1 #include <linux/types.h>
2 #include <linux/major.h>
3 #include <linux/errno.h>
4 #include <linux/signal.h>
5 #include <linux/fcntl.h>
6 #include <linux/sched.h>
7 #include <linux/interrupt.h>
9 #include <linux/tty_driver.h>
10 #include <linux/tty_flip.h>
11 #include <linux/devpts_fs.h>
12 #include <linux/file.h>
13 #include <linux/console.h>
14 #include <linux/timer.h>
15 #include <linux/ctype.h>
18 #include <linux/string.h>
19 #include <linux/slab.h>
20 #include <linux/poll.h>
21 #include <linux/proc_fs.h>
22 #include <linux/init.h>
23 #include <linux/module.h>
24 #include <linux/smp_lock.h>
25 #include <linux/device.h>
26 #include <linux/wait.h>
27 #include <linux/bitops.h>
28 #include <linux/delay.h>
29 #include <linux/seq_file.h>
31 #include <linux/uaccess.h>
32 #include <asm/system.h>
34 #include <linux/kbd_kern.h>
35 #include <linux/vt_kern.h>
36 #include <linux/selection.h>
38 #include <linux/kmod.h>
39 #include <linux/nsproxy.h>
42 * This guards the refcounted line discipline lists. The lock
43 * must be taken with irqs off because there are hangup path
44 * callers who will do ldisc lookups and cannot sleep.
47 static DEFINE_SPINLOCK(tty_ldisc_lock
);
48 static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait
);
49 /* Line disc dispatch table */
50 static struct tty_ldisc_ops
*tty_ldiscs
[NR_LDISCS
];
53 * tty_register_ldisc - install a line discipline
55 * @new_ldisc: pointer to the ldisc object
57 * Installs a new line discipline into the kernel. The discipline
58 * is set up as unreferenced and then made available to the kernel
59 * from this point onwards.
62 * takes tty_ldisc_lock to guard against ldisc races
65 int tty_register_ldisc(int disc
, struct tty_ldisc_ops
*new_ldisc
)
70 if (disc
< N_TTY
|| disc
>= NR_LDISCS
)
73 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
74 tty_ldiscs
[disc
] = new_ldisc
;
75 new_ldisc
->num
= disc
;
76 new_ldisc
->refcount
= 0;
77 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
81 EXPORT_SYMBOL(tty_register_ldisc
);
84 * tty_unregister_ldisc - unload a line discipline
86 * @new_ldisc: pointer to the ldisc object
88 * Remove a line discipline from the kernel providing it is not
92 * takes tty_ldisc_lock to guard against ldisc races
95 int tty_unregister_ldisc(int disc
)
100 if (disc
< N_TTY
|| disc
>= NR_LDISCS
)
103 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
104 if (tty_ldiscs
[disc
]->refcount
)
107 tty_ldiscs
[disc
] = NULL
;
108 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
112 EXPORT_SYMBOL(tty_unregister_ldisc
);
116 * tty_ldisc_try_get - try and reference an ldisc
117 * @disc: ldisc number
119 * Attempt to open and lock a line discipline into place. Return
120 * the line discipline refcounted or an error.
123 static struct tty_ldisc
*tty_ldisc_try_get(int disc
)
126 struct tty_ldisc
*ld
;
127 struct tty_ldisc_ops
*ldops
;
130 ld
= kmalloc(sizeof(struct tty_ldisc
), GFP_KERNEL
);
132 return ERR_PTR(-ENOMEM
);
134 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
136 ldops
= tty_ldiscs
[disc
];
137 /* Check the entry is defined */
139 /* If the module is being unloaded we can't use it */
140 if (!try_module_get(ldops
->owner
))
150 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
157 * tty_ldisc_get - take a reference to an ldisc
158 * @disc: ldisc number
160 * Takes a reference to a line discipline. Deals with refcounts and
161 * module locking counts. Returns NULL if the discipline is not available.
