_receiving:

  			/* Ok, start receiving: */
  			TRACE_PS("IDLE - got STX");
  			pInfo->rx_position = 0;
  			pInfo->last_rx = 0;
  			pInfo->flags &= ~R3964_ERROR;
  			pInfo->state = R3964_RECEIVING;
  			mod_timer(&pInfo->tmr, jiffies + R3964_TO_ZVZ);
  			pInfo->nRetry = 0;
  			put_char(pInfo, DLE);
  			flush(pInfo);
  			pInfo->bcc = 0;
  		}
  		break;
  	case R3964_RECEIVING:
  		if (pInfo->rx_position < RX_BUF_SIZE) {
  			pInfo->bcc ^= c;
  
  			if (c == DLE) {
  				if (pInfo->last_rx == DLE) {
  					pInfo->last_rx = 0;
  					goto char_to_buf;
  				}
  				pInfo->last_rx = DLE;
  				break;
  			} else if ((c == ETX) && (pInfo->last_rx == DLE)) {
  				if (pInfo->flags & R3964_BCC) {
  					pInfo->state = R3964_WAIT_FOR_BCC;
  					mod_timer(&pInfo->tmr,
  						  jiffies + R3964_TO_ZVZ);
  				} else {
  					on_receive_block(pInfo);
  				}
  			} else {
  				pInfo->last_rx = c;

  char_to_buf:

  				pInfo->rx_buf[pInfo->rx_position++] = c;
  				mod_timer(&pInfo->tmr, jiffies + R3964_TO_ZVZ);
  			}
  		}
  		/* else: overflow-msg? BUF_SIZE>MTU; should not happen? */
  		break;
  	case R3964_WAIT_FOR_BCC:
  		pInfo->last_rx = c;
  		on_receive_block(pInfo);
  		break;
  	}

  }
  
  static void receive_error(struct r3964_info *pInfo, const char flag)
  {

  	switch (flag) {
  	case TTY_NORMAL:
  		break;
  	case TTY_BREAK:
  		TRACE_PE("received break");
  		pInfo->flags |= R3964_BREAK;
  		break;
  	case TTY_PARITY:
  		TRACE_PE("parity error");
  		pInfo->flags |= R3964_PARITY;
  		break;
  	case TTY_FRAME:
  		TRACE_PE("frame error");
  		pInfo->flags |= R3964_FRAME;
  		break;
  	case TTY_OVERRUN:
  		TRACE_PE("frame overrun");
  		pInfo->flags |= R3964_OVERRUN;
  		break;
  	default:
  		TRACE_PE("receive_error - unknown flag %d", flag);
  		pInfo->flags |= R3964_UNKNOWN;
  		break;
  	}

  }
  
  static void on_timeout(unsigned long priv)
  {

  	struct r3964_info *pInfo = (void *)priv;
  
  	switch (pInfo->state) {
  	case R3964_TX_REQUEST:
  		TRACE_PE("TX_REQUEST - timeout");
  		retry_transmit(pInfo);
  		break;
  	case R3964_WAIT_ZVZ_BEFORE_TX_RETRY:
  		put_char(pInfo, NAK);
  		flush(pInfo);
  		retry_transmit(pInfo);
  		break;
  	case R3964_WAIT_FOR_TX_ACK:
  		TRACE_PE("WAIT_FOR_TX_ACK - timeout");
  		retry_transmit(pInfo);
  		break;
  	case R3964_WAIT_FOR_RX_BUF:
  		TRACE_PE("WAIT_FOR_RX_BUF - timeout");
  		put_char(pInfo, NAK);
  		flush(pInfo);
  		pInfo->state = R3964_IDLE;
  		break;
  	case R3964_RECEIVING:
  		TRACE_PE("RECEIVING - timeout after %d chars",
  			 pInfo->rx_position);
  		put_char(pInfo, NAK);
  		flush(pInfo);
  		pInfo->state = R3964_IDLE;
  		break;
  	case R3964_WAIT_FOR_RX_REPEAT:
  		TRACE_PE("WAIT_FOR_RX_REPEAT - timeout");
  		pInfo->state = R3964_IDLE;
  		break;
  	case R3964_WAIT_FOR_BCC:
  		TRACE_PE("WAIT_FOR_BCC - timeout");
  		put_char(pInfo, NAK);
  		flush(pInfo);
  		pInfo->state = R3964_IDLE;
  		break;
  	}

