/* This is the serial hardware link layer (HLL) for the Gigaset 307x isdn
   * DECT base (aka Sinus 45 isdn) using the RS232 DECT data module M101,
   * written as a line discipline.
   *
   * =====================================================================
   * This program 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.
   * =====================================================================
   */
  
  #include "gigaset.h"
  #include <linux/module.h>
  #include <linux/moduleparam.h>
  #include <linux/platform_device.h>
  #include <linux/completion.h>
  
  /* Version Information */
  #define DRIVER_AUTHOR "Tilman Schmidt"
  #define DRIVER_DESC "Serial Driver for Gigaset 307x using Siemens M101"
  
  #define GIGASET_MINORS     1
  #define GIGASET_MINOR      0
  #define GIGASET_MODULENAME "ser_gigaset"
  #define GIGASET_DEVNAME    "ttyGS"
  
  /* length limit according to Siemens 3070usb-protokoll.doc ch. 2.1 */
  #define IF_WRITEBUF 264
  
  MODULE_AUTHOR(DRIVER_AUTHOR);
  MODULE_DESCRIPTION(DRIVER_DESC);
  MODULE_LICENSE("GPL");
  MODULE_ALIAS_LDISC(N_GIGASET_M101);
  
  static int startmode = SM_ISDN;
  module_param(startmode, int, S_IRUGO);
  MODULE_PARM_DESC(startmode, "initial operation mode");
  static int cidmode = 1;
  module_param(cidmode, int, S_IRUGO);
  MODULE_PARM_DESC(cidmode, "stay in CID mode when idle");
  
  static struct gigaset_driver *driver;
  
  struct ser_cardstate {
  	struct platform_device	dev;
  	struct tty_struct	*tty;
  	atomic_t		refcnt;
  	struct completion	dead_cmp;
  };
  
  static struct platform_driver device_driver = {
  	.driver = {
  		.name = GIGASET_MODULENAME,
  	},
  };
  
  static void flush_send_queue(struct cardstate *);
  
  /* transmit data from current open skb
   * result: number of bytes sent or error code < 0
   */
  static int write_modem(struct cardstate *cs)
  {
  	struct tty_struct *tty = cs->hw.ser->tty;
  	struct bc_state *bcs = &cs->bcs[0];	/* only one channel */
  	struct sk_buff *skb = bcs->tx_skb;
  	int sent = -EOPNOTSUPP;
  
  	if (!tty || !tty->driver || !skb)
  		return -EINVAL;
  
  	if (!skb->len) {
  		dev_kfree_skb_any(skb);
  		bcs->tx_skb = NULL;
  		return -EINVAL;
  	}
  
  	set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
  	if (tty->ops->write)
  		sent = tty->ops->write(tty, skb->data, skb->len);
  	gig_dbg(DEBUG_OUTPUT, "write_modem: sent %d", sent);
  	if (sent < 0) {
  		/* error */
  		flush_send_queue(cs);
  		return sent;
  	}
  	skb_pull(skb, sent);
  	if (!skb->len) {
  		/* skb sent completely */
  		gigaset_skb_sent(bcs, skb);
  
  		gig_dbg(DEBUG_INTR, "kfree skb (Adr: %lx)!",
  			(unsigned long) skb);
  		dev_kfree_skb_any(skb);
  		bcs->tx_skb = NULL;
  	}
  	return sent;
  }
  
  /*
   * transmit first queued command buffer
   * result: number of bytes sent or error code < 0
   */
  static int send_cb(struct cardstate *cs)
  {
  	struct tty_struct *tty = cs->hw.ser->tty;
  	struct cmdbuf_t *cb, *tcb;
  	unsigned long flags;
  	int sent = 0;
  
  	if (!tty || !tty->driver)
  		return -EFAULT;
  
  	cb = cs->cmdbuf;
  	if (!cb)
  		return 0;	/* nothing to do */
  
  	if (cb->len) {
  		set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
  		sent = tty->ops->write(tty, cb->buf + cb->offset, cb->len);
  		if (sent < 0) {
  			/* error */
  			gig_dbg(DEBUG_OUTPUT, "send_cb: write error %d", sent);
  			flush_send_queue(cs);
  			return sent;
  		}
  		cb->offset += sent;
  		cb->len -= sent;
  		gig_dbg(DEBUG_OUTPUT, "send_cb: sent %d, left %u, queued %u",
  			sent, cb->len, cs->cmdbytes);
  	}
  
