tty_ioctl.c

Go to the documentation of this file.

/*
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 * 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).
 */

#include <linux/types.h>
#include <linux/termios.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/tty.h>
#include <linux/fcntl.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/mutex.h>
#include <linux/compat.h>

#include <asm/io.h>
#include <asm/uaccess.h>

#undef TTY_DEBUG_WAIT_UNTIL_SENT

#undef  DEBUG

/*
 * Internal flag options for termios setting behavior
 */
#define TERMIOS_FLUSH   1
#define TERMIOS_WAIT    2
#define TERMIOS_TERMIO  4
#define TERMIOS_OLD 8


int tty_chars_in_buffer(struct tty_struct *tty)
{
    if (tty->ops->chars_in_buffer)
        return tty->ops->chars_in_buffer(tty);
    else
        return 0;
}
EXPORT_SYMBOL(tty_chars_in_buffer);

int tty_write_room(struct tty_struct *tty)
{
    if (tty->ops->write_room)
        return tty->ops->write_room(tty);
    return 2048;
}
EXPORT_SYMBOL(tty_write_room);

void tty_driver_flush_buffer(struct tty_struct *tty)
{
    if (tty->ops->flush_buffer)
        tty->ops->flush_buffer(tty);
}
EXPORT_SYMBOL(tty_driver_flush_buffer);

void tty_throttle(struct tty_struct *tty)
{
    mutex_lock(&tty->termios_mutex);
    /* check TTY_THROTTLED first so it indicates our state */
    if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
        tty->ops->throttle)
        tty->ops->throttle(tty);
    mutex_unlock(&tty->termios_mutex);
}
EXPORT_SYMBOL(tty_throttle);

void tty_unthrottle(struct tty_struct *tty)
{
    mutex_lock(&tty->termios_mutex);
    if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
        tty->ops->unthrottle)
        tty->ops->unthrottle(tty);
    mutex_unlock(&tty->termios_mutex);
}
EXPORT_SYMBOL(tty_unthrottle);

void tty_wait_until_sent(struct tty_struct *tty, long timeout)
{
#ifdef TTY_DEBUG_WAIT_UNTIL_SENT
    char buf[64];

    printk(KERN_DEBUG "%s wait until sent...\n", tty_name(tty, buf));
#endif
    if (!timeout)
        timeout = MAX_SCHEDULE_TIMEOUT;
    if (wait_event_interruptible_timeout(tty->write_wait,
            !tty_chars_in_buffer(tty), timeout) >= 0) {
        if (tty->ops->wait_until_sent)
            tty->ops->wait_until_sent(tty, timeout);
    }
}
EXPORT_SYMBOL(tty_wait_until_sent);


/*
 *      Termios Helper Methods
 */

static void unset_locked_termios(struct ktermios *termios,
                 struct ktermios *old,
                 struct ktermios *locked)
{
    int i;

#define NOSET_MASK(x, y, z) (x = ((x) & ~(z)) | ((y) & (z)))

    if (!locked) {
        printk(KERN_WARNING "Warning?!? termios_locked is NULL.\n");
        return;
    }

    NOSET_MASK(termios->c_iflag, old->c_iflag, locked->c_iflag);
    NOSET_MASK(termios->c_oflag, old->c_oflag, locked->c_oflag);
    NOSET_MASK(termios->c_cflag, old->c_cflag, locked->c_cflag);
    NOSET_MASK(termios->c_lflag, old->c_lflag, locked->c_lflag);
    termios->c_line = locked->c_line ? old->c_line : termios->c_line;
    for (i = 0; i < NCCS; i++)
        termios->c_cc[i] = locked->c_cc[i] ?
            old->c_cc[i] : termios->c_cc[i];
    /* FIXME: What should we do for i/ospeed */
}

