linux-pty.c

/*
 *  linux/kernel/chr_drv/pty.c
 *
 *  (C) 1991  Linus Torvalds
 */

/*
 *    pty.c
 *
 * This module implements the pty functions
 *    void mpty_write(struct tty_struct * queue);
 *    void spty_write(struct tty_struct * queue);
 */

#include <linux/tty.h>
#include <linux/sched.h>
#include <asm/system.h>
#include <asm/io.h>

static inline void pty_copy(struct tty_struct * from, struct tty_struct * to)
{
    char c;

    while (!from->stopped && !EMPTY(from->write_q)) {
        if (FULL(to->read_q)) {
            if (FULL(to->secondary))
                break;
            copy_to_cooked(to);
            continue;
        }
        GETCH(from->write_q,c);
        PUTCH(c,to->read_q);
        if (current->signal & ~current->blocked)
            break;
    }
    copy_to_cooked(to);
    wake_up(&from->write_q->proc_list);
}

/*
 * This routine gets called when tty_write has put something into
 * the write_queue. It copies the input to the output-queue of it's
 * slave.
 */
void mpty_write(struct tty_struct * tty)
{
    int nr = tty - tty_table;

    if ((nr >> 6) != 2)
        printk("bad mpty/n/r");
    else
        pty_copy(tty,tty+64);
}

void spty_write(struct tty_struct * tty)
{
    int nr = tty - tty_table;

    if ((nr >> 6) != 3)
        printk("bad spty/n/r");
    else
        pty_copy(tty,tty-64);
}