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/*

 *  linux/drivers/char/pty.c

 *

 *  Copyright (C) 1991, 1992  Linus Torvalds

 */

/*

 *      pty.c

 *

 * This module exports the following pty function:

 *

 *      int  pty_open(struct tty_struct * tty, struct file * filp);

 */

#include <linux/errno.h>

#include <linux/sched.h>

#include <linux/interrupt.h>

#include <linux/tty.h>

#include <linux/tty_flip.h>

#include <linux/fcntl.h>

#include <linux/string.h>

#include <linux/major.h>

#include <linux/mm.h>

#include <asm/segment.h>

#include <asm/system.h>

#include <asm/bitops.h>

struct pty_struct {

        int     magic;

        struct wait_queue * open_wait;

};

#define PTY_MAGIC 0x5001

#define PTY_BUF_SIZE PAGE_SIZE/2

/*

 * tmp_buf is used as a temporary buffer by pty_write.  We need to

 * lock it in case the memcpy_fromfs blocks while swapping in a page,

 * and some other program tries to do a pty write at the same time.

 * Since the lock will only come under contention when the system is

 * swapping and available memory is low, it makes sense to share one

 * buffer across all the PTY's, since it significantly saves memory if

 * large numbers of PTY's are open.

 */

static unsigned char *tmp_buf;

static struct semaphore tmp_buf_sem = MUTEX;

struct tty_driver pty_driver, pty_slave_driver;

struct tty_driver old_pty_driver, old_pty_slave_driver;

static int pty_refcount;

static struct tty_struct *pty_table[NR_PTYS];

static struct termios *pty_termios[NR_PTYS];

static struct termios *pty_termios_locked[NR_PTYS];

static struct tty_struct *ttyp_table[NR_PTYS];

static struct termios *ttyp_termios[NR_PTYS];

static struct termios *ttyp_termios_locked[NR_PTYS];

static struct pty_struct pty_state[NR_PTYS];

#define MIN(a,b)        ((a) < (b) ? (a) : (b))

static void pty_close(struct tty_struct * tty, struct file * filp)

{

        if (!tty)

                return;

        if (tty->driver.subtype == PTY_TYPE_MASTER) {

                if (tty->count > 1)

                        printk("master pty_close: count = %d!!\n", tty->count);

        } else {

                if (tty->count > 2)

                        return;

        }

        wake_up_interruptible(&tty->read_wait);

        wake_up_interruptible(&tty->write_wait);

        if (!tty->link)

                return;

        wake_up_interruptible(&tty->link->read_wait);

        wake_up_interruptible(&tty->link->write_wait);

        set_bit(TTY_OTHER_CLOSED, &tty->link->flags);

        if (tty->driver.subtype == PTY_TYPE_MASTER) {

                tty_hangup(tty->link);

                set_bit(TTY_OTHER_CLOSED, &tty->flags);

        }

}

/*

 * The unthrottle routine is called by the line discipline to signal

 * that it can receive more characters.  For PTY's, the TTY_THROTTLED

 * flag is always set, to force the line discipline to always call the

 * unthrottle routine when there are fewer than TTY_THRESHOLD_UNTHROTTLE

 * characters in the queue.  This is necessary since each time this

 * happens, we need to wake up any sleeping processes that could be

 * (1) trying to send data to the pty, or (2) waiting in wait_until_sent()

 * for the pty buffer to be drained.

 */

static void pty_unthrottle(struct tty_struct * tty)

{

        struct tty_struct *o_tty = tty->link;

        if (!o_tty)

                return;

        if ((o_tty->flags & (1 << TTY_DO_WRITE_WAKEUP)) &&

            o_tty->ldisc.write_wakeup)

                (o_tty->ldisc.write_wakeup)(o_tty);

        wake_up_interruptible(&o_tty->write_wait);

        set_bit(TTY_THROTTLED, &tty->flags);

}

static int pty_write(struct tty_struct * tty, int from_user,

                       const unsigned char *buf, int count)

{

        struct tty_struct *to = tty->link;

        int     c=0, n, r;

        char    *temp_buffer;

        if (!to || tty->stopped)

                return 0;

        if (from_user) {

                down(&tmp_buf_sem);

                temp_buffer = tmp_buf +

                        ((tty->driver.subtype-1) * PTY_BUF_SIZE);

                while (count > 0) {

                        n = MIN(count, PTY_BUF_SIZE);

                        memcpy_fromfs(temp_buffer, buf, n);

                        r = to->ldisc.receive_room(to);

                        if (r <= 0)

                                break;

                        n = MIN(n, r);

                        to->ldisc.receive_buf(to, temp_buffer, 0, n);

                        buf += n;  c+= n;

                        count -= n;

                }

                up(&tmp_buf_sem);

        } else {

                c = MIN(count, to->ldisc.receive_room(to));

                to->ldisc.receive_buf(to, buf, 0, c);

        }

        return c;

}

static int pty_write_room(struct tty_struct *tty)

{

        struct tty_struct *to = tty->link;

        if (!to || tty->stopped)

                return 0;

        return to->ldisc.receive_room(to);

}

/*

 * Modified for asymmetric master/slave behavior

 * The chars_in_buffer() value is used by the ldisc select() function

 * to hold off writing when chars_in_buffer > WAKEUP_CHARS (== 256).

 * To allow typed-ahead commands to accumulate, the master side returns 0

 * until the buffer is half full. The slave side returns the true count.