  }

  static struct r3964_client_info *findClient(struct r3964_info *pInfo,
  		struct pid *pid)

  {

  	struct r3964_client_info *pClient;
  
  	for (pClient = pInfo->firstClient; pClient; pClient = pClient->next) {
  		if (pClient->pid == pid) {
  			return pClient;
  		}
  	}
  	return NULL;

  }

  static int enable_signals(struct r3964_info *pInfo, struct pid *pid, int arg)

  {

  	struct r3964_client_info *pClient;
  	struct r3964_client_info **ppClient;
  	struct r3964_message *pMsg;
  
  	if ((arg & R3964_SIG_ALL) == 0) {
  		/* Remove client from client list */
  		for (ppClient = &pInfo->firstClient; *ppClient;
  		     ppClient = &(*ppClient)->next) {
  			pClient = *ppClient;
  
  			if (pClient->pid == pid) {
  				TRACE_PS("removing client %d from client list",
  					 pid_nr(pid));
  				*ppClient = pClient->next;
  				while (pClient->msg_count) {
  					pMsg = remove_msg(pInfo, pClient);
  					if (pMsg) {
  						kfree(pMsg);
  						TRACE_M("enable_signals - msg "
  							"kfree %p", pMsg);
  					}
  				}
  				put_pid(pClient->pid);
  				kfree(pClient);
  				TRACE_M("enable_signals - kfree %p", pClient);
  				return 0;
  			}
  		}
  		return -EINVAL;
  	} else {
  		pClient = findClient(pInfo, pid);
  		if (pClient) {
  			/* update signal options */
  			pClient->sig_flags = arg;
  		} else {
  			/* add client to client list */
  			pClient = kmalloc(sizeof(struct r3964_client_info),
  					GFP_KERNEL);
  			TRACE_M("enable_signals - kmalloc %p", pClient);
  			if (pClient == NULL)
  				return -ENOMEM;
  
  			TRACE_PS("add client %d to client list", pid_nr(pid));
  			spin_lock_init(&pClient->lock);
  			pClient->sig_flags = arg;
  			pClient->pid = get_pid(pid);
  			pClient->next = pInfo->firstClient;
  			pClient->first_msg = NULL;
  			pClient->last_msg = NULL;
  			pClient->next_block_to_read = NULL;
  			pClient->msg_count = 0;
  			pInfo->firstClient = pClient;
  		}
  	}
  
  	return 0;

  }

  static int read_telegram(struct r3964_info *pInfo, struct pid *pid,
  			 unsigned char __user * buf)

  {

  	struct r3964_client_info *pClient;
  	struct r3964_block_header *block;
  
  	if (!buf) {
  		return -EINVAL;
  	}
  
  	pClient = findClient(pInfo, pid);
  	if (pClient == NULL) {
  		return -EINVAL;
  	}
  
  	block = pClient->next_block_to_read;
  	if (!block) {
  		return 0;
  	} else {
  		if (copy_to_user(buf, block->data, block->length))
  			return -EFAULT;
  
  		remove_client_block(pInfo, pClient);
  		return block->length;
  	}
  
  	return -EINVAL;

  }
  
  static void add_msg(struct r3964_client_info *pClient, int msg_id, int arg,

  		int error_code, struct r3964_block_header *pBlock)

  {

  	struct r3964_message *pMsg;
  	unsigned long flags;
  
  	if (pClient->msg_count < R3964_MAX_MSG_COUNT - 1) {

  queue_the_message:

  		pMsg = kmalloc(sizeof(struct r3964_message),
  				error_code ? GFP_ATOMIC : GFP_KERNEL);
  		TRACE_M("add_msg - kmalloc %p", pMsg);
  		if (pMsg == NULL) {
  			return;
  		}
  
  		spin_lock_irqsave(&pClient->lock, flags);
  
  		pMsg->msg_id = msg_id;
  		pMsg->arg = arg;
  		pMsg->error_code = error_code;
  		pMsg->block = pBlock;
  		pMsg->next = NULL;
  
  		if (pClient->last_msg == NULL) {
  			pClient->first_msg = pClient->last_msg = pMsg;
  		} else {
  			pClient->last_msg->next = pMsg;
  			pClient->last_msg = pMsg;
  		}
  
  		pClient->msg_count++;
  
