Import 2.1.118

[davej-history.git] / drivers / char / tty_io.c

/*
 *  linux/drivers/char/tty_io.c
 *
 *  Copyright (C) 1991, 1992  Linus Torvalds
 */

/*
 * 'tty_io.c' gives an orthogonal feeling to tty's, be they consoles
 * or rs-channels. It also implements echoing, cooked mode etc.
 *
 * Kill-line thanks to John T Kohl, who also corrected VMIN = VTIME = 0.
 *
 * Modified by Theodore Ts'o, 9/14/92, to dynamically allocate the
 * tty_struct and tty_queue structures.  Previously there was an array
 * of 256 tty_struct's which was statically allocated, and the
 * tty_queue structures were allocated at boot time.  Both are now
 * dynamically allocated only when the tty is open.
 *
 * Also restructured routines so that there is more of a separation
 * between the high-level tty routines (tty_io.c and tty_ioctl.c) and
 * the low-level tty routines (serial.c, pty.c, console.c).  This
 * makes for cleaner and more compact code.  -TYT, 9/17/92 
 *
 * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
 * which can be dynamically activated and de-activated by the line
 * discipline handling modules (like SLIP).
 *
 * NOTE: pay no attention to the line discipline code (yet); its
 * interface is still subject to change in this version...
 * -- TYT, 1/31/92
 *
 * Added functionality to the OPOST tty handling.  No delays, but all
 * other bits should be there.
 *      -- Nick Holloway <alfie@dcs.warwick.ac.uk>, 27th May 1993.
 *
 * Rewrote canonical mode and added more termios flags.
 *      -- julian@uhunix.uhcc.hawaii.edu (J. Cowley), 13Jan94
 *
 * Reorganized FASYNC support so mouse code can share it.
 *      -- ctm@ardi.com, 9Sep95
 *
 * New TIOCLINUX variants added.
 *      -- mj@k332.feld.cvut.cz, 19-Nov-95
 * 
 * Restrict vt switching via ioctl()
 *      -- grif@cs.ucr.edu, 5-Dec-95
 *
 * Move console and virtual terminal code to more appropriate files,
 * implement CONFIG_VT and generalize console device interface.
 *      -- Marko Kohtala <Marko.Kohtala@hut.fi>, March 97
 *
 * Rewrote init_dev and release_dev to eliminate races.
 *      -- Bill Hawes <whawes@star.net>, June 97
 *
 * Added support for a Unix98-style ptmx device.
 *      -- C. Scott Ananian <cananian@alumni.princeton.edu>, 14-Jan-1998
 */

#include <linux/config.h>
#include <linux/types.h>
#include <linux/major.h>
#include <linux/errno.h>
#include <linux/signal.h>
#include <linux/fcntl.h>
#include <linux/sched.h>
#include <linux/interrupt.h>
#include <linux/tty.h>
#include <linux/tty_driver.h>
#include <linux/tty_flip.h>
#include <linux/devpts_fs.h>
#include <linux/file.h>
#include <linux/console.h>
#include <linux/timer.h>
#include <linux/ctype.h>
#include <linux/kd.h>
#include <linux/mm.h>
#include <linux/string.h>
#include <linux/malloc.h>
#include <linux/poll.h>
#ifdef CONFIG_PROC_FS
#include <linux/proc_fs.h>
#endif
#include <linux/init.h>
#include <linux/smp_lock.h>

#include <asm/uaccess.h>
#include <asm/system.h>
#include <asm/bitops.h>

#include <linux/kbd_kern.h>
#include <linux/vt_kern.h>
#include <linux/selection.h>

#ifdef CONFIG_KMOD
#include <linux/kmod.h>
#endif

#define CONSOLE_DEV MKDEV(TTY_MAJOR,0)
#define TTY_DEV MKDEV(TTYAUX_MAJOR,0)
#define SYSCONS_DEV MKDEV(TTYAUX_MAJOR,1)
#define PTMX_DEV MKDEV(TTYAUX_MAJOR,2)

#undef TTY_DEBUG_HANGUP

#define TTY_PARANOIA_CHECK 1
#define CHECK_TTY_COUNT 1

struct termios tty_std_termios;         /* for the benefit of tty drivers  */
struct tty_driver *tty_drivers = NULL;  /* linked list of tty drivers */
struct tty_ldisc ldiscs[NR_LDISCS];     /* line disc dispatch table     */

#ifdef CONFIG_UNIX98_PTYS
extern struct tty_driver ptm_driver[];  /* Unix98 pty masters; for /dev/ptmx */
#endif

/*
 * redirect is the pseudo-tty that console output
 * is redirected to if asked by TIOCCONS.
 */
struct tty_struct * redirect = NULL;

static void initialize_tty_struct(struct tty_struct *tty);

static ssize_t tty_read(struct file *, char *, size_t, loff_t *);
static ssize_t tty_write(struct file *, const char *, size_t, loff_t *);
static unsigned int tty_poll(struct file *, poll_table *);
static int tty_open(struct inode *, struct file *);
static int tty_release(struct inode *, struct file *);
static int tty_ioctl(struct inode * inode, struct file * file,
                     unsigned int cmd, unsigned long arg);
static int tty_fasync(int fd, struct file * filp, int on);
#ifdef CONFIG_8xx
extern long console_8xx_init(void);
extern int rs_8xx_init(void);
#endif /* CONFIG_8xx */

#ifndef MIN
#define MIN(a,b)        ((a) < (b) ? (a) : (b))
#endif

/*
 * This routine returns the name of tty.
 */
#define TTY_NUMBER(tty) (MINOR((tty)->device) - (tty)->driver.minor_start + \
                         (tty)->driver.name_base)
        
char *tty_name(struct tty_struct *tty, char *buf)
{
        if (tty)
                sprintf(buf, "%s%d", tty->driver.name, TTY_NUMBER(tty));
        else
                strcpy(buf, "NULL tty");
        return buf;
}

inline int tty_paranoia_check(struct tty_struct *tty, kdev_t device,
                              const char *routine)
{
#ifdef TTY_PARANOIA_CHECK
        static const char *badmagic =
                "Warning: bad magic number for tty struct (%s) in %s\n";
        static const char *badtty =
                "Warning: null TTY for (%s) in %s\n";

        if (!tty) {
                printk(badtty, kdevname(device), routine);
                return 1;
        }
        if (tty->magic != TTY_MAGIC) {
                printk(badmagic, kdevname(device), routine);
                return 1;
        }
#endif
        return 0;
}

static int check_tty_count(struct tty_struct *tty, const char *routine)
{
#ifdef CHECK_TTY_COUNT
        struct file *f;
        int count = 0;
        
        for(f = inuse_filps; f; f = f->f_next) {
                if(f->private_data == tty)
                        count++;
        }
        if (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
            tty->driver.subtype == PTY_TYPE_SLAVE &&
            tty->link && tty->link->count)
                count++;
        if (tty->count != count) {
                printk("Warning: dev (%s) tty->count(%d) != #fd's(%d) in %s\n",
                       kdevname(tty->device), tty->count, count, routine);
                return count;
       }        
#endif
        return 0;
}

int tty_register_ldisc(int disc, struct tty_ldisc *new_ldisc)
{
        if (disc < N_TTY || disc >= NR_LDISCS)
                return -EINVAL;
        
        if (new_ldisc) {
                ldiscs[disc] = *new_ldisc;
                ldiscs[disc].flags |= LDISC_FLAG_DEFINED;
                ldiscs[disc].num = disc;
        } else
                memset(&ldiscs[disc], 0, sizeof(struct tty_ldisc));
        
        return 0;
}

/* Set the discipline of a tty line. */
static int tty_set_ldisc(struct tty_struct *tty, int ldisc)
{
        int     retval = 0;
        struct  tty_ldisc o_ldisc;
        char buf[64];

        if ((ldisc < N_TTY) || (ldisc >= NR_LDISCS))
                return -EINVAL;
#ifdef CONFIG_KMOD
        /* Eduardo Blanco <ejbs@cs.cs.com.uy> */
        /* Cyrus Durgin <cider@speakeasy.org> */
        if (!(ldiscs[ldisc].flags & LDISC_FLAG_DEFINED)) {
                char modname [20];
                sprintf(modname, "tty-ldisc-%d", ldisc);
                request_module (modname);
        }
#endif
        if (!(ldiscs[ldisc].flags & LDISC_FLAG_DEFINED))
                return -EINVAL;

        if (tty->ldisc.num == ldisc)
                return 0;       /* We are already in the desired discipline */
        o_ldisc = tty->ldisc;

        tty_wait_until_sent(tty, 0);
        
