dgrp_tty.c

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/*
 *
 * Copyright 1999 Digi International (www.digi.com)
 *     Gene Olson    <Gene_Olson at digi dot com>
 *     James Puzzo   <jamesp at digi dot com>
 *     Jeff Randall
 *     Scott Kilau   <scottk at digi dot com>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2, or (at your option)
 * any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY, EXPRESS OR IMPLIED; without even the
 * implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
 * PURPOSE.  See the GNU General Public License for more details.
 *
 */

/*
 *
 *  Filename:
 *
 *     dgrp_tty.c
 *
 *  Description:
 *
 *     This file implements the tty driver functionality for the
 *     RealPort driver software.
 *
 *  Author:
 *
 *     James A. Puzzo
 *     Ann-Marie Westgate
 *
 */

#include <linux/slab.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/sched.h>
#include <linux/uaccess.h>

#include "dgrp_common.h"

#ifndef _POSIX_VDISABLE
#define   _POSIX_VDISABLE ('\0')
#endif

/*
 *  forward declarations
 */

static void drp_param(struct ch_struct *);
static void dgrp_tty_close(struct tty_struct *, struct file *);

/* ioctl helper functions */
static int set_modem_info(struct ch_struct *, unsigned int, unsigned int *);
static int get_modem_info(struct ch_struct *, unsigned int *);
static void dgrp_set_custom_speed(struct ch_struct *, int);
static int dgrp_tty_digigetedelay(struct tty_struct *, int *);
static int dgrp_tty_digisetedelay(struct tty_struct *, int *);
static int dgrp_send_break(struct ch_struct *, int);

static ushort  tty_to_ch_flags(struct tty_struct *, char);
static tcflag_t ch_to_tty_flags(unsigned short, char);

static void dgrp_tty_input_start(struct tty_struct *);
static void dgrp_tty_input_stop(struct tty_struct *);

static void drp_wmove(struct ch_struct *, int, void*, int);

static int dgrp_tty_open(struct tty_struct *, struct file *);
static void dgrp_tty_close(struct tty_struct *, struct file *);
static int dgrp_tty_write(struct tty_struct *, const unsigned char *, int);
static int dgrp_tty_write_room(struct tty_struct *);
static void dgrp_tty_flush_buffer(struct tty_struct *);
static int dgrp_tty_chars_in_buffer(struct tty_struct *);
static int dgrp_tty_ioctl(struct tty_struct *, unsigned int, unsigned long);
static void dgrp_tty_set_termios(struct tty_struct *, struct ktermios *);
static void dgrp_tty_stop(struct tty_struct *);
static void dgrp_tty_start(struct tty_struct *);
static void dgrp_tty_throttle(struct tty_struct *);
static void dgrp_tty_unthrottle(struct tty_struct *);
static void dgrp_tty_hangup(struct tty_struct *);
static int dgrp_tty_put_char(struct tty_struct *, unsigned char);
static int dgrp_tty_tiocmget(struct tty_struct *);
static int dgrp_tty_tiocmset(struct tty_struct *, unsigned int, unsigned int);
static int dgrp_tty_send_break(struct tty_struct *, int);
static void dgrp_tty_send_xchar(struct tty_struct *, char);

/*
 *  tty defines
 */
#define SERIAL_TYPE_NORMAL  1
#define SERIAL_TYPE_CALLOUT 2
#define SERIAL_TYPE_XPRINT  3


/*
 *  tty globals/statics
 */


#define PORTSERVER_DIVIDEND 1843200

/*
 *  Default transparent print information.
 */
static struct digi_struct digi_init = {
    .digi_flags   = DIGI_COOK,  /* Flags            */
    .digi_maxcps  = 100,        /* Max CPS          */
    .digi_maxchar = 50,     /* Max chars in print queue */
    .digi_bufsize = 100,        /* Printer buffer size      */
    .digi_onlen   = 4,      /* size of printer on string    */
    .digi_offlen  = 4,      /* size of printer off string   */
    .digi_onstr   = "\033[5i",  /* ANSI printer on string   */
    .digi_offstr  = "\033[4i",  /* ANSI printer off string  */
    .digi_term    = "ansi"      /* default terminal type    */
};

/*
 *  Define a local default termios struct. All ports will be created
 *  with this termios initially.
 *
 *  This defines a raw port at 9600 baud, 8 data bits, no parity,
 *  1 stop bit.
 */
static struct ktermios DefaultTermios = {
    .c_iflag = (ICRNL | IXON),
    .c_oflag = (OPOST | ONLCR),
    .c_cflag = (B9600 | CS8 | CREAD | HUPCL | CLOCAL),
    .c_lflag = (ISIG | ICANON | ECHO | ECHOE | ECHOK | ECHOCTL
            | ECHOKE | IEXTEN),
    .c_cc    = INIT_C_CC,
    .c_line  = 0,
};

/* Define our tty operations struct */
static const struct tty_operations dgrp_tty_ops = {
    .open            = dgrp_tty_open,
    .close           = dgrp_tty_close,
    .write           = dgrp_tty_write,
    .write_room      = dgrp_tty_write_room,
    .flush_buffer    = dgrp_tty_flush_buffer,
    .chars_in_buffer = dgrp_tty_chars_in_buffer,
    .flush_chars     = NULL,
    .ioctl           = dgrp_tty_ioctl,
    .set_termios     = dgrp_tty_set_termios,
    .stop            = dgrp_tty_stop,
    .start           = dgrp_tty_start,
    .throttle        = dgrp_tty_throttle,
    .unthrottle      = dgrp_tty_unthrottle,
    .hangup          = dgrp_tty_hangup,
    .put_char        = dgrp_tty_put_char,
    .tiocmget        = dgrp_tty_tiocmget,
    .tiocmset        = dgrp_tty_tiocmset,
    .break_ctl       = dgrp_tty_send_break,
    .send_xchar      = dgrp_tty_send_xchar
};


static int calc_baud_rate(struct un_struct *un)
{
    int i;
    int brate;

    struct baud_rates {
        unsigned int rate;
        unsigned int cflag;
    };

    static struct baud_rates baud_rates[] = {
        { 921600, B921600 },
        { 460800, B460800 },
        { 230400, B230400 },
        { 115200, B115200 },
        {  57600, B57600  },
        {  38400, B38400  },
        {  19200, B19200  },
        {   9600, B9600   },
        {   4800, B4800   },
        {   2400, B2400   },
        {   1200, B1200   },
        {    600, B600    },
        {    300, B300    },
        {    200, B200    },
        {    150, B150    },
        {    134, B134    },
        {    110, B110    },
        {     75, B75     },
        {     50, B50     },
        {      0, B9600  }
    };

    brate = C_BAUD(un->un_tty);

    for (i = 0; baud_rates[i].rate; i++) {
        if (baud_rates[i].cflag == brate)
            break;
    }

    return baud_rates[i].rate;
}

static int calc_fastbaud_rate(struct un_struct *un, struct ktermios *uts)
{
    int i;
    int brate;

    ulong bauds[2][16] = {
        { /* fastbaud*/
            0,      57600,   76800, 115200,
            131657, 153600, 230400, 460800,
            921600, 1200,   1800,   2400,
            4800,   9600,   19200,  38400 },
        { /* fastbaud & CBAUDEX */
            0,      57600,  115200, 230400,
            460800, 150,    200,    921600,
            600,    1200,   1800,   2400,
            4800,   9600,   19200,  38400 }
    };

    brate = C_BAUD(un->un_tty) & 0xff;

    i = (uts->c_cflag & CBAUDEX) ? 1 : 0;


    if ((i >= 0) && (i < 2) && (brate >= 0) && (brate < 16))
        brate = bauds[i][brate];
    else
        brate = 0;

    return brate;
}

static void drp_param(struct ch_struct *ch)
{
    struct nd_struct *nd;
    struct un_struct *un;
    int   brate;
    int   mflow;
    int   xflag;
    int   iflag;
    struct ktermios *tts, *pts, *uts;

    nd = ch->ch_nd;

    /*
     *  If the terminal device is open, use it to set up all tty
     *  modes and functions.  Otherwise use the printer device.
     */

    if (ch->ch_tun.un_open_count) {

        un = &ch->ch_tun;
        tts = &ch->ch_tun.un_tty->termios;

        /*
         *  If both devices are open, copy critical line
         *  parameters from the tty device to the printer,
         *  so that if the tty is closed, the printer will
         *  continue without disruption.
         */

        if (ch->ch_pun.un_open_count) {

            pts = &ch->ch_pun.un_tty->termios;

            pts->c_cflag ^=
                (pts->c_cflag ^ tts->c_cflag) &
                (CBAUD  | CSIZE | CSTOPB | CREAD | PARENB |
                 PARODD | HUPCL | CLOCAL);

            pts->c_iflag ^=
                (pts->c_iflag ^ tts->c_iflag) &
                (IGNBRK | BRKINT | IGNPAR | PARMRK | INPCK |
                 ISTRIP | IXON   | IXANY  | IXOFF);

            pts->c_cc[VSTART] = tts->c_cc[VSTART];
            pts->c_cc[VSTOP] = tts->c_cc[VSTOP];
        }
    } else if (ch->ch_pun.un_open_count == 0) {
        pr_warn("%s - ch_pun.un_open_count shouldn't be 0\n",
               __func__);
        return;
    } else {
        un = &ch->ch_pun;
    }

    uts = &un->un_tty->termios;

    /*
     * Determine if FAST writes can be performed.
     */

    if ((ch->ch_digi.digi_flags & DIGI_COOK) != 0 &&
        (ch->ch_tun.un_open_count != 0)  &&
        !((un->un_tty)->ldisc->ops->flags & LDISC_FLAG_DEFINED) &&
        !(L_XCASE(un->un_tty))) {
        ch->ch_flag |= CH_FAST_WRITE;
    } else {
        ch->ch_flag &= ~CH_FAST_WRITE;
    }

    /*
     *  If FAST writes can be performed, and OPOST is on in the
     *  terminal device, do OPOST handling in the server.
     */

    if ((ch->ch_flag & CH_FAST_WRITE) &&
          O_OPOST(un->un_tty) != 0) {
        int oflag = tty_to_ch_flags(un->un_tty, 'o');

        /* add to ch_ocook any processing flags set in the termio */
        ch->ch_ocook |= oflag & (OF_OLCUC |
                     OF_ONLCR |
                     OF_OCRNL |
                     OF_ONLRET |
                     OF_TABDLY);

        /*
         * the hpux driver clears any flags set in ch_ocook
         * from the termios oflag.  It is STILL reported though
         * by a TCGETA
         */

        oflag = ch_to_tty_flags(ch->ch_ocook, 'o');
        uts->c_oflag &= ~oflag;

    } else {
        /* clear the ch->ch_ocook flag */
        int oflag = ch_to_tty_flags(ch->ch_ocook, 'o');
        uts->c_oflag |= oflag;
        ch->ch_ocook = 0;
    }

    ch->ch_oflag = ch->ch_ocook;


    ch->ch_flag &= ~CH_FAST_READ;

    /*
     *  Generate channel flags
     */

    if (C_BAUD(un->un_tty) == B0) {
        if (!(ch->ch_flag & CH_BAUD0)) {
            /* TODO : the HPUX driver flushes line */
            /* TODO : discipline, I assume I don't have to */

            ch->ch_tout = ch->ch_tin;
            ch->ch_rout = ch->ch_rin;

            ch->ch_break_time = 0;

            ch->ch_send |= RR_TX_FLUSH | RR_RX_FLUSH;

            ch->ch_mout &= ~(DM_DTR | DM_RTS);

            ch->ch_flag |= CH_BAUD0;
        }
    } else if (ch->ch_custom_speed) {
        ch->ch_brate = PORTSERVER_DIVIDEND / ch->ch_custom_speed ;

        if (ch->ch_flag & CH_BAUD0) {
            ch->ch_mout |= DM_DTR | DM_RTS;

            ch->ch_flag &= ~CH_BAUD0;
        }
    } else {
        /*
         * Baud rate mapping.
         *
         * If FASTBAUD isn't on, we can scan the new baud rate list
         * as required.
         *
         * However, if FASTBAUD is on, we must go to the old
         * baud rate mapping that existed many many moons ago,
         * for compatibility reasons.
         */

        if (!(ch->ch_digi.digi_flags & DIGI_FAST))
            brate = calc_baud_rate(un);
        else
            brate = calc_fastbaud_rate(un, uts);

        if (brate == 0)
            brate = 9600;

        ch->ch_brate = PORTSERVER_DIVIDEND / brate;

        if (ch->ch_flag & CH_BAUD0) {
            ch->ch_mout |= DM_DTR | DM_RTS;

            ch->ch_flag &= ~CH_BAUD0;
        }
    }

    /*
     *  Generate channel cflags from the termio.
     */

    ch->ch_cflag = tty_to_ch_flags(un->un_tty, 'c');