  	while (cb && !cb->len) {
  		spin_lock_irqsave(&cs->cmdlock, flags);
  		cs->cmdbytes -= cs->curlen;
  		tcb = cb;
  		cs->cmdbuf = cb = cb->next;
  		if (cb) {
  			cb->prev = NULL;
  			cs->curlen = cb->len;
  		} else {
  			cs->lastcmdbuf = NULL;
  			cs->curlen = 0;
  		}
  		spin_unlock_irqrestore(&cs->cmdlock, flags);
  
  		if (tcb->wake_tasklet)
  			tasklet_schedule(tcb->wake_tasklet);
  		kfree(tcb);
  	}
  	return sent;
  }
  
  /*
   * send queue tasklet
   * If there is already a skb opened, put data to the transfer buffer
   * by calling "write_modem".
   * Otherwise take a new skb out of the queue.
   */
  static void gigaset_modem_fill(unsigned long data)
  {
  	struct cardstate *cs = (struct cardstate *) data;
  	struct bc_state *bcs;
  	struct sk_buff *nextskb;
  	int sent = 0;
  
  	if (!cs) {
  		gig_dbg(DEBUG_OUTPUT, "%s: no cardstate", __func__);
  		return;
  	}
  	bcs = cs->bcs;
  	if (!bcs) {
  		gig_dbg(DEBUG_OUTPUT, "%s: no cardstate", __func__);
  		return;
  	}
  	if (!bcs->tx_skb) {
  		/* no skb is being sent; send command if any */
  		sent = send_cb(cs);
  		gig_dbg(DEBUG_OUTPUT, "%s: send_cb -> %d", __func__, sent);
  		if (sent)
  			/* something sent or error */
  			return;
  
  		/* no command to send; get skb */
  		nextskb = skb_dequeue(&bcs->squeue);
  		if (!nextskb)
  			/* no skb either, nothing to do */
  			return;
  		bcs->tx_skb = nextskb;
  
  		gig_dbg(DEBUG_INTR, "Dequeued skb (Adr: %lx)",
  			(unsigned long) bcs->tx_skb);
  	}
  
  	/* send skb */
  	gig_dbg(DEBUG_OUTPUT, "%s: tx_skb", __func__);
  	if (write_modem(cs) < 0)
  		gig_dbg(DEBUG_OUTPUT, "%s: write_modem failed", __func__);
  }
  
  /*
   * throw away all data queued for sending
   */
  static void flush_send_queue(struct cardstate *cs)
  {
  	struct sk_buff *skb;
  	struct cmdbuf_t *cb;
  	unsigned long flags;
  
  	/* command queue */
  	spin_lock_irqsave(&cs->cmdlock, flags);
  	while ((cb = cs->cmdbuf) != NULL) {
  		cs->cmdbuf = cb->next;
  		if (cb->wake_tasklet)
  			tasklet_schedule(cb->wake_tasklet);
  		kfree(cb);
  	}
  	cs->cmdbuf = cs->lastcmdbuf = NULL;
  	cs->cmdbytes = cs->curlen = 0;
  	spin_unlock_irqrestore(&cs->cmdlock, flags);
  
  	/* data queue */
  	if (cs->bcs->tx_skb)
  		dev_kfree_skb_any(cs->bcs->tx_skb);
  	while ((skb = skb_dequeue(&cs->bcs->squeue)) != NULL)
  		dev_kfree_skb_any(skb);
  }
  
  
  /* Gigaset Driver Interface */
  /* ======================== */
  
  /*
   * queue an AT command string for transmission to the Gigaset device
   * parameters:
   *	cs		controller state structure
   *	buf		buffer containing the string to send
   *	len		number of characters to send
   *	wake_tasklet	tasklet to run when transmission is complete, or NULL
   * return value:
   *	number of bytes queued, or error code < 0
   */
  static int gigaset_write_cmd(struct cardstate *cs, struct cmdbuf_t *cb)
  {
  	unsigned long flags;
  
  	gigaset_dbg_buffer(cs->mstate != MS_LOCKED ?
  			   DEBUG_TRANSCMD : DEBUG_LOCKCMD,
  			   "CMD Transmit", cb->len, cb->buf);
  
  	spin_lock_irqsave(&cs->cmdlock, flags);
  	cb->prev = cs->lastcmdbuf;
  	if (cs->lastcmdbuf)
  		cs->lastcmdbuf->next = cb;
  	else {
  		cs->cmdbuf = cb;
  		cs->curlen = cb->len;
  	}
  	cs->cmdbytes += cb->len;
  	cs->lastcmdbuf = cb;
  	spin_unlock_irqrestore(&cs->cmdlock, flags);
  
  	spin_lock_irqsave(&cs->lock, flags);
  	if (cs->connected)
  		tasklet_schedule(&cs->write_tasklet);
  	spin_unlock_irqrestore(&cs->lock, flags);
  	return cb->len;
  }
  
