1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright (C) 1991, 1992, 1993, 1994 Linus Torvalds
5 * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
6 * which can be dynamically activated and de-activated by the line
7 * discipline handling modules (like SLIP).
10 #include <linux/types.h>
11 #include <linux/termios.h>
12 #include <linux/errno.h>
13 #include <linux/sched/signal.h>
14 #include <linux/kernel.h>
15 #include <linux/major.h>
16 #include <linux/tty.h>
17 #include <linux/fcntl.h>
18 #include <linux/string.h>
20 #include <linux/module.h>
21 #include <linux/bitops.h>
22 #include <linux/mutex.h>
23 #include <linux/compat.h>
27 #include <linux/uaccess.h>
29 #undef TTY_DEBUG_WAIT_UNTIL_SENT
31 #ifdef TTY_DEBUG_WAIT_UNTIL_SENT
32 # define tty_debug_wait_until_sent(tty, f, args...) tty_debug(tty, f, ##args)
34 # define tty_debug_wait_until_sent(tty, f, args...) do {} while (0)
40 * Internal flag options for termios setting behavior
42 #define TERMIOS_FLUSH 1
43 #define TERMIOS_WAIT 2
44 #define TERMIOS_TERMIO 4
49 * tty_chars_in_buffer - characters pending
52 * Return the number of bytes of data in the device private
53 * output queue. If no private method is supplied there is assumed
54 * to be no queue on the device.
57 unsigned int tty_chars_in_buffer(struct tty_struct *tty)
59 if (tty->ops->chars_in_buffer)
60 return tty->ops->chars_in_buffer(tty);
63 EXPORT_SYMBOL(tty_chars_in_buffer);
66 * tty_write_room - write queue space
69 * Return the number of bytes that can be queued to this device
70 * at the present time. The result should be treated as a guarantee
71 * and the driver cannot offer a value it later shrinks by more than
72 * the number of bytes written. If no method is provided 2K is always
73 * returned and data may be lost as there will be no flow control.
76 unsigned int tty_write_room(struct tty_struct *tty)
78 if (tty->ops->write_room)
79 return tty->ops->write_room(tty);
82 EXPORT_SYMBOL(tty_write_room);
85 * tty_driver_flush_buffer - discard internal buffer
88 * Discard the internal output buffer for this device. If no method
89 * is provided then either the buffer cannot be hardware flushed or
90 * there is no buffer driver side.
92 void tty_driver_flush_buffer(struct tty_struct *tty)
94 if (tty->ops->flush_buffer)
95 tty->ops->flush_buffer(tty);
97 EXPORT_SYMBOL(tty_driver_flush_buffer);
100 * tty_unthrottle - flow control
103 * Indicate that a tty may continue transmitting data down the stack.
104 * Takes the termios rwsem to protect against parallel throttle/unthrottle
105 * and also to ensure the driver can consistently reference its own
106 * termios data at this point when implementing software flow control.
108 * Drivers should however remember that the stack can issue a throttle,
109 * then change flow control method, then unthrottle.
112 void tty_unthrottle(struct tty_struct *tty)
114 down_write(&tty->termios_rwsem);
115 if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
116 tty->ops->unthrottle)
117 tty->ops->unthrottle(tty);
118 tty->flow_change = 0;
119 up_write(&tty->termios_rwsem);
121 EXPORT_SYMBOL(tty_unthrottle);
124 * tty_throttle_safe - flow control
127 * Indicate that a tty should stop transmitting data down the stack.
128 * tty_throttle_safe will only attempt throttle if tty->flow_change is
129 * TTY_THROTTLE_SAFE. Prevents an accidental throttle due to race
130 * conditions when throttling is conditional on factors evaluated prior to
133 * Returns 0 if tty is throttled (or was already throttled)
136 int tty_throttle_safe(struct tty_struct *tty)
140 mutex_lock(&tty->throttle_mutex);
141 if (!tty_throttled(tty)) {
142 if (tty->flow_change != TTY_THROTTLE_SAFE)
145 set_bit(TTY_THROTTLED, &tty->flags);
146 if (tty->ops->throttle)
147 tty->ops->throttle(tty);
150 mutex_unlock(&tty->throttle_mutex);
156 * tty_unthrottle_safe - flow control
159 * Similar to tty_unthrottle() but will only attempt unthrottle
160 * if tty->flow_change is TTY_UNTHROTTLE_SAFE. Prevents an accidental
161 * unthrottle due to race conditions when unthrottling is conditional
162 * on factors evaluated prior to unthrottling.
