/*

   *  Copyright (C) 1991, 1992  Linus Torvalds
   *
   *  Added support for a Unix98-style ptmx device.
   *    -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998

   *

   *  When reading this code see also fs/devpts. In particular note that the
   *  driver_data field is used by the devpts side as a binding to the devpts
   *  inode.

   */

  #include <linux/module.h>

  
  #include <linux/errno.h>

  #include <linux/interrupt.h>
  #include <linux/tty.h>
  #include <linux/tty_flip.h>
  #include <linux/fcntl.h>

  #include <linux/sched.h>

  #include <linux/string.h>
  #include <linux/major.h>
  #include <linux/mm.h>
  #include <linux/init.h>

  #include <linux/sysctl.h>

  #include <linux/device.h>

  #include <linux/uaccess.h>

  #include <linux/bitops.h>
  #include <linux/devpts_fs.h>

  #include <linux/slab.h>

  #include <asm/system.h>

  #ifdef CONFIG_UNIX98_PTYS

  static struct tty_driver *ptm_driver;

  static struct tty_driver *pts_driver;
  #endif

  static void pty_close(struct tty_struct *tty, struct file *filp)

  {

  	BUG_ON(!tty);
  	if (tty->driver->subtype == PTY_TYPE_MASTER)
  		WARN_ON(tty->count > 1);
  	else {

  		if (tty->count > 2)
  			return;
  	}
  	wake_up_interruptible(&tty->read_wait);
  	wake_up_interruptible(&tty->write_wait);
  	tty->packet = 0;
  	if (!tty->link)
  		return;
  	tty->link->packet = 0;
  	set_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  	wake_up_interruptible(&tty->link->read_wait);
  	wake_up_interruptible(&tty->link->write_wait);
  	if (tty->driver->subtype == PTY_TYPE_MASTER) {
  		set_bit(TTY_OTHER_CLOSED, &tty->flags);
  #ifdef CONFIG_UNIX98_PTYS
  		if (tty->driver == ptm_driver)

  			devpts_pty_kill(tty->link);

  #endif

  		tty_unlock();
  		tty_vhangup(tty->link);
  		tty_lock();

  	}
  }
  
  /*
   * The unthrottle routine is called by the line discipline to signal
   * that it can receive more characters.  For PTY's, the TTY_THROTTLED
   * flag is always set, to force the line discipline to always call the

   * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE

   * characters in the queue.  This is necessary since each time this
   * happens, we need to wake up any sleeping processes that could be
   * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()
   * for the pty buffer to be drained.
   */

  static void pty_unthrottle(struct tty_struct *tty)

  {

  	tty_wakeup(tty->link);

  	set_bit(TTY_THROTTLED, &tty->flags);
  }

  /**
   *	pty_space	-	report space left for writing
   *	@to: tty we are writing into

   *

   *	The tty buffers allow 64K but we sneak a peak and clip at 8K this
   *	allows a lot of overspill room for echo and other fun messes to
   *	be handled properly
   */
  
  static int pty_space(struct tty_struct *to)
  {
  	int n = 8192 - to->buf.memory_used;
  	if (n < 0)
  		return 0;
  	return n;
  }
  
  /**
   *	pty_write		-	write to a pty
   *	@tty: the tty we write from
   *	@buf: kernel buffer of data
   *	@count: bytes to write

   *

   *	Our "hardware" write method. Data is coming from the ldisc which
   *	may be in a non sleeping state. We simply throw this at the other
   *	end of the link as if we were an IRQ handler receiving stuff for
   *	the other side of the pty/tty pair.

   */

  static int pty_write(struct tty_struct *tty, const unsigned char *buf, int c)

  {
  	struct tty_struct *to = tty->link;

  	if (tty->stopped)

  		return 0;

  	if (c > 0) {
  		/* Stuff the data into the input queue of the other end */
  		c = tty_insert_flip_string(to, buf, c);
  		/* And shovel */

  		if (c) {
  			tty_flip_buffer_push(to);
  			tty_wakeup(tty);
  		}

  	}

  	return c;
  }

  /**
   *	pty_write_room	-	write space
   *	@tty: tty we are writing from
   *
   *	Report how many bytes the ldisc can send into the queue for
   *	the other device.
   */

  static int pty_write_room(struct tty_struct *tty)
  {

  	if (tty->stopped)
  		return 0;

  	return pty_space(tty->link);

  }

  /**
   *	pty_chars_in_buffer	-	characters currently in our tx queue
   *	@tty: our tty

   *

   *	Report how much we have in the transmit queue. As everything is
   *	instantly at the other end this is easy to implement.