  /*
   * tty_driver.write_room interface routine
   * return number of characters the driver will accept to be written
   * parameter:
   *	controller state structure
   * return value:
   *	number of characters
   */
  static int gigaset_write_room(struct cardstate *cs)
  {
  	unsigned bytes;
  
  	bytes = cs->cmdbytes;
  	return bytes < IF_WRITEBUF ? IF_WRITEBUF - bytes : 0;
  }
  
  /*
   * tty_driver.chars_in_buffer interface routine
   * return number of characters waiting to be sent
   * parameter:
   *	controller state structure
   * return value:
   *	number of characters
   */
  static int gigaset_chars_in_buffer(struct cardstate *cs)
  {
  	return cs->cmdbytes;
  }
  
  /*
   * implementation of ioctl(GIGASET_BRKCHARS)
   * parameter:
   *	controller state structure
   * return value:
   *	-EINVAL (unimplemented function)
   */
  static int gigaset_brkchars(struct cardstate *cs, const unsigned char buf[6])
  {
  	/* not implemented */
  	return -EINVAL;
  }
  
  /*
   * Open B channel
   * Called by "do_action" in ev-layer.c
   */
  static int gigaset_init_bchannel(struct bc_state *bcs)
  {
  	/* nothing to do for M10x */
  	gigaset_bchannel_up(bcs);
  	return 0;
  }
  
  /*
   * Close B channel
   * Called by "do_action" in ev-layer.c
   */
  static int gigaset_close_bchannel(struct bc_state *bcs)
  {
  	/* nothing to do for M10x */
  	gigaset_bchannel_down(bcs);
  	return 0;
  }
  
  /*
   * Set up B channel structure
   * This is called by "gigaset_initcs" in common.c
   */
  static int gigaset_initbcshw(struct bc_state *bcs)
  {
  	/* unused */
  	bcs->hw.ser = NULL;
  	return 0;
  }
  
  /*
   * Free B channel structure
   * Called by "gigaset_freebcs" in common.c
   */
  static void gigaset_freebcshw(struct bc_state *bcs)
  {
  	/* unused */
  }
  
  /*
   * Reinitialize B channel structure
   * This is called by "bcs_reinit" in common.c
   */
  static void gigaset_reinitbcshw(struct bc_state *bcs)
  {
  	/* nothing to do for M10x */
  }
  
  /*
   * Free hardware specific device data
   * This will be called by "gigaset_freecs" in common.c
   */
  static void gigaset_freecshw(struct cardstate *cs)
  {
  	tasklet_kill(&cs->write_tasklet);
  	if (!cs->hw.ser)
  		return;
  	dev_set_drvdata(&cs->hw.ser->dev.dev, NULL);
  	platform_device_unregister(&cs->hw.ser->dev);
  	kfree(cs->hw.ser);
  	cs->hw.ser = NULL;
  }
  
  static void gigaset_device_release(struct device *dev)
  {
  	struct platform_device *pdev = to_platform_device(dev);
  
  	/* adapted from platform_device_release() in drivers/base/platform.c */
  	kfree(dev->platform_data);
  	kfree(pdev->resource);
  }
  