/*
 * Routine which returns the baud rate of the tty
 *
 * Note that the baud_table needs to be kept in sync with the
 * include/asm/termbits.h file.
 */
static const speed_t baud_table[] = {
    0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
    9600, 19200, 38400, 57600, 115200, 230400, 460800,
#ifdef __sparc__
    76800, 153600, 307200, 614400, 921600
#else
    500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
    2500000, 3000000, 3500000, 4000000
#endif
};

#ifndef __sparc__
static const tcflag_t baud_bits[] = {
    B0, B50, B75, B110, B134, B150, B200, B300, B600,
    B1200, B1800, B2400, B4800, B9600, B19200, B38400,
    B57600, B115200, B230400, B460800, B500000, B576000,
    B921600, B1000000, B1152000, B1500000, B2000000, B2500000,
    B3000000, B3500000, B4000000
};
#else
static const tcflag_t baud_bits[] = {
    B0, B50, B75, B110, B134, B150, B200, B300, B600,
    B1200, B1800, B2400, B4800, B9600, B19200, B38400,
    B57600, B115200, B230400, B460800, B76800, B153600,
    B307200, B614400, B921600
};
#endif

static int n_baud_table = ARRAY_SIZE(baud_table);

speed_t tty_termios_baud_rate(struct ktermios *termios)
{
    unsigned int cbaud;

    cbaud = termios->c_cflag & CBAUD;

#ifdef BOTHER
    /* Magic token for arbitrary speed via c_ispeed/c_ospeed */
    if (cbaud == BOTHER)
        return termios->c_ospeed;
#endif
    if (cbaud & CBAUDEX) {
        cbaud &= ~CBAUDEX;

        if (cbaud < 1 || cbaud + 15 > n_baud_table)
            termios->c_cflag &= ~CBAUDEX;
        else
            cbaud += 15;
    }
    return baud_table[cbaud];
}
EXPORT_SYMBOL(tty_termios_baud_rate);

speed_t tty_termios_input_baud_rate(struct ktermios *termios)
{
#ifdef IBSHIFT
    unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;

    if (cbaud == B0)
        return tty_termios_baud_rate(termios);

    /* Magic token for arbitrary speed via c_ispeed*/
    if (cbaud == BOTHER)
        return termios->c_ispeed;

    if (cbaud & CBAUDEX) {
        cbaud &= ~CBAUDEX;

        if (cbaud < 1 || cbaud + 15 > n_baud_table)
            termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
        else
            cbaud += 15;
    }
    return baud_table[cbaud];
#else
    return tty_termios_baud_rate(termios);
#endif
}
EXPORT_SYMBOL(tty_termios_input_baud_rate);

void tty_termios_encode_baud_rate(struct ktermios *termios,
                  speed_t ibaud, speed_t obaud)
{
    int i = 0;
    int ifound = -1, ofound = -1;
    int iclose = ibaud/50, oclose = obaud/50;
    int ibinput = 0;

    if (obaud == 0)         /* CD dropped         */
        ibaud = 0;      /* Clear ibaud to be sure */

    termios->c_ispeed = ibaud;
    termios->c_ospeed = obaud;

#ifdef BOTHER
    /* If the user asked for a precise weird speed give a precise weird
       answer. If they asked for a Bfoo speed they many have problems
       digesting non-exact replies so fuzz a bit */

    if ((termios->c_cflag & CBAUD) == BOTHER)
        oclose = 0;
    if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
        iclose = 0;
    if ((termios->c_cflag >> IBSHIFT) & CBAUD)
        ibinput = 1;    /* An input speed was specified */
#endif
    termios->c_cflag &= ~CBAUD;

    /*
     *  Our goal is to find a close match to the standard baud rate
     *  returned. Walk the baud rate table and if we get a very close
     *  match then report back the speed as a POSIX Bxxxx value by
     *  preference
     */

    do {
        if (obaud - oclose <= baud_table[i] &&
            obaud + oclose >= baud_table[i]) {
            termios->c_cflag |= baud_bits[i];
            ofound = i;
        }
        if (ibaud - iclose <= baud_table[i] &&
            ibaud + iclose >= baud_table[i]) {
            /* For the case input == output don't set IBAUD bits
               if the user didn't do so */
            if (ofound == i && !ibinput)
                ifound  = i;
#ifdef IBSHIFT
            else {
                ifound = i;
                termios->c_cflag |= (baud_bits[i] << IBSHIFT);
            }
#endif
        }
    } while (++i < n_baud_table);

