/*
 * Copyright 2003 Digi International (www.digi.com)
 *      Scott H Kilau <Scott_Kilau 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.
 */

/************************************************************************
 *
 * This file implements the tty driver functionality for the
 * Neo and ClassicBoard PCI based product lines.
 *
 ************************************************************************
 *
 */

#include <linux/kernel.h>
#include <linux/sched.h>        /* For jiffies, task states */
#include <linux/interrupt.h>    /* For tasklet and interrupt structs/defines */
#include <linux/module.h>
#include <linux/ctype.h>
#include <linux/tty.h>
#include <linux/tty_flip.h>
#include <linux/types.h>
#include <linux/serial_reg.h>
#include <linux/slab.h>
#include <linux/delay.h>        /* For udelay */
#include <linux/uaccess.h>      /* For copy_from_user/copy_to_user */
#include <linux/pci.h>
#include "dgnc_driver.h"
#include "dgnc_tty.h"
#include "dgnc_neo.h"
#include "dgnc_cls.h"
#include "dgnc_sysfs.h"
#include "dgnc_utils.h"

#define init_MUTEX(sem)  sema_init(sem, 1)
#define DECLARE_MUTEX(name)     \
        struct semaphore name = __SEMAPHORE_INITIALIZER(name, 1)

/*
 * internal variables
 */
static struct dgnc_board        *dgnc_BoardsByMajor[256];
static unsigned char            *dgnc_TmpWriteBuf;
static DECLARE_MUTEX(dgnc_TmpWriteSem);

/*
 * Default transparent print information.
 */
static struct digi_t dgnc_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 DgncDefaultTermios = {
        .c_iflag =      (DEFAULT_IFLAGS),       /* iflags */
        .c_oflag =      (DEFAULT_OFLAGS),       /* oflags */
        .c_cflag =      (DEFAULT_CFLAGS),       /* cflags */
        .c_lflag =      (DEFAULT_LFLAGS),       /* lflags */
        .c_cc =         INIT_C_CC,
        .c_line =       0,
};


/* Our function prototypes */
static int dgnc_tty_open(struct tty_struct *tty, struct file *file);
static void dgnc_tty_close(struct tty_struct *tty, struct file *file);
static int dgnc_block_til_ready(struct tty_struct *tty, struct file *file, struct channel_t *ch);
static int dgnc_tty_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg);
static int dgnc_tty_digigeta(struct tty_struct *tty, struct digi_t __user *retinfo);
static int dgnc_tty_digiseta(struct tty_struct *tty, struct digi_t __user *new_info);
static int dgnc_tty_write_room(struct tty_struct *tty);
static int dgnc_tty_put_char(struct tty_struct *tty, unsigned char c);
static int dgnc_tty_chars_in_buffer(struct tty_struct *tty);
static void dgnc_tty_start(struct tty_struct *tty);
static void dgnc_tty_stop(struct tty_struct *tty);
static void dgnc_tty_throttle(struct tty_struct *tty);
static void dgnc_tty_unthrottle(struct tty_struct *tty);
static void dgnc_tty_flush_chars(struct tty_struct *tty);
static void dgnc_tty_flush_buffer(struct tty_struct *tty);
static void dgnc_tty_hangup(struct tty_struct *tty);
static int dgnc_set_modem_info(struct tty_struct *tty, unsigned int command, unsigned int __user *value);
static int dgnc_get_modem_info(struct channel_t *ch, unsigned int __user *value);
static int dgnc_tty_tiocmget(struct tty_struct *tty);
static int dgnc_tty_tiocmset(struct tty_struct *tty, unsigned int set, unsigned int clear);
static int dgnc_tty_send_break(struct tty_struct *tty, int msec);
static void dgnc_tty_wait_until_sent(struct tty_struct *tty, int timeout);
static int dgnc_tty_write(struct tty_struct *tty, const unsigned char *buf, int count);
static void dgnc_tty_set_termios(struct tty_struct *tty, struct ktermios *old_termios);
static void dgnc_tty_send_xchar(struct tty_struct *tty, char ch);


static const struct tty_operations dgnc_tty_ops = {
        .open = dgnc_tty_open,
        .close = dgnc_tty_close,
        .write = dgnc_tty_write,
        .write_room = dgnc_tty_write_room,
        .flush_buffer = dgnc_tty_flush_buffer,
        .chars_in_buffer = dgnc_tty_chars_in_buffer,
        .flush_chars = dgnc_tty_flush_chars,
        .ioctl = dgnc_tty_ioctl,
        .set_termios = dgnc_tty_set_termios,
        .stop = dgnc_tty_stop,
        .start = dgnc_tty_start,
        .throttle = dgnc_tty_throttle,
        .unthrottle = dgnc_tty_unthrottle,
        .hangup = dgnc_tty_hangup,
        .put_char = dgnc_tty_put_char,
        .tiocmget = dgnc_tty_tiocmget,
        .tiocmset = dgnc_tty_tiocmset,
        .break_ctl = dgnc_tty_send_break,
        .wait_until_sent = dgnc_tty_wait_until_sent,
        .send_xchar = dgnc_tty_send_xchar
};

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

/*
 * dgnc_tty_preinit()
 *
 * Initialize any global tty related data before we download any boards.
 */
int dgnc_tty_preinit(void)
{
        /*
         * Allocate a buffer for doing the copy from user space to
         * kernel space in dgnc_write().  We only use one buffer and
         * control access to it with a semaphore.  If we are paging, we
         * are already in trouble so one buffer won't hurt much anyway.
         *
         * We are okay to sleep in the malloc, as this routine
         * is only called during module load, (not in interrupt context),
         * and with no locks held.
         */
        dgnc_TmpWriteBuf = kmalloc(WRITEBUFLEN, GFP_KERNEL);

        if (!dgnc_TmpWriteBuf)
                return -ENOMEM;

        return 0;
}


/*
 * dgnc_tty_register()
 *
 * Init the tty subsystem for this board.
 */
int dgnc_tty_register(struct dgnc_board *brd)
{
        int rc = 0;

        brd->SerialDriver.magic = TTY_DRIVER_MAGIC;

        snprintf(brd->SerialName, MAXTTYNAMELEN, "tty_dgnc_%d_", brd->boardnum);

        brd->SerialDriver.name = brd->SerialName;
        brd->SerialDriver.name_base = 0;
        brd->SerialDriver.major = 0;
        brd->SerialDriver.minor_start = 0;
        brd->SerialDriver.num = brd->maxports;
        brd->SerialDriver.type = TTY_DRIVER_TYPE_SERIAL;
        brd->SerialDriver.subtype = SERIAL_TYPE_NORMAL;
        brd->SerialDriver.init_termios = DgncDefaultTermios;
        brd->SerialDriver.driver_name = DRVSTR;
        brd->SerialDriver.flags = (TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_HARDWARE_BREAK);

        /*
         * The kernel wants space to store pointers to
         * tty_struct's and termios's.
         */
        brd->SerialDriver.ttys = kcalloc(brd->maxports, sizeof(*brd->SerialDriver.ttys), GFP_KERNEL);
        if (!brd->SerialDriver.ttys)
                return -ENOMEM;

        kref_init(&brd->SerialDriver.kref);
        brd->SerialDriver.termios = kcalloc(brd->maxports, sizeof(*brd->SerialDriver.termios), GFP_KERNEL);
        if (!brd->SerialDriver.termios)
                return -ENOMEM;

        /*
         * Entry points for driver.  Called by the kernel from
         * tty_io.c and n_tty.c.
         */
        tty_set_operations(&brd->SerialDriver, &dgnc_tty_ops);

        if (!brd->dgnc_Major_Serial_Registered) {
                /* Register tty devices */
                rc = tty_register_driver(&brd->SerialDriver);
                if (rc < 0) {
                        dev_dbg(&brd->pdev->dev,
                                "Can't register tty device (%d)\n", rc);
                        return rc;
                }
                brd->dgnc_Major_Serial_Registered = true;
        }

        /*
         * If we're doing transparent print, we have to do all of the above
         * again, separately so we don't get the LD confused about what major
         * we are when we get into the dgnc_tty_open() routine.
         */
        brd->PrintDriver.magic = TTY_DRIVER_MAGIC;
        snprintf(brd->PrintName, MAXTTYNAMELEN, "pr_dgnc_%d_", brd->boardnum);

        brd->PrintDriver.name = brd->PrintName;
        brd->PrintDriver.name_base = 0;
        brd->PrintDriver.major = brd->SerialDriver.major;
        brd->PrintDriver.minor_start = 0x80;
        brd->PrintDriver.num = brd->maxports;
        brd->PrintDriver.type = TTY_DRIVER_TYPE_SERIAL;
        brd->PrintDriver.subtype = SERIAL_TYPE_NORMAL;
        brd->PrintDriver.init_termios = DgncDefaultTermios;
        brd->PrintDriver.driver_name = DRVSTR;
        brd->PrintDriver.flags = (TTY_DRIVER_REAL_RAW | TTY_DRIVER_DYNAMIC_DEV | TTY_DRIVER_HARDWARE_BREAK);

        /*
         * The kernel wants space to store pointers to
         * tty_struct's and termios's.  Must be separated from
         * the Serial Driver so we don't get confused
         */
        brd->PrintDriver.ttys = kcalloc(brd->maxports, sizeof(*brd->PrintDriver.ttys), GFP_KERNEL);
        if (!brd->PrintDriver.ttys)
                return -ENOMEM;
        kref_init(&brd->PrintDriver.kref);
        brd->PrintDriver.termios = kcalloc(brd->maxports, sizeof(*brd->PrintDriver.termios), GFP_KERNEL);
        if (!brd->PrintDriver.termios)
                return -ENOMEM;

