[PATCH] s390: fix in-user atomic futex operation.

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

/*
 *  generic_serial.c
 *
 *  Copyright (C) 1998/1999 R.E.Wolff@BitWizard.nl
 *
 *  written for the SX serial driver.
 *     Contains the code that should be shared over all the serial drivers.
 *
 *  Credit for the idea to do it this way might go to Alan Cox. 
 *
 *
 *  Version 0.1 -- December, 1998. Initial version.
 *  Version 0.2 -- March, 1999.    Some more routines. Bugfixes. Etc.
 *  Version 0.5 -- August, 1999.   Some more fixes. Reformat for Linus.
 *
 *  BitWizard is actively maintaining this file. We sometimes find
 *  that someone submitted changes to this file. We really appreciate
 *  your help, but please submit changes through us. We're doing our
 *  best to be responsive.  -- REW
 * */

#include <linux/module.h>
#include <linux/kernel.h>
#include <linux/tty.h>
#include <linux/serial.h>
#include <linux/mm.h>
#include <linux/generic_serial.h>
#include <linux/interrupt.h>
#include <linux/tty_flip.h>
#include <linux/delay.h>
#include <asm/semaphore.h>
#include <asm/uaccess.h>

#define DEBUG 

static char *                  tmp_buf; 

static int gs_debug;

#ifdef DEBUG
#define gs_dprintk(f, str...) if (gs_debug & f) printk (str)
#else
#define gs_dprintk(f, str...) /* nothing */
#endif

#define func_enter() gs_dprintk (GS_DEBUG_FLOW, "gs: enter %s\n", __FUNCTION__)
#define func_exit()  gs_dprintk (GS_DEBUG_FLOW, "gs: exit  %s\n", __FUNCTION__)
#define NEW_WRITE_LOCKING 1
#if NEW_WRITE_LOCKING
#define DECL      /* Nothing */
#define LOCKIT    mutex_lock(& port->port_write_mutex);
#define RELEASEIT mutex_unlock(&port->port_write_mutex);
#else
#define DECL      unsigned long flags;
#define LOCKIT    save_flags (flags);cli ()
#define RELEASEIT restore_flags (flags)
#endif

#define RS_EVENT_WRITE_WAKEUP   1

module_param(gs_debug, int, 0644);


void gs_put_char(struct tty_struct * tty, unsigned char ch)
{
        struct gs_port *port;
        DECL

        func_enter (); 

        if (!tty) return;

        port = tty->driver_data;

        if (!port) return;

        if (! (port->flags & ASYNC_INITIALIZED)) return;

        /* Take a lock on the serial tranmit buffer! */
        LOCKIT;

        if (port->xmit_cnt >= SERIAL_XMIT_SIZE - 1) {
                /* Sorry, buffer is full, drop character. Update statistics???? -- REW */
                RELEASEIT;
                return;
        }

        port->xmit_buf[port->xmit_head++] = ch;
        port->xmit_head &= SERIAL_XMIT_SIZE - 1;
        port->xmit_cnt++;  /* Characters in buffer */

        RELEASEIT;
        func_exit ();
}


#ifdef NEW_WRITE_LOCKING

/*
> Problems to take into account are:
>       -1- Interrupts that empty part of the buffer.
>       -2- page faults on the access to userspace. 
>       -3- Other processes that are also trying to do a "write". 
*/

int gs_write(struct tty_struct * tty, 
                    const unsigned char *buf, int count)
{
        struct gs_port *port;
        int c, total = 0;
        int t;

        func_enter ();

        if (!tty) return 0;

        port = tty->driver_data;

        if (!port) return 0;

        if (! (port->flags & ASYNC_INITIALIZED))
                return 0;

        /* get exclusive "write" access to this port (problem 3) */
        /* This is not a spinlock because we can have a disk access (page 
                 fault) in copy_from_user */
        mutex_lock(& port->port_write_mutex);

        while (1) {

                c = count;
 