    /*
     *  Generate channel iflags from the termio.
     */

    iflag = (int) tty_to_ch_flags(un->un_tty, 'i');

    if (START_CHAR(un->un_tty) == _POSIX_VDISABLE ||
        STOP_CHAR(un->un_tty) == _POSIX_VDISABLE) {
        iflag &= ~(IF_IXON | IF_IXANY | IF_IXOFF);
    }

    ch->ch_iflag = iflag;

    /*
     *  Generate flow control characters
     */

    /*
     * From the POSIX.1 spec (7.1.2.6): "If {_POSIX_VDISABLE}
     * is defined for the terminal device file, and the value
     * of one of the changable special control characters (see
     * 7.1.1.9) is {_POSIX_VDISABLE}, that function shall be
     * disabled, that is, no input data shall be recognized as
     * the disabled special character."
     *
     * OK, so we don't ever assign S/DXB XON or XOFF to _POSIX_VDISABLE.
     */

    if (uts->c_cc[VSTART] != _POSIX_VDISABLE)
        ch->ch_xon = uts->c_cc[VSTART];
    if (uts->c_cc[VSTOP] != _POSIX_VDISABLE)
        ch->ch_xoff = uts->c_cc[VSTOP];

    ch->ch_lnext = (uts->c_cc[VLNEXT] == _POSIX_VDISABLE ? 0 :
            uts->c_cc[VLNEXT]);

    /*
     * Also, if either c_cc[START] or c_cc[STOP] is set to
     * _POSIX_VDISABLE, we can't really do software flow
     * control--in either direction--so we turn it off as
     * far as S/DXB is concerned.  In essence, if you disable
     * one, you disable the other too.
     */
    if ((uts->c_cc[VSTART] == _POSIX_VDISABLE) ||
        (uts->c_cc[VSTOP] == _POSIX_VDISABLE))
        ch->ch_iflag &= ~(IF_IXOFF | IF_IXON);

    /*
     *  Update xflags.
     */

    xflag = 0;

    if (ch->ch_digi.digi_flags & DIGI_AIXON)
        xflag = XF_XIXON;

    if ((ch->ch_xxon == _POSIX_VDISABLE) ||
        (ch->ch_xxoff == _POSIX_VDISABLE))
        xflag &= ~XF_XIXON;

    ch->ch_xflag = xflag;


    /*
     *  Figure effective DCD value.
     */

    if (C_CLOCAL(un->un_tty))
        ch->ch_flag |= CH_CLOCAL;
    else
        ch->ch_flag &= ~CH_CLOCAL;

    /*
     *  Check modem signals
     */

    dgrp_carrier(ch);

    /*
     *  Get hardware handshake value.
     */

    mflow = 0;

    if (C_CRTSCTS(un->un_tty))
        mflow |= (DM_RTS | DM_CTS);

    if (ch->ch_digi.digi_flags & RTSPACE)
        mflow |= DM_RTS;

    if (ch->ch_digi.digi_flags & DTRPACE)
        mflow |= DM_DTR;

    if (ch->ch_digi.digi_flags & CTSPACE)
        mflow |= DM_CTS;

    if (ch->ch_digi.digi_flags & DSRPACE)
        mflow |= DM_DSR;

    if (ch->ch_digi.digi_flags & DCDPACE)
        mflow |= DM_CD;

    if (ch->ch_digi.digi_flags & DIGI_RTS_TOGGLE)
        mflow |= DM_RTS_TOGGLE;

    ch->ch_mflow = mflow;

    /*
     *  Send the changes to the server.
     */

    ch->ch_flag |= CH_PARAM;
    (ch->ch_nd)->nd_tx_work = 1;

    if (waitqueue_active(&ch->ch_flag_wait))
        wake_up_interruptible(&ch->ch_flag_wait);
}

/*
 * This function is just used as a callback for timeouts
 * waiting on the ch_sleep flag.
 */
static void wake_up_drp_sleep_timer(unsigned long ptr)
{
    struct ch_struct *ch = (struct ch_struct *) ptr;
    if (ch)
        wake_up(&ch->ch_sleep);
}


/*
 * Set up our own sleep that can't be cancelled
 * until our timeout occurs.
 */
static void drp_my_sleep(struct ch_struct *ch)
{
    struct timer_list drp_wakeup_timer;
    DECLARE_WAITQUEUE(wait, current);

    /*
     * First make sure we're ready to receive the wakeup.
     */

    add_wait_queue(&ch->ch_sleep, &wait);
    current->state = TASK_UNINTERRUPTIBLE;

    /*
     * Since we are uninterruptible, set a timer to
     * unset the uninterruptable state in 1 second.
     */

    init_timer(&drp_wakeup_timer);
    drp_wakeup_timer.function = wake_up_drp_sleep_timer;
    drp_wakeup_timer.data = (unsigned long) ch;
    drp_wakeup_timer.expires = jiffies + (1 * HZ);
    add_timer(&drp_wakeup_timer);

    schedule();

    del_timer(&drp_wakeup_timer);

    remove_wait_queue(&ch->ch_sleep, &wait);
}

/*
 * dgrp_tty_open()
 *
 * returns:
 *    -EBUSY    - this is a callout device and the normal device is active
 *              - there is an error in opening the tty
 *    -ENODEV   - the channel does not exist
 *    -EAGAIN   - we are in the middle of hanging up or closing
 *              - IMMEDIATE_OPEN fails
 *    -ENXIO or -EAGAIN
 *              - if the port is outside physical range
 *    -EINTR    - the open is interrupted
 *
 */
static int dgrp_tty_open(struct tty_struct *tty, struct file *file)
{
    int    retval = 0;
    struct nd_struct  *nd;
    struct ch_struct *ch;
    struct un_struct  *un;
    int    port;
    int    delay_error;
    int    otype;
    int    unf;
    int    wait_carrier;
    int    category;
    int    counts_were_incremented = 0;
    ulong lock_flags;
    DECLARE_WAITQUEUE(wait, current);

    /*
     * Do some initial checks to see if the node and port exist
     */

    nd = nd_struct_get(MAJOR(tty_devnum(tty)));
    port = PORT_NUM(MINOR(tty_devnum(tty)));
    category = OPEN_CATEGORY(MINOR(tty_devnum(tty)));

    if (!nd)
        return -ENODEV;

    if (port >= CHAN_MAX)
        return -ENODEV;

    /*
     *  The channel exists.
     */

    ch = nd->nd_chan + port;

    un = IS_PRINT(MINOR(tty_devnum(tty))) ? &ch->ch_pun : &ch->ch_tun;
    un->un_tty = tty;
    tty->driver_data = un;

    /*
     * If we are in the middle of hanging up,
     * then return an error
     */
    if (tty_hung_up_p(file)) {
        retval = ((un->un_flag & UN_HUP_NOTIFY) ?
               -EAGAIN : -ERESTARTSYS);
        goto done;
    }

    /*
     * If the port is in the middle of closing, then block
     * until it is done, then try again.
     */
    retval = wait_event_interruptible(un->un_close_wait,
            ((un->un_flag & UN_CLOSING) == 0));

    if (retval)
        goto done;

    /*
     * If the port is in the middle of a reopen after a network disconnect,
     * wait until it is done, then try again.
     */
    retval = wait_event_interruptible(ch->ch_flag_wait,
            ((ch->ch_flag & CH_PORT_GONE) == 0));

    if (retval)
        goto done;

    /*
     * If this is a callout device, then just make sure the normal
     * device isn't being used.
     */

    if (tty->driver->subtype == SERIAL_TYPE_CALLOUT) {
        if (un->un_flag & UN_NORMAL_ACTIVE) {
            retval = -EBUSY;
            goto done;
        } else {
            un->un_flag |= UN_CALLOUT_ACTIVE;
        }
    }

    /*
     *  Loop waiting until the open can be successfully completed.
     */

    spin_lock_irqsave(&nd->nd_lock, lock_flags);

    nd->nd_tx_work = 1;

    for (;;) {
        wait_carrier = 0;

        /*
         * Determine the open type from the flags provided.
         */

        /*
         * If the port is not enabled, then exit
         */
        if (test_bit(TTY_IO_ERROR, &tty->flags)) {
            /* there was an error in opening the tty */
            if (un->un_flag & UN_CALLOUT_ACTIVE)
                retval = -EBUSY;
            else
                un->un_flag |= UN_NORMAL_ACTIVE;
            goto unlock;
        }

        if (file->f_flags & O_NONBLOCK) {

            /*
             * if the O_NONBLOCK is set, errors on read and write
             * must return -EAGAIN immediately and NOT sleep
             * on the waitqs.
             */
            otype = OTYPE_IMMEDIATE;
            delay_error = -EAGAIN;

        } else if (!OPEN_WAIT_AVAIL(category) ||
              (file->f_flags & O_NDELAY) != 0) {
            otype = OTYPE_IMMEDIATE;
            delay_error = -EBUSY;

        } else if (!OPEN_WAIT_CARRIER(category) ||
              ((ch->ch_digi.digi_flags & DIGI_FORCEDCD) != 0) ||
              C_CLOCAL(tty)) {
            otype = OTYPE_PERSISTENT;
            delay_error = 0;

        } else {
            otype = OTYPE_INCOMING;
            delay_error = 0;
        }

        /*
         * Handle port currently outside physical port range.
         */

        if (port >= nd->nd_chan_count) {
            if (otype == OTYPE_IMMEDIATE) {
                retval = (nd->nd_state == NS_READY) ?
                        -ENXIO : -EAGAIN;
                goto unlock;
            }
        }

        /*
         *  Handle port not currently open.
         */

        else if (ch->ch_open_count == 0) {
            /*
             * Return an error when an Incoming Open
             * response indicates the port is busy.
             */

            if (ch->ch_open_error != 0 && otype == ch->ch_otype) {
                retval = (ch->ch_open_error <= 2) ?
                      delay_error : -ENXIO ;
                goto unlock;
            }

            /*
             * Fail any new Immediate open if we do not have
             * a normal connection to the server.
             */

            if (nd->nd_state != NS_READY &&
                otype == OTYPE_IMMEDIATE) {
                retval = -EAGAIN;
                goto unlock;
            }

            /*
             * If a Realport open of the correct type has
             * succeeded, complete the open.
             */

            if (ch->ch_state == CS_READY && ch->ch_otype == otype)
                break;
        }

        /*
         * Handle port already open and active as a device
         * of same category.
         */

        else if ((ch->ch_category == category) ||
              IS_PRINT(MINOR(tty_devnum(tty)))) {
            /*
             * Fail if opening the device now would
             * violate exclusive use.
             */
            unf = ch->ch_tun.un_flag | ch->ch_pun.un_flag;

            if ((file->f_flags & O_EXCL) || (unf & UN_EXCL)) {
                retval = -EBUSY;
                goto unlock;
            }

            /*
             * If the open device is in the hangup state, all
             * system calls fail except close().
             */

            /* TODO : check on hangup_p calls */

            if (ch->ch_flag & CH_HANGUP) {
                retval = -ENXIO;
                goto unlock;
            }

            /*
             * If the port is ready, and carrier is ignored
             * or present, then complete the open.
             */

            if (ch->ch_state == CS_READY &&
                (otype != OTYPE_INCOMING ||
                ch->ch_flag & CH_VIRT_CD))
                break;

            wait_carrier = 1;
        }

        /*
         *  Handle port active with a different category device.
         */

        else {
            if (otype == OTYPE_IMMEDIATE) {
                retval = delay_error;
                goto unlock;
            }
        }