164 * Returns 0 if tty is unthrottled (or was already unthrottled)
167 int tty_unthrottle_safe(struct tty_struct *tty)
171 mutex_lock(&tty->throttle_mutex);
172 if (tty_throttled(tty)) {
173 if (tty->flow_change != TTY_UNTHROTTLE_SAFE)
176 clear_bit(TTY_THROTTLED, &tty->flags);
177 if (tty->ops->unthrottle)
178 tty->ops->unthrottle(tty);
181 mutex_unlock(&tty->throttle_mutex);
187 * tty_wait_until_sent - wait for I/O to finish
188 * @tty: tty we are waiting for
189 * @timeout: how long we will wait
191 * Wait for characters pending in a tty driver to hit the wire, or
192 * for a timeout to occur (eg due to flow control)
197 void tty_wait_until_sent(struct tty_struct *tty, long timeout)
199 tty_debug_wait_until_sent(tty, "wait until sent, timeout=%ld\n", timeout);
202 timeout = MAX_SCHEDULE_TIMEOUT;
204 timeout = wait_event_interruptible_timeout(tty->write_wait,
205 !tty_chars_in_buffer(tty), timeout);
209 if (timeout == MAX_SCHEDULE_TIMEOUT)
212 if (tty->ops->wait_until_sent)
213 tty->ops->wait_until_sent(tty, timeout);
215 EXPORT_SYMBOL(tty_wait_until_sent);
219 * Termios Helper Methods
222 static void unset_locked_termios(struct tty_struct *tty, struct ktermios *old)
224 struct ktermios *termios = &tty->termios;
225 struct ktermios *locked = &tty->termios_locked;
228 #define NOSET_MASK(x, y, z) (x = ((x) & ~(z)) | ((y) & (z)))
230 NOSET_MASK(termios->c_iflag, old->c_iflag, locked->c_iflag);
231 NOSET_MASK(termios->c_oflag, old->c_oflag, locked->c_oflag);
232 NOSET_MASK(termios->c_cflag, old->c_cflag, locked->c_cflag);
233 NOSET_MASK(termios->c_lflag, old->c_lflag, locked->c_lflag);
234 termios->c_line = locked->c_line ? old->c_line : termios->c_line;
235 for (i = 0; i < NCCS; i++)
236 termios->c_cc[i] = locked->c_cc[i] ?
237 old->c_cc[i] : termios->c_cc[i];
238 /* FIXME: What should we do for i/ospeed */
242 * tty_termios_copy_hw - copy hardware settings
246 * Propagate the hardware specific terminal setting bits from
247 * the old termios structure to the new one. This is used in cases
248 * where the hardware does not support reconfiguration or as a helper
249 * in some cases where only minimal reconfiguration is supported
252 void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old)
254 /* The bits a dumb device handles in software. Smart devices need
255 to always provide a set_termios method */
256 new->c_cflag &= HUPCL | CREAD | CLOCAL;
257 new->c_cflag |= old->c_cflag & ~(HUPCL | CREAD | CLOCAL);
258 new->c_ispeed = old->c_ispeed;
259 new->c_ospeed = old->c_ospeed;
261 EXPORT_SYMBOL(tty_termios_copy_hw);
264 * tty_termios_hw_change - check for setting change
266 * @b: termios to compare
268 * Check if any of the bits that affect a dumb device have changed
269 * between the two termios structures, or a speed change is needed.