                /* This is safe because we "OWN" the "head". Noone else can 
                   change the "head": we own the port_write_mutex. */
                /* Don't overrun the end of the buffer */
                t = SERIAL_XMIT_SIZE - port->xmit_head;
                if (t < c) c = t;
 
                /* This is safe because the xmit_cnt can only decrease. This 
                   would increase "t", so we might copy too little chars. */
                /* Don't copy past the "head" of the buffer */
                t = SERIAL_XMIT_SIZE - 1 - port->xmit_cnt;
                if (t < c) c = t;
 
                /* Can't copy more? break out! */
                if (c <= 0) break;

                memcpy (port->xmit_buf + port->xmit_head, buf, c);

                port -> xmit_cnt += c;
                port -> xmit_head = (port->xmit_head + c) & (SERIAL_XMIT_SIZE -1);
                buf += c;
                count -= c;
                total += c;
        }
        mutex_unlock(& port->port_write_mutex);

        gs_dprintk (GS_DEBUG_WRITE, "write: interrupts are %s\n", 
                    (port->flags & GS_TX_INTEN)?"enabled": "disabled"); 

        if (port->xmit_cnt && 
            !tty->stopped && 
            !tty->hw_stopped &&
            !(port->flags & GS_TX_INTEN)) {
                port->flags |= GS_TX_INTEN;
                port->rd->enable_tx_interrupts (port);
        }
        func_exit ();
        return total;
}
#else
/*
> Problems to take into account are:
>       -1- Interrupts that empty part of the buffer.
>       -2- page faults on the access to userspace. 
>       -3- Other processes that are also trying to do a "write". 
*/

int gs_write(struct tty_struct * tty,
                    const unsigned char *buf, int count)
{
        struct gs_port *port;
        int c, total = 0;
        int t;
        unsigned long flags;

        func_enter ();

        /* The standard serial driver returns 0 in this case. 
           That sounds to me as "No error, I just didn't get to writing any
           bytes. Feel free to try again." 
           The "official" way to write n bytes from buf is:

                 for (nwritten = 0;nwritten < n;nwritten += rv) {
                         rv = write (fd, buf+nwritten, n-nwritten);
                         if (rv < 0) break; // Error: bail out. //
                 } 

           which will loop endlessly in this case. The manual page for write
           agrees with me. In practise almost everybody writes 
           "write (fd, buf,n);" but some people might have had to deal with 
           incomplete writes in the past and correctly implemented it by now... 
         */

        if (!tty) return -EIO;

        port = tty->driver_data;
        if (!port || !port->xmit_buf || !tmp_buf)
                return -EIO;

        local_save_flags(flags);
        while (1) {
                cli();
                c = count;

                /* This is safe because we "OWN" the "head". Noone else can 
                   change the "head": we own the port_write_mutex. */
                /* Don't overrun the end of the buffer */
                t = SERIAL_XMIT_SIZE - port->xmit_head;
                if (t < c) c = t;

                /* This is safe because the xmit_cnt can only decrease. This 
                   would increase "t", so we might copy too little chars. */
                /* Don't copy past the "head" of the buffer */
                t = SERIAL_XMIT_SIZE - 1 - port->xmit_cnt;
                if (t < c) c = t;

                /* Can't copy more? break out! */
                if (c <= 0) {
                        local_restore_flags(flags);
                        break;
                }
                memcpy(port->xmit_buf + port->xmit_head, buf, c);
                port->xmit_head = ((port->xmit_head + c) &
                                   (SERIAL_XMIT_SIZE-1));
                port->xmit_cnt += c;
                local_restore_flags(flags);
                buf += c;
                count -= c;
                total += c;
        }

        if (port->xmit_cnt && 
            !tty->stopped && 
            !tty->hw_stopped &&
            !(port->flags & GS_TX_INTEN)) {
                port->flags |= GS_TX_INTEN;
                port->rd->enable_tx_interrupts (port);
        }
        func_exit ();
        return total;
}