162 * Returns a pointer to the discipline and bumps the ref count if it is
166 * takes tty_ldisc_lock to guard against ldisc races
169 static struct tty_ldisc
*tty_ldisc_get(int disc
)
171 struct tty_ldisc
*ld
;
173 if (disc
< N_TTY
|| disc
>= NR_LDISCS
)
174 return ERR_PTR(-EINVAL
);
175 ld
= tty_ldisc_try_get(disc
);
177 request_module("tty-ldisc-%d", disc
);
178 ld
= tty_ldisc_try_get(disc
);
184 * tty_ldisc_put - drop ldisc reference
187 * Drop a reference to a line discipline. Manage refcounts and
188 * module usage counts. Free the ldisc once the recount hits zero.
191 * takes tty_ldisc_lock to guard against ldisc races
194 static void tty_ldisc_put(struct tty_ldisc
*ld
)
197 int disc
= ld
->ops
->num
;
198 struct tty_ldisc_ops
*ldo
;
200 BUG_ON(disc
< N_TTY
|| disc
>= NR_LDISCS
);
202 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
203 ldo
= tty_ldiscs
[disc
];
204 BUG_ON(ldo
->refcount
== 0);
206 module_put(ldo
->owner
);
207 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
211 static void *tty_ldiscs_seq_start(struct seq_file
*m
, loff_t
*pos
)
213 return (*pos
< NR_LDISCS
) ? pos
: NULL
;
216 static void *tty_ldiscs_seq_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
219 return (*pos
< NR_LDISCS
) ? pos
: NULL
;
222 static void tty_ldiscs_seq_stop(struct seq_file
*m
, void *v
)
226 static int tty_ldiscs_seq_show(struct seq_file
*m
, void *v
)
228 int i
= *(loff_t
*)v
;
229 struct tty_ldisc
*ld
;
231 ld
= tty_ldisc_try_get(i
);
234 seq_printf(m
, "%-10s %2d\n", ld
->ops
->name
? ld
->ops
->name
: "???", i
);
239 static const struct seq_operations tty_ldiscs_seq_ops
= {
240 .start
= tty_ldiscs_seq_start
,
241 .next
= tty_ldiscs_seq_next
,
242 .stop
= tty_ldiscs_seq_stop
,
243 .show
= tty_ldiscs_seq_show
,
246 static int proc_tty_ldiscs_open(struct inode
*inode
, struct file
*file
)
248 return seq_open(file
, &tty_ldiscs_seq_ops
);
251 const struct file_operations tty_ldiscs_proc_fops
= {
252 .owner
= THIS_MODULE
,
253 .open
= proc_tty_ldiscs_open
,
256 .release
= seq_release
,
260 * tty_ldisc_assign - set ldisc on a tty
261 * @tty: tty to assign
262 * @ld: line discipline
264 * Install an instance of a line discipline into a tty structure. The
265 * ldisc must have a reference count above zero to ensure it remains/
266 * The tty instance refcount starts at zero.
269 * Caller must hold references
272 static void tty_ldisc_assign(struct tty_struct
*tty
, struct tty_ldisc
*ld
)
278 * tty_ldisc_try - internal helper
281 * Make a single attempt to grab and bump the refcount on
282 * the tty ldisc. Return 0 on failure or 1 on success. This is
283 * used to implement both the waiting and non waiting versions
286 * Locking: takes tty_ldisc_lock
289 static int tty_ldisc_try(struct tty_struct
*tty
)
292 struct tty_ldisc
*ld
;
295 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
297 if (test_bit(TTY_LDISC
, &tty
->flags
)) {
301 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
306 * tty_ldisc_ref_wait - wait for the tty ldisc
309 * Dereference the line discipline for the terminal and take a
310 * reference to it. If the line discipline is in flux then
311 * wait patiently until it changes.
313 * Note: Must not be called from an IRQ/timer context. The caller
314 * must also be careful not to hold other locks that will deadlock
315 * against a discipline change, such as an existing ldisc reference
316 * (which we check for)
318 * Locking: call functions take tty_ldisc_lock
321 struct tty_ldisc
*tty_ldisc_ref_wait(struct tty_struct
*tty
)
323 /* wait_event is a macro */
324 wait_event(tty_ldisc_wait
, tty_ldisc_try(tty
));
325 WARN_ON(tty
->ldisc
->refcount
== 0);
328 EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait
);
331 * tty_ldisc_ref - get the tty ldisc
334 * Dereference the line discipline for the terminal and take a
335 * reference to it. If the line discipline is in flux then
336 * return NULL. Can be called from IRQ and timer functions.