        /*
         * Wait until conditions change, then take another
         * try at the open.
         */

        ch->ch_wait_count[otype]++;

        if (wait_carrier)
            ch->ch_wait_carrier++;

        /*
         * Prepare the task to accept the wakeup, then
         * release our locks and release control.
         */

        add_wait_queue(&ch->ch_flag_wait, &wait);
        current->state = TASK_INTERRUPTIBLE;

        spin_unlock_irqrestore(&nd->nd_lock, lock_flags);

        /*
         * Give up control, we'll come back if we're
         * interrupted or are woken up.
         */
        schedule();
        remove_wait_queue(&ch->ch_flag_wait, &wait);

        spin_lock_irqsave(&nd->nd_lock, lock_flags);

        current->state = TASK_RUNNING;

        ch->ch_wait_count[otype]--;

        if (wait_carrier)
            ch->ch_wait_carrier--;

        nd->nd_tx_work = 1;

        if (signal_pending(current)) {
            retval = -EINTR;
            goto unlock;
        }
    } /* end for(;;) */

    /*
     *  The open has succeeded.  No turning back.
     */
    counts_were_incremented = 1;
    un->un_open_count++;
    ch->ch_open_count++;

    /*
     * Initialize the channel, if it's not already open.
     */

    if (ch->ch_open_count == 1) {
        ch->ch_flag = 0;
        ch->ch_inwait = 0;
        ch->ch_category = category;
        ch->ch_pscan_state = 0;

        /* TODO : find out what PS-1 bug Gene was referring to */
        /* TODO : in the following comment. */

        ch->ch_send = RR_TX_START | RR_RX_START;  /* PS-1 bug */

        if (C_CLOCAL(tty) ||
            ch->ch_s_mlast & DM_CD ||
            ch->ch_digi.digi_flags & DIGI_FORCEDCD)
            ch->ch_flag |= CH_VIRT_CD;
        else if (OPEN_FORCES_CARRIER(category))
            ch->ch_flag |= CH_VIRT_CD;

    }

    /*
     *  Initialize the unit, if it is not already open.
     */

    if (un->un_open_count == 1) {
        /*
         *  Since all terminal options are always sticky in Linux,
         *  we don't need the UN_STICKY flag to be handled specially.
         */
        /* clears all the digi flags, leaves serial flags */
        un->un_flag &= ~UN_DIGI_MASK;

        if (file->f_flags & O_EXCL)
            un->un_flag |= UN_EXCL;

        /* TODO : include "session" and "pgrp" */

        /*
         *  In Linux, all terminal parameters are intended to be sticky.
         *  as a result, we "remove" the code which once reset the ports
         *  to sane values.
         */

        drp_param(ch);

    }

    un->un_flag |= UN_INITIALIZED;

    retval = 0;

unlock:

    spin_unlock_irqrestore(&nd->nd_lock, lock_flags);

done:
    /*
     * Linux does a close for every open, even failed ones!
     */
    if (!counts_were_incremented) {
        un->un_open_count++;
        ch->ch_open_count++;
    }

    if (retval)
        dev_err(tty->dev, "tty open bad return (%i)\n", retval);

    return retval;
}




/*
 * dgrp_tty_close() -- close function for tty_operations
 */
static void dgrp_tty_close(struct tty_struct *tty, struct file *file)
{
    struct ch_struct *ch;
    struct un_struct *un;
    struct nd_struct *nd;
    int tpos;
    int port;
    int err = 0;
    int s = 0;
    ulong  waketime;
    ulong  lock_flags;
    int sent_printer_offstr = 0;

    port = PORT_NUM(MINOR(tty_devnum(tty)));

    un = tty->driver_data;

    if (!un)
        return;

    ch = un->un_ch;

    if (!ch)
        return;

    nd = ch->ch_nd;

    if (!nd)
        return;

    spin_lock_irqsave(&nd->nd_lock, lock_flags);


    /* Used to be on channel basis, now we check on a unit basis. */
    if (un->un_open_count != 1)
        goto unlock;

    /*
     * OK, its the last close on the unit
     */
    un->un_flag |= UN_CLOSING;

    /*
     * Notify the discipline to only process XON/XOFF characters.
     */
    tty->closing = 1;

    /*
     * Wait for output to drain only if this is
     * the last close against the channel
     */

    if (ch->ch_open_count == 1) {
        /*
         * If its the print device, we need to ensure at all costs that
         * the offstr will fit. If it won't, flush our tbuf.
         */
        if (IS_PRINT(MINOR(tty_devnum(tty))) &&
            (((ch->ch_tout - ch->ch_tin - 1) & TBUF_MASK) <
            ch->ch_digi.digi_offlen))
            ch->ch_tin = ch->ch_tout;

        /*
         * Turn off the printer.  Don't bother checking to see if its
         * IS_PRINT... Since this is the last close the flag is going
         * to be cleared, so we MUST make sure the offstr gets inserted
         * into tbuf.
         */

        if ((ch->ch_flag & CH_PRON) != 0) {
            drp_wmove(ch, 0, ch->ch_digi.digi_offstr,
                  ch->ch_digi.digi_offlen);
            ch->ch_flag &= ~CH_PRON;
            sent_printer_offstr = 1;
        }
    }

    /*
     *  Wait until either the output queue has drained, or we see
     *  absolutely no progress for 15 seconds.
     */

    tpos = ch->ch_s_tpos;

    waketime = jiffies + 15 * HZ;

    for (;;) {

        /*
         *  Make sure the port still exists.
         */

        if (port >= nd->nd_chan_count) {
            err = 1;
            break;
        }

        if (signal_pending(current)) {
            err = 1;
            break;
        }

        /*
         * If the port is idle (not opened on the server), we have
         * no way of draining/flushing/closing the port on that server.
         * So break out of loop.
         */
        if (ch->ch_state == CS_IDLE)
            break;

        nd->nd_tx_work = 1;

        /*
         *  Exit if the queues for this unit are empty,
         *  and either the other unit is still open or all
         *  data has drained.
         */

        if ((un->un_tty)->ops->chars_in_buffer ?
            ((un->un_tty)->ops->chars_in_buffer)(un->un_tty) == 0 : 1) {

            /*
             * We don't need to wait for a buffer to drain
             * if the other unit is open.
             */

            if (ch->ch_open_count != un->un_open_count)
                break;

            /*
             *  The wait is complete when all queues are
             *  drained, and any break in progress is complete.
             */

            if (ch->ch_tin == ch->ch_tout &&
                ch->ch_s_tin == ch->ch_s_tpos &&
                (ch->ch_send & RR_TX_BREAK) == 0) {
                break;
            }
        }

        /*
         * Flush TX data and exit the wait if NDELAY is set,
         * or this is not a DIGI printer, and the close timeout
         * expires.
         */

        if ((file->f_flags & (O_NDELAY | O_NONBLOCK)) ||
            ((long)(jiffies - waketime) >= 0 &&
              (ch->ch_digi.digi_flags & DIGI_PRINTER) == 0)) {

                /*
                 * If we sent the printer off string, we cannot
                 * flush our internal buffers, or we might lose
                 * the offstr.
                 */
                if (!sent_printer_offstr)
                    dgrp_tty_flush_buffer(tty);

                tty_ldisc_flush(tty);
                break;
        }

        /*
         *  Otherwise take a short nap.
         */

        ch->ch_flag |= CH_DRAIN;

        spin_unlock_irqrestore(&nd->nd_lock, lock_flags);

        schedule_timeout_interruptible(1);
        s = signal_pending(current);

        spin_lock_irqsave(&nd->nd_lock, lock_flags);

        if (s) {
            /*
             * If we had sent the printer off string, we now have
             * some problems.
             *
             * The system won't let us sleep since we got an error
             * back from sleep, presumably because the user did
             * a ctrl-c...
             * But we need to ensure that the offstr gets sent!
             * Thus, we have to do something else besides sleeping.
             * The plan:
             * 1) Make this task uninterruptable.
             * 2) Set up a timer to go off in 1 sec.
             * 3) Act as tho we just got out of the sleep above.
             *
             * Thankfully, in the real world, this just
             * never happens.
             */

            if (sent_printer_offstr) {
                spin_unlock_irqrestore(&nd->nd_lock,
                               lock_flags);
                drp_my_sleep(ch);
                spin_lock_irqsave(&nd->nd_lock, lock_flags);
            } else {
                err = 1;
                break;
            }
        }

        /*
         *  Restart the wait if any progress is seen.
         */

        if (ch->ch_s_tpos != tpos) {
            tpos = ch->ch_s_tpos;

            /* TODO:  this gives us timeout problems with nist ?? */
            waketime = jiffies + 15 * HZ;
        }
    }

    /*
     *  Close the line discipline
     */

    /* this is done in tty_io.c */
    /* if ((un->un_tty)->ldisc.close)
     *  ((un->un_tty)->ldisc.close)(un->un_tty);
     */

    /* don't do this here */
    /* un->un_flag = 0; */

    /*
     *  Flush the receive buffer on terminal unit close only.
     */

    if (!IS_PRINT(MINOR(tty_devnum(tty))))
        ch->ch_rout = ch->ch_rin;


    /*
     * Don't permit the close to happen until we get any pending
     * sync request responses.
     * There could be other ports depending upon the response as well.
     *
     * Also, don't permit the close to happen until any parameter
     * changes have been sent out from the state machine as well.
     * This is required because of a ditty -a race with -HUPCL
     * We MUST make sure all channel parameters have been sent to the
     * Portserver before sending a close.
     */

    if ((err != 1) && (ch->ch_state != CS_IDLE)) {
        spin_unlock_irqrestore(&nd->nd_lock, lock_flags);
        s = wait_event_interruptible(ch->ch_flag_wait,
            ((ch->ch_flag & (CH_WAITING_SYNC | CH_PARAM)) == 0));
        spin_lock_irqsave(&nd->nd_lock, lock_flags);
    }

    /*
     * Cleanup the channel if last unit open.
     */

    if (ch->ch_open_count == 1) {
        ch->ch_flag = 0;
        ch->ch_category = 0;
        ch->ch_send = 0;
        ch->ch_expect = 0;
        ch->ch_tout = ch->ch_tin;
        /* (un->un_tty)->device = 0; */

        if (ch->ch_state == CS_READY)
            ch->ch_state = CS_SEND_CLOSE;
    }

    /*
     * Send the changes to the server
     */
    if (ch->ch_state != CS_IDLE) {
        ch->ch_flag |= CH_PARAM;
        wake_up_interruptible(&ch->ch_flag_wait);
    }

    nd->nd_tx_work = 1;
    nd->nd_tx_ready = 1;

unlock:
    tty->closing = 0;

    if (ch->ch_open_count <= 0)
        dev_info(tty->dev,
             "%s - unexpected value for ch->ch_open_count: %i\n",
             __func__, ch->ch_open_count);
    else
        ch->ch_open_count--;

    if (un->un_open_count <= 0)
        dev_info(tty->dev,
             "%s - unexpected value for un->un_open_count: %i\n",
             __func__, un->un_open_count);
    else
        un->un_open_count--;

    un->un_flag &= ~(UN_NORMAL_ACTIVE | UN_CALLOUT_ACTIVE | UN_CLOSING);
    if (waitqueue_active(&un->un_close_wait))
        wake_up_interruptible(&un->un_close_wait);

    spin_unlock_irqrestore(&nd->nd_lock, lock_flags);

    return;

}

static void drp_wmove(struct ch_struct *ch, int from_user, void *buf, int count)
{
    int n;
    int ret = 0;

    ch->ch_nd->nd_tx_work = 1;

    n = TBUF_MAX - ch->ch_tin;

    if (count >= n) {
        if (from_user)
            ret = copy_from_user(ch->ch_tbuf + ch->ch_tin,
                         (void __user *) buf, n);
        else
            memcpy(ch->ch_tbuf + ch->ch_tin, buf, n);

        buf = (char *) buf + n;
        count -= n;
        ch->ch_tin = 0;
    }

    if (from_user)
        ret = copy_from_user(ch->ch_tbuf + ch->ch_tin,
                     (void __user *) buf, count);
    else
        memcpy(ch->ch_tbuf + ch->ch_tin, buf, count);

    ch->ch_tin += count;
}


static int dgrp_calculate_txprint_bounds(struct ch_struct *ch, int space,
                     int *un_flag)
{
    clock_t tt;
    clock_t mt;
    unsigned short tmax = 0;