  /*
   * Set up hardware specific device data
   * This is called by "gigaset_initcs" in common.c
   */
  static int gigaset_initcshw(struct cardstate *cs)
  {
  	int rc;
  	struct ser_cardstate *scs;
  
  	scs = kzalloc(sizeof(struct ser_cardstate), GFP_KERNEL);
  	if (!scs) {
  		pr_err("out of memory
  ");
  		return -ENOMEM;
  	}
  	cs->hw.ser = scs;
  
  	cs->hw.ser->dev.name = GIGASET_MODULENAME;
  	cs->hw.ser->dev.id = cs->minor_index;
  	cs->hw.ser->dev.dev.release = gigaset_device_release;
  	rc = platform_device_register(&cs->hw.ser->dev);
  	if (rc != 0) {
  		pr_err("error %d registering platform device
  ", rc);
  		kfree(cs->hw.ser);
  		cs->hw.ser = NULL;
  		return rc;
  	}
  	dev_set_drvdata(&cs->hw.ser->dev.dev, cs);
  
  	tasklet_init(&cs->write_tasklet,
  		     gigaset_modem_fill, (unsigned long) cs);
  	return 0;
  }
  
  /*
   * set modem control lines
   * Parameters:
   *	card state structure
   *	modem control line state ([TIOCM_DTR]|[TIOCM_RTS])
   * Called by "gigaset_start" and "gigaset_enterconfigmode" in common.c
   * and by "if_lock" and "if_termios" in interface.c
   */
  static int gigaset_set_modem_ctrl(struct cardstate *cs, unsigned old_state,
  				  unsigned new_state)
  {
  	struct tty_struct *tty = cs->hw.ser->tty;
  	unsigned int set, clear;
  
  	if (!tty || !tty->driver || !tty->ops->tiocmset)
  		return -EINVAL;
  	set = new_state & ~old_state;
  	clear = old_state & ~new_state;
  	if (!set && !clear)
  		return 0;
  	gig_dbg(DEBUG_IF, "tiocmset set %x clear %x", set, clear);
  	return tty->ops->tiocmset(tty, set, clear);
  }
  
  static int gigaset_baud_rate(struct cardstate *cs, unsigned cflag)
  {
  	return -EINVAL;
  }
  
  static int gigaset_set_line_ctrl(struct cardstate *cs, unsigned cflag)
  {
  	return -EINVAL;
  }
  
  static const struct gigaset_ops ops = {
  	gigaset_write_cmd,
  	gigaset_write_room,
  	gigaset_chars_in_buffer,
  	gigaset_brkchars,
  	gigaset_init_bchannel,
  	gigaset_close_bchannel,
  	gigaset_initbcshw,
  	gigaset_freebcshw,
  	gigaset_reinitbcshw,
  	gigaset_initcshw,
  	gigaset_freecshw,
  	gigaset_set_modem_ctrl,
  	gigaset_baud_rate,
  	gigaset_set_line_ctrl,
  	gigaset_m10x_send_skb,	/* asyncdata.c */
  	gigaset_m10x_input,	/* asyncdata.c */
  };
  
  
  /* Line Discipline Interface */
  /* ========================= */
  
  /* helper functions for cardstate refcounting */
  static struct cardstate *cs_get(struct tty_struct *tty)
  {
  	struct cardstate *cs = tty->disc_data;
  
  	if (!cs || !cs->hw.ser) {
  		gig_dbg(DEBUG_ANY, "%s: no cardstate", __func__);
  		return NULL;
  	}
  	atomic_inc(&cs->hw.ser->refcnt);
  	return cs;
  }
  
  static void cs_put(struct cardstate *cs)
  {
  	if (atomic_dec_and_test(&cs->hw.ser->refcnt))
  		complete(&cs->hw.ser->dead_cmp);
  }
  
  /*
   * Called by the tty driver when the line discipline is pushed onto the tty.
   * Called in process context.
   */
  static int
  gigaset_tty_open(struct tty_struct *tty)
  {
  	struct cardstate *cs;
  	int rc;
  
  	gig_dbg(DEBUG_INIT, "Starting HLL for Gigaset M101");
  
  	pr_info(DRIVER_DESC "
  ");
  
  	if (!driver) {
  		pr_err("%s: no driver structure
  ", __func__);
  		return -ENODEV;
  	}
  
  	/* allocate memory for our device state and initialize it */
  	cs = gigaset_initcs(driver, 1, 1, 0, cidmode, GIGASET_MODULENAME);
  	if (!cs) {
  		rc = -ENODEV;
  		goto error;
  	}
  
  	cs->dev = &cs->hw.ser->dev.dev;
  	cs->hw.ser->tty = tty;
  	atomic_set(&cs->hw.ser->refcnt, 1);
  	init_completion(&cs->hw.ser->dead_cmp);
  
  	tty->disc_data = cs;
  