 */

static int pty_chars_in_buffer(struct tty_struct *tty)

{

        struct tty_struct *to = tty->link;

        int count;

        if (!to || !to->ldisc.chars_in_buffer)

                return 0;

        /* The ldisc must report 0 if no characters available to be read */

        count = to->ldisc.chars_in_buffer(to);

        if (tty->driver.subtype == PTY_TYPE_SLAVE) return count;

        /*

         * Master side driver ... return 0 if the other side's read buffer

         * is less than half full.  This allows room for typed-ahead commands

         * with a reasonable margin to avoid overflow.

         */

        return ((count < N_TTY_BUF_SIZE/2) ? 0 : count);

}

static void pty_flush_buffer(struct tty_struct *tty)

{

        struct tty_struct *to = tty->link;

        if (!to)

                return;

        if (to->ldisc.flush_buffer)

                to->ldisc.flush_buffer(to);

        if (to->packet) {

                tty->ctrl_status |= TIOCPKT_FLUSHWRITE;

                wake_up_interruptible(&to->read_wait);

        }

}

int pty_open(struct tty_struct *tty, struct file * filp)

{

        int     retval;

        int     line;

        struct  pty_struct *pty;

        retval = -ENODEV;

        if (!tty || !tty->link)

                goto out;

        line = MINOR(tty->device) - tty->driver.minor_start;

        if ((line < 0) || (line >= NR_PTYS))

                goto out;

        pty = pty_state + line;

        tty->driver_data = pty;

        if (!tmp_buf) {

                unsigned long page = __get_free_page(GFP_KERNEL);

                if (!tmp_buf) {

                        retval = -ENOMEM;

                        if (!page)

                                goto out;

                        tmp_buf = (unsigned char *) page;

                        memset((void *) page, 0, PAGE_SIZE);

                } else

                        free_page(page);

        }

        retval = -EIO;

        if (test_bit(TTY_OTHER_CLOSED, &tty->flags))

                goto out;

        if (tty->link->count != 1)

                goto out;

        clear_bit(TTY_OTHER_CLOSED, &tty->link->flags);

        wake_up_interruptible(&pty->open_wait);

        set_bit(TTY_THROTTLED, &tty->flags);

        retval = 0;

out:

        return retval;

}

static void pty_set_termios(struct tty_struct *tty, struct termios *old_termios)

{

        tty->termios->c_cflag &= ~(CSIZE | PARENB);

        tty->termios->c_cflag |= (CS8 | CREAD);

}

int pty_init(void)

{

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

        memset(&pty_driver, 0, sizeof(struct tty_driver));

        pty_driver.magic = TTY_DRIVER_MAGIC;

        pty_driver.name = "pty";

        pty_driver.major = PTY_MASTER_MAJOR;

        pty_driver.minor_start = 0;

        pty_driver.num = NR_PTYS;

        pty_driver.type = TTY_DRIVER_TYPE_PTY;

        pty_driver.subtype = PTY_TYPE_MASTER;

        pty_driver.init_termios = tty_std_termios;

        pty_driver.init_termios.c_iflag = 0;

        pty_driver.init_termios.c_oflag = 0;

        pty_driver.init_termios.c_cflag = B38400 | CS8 | CREAD;

        pty_driver.init_termios.c_lflag = 0;

        pty_driver.flags = TTY_DRIVER_RESET_TERMIOS | TTY_DRIVER_REAL_RAW;

        pty_driver.refcount = &pty_refcount;

        pty_driver.table = pty_table;

        pty_driver.termios = pty_termios;

        pty_driver.termios_locked = pty_termios_locked;

        pty_driver.other = &pty_slave_driver;

        pty_driver.open = pty_open;

        pty_driver.close = pty_close;

        pty_driver.write = pty_write;

        pty_driver.write_room = pty_write_room;

        pty_driver.flush_buffer = pty_flush_buffer;

        pty_driver.chars_in_buffer = pty_chars_in_buffer;

        pty_driver.unthrottle = pty_unthrottle;

        pty_driver.set_termios = pty_set_termios;

        pty_slave_driver = pty_driver;

        pty_slave_driver.name = "ttyp";

        pty_slave_driver.subtype = PTY_TYPE_SLAVE;

        pty_slave_driver.major = PTY_SLAVE_MAJOR;

        pty_slave_driver.minor_start = 0;

        pty_slave_driver.init_termios = tty_std_termios;

        pty_slave_driver.init_termios.c_cflag = B38400 | CS8 | CREAD;

        pty_slave_driver.table = ttyp_table;

        pty_slave_driver.termios = ttyp_termios;

        pty_slave_driver.termios_locked = ttyp_termios_locked;

        pty_slave_driver.other = &pty_driver;

        old_pty_driver = pty_driver;

        old_pty_driver.major = TTY_MAJOR;

        old_pty_driver.minor_start = 128;

        old_pty_driver.num = (NR_PTYS > 64) ? 64 : NR_PTYS;

        old_pty_driver.other = &old_pty_slave_driver;

        old_pty_slave_driver = pty_slave_driver;

        old_pty_slave_driver.major = TTY_MAJOR;

        old_pty_slave_driver.minor_start = 192;

        old_pty_slave_driver.num = (NR_PTYS > 64) ? 64 : NR_PTYS;

        old_pty_slave_driver.other = &old_pty_driver;

        tmp_buf = 0;

        if (tty_register_driver(&pty_driver))

                panic("Couldn't register pty driver");

        if (tty_register_driver(&pty_slave_driver))

                panic("Couldn't register pty slave driver");

        if (tty_register_driver(&old_pty_driver))

                panic("Couldn't register compat pty driver");

        if (tty_register_driver(&old_pty_slave_driver))

                panic("Couldn't register compat pty slave driver");

        return 0;

}