    /*
     * If the terminal device is busy, reschedule when
     * the terminal device becomes idle.
     */

    if (ch->ch_tun.un_open_count != 0 &&
        ch->ch_tun.un_tty->ops->chars_in_buffer &&
        ((ch->ch_tun.un_tty->ops->chars_in_buffer)(ch->ch_tun.un_tty) != 0)) {
        *un_flag = UN_PWAIT;
        return 0;
    }

    /*
     * Assure that whenever there is printer data in the output
     * buffer, there always remains enough space after it to
     * turn the printer off.
     */
    space -= ch->ch_digi.digi_offlen;

    if (space <= 0) {
        *un_flag = UN_EMPTY;
        return 0;
    }

    /*
     * We measure printer CPS speed by incrementing
     * ch_cpstime by (HZ / digi_maxcps) for every
     * character we output, restricting output so
     * that ch_cpstime never exceeds lbolt.
     *
     * However if output has not been done for some
     * time, lbolt will grow to very much larger than
     * ch_cpstime, which would allow essentially
     * unlimited amounts of output until ch_cpstime
     * finally caught up.   To avoid this, we adjust
     * cps_time when necessary so the difference
     * between lbolt and ch_cpstime never results
     * in sending more than digi_bufsize characters.
     *
     * This nicely models a printer with an internal
     * buffer of digi_bufsize characters.
     *
     * Get the time between lbolt and ch->ch_cpstime;
     */

    tt = jiffies - ch->ch_cpstime;

    /*
     * Compute the time required to send digi_bufsize
     * characters.
     */

    mt = HZ * ch->ch_digi.digi_bufsize / ch->ch_digi.digi_maxcps;

    /*
     * Compute the number of characters that can be sent
     * without violating the time constraint.   If the
     * direct calculation of this number is bigger than
     * digi_bufsize, limit the number to digi_bufsize,
     * and adjust cpstime to match.
     */

    if ((clock_t)(tt + HZ) > (clock_t)(mt + HZ)) {
        tmax = ch->ch_digi.digi_bufsize;
        ch->ch_cpstime = jiffies - mt;
    } else {
        tmax = ch->ch_digi.digi_maxcps * tt / HZ;
    }

    /*
     * If the time constraint now binds, limit the transmit
     * count accordingly, and tentatively arrange to be
     * rescheduled based on time.
     */

    if (tmax < space) {
        *un_flag = UN_TIME;
        space = tmax;
    }

    /*
     * Compute the total number of characters we can
     * output before the total number of characters known
     * to be in the output queue exceeds digi_maxchar.
     */

    tmax = (ch->ch_digi.digi_maxchar -
        ((ch->ch_tin - ch->ch_tout) & TBUF_MASK) -
        ((ch->ch_s_tin - ch->ch_s_tpos) & 0xffff));


    /*
     * If the digi_maxchar constraint now holds, limit
     * the transmit count accordingly, and arrange to
     * be rescheduled when the queue becomes empty.
     */

    if (space > tmax) {
        *un_flag = UN_EMPTY;
        space = tmax;
    }

    if (space <= 0)
        *un_flag |= UN_EMPTY;

    return space;
}


static int dgrp_tty_write(struct tty_struct *tty,
              const unsigned char *buf,
              int count)
{
    struct nd_struct *nd;
    struct un_struct *un;
    struct ch_struct *ch;
    int space;
    int n;
    int t;
    int sendcount;
    int un_flag;
    ulong lock_flags;

    if (tty == NULL)
        return 0;

    un = tty->driver_data;
    if (!un)
        return 0;

    ch = un->un_ch;
    if (!ch)
        return 0;

    nd = ch->ch_nd;
    if (!nd)
        return 0;

    /*
     * Ignore the request if the channel is not ready.
     */
    if (ch->ch_state != CS_READY)
        return 0;

    spin_lock_irqsave(&dgrp_poll_data.poll_lock, lock_flags);

    /*
     * Ignore the request if output is blocked.
     */
    if ((un->un_flag & (UN_EMPTY | UN_LOW | UN_TIME | UN_PWAIT)) != 0) {
        count = 0;
        goto out;
    }

    /*
     * Also ignore the request if DPA has this port open,
     * and is flow controlled on reading more data.
     */
    if (nd->nd_dpa_debug && nd->nd_dpa_flag & DPA_WAIT_SPACE &&
        nd->nd_dpa_port == MINOR(tty_devnum(ch->ch_tun.un_tty))) {
        count = 0;
        goto out;
    }

    /*
     *  Limit amount we will write to the amount of space
     *  available in the channel buffer.
     */
    sendcount = 0;

    space = (ch->ch_tout - ch->ch_tin - 1) & TBUF_MASK;

    /*
     * Handle the printer device.
     */

    un_flag = UN_LOW;

    if (IS_PRINT(MINOR(tty_devnum(tty)))) {
        clock_t tt;
        clock_t mt;
        unsigned short tmax = 0;

        /*
         * If the terminal device is busy, reschedule when
         * the terminal device becomes idle.
         */

        if (ch->ch_tun.un_open_count != 0 &&
            ((ch->ch_tun.un_tty->ops->chars_in_buffer)(ch->ch_tun.un_tty) != 0)) {
            un->un_flag |= UN_PWAIT;
            count = 0;
            goto out;
        }

        /*
         * Assure that whenever there is printer data in the output
         * buffer, there always remains enough space after it to
         * turn the printer off.
         */
        space -= ch->ch_digi.digi_offlen;

        /*
         * Output the printer on string.
         */

        if ((ch->ch_flag & CH_PRON) == 0) {
            space -= ch->ch_digi.digi_onlen;

            if (space < 0) {
                un->un_flag |= UN_EMPTY;
                (ch->ch_nd)->nd_tx_work = 1;
                count = 0;
                goto out;
            }

            drp_wmove(ch, 0, ch->ch_digi.digi_onstr,
                ch->ch_digi.digi_onlen);

            ch->ch_flag |= CH_PRON;
        }

        /*
         * We measure printer CPS speed by incrementing
         * ch_cpstime by (HZ / digi_maxcps) for every
         * character we output, restricting output so
         * that ch_cpstime never exceeds lbolt.
         *
         * However if output has not been done for some
         * time, lbolt will grow to very much larger than
         * ch_cpstime, which would allow essentially
         * unlimited amounts of output until ch_cpstime
         * finally caught up.   To avoid this, we adjust
         * cps_time when necessary so the difference
         * between lbolt and ch_cpstime never results
         * in sending more than digi_bufsize characters.
         *
         * This nicely models a printer with an internal
         * buffer of digi_bufsize characters.
         *
         * Get the time between lbolt and ch->ch_cpstime;
         */

        tt = jiffies - ch->ch_cpstime;

        /*
         * Compute the time required to send digi_bufsize
         * characters.
         */

        mt = HZ * ch->ch_digi.digi_bufsize / ch->ch_digi.digi_maxcps;

        /*
         * Compute the number of characters that can be sent
         * without violating the time constraint.   If the
         * direct calculation of this number is bigger than
         * digi_bufsize, limit the number to digi_bufsize,
         * and adjust cpstime to match.
         */

        if ((clock_t)(tt + HZ) > (clock_t)(mt + HZ)) {
            tmax = ch->ch_digi.digi_bufsize;
            ch->ch_cpstime = jiffies - mt;
        } else {
            tmax = ch->ch_digi.digi_maxcps * tt / HZ;
        }

        /*
         * If the time constraint now binds, limit the transmit
         * count accordingly, and tentatively arrange to be
         * rescheduled based on time.
         */

        if (tmax < space) {
            space = tmax;
            un_flag = UN_TIME;
        }

        /*
         * Compute the total number of characters we can
         * output before the total number of characters known
         * to be in the output queue exceeds digi_maxchar.
         */

        tmax = (ch->ch_digi.digi_maxchar -
            ((ch->ch_tin - ch->ch_tout) & TBUF_MASK) -
            ((ch->ch_s_tin - ch->ch_s_tpos) & 0xffff));


        /*
         * If the digi_maxchar constraint now holds, limit
         * the transmit count accordingly, and arrange to
         * be rescheduled when the queue becomes empty.
         */

        if (space > tmax) {
            space = tmax;
            un_flag = UN_EMPTY;
        }

    }
    /*
     * Handle the terminal device.
     */
    else {

        /*
         * If the printer device is on, turn it off.
         */

        if ((ch->ch_flag & CH_PRON) != 0) {

            space -= ch->ch_digi.digi_offlen;

            drp_wmove(ch, 0, ch->ch_digi.digi_offstr,
                  ch->ch_digi.digi_offlen);

            ch->ch_flag &= ~CH_PRON;
        }
    }

    /*
     *  If space is 0 and its because the ch->tbuf
     *  is full, then Linux will handle a callback when queue
     *  space becomes available.
     *  tty_write returns count = 0
     */

    if (space <= 0) {
        /* the linux tty_io.c handles this if we return 0 */
        /* if (fp->flags & O_NONBLOCK) return -EAGAIN; */

        un->un_flag |= UN_EMPTY;
        (ch->ch_nd)->nd_tx_work = 1;
        count = 0;
        goto out;
    }

    count = min(count, space);

    if (count > 0) {

        un->un_tbusy++;

        /*
         *  Copy the buffer contents to the ch_tbuf
         *  being careful to wrap around the circular queue
         */

        t = TBUF_MAX - ch->ch_tin;
        n = count;

        if (n >= t) {
            memcpy(ch->ch_tbuf + ch->ch_tin, buf, t);
            if (nd->nd_dpa_debug && nd->nd_dpa_port == PORT_NUM(MINOR(tty_devnum(un->un_tty))))
                dgrp_dpa_data(nd, 0, (char *) buf, t);
            buf += t;
            n -= t;
            ch->ch_tin = 0;
            sendcount += n;
        }

        memcpy(ch->ch_tbuf + ch->ch_tin, buf, n);
        if (nd->nd_dpa_debug && nd->nd_dpa_port == PORT_NUM(MINOR(tty_devnum(un->un_tty))))
            dgrp_dpa_data(nd, 0, (char *) buf, n);
        buf += n;
        ch->ch_tin += n;
        sendcount += n;

        un->un_tbusy--;
        (ch->ch_nd)->nd_tx_work = 1;
        if (ch->ch_edelay != DGRP_RTIME) {
            (ch->ch_nd)->nd_tx_ready = 1;
            wake_up_interruptible(&nd->nd_tx_waitq);
        }
    }

    ch->ch_txcount += count;

    if (IS_PRINT(MINOR(tty_devnum(tty)))) {

        /*
         * Adjust ch_cpstime to account
         * for the characters just output.
         */

        if (sendcount > 0) {
            int cc = HZ * sendcount + ch->ch_cpsrem;

            ch->ch_cpstime += cc / ch->ch_digi.digi_maxcps;
            ch->ch_cpsrem   = cc % ch->ch_digi.digi_maxcps;
        }

        /*
         * If we are now waiting on time, schedule ourself
         * back when we'll be able to send a block of
         * digi_maxchar characters.
         */

        if ((un_flag & UN_TIME) != 0) {
            ch->ch_waketime = (ch->ch_cpstime +
                (ch->ch_digi.digi_maxchar * HZ /
                ch->ch_digi.digi_maxcps));
        }
    }