        /*
         * Entry points for driver.  Called by the kernel from
         * tty_io.c and n_tty.c.
         */
        tty_set_operations(&brd->PrintDriver, &dgnc_tty_ops);

        if (!brd->dgnc_Major_TransparentPrint_Registered) {
                /* Register Transparent Print devices */
                rc = tty_register_driver(&brd->PrintDriver);
                if (rc < 0) {
                        dev_dbg(&brd->pdev->dev,
                                "Can't register Transparent Print device(%d)\n",
                                rc);
                        return rc;
                }
                brd->dgnc_Major_TransparentPrint_Registered = true;
        }

        dgnc_BoardsByMajor[brd->SerialDriver.major] = brd;
        brd->dgnc_Serial_Major = brd->SerialDriver.major;
        brd->dgnc_TransparentPrint_Major = brd->PrintDriver.major;

        return rc;
}


/*
 * dgnc_tty_init()
 *
 * Init the tty subsystem.  Called once per board after board has been
 * downloaded and init'ed.
 */
int dgnc_tty_init(struct dgnc_board *brd)
{
        int i;
        void __iomem *vaddr;
        struct channel_t *ch;

        if (!brd)
                return -ENXIO;

        /*
         * Initialize board structure elements.
         */

        vaddr = brd->re_map_membase;

        brd->nasync = brd->maxports;

        /*
         * Allocate channel memory that might not have been allocated
         * when the driver was first loaded.
         */
        for (i = 0; i < brd->nasync; i++) {
                if (!brd->channels[i]) {

                        /*
                         * Okay to malloc with GFP_KERNEL, we are not at
                         * interrupt context, and there are no locks held.
                         */
                        brd->channels[i] = kzalloc(sizeof(*brd->channels[i]), GFP_KERNEL);
                }
        }

        ch = brd->channels[0];
        vaddr = brd->re_map_membase;

        /* Set up channel variables */
        for (i = 0; i < brd->nasync; i++, ch = brd->channels[i]) {

                if (!brd->channels[i])
                        continue;

                spin_lock_init(&ch->ch_lock);

                /* Store all our magic numbers */
                ch->magic = DGNC_CHANNEL_MAGIC;
                ch->ch_tun.magic = DGNC_UNIT_MAGIC;
                ch->ch_tun.un_ch = ch;
                ch->ch_tun.un_type = DGNC_SERIAL;
                ch->ch_tun.un_dev = i;

                ch->ch_pun.magic = DGNC_UNIT_MAGIC;
                ch->ch_pun.un_ch = ch;
                ch->ch_pun.un_type = DGNC_PRINT;
                ch->ch_pun.un_dev = i + 128;

                if (brd->bd_uart_offset == 0x200)
                        ch->ch_neo_uart = vaddr + (brd->bd_uart_offset * i);
                else
                        ch->ch_cls_uart = vaddr + (brd->bd_uart_offset * i);

                ch->ch_bd = brd;
                ch->ch_portnum = i;
                ch->ch_digi = dgnc_digi_init;

                /* .25 second delay */
                ch->ch_close_delay = 250;

                init_waitqueue_head(&ch->ch_flags_wait);
                init_waitqueue_head(&ch->ch_tun.un_flags_wait);
                init_waitqueue_head(&ch->ch_pun.un_flags_wait);

                {
                        struct device *classp;

                        classp = tty_register_device(&brd->SerialDriver, i,
                                &(ch->ch_bd->pdev->dev));
                        ch->ch_tun.un_sysfs = classp;
                        dgnc_create_tty_sysfs(&ch->ch_tun, classp);

                        classp = tty_register_device(&brd->PrintDriver, i,
                                &(ch->ch_bd->pdev->dev));
                        ch->ch_pun.un_sysfs = classp;
                        dgnc_create_tty_sysfs(&ch->ch_pun, classp);
                }

        }

        return 0;
}


/*
 * dgnc_tty_post_uninit()
 *
 * UnInitialize any global tty related data.
 */
void dgnc_tty_post_uninit(void)
{
        kfree(dgnc_TmpWriteBuf);
        dgnc_TmpWriteBuf = NULL;
}


/*
 * dgnc_tty_uninit()
 *
 * Uninitialize the TTY portion of this driver.  Free all memory and
 * resources.
 */
void dgnc_tty_uninit(struct dgnc_board *brd)
{
        int i = 0;

        if (brd->dgnc_Major_Serial_Registered) {
                dgnc_BoardsByMajor[brd->SerialDriver.major] = NULL;
                brd->dgnc_Serial_Major = 0;
                for (i = 0; i < brd->nasync; i++) {
                        dgnc_remove_tty_sysfs(brd->channels[i]->ch_tun.un_sysfs);
                        tty_unregister_device(&brd->SerialDriver, i);
                }
                tty_unregister_driver(&brd->SerialDriver);
                brd->dgnc_Major_Serial_Registered = false;
        }

        if (brd->dgnc_Major_TransparentPrint_Registered) {
                dgnc_BoardsByMajor[brd->PrintDriver.major] = NULL;
                brd->dgnc_TransparentPrint_Major = 0;
                for (i = 0; i < brd->nasync; i++) {
                        dgnc_remove_tty_sysfs(brd->channels[i]->ch_pun.un_sysfs);
                        tty_unregister_device(&brd->PrintDriver, i);
                }
                tty_unregister_driver(&brd->PrintDriver);
                brd->dgnc_Major_TransparentPrint_Registered = false;
        }

        kfree(brd->SerialDriver.ttys);
        brd->SerialDriver.ttys = NULL;
        kfree(brd->PrintDriver.ttys);
        brd->PrintDriver.ttys = NULL;
}


#define TMPBUFLEN (1024)

/*=======================================================================
 *
 *      dgnc_wmove - Write data to transmit queue.
 *
 *              ch      - Pointer to channel structure.
 *              buf     - Poiter to characters to be moved.
 *              n       - Number of characters to move.
 *
 *=======================================================================*/
static void dgnc_wmove(struct channel_t *ch, char *buf, uint n)
{
        int     remain;
        uint    head;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        head = ch->ch_w_head & WQUEUEMASK;

        /*
         * If the write wraps over the top of the circular buffer,
         * move the portion up to the wrap point, and reset the
         * pointers to the bottom.
         */
        remain = WQUEUESIZE - head;

        if (n >= remain) {
                n -= remain;
                memcpy(ch->ch_wqueue + head, buf, remain);
                head = 0;
                buf += remain;
        }

        if (n > 0) {
                /*
                 * Move rest of data.
                 */
                remain = n;
                memcpy(ch->ch_wqueue + head, buf, remain);
                head += remain;
        }

        head &= WQUEUEMASK;
        ch->ch_w_head = head;
}




/*=======================================================================
 *
 *      dgnc_input - Process received data.
 *
 *            ch      - Pointer to channel structure.
 *
 *=======================================================================*/
void dgnc_input(struct channel_t *ch)
{
        struct dgnc_board *bd;
        struct tty_struct *tp;
        struct tty_ldisc *ld = NULL;
        uint    rmask;
        ushort  head;
        ushort  tail;
        int     data_len;
        unsigned long flags;
        int flip_len;
        int len = 0;
        int n = 0;
        int s = 0;
        int i = 0;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        tp = ch->ch_tun.un_tty;

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return;

        spin_lock_irqsave(&ch->ch_lock, flags);

        /*
         *      Figure the number of characters in the buffer.
         *      Exit immediately if none.
         */
        rmask = RQUEUEMASK;
        head = ch->ch_r_head & rmask;
        tail = ch->ch_r_tail & rmask;
        data_len = (head - tail) & rmask;

        if (data_len == 0)
                goto exit_unlock;

        /*
         * If the device is not open, or CREAD is off,
         * flush input data and return immediately.
         */
        if (!tp || (tp->magic != TTY_MAGIC) || !(ch->ch_tun.un_flags & UN_ISOPEN) ||
            !(tp->termios.c_cflag & CREAD) || (ch->ch_tun.un_flags & UN_CLOSING)) {

                ch->ch_r_head = tail;

                /* Force queue flow control to be released, if needed */
                dgnc_check_queue_flow_control(ch);

                goto exit_unlock;
        }

        /*
         * If we are throttled, simply don't read any data.
         */
        if (ch->ch_flags & CH_FORCED_STOPI)
                goto exit_unlock;

        flip_len = TTY_FLIPBUF_SIZE;

        /* Chop down the length, if needed */
        len = min(data_len, flip_len);
        len = min(len, (N_TTY_BUF_SIZE - 1));

        ld = tty_ldisc_ref(tp);

#ifdef TTY_DONT_FLIP
        /*
         * If the DONT_FLIP flag is on, don't flush our buffer, and act
         * like the ld doesn't have any space to put the data right now.
         */
        if (test_bit(TTY_DONT_FLIP, &tp->flags))
                len = 0;
#endif

        /*
         * If we were unable to get a reference to the ld,
         * don't flush our buffer, and act like the ld doesn't
         * have any space to put the data right now.
         */
        if (!ld) {
                len = 0;
        } else {
                /*
                 * If ld doesn't have a pointer to a receive_buf function,
                 * flush the data, then act like the ld doesn't have any
                 * space to put the data right now.
                 */
                if (!ld->ops->receive_buf) {
                        ch->ch_r_head = ch->ch_r_tail;
                        len = 0;
                }
        }

        if (len <= 0)
                goto exit_unlock;

        /*
         * The tty layer in the kernel has changed in 2.6.16+.
         *
         * The flip buffers in the tty structure are no longer exposed,
         * and probably will be going away eventually.
         *
         * If we are completely raw, we don't need to go through a lot
         * of the tty layers that exist.
         * In this case, we take the shortest and fastest route we
         * can to relay the data to the user.
         *
         * On the other hand, if we are not raw, we need to go through
         * the new 2.6.16+ tty layer, which has its API more well defined.
         */
        len = tty_buffer_request_room(tp->port, len);
        n = len;