272 int tty_termios_hw_change(const struct ktermios *a, const struct ktermios *b)
274 if (a->c_ispeed != b->c_ispeed || a->c_ospeed != b->c_ospeed)
276 if ((a->c_cflag ^ b->c_cflag) & ~(HUPCL | CREAD | CLOCAL))
280 EXPORT_SYMBOL(tty_termios_hw_change);
283 * tty_get_char_size - get size of a character
284 * @cflag: termios cflag value
286 * Get the size (in bits) of a character depending on @cflag's %CSIZE
289 unsigned char tty_get_char_size(unsigned int cflag)
291 switch (cflag & CSIZE) {
303 EXPORT_SYMBOL_GPL(tty_get_char_size);
306 * tty_get_frame_size - get size of a frame
307 * @cflag: termios cflag value
309 * Get the size (in bits) of a frame depending on @cflag's %CSIZE, %CSTOPB,
310 * and %PARENB setting. The result is a sum of character size, start and
311 * stop bits -- one bit each -- second stop bit (if set), and parity bit
314 unsigned char tty_get_frame_size(unsigned int cflag)
316 unsigned char bits = 2 + tty_get_char_size(cflag);
327 EXPORT_SYMBOL_GPL(tty_get_frame_size);
330 * tty_set_termios - update termios values
331 * @tty: tty to update
332 * @new_termios: desired new value
334 * Perform updates to the termios values set on this terminal.
335 * A master pty's termios should never be set.
337 * Locking: termios_rwsem
340 int tty_set_termios(struct tty_struct *tty, struct ktermios *new_termios)
342 struct ktermios old_termios;
343 struct tty_ldisc *ld;
345 WARN_ON(tty->driver->type == TTY_DRIVER_TYPE_PTY &&
346 tty->driver->subtype == PTY_TYPE_MASTER);
348 * Perform the actual termios internal changes under lock.
352 /* FIXME: we need to decide on some locking/ordering semantics
353 for the set_termios notification eventually */
354 down_write(&tty->termios_rwsem);
355 old_termios = tty->termios;
356 tty->termios = *new_termios;
357 unset_locked_termios(tty, &old_termios);
358 /* Reset any ADDRB changes, ADDRB is changed through ->rs485_config() */
359 tty->termios.c_cflag ^= (tty->termios.c_cflag ^ old_termios.c_cflag) & ADDRB;
361 if (tty->ops->set_termios)
362 tty->ops->set_termios(tty, &old_termios);
364 tty_termios_copy_hw(&tty->termios, &old_termios);
366 ld = tty_ldisc_ref(tty);
368 if (ld->ops->set_termios)
369 ld->ops->set_termios(tty, &old_termios);
372 up_write(&tty->termios_rwsem);
375 EXPORT_SYMBOL_GPL(tty_set_termios);
378 * set_termios - set termios values for a tty
379 * @tty: terminal device
381 * @opt: option information
383 * Helper function to prepare termios data and run necessary other
384 * functions before using tty_set_termios to do the actual changes.
387 * Called functions take ldisc and termios_rwsem locks
390 static int set_termios(struct tty_struct *tty, void __user *arg, int opt)
392 struct ktermios tmp_termios;
393 struct tty_ldisc *ld;
394 int retval = tty_check_change(tty);
399 down_read(&tty->termios_rwsem);
400 tmp_termios = tty->termios;
401 up_read(&tty->termios_rwsem);
403 if (opt & TERMIOS_TERMIO) {
404 if (user_termio_to_kernel_termios(&tmp_termios,
405 (struct termio __user *)arg))
408 } else if (opt & TERMIOS_OLD) {
409 if (user_termios_to_kernel_termios_1(&tmp_termios,
410 (struct termios __user *)arg))
413 if (user_termios_to_kernel_termios(&tmp_termios,
414 (struct termios2 __user *)arg))
418 } else if (user_termios_to_kernel_termios(&tmp_termios,
419 (struct termios __user *)arg))
423 /* If old style Bfoo values are used then load c_ispeed/c_ospeed
424 * with the real speed so its unconditionally usable */
425 tmp_termios.c_ispeed = tty_termios_input_baud_rate(&tmp_termios);
426 tmp_termios.c_ospeed = tty_termios_baud_rate(&tmp_termios);
428 ld = tty_ldisc_ref(tty);
431 if ((opt & TERMIOS_FLUSH) && ld->ops->flush_buffer)
432 ld->ops->flush_buffer(tty);
436 if (opt & TERMIOS_WAIT) {
437 tty_wait_until_sent(tty, 0);
438 if (signal_pending(current))
442 tty_set_termios(tty, &tmp_termios);
444 /* FIXME: Arguably if tmp_termios == tty->termios AND the
445 actual requested termios was not tmp_termios then we may
446 want to return an error as no user requested change has
451 static void copy_termios(struct tty_struct *tty, struct ktermios *kterm)
453 down_read(&tty->termios_rwsem);
454 *kterm = tty->termios;
455 up_read(&tty->termios_rwsem);
458 static void copy_termios_locked(struct tty_struct *tty, struct ktermios *kterm)
460 down_read(&tty->termios_rwsem);
461 *kterm = tty->termios_locked;
462 up_read(&tty->termios_rwsem);
465 static int get_termio(struct tty_struct *tty, struct termio __user *termio)
467 struct ktermios kterm;
468 copy_termios(tty, &kterm);
469 if (kernel_termios_to_user_termio(termio, &kterm))
476 * These are deprecated, but there is limited support..