    /*
     * If the printer unit is waiting for completion
     * of terminal output, get him going again.
     */

    if ((ch->ch_pun.un_flag & UN_PWAIT) != 0)
        (ch->ch_nd)->nd_tx_work = 1;

out:
    spin_unlock_irqrestore(&dgrp_poll_data.poll_lock, lock_flags);

    return count;
}


/*
 *  Put a character into ch->ch_buf
 *
 *  - used by the line discipline for OPOST processing
 */

static int dgrp_tty_put_char(struct tty_struct *tty, unsigned char new_char)
{
    struct un_struct *un;
    struct ch_struct *ch;
    ulong  lock_flags;
    int space;
    int retval = 0;

    if (tty == NULL)
        return 0;

    un = tty->driver_data;
    if (!un)
        return 0;

    ch = un->un_ch;
    if (!ch)
        return 0;

    if (ch->ch_state != CS_READY)
        return 0;

    spin_lock_irqsave(&dgrp_poll_data.poll_lock, lock_flags);


    /*
     *  If space is 0 and its because the ch->tbuf
     *  Warn and dump the character, there isn't anything else
     *  we can do about it.  [email protected]
     */

    space = (ch->ch_tout - ch->ch_tin - 1) & TBUF_MASK;

    un->un_tbusy++;

    /*
     * Output the printer on string if device is TXPrint.
     */
    if (IS_PRINT(MINOR(tty_devnum(tty))) && (ch->ch_flag & CH_PRON) == 0) {
        if (space < ch->ch_digi.digi_onlen) {
            un->un_tbusy--;
            goto out;
        }
        space -= ch->ch_digi.digi_onlen;
        drp_wmove(ch, 0, ch->ch_digi.digi_onstr,
              ch->ch_digi.digi_onlen);
        ch->ch_flag |= CH_PRON;
    }

    /*
     * Output the printer off string if device is NOT TXPrint.
     */

    if (!IS_PRINT(MINOR(tty_devnum(tty))) &&
        ((ch->ch_flag & CH_PRON) != 0)) {
        if (space < ch->ch_digi.digi_offlen) {
            un->un_tbusy--;
            goto out;
        }

        space -= ch->ch_digi.digi_offlen;
        drp_wmove(ch, 0, ch->ch_digi.digi_offstr,
              ch->ch_digi.digi_offlen);
        ch->ch_flag &= ~CH_PRON;
    }

    if (!space) {
        un->un_tbusy--;
        goto out;
    }

    /*
     *  Copy the character to the ch_tbuf being
     *  careful to wrap around the circular queue
     */
    ch->ch_tbuf[ch->ch_tin] = new_char;
    ch->ch_tin = (1 + ch->ch_tin) & TBUF_MASK;

    if (IS_PRINT(MINOR(tty_devnum(tty)))) {

        /*
         * Adjust ch_cpstime to account
         * for the character just output.
         */

        int cc = HZ + ch->ch_cpsrem;

        ch->ch_cpstime += cc / ch->ch_digi.digi_maxcps;
        ch->ch_cpsrem   = cc % ch->ch_digi.digi_maxcps;

        /*
         * If we are now waiting on time, schedule ourself
         * back when we'll be able to send a block of
         * digi_maxchar characters.
         */

        ch->ch_waketime = (ch->ch_cpstime +
            (ch->ch_digi.digi_maxchar * HZ /
            ch->ch_digi.digi_maxcps));
    }


    un->un_tbusy--;
    (ch->ch_nd)->nd_tx_work = 1;

    retval = 1;
out:
    spin_unlock_irqrestore(&dgrp_poll_data.poll_lock, lock_flags);
    return retval;
}



/*
 *  Flush TX buffer (make in == out)
 *
 *  check tty_ioctl.c  -- this is called after TCOFLUSH
 */
static void dgrp_tty_flush_buffer(struct tty_struct *tty)
{
    struct un_struct *un;
    struct ch_struct *ch;

    if (!tty)
        return;
    un = tty->driver_data;
    if (!un)
        return;

    ch = un->un_ch;
    if (!ch)
        return;

    ch->ch_tout = ch->ch_tin;
    /* do NOT do this here! */
    /* ch->ch_s_tpos = ch->ch_s_tin = 0; */

    /* send the flush output command now */
    ch->ch_send |= RR_TX_FLUSH;
    (ch->ch_nd)->nd_tx_ready = 1;
    (ch->ch_nd)->nd_tx_work = 1;
    wake_up_interruptible(&(ch->ch_nd)->nd_tx_waitq);

    if (waitqueue_active(&tty->write_wait))
        wake_up_interruptible(&tty->write_wait);

    tty_wakeup(tty);

}

/*
 *  Return space available in Tx buffer
 *  count = ( ch->ch_tout - ch->ch_tin ) mod (TBUF_MAX - 1)
 */
static int dgrp_tty_write_room(struct tty_struct *tty)
{
    struct un_struct *un;
    struct ch_struct *ch;
    int count;

    if (!tty)
        return 0;

    un = tty->driver_data;
    if (!un)
        return 0;

    ch = un->un_ch;
    if (!ch)
        return 0;

    count = (ch->ch_tout - ch->ch_tin - 1) & TBUF_MASK;

    /* We *MUST* check this, and return 0 if the Printer Unit cannot
     * take any more data within its time constraints...  If we don't
     * return 0 and the printer has hit it time constraint, the ld will
     * call us back doing a put_char, which cannot be rejected!!!
     */
    if (IS_PRINT(MINOR(tty_devnum(tty)))) {
        int un_flag = 0;
        count = dgrp_calculate_txprint_bounds(ch, count, &un_flag);
        if (count <= 0)
            count = 0;

        ch->ch_pun.un_flag |= un_flag;
        (ch->ch_nd)->nd_tx_work = 1;
    }

    return count;
}

/*
 *  Return number of characters that have not been transmitted yet.
 *  chars_in_buffer = ( ch->ch_tin - ch->ch_tout ) mod (TBUF_MAX - 1)
 *          + ( ch->ch_s_tin - ch->ch_s_tout ) mod (0xffff)
 *          = number of characters "in transit"
 *
 * Remember that sequence number math is always with a sixteen bit
 * mask, not the TBUF_MASK.
 */

static int dgrp_tty_chars_in_buffer(struct tty_struct *tty)
{
    struct un_struct *un;
    struct ch_struct *ch;
    int count;
    int count1;

    if (!tty)
        return 0;

    un = tty->driver_data;
    if (!un)
        return 0;

    ch = un->un_ch;
    if (!ch)
        return 0;

    count1 = count = (ch->ch_tin - ch->ch_tout) & TBUF_MASK;
    count += (ch->ch_s_tin - ch->ch_s_tpos) & 0xffff;
    /* one for tbuf, one for the PS */

    /*
     * If we are busy transmitting add 1
     */
    count += un->un_tbusy;

    return count;
}


/*****************************************************************************
 *
 * Helper applications for dgrp_tty_ioctl()
 *
 *****************************************************************************
 */


static tcflag_t ch_to_tty_flags(ushort ch_flag, char flagtype)
{
    tcflag_t retval = 0;

    switch (flagtype) {
    case 'i':
        retval = ((ch_flag & IF_IGNBRK) ? IGNBRK : 0)
             | ((ch_flag & IF_BRKINT) ? BRKINT : 0)
             | ((ch_flag & IF_IGNPAR) ? IGNPAR : 0)
             | ((ch_flag & IF_PARMRK) ? PARMRK : 0)
             | ((ch_flag & IF_INPCK) ? INPCK  : 0)
             | ((ch_flag & IF_ISTRIP) ? ISTRIP : 0)
             | ((ch_flag & IF_IXON) ? IXON   : 0)
             | ((ch_flag & IF_IXANY) ? IXANY  : 0)
             | ((ch_flag & IF_IXOFF) ? IXOFF  : 0);
        break;

    case 'o':
        retval = ((ch_flag & OF_OLCUC) ? OLCUC : 0)
             | ((ch_flag & OF_ONLCR) ? ONLCR  : 0)
             | ((ch_flag & OF_OCRNL) ? OCRNL  : 0)
             | ((ch_flag & OF_ONOCR) ? ONOCR  : 0)
             | ((ch_flag & OF_ONLRET) ? ONLRET : 0)
          /* | ((ch_flag & OF_OTAB3) ? OFILL  : 0) */
             | ((ch_flag & OF_TABDLY) ? TABDLY : 0);
        break;

    case 'c':
        retval = ((ch_flag & CF_CSTOPB) ? CSTOPB : 0)
             | ((ch_flag & CF_CREAD) ? CREAD  : 0)
             | ((ch_flag & CF_PARENB) ? PARENB : 0)
             | ((ch_flag & CF_PARODD) ? PARODD : 0)
             | ((ch_flag & CF_HUPCL) ? HUPCL  : 0);

        switch (ch_flag & CF_CSIZE) {
        case CF_CS5:
            retval |= CS5;
            break;
        case CF_CS6:
            retval |= CS6;
            break;
        case CF_CS7:
            retval |= CS7;
            break;
        case CF_CS8:
            retval |= CS8;
            break;
        default:
            retval |= CS8;
            break;
        }
        break;
    case 'x':
        break;
    case 'l':
        break;
    default:
        return 0;
    }

    return retval;
}


static ushort tty_to_ch_flags(struct tty_struct *tty, char flagtype)
{
    ushort retval = 0;
    tcflag_t tflag = 0;

    switch (flagtype) {
    case 'i':
        tflag  = tty->termios.c_iflag;
        retval = (I_IGNBRK(tty) ? IF_IGNBRK : 0)
              | (I_BRKINT(tty) ? IF_BRKINT : 0)
              | (I_IGNPAR(tty) ? IF_IGNPAR : 0)
              | (I_PARMRK(tty) ? IF_PARMRK : 0)
              | (I_INPCK(tty)  ? IF_INPCK  : 0)
              | (I_ISTRIP(tty) ? IF_ISTRIP : 0)
              | (I_IXON(tty)   ? IF_IXON   : 0)
              | (I_IXANY(tty)  ? IF_IXANY  : 0)
              | (I_IXOFF(tty)  ? IF_IXOFF  : 0);
        break;
    case 'o':
        tflag  = tty->termios.c_oflag;
        /*
         * If OPOST is set, then do the post processing in the
         * firmware by setting all the processing flags on.
         * If ~OPOST, then make sure we are not doing any
         * output processing!!
         */
        if (!O_OPOST(tty))
            retval = 0;
        else
            retval = (O_OLCUC(tty) ? OF_OLCUC : 0)
                 | (O_ONLCR(tty)  ? OF_ONLCR  : 0)
                 | (O_OCRNL(tty)  ? OF_OCRNL  : 0)
                 | (O_ONOCR(tty)  ? OF_ONOCR  : 0)
                 | (O_ONLRET(tty) ? OF_ONLRET : 0)
              /* | (O_OFILL(tty)  ? OF_TAB3   : 0) */
                 | (O_TABDLY(tty) ? OF_TABDLY : 0);
        break;
    case 'c':
        tflag  = tty->termios.c_cflag;
        retval = (C_CSTOPB(tty) ? CF_CSTOPB : 0)
             | (C_CREAD(tty)  ? CF_CREAD  : 0)
             | (C_PARENB(tty) ? CF_PARENB : 0)
             | (C_PARODD(tty) ? CF_PARODD : 0)
             | (C_HUPCL(tty)  ? CF_HUPCL  : 0);
        switch (C_CSIZE(tty)) {
        case CS8:
            retval |= CF_CS8;
            break;
        case CS7:
            retval |= CF_CS7;
            break;
        case CS6:
            retval |= CF_CS6;
            break;
        case CS5:
            retval |= CF_CS5;
            break;
        default:
            retval |= CF_CS8;
            break;
        }
        break;
    case 'x':
        break;
    case 'l':
        break;
    default:
        return 0;
    }

    return retval;
}


static int dgrp_tty_send_break(struct tty_struct *tty, int msec)
{
    struct un_struct *un;
    struct ch_struct *ch;
    int ret = -EIO;

    if (!tty)
        return ret;

    un = tty->driver_data;
    if (!un)
        return ret;

    ch = un->un_ch;
    if (!ch)
        return ret;

    dgrp_send_break(ch, msec);
    return 0;
}


/*
 * This routine sends a break character out the serial port.
 *
 * duration is in 1/1000's of a second
 */
static int dgrp_send_break(struct ch_struct *ch, int msec)
{
    ulong x;

    wait_event_interruptible(ch->ch_flag_wait,
        ((ch->ch_flag & CH_TX_BREAK) == 0));
    ch->ch_break_time += max(msec, 250);
    ch->ch_send |= RR_TX_BREAK;
    ch->ch_flag |= CH_TX_BREAK;
    (ch->ch_nd)->nd_tx_work = 1;

    x = (msec * HZ) / 1000;
    wake_up_interruptible(&(ch->ch_nd)->nd_tx_waitq);

    return 0;
}


/*
 * Return modem signals to ld.
 */
static int dgrp_tty_tiocmget(struct tty_struct *tty)
{
    unsigned int mlast;
    struct un_struct *un = tty->driver_data;
    struct ch_struct *ch;

    if (!un)
        return -ENODEV;

    ch = un->un_ch;
    if (!ch)
        return -ENODEV;

    mlast = ((ch->ch_s_mlast & ~(DM_RTS | DM_DTR)) |
        (ch->ch_mout & (DM_RTS | DM_DTR)));