        /*
         * n now contains the most amount of data we can copy,
         * bounded either by how much the Linux tty layer can handle,
         * or the amount of data the card actually has pending...
         */
        while (n) {
                s = ((head >= tail) ? head : RQUEUESIZE) - tail;
                s = min(s, n);

                if (s <= 0)
                        break;

                /*
                 * If conditions are such that ld needs to see all
                 * UART errors, we will have to walk each character
                 * and error byte and send them to the buffer one at
                 * a time.
                 */
                if (I_PARMRK(tp) || I_BRKINT(tp) || I_INPCK(tp)) {
                        for (i = 0; i < s; i++) {
                                if (*(ch->ch_equeue + tail + i) & UART_LSR_BI)
                                        tty_insert_flip_char(tp->port, *(ch->ch_rqueue + tail + i), TTY_BREAK);
                                else if (*(ch->ch_equeue + tail + i) & UART_LSR_PE)
                                        tty_insert_flip_char(tp->port, *(ch->ch_rqueue + tail + i), TTY_PARITY);
                                else if (*(ch->ch_equeue + tail + i) & UART_LSR_FE)
                                        tty_insert_flip_char(tp->port, *(ch->ch_rqueue + tail + i), TTY_FRAME);
                                else
                                        tty_insert_flip_char(tp->port, *(ch->ch_rqueue + tail + i), TTY_NORMAL);
                        }
                } else {
                        tty_insert_flip_string(tp->port, ch->ch_rqueue + tail, s);
                }

                tail += s;
                n -= s;
                /* Flip queue if needed */
                tail &= rmask;
        }

        ch->ch_r_tail = tail & rmask;
        ch->ch_e_tail = tail & rmask;
        dgnc_check_queue_flow_control(ch);
        spin_unlock_irqrestore(&ch->ch_lock, flags);

        /* Tell the tty layer its okay to "eat" the data now */
        tty_flip_buffer_push(tp->port);

        if (ld)
                tty_ldisc_deref(ld);
        return;

exit_unlock:
        spin_unlock_irqrestore(&ch->ch_lock, flags);
        if (ld)
                tty_ldisc_deref(ld);
}


/************************************************************************
 * Determines when CARRIER changes state and takes appropriate
 * action.
 ************************************************************************/
void dgnc_carrier(struct channel_t *ch)
{
        struct dgnc_board *bd;

        int virt_carrier = 0;
        int phys_carrier = 0;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        bd = ch->ch_bd;

        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return;

        if (ch->ch_mistat & UART_MSR_DCD)
                phys_carrier = 1;

        if (ch->ch_digi.digi_flags & DIGI_FORCEDCD)
                virt_carrier = 1;

        if (ch->ch_c_cflag & CLOCAL)
                virt_carrier = 1;

        /*
         * Test for a VIRTUAL carrier transition to HIGH.
         */
        if (((ch->ch_flags & CH_FCAR) == 0) && (virt_carrier == 1)) {

                /*
                 * When carrier rises, wake any threads waiting
                 * for carrier in the open routine.
                 */

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

        /*
         * Test for a PHYSICAL carrier transition to HIGH.
         */
        if (((ch->ch_flags & CH_CD) == 0) && (phys_carrier == 1)) {

                /*
                 * When carrier rises, wake any threads waiting
                 * for carrier in the open routine.
                 */

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

        /*
         *  Test for a PHYSICAL transition to low, so long as we aren't
         *  currently ignoring physical transitions (which is what "virtual
         *  carrier" indicates).
         *
         *  The transition of the virtual carrier to low really doesn't
         *  matter... it really only means "ignore carrier state", not
         *  "make pretend that carrier is there".
         */
        if ((virt_carrier == 0) && ((ch->ch_flags & CH_CD) != 0) &&
            (phys_carrier == 0)) {

                /*
                 *   When carrier drops:
                 *
                 *   Drop carrier on all open units.
                 *
                 *   Flush queues, waking up any task waiting in the
                 *   line discipline.
                 *
                 *   Send a hangup to the control terminal.
                 *
                 *   Enable all select calls.
                 */
                if (waitqueue_active(&(ch->ch_flags_wait)))
                        wake_up_interruptible(&ch->ch_flags_wait);

                if (ch->ch_tun.un_open_count > 0)
                        tty_hangup(ch->ch_tun.un_tty);

                if (ch->ch_pun.un_open_count > 0)
                        tty_hangup(ch->ch_pun.un_tty);
        }

        /*
         *  Make sure that our cached values reflect the current reality.
         */
        if (virt_carrier == 1)
                ch->ch_flags |= CH_FCAR;
        else
                ch->ch_flags &= ~CH_FCAR;

        if (phys_carrier == 1)
                ch->ch_flags |= CH_CD;
        else
                ch->ch_flags &= ~CH_CD;
}

/*
 *  Assign the custom baud rate to the channel structure
 */
static void dgnc_set_custom_speed(struct channel_t *ch, uint newrate)
{
        int testdiv;
        int testrate_high;
        int testrate_low;
        int deltahigh;
        int deltalow;

        if (newrate <= 0) {
                ch->ch_custom_speed = 0;
                return;
        }

        /*
         *  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 < ((ch->ch_bd->bd_dividend / 0xFFFF) + 1))
                newrate = ((ch->ch_bd->bd_dividend / 0xFFFF) + 1);

        if (newrate && newrate > ch->ch_bd->bd_dividend)
                newrate = ch->ch_bd->bd_dividend;

        if (newrate > 0) {
                testdiv = ch->ch_bd->bd_dividend / newrate;

                /*
                 *  If we try to figure out what rate the board 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 = ch->ch_bd->bd_dividend / testdiv;
                testrate_low  = ch->ch_bd->bd_dividend / (testdiv + 1);

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

        ch->ch_custom_speed = newrate;
}


void dgnc_check_queue_flow_control(struct channel_t *ch)
{
        int qleft = 0;

        /* Store how much space we have left in the queue */
        qleft = ch->ch_r_tail - ch->ch_r_head - 1;
        if (qleft < 0)
                qleft += RQUEUEMASK + 1;

        /*
         * Check to see if we should enforce flow control on our queue because
         * the ld (or user) isn't reading data out of our queue fast enuf.
         *
         * NOTE: This is done based on what the current flow control of the
         * port is set for.
         *
         * 1) HWFLOW (RTS) - Turn off the UART's Receive interrupt.
         *      This will cause the UART's FIFO to back up, and force
         *      the RTS signal to be dropped.
         * 2) SWFLOW (IXOFF) - Keep trying to send a stop character to
         *      the other side, in hopes it will stop sending data to us.
         * 3) NONE - Nothing we can do.  We will simply drop any extra data
         *      that gets sent into us when the queue fills up.
         */
        if (qleft < 256) {
                /* HWFLOW */
                if (ch->ch_digi.digi_flags & CTSPACE || ch->ch_c_cflag & CRTSCTS) {
                        if (!(ch->ch_flags & CH_RECEIVER_OFF)) {
                                ch->ch_bd->bd_ops->disable_receiver(ch);
                                ch->ch_flags |= (CH_RECEIVER_OFF);
                        }
                }
                /* SWFLOW */
                else if (ch->ch_c_iflag & IXOFF) {
                        if (ch->ch_stops_sent <= MAX_STOPS_SENT) {
                                ch->ch_bd->bd_ops->send_stop_character(ch);
                                ch->ch_stops_sent++;
                        }
                }
        }

        /*
         * Check to see if we should unenforce flow control because
         * ld (or user) finally read enuf data out of our queue.
         *
         * NOTE: This is done based on what the current flow control of the
         * port is set for.
         *
         * 1) HWFLOW (RTS) - Turn back on the UART's Receive interrupt.
         *      This will cause the UART's FIFO to raise RTS back up,
         *      which will allow the other side to start sending data again.
         * 2) SWFLOW (IXOFF) - Send a start character to
         *      the other side, so it will start sending data to us again.
         * 3) NONE - Do nothing. Since we didn't do anything to turn off the
         *      other side, we don't need to do anything now.
         */
        if (qleft > (RQUEUESIZE / 2)) {
                /* HWFLOW */
                if (ch->ch_digi.digi_flags & RTSPACE || ch->ch_c_cflag & CRTSCTS) {
                        if (ch->ch_flags & CH_RECEIVER_OFF) {
                                ch->ch_bd->bd_ops->enable_receiver(ch);
                                ch->ch_flags &= ~(CH_RECEIVER_OFF);
                        }
                }
                /* SWFLOW */
                else if (ch->ch_c_iflag & IXOFF && ch->ch_stops_sent) {
                        ch->ch_stops_sent = 0;
                        ch->ch_bd->bd_ops->send_start_character(ch);
                }
                /* No FLOW */
                else {
                        /* Nothing needed. */
                }
        }
}


void dgnc_wakeup_writes(struct channel_t *ch)
{
        int qlen = 0;
        unsigned long flags;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return;

        spin_lock_irqsave(&ch->ch_lock, flags);

        /*
         * If channel now has space, wake up anyone waiting on the condition.
         */
        qlen = ch->ch_w_head - ch->ch_w_tail;
        if (qlen < 0)
                qlen += WQUEUESIZE;

        if (qlen >= (WQUEUESIZE - 256)) {
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return;
        }

        if (ch->ch_tun.un_flags & UN_ISOPEN) {
                if ((ch->ch_tun.un_tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
                        ch->ch_tun.un_tty->ldisc->ops->write_wakeup) {
                        spin_unlock_irqrestore(&ch->ch_lock, flags);
                        (ch->ch_tun.un_tty->ldisc->ops->write_wakeup)(ch->ch_tun.un_tty);
                        spin_lock_irqsave(&ch->ch_lock, flags);
                }

                wake_up_interruptible(&ch->ch_tun.un_tty->write_wait);

