n_tty.c

unix/linux 编程实践一书的所有源代码

				/* Record the column of first canon char. */
				if (tty->canon_head == tty->read_head)
					tty->canon_column = tty->column;
				echo_char(c, tty);
			}
			/*
			 * XXX does PARMRK doubling happen for
			 * EOL_CHAR and EOL2_CHAR?
			 */
			if (I_PARMRK(tty) && c == (unsigned char) '\377')
				put_tty_queue(c, tty);

		handle_newline:
			set_bit(tty->read_head, &tty->read_flags);
			put_tty_queue(c, tty);
			tty->canon_head = tty->read_head;
			tty->canon_data++;
			if (tty->fasync)
				kill_fasync(tty->fasync, SIGIO);
			if (tty->read_wait)
				wake_up_interruptible(&tty->read_wait);
			return;
		}
	}
	
	finish_erasing(tty);
	if (L_ECHO(tty)) {
		if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
			put_char('\a', tty); /* beep if no space */
			return;
		}
		if (c == '\n')
			opost('\n', tty);
		else {
			/* Record the column of first canon char. */
			if (tty->canon_head == tty->read_head)
				tty->canon_column = tty->column;
			echo_char(c, tty);
		}
	}

	if (I_PARMRK(tty) && c == (unsigned char) '\377')
		put_tty_queue(c, tty);

	put_tty_queue(c, tty);
}	

static int n_tty_receive_room(struct tty_struct *tty)
{
	int	left = N_TTY_BUF_SIZE - tty->read_cnt - 1;

	/*
	 * If we are doing input canonicalization, and there are no
	 * pending newlines, let characters through without limit, so
	 * that erase characters will be handled.  Other excess
	 * characters will be beeped.
	 */
	if (tty->icanon && !tty->canon_data)
		return N_TTY_BUF_SIZE;

	if (left > 0)
		return left;
	return 0;
}

static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
			      char *fp, int count)
{
	const unsigned char *p;
	char *f, flags = TTY_NORMAL;
	int	i;
	char	buf[64];

	if (!tty->read_buf)
		return;

	if (tty->real_raw) {
		i = MIN(count, MIN(N_TTY_BUF_SIZE - tty->read_cnt,
				   N_TTY_BUF_SIZE - tty->read_head));
		memcpy(tty->read_buf + tty->read_head, cp, i);
		tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
		tty->read_cnt += i;
		cp += i;
		count -= i;

		i = MIN(count, MIN(N_TTY_BUF_SIZE - tty->read_cnt,
			       N_TTY_BUF_SIZE - tty->read_head));
		memcpy(tty->read_buf + tty->read_head, cp, i);
		tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
		tty->read_cnt += i;
	} else {
		for (i=count, p = cp, f = fp; i; i--, p++) {
			if (f)
				flags = *f++;
			switch (flags) {
			case TTY_NORMAL:
				n_tty_receive_char(tty, *p);
				break;
			case TTY_BREAK:
				n_tty_receive_break(tty);
				break;
			case TTY_PARITY:
			case TTY_FRAME:
				n_tty_receive_parity_error(tty, *p);
				break;
			case TTY_OVERRUN:
				n_tty_receive_overrun(tty);
				break;
			default:
				printk("%s: unknown flag %d\n",
				       tty_name(tty, buf), flags);
				break;
			}
		}
		if (tty->driver.flush_chars)
			tty->driver.flush_chars(tty);
	}

	if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
		if (tty->fasync)
			kill_fasync(tty->fasync, SIGIO);
		if (tty->read_wait)
			wake_up_interruptible(&tty->read_wait);
	}

	/*
	 * Check the remaining room for the input canonicalization
	 * mode.  We don't want to throttle the driver if we're in
	 * canonical mode and don't have a newline yet!
	 */
	if (n_tty_receive_room(tty) < TTY_THRESHOLD_THROTTLE) {
		/* check TTY_THROTTLED first so it indicates our state */
		if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
		    tty->driver.throttle)
			tty->driver.throttle(tty);
	}
}

int is_ignored(int sig)
{
	return (sigismember(&current->blocked, sig) ||
	        current->sig->action[sig-1].sa.sa_handler == SIG_IGN);
}

static void n_tty_set_termios(struct tty_struct *tty, struct termios * old)
{
	if (!tty)
		return;
	