        /* Shutdown the current discipline. */
        if (tty->ldisc.close)
                (tty->ldisc.close)(tty);

        /* Now set up the new line discipline. */
        tty->ldisc = ldiscs[ldisc];
        tty->termios->c_line = ldisc;
        if (tty->ldisc.open)
                retval = (tty->ldisc.open)(tty);
        if (retval < 0) {
                tty->ldisc = o_ldisc;
                tty->termios->c_line = tty->ldisc.num;
                if (tty->ldisc.open && (tty->ldisc.open(tty) < 0)) {
                        tty->ldisc = ldiscs[N_TTY];
                        tty->termios->c_line = N_TTY;
                        if (tty->ldisc.open) {
                                int r = tty->ldisc.open(tty);

                                if (r < 0)
                                        panic("Couldn't open N_TTY ldisc for "
                                              "%s --- error %d.",
                                              tty_name(tty, buf), r);
                        }
                }
        }
        if (tty->ldisc.num != o_ldisc.num && tty->driver.set_ldisc)
                tty->driver.set_ldisc(tty);
        return retval;
}

/*
 * This routine returns a tty driver structure, given a device number
 */
struct tty_driver *get_tty_driver(kdev_t device)
{
        int     major, minor;
        struct tty_driver *p;
        
        minor = MINOR(device);
        major = MAJOR(device);

        for (p = tty_drivers; p; p = p->next) {
                if (p->major != major)
                        continue;
                if (minor < p->minor_start)
                        continue;
                if (minor >= p->minor_start + p->num)
                        continue;
                return p;
        }
        return NULL;
}

/*
 * If we try to write to, or set the state of, a terminal and we're
 * not in the foreground, send a SIGTTOU.  If the signal is blocked or
 * ignored, go ahead and perform the operation.  (POSIX 7.2)
 */
int tty_check_change(struct tty_struct * tty)
{
        if (current->tty != tty)
                return 0;
        if (tty->pgrp <= 0) {
                printk("tty_check_change: tty->pgrp <= 0!\n");
                return 0;
        }
        if (current->pgrp == tty->pgrp)
                return 0;
        if (is_ignored(SIGTTOU))
                return 0;
        if (is_orphaned_pgrp(current->pgrp))
                return -EIO;
        (void) kill_pg(current->pgrp,SIGTTOU,1);
        return -ERESTARTSYS;
}

static ssize_t hung_up_tty_read(struct file * file, char * buf,
                                size_t count, loff_t *ppos)
{
        /* Can't seek (pread) on ttys.  */
        if (ppos != &file->f_pos)
                return -ESPIPE;
        return 0;
}

static ssize_t hung_up_tty_write(struct file * file, const char * buf,
                                 size_t count, loff_t *ppos)
{
        /* Can't seek (pwrite) on ttys.  */
        if (ppos != &file->f_pos)
                return -ESPIPE;
        return -EIO;
}

static unsigned int hung_up_tty_poll(struct file * filp, poll_table * wait)
{
        return POLLIN | POLLOUT | POLLERR | POLLHUP | POLLRDNORM | POLLWRNORM;
}

static int hung_up_tty_ioctl(struct inode * inode, struct file * file,
                             unsigned int cmd, unsigned long arg)
{
        return cmd == TIOCSPGRP ? -ENOTTY : -EIO;
}

static long long tty_lseek(struct file * file,  long long offset, int orig)
{
        return -ESPIPE;
}

static struct file_operations tty_fops = {
        tty_lseek,
        tty_read,
        tty_write,
        NULL,           /* tty_readdir */
        tty_poll,
        tty_ioctl,
        NULL,           /* tty_mmap */
        tty_open,
        NULL,           /* flush */
        tty_release,
        NULL,           /* tty_fsync */
        tty_fasync
};

static struct file_operations hung_up_tty_fops = {
        tty_lseek,
        hung_up_tty_read,
        hung_up_tty_write,
        NULL,           /* hung_up_tty_readdir */
        hung_up_tty_poll,
        hung_up_tty_ioctl,
        NULL,           /* hung_up_tty_mmap */
        NULL,           /* hung_up_tty_open */
        NULL,           /* flush */
        tty_release,    /* hung_up_tty_release */
        NULL,           /* hung_up_tty_fsync  */
        NULL            /* hung_up_tty_fasync */
};

/*
 * This can be called through the "tq_scheduler" 
 * task-list. That is process synchronous, but
 * doesn't hold any locks, so we need to make
 * sure we have the appropriate locks for what
 * we're doing..
 */
void do_tty_hangup(void *data)
{
        struct tty_struct *tty = (struct tty_struct *) data;
        struct file * filp;
        struct task_struct *p;

        if (!tty)
                return;

        /* inuse_filps is protected by the single kernel lock */
        lock_kernel();
        
        check_tty_count(tty, "do_tty_hangup");
        for (filp = inuse_filps; filp; filp = filp->f_next) {
                if (filp->private_data != tty)
                        continue;
                if (!filp->f_dentry)
                        continue;
                if (!filp->f_dentry->d_inode)
                        continue;
                if (filp->f_dentry->d_inode->i_rdev == CONSOLE_DEV ||
                    filp->f_dentry->d_inode->i_rdev == SYSCONS_DEV)
                        continue;
                if (filp->f_op != &tty_fops)
                        continue;
                tty_fasync(-1, filp, 0);
                filp->f_op = &hung_up_tty_fops;
        }
        
        /* FIXME! What are the locking issues here? This may me overdoing things.. */
        {
                unsigned long flags;

                save_flags(flags); cli();
                if (tty->ldisc.flush_buffer)
                        tty->ldisc.flush_buffer(tty);
                if (tty->driver.flush_buffer)
                        tty->driver.flush_buffer(tty);
                if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
                    tty->ldisc.write_wakeup)
                        (tty->ldisc.write_wakeup)(tty);
                restore_flags(flags);
        }

        wake_up_interruptible(&tty->write_wait);
        wake_up_interruptible(&tty->read_wait);

        /*
         * Shutdown the current line discipline, and reset it to
         * N_TTY.
         */
        if (tty->driver.flags & TTY_DRIVER_RESET_TERMIOS)
                *tty->termios = tty->driver.init_termios;
        if (tty->ldisc.num != ldiscs[N_TTY].num) {
                if (tty->ldisc.close)
                        (tty->ldisc.close)(tty);
                tty->ldisc = ldiscs[N_TTY];
                tty->termios->c_line = N_TTY;
                if (tty->ldisc.open) {
                        int i = (tty->ldisc.open)(tty);
                        if (i < 0)
                                printk("do_tty_hangup: N_TTY open: error %d\n",
                                       -i);
                }
        }
        
        read_lock(&tasklist_lock);
        for_each_task(p) {
                if ((tty->session > 0) && (p->session == tty->session) &&
                    p->leader) {
                        send_sig(SIGHUP,p,1);
                        send_sig(SIGCONT,p,1);
                        if (tty->pgrp > 0)
                                p->tty_old_pgrp = tty->pgrp;
                }
                if (p->tty == tty)
                        p->tty = NULL;
        }
        read_unlock(&tasklist_lock);

        tty->flags = 0;
        tty->session = 0;
        tty->pgrp = -1;
        tty->ctrl_status = 0;
        if (tty->driver.hangup)
                (tty->driver.hangup)(tty);
        unlock_kernel();
}

void tty_hangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
        char    buf[64];
        
        printk("%s hangup...\n", tty_name(tty, buf));
#endif
        queue_task(&tty->tq_hangup, &tq_scheduler);
}

void tty_vhangup(struct tty_struct * tty)
{
#ifdef TTY_DEBUG_HANGUP
        char    buf[64];

        printk("%s vhangup...\n", tty_name(tty, buf));
#endif
        do_tty_hangup((void *) tty);
}

int tty_hung_up_p(struct file * filp)
{
        return (filp->f_op == &hung_up_tty_fops);
}