  		if (pBlock != NULL) {
  			pBlock->locks++;
  		}
  		spin_unlock_irqrestore(&pClient->lock, flags);
  	} else {
  		if ((pClient->last_msg->msg_id == R3964_MSG_ACK)
  		    && (pClient->last_msg->error_code == R3964_OVERFLOW)) {
  			pClient->last_msg->arg++;
  			TRACE_PE("add_msg - inc prev OVERFLOW-msg");
  		} else {
  			msg_id = R3964_MSG_ACK;
  			arg = 0;
  			error_code = R3964_OVERFLOW;
  			pBlock = NULL;
  			TRACE_PE("add_msg - queue OVERFLOW-msg");
  			goto queue_the_message;
  		}
  	}
  	/* Send SIGIO signal to client process: */
  	if (pClient->sig_flags & R3964_USE_SIGIO) {
  		kill_pid(pClient->pid, SIGIO, 1);
  	}

  }
  
  static struct r3964_message *remove_msg(struct r3964_info *pInfo,

  					struct r3964_client_info *pClient)

  {

  	struct r3964_message *pMsg = NULL;
  	unsigned long flags;
  
  	if (pClient->first_msg) {
  		spin_lock_irqsave(&pClient->lock, flags);
  
  		pMsg = pClient->first_msg;
  		pClient->first_msg = pMsg->next;
  		if (pClient->first_msg == NULL) {
  			pClient->last_msg = NULL;
  		}
  
  		pClient->msg_count--;
  		if (pMsg->block) {
  			remove_client_block(pInfo, pClient);
  			pClient->next_block_to_read = pMsg->block;
  		}
  		spin_unlock_irqrestore(&pClient->lock, flags);
  	}
  	return pMsg;

  }

  static void remove_client_block(struct r3964_info *pInfo,
  				struct r3964_client_info *pClient)

  {

  	struct r3964_block_header *block;
  
  	TRACE_PS("remove_client_block PID %d", pid_nr(pClient->pid));

  	block = pClient->next_block_to_read;
  	if (block) {
  		block->locks--;
  		if (block->locks == 0) {
  			remove_from_rx_queue(pInfo, block);
  		}
  	}
  	pClient->next_block_to_read = NULL;
  }

  
  /*************************************************************
   * Line discipline routines
   *************************************************************/
  
  static int r3964_open(struct tty_struct *tty)
  {

  	struct r3964_info *pInfo;
  
  	TRACE_L("open");
  	TRACE_L("tty=%p, PID=%d, disc_data=%p",
  		tty, current->pid, tty->disc_data);
  
  	pInfo = kmalloc(sizeof(struct r3964_info), GFP_KERNEL);
  	TRACE_M("r3964_open - info kmalloc %p", pInfo);
  
  	if (!pInfo) {
  		printk(KERN_ERR "r3964: failed to alloc info structure
  ");
  		return -ENOMEM;
  	}
  
  	pInfo->rx_buf = kmalloc(RX_BUF_SIZE, GFP_KERNEL);
  	TRACE_M("r3964_open - rx_buf kmalloc %p", pInfo->rx_buf);
  
  	if (!pInfo->rx_buf) {
  		printk(KERN_ERR "r3964: failed to alloc receive buffer
  ");
  		kfree(pInfo);
  		TRACE_M("r3964_open - info kfree %p", pInfo);
  		return -ENOMEM;
  	}
  
  	pInfo->tx_buf = kmalloc(TX_BUF_SIZE, GFP_KERNEL);
  	TRACE_M("r3964_open - tx_buf kmalloc %p", pInfo->tx_buf);
  
  	if (!pInfo->tx_buf) {
  		printk(KERN_ERR "r3964: failed to alloc transmit buffer
  ");
  		kfree(pInfo->rx_buf);
  		TRACE_M("r3964_open - rx_buf kfree %p", pInfo->rx_buf);
  		kfree(pInfo);
  		TRACE_M("r3964_open - info kfree %p", pInfo);
  		return -ENOMEM;
  	}
  
  	spin_lock_init(&pInfo->lock);
  	pInfo->tty = tty;
  	init_waitqueue_head(&pInfo->read_wait);
  	pInfo->priority = R3964_MASTER;
  	pInfo->rx_first = pInfo->rx_last = NULL;
  	pInfo->tx_first = pInfo->tx_last = NULL;
  	pInfo->rx_position = 0;
  	pInfo->tx_position = 0;
  	pInfo->last_rx = 0;
  	pInfo->blocks_in_rx_queue = 0;
  	pInfo->firstClient = NULL;
  	pInfo->state = R3964_IDLE;
  	pInfo->flags = R3964_DEBUG;
  	pInfo->nRetry = 0;
  
  	tty->disc_data = pInfo;
  	tty->receive_room = 65536;

  	setup_timer(&pInfo->tmr, on_timeout, (unsigned long)pInfo);

  
  	return 0;