#endif



int gs_write_room(struct tty_struct * tty)
{
        struct gs_port *port = tty->driver_data;
        int ret;

        func_enter ();
        ret = SERIAL_XMIT_SIZE - port->xmit_cnt - 1;
        if (ret < 0)
                ret = 0;
        func_exit ();
        return ret;
}


int gs_chars_in_buffer(struct tty_struct *tty)
{
        struct gs_port *port = tty->driver_data;
        func_enter ();

        func_exit ();
        return port->xmit_cnt;
}


static int gs_real_chars_in_buffer(struct tty_struct *tty)
{
        struct gs_port *port;
        func_enter ();

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

        if (!port->rd) return 0;
        if (!port->rd->chars_in_buffer) return 0;

        func_exit ();
        return port->xmit_cnt + port->rd->chars_in_buffer (port);
}


static int gs_wait_tx_flushed (void * ptr, unsigned long timeout) 
{
        struct gs_port *port = ptr;
        unsigned long end_jiffies;
        int jiffies_to_transmit, charsleft = 0, rv = 0;
        int rcib;

        func_enter();

        gs_dprintk (GS_DEBUG_FLUSH, "port=%p.\n", port);
        if (port) {
                gs_dprintk (GS_DEBUG_FLUSH, "xmit_cnt=%x, xmit_buf=%p, tty=%p.\n", 
                port->xmit_cnt, port->xmit_buf, port->tty);
        }

        if (!port || port->xmit_cnt < 0 || !port->xmit_buf) {
                gs_dprintk (GS_DEBUG_FLUSH, "ERROR: !port, !port->xmit_buf or prot->xmit_cnt < 0.\n");
                func_exit();
                return -EINVAL;  /* This is an error which we don't know how to handle. */
        }

        rcib = gs_real_chars_in_buffer(port->tty);

        if(rcib <= 0) {
                gs_dprintk (GS_DEBUG_FLUSH, "nothing to wait for.\n");
                func_exit();
                return rv;
        }
        /* stop trying: now + twice the time it would normally take +  seconds */
        if (timeout == 0) timeout = MAX_SCHEDULE_TIMEOUT;
        end_jiffies  = jiffies; 
        if (timeout !=  MAX_SCHEDULE_TIMEOUT)
                end_jiffies += port->baud?(2 * rcib * 10 * HZ / port->baud):0;
        end_jiffies += timeout;

        gs_dprintk (GS_DEBUG_FLUSH, "now=%lx, end=%lx (%ld).\n", 
                    jiffies, end_jiffies, end_jiffies-jiffies); 

        /* the expression is actually jiffies < end_jiffies, but that won't
           work around the wraparound. Tricky eh? */
        while ((charsleft = gs_real_chars_in_buffer (port->tty)) &&
                time_after (end_jiffies, jiffies)) {
                /* Units check: 
                   chars * (bits/char) * (jiffies /sec) / (bits/sec) = jiffies!
                   check! */

                charsleft += 16; /* Allow 16 chars more to be transmitted ... */
                jiffies_to_transmit = port->baud?(1 + charsleft * 10 * HZ / port->baud):0;
                /*                                ^^^ Round up.... */
                if (jiffies_to_transmit <= 0) jiffies_to_transmit = 1;

                gs_dprintk (GS_DEBUG_FLUSH, "Expect to finish in %d jiffies "
                            "(%d chars).\n", jiffies_to_transmit, charsleft); 

                msleep_interruptible(jiffies_to_msecs(jiffies_to_transmit));
                if (signal_pending (current)) {
                        gs_dprintk (GS_DEBUG_FLUSH, "Signal pending. Bombing out: "); 
                        rv = -EINTR;
                        break;
                }
        }

        gs_dprintk (GS_DEBUG_FLUSH, "charsleft = %d.\n", charsleft); 
        set_current_state (TASK_RUNNING);

        func_exit();
        return rv;
}



void gs_flush_buffer(struct tty_struct *tty)
{
        struct gs_port *port;
        unsigned long flags;

        func_enter ();

        if (!tty) return;

        port = tty->driver_data;

        if (!port) return;