/*
 * This function is typically called only by the session leader, when
 * it wants to disassociate itself from its controlling tty.
 *
 * It performs the following functions:
 *      (1)  Sends a SIGHUP and SIGCONT to the foreground process group
 *      (2)  Clears the tty from being controlling the session
 *      (3)  Clears the controlling tty for all processes in the
 *              session group.
 *
 * The argument on_exit is set to 1 if called when a process is
 * exiting; it is 0 if called by the ioctl TIOCNOTTY.
 */
void disassociate_ctty(int on_exit)
{
        struct tty_struct *tty = current->tty;
        struct task_struct *p;
        int tty_pgrp = -1;

        if (tty) {
                tty_pgrp = tty->pgrp;
                if (on_exit && tty->driver.type != TTY_DRIVER_TYPE_PTY)
                        tty_vhangup(tty);
        } else {
                if (current->tty_old_pgrp) {
                        kill_pg(current->tty_old_pgrp, SIGHUP, on_exit);
                        kill_pg(current->tty_old_pgrp, SIGCONT, on_exit);
                }
                return;
        }
        if (tty_pgrp > 0) {
                kill_pg(tty_pgrp, SIGHUP, on_exit);
                if (!on_exit)
                        kill_pg(tty_pgrp, SIGCONT, on_exit);
        }

        current->tty_old_pgrp = 0;
        tty->session = 0;
        tty->pgrp = -1;

        read_lock(&tasklist_lock);
        for_each_task(p)
                if (p->session == current->session)
                        p->tty = NULL;
        read_unlock(&tasklist_lock);
}

void wait_for_keypress(void)
{
        struct console *c = console_drivers;
        if (c) c->wait_key(c);
}

void stop_tty(struct tty_struct *tty)
{
        if (tty->stopped)
                return;
        tty->stopped = 1;
        if (tty->link && tty->link->packet) {
                tty->ctrl_status &= ~TIOCPKT_START;
                tty->ctrl_status |= TIOCPKT_STOP;
                wake_up_interruptible(&tty->link->read_wait);
        }
        if (tty->driver.stop)
                (tty->driver.stop)(tty);
}

void start_tty(struct tty_struct *tty)
{
        if (!tty->stopped || tty->flow_stopped)
                return;
        tty->stopped = 0;
        if (tty->link && tty->link->packet) {
                tty->ctrl_status &= ~TIOCPKT_STOP;
                tty->ctrl_status |= TIOCPKT_START;
                wake_up_interruptible(&tty->link->read_wait);
        }
        if (tty->driver.start)
                (tty->driver.start)(tty);
        if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
            tty->ldisc.write_wakeup)
                (tty->ldisc.write_wakeup)(tty);
        wake_up_interruptible(&tty->write_wait);
}

static ssize_t tty_read(struct file * file, char * buf, size_t count, 
                        loff_t *ppos)
{
        int i;
        struct tty_struct * tty;
        struct inode *inode;

        /* Can't seek (pread) on ttys.  */
        if (ppos != &file->f_pos)
                return -ESPIPE;

        tty = (struct tty_struct *)file->private_data;
        inode = file->f_dentry->d_inode;
        if (tty_paranoia_check(tty, inode->i_rdev, "tty_read"))
                return -EIO;
        if (!tty || (test_bit(TTY_IO_ERROR, &tty->flags)))
                return -EIO;

        /* This check not only needs to be done before reading, but also
           whenever read_chan() gets woken up after sleeping, so I've
           moved it to there.  This should only be done for the N_TTY
           line discipline, anyway.  Same goes for write_chan(). -- jlc. */
#if 0
        if ((inode->i_rdev != CONSOLE_DEV) && /* don't stop on /dev/console */
            (tty->pgrp > 0) &&
            (current->tty == tty) &&
            (tty->pgrp != current->pgrp))
                if (is_ignored(SIGTTIN) || is_orphaned_pgrp(current->pgrp))
                        return -EIO;
                else {
                        (void) kill_pg(current->pgrp, SIGTTIN, 1);
                        return -ERESTARTSYS;
                }
#endif
        if (tty->ldisc.read)
                i = (tty->ldisc.read)(tty,file,buf,count);
        else
                i = -EIO;
        if (i > 0)
                inode->i_atime = CURRENT_TIME;
        return i;
}

/*
 * Split writes up in sane blocksizes to avoid
 * denial-of-service type attacks
 */
static inline ssize_t do_tty_write(
        ssize_t (*write)(struct tty_struct *, struct file *, const unsigned char *, size_t),
        struct tty_struct *tty,
        struct file *file,
        const unsigned char *buf,
        size_t count)
{
        ssize_t ret = 0, written = 0;

        for (;;) {
                unsigned long size = PAGE_SIZE*2;
                if (size > count)
                        size = count;
                ret = write(tty, file, buf, size);
                if (ret <= 0)
                        break;
                written += ret;
                buf += ret;
                count -= ret;
                if (!count)
                        break;
                ret = -ERESTARTSYS;
                if (signal_pending(current))
                        break;
                if (current->need_resched)
                        schedule();
        }
        if (written) {
                file->f_dentry->d_inode->i_mtime = CURRENT_TIME;
                ret = written;
        }
        return ret;
}


static ssize_t tty_write(struct file * file, const char * buf, size_t count,
                         loff_t *ppos)
{
        int is_console;
        struct tty_struct * tty;
        struct inode *inode;

        /* Can't seek (pwrite) on ttys.  */
        if (ppos != &file->f_pos)
                return -ESPIPE;

        /*
         *      For now, we redirect writes from /dev/console as
         *      well as /dev/tty0.
         */
        inode = file->f_dentry->d_inode;
        is_console = (inode->i_rdev == SYSCONS_DEV ||
                      inode->i_rdev == CONSOLE_DEV);

        if (is_console && redirect)
                tty = redirect;
        else
                tty = (struct tty_struct *)file->private_data;
        if (tty_paranoia_check(tty, inode->i_rdev, "tty_write"))
                return -EIO;
        if (!tty || !tty->driver.write || (test_bit(TTY_IO_ERROR, &tty->flags)))
                return -EIO;
#if 0
        if (!is_console && L_TOSTOP(tty) && (tty->pgrp > 0) &&
            (current->tty == tty) && (tty->pgrp != current->pgrp)) {
                if (is_orphaned_pgrp(current->pgrp))
                        return -EIO;
                if (!is_ignored(SIGTTOU)) {
                        (void) kill_pg(current->pgrp, SIGTTOU, 1);
                        return -ERESTARTSYS;
                }
        }
#endif
        if (!tty->ldisc.write)
                return -EIO;
        return do_tty_write(tty->ldisc.write, tty, file,
                            (const unsigned char *)buf, count);
}

/* Semaphore to protect creating and releasing a tty */
static struct semaphore tty_sem = MUTEX;

static void down_tty_sem(int index)
{
        down(&tty_sem);
}

static void up_tty_sem(int index)
{
        up(&tty_sem);
}

static void release_mem(struct tty_struct *tty, int idx);

/*
 * WSH 06/09/97: Rewritten to remove races and properly clean up after a
 * failed open.  The new code protects the open with a semaphore, so it's
 * really quite straightforward.  The semaphore locking can probably be
 * relaxed for the (most common) case of reopening a tty.
 */
static int init_dev(kdev_t device, struct tty_struct **ret_tty)
{
        struct tty_struct *tty, *o_tty;
        struct termios *tp, **tp_loc, *o_tp, **o_tp_loc;
        struct termios *ltp, **ltp_loc, *o_ltp, **o_ltp_loc;
        struct tty_driver *driver;      
        int retval=0;
        int idx;

        driver = get_tty_driver(device);
        if (!driver)
                return -ENODEV;

        idx = MINOR(device) - driver->minor_start;

        /* 
         * Check whether we need to acquire the tty semaphore to avoid
         * race conditions.  For now, play it safe.
         */
        down_tty_sem(idx);

        /* check whether we're reopening an existing tty */
        tty = driver->table[idx];
        if (tty) goto fast_track;

