/* *  linux/kernel/chr_drv/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/tty.h>#include <linux/fcntl.h>#include <linux/interrupt.h>#include <linux/string.h>#include <asm/system.h>#include <asm/bitops.h>#define MIN(a,b)	((a) < (b) ? (a) : (b))static void pty_close(struct tty_struct * tty, struct file * filp){	if (!tty)		return;	if (IS_A_PTY_MASTER(tty->line)) {		if (tty->count > 1)			printk("master pty_close: count = %d!!\n", tty->count);	} else {		if (tty->count > 2)			return;	}	wake_up_interruptible(&tty->secondary.proc_list);	wake_up_interruptible(&tty->read_q.proc_list);	wake_up_interruptible(&tty->write_q.proc_list);	if (!tty->link)		return;	wake_up_interruptible(&tty->link->secondary.proc_list);	wake_up_interruptible(&tty->link->read_q.proc_list);	wake_up_interruptible(&tty->link->write_q.proc_list);	if (IS_A_PTY_MASTER(tty->line))		tty_hangup(tty->link);	else {		start_tty(tty);		set_bit(TTY_SLAVE_CLOSED, &tty->link->flags);	}}static inline void pty_copy(struct tty_struct * from, struct tty_struct * to){	unsigned long count, n;	struct tty_queue *fq, *tq;	if (from->stopped || EMPTY(&from->write_q))		return;	fq = &from->write_q;	tq = &to->read_q;	count = MIN(CHARS(fq), LEFT(tq));	while (count) {		n = MIN(MIN(TTY_BUF_SIZE - fq->tail, TTY_BUF_SIZE - tq->head),			count);		memcpy(&tq->buf[tq->head], &fq->buf[fq->tail], n);		count -= n;		fq->tail = (fq->tail + n) & (TTY_BUF_SIZE - 1);		tq->head = (tq->head + n) & (TTY_BUF_SIZE - 1);	}	TTY_READ_FLUSH(to);	if (LEFT(fq) > WAKEUP_CHARS)		wake_up_interruptible(&fq->proc_list);	if (from->write_data_cnt) {		set_bit(from->line, &tty_check_write);		mark_bh(TTY_BH);	}}/* * This routine gets called when tty_write has put something into * the write_queue. It copies the input to the output-queue of its * slave. */static void pty_write(struct tty_struct * tty){	if (tty->link)		pty_copy(tty,tty->link);}int pty_open(struct tty_struct *tty, struct file * filp){	if (!tty || !tty->link)		return -ENODEV;	if (IS_A_PTY_SLAVE(tty->line))		clear_bit(TTY_SLAVE_CLOSED, &tty->link->flags);	tty->write = tty->link->write = pty_write;	tty->close = tty->link->close = pty_close;	wake_up_interruptible(&tty->read_q.proc_list);	if (filp->f_flags & O_NDELAY)		return 0;	while (!tty->link->count && !(current->signal & ~current->blocked))		interruptible_sleep_on(&tty->link->read_q.proc_list);	if (!tty->link->count)		return -ERESTARTSYS;	return 0;}