        /* XXX Would the write semaphore do? */
        spin_lock_irqsave (&port->driver_lock, flags);
        port->xmit_cnt = port->xmit_head = port->xmit_tail = 0;
        spin_unlock_irqrestore (&port->driver_lock, flags);

        wake_up_interruptible(&tty->write_wait);
        tty_wakeup(tty);
        func_exit ();
}


void gs_flush_chars(struct tty_struct * tty)
{
        struct gs_port *port;

        func_enter ();

        if (!tty) return;

        port = tty->driver_data;

        if (!port) return;

        if (port->xmit_cnt <= 0 || tty->stopped || tty->hw_stopped ||
            !port->xmit_buf) {
                func_exit ();
                return;
        }

        /* Beats me -- REW */
        port->flags |= GS_TX_INTEN;
        port->rd->enable_tx_interrupts (port);
        func_exit ();
}


void gs_stop(struct tty_struct * tty)
{
        struct gs_port *port;

        func_enter ();

        if (!tty) return;

        port = tty->driver_data;

        if (!port) return;

        if (port->xmit_cnt && 
            port->xmit_buf && 
            (port->flags & GS_TX_INTEN) ) {
                port->flags &= ~GS_TX_INTEN;
                port->rd->disable_tx_interrupts (port);
        }
        func_exit ();
}


void gs_start(struct tty_struct * tty)
{
        struct gs_port *port;

        if (!tty) return;

        port = tty->driver_data;

        if (!port) return;

        if (port->xmit_cnt && 
            port->xmit_buf && 
            !(port->flags & GS_TX_INTEN) ) {
                port->flags |= GS_TX_INTEN;
                port->rd->enable_tx_interrupts (port);
        }
        func_exit ();
}


static void gs_shutdown_port (struct gs_port *port)
{
        unsigned long flags;

        func_enter();
        
        if (!port) return;
        
        if (!(port->flags & ASYNC_INITIALIZED))
                return;

        spin_lock_irqsave(&port->driver_lock, flags);

        if (port->xmit_buf) {
                free_page((unsigned long) port->xmit_buf);
                port->xmit_buf = NULL;
        }

        if (port->tty)
                set_bit(TTY_IO_ERROR, &port->tty->flags);

        port->rd->shutdown_port (port);

        port->flags &= ~ASYNC_INITIALIZED;
        spin_unlock_irqrestore(&port->driver_lock, flags);

        func_exit();
}


void gs_hangup(struct tty_struct *tty)
{
        struct gs_port   *port;

        func_enter ();

        if (!tty) return;

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

        gs_shutdown_port (port);
        port->flags &= ~(ASYNC_NORMAL_ACTIVE|GS_ACTIVE);
        port->tty = NULL;
        port->count = 0;

        wake_up_interruptible(&port->open_wait);
        func_exit ();
}


int gs_block_til_ready(void *port_, struct file * filp)
{
        struct gs_port *port = port_;
        DECLARE_WAITQUEUE(wait, current);
        int    retval;
        int    do_clocal = 0;
        int    CD;
        struct tty_struct *tty;
        unsigned long flags;

        func_enter ();

        if (!port) return 0;

        tty = port->tty;

        if (!tty) return 0;

        gs_dprintk (GS_DEBUG_BTR, "Entering gs_block_till_ready.\n"); 
        /*
         * If the device is in the middle of being closed, then block
         * until it's done, and then try again.
         */
        if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
                interruptible_sleep_on(&port->close_wait);
                if (port->flags & ASYNC_HUP_NOTIFY)
                        return -EAGAIN;
                else
                        return -ERESTARTSYS;
        }

        gs_dprintk (GS_DEBUG_BTR, "after hung up\n"); 