        /*
         * First time open is complex, especially for PTY devices.
         * This code guarantees that either everything succeeds and the
         * TTY is ready for operation, or else the table slots are vacated
         * and the allocated memory released.  (Except that the termios 
         * and locked termios may be retained.)
         */

        o_tty = NULL;
        tp = o_tp = NULL;
        ltp = o_ltp = NULL;

        tty = (struct tty_struct*) get_free_page(GFP_KERNEL);
        if(!tty)
                goto fail_no_mem;
        initialize_tty_struct(tty);
        tty->device = device;
        tty->driver = *driver;

        tp_loc = &driver->termios[idx];
        if (!*tp_loc) {
                tp = (struct termios *) kmalloc(sizeof(struct termios),
                                                GFP_KERNEL);
                if (!tp)
                        goto free_mem_out;
                *tp = driver->init_termios;
        }

        ltp_loc = &driver->termios_locked[idx];
        if (!*ltp_loc) {
                ltp = (struct termios *) kmalloc(sizeof(struct termios),
                                                 GFP_KERNEL);
                if (!ltp)
                        goto free_mem_out;
                memset(ltp, 0, sizeof(struct termios));
        }

        if (driver->type == TTY_DRIVER_TYPE_PTY) {
                o_tty = (struct tty_struct *) get_free_page(GFP_KERNEL);
                if (!o_tty)
                        goto free_mem_out;
                initialize_tty_struct(o_tty);
                o_tty->device = (kdev_t) MKDEV(driver->other->major,
                                        driver->other->minor_start + idx);
                o_tty->driver = *driver->other;

                o_tp_loc  = &driver->other->termios[idx];
                if (!*o_tp_loc) {
                        o_tp = (struct termios *)
                                kmalloc(sizeof(struct termios), GFP_KERNEL);
                        if (!o_tp)
                                goto free_mem_out;
                        *o_tp = driver->other->init_termios;
                }

                o_ltp_loc = &driver->other->termios_locked[idx];
                if (!*o_ltp_loc) {
                        o_ltp = (struct termios *)
                                kmalloc(sizeof(struct termios), GFP_KERNEL);
                        if (!o_ltp)
                                goto free_mem_out;
                        memset(o_ltp, 0, sizeof(struct termios));
                }

                /*
                 * Everything allocated ... set up the o_tty structure.
                 */
                driver->other->table[idx] = o_tty;
                if (!*o_tp_loc)
                        *o_tp_loc = o_tp;
                if (!*o_ltp_loc)
                        *o_ltp_loc = o_ltp;
                o_tty->termios = *o_tp_loc;
                o_tty->termios_locked = *o_ltp_loc;
                (*driver->other->refcount)++;
                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_mem to clean up, so 
         * there's no need to null out the local pointers.
         */
        driver->table[idx] = tty;
        if (!*tp_loc)
                *tp_loc = tp;
        if (!*ltp_loc)
                *ltp_loc = ltp;
        tty->termios = *tp_loc;
        tty->termios_locked = *ltp_loc;
        (*driver->refcount)++;
        tty->count++;

        /* 
         * Structures all installed ... call the ldisc open routines.
         * If we fail here just call release_mem to clean up.  No need
         * to decrement the use counts, as release_mem doesn't care.
         */
        if (tty->ldisc.open) {
                retval = (tty->ldisc.open)(tty);
                if (retval)
                        goto release_mem_out;
        }
        if (o_tty && o_tty->ldisc.open) {
                retval = (o_tty->ldisc.open)(o_tty);
                if (retval) {
                        if (tty->ldisc.close)
                                (tty->ldisc.close)(tty);
                        goto release_mem_out;
                }
        }
        goto success;

        /*
         * This fast open can be used if the tty is already open.
         * No memory is allocated, and the only failures are from
         * attempting to open a closing tty or attempting multiple
         * opens on a pty master.
         */
fast_track:
        if (test_bit(TTY_CLOSING, &tty->flags)) {
                retval = -EIO;
                goto end_init;
        }
        if (driver->type == TTY_DRIVER_TYPE_PTY &&
            driver->subtype == PTY_TYPE_MASTER) {
                /*
                 * special case for PTY masters: only one open permitted, 
                 * and the slave side open count is incremented as well.
                 */
                if (tty->count) {
                        retval = -EIO;
                        goto end_init;
                }
                tty->link->count++;
        }
        tty->count++;
        tty->driver = *driver; /* N.B. why do this every time?? */

success:
        *ret_tty = tty;
        
        /* All paths come through here to release the semaphore */
end_init:
        up_tty_sem(idx);
        return retval;

        /* Release locally allocated memory ... nothing placed in slots */
free_mem_out:
        if (o_tp)
                kfree_s(o_tp, sizeof(struct termios));
        if (o_tty)
                free_page((unsigned long) o_tty);
        if (ltp)
                kfree_s(ltp, sizeof(struct termios));
        if (tp)
                kfree_s(tp, sizeof(struct termios));
        free_page((unsigned long) tty);

fail_no_mem:
        retval = -ENOMEM;
        goto end_init;

        /* call the tty release_mem routine to clean out this slot */
release_mem_out:
        printk("init_dev: ldisc open failed, clearing slot %d\n", idx);
        release_mem(tty, idx);
        goto end_init;
}

/*
 * Releases memory associated with a tty structure, and clears out the
 * driver table slots.
 */
static void release_mem(struct tty_struct *tty, int idx)
{
        struct tty_struct *o_tty;
        struct termios *tp;

        if ((o_tty = tty->link) != NULL) {
                o_tty->driver.table[idx] = NULL;
                if (o_tty->driver.flags & TTY_DRIVER_RESET_TERMIOS) {
                        tp = o_tty->driver.termios[idx];
                        o_tty->driver.termios[idx] = NULL;
                        kfree_s(tp, sizeof(struct termios));
                }
                o_tty->magic = 0;
                (*o_tty->driver.refcount)--;
                free_page((unsigned long) o_tty);
        }

        tty->driver.table[idx] = NULL;
        if (tty->driver.flags & TTY_DRIVER_RESET_TERMIOS) {
                tp = tty->driver.termios[idx];
                tty->driver.termios[idx] = NULL;
                kfree_s(tp, sizeof(struct termios));
        }
        tty->magic = 0;
        (*tty->driver.refcount)--;
        free_page((unsigned long) tty);
}

/*
 * Even releasing the tty structures is a tricky business.. We have
 * to be very careful that the structures are all released at the
 * same time, as interrupts might otherwise get the wrong pointers.
 *
 * WSH 09/09/97: rewritten to avoid some nasty race conditions that could
 * lead to double frees or releasing memory still in use.
 */
static void release_dev(struct file * filp)
{
        struct tty_struct *tty, *o_tty;
        int     pty_master, tty_closing, o_tty_closing, do_sleep;
        int     idx;
        char    buf[64];
        
        tty = (struct tty_struct *)filp->private_data;
        if (tty_paranoia_check(tty, filp->f_dentry->d_inode->i_rdev, "release_dev"))
                return;

        check_tty_count(tty, "release_dev");

        tty_fasync(-1, filp, 0);

        idx = MINOR(tty->device) - tty->driver.minor_start;
        pty_master = (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
                      tty->driver.subtype == PTY_TYPE_MASTER);
        o_tty = tty->link;

#ifdef TTY_PARANOIA_CHECK
        if (idx < 0 || idx >= tty->driver.num) {
                printk("release_dev: bad idx when trying to free (%s)\n",
                       kdevname(tty->device));
                return;
        }
        if (tty != tty->driver.table[idx]) {
                printk("release_dev: driver.table[%d] not tty for (%s)\n",
                       idx, kdevname(tty->device));
                return;
        }
        if (tty->termios != tty->driver.termios[idx]) {
                printk("release_dev: driver.termios[%d] not termios "
                       "for (%s)\n",
                       idx, kdevname(tty->device));
                return;
        }
        if (tty->termios_locked != tty->driver.termios_locked[idx]) {
                printk("release_dev: driver.termios_locked[%d] not "
                       "termios_locked for (%s)\n",
                       idx, kdevname(tty->device));
                return;
        }
#endif

#ifdef TTY_DEBUG_HANGUP
        printk("release_dev of %s (tty count=%d)...", tty_name(tty, buf),
               tty->count);
#endif

#ifdef TTY_PARANOIA_CHECK
        if (tty->driver.other) {
                if (o_tty != tty->driver.other->table[idx]) {
                        printk("release_dev: other->table[%d] not o_tty for ("
                               "%s)\n",
                               idx, kdevname(tty->device));
                        return;
                }
                if (o_tty->termios != tty->driver.other->termios[idx]) {
                        printk("release_dev: other->termios[%d] not o_termios "
                               "for (%s)\n",
                               idx, kdevname(tty->device));
                        return;
                }
                if (o_tty->termios_locked != 
                      tty->driver.other->termios_locked[idx]) {
                        printk("release_dev: other->termios_locked[%d] not "
                               "o_termios_locked for (%s)\n",
                               idx, kdevname(tty->device));
                        return;
                }
                if (o_tty->link != tty) {
                        printk("release_dev: bad pty pointers\n");
                        return;
                }
        }
#endif

        if (tty->driver.close)
                tty->driver.close(tty, filp);