338 * Locking: called functions take tty_ldisc_lock
341 struct tty_ldisc
*tty_ldisc_ref(struct tty_struct
*tty
)
343 if (tty_ldisc_try(tty
))
347 EXPORT_SYMBOL_GPL(tty_ldisc_ref
);
350 * tty_ldisc_deref - free a tty ldisc reference
351 * @ld: reference to free up
353 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
354 * be called in IRQ context.
356 * Locking: takes tty_ldisc_lock
359 void tty_ldisc_deref(struct tty_ldisc
*ld
)
365 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
366 if (ld
->refcount
== 0)
367 printk(KERN_ERR
"tty_ldisc_deref: no references.\n");
370 if (ld
->refcount
== 0)
371 wake_up(&tty_ldisc_wait
);
372 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
374 EXPORT_SYMBOL_GPL(tty_ldisc_deref
);
377 * tty_ldisc_enable - allow ldisc use
378 * @tty: terminal to activate ldisc on
380 * Set the TTY_LDISC flag when the line discipline can be called
381 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
382 * changing flag to indicate any ldisc change is now over.
384 * Note: nobody should set the TTY_LDISC bit except via this function.
385 * Clearing directly is allowed.
388 void tty_ldisc_enable(struct tty_struct
*tty
)
390 set_bit(TTY_LDISC
, &tty
->flags
);
391 clear_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
392 wake_up(&tty_ldisc_wait
);
396 * tty_ldisc_flush - flush line discipline queue
399 * Flush the line discipline queue (if any) for this tty. If there
400 * is no line discipline active this is a no-op.
403 void tty_ldisc_flush(struct tty_struct
*tty
)
405 struct tty_ldisc
*ld
= tty_ldisc_ref(tty
);
407 if (ld
->ops
->flush_buffer
)
408 ld
->ops
->flush_buffer(tty
);
411 tty_buffer_flush(tty
);
413 EXPORT_SYMBOL_GPL(tty_ldisc_flush
);
416 * tty_set_termios_ldisc - set ldisc field
417 * @tty: tty structure
418 * @num: line discipline number
420 * This is probably overkill for real world processors but
421 * they are not on hot paths so a little discipline won't do
424 * Locking: takes termios_mutex
427 static void tty_set_termios_ldisc(struct tty_struct
*tty
, int num
)
429 mutex_lock(&tty
->termios_mutex
);
430 tty
->termios
->c_line
= num
;
431 mutex_unlock(&tty
->termios_mutex
);
435 * tty_ldisc_open - open a line discipline
436 * @tty: tty we are opening the ldisc on
437 * @ld: discipline to open
439 * A helper opening method. Also a convenient debugging and check
443 static int tty_ldisc_open(struct tty_struct
*tty
, struct tty_ldisc
*ld
)
445 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN
, &tty
->flags
));
447 return ld
->ops
->open(tty
);
452 * tty_ldisc_close - close a line discipline
453 * @tty: tty we are opening the ldisc on
454 * @ld: discipline to close
456 * A helper close method. Also a convenient debugging and check
460 static void tty_ldisc_close(struct tty_struct
*tty
, struct tty_ldisc
*ld
)
462 WARN_ON(!test_bit(TTY_LDISC_OPEN
, &tty
->flags
));
463 clear_bit(TTY_LDISC_OPEN
, &tty
->flags
);
469 * tty_ldisc_restore - helper for tty ldisc change
470 * @tty: tty to recover
471 * @old: previous ldisc
473 * Restore the previous line discipline or N_TTY when a line discipline
474 * change fails due to an open error
477 static void tty_ldisc_restore(struct tty_struct
*tty
, struct tty_ldisc
*old
)
480 struct tty_ldisc
*new_ldisc
;
483 /* There is an outstanding reference here so this is safe */
484 old
= tty_ldisc_get(old
->ops
->num
);
485 WARN_ON(IS_ERR(old
));
486 tty_ldisc_assign(tty
, old
);
487 tty_set_termios_ldisc(tty
, old
->ops
->num
);
488 if (tty_ldisc_open(tty
, old
) < 0) {
490 /* This driver is always present */
491 new_ldisc
= tty_ldisc_get(N_TTY
);
492 if (IS_ERR(new_ldisc
))
494 tty_ldisc_assign(tty
, new_ldisc
);
495 tty_set_termios_ldisc(tty
, N_TTY
);
496 r
= tty_ldisc_open(tty
, new_ldisc
);
498 panic("Couldn't open N_TTY ldisc for "
500 tty_name(tty
, buf
), r
);
505 * tty_ldisc_halt - shut down the line discipline
508 * Shut down the line discipline and work queue for this tty device.