    /*
     *  If we found no match then use BOTHER if provided or warn
     *  the user their platform maintainer needs to wake up if not.
     */
#ifdef BOTHER
    if (ofound == -1)
        termios->c_cflag |= BOTHER;
    /* Set exact input bits only if the input and output differ or the
       user already did */
    if (ifound == -1 && (ibaud != obaud || ibinput))
        termios->c_cflag |= (BOTHER << IBSHIFT);
#else
    if (ifound == -1 || ofound == -1) {
        printk_once(KERN_WARNING "tty: Unable to return correct "
              "speed data as your architecture needs updating.\n");
    }
#endif
}
EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);

void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
{
    tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
}
EXPORT_SYMBOL_GPL(tty_encode_baud_rate);

speed_t tty_get_baud_rate(struct tty_struct *tty)
{
    speed_t baud = tty_termios_baud_rate(&tty->termios);

    if (baud == 38400 && tty->alt_speed) {
        if (!tty->warned) {
            printk(KERN_WARNING "Use of setserial/setrocket to "
                        "set SPD_* flags is deprecated\n");
            tty->warned = 1;
        }
        baud = tty->alt_speed;
    }

    return baud;
}
EXPORT_SYMBOL(tty_get_baud_rate);

void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old)
{
    /* The bits a dumb device handles in software. Smart devices need
       to always provide a set_termios method */
    new->c_cflag &= HUPCL | CREAD | CLOCAL;
    new->c_cflag |= old->c_cflag & ~(HUPCL | CREAD | CLOCAL);
    new->c_ispeed = old->c_ispeed;
    new->c_ospeed = old->c_ospeed;
}
EXPORT_SYMBOL(tty_termios_copy_hw);

int tty_termios_hw_change(struct ktermios *a, struct ktermios *b)
{
    if (a->c_ispeed != b->c_ispeed || a->c_ospeed != b->c_ospeed)
        return 1;
    if ((a->c_cflag ^ b->c_cflag) & ~(HUPCL | CREAD | CLOCAL))
        return 1;
    return 0;
}
EXPORT_SYMBOL(tty_termios_hw_change);

int tty_set_termios(struct tty_struct *tty, struct ktermios *new_termios)
{
    struct ktermios old_termios;
    struct tty_ldisc *ld;
    unsigned long flags;

    /*
     *  Perform the actual termios internal changes under lock.
     */


    /* FIXME: we need to decide on some locking/ordering semantics
       for the set_termios notification eventually */
    mutex_lock(&tty->termios_mutex);
    old_termios = tty->termios;
    tty->termios = *new_termios;
    unset_locked_termios(&tty->termios, &old_termios, &tty->termios_locked);

    /* See if packet mode change of state. */
    if (tty->link && tty->link->packet) {
        int extproc = (old_termios.c_lflag & EXTPROC) |
                (tty->termios.c_lflag & EXTPROC);
        int old_flow = ((old_termios.c_iflag & IXON) &&
                (old_termios.c_cc[VSTOP] == '\023') &&
                (old_termios.c_cc[VSTART] == '\021'));
        int new_flow = (I_IXON(tty) &&
                STOP_CHAR(tty) == '\023' &&
                START_CHAR(tty) == '\021');
        if ((old_flow != new_flow) || extproc) {
            spin_lock_irqsave(&tty->ctrl_lock, flags);
            if (old_flow != new_flow) {
                tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
                if (new_flow)
                    tty->ctrl_status |= TIOCPKT_DOSTOP;
                else
                    tty->ctrl_status |= TIOCPKT_NOSTOP;
            }
            if (extproc)
                tty->ctrl_status |= TIOCPKT_IOCTL;
            spin_unlock_irqrestore(&tty->ctrl_lock, flags);
            wake_up_interruptible(&tty->link->read_wait);
        }
    }