        /*
         * If non-blocking mode is set, or the port is not enabled,
         * then make the check up front and then exit.
         */
        if ((filp->f_flags & O_NONBLOCK) ||
            (tty->flags & (1 << TTY_IO_ERROR))) {
                port->flags |= ASYNC_NORMAL_ACTIVE;
                return 0;
        }

        gs_dprintk (GS_DEBUG_BTR, "after nonblock\n"); 
 
        if (C_CLOCAL(tty))
                do_clocal = 1;

        /*
         * Block waiting for the carrier detect and the line to become
         * free (i.e., not in use by the callout).  While we are in
         * this loop, port->count is dropped by one, so that
         * rs_close() knows when to free things.  We restore it upon
         * exit, either normal or abnormal.
         */
        retval = 0;

        add_wait_queue(&port->open_wait, &wait);

        gs_dprintk (GS_DEBUG_BTR, "after add waitq.\n"); 
        spin_lock_irqsave(&port->driver_lock, flags);
        if (!tty_hung_up_p(filp)) {
                port->count--;
        }
        spin_unlock_irqrestore(&port->driver_lock, flags);
        port->blocked_open++;
        while (1) {
                CD = port->rd->get_CD (port);
                gs_dprintk (GS_DEBUG_BTR, "CD is now %d.\n", CD);
                set_current_state (TASK_INTERRUPTIBLE);
                if (tty_hung_up_p(filp) ||
                    !(port->flags & ASYNC_INITIALIZED)) {
                        if (port->flags & ASYNC_HUP_NOTIFY)
                                retval = -EAGAIN;
                        else
                                retval = -ERESTARTSYS;
                        break;
                }
                if (!(port->flags & ASYNC_CLOSING) &&
                    (do_clocal || CD))
                        break;
                gs_dprintk (GS_DEBUG_BTR, "signal_pending is now: %d (%lx)\n", 
                (int)signal_pending (current), *(long*)(&current->blocked)); 
                if (signal_pending(current)) {
                        retval = -ERESTARTSYS;
                        break;
                }
                schedule();
        }
        gs_dprintk (GS_DEBUG_BTR, "Got out of the loop. (%d)\n",
                    port->blocked_open);
        set_current_state (TASK_RUNNING);
        remove_wait_queue(&port->open_wait, &wait);
        if (!tty_hung_up_p(filp)) {
                port->count++;
        }
        port->blocked_open--;
        if (retval)
                return retval;

        port->flags |= ASYNC_NORMAL_ACTIVE;
        func_exit ();
        return 0;
}                        


void gs_close(struct tty_struct * tty, struct file * filp)
{
        unsigned long flags;
        struct gs_port *port;
        
        func_enter ();

        if (!tty) return;

        port = (struct gs_port *) tty->driver_data;

        if (!port) return;

        if (!port->tty) {
                /* This seems to happen when this is called from vhangup. */
                gs_dprintk (GS_DEBUG_CLOSE, "gs: Odd: port->tty is NULL\n");
                port->tty = tty;
        }

        spin_lock_irqsave(&port->driver_lock, flags);

        if (tty_hung_up_p(filp)) {
                spin_unlock_irqrestore(&port->driver_lock, flags);
                if (port->rd->hungup)
                        port->rd->hungup (port);
                func_exit ();
                return;
        }

        if ((tty->count == 1) && (port->count != 1)) {
                printk(KERN_ERR "gs: gs_close port %p: bad port count;"
                       " tty->count is 1, port count is %d\n", port, port->count);
                port->count = 1;
        }
        if (--port->count < 0) {
                printk(KERN_ERR "gs: gs_close port %p: bad port count: %d\n", port, port->count);
                port->count = 0;
        }

        if (port->count) {
                gs_dprintk(GS_DEBUG_CLOSE, "gs_close port %p: count: %d\n", port, port->count);
                spin_unlock_irqrestore(&port->driver_lock, flags);
                func_exit ();
                return;
        }
        port->flags |= ASYNC_CLOSING;