  	/* OK.. Initialization of the datastructures and the HW is done.. Now
  	 * startup system and notify the LL that we are ready to run
  	 */
  	if (startmode == SM_LOCKED)
  		cs->mstate = MS_LOCKED;
  	rc = gigaset_start(cs);
  	if (rc < 0) {
  		tasklet_kill(&cs->write_tasklet);
  		goto error;
  	}
  
  	gig_dbg(DEBUG_INIT, "Startup of HLL done");
  	return 0;
  
  error:
  	gig_dbg(DEBUG_INIT, "Startup of HLL failed");
  	tty->disc_data = NULL;
  	gigaset_freecs(cs);
  	return rc;
  }
  
  /*
   * Called by the tty driver when the line discipline is removed.
   * Called from process context.
   */
  static void
  gigaset_tty_close(struct tty_struct *tty)
  {
  	struct cardstate *cs = tty->disc_data;
  
  	gig_dbg(DEBUG_INIT, "Stopping HLL for Gigaset M101");
  
  	if (!cs) {
  		gig_dbg(DEBUG_INIT, "%s: no cardstate", __func__);
  		return;
  	}
  
  	/* prevent other callers from entering ldisc methods */
  	tty->disc_data = NULL;
  
  	if (!cs->hw.ser)
  		pr_err("%s: no hw cardstate
  ", __func__);
  	else {
  		/* wait for running methods to finish */
  		if (!atomic_dec_and_test(&cs->hw.ser->refcnt))
  			wait_for_completion(&cs->hw.ser->dead_cmp);
  	}
  
  	/* stop operations */
  	gigaset_stop(cs);
  	tasklet_kill(&cs->write_tasklet);
  	flush_send_queue(cs);
  	cs->dev = NULL;
  	gigaset_freecs(cs);
  
  	gig_dbg(DEBUG_INIT, "Shutdown of HLL done");
  }
  
  /*
   * Called by the tty driver when the tty line is hung up.
   * Wait for I/O to driver to complete and unregister ISDN device.
   * This is already done by the close routine, so just call that.
   * Called from process context.
   */
  static int gigaset_tty_hangup(struct tty_struct *tty)
  {
  	gigaset_tty_close(tty);
  	return 0;
  }
  
  /*
   * Read on the tty.
   * Unused, received data goes only to the Gigaset driver.
   */
  static ssize_t
  gigaset_tty_read(struct tty_struct *tty, struct file *file,
  		 unsigned char __user *buf, size_t count)
  {
  	return -EAGAIN;
  }
  
  /*
   * Write on the tty.
   * Unused, transmit data comes only from the Gigaset driver.
   */
  static ssize_t
  gigaset_tty_write(struct tty_struct *tty, struct file *file,
  		  const unsigned char *buf, size_t count)
  {
  	return -EAGAIN;
  }
  
  /*
   * Ioctl on the tty.
   * Called in process context only.
   * May be re-entered by multiple ioctl calling threads.
   */
  static int
  gigaset_tty_ioctl(struct tty_struct *tty, struct file *file,
  		  unsigned int cmd, unsigned long arg)
  {
  	struct cardstate *cs = cs_get(tty);
  	int rc, val;
  	int __user *p = (int __user *)arg;
  
  	if (!cs)
  		return -ENXIO;
  
  	switch (cmd) {
  
  	case FIONREAD:
  		/* unused, always return zero */
  		val = 0;
  		rc = put_user(val, p);
  		break;
  
  	case TCFLSH:
  		/* flush our buffers and the serial port's buffer */
  		switch (arg) {
  		case TCIFLUSH:
  			/* no own input buffer to flush */
  			break;
  		case TCIOFLUSH:
  		case TCOFLUSH:
  			flush_send_queue(cs);
  			break;
  		}
  		/* Pass through */
  
  	default:
  		/* pass through to underlying serial device */
  		rc = n_tty_ioctl_helper(tty, file, cmd, arg);
  		break;
  	}
  	cs_put(cs);
  	return rc;
  }
  