                /*
                 * If unit is set to wait until empty, check to make sure
                 * the queue AND FIFO are both empty.
                 */
                if (ch->ch_tun.un_flags & UN_EMPTY) {
                        if ((qlen == 0) && (ch->ch_bd->bd_ops->get_uart_bytes_left(ch) == 0)) {
                                ch->ch_tun.un_flags &= ~(UN_EMPTY);

                                /*
                                 * If RTS Toggle mode is on, whenever
                                 * the queue and UART is empty, keep RTS low.
                                 */
                                if (ch->ch_digi.digi_flags & DIGI_RTS_TOGGLE) {
                                        ch->ch_mostat &= ~(UART_MCR_RTS);
                                        ch->ch_bd->bd_ops->assert_modem_signals(ch);
                                }

                                /*
                                 * If DTR Toggle mode is on, whenever
                                 * the queue and UART is empty, keep DTR low.
                                 */
                                if (ch->ch_digi.digi_flags & DIGI_DTR_TOGGLE) {
                                        ch->ch_mostat &= ~(UART_MCR_DTR);
                                        ch->ch_bd->bd_ops->assert_modem_signals(ch);
                                }
                        }
                }

                wake_up_interruptible(&ch->ch_tun.un_flags_wait);
        }

        if (ch->ch_pun.un_flags & UN_ISOPEN) {
                if ((ch->ch_pun.un_tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&
                        ch->ch_pun.un_tty->ldisc->ops->write_wakeup) {
                        spin_unlock_irqrestore(&ch->ch_lock, flags);
                        (ch->ch_pun.un_tty->ldisc->ops->write_wakeup)(ch->ch_pun.un_tty);
                        spin_lock_irqsave(&ch->ch_lock, flags);
                }

                wake_up_interruptible(&ch->ch_pun.un_tty->write_wait);

                /*
                 * If unit is set to wait until empty, check to make sure
                 * the queue AND FIFO are both empty.
                 */
                if (ch->ch_pun.un_flags & UN_EMPTY) {
                        if ((qlen == 0) && (ch->ch_bd->bd_ops->get_uart_bytes_left(ch) == 0))
                                ch->ch_pun.un_flags &= ~(UN_EMPTY);
                }

                wake_up_interruptible(&ch->ch_pun.un_flags_wait);
        }

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}



/************************************************************************
 *
 * TTY Entry points and helper functions

 *
 ************************************************************************/

/*
 * dgnc_tty_open()
 *
 */
static int dgnc_tty_open(struct tty_struct *tty, struct file *file)
{
        struct dgnc_board       *brd;
        struct channel_t *ch;
        struct un_t     *un;
        uint            major = 0;
        uint            minor = 0;
        int             rc = 0;
        unsigned long flags;

        rc = 0;

        major = MAJOR(tty_devnum(tty));
        minor = MINOR(tty_devnum(tty));

        if (major > 255)
                return -ENXIO;

        /* Get board pointer from our array of majors we have allocated */
        brd = dgnc_BoardsByMajor[major];
        if (!brd)
                return -ENXIO;

        /*
         * If board is not yet up to a state of READY, go to
         * sleep waiting for it to happen or they cancel the open.
         */
        rc = wait_event_interruptible(brd->state_wait,
                (brd->state & BOARD_READY));

        if (rc)
                return rc;

        spin_lock_irqsave(&brd->bd_lock, flags);

        /* If opened device is greater than our number of ports, bail. */
        if (PORT_NUM(minor) >= brd->nasync) {
                spin_unlock_irqrestore(&brd->bd_lock, flags);
                return -ENXIO;
        }

        ch = brd->channels[PORT_NUM(minor)];
        if (!ch) {
                spin_unlock_irqrestore(&brd->bd_lock, flags);
                return -ENXIO;
        }

        /* Drop board lock */
        spin_unlock_irqrestore(&brd->bd_lock, flags);

        /* Grab channel lock */
        spin_lock_irqsave(&ch->ch_lock, flags);

        /* Figure out our type */
        if (!IS_PRINT(minor)) {
                un = &brd->channels[PORT_NUM(minor)]->ch_tun;
                un->un_type = DGNC_SERIAL;
        } else if (IS_PRINT(minor)) {
                un = &brd->channels[PORT_NUM(minor)]->ch_pun;
                un->un_type = DGNC_PRINT;
        } else {
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return -ENXIO;
        }

        /*
         * If the port is still in a previous open, and in a state
         * where we simply cannot safely keep going, wait until the
         * state clears.
         */
        spin_unlock_irqrestore(&ch->ch_lock, flags);

        rc = wait_event_interruptible(ch->ch_flags_wait, ((ch->ch_flags & CH_OPENING) == 0));

        /* If ret is non-zero, user ctrl-c'ed us */
        if (rc)
                return -EINTR;

        /*
         * If either unit is in the middle of the fragile part of close,
         * we just cannot touch the channel safely.
         * Go to sleep, knowing that when the channel can be
         * touched safely, the close routine will signal the
         * ch_flags_wait to wake us back up.
         */
        rc = wait_event_interruptible(ch->ch_flags_wait,
                (((ch->ch_tun.un_flags | ch->ch_pun.un_flags) & UN_CLOSING) == 0));

        /* If ret is non-zero, user ctrl-c'ed us */
        if (rc)
                return -EINTR;

        spin_lock_irqsave(&ch->ch_lock, flags);


        /* Store our unit into driver_data, so we always have it available. */
        tty->driver_data = un;


        /*
         * Initialize tty's
         */
        if (!(un->un_flags & UN_ISOPEN)) {
                /* Store important variables. */
                un->un_tty     = tty;

                /* Maybe do something here to the TTY struct as well? */
        }


        /*
         * Allocate channel buffers for read/write/error.
         * Set flag, so we don't get trounced on.
         */
        ch->ch_flags |= (CH_OPENING);

        /* Drop locks, as malloc with GFP_KERNEL can sleep */
        spin_unlock_irqrestore(&ch->ch_lock, flags);

        if (!ch->ch_rqueue)
                ch->ch_rqueue = kzalloc(RQUEUESIZE, GFP_KERNEL);
        if (!ch->ch_equeue)
                ch->ch_equeue = kzalloc(EQUEUESIZE, GFP_KERNEL);
        if (!ch->ch_wqueue)
                ch->ch_wqueue = kzalloc(WQUEUESIZE, GFP_KERNEL);

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_flags &= ~(CH_OPENING);
        wake_up_interruptible(&ch->ch_flags_wait);

        /*
         * Initialize if neither terminal or printer is open.
         */
        if (!((ch->ch_tun.un_flags | ch->ch_pun.un_flags) & UN_ISOPEN)) {

                /*
                 * Flush input queues.
                 */
                ch->ch_r_head = 0;
                ch->ch_r_tail = 0;
                ch->ch_e_head = 0;
                ch->ch_e_tail = 0;
                ch->ch_w_head = 0;
                ch->ch_w_tail = 0;

                brd->bd_ops->flush_uart_write(ch);
                brd->bd_ops->flush_uart_read(ch);

                ch->ch_flags = 0;
                ch->ch_cached_lsr = 0;
                ch->ch_stop_sending_break = 0;
                ch->ch_stops_sent = 0;

                ch->ch_c_cflag   = tty->termios.c_cflag;
                ch->ch_c_iflag   = tty->termios.c_iflag;
                ch->ch_c_oflag   = tty->termios.c_oflag;
                ch->ch_c_lflag   = tty->termios.c_lflag;
                ch->ch_startc = tty->termios.c_cc[VSTART];
                ch->ch_stopc  = tty->termios.c_cc[VSTOP];

                /*
                 * Bring up RTS and DTR...
                 * Also handle RTS or DTR toggle if set.
                 */
                if (!(ch->ch_digi.digi_flags & DIGI_RTS_TOGGLE))
                        ch->ch_mostat |= (UART_MCR_RTS);
                if (!(ch->ch_digi.digi_flags & DIGI_DTR_TOGGLE))
                        ch->ch_mostat |= (UART_MCR_DTR);

                /* Tell UART to init itself */
                brd->bd_ops->uart_init(ch);
        }

        /*
         * Run param in case we changed anything
         */
        brd->bd_ops->param(tty);

        dgnc_carrier(ch);

        /*
         * follow protocol for opening port
         */

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        rc = dgnc_block_til_ready(tty, file, ch);

        /* No going back now, increment our unit and channel counters */
        spin_lock_irqsave(&ch->ch_lock, flags);
        ch->ch_open_count++;
        un->un_open_count++;
        un->un_flags |= (UN_ISOPEN);
        spin_unlock_irqrestore(&ch->ch_lock, flags);

        return rc;
}


/*
 * dgnc_block_til_ready()
 *
 * Wait for DCD, if needed.
 */
static int dgnc_block_til_ready(struct tty_struct *tty, struct file *file, struct channel_t *ch)
{
        int retval = 0;
        struct un_t *un = NULL;
        unsigned long flags;
        uint    old_flags = 0;
        int     sleep_on_un_flags = 0;

        if (!tty || tty->magic != TTY_MAGIC || !file || !ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return -ENXIO;

        un = tty->driver_data;
        if (!un || un->magic != DGNC_UNIT_MAGIC)
                return -ENXIO;

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_wopen++;

        /* Loop forever */
        while (1) {

                sleep_on_un_flags = 0;

                /*
                 * If board has failed somehow during our sleep, bail with error.
                 */
                if (ch->ch_bd->state == BOARD_FAILED) {
                        retval = -ENXIO;
                        break;
                }

                /* If tty was hung up, break out of loop and set error. */
                if (tty_hung_up_p(file)) {
                        retval = -EAGAIN;
                        break;
                }

                /*
                 * If either unit is in the middle of the fragile part of close,
                 * we just cannot touch the channel safely.
                 * Go back to sleep, knowing that when the channel can be
                 * touched safely, the close routine will signal the
                 * ch_wait_flags to wake us back up.
                 */
                if (!((ch->ch_tun.un_flags | ch->ch_pun.un_flags) & UN_CLOSING)) {