  }
  
  static void r3964_close(struct tty_struct *tty)
  {

  	struct r3964_info *pInfo = tty->disc_data;

  	struct r3964_client_info *pClient, *pNext;
  	struct r3964_message *pMsg;
  	struct r3964_block_header *pHeader, *pNextHeader;
  	unsigned long flags;
  
  	TRACE_L("close");
  
  	/*
  	 * Make sure that our task queue isn't activated.  If it
  	 * is, take it out of the linked list.
  	 */
  	del_timer_sync(&pInfo->tmr);
  
  	/* Remove client-structs and message queues: */
  	pClient = pInfo->firstClient;
  	while (pClient) {
  		pNext = pClient->next;
  		while (pClient->msg_count) {
  			pMsg = remove_msg(pInfo, pClient);
  			if (pMsg) {
  				kfree(pMsg);
  				TRACE_M("r3964_close - msg kfree %p", pMsg);
  			}
  		}
  		put_pid(pClient->pid);
  		kfree(pClient);
  		TRACE_M("r3964_close - client kfree %p", pClient);
  		pClient = pNext;
  	}
  	/* Remove jobs from tx_queue: */
  	spin_lock_irqsave(&pInfo->lock, flags);
  	pHeader = pInfo->tx_first;
  	pInfo->tx_first = pInfo->tx_last = NULL;

  	spin_unlock_irqrestore(&pInfo->lock, flags);

  
  	while (pHeader) {
  		pNextHeader = pHeader->next;
  		kfree(pHeader);
  		pHeader = pNextHeader;

  	}

  	/* Free buffers: */
  	wake_up_interruptible(&pInfo->read_wait);
  	kfree(pInfo->rx_buf);
  	TRACE_M("r3964_close - rx_buf kfree %p", pInfo->rx_buf);
  	kfree(pInfo->tx_buf);
  	TRACE_M("r3964_close - tx_buf kfree %p", pInfo->tx_buf);
  	kfree(pInfo);
  	TRACE_M("r3964_close - info kfree %p", pInfo);

  }
  
  static ssize_t r3964_read(struct tty_struct *tty, struct file *file,

  			  unsigned char __user * buf, size_t nr)

  {

  	struct r3964_info *pInfo = tty->disc_data;

  	struct r3964_client_info *pClient;
  	struct r3964_message *pMsg;
  	struct r3964_client_message theMsg;

  	int ret;

  
  	TRACE_L("read()");

  	tty_lock();

  	pClient = findClient(pInfo, task_pid(current));
  	if (pClient) {
  		pMsg = remove_msg(pInfo, pClient);
  		if (pMsg == NULL) {
  			/* no messages available. */
  			if (file->f_flags & O_NONBLOCK) {

  				ret = -EAGAIN;
  				goto unlock;

  			}
  			/* block until there is a message: */

  			wait_event_interruptible_tty(pInfo->read_wait,

  					(pMsg = remove_msg(pInfo, pClient)));

  		}
  
  		/* If we still haven't got a message, we must have been signalled */

  		if (!pMsg) {

  			ret = -EINTR;
  			goto unlock;

  		}

  
  		/* deliver msg to client process: */
  		theMsg.msg_id = pMsg->msg_id;
  		theMsg.arg = pMsg->arg;
  		theMsg.error_code = pMsg->error_code;

  		ret = sizeof(struct r3964_client_message);

  
  		kfree(pMsg);
  		TRACE_M("r3964_read - msg kfree %p", pMsg);

  		if (copy_to_user(buf, &theMsg, ret)) {
  			ret = -EFAULT;
  			goto unlock;

  		}

  		TRACE_PS("read - return %d", ret);
  		goto unlock;

  	}

  	ret = -EPERM;
  unlock:

  	tty_unlock();

  	return ret;

  }

  static ssize_t r3964_write(struct tty_struct *tty, struct file *file,

  			   const unsigned char *data, size_t count)
  {

  	struct r3964_info *pInfo = tty->disc_data;

  	struct r3964_block_header *pHeader;
  	struct r3964_client_info *pClient;
  	unsigned char *new_data;
  
  	TRACE_L("write request, %d characters", count);

