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/device.h>
25 #include <linux/wait.h>
26 #include <linux/bitops.h>
27 #include <linux/delay.h>
28 #include <linux/seq_file.h>
30 #include <linux/uaccess.h>
31 #include <asm/system.h>
33 #include <linux/kbd_kern.h>
34 #include <linux/vt_kern.h>
35 #include <linux/selection.h>
37 #include <linux/kmod.h>
38 #include <linux/nsproxy.h>
41 * This guards the refcounted line discipline lists. The lock
42 * must be taken with irqs off because there are hangup path
43 * callers who will do ldisc lookups and cannot sleep.
46 static DEFINE_SPINLOCK(tty_ldisc_lock
);
47 static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait
);
48 /* Line disc dispatch table */
49 static struct tty_ldisc_ops
*tty_ldiscs
[NR_LDISCS
];
51 static inline struct tty_ldisc
*get_ldisc(struct tty_ldisc
*ld
)
54 atomic_inc(&ld
->users
);
58 static void put_ldisc(struct tty_ldisc
*ld
)
62 if (WARN_ON_ONCE(!ld
))
66 * If this is the last user, free the ldisc, and
67 * release the ldisc ops.
69 * We really want an "atomic_dec_and_lock_irqsave()",
70 * but we don't have it, so this does it by hand.
72 local_irq_save(flags
);
73 if (atomic_dec_and_lock(&ld
->users
, &tty_ldisc_lock
)) {
74 struct tty_ldisc_ops
*ldo
= ld
->ops
;
77 module_put(ldo
->owner
);
78 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
83 local_irq_restore(flags
);
87 * tty_register_ldisc - install a line discipline
89 * @new_ldisc: pointer to the ldisc object
91 * Installs a new line discipline into the kernel. The discipline
92 * is set up as unreferenced and then made available to the kernel
93 * from this point onwards.
96 * takes tty_ldisc_lock to guard against ldisc races
99 int tty_register_ldisc(int disc
, struct tty_ldisc_ops
*new_ldisc
)
104 if (disc
< N_TTY
|| disc
>= NR_LDISCS
)
107 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
108 tty_ldiscs
[disc
] = new_ldisc
;
109 new_ldisc
->num
= disc
;
110 new_ldisc
->refcount
= 0;
111 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
115 EXPORT_SYMBOL(tty_register_ldisc
);
118 * tty_unregister_ldisc - unload a line discipline
119 * @disc: ldisc number
120 * @new_ldisc: pointer to the ldisc object
122 * Remove a line discipline from the kernel providing it is not
126 * takes tty_ldisc_lock to guard against ldisc races
129 int tty_unregister_ldisc(int disc
)
134 if (disc
< N_TTY
|| disc
>= NR_LDISCS
)
137 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
138 if (tty_ldiscs
[disc
]->refcount
)
141 tty_ldiscs
[disc
] = NULL
;
142 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
146 EXPORT_SYMBOL(tty_unregister_ldisc
);
148 static struct tty_ldisc_ops
*get_ldops(int disc
)
151 struct tty_ldisc_ops
*ldops
, *ret
;
153 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
154 ret
= ERR_PTR(-EINVAL
);
155 ldops
= tty_ldiscs
[disc
];
157 ret
= ERR_PTR(-EAGAIN
);
158 if (try_module_get(ldops
->owner
)) {
163 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
167 static void put_ldops(struct tty_ldisc_ops
*ldops
)
171 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
173 module_put(ldops
->owner
);
174 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
178 * tty_ldisc_try_get - try and reference an ldisc
179 * @disc: ldisc number
181 * Attempt to open and lock a line discipline into place. Return
182 * the line discipline refcounted or an error.