	tty->icanon = (L_ICANON(tty) != 0);
	if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
		tty->raw = 1;
		tty->real_raw = 1;
		return;
	}
	if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
	    I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
	    I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
	    I_PARMRK(tty)) {
		cli();
		memset(tty->process_char_map, 0, 256/8);

		if (I_IGNCR(tty) || I_ICRNL(tty))
			set_bit('\r', &tty->process_char_map);
		if (I_INLCR(tty))
			set_bit('\n', &tty->process_char_map);

		if (L_ICANON(tty)) {
			set_bit(ERASE_CHAR(tty), &tty->process_char_map);
			set_bit(KILL_CHAR(tty), &tty->process_char_map);
			set_bit(EOF_CHAR(tty), &tty->process_char_map);
			set_bit('\n', &tty->process_char_map);
			set_bit(EOL_CHAR(tty), &tty->process_char_map);
			if (L_IEXTEN(tty)) {
				set_bit(WERASE_CHAR(tty),
					&tty->process_char_map);
				set_bit(LNEXT_CHAR(tty),
					&tty->process_char_map);
				set_bit(EOL2_CHAR(tty),
					&tty->process_char_map);
				if (L_ECHO(tty))
					set_bit(REPRINT_CHAR(tty),
						&tty->process_char_map);
			}
		}
		if (I_IXON(tty)) {
			set_bit(START_CHAR(tty), &tty->process_char_map);
			set_bit(STOP_CHAR(tty), &tty->process_char_map);
		}
		if (L_ISIG(tty)) {
			set_bit(INTR_CHAR(tty), &tty->process_char_map);
			set_bit(QUIT_CHAR(tty), &tty->process_char_map);
			set_bit(SUSP_CHAR(tty), &tty->process_char_map);
		}
		clear_bit(__DISABLED_CHAR, &tty->process_char_map);
		sti();
		tty->raw = 0;
		tty->real_raw = 0;
	} else {
		tty->raw = 1;
		if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
		    (I_IGNPAR(tty) || !I_INPCK(tty)) &&
		    (tty->driver.flags & TTY_DRIVER_REAL_RAW))
			tty->real_raw = 1;
		else
			tty->real_raw = 0;
	}
}

static void n_tty_close(struct tty_struct *tty)
{
	n_tty_flush_buffer(tty);
	if (tty->read_buf) {
		free_page((unsigned long) tty->read_buf);
		tty->read_buf = 0;
	}
}

static int n_tty_open(struct tty_struct *tty)
{
	if (!tty)
		return -EINVAL;

	if (!tty->read_buf) {
		tty->read_buf = (unsigned char *)
			get_free_page(in_interrupt() ? GFP_ATOMIC : GFP_KERNEL);
		if (!tty->read_buf)
			return -ENOMEM;
	}
	memset(tty->read_buf, 0, N_TTY_BUF_SIZE);
	reset_buffer_flags(tty);
	tty->column = 0;
	n_tty_set_termios(tty, 0);
	tty->minimum_to_wake = 1;
	tty->closing = 0;
	return 0;
}

static inline int input_available_p(struct tty_struct *tty, int amt)
{
	if (tty->icanon) {
		if (tty->canon_data)
			return 1;
	} else if (tty->read_cnt >= (amt ? amt : 1))
		return 1;

	return 0;
}

/*
 * Helper function to speed up read_chan.  It is only called when
 * ICANON is off; it copies characters straight from the tty queue to
 * user space directly.  It can be profitably called twice; once to
 * drain the space from the tail pointer to the (physical) end of the
 * buffer, and once to drain the space from the (physical) beginning of
 * the buffer to head pointer.
 */
static inline int copy_from_read_buf(struct tty_struct *tty,
				      unsigned char **b,
				      size_t *nr)

{
	int retval;
	ssize_t n;

	retval = 0;
	n = MIN(*nr, MIN(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail));
	if (n) {
		mb();
		retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
		n -= retval;
		tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
		tty->read_cnt -= n;
		*b += n;
		*nr -= n;
	}
	return retval;
}

static ssize_t read_chan(struct tty_struct *tty, struct file *file,
			 unsigned char *buf, size_t nr)
{
	unsigned char *b = buf;
	struct wait_queue wait = { current, NULL };
	int c;
	int minimum, time;
	ssize_t retval = 0;
	ssize_t size;
	long timeout;

do_it_again:

	if (!tty->read_buf) {
		printk("n_tty_read_chan: called with read_buf == NULL?!?\n");
		return -EIO;
	}