        /*
         * Sanity check: if tty->count is going to zero, there shouldn't be
         * any waiters on tty->read_wait or tty->write_wait.  We test the
         * wait queues and kick everyone out _before_ actually starting to
         * close.  This ensures that we won't block while releasing the tty
         * structure.
         *
         * The test for the o_tty closing is necessary, since the master and
         * slave sides may close in any order.  If the slave side closes out
         * first, its count will be one, since the master side holds an open.
         * Thus this test wouldn't be triggered at the time the slave closes,
         * so we do it now.
         *
         * Note that it's possible for the tty to be opened again while we're
         * flushing out waiters.  By recalculating the closing flags before
         * each iteration we avoid any problems.
         */
        while (1) {
                tty_closing = tty->count <= 1;
                o_tty_closing = o_tty &&
                        (o_tty->count <= (pty_master ? 1 : 0));
                do_sleep = 0;

                if (tty_closing) {
                        if (waitqueue_active(&tty->read_wait)) {
                                wake_up(&tty->read_wait);
                                do_sleep++;
                        }
                        if (waitqueue_active(&tty->write_wait)) {
                                wake_up(&tty->write_wait);
                                do_sleep++;
                        }
                }
                if (o_tty_closing) {
                        if (waitqueue_active(&o_tty->read_wait)) {
                                wake_up(&o_tty->read_wait);
                                do_sleep++;
                        }
                        if (waitqueue_active(&o_tty->write_wait)) {
                                wake_up(&o_tty->write_wait);
                                do_sleep++;
                        }
                }
                if (!do_sleep)
                        break;

                printk("release_dev: %s: read/write wait queue active!\n",
                       tty_name(tty, buf));
                schedule();
        }       

        /*
         * The closing flags are now consistent with the open counts on 
         * both sides, and we've completed the last operation that could 
         * block, so it's safe to proceed with closing.
         */

        if (pty_master) {
                if (--o_tty->count < 0) {
                        printk("release_dev: bad pty slave count (%d) for %s\n",
                               o_tty->count, tty_name(o_tty, buf));
                        o_tty->count = 0;
                }
        }
        if (--tty->count < 0) {
                printk("release_dev: bad tty->count (%d) for %s\n",
                       tty->count, tty_name(tty, buf));
                tty->count = 0;
        }

        /*
         * Perform some housekeeping before deciding whether to return.
         *
         * Set the TTY_CLOSING flag if this was the last open.  In the
         * case of a pty we may have to wait around for the other side
         * to close, and TTY_CLOSING makes sure we can't be reopened.
         */
        if(tty_closing)
                set_bit(TTY_CLOSING, &tty->flags);
        if(o_tty_closing)
                set_bit(TTY_CLOSING, &o_tty->flags);

        /*
         * If _either_ side is closing, make sure there aren't any
         * processes that still think tty or o_tty is their controlling
         * tty.  Also, clear redirect if it points to either tty.
         */
        if (tty_closing || o_tty_closing) {
                struct task_struct *p;

                read_lock(&tasklist_lock);
                for_each_task(p) {
                        if (p->tty == tty || (o_tty && p->tty == o_tty))
                                p->tty = NULL;
                }
                read_unlock(&tasklist_lock);

                if (redirect == tty || (o_tty && redirect == o_tty))
                        redirect = NULL;
        }

        /* check whether both sides are closing ... */
        if (!tty_closing || (o_tty && !o_tty_closing))
                return;
        filp->private_data = 0;
        
#ifdef TTY_DEBUG_HANGUP
        printk("freeing tty structure...");
#endif

        /*
         * Shutdown the current line discipline, and reset it to N_TTY.
         * N.B. why reset ldisc when we're releasing the memory??
         */
        if (tty->ldisc.close)
                (tty->ldisc.close)(tty);
        tty->ldisc = ldiscs[N_TTY];
        tty->termios->c_line = N_TTY;
        if (o_tty) {
                if (o_tty->ldisc.close)
                        (o_tty->ldisc.close)(o_tty);
                o_tty->ldisc = ldiscs[N_TTY];
        }
        
        /*
         * Make sure that the tty's task queue isn't activated. 
         */
        run_task_queue(&tq_timer);
        run_task_queue(&tq_scheduler);

        /* 
         * The release_mem function takes care of the details of clearing
         * the slots and preserving the termios structure.
         */
        release_mem(tty, idx);
}

/*
 * tty_open and tty_release keep up the tty count that contains the
 * number of opens done on a tty. We cannot use the inode-count, as
 * different inodes might point to the same tty.
 *
 * Open-counting is needed for pty masters, as well as for keeping
 * track of serial lines: DTR is dropped when the last close happens.
 * (This is not done solely through tty->count, now.  - Ted 1/27/92)
 *
 * The termios state of a pty is reset on first open so that
 * settings don't persist across reuse.
 */
static int tty_open(struct inode * inode, struct file * filp)
{
        struct tty_struct *tty;
        int noctty, retval;
        kdev_t device;
        unsigned short saved_flags;
        char    buf[64];

        saved_flags = filp->f_flags;
retry_open:
        noctty = filp->f_flags & O_NOCTTY;
        device = inode->i_rdev;
        if (device == TTY_DEV) {
                if (!current->tty)
                        return -ENXIO;
                device = current->tty->device;
                filp->f_flags |= O_NONBLOCK; /* Don't let /dev/tty block */
                /* noctty = 1; */
        }
#ifdef CONFIG_VT
        if (device == CONSOLE_DEV) {
                extern int fg_console;
                device = MKDEV(TTY_MAJOR, fg_console + 1);
                noctty = 1;
        }
#endif
        if (device == SYSCONS_DEV) {
                struct console *c = console_drivers;
                while(c && !c->device)
                        c = c->next;
                if (!c)
                        return -ENODEV;
                device = c->device(c);
                noctty = 1;
        }
#ifdef CONFIG_UNIX98_PTYS
        if (device == PTMX_DEV) {
                /* find a free pty. */
                int major, minor;
                struct tty_driver *driver;

                /* find a device that is not in use. */
                retval = -1;
                for ( major = 0 ; major < UNIX98_NR_MAJORS ; major++ ) {
                        driver = &ptm_driver[major];
                        for (minor = driver->minor_start ;
                             minor < driver->minor_start + driver->num ;
                             minor++) {
                                device = MKDEV(driver->major, minor);
                                if (!init_dev(device, &tty)) goto ptmx_found; /* ok! */
                        }
                }
                return -EIO; /* no free ptys */
        ptmx_found:
                set_bit(TTY_PTY_LOCK, &tty->flags); /* LOCK THE SLAVE */
                minor -= driver->minor_start;
                devpts_pty_new(driver->other->name_base + minor, MKDEV(driver->other->major, minor + driver->other->minor_start));
                noctty = 1;
                goto init_dev_done;
        }
#endif
        
        retval = init_dev(device, &tty);
        if (retval)
                return retval;

        /* N.B. this error exit may leave filp->f_flags with O_NONBLOCK set */
init_dev_done:
        filp->private_data = tty;
        check_tty_count(tty, "tty_open");
        if (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
            tty->driver.subtype == PTY_TYPE_MASTER)
                noctty = 1;
#ifdef TTY_DEBUG_HANGUP
        printk("opening %s...", tty_name(tty, buf));
#endif
        if (tty->driver.open)
                retval = tty->driver.open(tty, filp);
        else
                retval = -ENODEV;
        filp->f_flags = saved_flags;

        if (!retval && test_bit(TTY_EXCLUSIVE, &tty->flags) && !suser())
                retval = -EBUSY;

        if (retval) {
#ifdef TTY_DEBUG_HANGUP
                printk("error %d in opening %s...", retval,
                       tty_name(tty, buf));
#endif

                release_dev(filp);
                if (retval != -ERESTARTSYS)
                        return retval;
                if (signal_pending(current))
                        return retval;
                schedule();
                /*
                 * Need to reset f_op in case a hangup happened.
                 */
                filp->f_op = &tty_fops;
                goto retry_open;
        }
        if (!noctty &&
            current->leader &&
            !current->tty &&
            tty->session == 0) {
                current->tty = tty;
                current->tty_old_pgrp = 0;
                tty->session = current->session;
                tty->pgrp = current->pgrp;
        }
        if ((tty->driver.type == TTY_DRIVER_TYPE_SERIAL) &&
            (tty->driver.subtype == SERIAL_TYPE_CALLOUT) &&
            (tty->count == 1)) {
                static int nr_warns = 0;
                if (nr_warns < 5) {
                        printk(KERN_WARNING "tty_io.c: "
                                "process %d (%s) used obsolete /dev/%s - " 
                                "update software to use /dev/ttyS%d\n",
                                current->pid, current->comm, 
                                tty_name(tty, buf), TTY_NUMBER(tty));
                        nr_warns++;
                }
        }
        return 0;
}

static int tty_release(struct inode * inode, struct file * filp)
{
        release_dev(filp);
        return 0;
}

static unsigned int tty_poll(struct file * filp, poll_table * wait)
{
        struct tty_struct * tty;

        tty = (struct tty_struct *)filp->private_data;
        if (tty_paranoia_check(tty, filp->f_dentry->d_inode->i_rdev, "tty_poll"))
                return 0;

        if (tty->ldisc.poll)
                return (tty->ldisc.poll)(tty, filp, wait);
        return 0;
}