   */

  static int pty_chars_in_buffer(struct tty_struct *tty)
  {

  	return 0;

  }
  
  /* Set the lock flag on a pty */

  static int pty_set_lock(struct tty_struct *tty, int __user *arg)

  {
  	int val;

  	if (get_user(val, arg))

  		return -EFAULT;
  	if (val)
  		set_bit(TTY_PTY_LOCK, &tty->flags);
  	else
  		clear_bit(TTY_PTY_LOCK, &tty->flags);
  	return 0;
  }

  /* Send a signal to the slave */
  static int pty_signal(struct tty_struct *tty, int sig)
  {
  	unsigned long flags;
  	struct pid *pgrp;
  
  	if (tty->link) {
  		spin_lock_irqsave(&tty->link->ctrl_lock, flags);
  		pgrp = get_pid(tty->link->pgrp);
  		spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
  
  		kill_pgrp(pgrp, sig, 1);
  		put_pid(pgrp);
  	}
  	return 0;
  }

  static void pty_flush_buffer(struct tty_struct *tty)
  {
  	struct tty_struct *to = tty->link;

  	unsigned long flags;

  	if (!to)
  		return;

  	/* tty_buffer_flush(to); FIXME */

  	if (to->packet) {

  		spin_lock_irqsave(&tty->ctrl_lock, flags);

  		tty->ctrl_status |= TIOCPKT_FLUSHWRITE;
  		wake_up_interruptible(&to->read_wait);

  		spin_unlock_irqrestore(&tty->ctrl_lock, flags);

  	}
  }

  static int pty_open(struct tty_struct *tty, struct file *filp)

  {
  	int	retval = -ENODEV;
  
  	if (!tty || !tty->link)
  		goto out;
  
  	retval = -EIO;
  	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
  		goto out;
  	if (test_bit(TTY_PTY_LOCK, &tty->link->flags))
  		goto out;
  	if (tty->link->count != 1)
  		goto out;
  
  	clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);
  	set_bit(TTY_THROTTLED, &tty->flags);

  	retval = 0;
  out:
  	return retval;
  }

  static void pty_set_termios(struct tty_struct *tty,
  					struct ktermios *old_termios)

  {

  	tty->termios->c_cflag &= ~(CSIZE | PARENB);
  	tty->termios->c_cflag |= (CS8 | CREAD);

  }

  /**
   *	pty_do_resize		-	resize event
   *	@tty: tty being resized

   *	@ws: window size being set.

   *

   *	Update the termios variables and send the necessary signals to

   *	peform a terminal resize correctly
   */
  
  int pty_resize(struct tty_struct *tty,  struct winsize *ws)
  {
  	struct pid *pgrp, *rpgrp;
  	unsigned long flags;
  	struct tty_struct *pty = tty->link;
  
  	/* For a PTY we need to lock the tty side */
  	mutex_lock(&tty->termios_mutex);
  	if (!memcmp(ws, &tty->winsize, sizeof(*ws)))
  		goto done;
  
  	/* Get the PID values and reference them so we can
  	   avoid holding the tty ctrl lock while sending signals.
  	   We need to lock these individually however. */
  
  	spin_lock_irqsave(&tty->ctrl_lock, flags);
  	pgrp = get_pid(tty->pgrp);
  	spin_unlock_irqrestore(&tty->ctrl_lock, flags);
  
  	spin_lock_irqsave(&pty->ctrl_lock, flags);
  	rpgrp = get_pid(pty->pgrp);
  	spin_unlock_irqrestore(&pty->ctrl_lock, flags);
  
  	if (pgrp)
  		kill_pgrp(pgrp, SIGWINCH, 1);
  	if (rpgrp != pgrp && rpgrp)
  		kill_pgrp(rpgrp, SIGWINCH, 1);
  
  	put_pid(pgrp);
  	put_pid(rpgrp);
  
  	tty->winsize = *ws;
  	pty->winsize = *ws;	/* Never used so will go away soon */
  done:
  	mutex_unlock(&tty->termios_mutex);
  	return 0;
  }

