iwlwifi: introduce host commands callbacks

[linux/fpc-iii.git] / drivers / char / tty_ioctl.c

/*
 *  linux/drivers/char/tty_ioctl.c
 *
 *  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 <asm/io.h>
#include <asm/uaccess.h>
#include <asm/system.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


/**
 *      tty_wait_until_sent     -       wait for I/O to finish
 *      @tty: tty we are waiting for
 *      @timeout: how long we will wait
 *
 *      Wait for characters pending in a tty driver to hit the wire, or
 *      for a timeout to occur (eg due to flow control)
 *
 *      Locking: none
 */

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 (!tty->driver->chars_in_buffer)
                return;
        if (!timeout)
                timeout = MAX_SCHEDULE_TIMEOUT;
        if (wait_event_interruptible_timeout(tty->write_wait,
                        !tty->driver->chars_in_buffer(tty), timeout) < 0)
                return;
        if (tty->driver->wait_until_sent)
                tty->driver->wait_until_sent(tty, timeout);
}
EXPORT_SYMBOL(tty_wait_until_sent);

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);

/**
 *      tty_termios_baud_rate
 *      @termios: termios structure
 *
 *      Convert termios baud rate data into a speed. This should be called
 *      with the termios lock held if this termios is a terminal termios
 *      structure. May change the termios data. Device drivers can call this
 *      function but should use ->c_[io]speed directly as they are updated.
 *
 *      Locking: none
 */

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

        cbaud = termios->c_cflag & CBAUD;

#ifdef BOTHER
        /* Magic token for arbitary 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);

/**
 *      tty_termios_input_baud_rate
 *      @termios: termios structure
 *
 *      Convert termios baud rate data into a speed. This should be called
 *      with the termios lock held if this termios is a terminal termios
 *      structure. May change the termios data. Device drivers can call this
 *      function but should use ->c_[io]speed directly as they are updated.
 *
 *      Locking: none
 */

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 arbitary 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);

/**
 *      tty_termios_encode_baud_rate
 *      @termios: ktermios structure holding user requested state
 *      @ispeed: input speed
 *      @ospeed: output speed
 *
 *      Encode the speeds set into the passed termios structure. This is
 *      used as a library helper for drivers os that they can report back
 *      the actual speed selected when it differs from the speed requested
 *
 *      For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
 *      we need to carefully set the bits when the user does not get the
 *      desired speed. We allow small margins and preserve as much of possible
 *      of the input intent to keep compatiblity.
 *
 *      Locking: Caller should hold termios lock. This is already held
 *      when calling this function from the driver termios handler.
 *
 *      The ifdefs deal with platforms whose owners have yet to update them
 *      and will all go away once this is done.
 */

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) {
                static int warned;
                if (!warned++)
                        printk(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);

/**
 *      tty_get_baud_rate       -       get tty bit rates
 *      @tty: tty to query
 *
 *      Returns the baud rate as an integer for this terminal. The
 *      termios lock must be held by the caller and the terminal bit
 *      flags may be updated.
 *
 *      Locking: none
 */

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);

/**
 *      tty_termios_copy_hw     -       copy hardware settings
 *      @new: New termios
 *      @old: Old termios
 *
 *      Propogate the hardware specific terminal setting bits from
 *      the old termios structure to the new one. This is used in cases
 *      where the hardware does not support reconfiguration or as a helper
 *      in some cases where only minimal reconfiguration is supported
 */

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);

/**
 *      tty_termios_hw_change   -       check for setting change
 *      @a: termios
 *      @b: termios to compare
 *
 *      Check if any of the bits that affect a dumb device have changed
 *      between the two termios structures, or a speed change is needed.
 */

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);

/**
 *      change_termios          -       update termios values
 *      @tty: tty to update
 *      @new_termios: desired new value
 *
 *      Perform updates to the termios values set on this terminal. There
 *      is a bit of layering violation here with n_tty in terms of the
 *      internal knowledge of this function.
 *
 *      Locking: termios_sem
 */

static void change_termios(struct tty_struct *tty, struct ktermios *new_termios)
{
        int canon_change;
        struct ktermios old_termios = *tty->termios;
        struct tty_ldisc *ld;

        /*
         *      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);

        *tty->termios = *new_termios;
        unset_locked_termios(tty->termios, &old_termios, tty->termios_locked);
        canon_change = (old_termios.c_lflag ^ tty->termios->c_lflag) & ICANON;
        if (canon_change) {
                memset(&tty->read_flags, 0, sizeof tty->read_flags);
                tty->canon_head = tty->read_tail;
                tty->canon_data = 0;
                tty->erasing = 0;
        }

        /* This bit should be in the ldisc code */
        if (canon_change && !L_ICANON(tty) && tty->read_cnt)
                /* Get characters left over from canonical mode. */
                wake_up_interruptible(&tty->read_wait);

        /* See if packet mode change of state. */
        if (tty->link && tty->link->packet) {
                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) {
                        tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
                        if (new_flow)
                                tty->ctrl_status |= TIOCPKT_DOSTOP;
                        else
                                tty->ctrl_status |= TIOCPKT_NOSTOP;
                        wake_up_interruptible(&tty->link->read_wait);
                }
        }

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

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

/**
 *      set_termios             -       set termios values for a tty
 *      @tty: terminal device
 *      @arg: user data
 *      @opt: option information
 *
 *      Helper function to prepare termios data and run necessary other
 *      functions before using change_termios to do the actual changes.
 *
 *      Locking:
 *              Called functions take ldisc and termios_sem locks
 */