478 * The "sg_flags" translation is a joke..
480 static int get_sgflags(struct tty_struct *tty)
484 if (!L_ICANON(tty)) {
486 flags |= 0x02; /* cbreak */
488 flags |= 0x20; /* raw */
491 flags |= 0x08; /* echo */
494 flags |= 0x10; /* crmod */
498 static int get_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
502 down_read(&tty->termios_rwsem);
503 tmp.sg_ispeed = tty->termios.c_ispeed;
504 tmp.sg_ospeed = tty->termios.c_ospeed;
505 tmp.sg_erase = tty->termios.c_cc[VERASE];
506 tmp.sg_kill = tty->termios.c_cc[VKILL];
507 tmp.sg_flags = get_sgflags(tty);
508 up_read(&tty->termios_rwsem);
510 return copy_to_user(sgttyb, &tmp, sizeof(tmp)) ? -EFAULT : 0;
513 static void set_sgflags(struct ktermios *termios, int flags)
515 termios->c_iflag = ICRNL | IXON;
516 termios->c_oflag = 0;
517 termios->c_lflag = ISIG | ICANON;
518 if (flags & 0x02) { /* cbreak */
519 termios->c_iflag = 0;
520 termios->c_lflag &= ~ICANON;
522 if (flags & 0x08) { /* echo */
523 termios->c_lflag |= ECHO | ECHOE | ECHOK |
524 ECHOCTL | ECHOKE | IEXTEN;
526 if (flags & 0x10) { /* crmod */
527 termios->c_oflag |= OPOST | ONLCR;
529 if (flags & 0x20) { /* raw */
530 termios->c_iflag = 0;
531 termios->c_lflag &= ~(ISIG | ICANON);
533 if (!(termios->c_lflag & ICANON)) {
534 termios->c_cc[VMIN] = 1;
535 termios->c_cc[VTIME] = 0;
540 * set_sgttyb - set legacy terminal values
541 * @tty: tty structure
542 * @sgttyb: pointer to old style terminal structure
544 * Updates a terminal from the legacy BSD style terminal information
547 * Locking: termios_rwsem
550 static int set_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
554 struct ktermios termios;
556 retval = tty_check_change(tty);
560 if (copy_from_user(&tmp, sgttyb, sizeof(tmp)))
563 down_write(&tty->termios_rwsem);
564 termios = tty->termios;
565 termios.c_cc[VERASE] = tmp.sg_erase;
566 termios.c_cc[VKILL] = tmp.sg_kill;
567 set_sgflags(&termios, tmp.sg_flags);
568 /* Try and encode into Bfoo format */
569 tty_termios_encode_baud_rate(&termios, termios.c_ispeed,
571 up_write(&tty->termios_rwsem);
572 tty_set_termios(tty, &termios);
578 static int get_tchars(struct tty_struct *tty, struct tchars __user *tchars)
582 down_read(&tty->termios_rwsem);
583 tmp.t_intrc = tty->termios.c_cc[VINTR];
584 tmp.t_quitc = tty->termios.c_cc[VQUIT];
585 tmp.t_startc = tty->termios.c_cc[VSTART];
586 tmp.t_stopc = tty->termios.c_cc[VSTOP];
587 tmp.t_eofc = tty->termios.c_cc[VEOF];
588 tmp.t_brkc = tty->termios.c_cc[VEOL2]; /* what is brkc anyway? */
589 up_read(&tty->termios_rwsem);