    if (tty->ops->set_termios)
        (*tty->ops->set_termios)(tty, &old_termios);
    else
        tty_termios_copy_hw(&tty->termios, &old_termios);

    ld = tty_ldisc_ref(tty);
    if (ld != NULL) {
        if (ld->ops->set_termios)
            (ld->ops->set_termios)(tty, &old_termios);
        tty_ldisc_deref(ld);
    }
    mutex_unlock(&tty->termios_mutex);
    return 0;
}
EXPORT_SYMBOL_GPL(tty_set_termios);

static int set_termios(struct tty_struct *tty, void __user *arg, int opt)
{
    struct ktermios tmp_termios;
    struct tty_ldisc *ld;
    int retval = tty_check_change(tty);

    if (retval)
        return retval;

    mutex_lock(&tty->termios_mutex);
    tmp_termios = tty->termios;
    mutex_unlock(&tty->termios_mutex);

    if (opt & TERMIOS_TERMIO) {
        if (user_termio_to_kernel_termios(&tmp_termios,
                        (struct termio __user *)arg))
            return -EFAULT;
#ifdef TCGETS2
    } else if (opt & TERMIOS_OLD) {
        if (user_termios_to_kernel_termios_1(&tmp_termios,
                        (struct termios __user *)arg))
            return -EFAULT;
    } else {
        if (user_termios_to_kernel_termios(&tmp_termios,
                        (struct termios2 __user *)arg))
            return -EFAULT;
    }
#else
    } else if (user_termios_to_kernel_termios(&tmp_termios,
                    (struct termios __user *)arg))
        return -EFAULT;
#endif

    /* If old style Bfoo values are used then load c_ispeed/c_ospeed
     * with the real speed so its unconditionally usable */
    tmp_termios.c_ispeed = tty_termios_input_baud_rate(&tmp_termios);
    tmp_termios.c_ospeed = tty_termios_baud_rate(&tmp_termios);

    ld = tty_ldisc_ref(tty);

    if (ld != NULL) {
        if ((opt & TERMIOS_FLUSH) && ld->ops->flush_buffer)
            ld->ops->flush_buffer(tty);
        tty_ldisc_deref(ld);
    }

    if (opt & TERMIOS_WAIT) {
        tty_wait_until_sent(tty, 0);
        if (signal_pending(current))
            return -EINTR;
    }

    tty_set_termios(tty, &tmp_termios);

    /* FIXME: Arguably if tmp_termios == tty->termios AND the
       actual requested termios was not tmp_termios then we may
       want to return an error as no user requested change has
       succeeded */
    return 0;
}

static void copy_termios(struct tty_struct *tty, struct ktermios *kterm)
{
    mutex_lock(&tty->termios_mutex);
    *kterm = tty->termios;
    mutex_unlock(&tty->termios_mutex);
}

static void copy_termios_locked(struct tty_struct *tty, struct ktermios *kterm)
{
    mutex_lock(&tty->termios_mutex);
    *kterm = tty->termios_locked;
    mutex_unlock(&tty->termios_mutex);
}

static int get_termio(struct tty_struct *tty, struct termio __user *termio)
{
    struct ktermios kterm;
    copy_termios(tty, &kterm);
    if (kernel_termios_to_user_termio(termio, &kterm))
        return -EFAULT;
    return 0;
}