                        /*
                         * Our conditions to leave cleanly and happily:
                         * 1) NONBLOCKING on the tty is set.
                         * 2) CLOCAL is set.
                         * 3) DCD (fake or real) is active.
                         */

                        if (file->f_flags & O_NONBLOCK)
                                break;

                        if (tty->flags & (1 << TTY_IO_ERROR)) {
                                retval = -EIO;
                                break;
                        }

                        if (ch->ch_flags & CH_CD)
                                break;

                        if (ch->ch_flags & CH_FCAR)
                                break;
                } else {
                        sleep_on_un_flags = 1;
                }

                /*
                 * If there is a signal pending, the user probably
                 * interrupted (ctrl-c) us.
                 * Leave loop with error set.
                 */
                if (signal_pending(current)) {
                        retval = -ERESTARTSYS;
                        break;
                }

                /*
                 * Store the flags before we let go of channel lock
                 */
                if (sleep_on_un_flags)
                        old_flags = ch->ch_tun.un_flags | ch->ch_pun.un_flags;
                else
                        old_flags = ch->ch_flags;

                /*
                 * Let go of channel lock before calling schedule.
                 * Our poller will get any FEP events and wake us up when DCD
                 * eventually goes active.
                 */

                spin_unlock_irqrestore(&ch->ch_lock, flags);

                /*
                 * Wait for something in the flags to change from the current value.
                 */
                if (sleep_on_un_flags)
                        retval = wait_event_interruptible(un->un_flags_wait,
                                (old_flags != (ch->ch_tun.un_flags | ch->ch_pun.un_flags)));
                else
                        retval = wait_event_interruptible(ch->ch_flags_wait,
                                (old_flags != ch->ch_flags));

                /*
                 * We got woken up for some reason.
                 * Before looping around, grab our channel lock.
                 */
                spin_lock_irqsave(&ch->ch_lock, flags);
        }

        ch->ch_wopen--;

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        if (retval)
                return retval;

        return 0;
}


/*
 * dgnc_tty_hangup()
 *
 * Hangup the port.  Like a close, but don't wait for output to drain.
 */
static void dgnc_tty_hangup(struct tty_struct *tty)
{
        struct un_t     *un;

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

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

        /* flush the transmit queues */
        dgnc_tty_flush_buffer(tty);

}


/*
 * dgnc_tty_close()
 *
 */
static void dgnc_tty_close(struct tty_struct *tty, struct file *file)
{
        struct ktermios *ts;
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        unsigned long flags;
        int rc = 0;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return;

        ts = &tty->termios;

        spin_lock_irqsave(&ch->ch_lock, flags);

        /*
         * Determine if this is the last close or not - and if we agree about
         * which type of close it is with the Line Discipline
         */
        if ((tty->count == 1) && (un->un_open_count != 1)) {
                /*
                 * Uh, oh.  tty->count is 1, which means that the tty
                 * structure will be freed.  un_open_count should always
                 * be one in these conditions.  If it's greater than
                 * one, we've got real problems, since it means the
                 * serial port won't be shutdown.
                 */
                dev_dbg(tty->dev,
                        "tty->count is 1, un open count is %d\n",
                        un->un_open_count);
                un->un_open_count = 1;
        }

        if (un->un_open_count)
                un->un_open_count--;
        else
                dev_dbg(tty->dev,
                        "bad serial port open count of %d\n",
                        un->un_open_count);

        ch->ch_open_count--;

        if (ch->ch_open_count && un->un_open_count) {
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return;
        }

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

        tty->closing = 1;


        /*
         * Only officially close channel if count is 0 and
         * DIGI_PRINTER bit is not set.
         */
        if ((ch->ch_open_count == 0) && !(ch->ch_digi.digi_flags & DIGI_PRINTER)) {

                ch->ch_flags &= ~(CH_STOPI | CH_FORCED_STOPI);

                /*
                 * turn off print device when closing print device.
                 */
                if ((un->un_type == DGNC_PRINT) && (ch->ch_flags & CH_PRON)) {
                        dgnc_wmove(ch, ch->ch_digi.digi_offstr,
                                (int) ch->ch_digi.digi_offlen);
                        ch->ch_flags &= ~CH_PRON;
                }

                spin_unlock_irqrestore(&ch->ch_lock, flags);
                /* wait for output to drain */
                /* This will also return if we take an interrupt */

                rc = bd->bd_ops->drain(tty, 0);

                dgnc_tty_flush_buffer(tty);
                tty_ldisc_flush(tty);

                spin_lock_irqsave(&ch->ch_lock, flags);

                tty->closing = 0;

                /*
                 * If we have HUPCL set, lower DTR and RTS
                 */
                if (ch->ch_c_cflag & HUPCL) {

                        /* Drop RTS/DTR */
                        ch->ch_mostat &= ~(UART_MCR_DTR | UART_MCR_RTS);
                        bd->bd_ops->assert_modem_signals(ch);

                        /*
                         * Go to sleep to ensure RTS/DTR
                         * have been dropped for modems to see it.
                         */
                        if (ch->ch_close_delay) {
                                spin_unlock_irqrestore(&ch->ch_lock,
                                                       flags);
                                dgnc_ms_sleep(ch->ch_close_delay);
                                spin_lock_irqsave(&ch->ch_lock, flags);
                        }
                }

                ch->ch_old_baud = 0;

                /* Turn off UART interrupts for this port */
                ch->ch_bd->bd_ops->uart_off(ch);
        } else {
                /*
                 * turn off print device when closing print device.
                 */
                if ((un->un_type == DGNC_PRINT) && (ch->ch_flags & CH_PRON)) {
                        dgnc_wmove(ch, ch->ch_digi.digi_offstr,
                                (int) ch->ch_digi.digi_offlen);
                        ch->ch_flags &= ~CH_PRON;
                }
        }

        un->un_tty = NULL;
        un->un_flags &= ~(UN_ISOPEN | UN_CLOSING);

        wake_up_interruptible(&ch->ch_flags_wait);
        wake_up_interruptible(&un->un_flags_wait);

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}


/*
 * dgnc_tty_chars_in_buffer()
 *
 * Return number of characters that have not been transmitted yet.
 *
 * This routine is used by the line discipline to determine if there
 * is data waiting to be transmitted/drained/flushed or not.
 */
static int dgnc_tty_chars_in_buffer(struct tty_struct *tty)
{
        struct channel_t *ch = NULL;
        struct un_t *un = NULL;
        ushort thead;
        ushort ttail;
        uint tmask;
        uint chars = 0;
        unsigned long flags;

        if (tty == NULL)
                return 0;

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

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

        spin_lock_irqsave(&ch->ch_lock, flags);

        tmask = WQUEUEMASK;
        thead = ch->ch_w_head & tmask;
        ttail = ch->ch_w_tail & tmask;

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        if (ttail == thead) {
                chars = 0;
        } else {
                if (thead >= ttail)
                        chars = thead - ttail;
                else
                        chars = thead - ttail + WQUEUESIZE;
        }

        return chars;
}


/*
 * dgnc_maxcps_room
 *
 * Reduces bytes_available to the max number of characters
 * that can be sent currently given the maxcps value, and
 * returns the new bytes_available.  This only affects printer
 * output.
 */
static int dgnc_maxcps_room(struct tty_struct *tty, int bytes_available)
{
        struct channel_t *ch = NULL;
        struct un_t *un = NULL;

        if (!tty)
                return bytes_available;

        un = tty->driver_data;
        if (!un || un->magic != DGNC_UNIT_MAGIC)
                return bytes_available;

        ch = un->un_ch;
        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return bytes_available;

        /*
         * If its not the Transparent print device, return
         * the full data amount.
         */
        if (un->un_type != DGNC_PRINT)
                return bytes_available;

        if (ch->ch_digi.digi_maxcps > 0 && ch->ch_digi.digi_bufsize > 0) {
                int cps_limit = 0;
                unsigned long current_time = jiffies;
                unsigned long buffer_time = current_time +
                        (HZ * ch->ch_digi.digi_bufsize) / ch->ch_digi.digi_maxcps;

                if (ch->ch_cpstime < current_time) {
                        /* buffer is empty */
                        ch->ch_cpstime = current_time;      /* reset ch_cpstime */
                        cps_limit = ch->ch_digi.digi_bufsize;
                } else if (ch->ch_cpstime < buffer_time) {
                        /* still room in the buffer */
                        cps_limit = ((buffer_time - ch->ch_cpstime) * ch->ch_digi.digi_maxcps) / HZ;
                } else {
                        /* no room in the buffer */
                        cps_limit = 0;
                }

                bytes_available = min(cps_limit, bytes_available);
        }

        return bytes_available;
}


/*
 * dgnc_tty_write_room()
 *
 * Return space available in Tx buffer
 */
static int dgnc_tty_write_room(struct tty_struct *tty)
{
        struct channel_t *ch = NULL;
        struct un_t *un = NULL;
        ushort head;
        ushort tail;
        ushort tmask;
        int ret = 0;
        unsigned long flags;

        if (tty == NULL || dgnc_TmpWriteBuf == NULL)
                return 0;

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

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

        spin_lock_irqsave(&ch->ch_lock, flags);

        tmask = WQUEUEMASK;
        head = (ch->ch_w_head) & tmask;
        tail = (ch->ch_w_tail) & tmask;

        ret = tail - head - 1;
        if (ret < 0)
                ret += WQUEUESIZE;

        /* Limit printer to maxcps */
        ret = dgnc_maxcps_room(tty, ret);