  /* Traditional BSD devices */
  #ifdef CONFIG_LEGACY_PTYS

  static int pty_install(struct tty_driver *driver, struct tty_struct *tty)
  {
  	struct tty_struct *o_tty;
  	int idx = tty->index;
  	int retval;
  
  	o_tty = alloc_tty_struct();
  	if (!o_tty)
  		return -ENOMEM;
  	if (!try_module_get(driver->other->owner)) {
  		/* This cannot in fact currently happen */

  		retval = -ENOMEM;
  		goto err_free_tty;

  	}
  	initialize_tty_struct(o_tty, driver->other, idx);
  
  	/* We always use new tty termios data so we can do this
  	   the easy way .. */
  	retval = tty_init_termios(tty);
  	if (retval)

  		goto err_deinit_tty;

  
  	retval = tty_init_termios(o_tty);

  	if (retval)
  		goto err_free_termios;

  	/*
  	 * Everything allocated ... set up the o_tty structure.
  	 */
  	driver->other->ttys[idx] = o_tty;
  	tty_driver_kref_get(driver->other);
  	if (driver->subtype == PTY_TYPE_MASTER)
  		o_tty->count++;
  	/* Establish the links in both directions */
  	tty->link   = o_tty;
  	o_tty->link = tty;
  
  	tty_driver_kref_get(driver);
  	tty->count++;
  	driver->ttys[idx] = tty;
  	return 0;

  err_free_termios:
  	tty_free_termios(tty);

  err_deinit_tty:
  	deinitialize_tty_struct(o_tty);

  	module_put(o_tty->driver->owner);

  err_free_tty:

  	free_tty_struct(o_tty);

  	return retval;

  }

  static int pty_bsd_ioctl(struct tty_struct *tty,

  			 unsigned int cmd, unsigned long arg)
  {
  	switch (cmd) {
  	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
  		return pty_set_lock(tty, (int __user *) arg);

  	case TIOCSIG:    /* Send signal to other side of pty */
  		return pty_signal(tty, (int) arg);

  	}
  	return -ENOIOCTLCMD;
  }

  static int legacy_count = CONFIG_LEGACY_PTY_COUNT;
  module_param(legacy_count, int, 0);

  /*
   * The master side of a pty can do TIOCSPTLCK and thus
   * has pty_bsd_ioctl.
   */
  static const struct tty_operations master_pty_ops_bsd = {
  	.install = pty_install,

  	.open = pty_open,
  	.close = pty_close,
  	.write = pty_write,
  	.write_room = pty_write_room,
  	.flush_buffer = pty_flush_buffer,
  	.chars_in_buffer = pty_chars_in_buffer,
  	.unthrottle = pty_unthrottle,
  	.set_termios = pty_set_termios,
  	.ioctl = pty_bsd_ioctl,

  	.resize = pty_resize

  };

  static const struct tty_operations slave_pty_ops_bsd = {
  	.install = pty_install,
  	.open = pty_open,
  	.close = pty_close,
  	.write = pty_write,
  	.write_room = pty_write_room,
  	.flush_buffer = pty_flush_buffer,
  	.chars_in_buffer = pty_chars_in_buffer,
  	.unthrottle = pty_unthrottle,
  	.set_termios = pty_set_termios,
  	.resize = pty_resize
  };

  static void __init legacy_pty_init(void)
  {

  	struct tty_driver *pty_driver, *pty_slave_driver;

  	if (legacy_count <= 0)
  		return;

  	pty_driver = alloc_tty_driver(legacy_count);

  	if (!pty_driver)
  		panic("Couldn't allocate pty driver");

  	pty_slave_driver = alloc_tty_driver(legacy_count);

  	if (!pty_slave_driver)
  		panic("Couldn't allocate pty slave driver");
  
  	pty_driver->owner = THIS_MODULE;
  	pty_driver->driver_name = "pty_master";
  	pty_driver->name = "pty";

  	pty_driver->major = PTY_MASTER_MAJOR;
  	pty_driver->minor_start = 0;
  	pty_driver->type = TTY_DRIVER_TYPE_PTY;
  	pty_driver->subtype = PTY_TYPE_MASTER;
  	pty_driver->init_termios = tty_std_termios;
  	pty_driver->init_termios.c_iflag = 0;
  	pty_driver->init_termios.c_oflag = 0;
  	pty_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
  	pty_driver->init_termios.c_lflag = 0;

  	pty_driver->init_termios.c_ispeed = 38400;
  	pty_driver->init_termios.c_ospeed = 38400;