#ifdef TCGETX

static int set_termiox(struct tty_struct *tty, void __user *arg, int opt)
{
    struct termiox tnew;
    struct tty_ldisc *ld;

    if (tty->termiox == NULL)
        return -EINVAL;
    if (copy_from_user(&tnew, arg, sizeof(struct termiox)))
        return -EFAULT;

    ld = tty_ldisc_ref(tty);
    if (ld != NULL) {
        if ((opt & TERMIOS_FLUSH) && ld->ops->flush_buffer)
            ld->ops->flush_buffer(tty);
        tty_ldisc_deref(ld);
    }
    if (opt & TERMIOS_WAIT) {
        tty_wait_until_sent(tty, 0);
        if (signal_pending(current))
            return -EINTR;
    }

    mutex_lock(&tty->termios_mutex);
    if (tty->ops->set_termiox)
        tty->ops->set_termiox(tty, &tnew);
    mutex_unlock(&tty->termios_mutex);
    return 0;
}

#endif


#ifdef TIOCGETP
/*
 * These are deprecated, but there is limited support..
 *
 * The "sg_flags" translation is a joke..
 */
static int get_sgflags(struct tty_struct *tty)
{
    int flags = 0;

    if (!(tty->termios.c_lflag & ICANON)) {
        if (tty->termios.c_lflag & ISIG)
            flags |= 0x02;      /* cbreak */
        else
            flags |= 0x20;      /* raw */
    }
    if (tty->termios.c_lflag & ECHO)
        flags |= 0x08;          /* echo */
    if (tty->termios.c_oflag & OPOST)
        if (tty->termios.c_oflag & ONLCR)
            flags |= 0x10;      /* crmod */
    return flags;
}

static int get_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
{
    struct sgttyb tmp;

    mutex_lock(&tty->termios_mutex);
    tmp.sg_ispeed = tty->termios.c_ispeed;
    tmp.sg_ospeed = tty->termios.c_ospeed;
    tmp.sg_erase = tty->termios.c_cc[VERASE];
    tmp.sg_kill = tty->termios.c_cc[VKILL];
    tmp.sg_flags = get_sgflags(tty);
    mutex_unlock(&tty->termios_mutex);

    return copy_to_user(sgttyb, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}

static void set_sgflags(struct ktermios *termios, int flags)
{
    termios->c_iflag = ICRNL | IXON;
    termios->c_oflag = 0;
    termios->c_lflag = ISIG | ICANON;
    if (flags & 0x02) { /* cbreak */
        termios->c_iflag = 0;
        termios->c_lflag &= ~ICANON;
    }
    if (flags & 0x08) {     /* echo */
        termios->c_lflag |= ECHO | ECHOE | ECHOK |
                    ECHOCTL | ECHOKE | IEXTEN;
    }
    if (flags & 0x10) {     /* crmod */
        termios->c_oflag |= OPOST | ONLCR;
    }
    if (flags & 0x20) { /* raw */
        termios->c_iflag = 0;
        termios->c_lflag &= ~(ISIG | ICANON);
    }
    if (!(termios->c_lflag & ICANON)) {
        termios->c_cc[VMIN] = 1;
        termios->c_cc[VTIME] = 0;
    }
}

static int set_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
{
    int retval;
    struct sgttyb tmp;
    struct ktermios termios;

    retval = tty_check_change(tty);
    if (retval)
        return retval;

    if (copy_from_user(&tmp, sgttyb, sizeof(tmp)))
        return -EFAULT;

    mutex_lock(&tty->termios_mutex);
    termios = tty->termios;
    termios.c_cc[VERASE] = tmp.sg_erase;
    termios.c_cc[VKILL] = tmp.sg_kill;
    set_sgflags(&termios, tmp.sg_flags);
    /* Try and encode into Bfoo format */
#ifdef BOTHER
    tty_termios_encode_baud_rate(&termios, termios.c_ispeed,
                        termios.c_ospeed);
#endif
    mutex_unlock(&tty->termios_mutex);
    tty_set_termios(tty, &termios);
    return 0;
}
#endif