	/* Job control check -- must be done at start and after
	   every sleep (POSIX.1 7.1.1.4). */
	/* NOTE: not yet done after every sleep pending a thorough
	   check of the logic of this change. -- jlc */
	/* don't stop on /dev/console */
	if (file->f_dentry->d_inode->i_rdev != CONSOLE_DEV &&
	    file->f_dentry->d_inode->i_rdev != SYSCONS_DEV &&
	    current->tty == tty) {
		if (tty->pgrp <= 0)
			printk("read_chan: tty->pgrp <= 0!\n");
		else if (current->pgrp != tty->pgrp) {
			if (is_ignored(SIGTTIN) ||
			    is_orphaned_pgrp(current->pgrp))
				return -EIO;
			kill_pg(current->pgrp, SIGTTIN, 1);
			return -ERESTARTSYS;
		}
	}

	minimum = time = 0;
	timeout = MAX_SCHEDULE_TIMEOUT;
	if (!tty->icanon) {
		time = (HZ / 10) * TIME_CHAR(tty);
		minimum = MIN_CHAR(tty);
		if (minimum) {
			if (time)
				tty->minimum_to_wake = 1;
			else if (!waitqueue_active(&tty->read_wait) ||
				 (tty->minimum_to_wake > minimum))
				tty->minimum_to_wake = minimum;
		} else {
			timeout = 0;
			if (time) {
				timeout = time;
				time = 0;
			}
			tty->minimum_to_wake = minimum = 1;
		}
	}

	if (file->f_flags & O_NONBLOCK) {
		if (down_trylock(&tty->atomic_read))
			return -EAGAIN;
	}
	else {
		if (down_interruptible(&tty->atomic_read))
			return -ERESTARTSYS;
	}

	add_wait_queue(&tty->read_wait, &wait);
	set_bit(TTY_DONT_FLIP, &tty->flags);
	while (nr) {
		/* First test for status change. */
		if (tty->packet && tty->link->ctrl_status) {
			unsigned char cs;
			if (b != buf)
				break;
			cs = tty->link->ctrl_status;
			tty->link->ctrl_status = 0;
			put_user(cs, b++);
			nr--;
			break;
		}
		/* This statement must be first before checking for input
		   so that any interrupt will set the state back to
		   TASK_RUNNING. */
		current->state = TASK_INTERRUPTIBLE;
		
		if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
		    ((minimum - (b - buf)) >= 1))
			tty->minimum_to_wake = (minimum - (b - buf));
		
		if (!input_available_p(tty, 0)) {
			if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
				retval = -EIO;
				break;
			}
			if (tty_hung_up_p(file))
				break;
			if (!timeout)
				break;
			if (file->f_flags & O_NONBLOCK) {
				retval = -EAGAIN;
				break;
			}
			if (signal_pending(current)) {
				retval = -ERESTARTSYS;
				break;
			}
			clear_bit(TTY_DONT_FLIP, &tty->flags);
			timeout = schedule_timeout(timeout);
			set_bit(TTY_DONT_FLIP, &tty->flags);
			continue;
		}
		current->state = TASK_RUNNING;

		/* Deal with packet mode. */
		if (tty->packet && b == buf) {
			put_user(TIOCPKT_DATA, b++);
			nr--;
		}

		if (tty->icanon) {
			/* N.B. avoid overrun if nr == 0 */
			while (nr && tty->read_cnt) {
 				int eol;

				eol = test_and_clear_bit(tty->read_tail,
						&tty->read_flags);
				c = tty->read_buf[tty->read_tail];
				tty->read_tail = ((tty->read_tail+1) &
						  (N_TTY_BUF_SIZE-1));
				tty->read_cnt--;

				if (!eol || (c != __DISABLED_CHAR)) {
					put_user(c, b++);
					nr--;
				}
				if (eol) {
					/* this test should be redundant:
					 * we shouldn't be reading data if
					 * canon_data is 0
					 */
					if (--tty->canon_data < 0)
						tty->canon_data = 0;
					break;
				}
			}
		} else {
			int uncopied;
			uncopied = copy_from_read_buf(tty, &b, &nr);
			uncopied += copy_from_read_buf(tty, &b, &nr);
			if (uncopied) {
				retval = -EFAULT;
				break;
			}
		}