  	pty_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;
  	pty_driver->other = pty_slave_driver;

  	tty_set_operations(pty_driver, &master_pty_ops_bsd);

  
  	pty_slave_driver->owner = THIS_MODULE;
  	pty_slave_driver->driver_name = "pty_slave";
  	pty_slave_driver->name = "ttyp";

  	pty_slave_driver->major = PTY_SLAVE_MAJOR;
  	pty_slave_driver->minor_start = 0;
  	pty_slave_driver->type = TTY_DRIVER_TYPE_PTY;
  	pty_slave_driver->subtype = PTY_TYPE_SLAVE;
  	pty_slave_driver->init_termios = tty_std_termios;
  	pty_slave_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;

  	pty_slave_driver->init_termios.c_ispeed = 38400;
  	pty_slave_driver->init_termios.c_ospeed = 38400;

  	pty_slave_driver->flags = TTY_DRIVER_RESET_TERMIOS |
  					TTY_DRIVER_REAL_RAW;
  	pty_slave_driver->other = pty_driver;

  	tty_set_operations(pty_slave_driver, &slave_pty_ops_bsd);

  
  	if (tty_register_driver(pty_driver))
  		panic("Couldn't register pty driver");
  	if (tty_register_driver(pty_slave_driver))
  		panic("Couldn't register pty slave driver");
  }
  #else
  static inline void legacy_pty_init(void) { }
  #endif
  
  /* Unix98 devices */
  #ifdef CONFIG_UNIX98_PTYS
  /*
   * sysctl support for setting limits on the number of Unix98 ptys allocated.
   * Otherwise one can eat up all kernel memory by opening /dev/ptmx repeatedly.
   */
  int pty_limit = NR_UNIX98_PTY_DEFAULT;

  static int pty_limit_min;

  static int pty_limit_max = NR_UNIX98_PTY_MAX;

  static int pty_count;

  static struct cdev ptmx_cdev;

  static struct ctl_table pty_table[] = {

  	{

  		.procname	= "max",
  		.maxlen		= sizeof(int),
  		.mode		= 0644,
  		.data		= &pty_limit,

  		.proc_handler	= proc_dointvec_minmax,

  		.extra1		= &pty_limit_min,
  		.extra2		= &pty_limit_max,
  	}, {

  		.procname	= "nr",
  		.maxlen		= sizeof(int),
  		.mode		= 0444,

  		.data		= &pty_count,

  		.proc_handler	= proc_dointvec,

  	}, 
  	{}

  };

  static struct ctl_table pty_kern_table[] = {
  	{

  		.procname	= "pty",
  		.mode		= 0555,
  		.child		= pty_table,
  	},
  	{}
  };
  
  static struct ctl_table pty_root_table[] = {
  	{

  		.procname	= "kernel",
  		.mode		= 0555,
  		.child		= pty_kern_table,
  	},
  	{}
  };

  static int pty_unix98_ioctl(struct tty_struct *tty,

  			    unsigned int cmd, unsigned long arg)
  {
  	switch (cmd) {
  	case TIOCSPTLCK: /* Set PT Lock (disallow slave open) */
  		return pty_set_lock(tty, (int __user *)arg);
  	case TIOCGPTN: /* Get PT Number */
  		return put_user(tty->index, (unsigned int __user *)arg);

  	case TIOCSIG:    /* Send signal to other side of pty */
  		return pty_signal(tty, (int) arg);

  	}
  
  	return -ENOIOCTLCMD;
  }

  /**
   *	ptm_unix98_lookup	-	find a pty master
   *	@driver: ptm driver
   *	@idx: tty index
   *
   *	Look up a pty master device. Called under the tty_mutex for now.
   *	This provides our locking.
   */

  static struct tty_struct *ptm_unix98_lookup(struct tty_driver *driver,
  		struct inode *ptm_inode, int idx)

  {

  	struct tty_struct *tty = devpts_get_tty(ptm_inode, idx);

  	if (tty)
  		tty = tty->link;
  	return tty;
  }
  
  /**
   *	pts_unix98_lookup	-	find a pty slave
   *	@driver: pts driver
   *	@idx: tty index
   *
   *	Look up a pty master device. Called under the tty_mutex for now.
   *	This provides our locking.
   */

  static struct tty_struct *pts_unix98_lookup(struct tty_driver *driver,
  		struct inode *pts_inode, int idx)