    /* defined in /usr/include/asm/termios.h */
    mlast =   ((mlast & DM_RTS) ? TIOCM_RTS : 0)
        | ((mlast & DM_DTR) ? TIOCM_DTR : 0)
        | ((mlast & DM_CD)  ? TIOCM_CAR : 0)
        | ((mlast & DM_RI)  ? TIOCM_RNG : 0)
        | ((mlast & DM_DSR) ? TIOCM_DSR : 0)
        | ((mlast & DM_CTS) ? TIOCM_CTS : 0);

    return mlast;
}


/*
 *      Set modem lines
 */
static int dgrp_tty_tiocmset(struct tty_struct *tty,
                 unsigned int set, unsigned int clear)
{
    ulong lock_flags;
    struct un_struct *un = tty->driver_data;
    struct ch_struct *ch;

    if (!un)
        return -ENODEV;

    ch = un->un_ch;
    if (!ch)
        return -ENODEV;

    if (set & TIOCM_RTS)
        ch->ch_mout |= DM_RTS;

    if (set & TIOCM_DTR)
        ch->ch_mout |= DM_DTR;

    if (clear & TIOCM_RTS)
        ch->ch_mout &= ~(DM_RTS);

    if (clear & TIOCM_DTR)
        ch->ch_mout &= ~(DM_DTR);

    spin_lock_irqsave(&(ch->ch_nd)->nd_lock, lock_flags);
    ch->ch_flag |= CH_PARAM;
    (ch->ch_nd)->nd_tx_work = 1;
    wake_up_interruptible(&ch->ch_flag_wait);

    spin_unlock_irqrestore(&(ch->ch_nd)->nd_lock, lock_flags);

    return 0;
}



/*
 *      Get current modem status
 */
static int get_modem_info(struct ch_struct *ch, unsigned int *value)
{
    unsigned int mlast;

    mlast = ((ch->ch_s_mlast & ~(DM_RTS | DM_DTR)) |
        (ch->ch_mout    &  (DM_RTS | DM_DTR)));

    /* defined in /usr/include/asm/termios.h */
    mlast =   ((mlast & DM_RTS) ? TIOCM_RTS : 0)
        | ((mlast & DM_DTR) ? TIOCM_DTR : 0)
        | ((mlast & DM_CD)  ? TIOCM_CAR : 0)
        | ((mlast & DM_RI)  ? TIOCM_RNG : 0)
        | ((mlast & DM_DSR) ? TIOCM_DSR : 0)
        | ((mlast & DM_CTS) ? TIOCM_CTS : 0);
    put_user(mlast, (unsigned int __user *) value);

    return 0;
}

/*
 *      Set modem lines
 */
static int set_modem_info(struct ch_struct *ch, unsigned int command,
              unsigned int *value)
{
    int error;
    unsigned int arg;
    int mval = 0;
    ulong lock_flags;

    error = access_ok(VERIFY_READ, (void __user *) value, sizeof(int));
    if (error == 0)
        return -EFAULT;

    get_user(arg, (unsigned int __user *) value);
    mval |= ((arg & TIOCM_RTS) ? DM_RTS : 0)
        | ((arg & TIOCM_DTR) ? DM_DTR : 0);

    switch (command) {
    case TIOCMBIS:  /* set flags */
        ch->ch_mout |= mval;
        break;
    case TIOCMBIC:  /* clear flags */
        ch->ch_mout &= ~mval;
        break;
    case TIOCMSET:
        ch->ch_mout = mval;
        break;
    default:
        return -EINVAL;
    }

    spin_lock_irqsave(&(ch->ch_nd)->nd_lock, lock_flags);

    ch->ch_flag |= CH_PARAM;
    (ch->ch_nd)->nd_tx_work = 1;
    wake_up_interruptible(&ch->ch_flag_wait);

    spin_unlock_irqrestore(&(ch->ch_nd)->nd_lock, lock_flags);

    return 0;
}


/*
 *  Assign the custom baud rate to the channel structure
 */
static void dgrp_set_custom_speed(struct ch_struct *ch, int newrate)
{
    int testdiv;
    int testrate_high;
    int testrate_low;

    int deltahigh, deltalow;

    if (newrate < 0)
        newrate = 0;

    /*
     * Since the divisor is stored in a 16-bit integer, we make sure
     * we don't allow any rates smaller than a 16-bit integer would allow.
     * And of course, rates above the dividend won't fly.
     */
    if (newrate && newrate < ((PORTSERVER_DIVIDEND / 0xFFFF) + 1))
        newrate = ((PORTSERVER_DIVIDEND / 0xFFFF) + 1);
    if (newrate && newrate > PORTSERVER_DIVIDEND)
        newrate = PORTSERVER_DIVIDEND;

    while (newrate > 0) {
        testdiv = PORTSERVER_DIVIDEND / newrate;

        /*
         * If we try to figure out what rate the PortServer would use
         * with the test divisor, it will be either equal or higher
         * than the requested baud rate.  If we then determine the
         * rate with a divisor one higher, we will get the next lower
         * supported rate below the requested.
         */
        testrate_high = PORTSERVER_DIVIDEND / testdiv;
        testrate_low  = PORTSERVER_DIVIDEND / (testdiv + 1);

        /*
         * If the rate for the requested divisor is correct, just
         * use it and be done.
         */
        if (testrate_high == newrate)
            break;

        /*
         * Otherwise, pick the rate that is closer (i.e. whichever rate
         * has a smaller delta).
         */
        deltahigh = testrate_high - newrate;
        deltalow = newrate - testrate_low;

        if (deltahigh < deltalow)
            newrate = testrate_high;
        else
            newrate = testrate_low;

        break;
    }

    ch->ch_custom_speed = newrate;

    drp_param(ch);

    return;
}


/*
 # dgrp_tty_digiseta()
 *
 * Ioctl to set the information from ditty.
 *
 * NOTE: DIGI_IXON, DSRPACE, DCDPACE, and DTRPACE are unsupported.  JAR 990922
 */
static int dgrp_tty_digiseta(struct tty_struct *tty,
                 struct digi_struct *new_info)
{
    struct un_struct *un = tty->driver_data;
    struct ch_struct *ch;

    if (!un)
        return -ENODEV;

    ch = un->un_ch;
    if (!ch)
        return -ENODEV;

    if (copy_from_user(&ch->ch_digi, (void __user *) new_info,
               sizeof(struct digi_struct)))
        return -EFAULT;

    if ((ch->ch_digi.digi_flags & RTSPACE) ||
        (ch->ch_digi.digi_flags & CTSPACE))
        tty->termios.c_cflag |= CRTSCTS;
    else
        tty->termios.c_cflag &= ~CRTSCTS;

    if (ch->ch_digi.digi_maxcps < 1)
        ch->ch_digi.digi_maxcps = 1;

    if (ch->ch_digi.digi_maxcps > 10000)
        ch->ch_digi.digi_maxcps = 10000;

    if (ch->ch_digi.digi_bufsize < 10)
        ch->ch_digi.digi_bufsize = 10;

    if (ch->ch_digi.digi_maxchar < 1)
        ch->ch_digi.digi_maxchar = 1;

    if (ch->ch_digi.digi_maxchar > ch->ch_digi.digi_bufsize)
        ch->ch_digi.digi_maxchar = ch->ch_digi.digi_bufsize;

    if (ch->ch_digi.digi_onlen > DIGI_PLEN)
        ch->ch_digi.digi_onlen = DIGI_PLEN;

    if (ch->ch_digi.digi_offlen > DIGI_PLEN)
        ch->ch_digi.digi_offlen = DIGI_PLEN;

    /* make the changes now */
    drp_param(ch);

    return 0;
}



/*
 * dgrp_tty_digigetedelay()
 *
 * Ioctl to get the current edelay setting.
 *
 *
 *
 */
static int dgrp_tty_digigetedelay(struct tty_struct *tty, int *retinfo)
{
    struct un_struct *un;
    struct ch_struct *ch;
    int tmp;

    if (!retinfo)
        return -EFAULT;

    if (!tty || tty->magic != TTY_MAGIC)
        return -EFAULT;

    un = tty->driver_data;

    if (!un)
        return -ENODEV;

    ch = un->un_ch;
    if (!ch)
        return -ENODEV;

    tmp = ch->ch_edelay;

    if (copy_to_user((void __user *) retinfo, &tmp, sizeof(*retinfo)))
        return -EFAULT;

    return 0;
}


/*
 * dgrp_tty_digisetedelay()
 *
 * Ioctl to set the EDELAY setting
 *
 */
static int dgrp_tty_digisetedelay(struct tty_struct *tty, int *new_info)
{
    struct un_struct *un;
    struct ch_struct *ch;
    int new_digi;

    if (!tty || tty->magic != TTY_MAGIC)
        return -EFAULT;

    un = tty->driver_data;

    if (!un)
        return -ENODEV;

    ch = un->un_ch;
    if (!ch)
        return -ENODEV;

    if (copy_from_user(&new_digi, (void __user *)new_info, sizeof(int)))
        return -EFAULT;

    ch->ch_edelay = new_digi;

    /* make the changes now */
    drp_param(ch);

    return 0;
}


/*
 *  The usual assortment of ioctl's
 *
 *  note:  use tty_check_change to make sure that we are not
 *  changing the state of a terminal when we are not a process
 *  in the forground.  See tty_io.c
 *      rc = tty_check_change(tty);
 *      if (rc) return rc;
 */
static int dgrp_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
              unsigned long arg)
{
    struct un_struct *un;
    struct ch_struct *ch;
    int rc;
    struct digiflow_struct   dflow;

    if (!tty)
        return -ENODEV;

    un = tty->driver_data;
    if (!un)
        return -ENODEV;

    ch = un->un_ch;
    if (!ch)
        return -ENODEV;

    switch (cmd) {

    /*
     * Here are all the standard ioctl's that we MUST implement
     */

    case TCSBRK:
        /*
         * TCSBRK is SVID version: non-zero arg --> no break
         * this behaviour is exploited by tcdrain().
         *
         * According to POSIX.1 spec (7.2.2.1.2) breaks should be
         * between 0.25 and 0.5 seconds
         */

        rc = tty_check_change(tty);
        if (rc)
            return rc;
        tty_wait_until_sent(tty, 0);

        if (!arg)
            rc = dgrp_send_break(ch, 250); /* 1/4 second */

        if (dgrp_tty_chars_in_buffer(tty) != 0)
            return -EINTR;

        return 0;

    case TCSBRKP:
        /* support for POSIX tcsendbreak()
         *
         * According to POSIX.1 spec (7.2.2.1.2) breaks should be
         * between 0.25 and 0.5 seconds so we'll ask for something
         * in the middle: 0.375 seconds.
         */
        rc = tty_check_change(tty);
        if (rc)
            return rc;
        tty_wait_until_sent(tty, 0);

        rc = dgrp_send_break(ch, arg ? arg*250 : 250);

        if (dgrp_tty_chars_in_buffer(tty) != 0)
            return -EINTR;
        return 0;

    case TIOCSBRK:
        rc = tty_check_change(tty);
        if (rc)
            return rc;
        tty_wait_until_sent(tty, 0);