        /*
         * Now we wait for the transmit buffer to clear; and we notify 
         * the line discipline to only process XON/XOFF characters.
         */
        tty->closing = 1;
        /* if (port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
           tty_wait_until_sent(tty, port->closing_wait); */

        /*
         * At this point we stop accepting input.  To do this, we
         * disable the receive line status interrupts, and tell the
         * interrupt driver to stop checking the data ready bit in the
         * line status register.
         */

        port->rd->disable_rx_interrupts (port);
        spin_unlock_irqrestore(&port->driver_lock, flags);

        /* close has no way of returning "EINTR", so discard return value */
        if (port->closing_wait != ASYNC_CLOSING_WAIT_NONE)
                gs_wait_tx_flushed (port, port->closing_wait);

        port->flags &= ~GS_ACTIVE;

        if (tty->driver->flush_buffer)
                tty->driver->flush_buffer(tty);

        tty_ldisc_flush(tty);
        tty->closing = 0;

        port->event = 0;
        port->rd->close (port);
        port->rd->shutdown_port (port);
        port->tty = NULL;

        if (port->blocked_open) {
                if (port->close_delay) {
                        spin_unlock_irqrestore(&port->driver_lock, flags);
                        msleep_interruptible(jiffies_to_msecs(port->close_delay));
                        spin_lock_irqsave(&port->driver_lock, flags);
                }
                wake_up_interruptible(&port->open_wait);
        }
        port->flags &= ~(ASYNC_NORMAL_ACTIVE|ASYNC_CLOSING | ASYNC_INITIALIZED);
        wake_up_interruptible(&port->close_wait);

        func_exit ();
}


static unsigned int     gs_baudrates[] = {
  0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
  9600, 19200, 38400, 57600, 115200, 230400, 460800, 921600
};


void gs_set_termios (struct tty_struct * tty, 
                     struct termios * old_termios)
{
        struct gs_port *port;
        int baudrate, tmp, rv;
        struct termios *tiosp;

        func_enter();

        if (!tty) return;

        port = tty->driver_data;

        if (!port) return;
        if (!port->tty) {
                /* This seems to happen when this is called after gs_close. */
                gs_dprintk (GS_DEBUG_TERMIOS, "gs: Odd: port->tty is NULL\n");
                port->tty = tty;
        }


        tiosp = tty->termios;

        if (gs_debug & GS_DEBUG_TERMIOS) {
                gs_dprintk (GS_DEBUG_TERMIOS, "termios structure (%p):\n", tiosp);
        }

#if 0
        /* This is an optimization that is only allowed for dumb cards */
        /* Smart cards require knowledge of iflags and oflags too: that 
           might change hardware cooking mode.... */
#endif
        if (old_termios) {
                if(   (tiosp->c_iflag == old_termios->c_iflag)
                   && (tiosp->c_oflag == old_termios->c_oflag)
                   && (tiosp->c_cflag == old_termios->c_cflag)
                   && (tiosp->c_lflag == old_termios->c_lflag)
                   && (tiosp->c_line  == old_termios->c_line)
                   && (memcmp(tiosp->c_cc, old_termios->c_cc, NCC) == 0)) {
                        gs_dprintk(GS_DEBUG_TERMIOS, "gs_set_termios: optimized away\n");
                        return /* 0 */;
                }
        } else 
                gs_dprintk(GS_DEBUG_TERMIOS, "gs_set_termios: no old_termios: "
                           "no optimization\n");

        if(old_termios && (gs_debug & GS_DEBUG_TERMIOS)) {
                if(tiosp->c_iflag != old_termios->c_iflag)  printk("c_iflag changed\n");
                if(tiosp->c_oflag != old_termios->c_oflag)  printk("c_oflag changed\n");
                if(tiosp->c_cflag != old_termios->c_cflag)  printk("c_cflag changed\n");
                if(tiosp->c_lflag != old_termios->c_lflag)  printk("c_lflag changed\n");
                if(tiosp->c_line  != old_termios->c_line)   printk("c_line changed\n");
                if(!memcmp(tiosp->c_cc, old_termios->c_cc, NCC)) printk("c_cc changed\n");
        }