/*
 * fasync_helper() is used by some character device drivers (mainly mice)
 * to set up the fasync queue. It returns negative on error, 0 if it did
 * no changes and positive if it added/deleted the entry.
 */
int fasync_helper(int fd, struct file * filp, int on, struct fasync_struct **fapp)
{
        struct fasync_struct *fa, **fp;
        unsigned long flags;

        for (fp = fapp; (fa = *fp) != NULL; fp = &fa->fa_next) {
                if (fa->fa_file == filp)
                        break;
        }

        if (on) {
                if (fa) {
                        fa->fa_fd = fd;
                        return 0;
                }
                fa = (struct fasync_struct *)kmalloc(sizeof(struct fasync_struct), GFP_KERNEL);
                if (!fa)
                        return -ENOMEM;
                fa->magic = FASYNC_MAGIC;
                fa->fa_file = filp;
                fa->fa_fd = fd;
                save_flags(flags);
                cli();
                fa->fa_next = *fapp;
                *fapp = fa;
                restore_flags(flags);
                return 1;
        }
        if (!fa)
                return 0;
        save_flags(flags);
        cli();
        *fp = fa->fa_next;
        restore_flags(flags);
        kfree(fa);
        return 1;
}

static int tty_fasync(int fd, struct file * filp, int on)
{
        struct tty_struct * tty;
        int retval;

        tty = (struct tty_struct *)filp->private_data;
        if (tty_paranoia_check(tty, filp->f_dentry->d_inode->i_rdev, "tty_fasync"))
                return 0;
        
        retval = fasync_helper(fd, filp, on, &tty->fasync);
        if (retval <= 0)
                return retval;

        if (on) {
                if (!waitqueue_active(&tty->read_wait))
                        tty->minimum_to_wake = 1;
                if (filp->f_owner.pid == 0) {
                        filp->f_owner.pid = (-tty->pgrp) ? : current->pid;
                        filp->f_owner.uid = current->uid;
                        filp->f_owner.euid = current->euid;
                }
        } else {
                if (!tty->fasync && !waitqueue_active(&tty->read_wait))
                        tty->minimum_to_wake = N_TTY_BUF_SIZE;
        }
        return 0;
}

static int tiocsti(struct tty_struct *tty, char * arg)
{
        char ch, mbz = 0;

        if ((current->tty != tty) && !suser())
                return -EPERM;
        if (get_user(ch, arg))
                return -EFAULT;
        tty->ldisc.receive_buf(tty, &ch, &mbz, 1);
        return 0;
}

static int tiocgwinsz(struct tty_struct *tty, struct winsize * arg)
{
        if (copy_to_user(arg, &tty->winsize, sizeof(*arg)))
                return -EFAULT;
        return 0;
}

static int tiocswinsz(struct tty_struct *tty, struct tty_struct *real_tty,
        struct winsize * arg)
{
        struct winsize tmp_ws;

        if (copy_from_user(&tmp_ws, arg, sizeof(*arg)))
                return -EFAULT;
        if (!memcmp(&tmp_ws, &tty->winsize, sizeof(*arg)))
                return 0;
        if (tty->pgrp > 0)
                kill_pg(tty->pgrp, SIGWINCH, 1);
        if ((real_tty->pgrp != tty->pgrp) && (real_tty->pgrp > 0))
                kill_pg(real_tty->pgrp, SIGWINCH, 1);
        tty->winsize = tmp_ws;
        real_tty->winsize = tmp_ws;
        return 0;
}

static int tioccons(struct tty_struct *tty, struct tty_struct *real_tty)
{
        if (tty->driver.type == TTY_DRIVER_TYPE_CONSOLE ||
            tty->driver.type == TTY_DRIVER_TYPE_SYSCONS) {
                if (!suser())
                        return -EPERM;
                redirect = NULL;
                return 0;
        }
        if (redirect)
                return -EBUSY;
        redirect = real_tty;
        return 0;
}


static int fionbio(struct file *file, int *arg)
{
        int nonblock;

        if (get_user(nonblock, arg))
                return -EFAULT;

        if (nonblock)
                file->f_flags |= O_NONBLOCK;
        else
                file->f_flags &= ~O_NONBLOCK;
        return 0;
}

static int tiocsctty(struct tty_struct *tty, int arg)
{
        if (current->leader &&
            (current->session == tty->session))
                return 0;
        /*
         * The process must be a session leader and
         * not have a controlling tty already.
         */
        if (!current->leader || current->tty)
                return -EPERM;
        if (tty->session > 0) {
                /*
                 * This tty is already the controlling
                 * tty for another session group!
                 */
                if ((arg == 1) && suser()) {
                        /*
                         * Steal it away
                         */
                        struct task_struct *p;

                        read_lock(&tasklist_lock);
                        for_each_task(p)
                                if (p->tty == tty)
                                        p->tty = NULL;
                        read_unlock(&tasklist_lock);
                } else
                        return -EPERM;
        }
        current->tty = tty;
        current->tty_old_pgrp = 0;
        tty->session = current->session;
        tty->pgrp = current->pgrp;
        return 0;
}

static int tiocgpgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t *arg)
{
        /*
         * (tty == real_tty) is a cheap way of
         * testing if the tty is NOT a master pty.
         */
        if (tty == real_tty && current->tty != real_tty)
                return -ENOTTY;
        return put_user(real_tty->pgrp, arg);
}

static int tiocspgrp(struct tty_struct *tty, struct tty_struct *real_tty, pid_t *arg)
{
        pid_t pgrp;
        int retval = tty_check_change(real_tty);

        if (retval == -EIO)
                return -ENOTTY;
        if (retval)
                return retval;
        if (!current->tty ||
            (current->tty != real_tty) ||
            (real_tty->session != current->session))
                return -ENOTTY;
        get_user(pgrp, (pid_t *) arg);
        if (pgrp < 0)
                return -EINVAL;
        if (session_of_pgrp(pgrp) != current->session)
                return -EPERM;
        real_tty->pgrp = pgrp;
        return 0;
}

static int tiocgsid(struct tty_struct *tty, struct tty_struct *real_tty, pid_t *arg)
{
        /*
         * (tty == real_tty) is a cheap way of
         * testing if the tty is NOT a master pty.
        */
        if (tty == real_tty && current->tty != real_tty)
                return -ENOTTY;
        if (real_tty->session <= 0)
                return -ENOTTY;
        return put_user(real_tty->session, arg);
}

static int tiocttygstruct(struct tty_struct *tty, struct tty_struct *arg)
{
        if (copy_to_user(arg, tty, sizeof(*arg)))
                return -EFAULT;
        return 0;
}

static int tiocsetd(struct tty_struct *tty, int *arg)
{
        int retval, ldisc;

        retval = get_user(ldisc, arg);
        if (retval)
                return retval;
        return tty_set_ldisc(tty, ldisc);
}

static int send_break(struct tty_struct *tty, int duration)
{
        current->state = TASK_INTERRUPTIBLE;
        current->timeout = jiffies + duration;

        tty->driver.break_ctl(tty, -1);
        if (!signal_pending(current))
                schedule();
        tty->driver.break_ctl(tty, 0);
        if (signal_pending(current))
                return -EINTR;
        return 0;
}