        /*
         * RealPort doesn't support turning on a break unconditionally.
         * The RealPort device will stop sending a break automatically
         * after the specified time value that we send in.
         */
        rc = dgrp_send_break(ch, 250); /* 1/4 second */

        if (dgrp_tty_chars_in_buffer(tty) != 0)
            return -EINTR;
        return 0;

    case TIOCCBRK:
        /*
         * RealPort doesn't support turning off a break unconditionally.
         * The RealPort device will stop sending a break automatically
         * after the specified time value that was sent when turning on
         * the break.
         */
        return 0;

    case TIOCGSOFTCAR:
        rc = access_ok(VERIFY_WRITE, (void __user *) arg,
                   sizeof(long));
        if (rc == 0)
            return -EFAULT;
        put_user(C_CLOCAL(tty) ? 1 : 0, (unsigned long __user *) arg);
        return 0;

    case TIOCSSOFTCAR:
        get_user(arg, (unsigned long __user *) arg);
        tty->termios.c_cflag =
            ((tty->termios.c_cflag & ~CLOCAL) |
             (arg ? CLOCAL : 0));
        return 0;

    case TIOCMGET:
        rc = access_ok(VERIFY_WRITE, (void __user *) arg,
                 sizeof(unsigned int));
        if (rc == 0)
            return -EFAULT;
        return get_modem_info(ch, (unsigned int *) arg);

    case TIOCMBIS:
    case TIOCMBIC:
    case TIOCMSET:
        return set_modem_info(ch, cmd, (unsigned int *) arg);

    /*
     * Here are any additional ioctl's that we want to implement
     */

    case TCFLSH:
        /*
         * The linux tty driver doesn't have a flush
         * input routine for the driver, assuming all backed
         * up data is in the line disc. buffers.  However,
         * we all know that's not the case.  Here, we
         * act on the ioctl, but then lie and say we didn't
         * so the line discipline will process the flush
         * also.
         */
        rc = tty_check_change(tty);
        if (rc)
            return rc;

        switch (arg) {
        case TCIFLUSH:
        case TCIOFLUSH:
            /* only flush input if this is the only open unit */
            if (!IS_PRINT(MINOR(tty_devnum(tty)))) {
                ch->ch_rout = ch->ch_rin;
                ch->ch_send |= RR_RX_FLUSH;
                (ch->ch_nd)->nd_tx_work = 1;
                (ch->ch_nd)->nd_tx_ready = 1;
                wake_up_interruptible(&(ch->ch_nd)->nd_tx_waitq);
            }
            if (arg == TCIFLUSH)
                break;

        case TCOFLUSH: /* flush output, or the receive buffer */
            /*
             * This is handled in the tty_ioctl.c code
             * calling tty_flush_buffer
             */
            break;

        default:
            /* POSIX.1 says return EINVAL if we got a bad arg */
            return -EINVAL;
        }
        /* pretend we didn't recognize this IOCTL */
        return -ENOIOCTLCMD;

#ifdef TIOCGETP
    case TIOCGETP:
#endif
    /*****************************************
    Linux       HPUX        Function
    TCSETA      TCSETA      - set the termios
    TCSETAF     TCSETAF     - wait for drain first, then set termios
    TCSETAW     TCSETAW     - wait for drain, flush the input queue, then set termios
    - looking at the tty_ioctl code, these command all call our
    tty_set_termios at the driver's end, when a TCSETA* is sent,
    it is expecting the tty to have a termio structure,
    NOT a termios stucture.  These two structures differ in size
    and the tty_ioctl code does a conversion before processing them both.
    - we should treat the TCSETAW TCSETAF ioctls the same, and let
    the tty_ioctl code do the conversion stuff.

    TCSETS
    TCSETSF     (none)
    TCSETSW
    - the associated tty structure has a termios structure.
    *****************************************/

    case TCGETS:
    case TCGETA:
        return -ENOIOCTLCMD;

    case TCSETAW:
    case TCSETAF:
    case TCSETSF:
    case TCSETSW:
        /*
         * The linux tty driver doesn't have a flush
         * input routine for the driver, assuming all backed
         * up data is in the line disc. buffers.  However,
         * we all know that's not the case.  Here, we
         * act on the ioctl, but then lie and say we didn't
         * so the line discipline will process the flush
         * also.
         */

        /*
         * Also, now that we have TXPrint, we have to check
         * if this is the TXPrint device and the terminal
         * device is open. If so, do NOT run check_change,
         * as the terminal device is ALWAYS the parent.
         */
        if (!IS_PRINT(MINOR(tty_devnum(tty))) ||
            !ch->ch_tun.un_open_count) {
            rc = tty_check_change(tty);
            if (rc)
                return rc;
        }

        /* wait for all the characters in tbuf to drain */
        tty_wait_until_sent(tty, 0);

        if ((cmd == TCSETSF) || (cmd == TCSETAF)) {
            /* flush the contents of the rbuf queue */
            /* TODO:  check if this is print device? */
            ch->ch_send |= RR_RX_FLUSH;
            (ch->ch_nd)->nd_tx_ready = 1;
            (ch->ch_nd)->nd_tx_work = 1;
            wake_up_interruptible(&(ch->ch_nd)->nd_tx_waitq);
            /* do we need to do this?  just to be safe! */
            ch->ch_rout = ch->ch_rin;
        }

        /* pretend we didn't recognize this */
        return -ENOIOCTLCMD;

    case TCXONC:
        /*
         * The Linux Line Discipline (LD) would do this for us if we
         * let it, but we have the special firmware options to do this
         * the "right way" regardless of hardware or software flow
         * control so we'll do it outselves instead of letting the LD
         * do it.
         */
        rc = tty_check_change(tty);
        if (rc)
            return rc;

        switch (arg) {
        case TCOON:
            dgrp_tty_start(tty);
            return 0;
        case TCOOFF:
            dgrp_tty_stop(tty);
            return 0;
        case TCION:
            dgrp_tty_input_start(tty);
            return 0;
        case TCIOFF:
            dgrp_tty_input_stop(tty);
            return 0;
        default:
            return -EINVAL;
        }

    case DIGI_GETA:
        /* get information for ditty */
        if (copy_to_user((struct digi_struct __user *) arg,
                 &ch->ch_digi, sizeof(struct digi_struct)))
            return -EFAULT;
        break;

    case DIGI_SETAW:
    case DIGI_SETAF:
        /* wait for all the characters in tbuf to drain */
        tty_wait_until_sent(tty, 0);

        if (cmd == DIGI_SETAF) {
            /* flush the contents of the rbuf queue */
            /* send down a packet with RR_RX_FLUSH set */
            ch->ch_send |= RR_RX_FLUSH;
            (ch->ch_nd)->nd_tx_ready = 1;
            (ch->ch_nd)->nd_tx_work = 1;
            wake_up_interruptible(&(ch->ch_nd)->nd_tx_waitq);
            /* do we need to do this?  just to be safe! */
            ch->ch_rout = ch->ch_rin;
        }

        /* pretend we didn't recognize this */

    case DIGI_SETA:
        return dgrp_tty_digiseta(tty, (struct digi_struct *) arg);

    case DIGI_SEDELAY:
        return dgrp_tty_digisetedelay(tty, (int *) arg);

    case DIGI_GEDELAY:
        return dgrp_tty_digigetedelay(tty, (int *) arg);

    case DIGI_GETFLOW:
    case DIGI_GETAFLOW:
        if (cmd == (DIGI_GETFLOW)) {
            dflow.startc = tty->termios.c_cc[VSTART];
            dflow.stopc = tty->termios.c_cc[VSTOP];
        } else {
            dflow.startc = ch->ch_xxon;
            dflow.stopc = ch->ch_xxoff;
        }

        if (copy_to_user((char __user *)arg, &dflow, sizeof(dflow)))
            return -EFAULT;
        break;

    case DIGI_SETFLOW:
    case DIGI_SETAFLOW:

        if (copy_from_user(&dflow, (char __user *)arg, sizeof(dflow)))
            return -EFAULT;

        if (cmd == (DIGI_SETFLOW)) {
            tty->termios.c_cc[VSTART] = dflow.startc;
            tty->termios.c_cc[VSTOP] = dflow.stopc;
        } else {
            ch->ch_xxon = dflow.startc;
            ch->ch_xxoff = dflow.stopc;
        }
        break;

    case DIGI_GETCUSTOMBAUD:
        rc = access_ok(VERIFY_WRITE, (void __user *) arg, sizeof(int));
        if (rc == 0)
            return -EFAULT;
        put_user(ch->ch_custom_speed, (unsigned int __user *) arg);
        break;

    case DIGI_SETCUSTOMBAUD:
    {
        int new_rate;

        get_user(new_rate, (unsigned int __user *) arg);
        dgrp_set_custom_speed(ch, new_rate);

        break;
    }

    default:
        return -ENOIOCTLCMD;
    }

    return 0;
}

/*
 *  This routine allows the tty driver to be notified when
 *  the device's termios setting have changed.  Note that we
 *  should be prepared to accept the case where old == NULL
 *  and try to do something rational.
 *
 *  So we need to make sure that our copies of ch_oflag,
 *  ch_clag, and ch_iflag reflect the tty->termios flags.
 */
static void dgrp_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
{
    struct ktermios *ts;
    struct ch_struct *ch;
    struct un_struct *un;

    /* seems silly, but we have to check all these! */
    if (!tty)
        return;

    un = tty->driver_data;
    if (!un)
        return;

    ts = &tty->termios;

    ch = un->un_ch;
    if (!ch)
        return;

    drp_param(ch);

    /* the CLOCAL flag has just been set */
    if (!(old->c_cflag & CLOCAL) && C_CLOCAL(tty))
        wake_up_interruptible(&un->un_open_wait);
}


/*
 *  Throttle receiving data.  We just set a bit and stop reading
 *  data out of the channel buffer.  It will back up and the
 *  FEP will do whatever is necessary to stop the far end.
 */
static void dgrp_tty_throttle(struct tty_struct *tty)
{
    struct ch_struct *ch;

    if (!tty)
        return;

    ch = ((struct un_struct *) tty->driver_data)->un_ch;
    if (!ch)
        return;

    ch->ch_flag |= CH_RXSTOP;
}


static void dgrp_tty_unthrottle(struct tty_struct *tty)
{
    struct ch_struct *ch;

    if (!tty)
        return;

    ch = ((struct un_struct *) tty->driver_data)->un_ch;
    if (!ch)
        return;

    ch->ch_flag &= ~CH_RXSTOP;
}

/*
 *  Stop the transmitter
 */
static void dgrp_tty_stop(struct tty_struct *tty)
{
    struct ch_struct *ch;

    if (!tty)
        return;

    ch = ((struct un_struct *) tty->driver_data)->un_ch;
    if (!ch)
        return;

    ch->ch_send |= RR_TX_STOP;
    ch->ch_send &= ~RR_TX_START;

    /* make the change NOW! */
    (ch->ch_nd)->nd_tx_ready = 1;
    if (waitqueue_active(&(ch->ch_nd)->nd_tx_waitq))
        wake_up_interruptible(&(ch->ch_nd)->nd_tx_waitq);
}

/*
 *  Start the transmitter
 */
static void dgrp_tty_start(struct tty_struct *tty)
{
    struct ch_struct *ch;

    if (!tty)
        return;

    ch = ((struct un_struct *) tty->driver_data)->un_ch;
    if (!ch)
        return;

    /* TODO: don't do anything if the transmitter is not stopped */

    ch->ch_send |= RR_TX_START;
    ch->ch_send &= ~RR_TX_STOP;

    /* make the change NOW! */
    (ch->ch_nd)->nd_tx_ready = 1;
    (ch->ch_nd)->nd_tx_work = 1;
    if (waitqueue_active(&(ch->ch_nd)->nd_tx_waitq))
        wake_up_interruptible(&(ch->ch_nd)->nd_tx_waitq);

}

/*
 *  Stop the reciever
 */
static void dgrp_tty_input_stop(struct tty_struct *tty)
{
    struct ch_struct *ch;

    if (!tty)
        return;

    ch = ((struct un_struct *) tty->driver_data)->un_ch;
    if (!ch)
        return;

    ch->ch_send |= RR_RX_STOP;
    ch->ch_send &= ~RR_RX_START;
    (ch->ch_nd)->nd_tx_ready = 1;
    if (waitqueue_active(&(ch->ch_nd)->nd_tx_waitq))
        wake_up_interruptible(&(ch->ch_nd)->nd_tx_waitq);