        baudrate = tiosp->c_cflag & CBAUD;
        if (baudrate & CBAUDEX) {
                baudrate &= ~CBAUDEX;
                if ((baudrate < 1) || (baudrate > 4))
                        tiosp->c_cflag &= ~CBAUDEX;
                else
                        baudrate += 15;
        }

        baudrate = gs_baudrates[baudrate];
        if ((tiosp->c_cflag & CBAUD) == B38400) {
                if (     (port->flags & ASYNC_SPD_MASK) == ASYNC_SPD_HI)
                        baudrate = 57600;
                else if ((port->flags & ASYNC_SPD_MASK) == ASYNC_SPD_VHI)
                        baudrate = 115200;
                else if ((port->flags & ASYNC_SPD_MASK) == ASYNC_SPD_SHI)
                        baudrate = 230400;
                else if ((port->flags & ASYNC_SPD_MASK) == ASYNC_SPD_WARP)
                        baudrate = 460800;
                else if ((port->flags & ASYNC_SPD_MASK) == ASYNC_SPD_CUST)
                        baudrate = (port->baud_base / port->custom_divisor);
        }

        /* I recommend using THIS instead of the mess in termios (and
           duplicating the above code). Next we should create a clean
           interface towards this variable. If your card supports arbitrary
           baud rates, (e.g. CD1400 or 16550 based cards) then everything
           will be very easy..... */
        port->baud = baudrate;

        /* Two timer ticks seems enough to wakeup something like SLIP driver */
        /* Baudrate/10 is cps. Divide by HZ to get chars per tick. */
        tmp = (baudrate / 10 / HZ) * 2;                  

        if (tmp <                 0) tmp = 0;
        if (tmp >= SERIAL_XMIT_SIZE) tmp = SERIAL_XMIT_SIZE-1;

        port->wakeup_chars = tmp;

        /* We should really wait for the characters to be all sent before
           changing the settings. -- CAL */
        rv = gs_wait_tx_flushed (port, MAX_SCHEDULE_TIMEOUT);
        if (rv < 0) return /* rv */;

        rv = port->rd->set_real_termios(port);
        if (rv < 0) return /* rv */;

        if ((!old_termios || 
             (old_termios->c_cflag & CRTSCTS)) &&
            !(      tiosp->c_cflag & CRTSCTS)) {
                tty->stopped = 0;
                gs_start(tty);
        }

#ifdef tytso_patch_94Nov25_1726
        /* This "makes sense", Why is it commented out? */

        if (!(old_termios->c_cflag & CLOCAL) &&
            (tty->termios->c_cflag & CLOCAL))
                wake_up_interruptible(&port->gs.open_wait);
#endif

        func_exit();
        return /* 0 */;
}



/* Must be called with interrupts enabled */
int gs_init_port(struct gs_port *port)
{
        unsigned long flags;
        unsigned long page;

        func_enter ();

        if (!tmp_buf) {
                page = get_zeroed_page(GFP_KERNEL);
                spin_lock_irqsave (&port->driver_lock, flags); /* Don't expect this to make a difference. */
                if (tmp_buf)
                        free_page(page);
                else
                        tmp_buf = (unsigned char *) page;
                spin_unlock_irqrestore (&port->driver_lock, flags);
                if (!tmp_buf) {
                        func_exit ();
                        return -ENOMEM;
                }
        }

        if (port->flags & ASYNC_INITIALIZED) {
                func_exit ();
                return 0;
        }
        if (!port->xmit_buf) {
                /* We may sleep in get_zeroed_page() */
                unsigned long tmp;

                tmp = get_zeroed_page(GFP_KERNEL);
                spin_lock_irqsave (&port->driver_lock, flags);
                if (port->xmit_buf) 
                        free_page (tmp);
                else
                        port->xmit_buf = (unsigned char *) tmp;
                spin_unlock_irqrestore(&port->driver_lock, flags);
                if (!port->xmit_buf) {
                        func_exit ();
                        return -ENOMEM;
                }
        }