/*
 * Split this up, as gcc can choke on it otherwise..
 */
static int tty_ioctl(struct inode * inode, struct file * file,
                     unsigned int cmd, unsigned long arg)
{
        struct tty_struct *tty, *real_tty;
        int retval;
        
        tty = (struct tty_struct *)file->private_data;
        if (tty_paranoia_check(tty, inode->i_rdev, "tty_ioctl"))
                return -EINVAL;

        real_tty = tty;
        if (tty->driver.type == TTY_DRIVER_TYPE_PTY &&
            tty->driver.subtype == PTY_TYPE_MASTER)
                real_tty = tty->link;

        /*
         * Break handling by driver
         */
        if (!tty->driver.break_ctl) {
                switch(cmd) {
                case TIOCSBRK:
                case TIOCCBRK:
                        if (tty->driver.ioctl)
                                return tty->driver.ioctl(tty, file, cmd, arg);
                        return -EINVAL;
                        
                /* These two ioctl's always return success; even if */
                /* the driver doesn't support them. */
                case TCSBRK:
                case TCSBRKP:
                        if (!tty->driver.ioctl)
                                return 0;
                        retval = tty->driver.ioctl(tty, file, cmd, arg);
                        if (retval == -ENOIOCTLCMD)
                                retval = 0;
                        return retval;
                }
        }

        /*
         * Factor out some common prep work
         */
        switch (cmd) {
        case TIOCSETD:
        case TIOCSBRK:
        case TIOCCBRK:
        case TCSBRK:
        case TCSBRKP:                   
                retval = tty_check_change(tty);
                if (retval)
                        return retval;
                if (cmd != TIOCCBRK) {
                        tty_wait_until_sent(tty, 0);
                        if (signal_pending(current))
                                return -EINTR;
                }
                break;
        }

        switch (cmd) {
                case TIOCSTI:
                        return tiocsti(tty, (char *)arg);
                case TIOCGWINSZ:
                        return tiocgwinsz(tty, (struct winsize *) arg);
                case TIOCSWINSZ:
                        return tiocswinsz(tty, real_tty, (struct winsize *) arg);
                case TIOCCONS:
                        return tioccons(tty, real_tty);
                case FIONBIO:
                        return fionbio(file, (int *) arg);
                case TIOCEXCL:
                        set_bit(TTY_EXCLUSIVE, &tty->flags);
                        return 0;
                case TIOCNXCL:
                        clear_bit(TTY_EXCLUSIVE, &tty->flags);
                        return 0;
                case TIOCNOTTY:
                        if (current->tty != tty)
                                return -ENOTTY;
                        if (current->leader)
                                disassociate_ctty(0);
                        current->tty = NULL;
                        return 0;
                case TIOCSCTTY:
                        return tiocsctty(tty, arg);
                case TIOCGPGRP:
                        return tiocgpgrp(tty, real_tty, (pid_t *) arg);
                case TIOCSPGRP:
                        return tiocspgrp(tty, real_tty, (pid_t *) arg);
                case TIOCGSID:
                        return tiocgsid(tty, real_tty, (pid_t *) arg);
                case TIOCGETD:
                        return put_user(tty->ldisc.num, (int *) arg);
                case TIOCSETD:
                        return tiocsetd(tty, (int *) arg);
#ifdef CONFIG_VT
                case TIOCLINUX:
                        return tioclinux(tty, arg);
#endif
                case TIOCTTYGSTRUCT:
                        return tiocttygstruct(tty, (struct tty_struct *) arg);

                /*
                 * Break handling
                 */
                case TIOCSBRK:  /* Turn break on, unconditionally */
                        tty->driver.break_ctl(tty, -1);
                        return 0;
                        
                case TIOCCBRK:  /* Turn break off, unconditionally */
                        tty->driver.break_ctl(tty, 0);
                        return 0;
                case TCSBRK:   /* SVID version: non-zero arg --> no break */
                        /*
                         * XXX is the above comment correct, or the
                         * code below correct?  Is this ioctl used at
                         * all by anyone?
                         */
                        if (!arg)
                                return send_break(tty, HZ/4);
                        return 0;
                case TCSBRKP:   /* support for POSIX tcsendbreak() */   
                        return send_break(tty, arg ? arg*(HZ/10) : HZ/4);
        }
        if (tty->driver.ioctl) {
                int retval = (tty->driver.ioctl)(tty, file, cmd, arg);
                if (retval != -ENOIOCTLCMD)
                        return retval;
        }
        if (tty->ldisc.ioctl) {
                int retval = (tty->ldisc.ioctl)(tty, file, cmd, arg);
                if (retval != -ENOIOCTLCMD)
                        return retval;
        }
        return -EINVAL;
}


/*
 * This implements the "Secure Attention Key" ---  the idea is to
 * prevent trojan horses by killing all processes associated with this
 * tty when the user hits the "Secure Attention Key".  Required for
 * super-paranoid applications --- see the Orange Book for more details.
 * 
 * This code could be nicer; ideally it should send a HUP, wait a few
 * seconds, then send a INT, and then a KILL signal.  But you then
 * have to coordinate with the init process, since all processes associated
 * with the current tty must be dead before the new getty is allowed
 * to spawn.
 */
void do_SAK( struct tty_struct *tty)
{
#ifdef TTY_SOFT_SAK
        tty_hangup(tty);
#else
        struct task_struct *p;
        int session;
        int             i;
        struct file     *filp;
        
        if (!tty)
                return;
        session  = tty->session;
        if (tty->ldisc.flush_buffer)
                tty->ldisc.flush_buffer(tty);
        if (tty->driver.flush_buffer)
                tty->driver.flush_buffer(tty);
        read_lock(&tasklist_lock);
        for_each_task(p) {
                if ((p->tty == tty) ||
                    ((session > 0) && (p->session == session)))
                        send_sig(SIGKILL, p, 1);
                else if (p->files) {
                        for (i=0; i < p->files->max_fds; i++) {
                                filp = fcheck_task(p, i);
                                if (filp && (filp->f_op == &tty_fops) &&
                                    (filp->private_data == tty)) {
                                        send_sig(SIGKILL, p, 1);
                                        break;
                                }
                        }
                }
        }
        read_unlock(&tasklist_lock);
#endif
}

/*
 * This routine is called out of the software interrupt to flush data
 * from the flip buffer to the line discipline.
 */
static void flush_to_ldisc(void *private_)
{
        struct tty_struct *tty = (struct tty_struct *) private_;
        unsigned char   *cp;
        char            *fp;
        int             count;
        unsigned long flags;

        if (tty->flip.buf_num) {
                cp = tty->flip.char_buf + TTY_FLIPBUF_SIZE;
                fp = tty->flip.flag_buf + TTY_FLIPBUF_SIZE;
                tty->flip.buf_num = 0;

                save_flags(flags); cli();
                tty->flip.char_buf_ptr = tty->flip.char_buf;
                tty->flip.flag_buf_ptr = tty->flip.flag_buf;
        } else {
                cp = tty->flip.char_buf;
                fp = tty->flip.flag_buf;
                tty->flip.buf_num = 1;

                save_flags(flags); cli();
                tty->flip.char_buf_ptr = tty->flip.char_buf + TTY_FLIPBUF_SIZE;
                tty->flip.flag_buf_ptr = tty->flip.flag_buf + TTY_FLIPBUF_SIZE;
        }
        count = tty->flip.count;
        tty->flip.count = 0;
        restore_flags(flags);
        
        tty->ldisc.receive_buf(tty, cp, fp, count);
}

/*
 * Routine which returns the baud rate of the tty
 */

/*
 * This is used to figure out the divisor speeds and the timeouts
 */
static int baud_table[] = {
        0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
        9600, 19200, 38400, 57600, 115200, 230400, 460800, 0 };

int tty_get_baud_rate(struct tty_struct *tty)
{
        unsigned int cflag, i;

        cflag = tty->termios->c_cflag;

        i = cflag & CBAUD;
        if (i & CBAUDEX) {
                i &= ~CBAUDEX;
                if (i < 1 || i > 4) 
                        tty->termios->c_cflag &= ~CBAUDEX;
                else
                        i += 15;
        }
        if (i==15 && tty->alt_speed) {
                if (!tty->warned) {
                        printk("Use of setserial/setrocket to set SPD_* flags is deprecated\n");
                        tty->warned = 1;
                }
                return(tty->alt_speed);
        }
        
        return baud_table[i];
}

void tty_flip_buffer_push(struct tty_struct *tty)
{
        if (tty->low_latency)
                flush_to_ldisc((void *) tty);
        else
                queue_task(&tty->flip.tqueue, &tq_timer);
}