  {

  	struct tty_struct *tty = devpts_get_tty(pts_inode, idx);

  	/* Master must be open before slave */
  	if (!tty)
  		return ERR_PTR(-EIO);
  	return tty;
  }

  static void pty_unix98_shutdown(struct tty_struct *tty)

  {

  	tty_driver_remove_tty(tty->driver, tty);

  	/* We have our own method as we don't use the tty index */
  	kfree(tty->termios);

  }

  /* We have no need to install and remove our tty objects as devpts does all
     the work for us */

  static int pty_unix98_install(struct tty_driver *driver, struct tty_struct *tty)

  {

  	struct tty_struct *o_tty;
  	int idx = tty->index;
  
  	o_tty = alloc_tty_struct();
  	if (!o_tty)
  		return -ENOMEM;
  	if (!try_module_get(driver->other->owner)) {
  		/* This cannot in fact currently happen */

  		goto err_free_tty;

  	}
  	initialize_tty_struct(o_tty, driver->other, idx);

  	tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);

  	if (tty->termios == NULL)

  		goto err_free_mem;

  	*tty->termios = driver->init_termios;

  	tty->termios_locked = tty->termios + 1;
  
  	o_tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);

  	if (o_tty->termios == NULL)

  		goto err_free_mem;

  	*o_tty->termios = driver->other->init_termios;

  	o_tty->termios_locked = o_tty->termios + 1;

  
  	tty_driver_kref_get(driver->other);
  	if (driver->subtype == PTY_TYPE_MASTER)
  		o_tty->count++;
  	/* Establish the links in both directions */
  	tty->link   = o_tty;
  	o_tty->link = tty;
  	/*
  	 * All structures have been allocated, so now we install them.
  	 * Failures after this point use release_tty to clean up, so
  	 * there's no need to null out the local pointers.
  	 */
  	tty_driver_kref_get(driver);
  	tty->count++;

  	pty_count++;

  	return 0;

  err_free_mem:

  	deinitialize_tty_struct(o_tty);

  	kfree(o_tty->termios);

  	kfree(tty->termios);

  	module_put(o_tty->driver->owner);

  err_free_tty:

  	free_tty_struct(o_tty);

  	return -ENOMEM;

  }

  static void ptm_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
  {
  	pty_count--;
  }
  
  static void pts_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)

  {
  }

  static const struct tty_operations ptm_unix98_ops = {

  	.lookup = ptm_unix98_lookup,

  	.install = pty_unix98_install,

  	.remove = ptm_unix98_remove,

  	.open = pty_open,
  	.close = pty_close,
  	.write = pty_write,
  	.write_room = pty_write_room,
  	.flush_buffer = pty_flush_buffer,
  	.chars_in_buffer = pty_chars_in_buffer,
  	.unthrottle = pty_unthrottle,
  	.set_termios = pty_set_termios,

  	.ioctl = pty_unix98_ioctl,

  	.shutdown = pty_unix98_shutdown,
  	.resize = pty_resize

  };

  static const struct tty_operations pty_unix98_ops = {
  	.lookup = pts_unix98_lookup,

  	.install = pty_unix98_install,

  	.remove = pts_unix98_remove,

  	.open = pty_open,
  	.close = pty_close,
  	.write = pty_write,
  	.write_room = pty_write_room,
  	.flush_buffer = pty_flush_buffer,
  	.chars_in_buffer = pty_chars_in_buffer,
  	.unthrottle = pty_unthrottle,
  	.set_termios = pty_set_termios,

  	.shutdown = pty_unix98_shutdown

  };

  
  /**
   *	ptmx_open		-	open a unix 98 pty master
   *	@inode: inode of device file
   *	@filp: file pointer to tty
   *
   *	Allocate a unix98 pty master device from the ptmx driver.
   *
   *	Locking: tty_mutex protects the init_dev work. tty->count should
   * 		protect the rest.
   *		allocated_ptys_lock handles the list of free pty numbers
   */

  static int ptmx_open(struct inode *inode, struct file *filp)

  {
  	struct tty_struct *tty;
  	int retval;
  	int index;
  
  	nonseekable_open(inode, filp);

  	retval = tty_alloc_file(filp);
  	if (retval)
  		return retval;