590 return copy_to_user(tchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
593 static int set_tchars(struct tty_struct *tty, struct tchars __user *tchars)
597 if (copy_from_user(&tmp, tchars, sizeof(tmp)))
599 down_write(&tty->termios_rwsem);
600 tty->termios.c_cc[VINTR] = tmp.t_intrc;
601 tty->termios.c_cc[VQUIT] = tmp.t_quitc;
602 tty->termios.c_cc[VSTART] = tmp.t_startc;
603 tty->termios.c_cc[VSTOP] = tmp.t_stopc;
604 tty->termios.c_cc[VEOF] = tmp.t_eofc;
605 tty->termios.c_cc[VEOL2] = tmp.t_brkc; /* what is brkc anyway? */
606 up_write(&tty->termios_rwsem);
612 static int get_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
616 down_read(&tty->termios_rwsem);
617 tmp.t_suspc = tty->termios.c_cc[VSUSP];
618 /* what is dsuspc anyway? */
619 tmp.t_dsuspc = tty->termios.c_cc[VSUSP];
620 tmp.t_rprntc = tty->termios.c_cc[VREPRINT];
621 /* what is flushc anyway? */
622 tmp.t_flushc = tty->termios.c_cc[VEOL2];
623 tmp.t_werasc = tty->termios.c_cc[VWERASE];
624 tmp.t_lnextc = tty->termios.c_cc[VLNEXT];
625 up_read(&tty->termios_rwsem);
626 return copy_to_user(ltchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
629 static int set_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
633 if (copy_from_user(&tmp, ltchars, sizeof(tmp)))
636 down_write(&tty->termios_rwsem);
637 tty->termios.c_cc[VSUSP] = tmp.t_suspc;
638 /* what is dsuspc anyway? */
639 tty->termios.c_cc[VEOL2] = tmp.t_dsuspc;
640 tty->termios.c_cc[VREPRINT] = tmp.t_rprntc;
641 /* what is flushc anyway? */
642 tty->termios.c_cc[VEOL2] = tmp.t_flushc;
643 tty->termios.c_cc[VWERASE] = tmp.t_werasc;
644 tty->termios.c_cc[VLNEXT] = tmp.t_lnextc;
645 up_write(&tty->termios_rwsem);
651 * tty_change_softcar - carrier change ioctl helper
652 * @tty: tty to update
653 * @arg: enable/disable CLOCAL
655 * Perform a change to the CLOCAL state and call into the driver
656 * layer to make it visible. All done with the termios rwsem
659 static int tty_change_softcar(struct tty_struct *tty, int arg)
662 int bit = arg ? CLOCAL : 0;
665 down_write(&tty->termios_rwsem);
667 tty->termios.c_cflag &= ~CLOCAL;
668 tty->termios.c_cflag |= bit;
669 if (tty->ops->set_termios)
670 tty->ops->set_termios(tty, &old);
671 if (C_CLOCAL(tty) != bit)
673 up_write(&tty->termios_rwsem);
678 * tty_mode_ioctl - mode related ioctls
679 * @tty: tty for the ioctl
681 * @arg: ioctl argument
683 * Perform non line discipline specific mode control ioctls. This
684 * is designed to be called by line disciplines to ensure they provide
685 * consistent mode setting.