509 * The TTY_LDISC flag being cleared ensures no further references can
510 * be obtained while the delayed work queue halt ensures that no more
511 * data is fed to the ldisc.
513 * In order to wait for any existing references to complete see
514 * tty_ldisc_wait_idle.
517 static int tty_ldisc_halt(struct tty_struct
*tty
)
519 clear_bit(TTY_LDISC
, &tty
->flags
);
520 return cancel_delayed_work(&tty
->buf
.work
);
524 * tty_ldisc_wait_idle - wait for the ldisc to become idle
525 * @tty: tty to wait for
527 * Wait for the line discipline to become idle. The discipline must
528 * have been halted for this to guarantee it remains idle.
530 * tty_ldisc_lock protects the ref counts currently.
533 static int tty_ldisc_wait_idle(struct tty_struct
*tty
)
536 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
537 while (tty
->ldisc
->refcount
) {
538 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
539 if (wait_event_timeout(tty_ldisc_wait
,
540 tty
->ldisc
->refcount
== 0, 5 * HZ
) == 0)
542 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
544 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
549 * tty_set_ldisc - set line discipline
550 * @tty: the terminal to set
551 * @ldisc: the line discipline
553 * Set the discipline of a tty line. Must be called from a process
554 * context. The ldisc change logic has to protect itself against any
555 * overlapping ldisc change (including on the other end of pty pairs),
556 * the close of one side of a tty/pty pair, and eventually hangup.
558 * Locking: takes tty_ldisc_lock, termios_mutex
561 int tty_set_ldisc(struct tty_struct
*tty
, int ldisc
)
564 struct tty_ldisc
*o_ldisc
, *new_ldisc
;
565 int work
, o_work
= 0;
566 struct tty_struct
*o_tty
;
568 new_ldisc
= tty_ldisc_get(ldisc
);
569 if (IS_ERR(new_ldisc
))
570 return PTR_ERR(new_ldisc
);
573 * We need to look at the tty locking here for pty/tty pairs
574 * when both sides try to change in parallel.
577 o_tty
= tty
->link
; /* o_tty is the pty side or NULL */
581 * Check the no-op case
584 if (tty
->ldisc
->ops
->num
== ldisc
) {
585 tty_ldisc_put(new_ldisc
);
590 * Problem: What do we do if this blocks ?
591 * We could deadlock here
594 tty_wait_until_sent(tty
, 0);
596 mutex_lock(&tty
->ldisc_mutex
);
599 * We could be midstream of another ldisc change which has
600 * dropped the lock during processing. If so we need to wait.
603 while (test_bit(TTY_LDISC_CHANGING
, &tty
->flags
)) {
604 mutex_unlock(&tty
->ldisc_mutex
);
605 wait_event(tty_ldisc_wait
,
606 test_bit(TTY_LDISC_CHANGING
, &tty
->flags
) == 0);
607 mutex_lock(&tty
->ldisc_mutex
);
609 set_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
612 * No more input please, we are switching. The new ldisc
613 * will update this value in the ldisc open function
616 tty
->receive_room
= 0;
618 o_ldisc
= tty
->ldisc
;
620 * Make sure we don't change while someone holds a
621 * reference to the line discipline. The TTY_LDISC bit
622 * prevents anyone taking a reference once it is clear.
623 * We need the lock to avoid racing reference takers.