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;

        memcpy(&tmp_termios, tty->termios, sizeof(struct ktermios));

        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->flush_buffer)
                        ld->flush_buffer(tty);
                tty_ldisc_deref(ld);
        }

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

        change_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 int get_termio(struct tty_struct *tty, struct termio __user *termio)
{
        if (kernel_termios_to_user_termio(termio, tty->termios))
                return -EFAULT;
        return 0;
}

static unsigned long inq_canon(struct tty_struct *tty)
{
        int nr, head, tail;

        if (!tty->canon_data || !tty->read_buf)
                return 0;
        head = tty->canon_head;
        tail = tty->read_tail;
        nr = (head - tail) & (N_TTY_BUF_SIZE-1);
        /* Skip EOF-chars.. */
        while (head != tail) {
                if (test_bit(tail, tty->read_flags) &&
                    tty->read_buf[tail] == __DISABLED_CHAR)
                        nr--;
                tail = (tail+1) & (N_TTY_BUF_SIZE-1);
        }
        return nr;
}

#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;
        }
}

/**
 *      set_sgttyb              -       set legacy terminal values
 *      @tty: tty structure
 *      @sgttyb: pointer to old style terminal structure
 *
 *      Updates a terminal from the legacy BSD style terminal information
 *      structure.
 *
 *      Locking: termios_sem
 */

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);
        change_termios(tty, &termios);
        return 0;
}
#endif

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

        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? */
        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;
        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? */
        return 0;
}
#endif

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

        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];
        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;

        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;
        return 0;
}
#endif

/**
 *      send_prio_char          -       send priority character
 *
 *      Send a high priority character to the tty even if stopped
 *
 *      Locking: none for xchar method, write ordering for write method.
 */

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

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

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

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

/**
 *      tty_mode_ioctl          -       mode related ioctls
 *      @tty: tty for the ioctl
 *      @file: file pointer for the tty
 *      @cmd: command
 *      @arg: ioctl argument
 *
 *      Perform non line discipline specific mode control ioctls. This
 *      is designed to be called by line disciplines to ensure they provide
 *      consistent mode setting.
 */

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;

        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:
                if (kernel_termios_to_user_termios((struct termios __user *)arg, real_tty->termios))
                        return -EFAULT;
                return 0;
#else
        case TCGETS:
                if (kernel_termios_to_user_termios_1((struct termios __user *)arg, real_tty->termios))
                        return -EFAULT;
                return 0;
        case TCGETS2:
                if (kernel_termios_to_user_termios((struct termios2 __user *)arg, real_tty->termios))
                        return -EFAULT;
                return 0;
        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:
                if (kernel_termios_to_user_termios((struct termios __user *)arg, real_tty->termios_locked))
                        return -EFAULT;
                return 0;
        case TIOCSLCKTRMIOS:
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;
                if (user_termios_to_kernel_termios(real_tty->termios_locked,
                                               (struct termios __user *) arg))
                        return -EFAULT;
                return 0;
#else
        case TIOCGLCKTRMIOS:
                if (kernel_termios_to_user_termios_1((struct termios __user *)arg, real_tty->termios_locked))
                        return -EFAULT;
                return 0;
        case TIOCSLCKTRMIOS:
                if (!capable(CAP_SYS_ADMIN))
                        return -EPERM;
                if (user_termios_to_kernel_termios_1(real_tty->termios_locked,
                                               (struct termios __user *) arg))
                        return -EFAULT;
                        return 0;
#endif
        case TIOCGSOFTCAR:
                return put_user(C_CLOCAL(tty) ? 1 : 0,
                                                (int __user *)arg);
        case TIOCSSOFTCAR:
                if (get_user(arg, (unsigned int __user *) arg))
                        return -EFAULT;
                mutex_lock(&tty->termios_mutex);
                tty->termios->c_cflag =
                        ((tty->termios->c_cflag & ~CLOCAL) |
                         (arg ? CLOCAL : 0));
                mutex_unlock(&tty->termios_mutex);
                return 0;
        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(tty);
        switch (arg) {
        case TCIFLUSH:
                if (ld && ld->flush_buffer)
                        ld->flush_buffer(tty);
                break;
        case TCIOFLUSH:
                if (ld && ld->flush_buffer)
                        ld->flush_buffer(tty);
                /* fall through */
        case TCOFLUSH:
                if (tty->driver->flush_buffer)
                        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(struct tty_struct *tty, struct file *file,
                       unsigned int cmd, unsigned long arg)
{
        struct tty_struct *real_tty;
        int retval;

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

        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 TIOCOUTQ:
                return put_user(tty->driver->chars_in_buffer ?
                                tty->driver->chars_in_buffer(tty) : 0,
                                (int __user *) arg);
        case TIOCINQ:
                retval = tty->read_cnt;
                if (L_ICANON(tty))
                        retval = inq_canon(tty);
                return put_user(retval, (unsigned int __user *) 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;
                if (pktmode) {
                        if (!tty->packet) {
                                tty->packet = 1;
                                tty->link->ctrl_status = 0;
                        }
                } else
                        tty->packet = 0;
                return 0;
        }
        default:
                /* Try the mode commands */
                return tty_mode_ioctl(tty, file, cmd, arg);
        }
}
EXPORT_SYMBOL(n_tty_ioctl);