path: root/drivers/char/tty_ioctl.c

/*
 *  linux/drivers/char/tty_ioctl.c
 *
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
 * which can be dynamically activated and de-activated by the line
 * discipline handling modules (like SLIP).
 */

#include <linux/types.h>
#include <linux/termios.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/tty.h>
#include <linux/fcntl.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/mutex.h>

#include <asm/io.h>
#include <asm/uaccess.h>
#include <asm/system.h>

#undef TTY_DEBUG_WAIT_UNTIL_SENT

#undef	DEBUG

/*
 * Internal flag options for termios setting behavior
 */
#define TERMIOS_FLUSH	1
#define TERMIOS_WAIT	2
#define TERMIOS_TERMIO	4
#define TERMIOS_OLD	8


/**
 *	tty_chars_in_buffer	-	characters pending
 *	@tty: terminal
 *
 *	Return the number of bytes of data in the device private
 *	output queue. If no private method is supplied there is assumed
 *	to be no queue on the device.
 */

int tty_chars_in_buffer(struct tty_struct *tty)
{
	if (tty->ops->chars_in_buffer)
		return tty->ops->chars_in_buffer(tty);
	else
		return 0;
}
EXPORT_SYMBOL(tty_chars_in_buffer);

/**
 *	tty_write_room		-	write queue space
 *	@tty: terminal
 *
 *	Return the number of bytes that can be queued to this device
 *	at the present time. The result should be treated as a guarantee
 *	and the driver cannot offer a value it later shrinks by more than
 *	the number of bytes written. If no method is provided 2K is always
 *	returned and data may be lost as there will be no flow control.
 */
 
int tty_write_room(struct tty_struct *tty)
{
	if (tty->ops->write_room)
		return tty->ops->write_room(tty);
	return 2048;
}
EXPORT_SYMBOL(tty_write_room);

/**
 *	tty_driver_flush_buffer	-	discard internal buffer
 *	@tty: terminal
 *
 *	Discard the internal output buffer for this device. If no method
 *	is provided then either the buffer cannot be hardware flushed or
 *	there is no buffer driver side.
 */
void tty_driver_flush_buffer(struct tty_struct *tty)
{
	if (tty->ops->flush_buffer)
		tty->ops->flush_buffer(tty);
}
EXPORT_SYMBOL(tty_driver_flush_buffer);

/**
 *	tty_throttle		-	flow control
 *	@tty: terminal
 *
 *	Indicate that a tty should stop transmitting data down the stack.
 *	Takes the termios mutex to protect against parallel throttle/unthrottle
 *	and also to ensure the driver can consistently reference its own
 *	termios data at this point when implementing software flow control.
 */

void tty_throttle(struct tty_struct *tty)
{
	mutex_lock(&tty->termios_mutex);
	/* check TTY_THROTTLED first so it indicates our state */
	if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
	    tty->ops->throttle)
		tty->ops->throttle(tty);
	mutex_unlock(&tty->termios_mutex);
}
EXPORT_SYMBOL(tty_throttle);

/**
 *	tty_unthrottle		-	flow control
 *	@tty: terminal
 *
 *	Indicate that a tty may continue transmitting data down the stack.
 *	Takes the termios mutex to protect against parallel throttle/unthrottle
 *	and also to ensure the driver can consistently reference its own
 *	termios data at this point when implementing software flow control.
 *
 *	Drivers should however remember that the stack can issue a throttle,
 *	then change flow control method, then unthrottle.
 */

void tty_unthrottle(struct tty_struct *tty)
{
	mutex_lock(&tty->termios_mutex);
	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
	    tty->ops->unthrottle)
		tty->ops->unthrottle(tty);
	mutex_unlock(&tty->termios_mutex);
}
EXPORT_SYMBOL(tty_unthrottle);

/**
 *	tty_wait_until_sent	-	wait for I/O to finish
 *	@tty: tty we are waiting for
 *	@timeout: how long we will wait
 *
 *	Wait for characters pending in a tty driver to hit the wire, or
 *	for a timeout to occur (eg due to flow control)
 *
 *	Locking: none
 */

void tty_wait_until_sent(struct tty_struct *tty, long timeout)
{
#ifdef TTY_DEBUG_WAIT_UNTIL_SENT
	char buf[64];

	printk(KERN_DEBUG "%s wait until sent...\n", tty_name(tty, buf));
#endif
	if (!timeout)
		timeout = MAX_SCHEDULE_TIMEOUT;
	if (wait_event_interruptible_timeout(tty->write_wait,
			!tty_chars_in_buffer(tty), timeout) >= 0) {
		if (tty->ops->wait_until_sent)
			tty->ops->wait_until_sent(tty, timeout);
	}
}
EXPORT_SYMBOL(tty_wait_until_sent);


/*
 *		Termios Helper Methods
 */

static void unset_locked_termios(struct ktermios *termios,
				 struct ktermios *old,