  /*
   * Called by the tty driver when a block of data has been received.
   * Will not be re-entered while running but other ldisc functions
   * may be called in parallel.
   * Can be called from hard interrupt level as well as soft interrupt
   * level or mainline.
   * Parameters:
   *	tty	tty structure
   *	buf	buffer containing received characters
   *	cflags	buffer containing error flags for received characters (ignored)
   *	count	number of received characters
   */
  static void
  gigaset_tty_receive(struct tty_struct *tty, const unsigned char *buf,
  		    char *cflags, int count)
  {
  	struct cardstate *cs = cs_get(tty);
  	unsigned tail, head, n;
  	struct inbuf_t *inbuf;
  
  	if (!cs)
  		return;
  	inbuf = cs->inbuf;
  	if (!inbuf) {
  		dev_err(cs->dev, "%s: no inbuf
  ", __func__);
  		cs_put(cs);
  		return;
  	}
  
  	tail = inbuf->tail;
  	head = inbuf->head;
  	gig_dbg(DEBUG_INTR, "buffer state: %u -> %u, receive %u bytes",
  		head, tail, count);
  
  	if (head <= tail) {
  		/* possible buffer wraparound */
  		n = min_t(unsigned, count, RBUFSIZE - tail);
  		memcpy(inbuf->data + tail, buf, n);
  		tail = (tail + n) % RBUFSIZE;
  		buf += n;
  		count -= n;
  	}
  
  	if (count > 0) {
  		/* tail < head and some data left */
  		n = head - tail - 1;
  		if (count > n) {
  			dev_err(cs->dev,
  				"inbuf overflow, discarding %d bytes
  ",
  				count - n);
  			count = n;
  		}
  		memcpy(inbuf->data + tail, buf, count);
  		tail += count;
  	}
  
  	gig_dbg(DEBUG_INTR, "setting tail to %u", tail);
  	inbuf->tail = tail;
  
  	/* Everything was received .. Push data into handler */
  	gig_dbg(DEBUG_INTR, "%s-->BH", __func__);
  	gigaset_schedule_event(cs);
  	cs_put(cs);
  }
  
  /*
   * Called by the tty driver when there's room for more data to send.
   */
  static void
  gigaset_tty_wakeup(struct tty_struct *tty)
  {
  	struct cardstate *cs = cs_get(tty);
  
  	clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
  	if (!cs)
  		return;
  	tasklet_schedule(&cs->write_tasklet);
  	cs_put(cs);
  }
  
  static struct tty_ldisc_ops gigaset_ldisc = {
  	.owner		= THIS_MODULE,
  	.magic		= TTY_LDISC_MAGIC,
  	.name		= "ser_gigaset",
  	.open		= gigaset_tty_open,
  	.close		= gigaset_tty_close,
  	.hangup		= gigaset_tty_hangup,
  	.read		= gigaset_tty_read,
  	.write		= gigaset_tty_write,
  	.ioctl		= gigaset_tty_ioctl,
  	.receive_buf	= gigaset_tty_receive,
  	.write_wakeup	= gigaset_tty_wakeup,
  };
  
  
  /* Initialization / Shutdown */
  /* ========================= */
  
  static int __init ser_gigaset_init(void)
  {
  	int rc;
  
  	gig_dbg(DEBUG_INIT, "%s", __func__);
  	rc = platform_driver_register(&device_driver);
  	if (rc != 0) {
  		pr_err("error %d registering platform driver
  ", rc);
  		return rc;
  	}
  
  	/* allocate memory for our driver state and initialize it */
  	driver = gigaset_initdriver(GIGASET_MINOR, GIGASET_MINORS,
  				    GIGASET_MODULENAME, GIGASET_DEVNAME,
  				    &ops, THIS_MODULE);
  	if (!driver)
  		goto error;
  
  	rc = tty_register_ldisc(N_GIGASET_M101, &gigaset_ldisc);
  	if (rc != 0) {
  		pr_err("error %d registering line discipline
  ", rc);
  		goto error;
  	}
  
  	return 0;
  
  error:
  	if (driver) {
  		gigaset_freedriver(driver);
  		driver = NULL;
  	}
  	platform_driver_unregister(&device_driver);
  	return rc;
  }
  
  static void __exit ser_gigaset_exit(void)
  {
  	int rc;
  
  	gig_dbg(DEBUG_INIT, "%s", __func__);
  
  	if (driver) {
  		gigaset_freedriver(driver);
  		driver = NULL;
  	}
  
  	rc = tty_unregister_ldisc(N_GIGASET_M101);
  	if (rc != 0)
  		pr_err("error %d unregistering line discipline
  ", rc);
  
  	platform_driver_unregister(&device_driver);
  }
  
  module_init(ser_gigaset_init);
  module_exit(ser_gigaset_exit);