		/* If there is enough space in the read buffer now, let the
		 * low-level driver know. We use n_tty_chars_in_buffer() to
		 * check the buffer, as it now knows about canonical mode.
		 * Otherwise, if the driver is throttled and the line is
		 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
		 * we won't get any more characters.
		 */
		if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE)
			check_unthrottle(tty);

		if (b - buf >= minimum)
			break;
		if (time)
			timeout = time;
	}
	clear_bit(TTY_DONT_FLIP, &tty->flags);
	up(&tty->atomic_read);
	remove_wait_queue(&tty->read_wait, &wait);

	if (!waitqueue_active(&tty->read_wait))
		tty->minimum_to_wake = minimum;

	current->state = TASK_RUNNING;
	size = b - buf;
	if (size) {
		retval = size;
		if (nr)
	       		clear_bit(TTY_PUSH, &tty->flags);
	} else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
		 goto do_it_again;

	return retval;
}

static ssize_t write_chan(struct tty_struct * tty, struct file * file,
			  const unsigned char * buf, size_t nr)
{
	const unsigned char *b = buf;
	struct wait_queue wait = { current, NULL };
	int c;
	ssize_t retval = 0;

	/* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
	if (L_TOSTOP(tty) && 
	    file->f_dentry->d_inode->i_rdev != CONSOLE_DEV &&
	    file->f_dentry->d_inode->i_rdev != SYSCONS_DEV) {
		retval = tty_check_change(tty);
		if (retval)
			return retval;
	}

	add_wait_queue(&tty->write_wait, &wait);
	while (1) {
		current->state = TASK_INTERRUPTIBLE;
		if (signal_pending(current)) {
			retval = -ERESTARTSYS;
			break;
		}
		if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
			retval = -EIO;
			break;
		}
		if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
			while (nr > 0) {
				ssize_t num = opost_block(tty, b, nr);
				if (num < 0) {
					retval = num;
					goto break_out;
				}
				b += num;
				nr -= num;
				if (nr == 0)
					break;
				current->state = TASK_RUNNING;
				get_user(c, b);
				current->state = TASK_INTERRUPTIBLE;
				if (opost(c, tty) < 0)
					break;
				b++; nr--;
			}
			if (tty->driver.flush_chars)
				tty->driver.flush_chars(tty);
		} else {
			current->state = TASK_RUNNING;
			c = tty->driver.write(tty, 1, b, nr);
			current->state = TASK_INTERRUPTIBLE;
			if (c < 0) {
				retval = c;
				goto break_out;
			}
			b += c;
			nr -= c;
		}
		if (!nr)
			break;
		if (file->f_flags & O_NONBLOCK) {
			retval = -EAGAIN;
			break;
		}
		schedule();
	}
break_out:
	current->state = TASK_RUNNING;
	remove_wait_queue(&tty->write_wait, &wait);
	return (b - buf) ? b - buf : retval;
}

static unsigned int normal_poll(struct tty_struct * tty, struct file * file, poll_table *wait)
{
	unsigned int mask = 0;

	poll_wait(file, &tty->read_wait, wait);
	poll_wait(file, &tty->write_wait, wait);
	if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
		mask |= POLLIN | POLLRDNORM;
	if (tty->packet && tty->link->ctrl_status)
		mask |= POLLPRI | POLLIN | POLLRDNORM;
	if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
		mask |= POLLHUP;
	if (tty_hung_up_p(file))
		mask |= POLLHUP;
	if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
		if (MIN_CHAR(tty) && !TIME_CHAR(tty))
			tty->minimum_to_wake = MIN_CHAR(tty);
		else
			tty->minimum_to_wake = 1;
	}
	if (tty->driver.chars_in_buffer(tty) < WAKEUP_CHARS)
		mask |= POLLOUT | POLLWRNORM;
	return mask;
}

struct tty_ldisc tty_ldisc_N_TTY = {
	TTY_LDISC_MAGIC,	/* magic */
	"n_tty",		/* name */
	0,			/* num */
	0,			/* flags */
	n_tty_open,		/* open */
	n_tty_close,		/* close */
	n_tty_flush_buffer,	/* flush_buffer */
	n_tty_chars_in_buffer,	/* chars_in_buffer */
	read_chan,		/* read */
	write_chan,		/* write */
	n_tty_ioctl,		/* ioctl */
	n_tty_set_termios,	/* set_termios */
	normal_poll,		/* poll */
	n_tty_receive_buf,	/* receive_buf */
	n_tty_receive_room,	/* receive_room */
	0			/* write_wakeup */
};