  	/* find a device that is not in use. */

  	tty_lock();

  	index = devpts_new_index(inode);

  	tty_unlock();

  	if (index < 0) {
  		retval = index;
  		goto err_file;
  	}

  
  	mutex_lock(&tty_mutex);

  	tty_lock();

  	tty = tty_init_dev(ptm_driver, index, 1);

  	mutex_unlock(&tty_mutex);

  	if (IS_ERR(tty)) {
  		retval = PTR_ERR(tty);

  		goto out;

  	}

  
  	set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */

  	tty_add_file(tty, filp);

  	retval = devpts_pty_new(inode, tty->link);

  	if (retval)

  		goto err_release;

  
  	retval = ptm_driver->ops->open(tty, filp);

  	if (retval)

  		goto err_release;

  	tty_unlock();

  	return 0;
  err_release:

  	tty_unlock();

  	tty_release(inode, filp);

  	return retval;
  out:

  	devpts_kill_index(inode, index);

  	tty_unlock();

  err_file:
  	tty_free_file(filp);

  	return retval;

  }
  
  static struct file_operations ptmx_fops;

  static void __init unix98_pty_init(void)
  {

  	ptm_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
  	if (!ptm_driver)
  		panic("Couldn't allocate Unix98 ptm driver");
  	pts_driver = alloc_tty_driver(NR_UNIX98_PTY_MAX);
  	if (!pts_driver)
  		panic("Couldn't allocate Unix98 pts driver");
  
  	ptm_driver->owner = THIS_MODULE;
  	ptm_driver->driver_name = "pty_master";
  	ptm_driver->name = "ptm";
  	ptm_driver->major = UNIX98_PTY_MASTER_MAJOR;
  	ptm_driver->minor_start = 0;
  	ptm_driver->type = TTY_DRIVER_TYPE_PTY;
  	ptm_driver->subtype = PTY_TYPE_MASTER;
  	ptm_driver->init_termios = tty_std_termios;
  	ptm_driver->init_termios.c_iflag = 0;
  	ptm_driver->init_termios.c_oflag = 0;
  	ptm_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;
  	ptm_driver->init_termios.c_lflag = 0;

  	ptm_driver->init_termios.c_ispeed = 38400;
  	ptm_driver->init_termios.c_ospeed = 38400;

  	ptm_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |

  		TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;

  	ptm_driver->other = pts_driver;

  	tty_set_operations(ptm_driver, &ptm_unix98_ops);

  
  	pts_driver->owner = THIS_MODULE;
  	pts_driver->driver_name = "pty_slave";
  	pts_driver->name = "pts";
  	pts_driver->major = UNIX98_PTY_SLAVE_MAJOR;
  	pts_driver->minor_start = 0;
  	pts_driver->type = TTY_DRIVER_TYPE_PTY;
  	pts_driver->subtype = PTY_TYPE_SLAVE;
  	pts_driver->init_termios = tty_std_termios;
  	pts_driver->init_termios.c_cflag = B38400 | CS8 | CREAD;

  	pts_driver->init_termios.c_ispeed = 38400;
  	pts_driver->init_termios.c_ospeed = 38400;

  	pts_driver->flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW |

  		TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_DEVPTS_MEM;

  	pts_driver->other = ptm_driver;

  	tty_set_operations(pts_driver, &pty_unix98_ops);

  	if (tty_register_driver(ptm_driver))
  		panic("Couldn't register Unix98 ptm driver");
  	if (tty_register_driver(pts_driver))
  		panic("Couldn't register Unix98 pts driver");

  	register_sysctl_table(pty_root_table);

  
  	/* Now create the /dev/ptmx special device */
  	tty_default_fops(&ptmx_fops);
  	ptmx_fops.open = ptmx_open;
  
  	cdev_init(&ptmx_cdev, &ptmx_fops);
  	if (cdev_add(&ptmx_cdev, MKDEV(TTYAUX_MAJOR, 2), 1) ||
  	    register_chrdev_region(MKDEV(TTYAUX_MAJOR, 2), 1, "/dev/ptmx") < 0)
  		panic("Couldn't register /dev/ptmx driver
  ");
  	device_create(tty_class, NULL, MKDEV(TTYAUX_MAJOR, 2), NULL, "ptmx");

  }

  #else
  static inline void unix98_pty_init(void) { }
  #endif
  
  static int __init pty_init(void)
  {
  	legacy_pty_init();
  	unix98_pty_init();
  	return 0;
  }
  module_init(pty_init);