        /*
         * If we are printer device, leave space for
         * possibly both the on and off strings.
         */
        if (un->un_type == DGNC_PRINT) {
                if (!(ch->ch_flags & CH_PRON))
                        ret -= ch->ch_digi.digi_onlen;
                ret -= ch->ch_digi.digi_offlen;
        } else {
                if (ch->ch_flags & CH_PRON)
                        ret -= ch->ch_digi.digi_offlen;
        }

        if (ret < 0)
                ret = 0;

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        return ret;
}


/*
 * dgnc_tty_put_char()
 *
 * Put a character into ch->ch_buf
 *
 *      - used by the line discipline for OPOST processing
 */
static int dgnc_tty_put_char(struct tty_struct *tty, unsigned char c)
{
        /*
         * Simply call tty_write.
         */
        dgnc_tty_write(tty, &c, 1);
        return 1;
}


/*
 * dgnc_tty_write()
 *
 * Take data from the user or kernel and send it out to the FEP.
 * In here exists all the Transparent Print magic as well.
 */
static int dgnc_tty_write(struct tty_struct *tty,
                const unsigned char *buf, int count)
{
        struct channel_t *ch = NULL;
        struct un_t *un = NULL;
        int bufcount = 0, n = 0;
        int orig_count = 0;
        unsigned long flags;
        ushort head;
        ushort tail;
        ushort tmask;
        uint remain;
        int from_user = 0;

        if (tty == NULL || dgnc_TmpWriteBuf == NULL)
                return 0;

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

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

        if (!count)
                return 0;

        /*
         * Store original amount of characters passed in.
         * This helps to figure out if we should ask the FEP
         * to send us an event when it has more space available.
         */
        orig_count = count;

        spin_lock_irqsave(&ch->ch_lock, flags);

        /* Get our space available for the channel from the board */
        tmask = WQUEUEMASK;
        head = (ch->ch_w_head) & tmask;
        tail = (ch->ch_w_tail) & tmask;

        bufcount = tail - head - 1;
        if (bufcount < 0)
                bufcount += WQUEUESIZE;

        /*
         * Limit printer output to maxcps overall, with bursts allowed
         * up to bufsize characters.
         */
        bufcount = dgnc_maxcps_room(tty, bufcount);

        /*
         * Take minimum of what the user wants to send, and the
         * space available in the FEP buffer.
         */
        count = min(count, bufcount);

        /*
         * Bail if no space left.
         */
        if (count <= 0)
                goto exit_retry;

        /*
         * Output the printer ON string, if we are in terminal mode, but
         * need to be in printer mode.
         */
        if ((un->un_type == DGNC_PRINT) && !(ch->ch_flags & CH_PRON)) {
                dgnc_wmove(ch, ch->ch_digi.digi_onstr,
                    (int) ch->ch_digi.digi_onlen);
                head = (ch->ch_w_head) & tmask;
                ch->ch_flags |= CH_PRON;
        }

        /*
         * On the other hand, output the printer OFF string, if we are
         * currently in printer mode, but need to output to the terminal.
         */
        if ((un->un_type != DGNC_PRINT) && (ch->ch_flags & CH_PRON)) {
                dgnc_wmove(ch, ch->ch_digi.digi_offstr,
                        (int) ch->ch_digi.digi_offlen);
                head = (ch->ch_w_head) & tmask;
                ch->ch_flags &= ~CH_PRON;
        }

        /*
         * If there is nothing left to copy, or I can't handle any more data, leave.
         */
        if (count <= 0)
                goto exit_retry;

        if (from_user) {

                count = min(count, WRITEBUFLEN);

                spin_unlock_irqrestore(&ch->ch_lock, flags);

                /*
                 * If data is coming from user space, copy it into a temporary
                 * buffer so we don't get swapped out while doing the copy to
                 * the board.
                 */
                /* we're allowed to block if it's from_user */
                if (down_interruptible(&dgnc_TmpWriteSem))
                        return -EINTR;

                /*
                 * copy_from_user() returns the number
                 * of bytes that could *NOT* be copied.
                 */
                count -= copy_from_user(dgnc_TmpWriteBuf, (const unsigned char __user *) buf, count);

                if (!count) {
                        up(&dgnc_TmpWriteSem);
                        return -EFAULT;
                }

                spin_lock_irqsave(&ch->ch_lock, flags);

                buf = dgnc_TmpWriteBuf;

        }

        n = count;

        /*
         * If the write wraps over the top of the circular buffer,
         * move the portion up to the wrap point, and reset the
         * pointers to the bottom.
         */
        remain = WQUEUESIZE - head;

        if (n >= remain) {
                n -= remain;
                memcpy(ch->ch_wqueue + head, buf, remain);
                head = 0;
                buf += remain;
        }

        if (n > 0) {
                /*
                 * Move rest of data.
                 */
                remain = n;
                memcpy(ch->ch_wqueue + head, buf, remain);
                head += remain;
        }

        if (count) {
                head &= tmask;
                ch->ch_w_head = head;
        }

        /* Update printer buffer empty time. */
        if ((un->un_type == DGNC_PRINT) && (ch->ch_digi.digi_maxcps > 0)
            && (ch->ch_digi.digi_bufsize > 0)) {
                ch->ch_cpstime += (HZ * count) / ch->ch_digi.digi_maxcps;
        }

        if (from_user) {
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                up(&dgnc_TmpWriteSem);
        } else {
                spin_unlock_irqrestore(&ch->ch_lock, flags);
        }

        if (count) {
                /*
                 * Channel lock is grabbed and then released
                 * inside this routine.
                 */
                ch->ch_bd->bd_ops->copy_data_from_queue_to_uart(ch);
        }

        return count;

exit_retry:

        spin_unlock_irqrestore(&ch->ch_lock, flags);
        return 0;
}


/*
 * Return modem signals to ld.
 */

static int dgnc_tty_tiocmget(struct tty_struct *tty)
{
        struct channel_t *ch;
        struct un_t *un;
        int result = -EIO;
        unsigned char mstat = 0;
        unsigned long flags;

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

        un = tty->driver_data;
        if (!un || un->magic != DGNC_UNIT_MAGIC)
                return result;

        ch = un->un_ch;
        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return result;

        spin_lock_irqsave(&ch->ch_lock, flags);

        mstat = (ch->ch_mostat | ch->ch_mistat);

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        result = 0;

        if (mstat & UART_MCR_DTR)
                result |= TIOCM_DTR;
        if (mstat & UART_MCR_RTS)
                result |= TIOCM_RTS;
        if (mstat & UART_MSR_CTS)
                result |= TIOCM_CTS;
        if (mstat & UART_MSR_DSR)
                result |= TIOCM_DSR;
        if (mstat & UART_MSR_RI)
                result |= TIOCM_RI;
        if (mstat & UART_MSR_DCD)
                result |= TIOCM_CD;

        return result;
}


/*
 * dgnc_tty_tiocmset()
 *
 * Set modem signals, called by ld.
 */

static int dgnc_tty_tiocmset(struct tty_struct *tty,
                unsigned int set, unsigned int clear)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        int ret = -EIO;
        unsigned long flags;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return ret;

        spin_lock_irqsave(&ch->ch_lock, flags);

        if (set & TIOCM_RTS)
                ch->ch_mostat |= UART_MCR_RTS;

        if (set & TIOCM_DTR)
                ch->ch_mostat |= UART_MCR_DTR;

        if (clear & TIOCM_RTS)
                ch->ch_mostat &= ~(UART_MCR_RTS);

        if (clear & TIOCM_DTR)
                ch->ch_mostat &= ~(UART_MCR_DTR);

        ch->ch_bd->bd_ops->assert_modem_signals(ch);

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        return 0;
}


/*
 * dgnc_tty_send_break()
 *
 * Send a Break, called by ld.
 */
static int dgnc_tty_send_break(struct tty_struct *tty, int msec)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        int ret = -EIO;
        unsigned long flags;

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

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

        ch = un->un_ch;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return ret;

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return ret;

        switch (msec) {
        case -1:
                msec = 0xFFFF;
                break;
        case 0:
                msec = 0;
                break;
        default:
                break;
        }

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_bd->bd_ops->send_break(ch, msec);

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        return 0;

}


/*
 * dgnc_tty_wait_until_sent()
 *
 * wait until data has been transmitted, called by ld.
 */
static void dgnc_tty_wait_until_sent(struct tty_struct *tty, int timeout)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        int rc;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return;

        rc = bd->bd_ops->drain(tty, 0);
}


/*
 * dgnc_send_xchar()
 *
 * send a high priority character, called by ld.
 */
static void dgnc_tty_send_xchar(struct tty_struct *tty, char c)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        unsigned long flags;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return;

        dev_dbg(tty->dev, "dgnc_tty_send_xchar start\n");

        spin_lock_irqsave(&ch->ch_lock, flags);
        bd->bd_ops->send_immediate_char(ch, c);
        spin_unlock_irqrestore(&ch->ch_lock, flags);

        dev_dbg(tty->dev, "dgnc_tty_send_xchar finish\n");
}




/*
 * Return modem signals to ld.
 */
static inline int dgnc_get_mstat(struct channel_t *ch)
{
        unsigned char mstat;
        int result = -EIO;
        unsigned long flags;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return -ENXIO;

        spin_lock_irqsave(&ch->ch_lock, flags);

        mstat = (ch->ch_mostat | ch->ch_mistat);

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        result = 0;

        if (mstat & UART_MCR_DTR)
                result |= TIOCM_DTR;
        if (mstat & UART_MCR_RTS)
                result |= TIOCM_RTS;
        if (mstat & UART_MSR_CTS)
                result |= TIOCM_CTS;
        if (mstat & UART_MSR_DSR)
                result |= TIOCM_DSR;
        if (mstat & UART_MSR_RI)
                result |= TIOCM_RI;
        if (mstat & UART_MSR_DCD)
                result |= TIOCM_CD;

        return result;
}



/*
 * Return modem signals to ld.
 */
static int dgnc_get_modem_info(struct channel_t *ch, unsigned int  __user *value)
{
        int result;