}


static void dgrp_tty_send_xchar(struct tty_struct *tty, char c)
{
    struct un_struct *un;
    struct ch_struct *ch;

    if (!tty)
        return;

    un = tty->driver_data;
    if (!un)
        return;

    ch = un->un_ch;
    if (!ch)
        return;
    if (c == STOP_CHAR(tty))
        ch->ch_send |= RR_RX_STOP;
    else if (c == START_CHAR(tty))
        ch->ch_send |= RR_RX_START;

    ch->ch_nd->nd_tx_ready = 1;
    ch->ch_nd->nd_tx_work = 1;

    return;
}


static void dgrp_tty_input_start(struct tty_struct *tty)
{
    struct ch_struct *ch;

    if (!tty)
        return;

    ch = ((struct un_struct *) tty->driver_data)->un_ch;
    if (!ch)
        return;

    ch->ch_send |= RR_RX_START;
    ch->ch_send &= ~RR_RX_STOP;
    (ch->ch_nd)->nd_tx_ready = 1;
    (ch->ch_nd)->nd_tx_work = 1;
    if (waitqueue_active(&(ch->ch_nd)->nd_tx_waitq))
        wake_up_interruptible(&(ch->ch_nd)->nd_tx_waitq);

}


/*
 *  Hangup the port.  Like a close, but don't wait for output
 *  to drain.
 *
 *  How do we close all the channels that are open?
 */
static void dgrp_tty_hangup(struct tty_struct *tty)
{
    struct ch_struct *ch;
    struct nd_struct *nd;
    struct un_struct *un;

    if (!tty)
        return;

    un = tty->driver_data;
    if (!un)
        return;

    ch = un->un_ch;
    if (!ch)
        return;

    nd = ch->ch_nd;

    if (C_HUPCL(tty)) {
        /* LOWER DTR */
        ch->ch_mout &= ~DM_DTR;
        /* Don't do this here */
        /* ch->ch_flag |= CH_HANGUP; */
        ch->ch_nd->nd_tx_ready = 1;
        ch->ch_nd->nd_tx_work  = 1;
        if (waitqueue_active(&ch->ch_flag_wait))
            wake_up_interruptible(&ch->ch_flag_wait);
    }

}

/************************************************************************/
/*                                                                      */
/*       TTY Initialization/Cleanup Functions                           */
/*                                                                      */
/************************************************************************/

/*
 *  Uninitialize the TTY portion of the supplied node.  Free all
 *      memory and resources associated with this node.  Do it in reverse
 *      allocation order: this might possibly result in less fragmentation
 *      of memory, though I don't know this for sure.
 */
void
dgrp_tty_uninit(struct nd_struct *nd)
{
    char id[3];

    ID_TO_CHAR(nd->nd_ID, id);

    if (nd->nd_ttdriver_flags & SERIAL_TTDRV_REG) {
        tty_unregister_driver(nd->nd_serial_ttdriver);

        kfree(nd->nd_serial_ttdriver->ttys);
        nd->nd_serial_ttdriver->ttys = NULL;

        put_tty_driver(nd->nd_serial_ttdriver);
        nd->nd_ttdriver_flags &= ~SERIAL_TTDRV_REG;
    }

    if (nd->nd_ttdriver_flags & CALLOUT_TTDRV_REG) {
        tty_unregister_driver(nd->nd_callout_ttdriver);

        kfree(nd->nd_callout_ttdriver->ttys);
        nd->nd_callout_ttdriver->ttys = NULL;

        put_tty_driver(nd->nd_callout_ttdriver);
        nd->nd_ttdriver_flags &= ~CALLOUT_TTDRV_REG;
    }

    if (nd->nd_ttdriver_flags & XPRINT_TTDRV_REG) {
        tty_unregister_driver(nd->nd_xprint_ttdriver);

        kfree(nd->nd_xprint_ttdriver->ttys);
        nd->nd_xprint_ttdriver->ttys = NULL;

        put_tty_driver(nd->nd_xprint_ttdriver);
        nd->nd_ttdriver_flags &= ~XPRINT_TTDRV_REG;
    }
}



/*
 *     Initialize the TTY portion of the supplied node.
 */
int
dgrp_tty_init(struct nd_struct *nd)
{
    char id[3];
    int  rc;
    int  i;

    ID_TO_CHAR(nd->nd_ID, id);

    /*
     *  Initialize the TTDRIVER structures.
     */

    nd->nd_serial_ttdriver = alloc_tty_driver(CHAN_MAX);
    if (!nd->nd_serial_ttdriver)
        return -ENOMEM;

    sprintf(nd->nd_serial_name,  "tty_dgrp_%s_", id);

    nd->nd_serial_ttdriver->owner = THIS_MODULE;
    nd->nd_serial_ttdriver->name = nd->nd_serial_name;
    nd->nd_serial_ttdriver->name_base = 0;
    nd->nd_serial_ttdriver->major = 0;
    nd->nd_serial_ttdriver->minor_start = 0;
    nd->nd_serial_ttdriver->type = TTY_DRIVER_TYPE_SERIAL;
    nd->nd_serial_ttdriver->subtype = SERIAL_TYPE_NORMAL;
    nd->nd_serial_ttdriver->init_termios = DefaultTermios;
    nd->nd_serial_ttdriver->driver_name = "dgrp";
    nd->nd_serial_ttdriver->flags = (TTY_DRIVER_REAL_RAW |
                     TTY_DRIVER_DYNAMIC_DEV |
                     TTY_DRIVER_HARDWARE_BREAK);

    /* The kernel wants space to store pointers to tty_structs. */
    nd->nd_serial_ttdriver->ttys =
        kzalloc(CHAN_MAX * sizeof(struct tty_struct *), GFP_KERNEL);
    if (!nd->nd_serial_ttdriver->ttys)
        return -ENOMEM;

    tty_set_operations(nd->nd_serial_ttdriver, &dgrp_tty_ops);

    if (!(nd->nd_ttdriver_flags & SERIAL_TTDRV_REG)) {
        /*
         *   Register tty devices
         */
        rc = tty_register_driver(nd->nd_serial_ttdriver);
        if (rc < 0) {
            /*
             * If errno is EBUSY, this means there are no more
             * slots available to have us auto-majored.
             * (Which is currently supported up to 256)
             *
             * We can still request majors above 256,
             * we just have to do it manually.
             */
            if (rc == -EBUSY) {
                int i;
                int max_majors = 1U << (32 - MINORBITS);
                for (i = 256; i < max_majors; i++) {
                    nd->nd_serial_ttdriver->major = i;
                    rc = tty_register_driver(nd->nd_serial_ttdriver);
                    if (rc >= 0)
                        break;
                }
                /* Really fail now, since we ran out
                 * of majors to try. */
                if (i == max_majors)
                    return rc;

            } else {
                return rc;
            }
        }
        nd->nd_ttdriver_flags |= SERIAL_TTDRV_REG;
    }

    nd->nd_callout_ttdriver = alloc_tty_driver(CHAN_MAX);
    if (!nd->nd_callout_ttdriver)
        return -ENOMEM;

    sprintf(nd->nd_callout_name, "cu_dgrp_%s_",  id);

    nd->nd_callout_ttdriver->owner = THIS_MODULE;
    nd->nd_callout_ttdriver->name = nd->nd_callout_name;
    nd->nd_callout_ttdriver->name_base = 0;
    nd->nd_callout_ttdriver->major = nd->nd_serial_ttdriver->major;
    nd->nd_callout_ttdriver->minor_start = 0x40;
    nd->nd_callout_ttdriver->type = TTY_DRIVER_TYPE_SERIAL;
    nd->nd_callout_ttdriver->subtype = SERIAL_TYPE_CALLOUT;
    nd->nd_callout_ttdriver->init_termios = DefaultTermios;
    nd->nd_callout_ttdriver->driver_name = "dgrp";
    nd->nd_callout_ttdriver->flags = (TTY_DRIVER_REAL_RAW |
                      TTY_DRIVER_DYNAMIC_DEV |
                      TTY_DRIVER_HARDWARE_BREAK);

    /* The kernel wants space to store pointers to tty_structs. */
    nd->nd_callout_ttdriver->ttys =
        kzalloc(CHAN_MAX * sizeof(struct tty_struct *), GFP_KERNEL);
    if (!nd->nd_callout_ttdriver->ttys)
        return -ENOMEM;

    tty_set_operations(nd->nd_callout_ttdriver, &dgrp_tty_ops);

    if (dgrp_register_cudevices) {
        if (!(nd->nd_ttdriver_flags & CALLOUT_TTDRV_REG)) {
            /*
             *   Register cu devices
             */
            rc = tty_register_driver(nd->nd_callout_ttdriver);
            if (rc < 0)
                return rc;
            nd->nd_ttdriver_flags |= CALLOUT_TTDRV_REG;
        }
    }


    nd->nd_xprint_ttdriver = alloc_tty_driver(CHAN_MAX);
    if (!nd->nd_xprint_ttdriver)
        return -ENOMEM;

    sprintf(nd->nd_xprint_name,  "pr_dgrp_%s_", id);

    nd->nd_xprint_ttdriver->owner = THIS_MODULE;
    nd->nd_xprint_ttdriver->name = nd->nd_xprint_name;
    nd->nd_xprint_ttdriver->name_base = 0;
    nd->nd_xprint_ttdriver->major = nd->nd_serial_ttdriver->major;
    nd->nd_xprint_ttdriver->minor_start = 0x80;
    nd->nd_xprint_ttdriver->type = TTY_DRIVER_TYPE_SERIAL;
    nd->nd_xprint_ttdriver->subtype = SERIAL_TYPE_XPRINT;
    nd->nd_xprint_ttdriver->init_termios = DefaultTermios;
    nd->nd_xprint_ttdriver->driver_name = "dgrp";
    nd->nd_xprint_ttdriver->flags = (TTY_DRIVER_REAL_RAW |
                     TTY_DRIVER_DYNAMIC_DEV |
                     TTY_DRIVER_HARDWARE_BREAK);

    /* The kernel wants space to store pointers to tty_structs. */
    nd->nd_xprint_ttdriver->ttys =
        kzalloc(CHAN_MAX * sizeof(struct tty_struct *), GFP_KERNEL);
    if (!nd->nd_xprint_ttdriver->ttys)
        return -ENOMEM;

    tty_set_operations(nd->nd_xprint_ttdriver, &dgrp_tty_ops);

    if (dgrp_register_prdevices) {
        if (!(nd->nd_ttdriver_flags & XPRINT_TTDRV_REG)) {
            /*
             *   Register transparent print devices
             */
            rc = tty_register_driver(nd->nd_xprint_ttdriver);
            if (rc < 0)
                return rc;
            nd->nd_ttdriver_flags |= XPRINT_TTDRV_REG;
        }
    }

    for (i = 0; i < CHAN_MAX; i++) {
        struct ch_struct *ch = nd->nd_chan + i;

        ch->ch_nd = nd;
        ch->ch_digi = digi_init;
        ch->ch_edelay = 100;
        ch->ch_custom_speed = 0;
        ch->ch_portnum = i;
        ch->ch_tun.un_ch = ch;
        ch->ch_pun.un_ch = ch;
        ch->ch_tun.un_type = SERIAL_TYPE_NORMAL;
        ch->ch_pun.un_type = SERIAL_TYPE_XPRINT;

        init_waitqueue_head(&(ch->ch_flag_wait));
        init_waitqueue_head(&(ch->ch_sleep));

        init_waitqueue_head(&(ch->ch_tun.un_open_wait));
        init_waitqueue_head(&(ch->ch_tun.un_close_wait));

        init_waitqueue_head(&(ch->ch_pun.un_open_wait));
        init_waitqueue_head(&(ch->ch_pun.un_close_wait));
        tty_port_init(&ch->port);
        tty_port_init(&ch->port);
    }
    return 0;
}