#ifdef TIOCGETC
static int get_tchars(struct tty_struct *tty, struct tchars __user *tchars)
{
    struct tchars tmp;

    mutex_lock(&tty->termios_mutex);
    tmp.t_intrc = tty->termios.c_cc[VINTR];
    tmp.t_quitc = tty->termios.c_cc[VQUIT];
    tmp.t_startc = tty->termios.c_cc[VSTART];
    tmp.t_stopc = tty->termios.c_cc[VSTOP];
    tmp.t_eofc = tty->termios.c_cc[VEOF];
    tmp.t_brkc = tty->termios.c_cc[VEOL2];  /* what is brkc anyway? */
    mutex_unlock(&tty->termios_mutex);
    return copy_to_user(tchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}

static int set_tchars(struct tty_struct *tty, struct tchars __user *tchars)
{
    struct tchars tmp;

    if (copy_from_user(&tmp, tchars, sizeof(tmp)))
        return -EFAULT;
    mutex_lock(&tty->termios_mutex);
    tty->termios.c_cc[VINTR] = tmp.t_intrc;
    tty->termios.c_cc[VQUIT] = tmp.t_quitc;
    tty->termios.c_cc[VSTART] = tmp.t_startc;
    tty->termios.c_cc[VSTOP] = tmp.t_stopc;
    tty->termios.c_cc[VEOF] = tmp.t_eofc;
    tty->termios.c_cc[VEOL2] = tmp.t_brkc;  /* what is brkc anyway? */
    mutex_unlock(&tty->termios_mutex);
    return 0;
}
#endif

#ifdef TIOCGLTC
static int get_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
{
    struct ltchars tmp;

    mutex_lock(&tty->termios_mutex);
    tmp.t_suspc = tty->termios.c_cc[VSUSP];
    /* what is dsuspc anyway? */
    tmp.t_dsuspc = tty->termios.c_cc[VSUSP];
    tmp.t_rprntc = tty->termios.c_cc[VREPRINT];
    /* what is flushc anyway? */
    tmp.t_flushc = tty->termios.c_cc[VEOL2];
    tmp.t_werasc = tty->termios.c_cc[VWERASE];
    tmp.t_lnextc = tty->termios.c_cc[VLNEXT];
    mutex_unlock(&tty->termios_mutex);
    return copy_to_user(ltchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}

static int set_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
{
    struct ltchars tmp;

    if (copy_from_user(&tmp, ltchars, sizeof(tmp)))
        return -EFAULT;

    mutex_lock(&tty->termios_mutex);
    tty->termios.c_cc[VSUSP] = tmp.t_suspc;
    /* what is dsuspc anyway? */
    tty->termios.c_cc[VEOL2] = tmp.t_dsuspc;
    tty->termios.c_cc[VREPRINT] = tmp.t_rprntc;
    /* what is flushc anyway? */
    tty->termios.c_cc[VEOL2] = tmp.t_flushc;
    tty->termios.c_cc[VWERASE] = tmp.t_werasc;
    tty->termios.c_cc[VLNEXT] = tmp.t_lnextc;
    mutex_unlock(&tty->termios_mutex);
    return 0;
}
#endif

static int send_prio_char(struct tty_struct *tty, char ch)
{
    int was_stopped = tty->stopped;

    if (tty->ops->send_xchar) {
        tty->ops->send_xchar(tty, ch);
        return 0;
    }

    if (tty_write_lock(tty, 0) < 0)
        return -ERESTARTSYS;

    if (was_stopped)
        start_tty(tty);
    tty->ops->write(tty, &ch, 1);
    if (was_stopped)
        stop_tty(tty);
    tty_write_unlock(tty);
    return 0;
}

static int tty_change_softcar(struct tty_struct *tty, int arg)
{
    int ret = 0;
    int bit = arg ? CLOCAL : 0;
    struct ktermios old;

    mutex_lock(&tty->termios_mutex);
    old = tty->termios;
    tty->termios.c_cflag &= ~CLOCAL;
    tty->termios.c_cflag |= bit;
    if (tty->ops->set_termios)
        tty->ops->set_termios(tty, &old);
    if ((tty->termios.c_cflag & CLOCAL) != bit)
        ret = -EINVAL;
    mutex_unlock(&tty->termios_mutex);
    return ret;
}

int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
            unsigned int cmd, unsigned long arg)
{
    struct tty_struct *real_tty;
    void __user *p = (void __user *)arg;
    int ret = 0;
    struct ktermios kterm;