/*
 * This subroutine initializes a tty structure.
 */
static void initialize_tty_struct(struct tty_struct *tty)
{
        memset(tty, 0, sizeof(struct tty_struct));
        tty->magic = TTY_MAGIC;
        tty->ldisc = ldiscs[N_TTY];
        tty->pgrp = -1;
        tty->flip.char_buf_ptr = tty->flip.char_buf;
        tty->flip.flag_buf_ptr = tty->flip.flag_buf;
        tty->flip.tqueue.routine = flush_to_ldisc;
        tty->flip.tqueue.data = tty;
        tty->flip.pty_sem = MUTEX;
        tty->tq_hangup.routine = do_tty_hangup;
        tty->tq_hangup.data = tty;
}

/*
 * The default put_char routine if the driver did not define one.
 */
void tty_default_put_char(struct tty_struct *tty, unsigned char ch)
{
        tty->driver.write(tty, 0, &ch, 1);
}

/*
 * Called by a tty driver to register itself.
 */
int tty_register_driver(struct tty_driver *driver)
{
        int error;

        if (driver->flags & TTY_DRIVER_INSTALLED)
                return 0;

        error = register_chrdev(driver->major, driver->name, &tty_fops);
        if (error < 0)
                return error;
        else if(driver->major == 0)
                driver->major = error;

        if (!driver->put_char)
                driver->put_char = tty_default_put_char;
        
        driver->prev = 0;
        driver->next = tty_drivers;
        if (tty_drivers) tty_drivers->prev = driver;
        tty_drivers = driver;
        
#ifdef CONFIG_PROC_FS
        proc_tty_register_driver(driver);
#endif  
        return error;
}

/*
 * Called by a tty driver to unregister itself.
 */
int tty_unregister_driver(struct tty_driver *driver)
{
        int     retval;
        struct tty_driver *p;
        int     found = 0;
        const char *othername = NULL;
        
        if (*driver->refcount)
                return -EBUSY;

        for (p = tty_drivers; p; p = p->next) {
                if (p == driver)
                        found++;
                else if (p->major == driver->major)
                        othername = p->name;
        }
        
        if (!found)
                return -ENOENT;

        if (othername == NULL) {
                retval = unregister_chrdev(driver->major, driver->name);
                if (retval)
                        return retval;
        } else
                register_chrdev(driver->major, othername, &tty_fops);

        if (driver->prev)
                driver->prev->next = driver->next;
        else
                tty_drivers = driver->next;
        
        if (driver->next)
                driver->next->prev = driver->prev;

#ifdef CONFIG_PROC_FS
        proc_tty_unregister_driver(driver);
#endif
        return 0;
}


/*
 * Initialize the console device. This is called *early*, so
 * we can't necessarily depend on lots of kernel help here.
 * Just do some early initializations, and do the complex setup
 * later.
 */
long __init console_init(long kmem_start, long kmem_end)
{
        /* Setup the default TTY line discipline. */
        memset(ldiscs, 0, sizeof(ldiscs));
        (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);

        /*
         * Set up the standard termios.  Individual tty drivers may 
         * deviate from this; this is used as a template.
         */
        memset(&tty_std_termios, 0, sizeof(struct termios));
        memcpy(tty_std_termios.c_cc, INIT_C_CC, NCCS);
        tty_std_termios.c_iflag = ICRNL | IXON;
        tty_std_termios.c_oflag = OPOST | ONLCR;
        tty_std_termios.c_cflag = B38400 | CS8 | CREAD | HUPCL;
        tty_std_termios.c_lflag = ISIG | ICANON | ECHO | ECHOE | ECHOK |
                ECHOCTL | ECHOKE | IEXTEN;

        /*
         * set up the console device so that later boot sequences can 
         * inform about problems etc..
         */
#ifdef CONFIG_VT
        kmem_start = con_init(kmem_start);
#endif
#ifdef CONFIG_SERIAL_CONSOLE
        kmem_start = serial_console_init(kmem_start, kmem_end);
#endif
        return kmem_start;
}

static struct tty_driver dev_tty_driver, dev_syscons_driver, dev_ptmx_driver;
#ifdef CONFIG_VT
static struct tty_driver dev_console_driver;
#endif

/*
 * Ok, now we can initialize the rest of the tty devices and can count
 * on memory allocations, interrupts etc..
 */
__initfunc(int tty_init(void))
{
        if (sizeof(struct tty_struct) > PAGE_SIZE)
                panic("size of tty structure > PAGE_SIZE!");

        /*
         * dev_tty_driver and dev_console_driver are actually magic
         * devices which get redirected at open time.  Nevertheless,
         * we register them so that register_chrdev is called
         * appropriately.
         */
        memset(&dev_tty_driver, 0, sizeof(struct tty_driver));
        dev_tty_driver.magic = TTY_DRIVER_MAGIC;
        dev_tty_driver.driver_name = "/dev/tty";
        dev_tty_driver.name = dev_tty_driver.driver_name + 5;
        dev_tty_driver.name_base = 0;
        dev_tty_driver.major = TTYAUX_MAJOR;
        dev_tty_driver.minor_start = 0;
        dev_tty_driver.num = 1;
        dev_tty_driver.type = TTY_DRIVER_TYPE_SYSTEM;
        dev_tty_driver.subtype = SYSTEM_TYPE_TTY;
        
        if (tty_register_driver(&dev_tty_driver))
                panic("Couldn't register /dev/tty driver\n");

        dev_syscons_driver = dev_tty_driver;
        dev_syscons_driver.driver_name = "/dev/console";
        dev_syscons_driver.name = dev_syscons_driver.driver_name + 5;
        dev_syscons_driver.major = TTYAUX_MAJOR;
        dev_syscons_driver.minor_start = 1;
        dev_syscons_driver.type = TTY_DRIVER_TYPE_SYSTEM;
        dev_syscons_driver.subtype = SYSTEM_TYPE_SYSCONS;

        if (tty_register_driver(&dev_syscons_driver))
                panic("Couldn't register /dev/console driver\n");

        dev_ptmx_driver = dev_tty_driver;
        dev_ptmx_driver.driver_name = "/dev/ptmx";
        dev_ptmx_driver.name = dev_ptmx_driver.driver_name + 5;
        dev_ptmx_driver.major= MAJOR(PTMX_DEV);
        dev_ptmx_driver.minor_start = MINOR(PTMX_DEV);
        dev_ptmx_driver.type = TTY_DRIVER_TYPE_SYSTEM;
        dev_ptmx_driver.subtype = SYSTEM_TYPE_SYSPTMX;

        if (tty_register_driver(&dev_ptmx_driver))
                panic("Couldn't register /dev/ptmx driver\n");

#ifdef CONFIG_VT
        dev_console_driver = dev_tty_driver;
        dev_console_driver.driver_name = "/dev/tty0";
        dev_console_driver.name = dev_console_driver.driver_name + 5;
        dev_console_driver.major = TTY_MAJOR;
        dev_console_driver.type = TTY_DRIVER_TYPE_SYSTEM;
        dev_console_driver.subtype = SYSTEM_TYPE_CONSOLE;

        if (tty_register_driver(&dev_console_driver))
                panic("Couldn't register /dev/tty0 driver\n");

        kbd_init();
#endif
#ifdef CONFIG_ESPSERIAL  /* init ESP before rs, so rs doesn't see the port */
        espserial_init();
#endif
#ifdef CONFIG_SERIAL
        rs_init();
#endif
#ifdef CONFIG_MAC_SERIAL
        macserial_init();
#endif
#ifdef CONFIG_ROCKETPORT
        rp_init();
#endif
#ifdef CONFIG_CYCLADES
        cy_init();
#endif
#ifdef CONFIG_STALLION
        stl_init();
#endif
#ifdef CONFIG_ISTALLION
        stli_init();
#endif
#ifdef CONFIG_DIGI
        pcxe_init();
#endif
#ifdef CONFIG_DIGIEPCA
        pc_init();
#endif
#ifdef CONFIG_RISCOM8
        riscom8_init();
#endif
#ifdef CONFIG_SPECIALIX
        specialix_init();
#endif
#ifdef CONFIG_8xx
        rs_8xx_init();
#endif /* CONFIG_8xx */
        pty_init();
#ifdef CONFIG_VT
        vcs_init();
#endif
        return 0;
}