        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return -ENXIO;

        result = dgnc_get_mstat(ch);

        if (result < 0)
                return -ENXIO;

        return put_user(result, value);
}


/*
 * dgnc_set_modem_info()
 *
 * Set modem signals, called by ld.
 */
static int dgnc_set_modem_info(struct tty_struct *tty, unsigned int command, unsigned int __user *value)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        int ret = -ENXIO;
        unsigned int arg = 0;
        unsigned long flags;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return ret;

        ret = get_user(arg, value);
        if (ret)
                return ret;

        switch (command) {
        case TIOCMBIS:
                if (arg & TIOCM_RTS)
                        ch->ch_mostat |= UART_MCR_RTS;

                if (arg & TIOCM_DTR)
                        ch->ch_mostat |= UART_MCR_DTR;

                break;

        case TIOCMBIC:
                if (arg & TIOCM_RTS)
                        ch->ch_mostat &= ~(UART_MCR_RTS);

                if (arg & TIOCM_DTR)
                        ch->ch_mostat &= ~(UART_MCR_DTR);

                break;

        case TIOCMSET:

                if (arg & TIOCM_RTS)
                        ch->ch_mostat |= UART_MCR_RTS;
                else
                        ch->ch_mostat &= ~(UART_MCR_RTS);

                if (arg & TIOCM_DTR)
                        ch->ch_mostat |= UART_MCR_DTR;
                else
                        ch->ch_mostat &= ~(UART_MCR_DTR);

                break;

        default:
                return -EINVAL;
        }

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_bd->bd_ops->assert_modem_signals(ch);

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        return 0;
}


/*
 * dgnc_tty_digigeta()
 *
 * Ioctl to get the information for ditty.
 *
 *
 *
 */
static int dgnc_tty_digigeta(struct tty_struct *tty, struct digi_t __user *retinfo)
{
        struct channel_t *ch;
        struct un_t *un;
        struct digi_t tmp;
        unsigned long flags;

        if (!retinfo)
                return -EFAULT;

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

        un = tty->driver_data;
        if (!un || un->magic != DGNC_UNIT_MAGIC)
                return -EFAULT;

        ch = un->un_ch;
        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return -EFAULT;

        memset(&tmp, 0, sizeof(tmp));

        spin_lock_irqsave(&ch->ch_lock, flags);
        memcpy(&tmp, &ch->ch_digi, sizeof(tmp));
        spin_unlock_irqrestore(&ch->ch_lock, flags);

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

        return 0;
}


/*
 * dgnc_tty_digiseta()
 *
 * Ioctl to set the information for ditty.
 *
 *
 *
 */
static int dgnc_tty_digiseta(struct tty_struct *tty, struct digi_t __user *new_info)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        struct digi_t new_digi;
        unsigned long flags;

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

        un = tty->driver_data;
        if (!un || un->magic != DGNC_UNIT_MAGIC)
                return -EFAULT;

        ch = un->un_ch;
        if (!ch || ch->magic != DGNC_CHANNEL_MAGIC)
                return -EFAULT;

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return -EFAULT;

        if (copy_from_user(&new_digi, new_info, sizeof(new_digi)))
                return -EFAULT;

        spin_lock_irqsave(&ch->ch_lock, flags);

        /*
         * Handle transistions to and from RTS Toggle.
         */
        if (!(ch->ch_digi.digi_flags & DIGI_RTS_TOGGLE) && (new_digi.digi_flags & DIGI_RTS_TOGGLE))
                ch->ch_mostat &= ~(UART_MCR_RTS);
        if ((ch->ch_digi.digi_flags & DIGI_RTS_TOGGLE) && !(new_digi.digi_flags & DIGI_RTS_TOGGLE))
                ch->ch_mostat |= (UART_MCR_RTS);

        /*
         * Handle transistions to and from DTR Toggle.
         */
        if (!(ch->ch_digi.digi_flags & DIGI_DTR_TOGGLE) && (new_digi.digi_flags & DIGI_DTR_TOGGLE))
                ch->ch_mostat &= ~(UART_MCR_DTR);
        if ((ch->ch_digi.digi_flags & DIGI_DTR_TOGGLE) && !(new_digi.digi_flags & DIGI_DTR_TOGGLE))
                ch->ch_mostat |= (UART_MCR_DTR);

        memcpy(&ch->ch_digi, &new_digi, sizeof(new_digi));

        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;

        ch->ch_bd->bd_ops->param(tty);

        spin_unlock_irqrestore(&ch->ch_lock, flags);

        return 0;
}


/*
 * dgnc_set_termios()
 */
static void dgnc_tty_set_termios(struct tty_struct *tty, struct ktermios *old_termios)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        unsigned long flags;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return;

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_c_cflag   = tty->termios.c_cflag;
        ch->ch_c_iflag   = tty->termios.c_iflag;
        ch->ch_c_oflag   = tty->termios.c_oflag;
        ch->ch_c_lflag   = tty->termios.c_lflag;
        ch->ch_startc = tty->termios.c_cc[VSTART];
        ch->ch_stopc  = tty->termios.c_cc[VSTOP];

        ch->ch_bd->bd_ops->param(tty);
        dgnc_carrier(ch);

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}


static void dgnc_tty_throttle(struct tty_struct *tty)
{
        struct channel_t *ch;
        struct un_t *un;
        unsigned long flags;

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

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

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

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_flags |= (CH_FORCED_STOPI);

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}


static void dgnc_tty_unthrottle(struct tty_struct *tty)
{
        struct channel_t *ch;
        struct un_t *un;
        unsigned long flags;

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

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

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

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_flags &= ~(CH_FORCED_STOPI);

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}


static void dgnc_tty_start(struct tty_struct *tty)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        unsigned long flags;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return;

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_flags &= ~(CH_FORCED_STOP);

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}


static void dgnc_tty_stop(struct tty_struct *tty)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        unsigned long flags;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return;

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_flags |= (CH_FORCED_STOP);

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}


/*
 * dgnc_tty_flush_chars()
 *
 * Flush the cook buffer
 *
 * Note to self, and any other poor souls who venture here:
 *
 * flush in this case DOES NOT mean dispose of the data.
 * instead, it means "stop buffering and send it if you
 * haven't already."  Just guess how I figured that out...   SRW 2-Jun-98
 *
 * It is also always called in interrupt context - JAR 8-Sept-99
 */
static void dgnc_tty_flush_chars(struct tty_struct *tty)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        unsigned long flags;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return;

        spin_lock_irqsave(&ch->ch_lock, flags);

        /* Do something maybe here */

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}



/*
 * dgnc_tty_flush_buffer()
 *
 * Flush Tx buffer (make in == out)
 */
static void dgnc_tty_flush_buffer(struct tty_struct *tty)
{
        struct channel_t *ch;
        struct un_t *un;
        unsigned long flags;

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

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

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

        spin_lock_irqsave(&ch->ch_lock, flags);

        ch->ch_flags &= ~CH_STOP;

        /* Flush our write queue */
        ch->ch_w_head = ch->ch_w_tail;

        /* Flush UARTs transmit FIFO */
        ch->ch_bd->bd_ops->flush_uart_write(ch);

        if (ch->ch_tun.un_flags & (UN_LOW|UN_EMPTY)) {
                ch->ch_tun.un_flags &= ~(UN_LOW|UN_EMPTY);
                wake_up_interruptible(&ch->ch_tun.un_flags_wait);
        }
        if (ch->ch_pun.un_flags & (UN_LOW|UN_EMPTY)) {
                ch->ch_pun.un_flags &= ~(UN_LOW|UN_EMPTY);
                wake_up_interruptible(&ch->ch_pun.un_flags_wait);
        }

        spin_unlock_irqrestore(&ch->ch_lock, flags);
}



/*****************************************************************************
 *
 * The IOCTL function and all of its helpers
 *
 *****************************************************************************/

/*
 * dgnc_tty_ioctl()
 *
 * The usual assortment of ioctl's
 */
static int dgnc_tty_ioctl(struct tty_struct *tty, unsigned int cmd,
                unsigned long arg)
{
        struct dgnc_board *bd;
        struct channel_t *ch;
        struct un_t *un;
        int rc;
        unsigned long flags;
        void __user *uarg = (void __user *) arg;

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

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

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

        bd = ch->ch_bd;
        if (!bd || bd->magic != DGNC_BOARD_MAGIC)
                return -ENODEV;

        spin_lock_irqsave(&ch->ch_lock, flags);

        if (un->un_open_count <= 0) {
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return -EIO;
        }

        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 so we'll ask for something
                 * in the middle: 0.375 seconds.
                 */
                rc = tty_check_change(tty);
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                if (rc)
                        return rc;

                rc = ch->ch_bd->bd_ops->drain(tty, 0);

                if (rc)
                        return -EINTR;

                spin_lock_irqsave(&ch->ch_lock, flags);

                if (((cmd == TCSBRK) && (!arg)) || (cmd == TCSBRKP))
                        ch->ch_bd->bd_ops->send_break(ch, 250);

                spin_unlock_irqrestore(&ch->ch_lock, flags);