    BUG_ON(file == NULL);

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

    switch (cmd) {
#ifdef TIOCGETP
    case TIOCGETP:
        return get_sgttyb(real_tty, (struct sgttyb __user *) arg);
    case TIOCSETP:
    case TIOCSETN:
        return set_sgttyb(real_tty, (struct sgttyb __user *) arg);
#endif
#ifdef TIOCGETC
    case TIOCGETC:
        return get_tchars(real_tty, p);
    case TIOCSETC:
        return set_tchars(real_tty, p);
#endif
#ifdef TIOCGLTC
    case TIOCGLTC:
        return get_ltchars(real_tty, p);
    case TIOCSLTC:
        return set_ltchars(real_tty, p);
#endif
    case TCSETSF:
        return set_termios(real_tty, p,  TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_OLD);
    case TCSETSW:
        return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_OLD);
    case TCSETS:
        return set_termios(real_tty, p, TERMIOS_OLD);
#ifndef TCGETS2
    case TCGETS:
        copy_termios(real_tty, &kterm);
        if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
            ret = -EFAULT;
        return ret;
#else
    case TCGETS:
        copy_termios(real_tty, &kterm);
        if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
            ret = -EFAULT;
        return ret;
    case TCGETS2:
        copy_termios(real_tty, &kterm);
        if (kernel_termios_to_user_termios((struct termios2 __user *)arg, &kterm))
            ret = -EFAULT;
        return ret;
    case TCSETSF2:
        return set_termios(real_tty, p,  TERMIOS_FLUSH | TERMIOS_WAIT);
    case TCSETSW2:
        return set_termios(real_tty, p, TERMIOS_WAIT);
    case TCSETS2:
        return set_termios(real_tty, p, 0);
#endif
    case TCGETA:
        return get_termio(real_tty, p);
    case TCSETAF:
        return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_TERMIO);
    case TCSETAW:
        return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_TERMIO);
    case TCSETA:
        return set_termios(real_tty, p, TERMIOS_TERMIO);
#ifndef TCGETS2
    case TIOCGLCKTRMIOS:
        copy_termios_locked(real_tty, &kterm);
        if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
            ret = -EFAULT;
        return ret;
    case TIOCSLCKTRMIOS:
        if (!capable(CAP_SYS_ADMIN))
            return -EPERM;
        copy_termios_locked(real_tty, &kterm);
        if (user_termios_to_kernel_termios(&kterm,
                           (struct termios __user *) arg))
            return -EFAULT;
        mutex_lock(&real_tty->termios_mutex);
        real_tty->termios_locked = kterm;
        mutex_unlock(&real_tty->termios_mutex);
        return 0;
#else
    case TIOCGLCKTRMIOS:
        copy_termios_locked(real_tty, &kterm);
        if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
            ret = -EFAULT;
        return ret;
    case TIOCSLCKTRMIOS:
        if (!capable(CAP_SYS_ADMIN))
            return -EPERM;
        copy_termios_locked(real_tty, &kterm);
        if (user_termios_to_kernel_termios_1(&kterm,
                           (struct termios __user *) arg))
            return -EFAULT;
        mutex_lock(&real_tty->termios_mutex);
        real_tty->termios_locked = kterm;
        mutex_unlock(&real_tty->termios_mutex);
        return ret;
#endif
#ifdef TCGETX
    case TCGETX: {
        struct termiox ktermx;
        if (real_tty->termiox == NULL)
            return -EINVAL;
        mutex_lock(&real_tty->termios_mutex);
        memcpy(&ktermx, real_tty->termiox, sizeof(struct termiox));
        mutex_unlock(&real_tty->termios_mutex);
        if (copy_to_user(p, &ktermx, sizeof(struct termiox)))
            ret = -EFAULT;
        return ret;
    }
    case TCSETX:
        return set_termiox(real_tty, p, 0);
    case TCSETXW:
        return set_termiox(real_tty, p, TERMIOS_WAIT);
    case TCSETXF:
        return set_termiox(real_tty, p, TERMIOS_FLUSH);
#endif      
    case TIOCGSOFTCAR:
        copy_termios(real_tty, &kterm);
        ret = put_user((kterm.c_cflag & CLOCAL) ? 1 : 0,
                        (int __user *)arg);
        return ret;
    case TIOCSSOFTCAR:
        if (get_user(arg, (unsigned int __user *) arg))
            return -EFAULT;
        return tty_change_softcar(real_tty, arg);
    default:
        return -ENOIOCTLCMD;
    }
}
EXPORT_SYMBOL_GPL(tty_mode_ioctl);