625 * We must clear the TTY_LDISC bit here to avoid a livelock
626 * with a userspace app continually trying to use the tty in
627 * parallel to the change and re-referencing the tty.
630 work
= tty_ldisc_halt(tty
);
632 o_work
= tty_ldisc_halt(o_tty
);
635 * Wait for ->hangup_work and ->buf.work handlers to terminate.
636 * We must drop the mutex here in case a hangup is also in process.
639 mutex_unlock(&tty
->ldisc_mutex
);
641 flush_scheduled_work();
643 /* Let any existing reference holders finish */
644 retval
= tty_ldisc_wait_idle(tty
);
646 clear_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
647 tty_ldisc_put(new_ldisc
);
651 mutex_lock(&tty
->ldisc_mutex
);
652 if (test_bit(TTY_HUPPED
, &tty
->flags
)) {
653 /* We were raced by the hangup method. It will have stomped
654 the ldisc data and closed the ldisc down */
655 clear_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
656 mutex_unlock(&tty
->ldisc_mutex
);
657 tty_ldisc_put(new_ldisc
);
661 /* Shutdown the current discipline. */
662 tty_ldisc_close(tty
, o_ldisc
);
664 /* Now set up the new line discipline. */
665 tty_ldisc_assign(tty
, new_ldisc
);
666 tty_set_termios_ldisc(tty
, ldisc
);
668 retval
= tty_ldisc_open(tty
, new_ldisc
);
670 /* Back to the old one or N_TTY if we can't */
671 tty_ldisc_put(new_ldisc
);
672 tty_ldisc_restore(tty
, o_ldisc
);
675 /* At this point we hold a reference to the new ldisc and a
676 a reference to the old ldisc. If we ended up flipping back
677 to the existing ldisc we have two references to it */
679 if (tty
->ldisc
->ops
->num
!= o_ldisc
->ops
->num
&& tty
->ops
->set_ldisc
)
680 tty
->ops
->set_ldisc(tty
);
682 tty_ldisc_put(o_ldisc
);
685 * Allow ldisc referencing to occur again
688 tty_ldisc_enable(tty
);
690 tty_ldisc_enable(o_tty
);
692 /* Restart the work queue in case no characters kick it off. Safe if
695 schedule_delayed_work(&tty
->buf
.work
, 1);
697 schedule_delayed_work(&o_tty
->buf
.work
, 1);
698 mutex_unlock(&tty
->ldisc_mutex
);
703 * tty_reset_termios - reset terminal state
706 * Restore a terminal to the driver default state.
709 static void tty_reset_termios(struct tty_struct
*tty
)
711 mutex_lock(&tty
->termios_mutex
);
712 *tty
->termios
= tty
->driver
->init_termios
;
713 tty
->termios
->c_ispeed
= tty_termios_input_baud_rate(tty
->termios
);
714 tty
->termios
->c_ospeed
= tty_termios_baud_rate(tty
->termios
);
715 mutex_unlock(&tty
->termios_mutex
);
720 * tty_ldisc_reinit - reinitialise the tty ldisc
721 * @tty: tty to reinit
723 * Switch the tty back to N_TTY line discipline and leave the
727 static void tty_ldisc_reinit(struct tty_struct
*tty
)
729 struct tty_ldisc
*ld
;
731 tty_ldisc_close(tty
, tty
->ldisc
);
732 tty_ldisc_put(tty
->ldisc
);
735 * Switch the line discipline back
737 ld
= tty_ldisc_get(N_TTY
);
739 tty_ldisc_assign(tty
, ld
);
740 tty_set_termios_ldisc(tty
, N_TTY
);
744 * tty_ldisc_hangup - hangup ldisc reset
745 * @tty: tty being hung up
747 * Some tty devices reset their termios when they receive a hangup
748 * event. In that situation we must also switch back to N_TTY properly
749 * before we reset the termios data.
751 * Locking: We can take the ldisc mutex as the rest of the code is
752 * careful to allow for this.
754 * In the pty pair case this occurs in the close() path of the
755 * tty itself so we must be careful about locking rules.