688 int tty_mode_ioctl(struct tty_struct *tty, unsigned int cmd, unsigned long arg)
690 struct tty_struct *real_tty;
691 void __user *p = (void __user *)arg;
693 struct ktermios kterm;
695 if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
696 tty->driver->subtype == PTY_TYPE_MASTER)
697 real_tty = tty->link;
704 return get_sgttyb(real_tty, (struct sgttyb __user *) arg);
707 return set_sgttyb(real_tty, (struct sgttyb __user *) arg);
711 return get_tchars(real_tty, p);
713 return set_tchars(real_tty, p);
717 return get_ltchars(real_tty, p);
719 return set_ltchars(real_tty, p);
722 return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_OLD);
724 return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_OLD);
726 return set_termios(real_tty, p, TERMIOS_OLD);
729 copy_termios(real_tty, &kterm);
730 if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
735 copy_termios(real_tty, &kterm);
736 if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
740 copy_termios(real_tty, &kterm);
741 if (kernel_termios_to_user_termios((struct termios2 __user *)arg, &kterm))
745 return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT);
747 return set_termios(real_tty, p, TERMIOS_WAIT);
749 return set_termios(real_tty, p, 0);
752 return get_termio(real_tty, p);
754 return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_TERMIO);
756 return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_TERMIO);
758 return set_termios(real_tty, p, TERMIOS_TERMIO);
761 copy_termios_locked(real_tty, &kterm);
762 if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
766 if (!capable(CAP_SYS_ADMIN))
768 copy_termios_locked(real_tty, &kterm);
769 if (user_termios_to_kernel_termios(&kterm,
770 (struct termios __user *) arg))
772 down_write(&real_tty->termios_rwsem);
773 real_tty->termios_locked = kterm;
774 up_write(&real_tty->termios_rwsem);
778 copy_termios_locked(real_tty, &kterm);
779 if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
783 if (!capable(CAP_SYS_ADMIN))
785 copy_termios_locked(real_tty, &kterm);
786 if (user_termios_to_kernel_termios_1(&kterm,
787 (struct termios __user *) arg))
789 down_write(&real_tty->termios_rwsem);
790 real_tty->termios_locked = kterm;
791 up_write(&real_tty->termios_rwsem);
802 copy_termios(real_tty, &kterm);
803 ret = put_user((kterm.c_cflag & CLOCAL) ? 1 : 0,
807 if (get_user(arg, (unsigned int __user *) arg))
809 return tty_change_softcar(real_tty, arg);
814 EXPORT_SYMBOL_GPL(tty_mode_ioctl);
817 /* Caller guarantees ldisc reference is held */
818 static int __tty_perform_flush(struct tty_struct *tty, unsigned long arg)
820 struct tty_ldisc *ld = tty->ldisc;
824 if (ld && ld->ops->flush_buffer) {
825 ld->ops->flush_buffer(tty);
830 if (ld && ld->ops->flush_buffer) {
831 ld->ops->flush_buffer(tty);
836 tty_driver_flush_buffer(tty);
844 int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
846 struct tty_ldisc *ld;
847 int retval = tty_check_change(tty);
851 ld = tty_ldisc_ref_wait(tty);
852 retval = __tty_perform_flush(tty, arg);
857 EXPORT_SYMBOL_GPL(tty_perform_flush);
859 int n_tty_ioctl_helper(struct tty_struct *tty, unsigned int cmd,
866 retval = tty_check_change(tty);
871 spin_lock_irq(&tty->flow.lock);
872 if (!tty->flow.tco_stopped) {
873 tty->flow.tco_stopped = true;
876 spin_unlock_irq(&tty->flow.lock);
879 spin_lock_irq(&tty->flow.lock);
880 if (tty->flow.tco_stopped) {
881 tty->flow.tco_stopped = false;
884 spin_unlock_irq(&tty->flow.lock);
887 if (STOP_CHAR(tty) != __DISABLED_CHAR)
888 retval = tty_send_xchar(tty, STOP_CHAR(tty));
891 if (START_CHAR(tty) != __DISABLED_CHAR)
892 retval = tty_send_xchar(tty, START_CHAR(tty));
899 retval = tty_check_change(tty);
902 return __tty_perform_flush(tty, arg);
904 /* Try the mode commands */
905 return tty_mode_ioctl(tty, cmd, arg);
908 EXPORT_SYMBOL(n_tty_ioctl_helper);