        spin_lock_irqsave (&port->driver_lock, flags);
        if (port->tty) 
                clear_bit(TTY_IO_ERROR, &port->tty->flags);
        mutex_init(&port->port_write_mutex);
        port->xmit_cnt = port->xmit_head = port->xmit_tail = 0;
        spin_unlock_irqrestore(&port->driver_lock, flags);
        gs_set_termios(port->tty, NULL);
        spin_lock_irqsave (&port->driver_lock, flags);
        port->flags |= ASYNC_INITIALIZED;
        port->flags &= ~GS_TX_INTEN;

        spin_unlock_irqrestore(&port->driver_lock, flags);
        func_exit ();
        return 0;
}


int gs_setserial(struct gs_port *port, struct serial_struct __user *sp)
{
        struct serial_struct sio;

        if (copy_from_user(&sio, sp, sizeof(struct serial_struct)))
                return(-EFAULT);

        if (!capable(CAP_SYS_ADMIN)) {
                if ((sio.baud_base != port->baud_base) ||
                    (sio.close_delay != port->close_delay) ||
                    ((sio.flags & ~ASYNC_USR_MASK) !=
                     (port->flags & ~ASYNC_USR_MASK)))
                        return(-EPERM);
        } 

        port->flags = (port->flags & ~ASYNC_USR_MASK) |
                (sio.flags & ASYNC_USR_MASK);
  
        port->baud_base = sio.baud_base;
        port->close_delay = sio.close_delay;
        port->closing_wait = sio.closing_wait;
        port->custom_divisor = sio.custom_divisor;

        gs_set_termios (port->tty, NULL);

        return 0;
}


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

/*
 *      Generate the serial struct info.
 */

int gs_getserial(struct gs_port *port, struct serial_struct __user *sp)
{
        struct serial_struct    sio;

        memset(&sio, 0, sizeof(struct serial_struct));
        sio.flags = port->flags;
        sio.baud_base = port->baud_base;
        sio.close_delay = port->close_delay;
        sio.closing_wait = port->closing_wait;
        sio.custom_divisor = port->custom_divisor;
        sio.hub6 = 0;

        /* If you want you can override these. */
        sio.type = PORT_UNKNOWN;
        sio.xmit_fifo_size = -1;
        sio.line = -1;
        sio.port = -1;
        sio.irq = -1;

        if (port->rd->getserial)
                port->rd->getserial (port, &sio);

        if (copy_to_user(sp, &sio, sizeof(struct serial_struct)))
                return -EFAULT;
        return 0;

}


void gs_got_break(struct gs_port *port)
{
        func_enter ();

        tty_insert_flip_char(port->tty, 0, TTY_BREAK);
        tty_schedule_flip(port->tty);
        if (port->flags & ASYNC_SAK) {
                do_SAK (port->tty);
        }

        func_exit ();
}


EXPORT_SYMBOL(gs_put_char);
EXPORT_SYMBOL(gs_write);
EXPORT_SYMBOL(gs_write_room);
EXPORT_SYMBOL(gs_chars_in_buffer);
EXPORT_SYMBOL(gs_flush_buffer);
EXPORT_SYMBOL(gs_flush_chars);
EXPORT_SYMBOL(gs_stop);
EXPORT_SYMBOL(gs_start);
EXPORT_SYMBOL(gs_hangup);
EXPORT_SYMBOL(gs_block_til_ready);
EXPORT_SYMBOL(gs_close);
EXPORT_SYMBOL(gs_set_termios);
EXPORT_SYMBOL(gs_init_port);
EXPORT_SYMBOL(gs_setserial);
EXPORT_SYMBOL(gs_getserial);
EXPORT_SYMBOL(gs_got_break);

MODULE_LICENSE("GPL");