                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);
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                if (rc)
                        return rc;

                rc = ch->ch_bd->bd_ops->drain(tty, 0);
                if (rc)
                        return -EINTR;

                spin_lock_irqsave(&ch->ch_lock, flags);

                ch->ch_bd->bd_ops->send_break(ch, 250);

                spin_unlock_irqrestore(&ch->ch_lock, flags);

                return 0;

        case TIOCSBRK:
                rc = tty_check_change(tty);
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                if (rc)
                        return rc;

                rc = ch->ch_bd->bd_ops->drain(tty, 0);
                if (rc)
                        return -EINTR;

                spin_lock_irqsave(&ch->ch_lock, flags);

                ch->ch_bd->bd_ops->send_break(ch, 250);

                spin_unlock_irqrestore(&ch->ch_lock, flags);

                return 0;

        case TIOCCBRK:
                /* Do Nothing */
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return 0;

        case TIOCGSOFTCAR:

                spin_unlock_irqrestore(&ch->ch_lock, flags);

                rc = put_user(C_CLOCAL(tty) ? 1 : 0, (unsigned long __user *) arg);
                return rc;

        case TIOCSSOFTCAR:

                spin_unlock_irqrestore(&ch->ch_lock, flags);
                rc = get_user(arg, (unsigned long __user *) arg);
                if (rc)
                        return rc;

                spin_lock_irqsave(&ch->ch_lock, flags);
                tty->termios.c_cflag = ((tty->termios.c_cflag & ~CLOCAL) | (arg ? CLOCAL : 0));
                ch->ch_bd->bd_ops->param(tty);
                spin_unlock_irqrestore(&ch->ch_lock, flags);

                return 0;

        case TIOCMGET:
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return dgnc_get_modem_info(ch, uarg);

        case TIOCMBIS:
        case TIOCMBIC:
        case TIOCMSET:
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return dgnc_set_modem_info(tty, cmd, uarg);

                /*
                 * 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) {
                        spin_unlock_irqrestore(&ch->ch_lock, flags);
                        return rc;
                }

                if ((arg == TCIFLUSH) || (arg == TCIOFLUSH)) {
                        ch->ch_r_head = ch->ch_r_tail;
                        ch->ch_bd->bd_ops->flush_uart_read(ch);
                        /* Force queue flow control to be released, if needed */
                        dgnc_check_queue_flow_control(ch);
                }

                if ((arg == TCOFLUSH) || (arg == TCIOFLUSH)) {
                        if (!(un->un_type == DGNC_PRINT)) {
                                ch->ch_w_head = ch->ch_w_tail;
                                ch->ch_bd->bd_ops->flush_uart_write(ch);

                                if (ch->ch_tun.un_flags & (UN_LOW|UN_EMPTY)) {
                                        ch->ch_tun.un_flags &= ~(UN_LOW|UN_EMPTY);
                                        wake_up_interruptible(&ch->ch_tun.un_flags_wait);
                                }

                                if (ch->ch_pun.un_flags & (UN_LOW|UN_EMPTY)) {
                                        ch->ch_pun.un_flags &= ~(UN_LOW|UN_EMPTY);
                                        wake_up_interruptible(&ch->ch_pun.un_flags_wait);
                                }

                        }
                }

                /* pretend we didn't recognize this IOCTL */
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return -ENOIOCTLCMD;
        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.
                 */
                if (cmd == TCSETSF) {
                        /* flush rx */
                        ch->ch_flags &= ~CH_STOP;
                        ch->ch_r_head = ch->ch_r_tail;
                        ch->ch_bd->bd_ops->flush_uart_read(ch);
                        /* Force queue flow control to be released, if needed */
                        dgnc_check_queue_flow_control(ch);
                }

                /* now wait for all the output to drain */
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                rc = ch->ch_bd->bd_ops->drain(tty, 0);
                if (rc)
                        return -EINTR;

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

        case TCSETAW:

                spin_unlock_irqrestore(&ch->ch_lock, flags);
                rc = ch->ch_bd->bd_ops->drain(tty, 0);
                if (rc)
                        return -EINTR;

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

        case TCXONC:
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                /* Make the ld do it */
                return -ENOIOCTLCMD;

        case DIGI_GETA:
                /* get information for ditty */
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return dgnc_tty_digigeta(tty, uarg);

        case DIGI_SETAW:
        case DIGI_SETAF:

                /* set information for ditty */
                if (cmd == (DIGI_SETAW)) {

                        spin_unlock_irqrestore(&ch->ch_lock, flags);
                        rc = ch->ch_bd->bd_ops->drain(tty, 0);

                        if (rc)
                                return -EINTR;

                        spin_lock_irqsave(&ch->ch_lock, flags);
                } else {
                        tty_ldisc_flush(tty);
                }
                /* fall thru */

        case DIGI_SETA:
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return dgnc_tty_digiseta(tty, uarg);

        case DIGI_LOOPBACK:
                {
                        uint loopback = 0;
                        /* Let go of locks when accessing user space, could sleep */
                        spin_unlock_irqrestore(&ch->ch_lock, flags);
                        rc = get_user(loopback, (unsigned int __user *) arg);
                        if (rc)
                                return rc;
                        spin_lock_irqsave(&ch->ch_lock, flags);

                        /* Enable/disable internal loopback for this port */
                        if (loopback)
                                ch->ch_flags |= CH_LOOPBACK;
                        else
                                ch->ch_flags &= ~(CH_LOOPBACK);

                        ch->ch_bd->bd_ops->param(tty);
                        spin_unlock_irqrestore(&ch->ch_lock, flags);
                        return 0;
                }

        case DIGI_GETCUSTOMBAUD:
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                rc = put_user(ch->ch_custom_speed, (unsigned int __user *) arg);
                return rc;

        case DIGI_SETCUSTOMBAUD:
        {
                int new_rate;
                /* Let go of locks when accessing user space, could sleep */
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                rc = get_user(new_rate, (int __user *) arg);
                if (rc)
                        return rc;
                spin_lock_irqsave(&ch->ch_lock, flags);
                dgnc_set_custom_speed(ch, new_rate);
                ch->ch_bd->bd_ops->param(tty);
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return 0;
        }

        /*
         * This ioctl allows insertion of a character into the front
         * of any pending data to be transmitted.
         *
         * This ioctl is to satify the "Send Character Immediate"
         * call that the RealPort protocol spec requires.
         */
        case DIGI_REALPORT_SENDIMMEDIATE:
        {
                unsigned char c;

                spin_unlock_irqrestore(&ch->ch_lock, flags);
                rc = get_user(c, (unsigned char __user *) arg);
                if (rc)
                        return rc;
                spin_lock_irqsave(&ch->ch_lock, flags);
                ch->ch_bd->bd_ops->send_immediate_char(ch, c);
                spin_unlock_irqrestore(&ch->ch_lock, flags);
                return 0;
        }

        /*
         * This ioctl returns all the current counts for the port.
         *
         * This ioctl is to satify the "Line Error Counters"
         * call that the RealPort protocol spec requires.
         */
        case DIGI_REALPORT_GETCOUNTERS:
        {
                struct digi_getcounter buf;

                buf.norun = ch->ch_err_overrun;
                buf.noflow = 0;         /* The driver doesn't keep this stat */
                buf.nframe = ch->ch_err_frame;
                buf.nparity = ch->ch_err_parity;
                buf.nbreak = ch->ch_err_break;
                buf.rbytes = ch->ch_rxcount;
                buf.tbytes = ch->ch_txcount;

                spin_unlock_irqrestore(&ch->ch_lock, flags);

                if (copy_to_user(uarg, &buf, sizeof(buf)))
                        return -EFAULT;

                return 0;
        }

        /*
         * This ioctl returns all current events.
         *
         * This ioctl is to satify the "Event Reporting"
         * call that the RealPort protocol spec requires.
         */
        case DIGI_REALPORT_GETEVENTS:
        {
                unsigned int events = 0;

                /* NOTE: MORE EVENTS NEEDS TO BE ADDED HERE */
                if (ch->ch_flags & CH_BREAK_SENDING)
                        events |= EV_TXB;
                if ((ch->ch_flags & CH_STOP) || (ch->ch_flags & CH_FORCED_STOP))
                        events |= (EV_OPU | EV_OPS);

                if ((ch->ch_flags & CH_STOPI) || (ch->ch_flags & CH_FORCED_STOPI))
                        events |= (EV_IPU | EV_IPS);

                spin_unlock_irqrestore(&ch->ch_lock, flags);
                rc = put_user(events, (unsigned int __user *) arg);
                return rc;
        }

        /*
         * This ioctl returns TOUT and TIN counters based
         * upon the values passed in by the RealPort Server.
         * It also passes back whether the UART Transmitter is
         * empty as well.
         */
        case DIGI_REALPORT_GETBUFFERS:
        {
                struct digi_getbuffer buf;
                int tdist;
                int count;

                spin_unlock_irqrestore(&ch->ch_lock, flags);

                /*
                 * Get data from user first.
                 */
                if (copy_from_user(&buf, uarg, sizeof(buf)))
                        return -EFAULT;

                spin_lock_irqsave(&ch->ch_lock, flags);

                /*
                 * Figure out how much data is in our RX and TX queues.
                 */
                buf.rxbuf = (ch->ch_r_head - ch->ch_r_tail) & RQUEUEMASK;
                buf.txbuf = (ch->ch_w_head - ch->ch_w_tail) & WQUEUEMASK;

                /*
                 * Is the UART empty? Add that value to whats in our TX queue.
                 */
                count = buf.txbuf + ch->ch_bd->bd_ops->get_uart_bytes_left(ch);

                /*
                 * Figure out how much data the RealPort Server believes should
                 * be in our TX queue.
                 */
                tdist = (buf.tIn - buf.tOut) & 0xffff;

                /*
                 * If we have more data than the RealPort Server believes we
                 * should have, reduce our count to its amount.
                 *
                 * This count difference CAN happen because the Linux LD can
                 * insert more characters into our queue for OPOST processing
                 * that the RealPort Server doesn't know about.
                 */
                if (buf.txbuf > tdist)
                        buf.txbuf = tdist;

                /*
                 * Report whether our queue and UART TX are completely empty.
                 */
                if (count)
                        buf.txdone = 0;
                else
                        buf.txdone = 1;

                spin_unlock_irqrestore(&ch->ch_lock, flags);

                if (copy_to_user(uarg, &buf, sizeof(buf)))
                        return -EFAULT;

                return 0;
        }
        default:
                spin_unlock_irqrestore(&ch->ch_lock, flags);

                return -ENOIOCTLCMD;
        }
}