758 void tty_ldisc_hangup(struct tty_struct
*tty
)
760 struct tty_ldisc
*ld
;
763 * FIXME! What are the locking issues here? This may me overdoing
764 * things... This question is especially important now that we've
765 * removed the irqlock.
767 ld
= tty_ldisc_ref(tty
);
769 /* We may have no line discipline at this point */
770 if (ld
->ops
->flush_buffer
)
771 ld
->ops
->flush_buffer(tty
);
772 tty_driver_flush_buffer(tty
);
773 if ((test_bit(TTY_DO_WRITE_WAKEUP
, &tty
->flags
)) &&
774 ld
->ops
->write_wakeup
)
775 ld
->ops
->write_wakeup(tty
);
777 ld
->ops
->hangup(tty
);
781 * FIXME: Once we trust the LDISC code better we can wait here for
782 * ldisc completion and fix the driver call race
784 wake_up_interruptible_poll(&tty
->write_wait
, POLLOUT
);
785 wake_up_interruptible_poll(&tty
->read_wait
, POLLIN
);
787 * Shutdown the current line discipline, and reset it to
790 if (tty
->driver
->flags
& TTY_DRIVER_RESET_TERMIOS
) {
791 /* Avoid racing set_ldisc */
792 mutex_lock(&tty
->ldisc_mutex
);
793 /* Switch back to N_TTY */
794 tty_ldisc_reinit(tty
);
795 /* At this point we have a closed ldisc and we want to
796 reopen it. We could defer this to the next open but
797 it means auditing a lot of other paths so this is a FIXME */
798 WARN_ON(tty_ldisc_open(tty
, tty
->ldisc
));
799 tty_ldisc_enable(tty
);
800 mutex_unlock(&tty
->ldisc_mutex
);
801 tty_reset_termios(tty
);
806 * tty_ldisc_setup - open line discipline
807 * @tty: tty being shut down
808 * @o_tty: pair tty for pty/tty pairs
810 * Called during the initial open of a tty/pty pair in order to set up the
811 * line disciplines and bind them to the tty. This has no locking issues
812 * as the device isn't yet active.
815 int tty_ldisc_setup(struct tty_struct
*tty
, struct tty_struct
*o_tty
)
817 struct tty_ldisc
*ld
= tty
->ldisc
;
820 retval
= tty_ldisc_open(tty
, ld
);
825 retval
= tty_ldisc_open(o_tty
, o_tty
->ldisc
);
827 tty_ldisc_close(tty
, ld
);
830 tty_ldisc_enable(o_tty
);
832 tty_ldisc_enable(tty
);
836 * tty_ldisc_release - release line discipline
837 * @tty: tty being shut down
838 * @o_tty: pair tty for pty/tty pairs
840 * Called during the final close of a tty/pty pair in order to shut down
841 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
842 * ldisc has not been opened.
845 void tty_ldisc_release(struct tty_struct
*tty
, struct tty_struct
*o_tty
)
848 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
849 * kill any delayed work. As this is the final close it does not
850 * race with the set_ldisc code path.
854 flush_scheduled_work();
857 * Wait for any short term users (we know they are just driver
858 * side waiters as the file is closing so user count on the file
862 tty_ldisc_wait_idle(tty
);
865 * Shutdown the current line discipline, and reset it to N_TTY.
867 * FIXME: this MUST get fixed for the new reflocking
870 tty_ldisc_reinit(tty
);
871 /* This will need doing differently if we need to lock */
873 tty_ldisc_release(o_tty
, NULL
);
877 * tty_ldisc_init - ldisc setup for new tty
878 * @tty: tty being allocated
880 * Set up the line discipline objects for a newly allocated tty. Note that
881 * the tty structure is not completely set up when this call is made.
884 void tty_ldisc_init(struct tty_struct
*tty
)
886 struct tty_ldisc
*ld
= tty_ldisc_get(N_TTY
);
888 panic("n_tty: init_tty");
889 tty_ldisc_assign(tty
, ld
);
892 void tty_ldisc_begin(void)
894 /* Setup the default TTY line discipline. */
895 (void) tty_register_ldisc(N_TTY
, &tty_ldisc_N_TTY
);