TTY: create drivers/tty and move the tty core files there

The tty code should be in its own subdirectory and not in the char
driver with all of the cruft that is currently there.

Based on work done by Arnd Bergmann <arnd@arndb.de>

Acked-by: Arnd Bergmann <arnd@arndb.de>
Cc: Jiri Slaby <jslaby@suse.cz>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

1 files changed, 777 insertions, 0 deletions

diff --git a/drivers/tty/pty.c b/drivers/tty/pty.c
new file mode 100644
index 000000000000..923a48585501
--- /dev/null
+++ b/drivers/tty/pty.c
@@ -0,0 +1,777 @@
+/*
+ *  linux/drivers/char/pty.c
+ *
+ *  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/smp_lock.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 */
+                free_tty_struct(o_tty);
+                return -ENOMEM;
+        }
+        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 free_mem_out;
+
+        retval = tty_init_termios(o_tty);
+        if (retval) {
+                tty_free_termios(tty);
+                goto free_mem_out;
+        }
+
+        /*
+         * 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;
+free_mem_out:
+        module_put(o_tty->driver->owner);
+        free_tty_struct(o_tty);
+        return -ENOMEM;
+}
+
+static int pty_bsd_ioctl(struct tty_struct *tty, struct file *file,
+                         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, struct file *file,
+                            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)
+{
+        /* 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 */
+                free_tty_struct(o_tty);
+                return -ENOMEM;
+        }
+        initialize_tty_struct(o_tty, driver->other, idx);
+
+        tty->termios = kzalloc(sizeof(struct ktermios[2]), GFP_KERNEL);
+        if (tty->termios == NULL)
+                goto free_mem_out;
+        *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 free_mem_out;
+        *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;
+free_mem_out:
+        kfree(o_tty->termios);
+        module_put(o_tty->driver->owner);
+        free_tty_struct(o_tty);
+        kfree(tty->termios);
+        return -ENOMEM;
+}
+
+static void pty_unix98_remove(struct tty_driver *driver, struct tty_struct *tty)
+{
+        pty_count--;
+}
+
+static const struct tty_operations ptm_unix98_ops = {
+        .lookup = ptm_unix98_lookup,
+        .install = pty_unix98_install,
+        .remove = pty_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 = pty_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);
+
+        /* find a device that is not in use. */
+        tty_lock();
+        index = devpts_new_index(inode);
+        tty_unlock();
+        if (index < 0)
+                return index;
+
+        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 */
+
+        retval = tty_add_file(tty, filp);
+        if (retval)
+                goto out;
+
+        retval = devpts_pty_new(inode, tty->link);
+        if (retval)
+                goto out1;
+
+        retval = ptm_driver->ops->open(tty, filp);
+        if (retval)
+                goto out2;
+out1:
+        tty_unlock();
+        return retval;
+out2:
+        tty_unlock();
+        tty_release(inode, filp);
+        return retval;
+out:
+        devpts_kill_index(inode, index);
+        tty_unlock();
+        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\n");
+        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);