  /* 
   * Verify the pointers 
   */

  	if (!pInfo)
  		return -EIO;

  
  /*
   * Ensure that the caller does not wish to send too much.
   */

  	if (count > R3964_MTU) {
  		if (pInfo->flags & R3964_DEBUG) {
  			TRACE_L(KERN_WARNING "r3964_write: truncating user "
  				"packet from %u to mtu %d", count, R3964_MTU);
  		}
  		count = R3964_MTU;
  	}

  /*
   * Allocate a buffer for the data and copy it from the buffer with header prepended
   */

  	new_data = kmalloc(count + sizeof(struct r3964_block_header),
  			GFP_KERNEL);
  	TRACE_M("r3964_write - kmalloc %p", new_data);
  	if (new_data == NULL) {
  		if (pInfo->flags & R3964_DEBUG) {
  			printk(KERN_ERR "r3964_write: no memory
  ");
  		}
  		return -ENOSPC;
  	}
  
  	pHeader = (struct r3964_block_header *)new_data;
  	pHeader->data = new_data + sizeof(struct r3964_block_header);
  	pHeader->length = count;
  	pHeader->locks = 0;
  	pHeader->owner = NULL;

  	tty_lock();

  	pClient = findClient(pInfo, task_pid(current));
  	if (pClient) {
  		pHeader->owner = pClient;
  	}
  
  	memcpy(pHeader->data, data, count);	/* We already verified this */
  
  	if (pInfo->flags & R3964_DEBUG) {
  		dump_block(pHeader->data, count);
  	}

  
  /*
   * Add buffer to transmit-queue:
   */

  	add_tx_queue(pInfo, pHeader);
  	trigger_transmit(pInfo);

  	tty_unlock();

  	return 0;

  }

  static int r3964_ioctl(struct tty_struct *tty, struct file *file,
  		unsigned int cmd, unsigned long arg)

  {

  	struct r3964_info *pInfo = tty->disc_data;

  	if (pInfo == NULL)
  		return -EINVAL;
  	switch (cmd) {
  	case R3964_ENABLE_SIGNALS:
  		return enable_signals(pInfo, task_pid(current), arg);
  	case R3964_SETPRIORITY:
  		if (arg < R3964_MASTER || arg > R3964_SLAVE)
  			return -EINVAL;
  		pInfo->priority = arg & 0xff;
  		return 0;
  	case R3964_USE_BCC:
  		if (arg)
  			pInfo->flags |= R3964_BCC;
  		else
  			pInfo->flags &= ~R3964_BCC;
  		return 0;
  	case R3964_READ_TELEGRAM:
  		return read_telegram(pInfo, task_pid(current),
  				(unsigned char __user *)arg);
  	default:
  		return -ENOIOCTLCMD;
  	}

  }

  static void r3964_set_termios(struct tty_struct *tty, struct ktermios *old)

  {

  	TRACE_L("set_termios");

  }
  
  /* Called without the kernel lock held - fine */

  static unsigned int r3964_poll(struct tty_struct *tty, struct file *file,
  			struct poll_table_struct *wait)

  {

  	struct r3964_info *pInfo = tty->disc_data;

  	struct r3964_client_info *pClient;
  	struct r3964_message *pMsg = NULL;
  	unsigned long flags;
  	int result = POLLOUT;
  
  	TRACE_L("POLL");
  
  	pClient = findClient(pInfo, task_pid(current));
  	if (pClient) {
  		poll_wait(file, &pInfo->read_wait, wait);
  		spin_lock_irqsave(&pInfo->lock, flags);
  		pMsg = pClient->first_msg;
  		spin_unlock_irqrestore(&pInfo->lock, flags);
  		if (pMsg)
  			result |= POLLIN | POLLRDNORM;
  	} else {
  		result = -EINVAL;
  	}
  	return result;

  }

  static void r3964_receive_buf(struct tty_struct *tty, const unsigned char *cp,
  			char *fp, int count)

  {

  	struct r3964_info *pInfo = tty->disc_data;

  	const unsigned char *p;
  	char *f, flags = 0;
  	int i;
  
  	for (i = count, p = cp, f = fp; i; i--, p++) {
  		if (f)
  			flags = *f++;
  		if (flags == TTY_NORMAL) {
  			receive_char(pInfo, *p);
  		} else {
  			receive_error(pInfo, flags);
  		}
  
  	}

  }

  MODULE_LICENSE("GPL");
  MODULE_ALIAS_LDISC(N_R3964);