int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
{
    struct tty_ldisc *ld;
    int retval = tty_check_change(tty);
    if (retval)
        return retval;

    ld = tty_ldisc_ref_wait(tty);
    switch (arg) {
    case TCIFLUSH:
        if (ld && ld->ops->flush_buffer)
            ld->ops->flush_buffer(tty);
        break;
    case TCIOFLUSH:
        if (ld && ld->ops->flush_buffer)
            ld->ops->flush_buffer(tty);
        /* fall through */
    case TCOFLUSH:
        tty_driver_flush_buffer(tty);
        break;
    default:
        tty_ldisc_deref(ld);
        return -EINVAL;
    }
    tty_ldisc_deref(ld);
    return 0;
}
EXPORT_SYMBOL_GPL(tty_perform_flush);

int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
               unsigned int cmd, unsigned long arg)
{
    unsigned long flags;
    int retval;

    switch (cmd) {
    case TCXONC:
        retval = tty_check_change(tty);
        if (retval)
            return retval;
        switch (arg) {
        case TCOOFF:
            if (!tty->flow_stopped) {
                tty->flow_stopped = 1;
                stop_tty(tty);
            }
            break;
        case TCOON:
            if (tty->flow_stopped) {
                tty->flow_stopped = 0;
                start_tty(tty);
            }
            break;
        case TCIOFF:
            if (STOP_CHAR(tty) != __DISABLED_CHAR)
                return send_prio_char(tty, STOP_CHAR(tty));
            break;
        case TCION:
            if (START_CHAR(tty) != __DISABLED_CHAR)
                return send_prio_char(tty, START_CHAR(tty));
            break;
        default:
            return -EINVAL;
        }
        return 0;
    case TCFLSH:
        return tty_perform_flush(tty, arg);
    case TIOCPKT:
    {
        int pktmode;

        if (tty->driver->type != TTY_DRIVER_TYPE_PTY ||
            tty->driver->subtype != PTY_TYPE_MASTER)
            return -ENOTTY;
        if (get_user(pktmode, (int __user *) arg))
            return -EFAULT;
        spin_lock_irqsave(&tty->ctrl_lock, flags);
        if (pktmode) {
            if (!tty->packet) {
                tty->packet = 1;
                tty->link->ctrl_status = 0;
            }
        } else
            tty->packet = 0;
        spin_unlock_irqrestore(&tty->ctrl_lock, flags);
        return 0;
    }
    default:
        /* Try the mode commands */
        return tty_mode_ioctl(tty, file, cmd, arg);
    }
}
EXPORT_SYMBOL(n_tty_ioctl_helper);

#ifdef CONFIG_COMPAT
long n_tty_compat_ioctl_helper(struct tty_struct *tty, struct file *file,
                    unsigned int cmd, unsigned long arg)
{
    switch (cmd) {
    case TIOCGLCKTRMIOS:
    case TIOCSLCKTRMIOS:
        return tty_mode_ioctl(tty, file, cmd, (unsigned long) compat_ptr(arg));
    default:
        return -ENOIOCTLCMD;
    }
}
EXPORT_SYMBOL(n_tty_compat_ioctl_helper);
#endif