185 static struct tty_ldisc
*tty_ldisc_try_get(int disc
)
187 struct tty_ldisc
*ld
;
188 struct tty_ldisc_ops
*ldops
;
190 ld
= kmalloc(sizeof(struct tty_ldisc
), GFP_KERNEL
);
192 return ERR_PTR(-ENOMEM
);
194 ldops
= get_ldops(disc
);
197 return ERR_CAST(ldops
);
201 atomic_set(&ld
->users
, 1);
206 * tty_ldisc_get - take a reference to an ldisc
207 * @disc: ldisc number
209 * Takes a reference to a line discipline. Deals with refcounts and
210 * module locking counts. Returns NULL if the discipline is not available.
211 * Returns a pointer to the discipline and bumps the ref count if it is
215 * takes tty_ldisc_lock to guard against ldisc races
218 static struct tty_ldisc
*tty_ldisc_get(int disc
)
220 struct tty_ldisc
*ld
;
222 if (disc
< N_TTY
|| disc
>= NR_LDISCS
)
223 return ERR_PTR(-EINVAL
);
224 ld
= tty_ldisc_try_get(disc
);
226 request_module("tty-ldisc-%d", disc
);
227 ld
= tty_ldisc_try_get(disc
);
232 static void *tty_ldiscs_seq_start(struct seq_file
*m
, loff_t
*pos
)
234 return (*pos
< NR_LDISCS
) ? pos
: NULL
;
237 static void *tty_ldiscs_seq_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
240 return (*pos
< NR_LDISCS
) ? pos
: NULL
;
243 static void tty_ldiscs_seq_stop(struct seq_file
*m
, void *v
)
247 static int tty_ldiscs_seq_show(struct seq_file
*m
, void *v
)
249 int i
= *(loff_t
*)v
;
250 struct tty_ldisc_ops
*ldops
;
252 ldops
= get_ldops(i
);
255 seq_printf(m
, "%-10s %2d\n", ldops
->name
? ldops
->name
: "???", i
);
260 static const struct seq_operations tty_ldiscs_seq_ops
= {
261 .start
= tty_ldiscs_seq_start
,
262 .next
= tty_ldiscs_seq_next
,
263 .stop
= tty_ldiscs_seq_stop
,
264 .show
= tty_ldiscs_seq_show
,
267 static int proc_tty_ldiscs_open(struct inode
*inode
, struct file
*file
)
269 return seq_open(file
, &tty_ldiscs_seq_ops
);
272 const struct file_operations tty_ldiscs_proc_fops
= {
273 .owner
= THIS_MODULE
,
274 .open
= proc_tty_ldiscs_open
,
277 .release
= seq_release
,
281 * tty_ldisc_assign - set ldisc on a tty
282 * @tty: tty to assign
283 * @ld: line discipline
285 * Install an instance of a line discipline into a tty structure. The
286 * ldisc must have a reference count above zero to ensure it remains.
287 * The tty instance refcount starts at zero.
290 * Caller must hold references
293 static void tty_ldisc_assign(struct tty_struct
*tty
, struct tty_ldisc
*ld
)
299 * tty_ldisc_try - internal helper
302 * Make a single attempt to grab and bump the refcount on
303 * the tty ldisc. Return 0 on failure or 1 on success. This is
304 * used to implement both the waiting and non waiting versions
307 * Locking: takes tty_ldisc_lock
310 static struct tty_ldisc
*tty_ldisc_try(struct tty_struct
*tty
)
313 struct tty_ldisc
*ld
;
315 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
317 if (test_bit(TTY_LDISC
, &tty
->flags
))
318 ld
= get_ldisc(tty
->ldisc
);
319 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
324 * tty_ldisc_ref_wait - wait for the tty ldisc
327 * Dereference the line discipline for the terminal and take a
328 * reference to it. If the line discipline is in flux then
329 * wait patiently until it changes.
331 * Note: Must not be called from an IRQ/timer context. The caller
332 * must also be careful not to hold other locks that will deadlock
333 * against a discipline change, such as an existing ldisc reference
334 * (which we check for)
336 * Locking: call functions take tty_ldisc_lock
339 struct tty_ldisc
*tty_ldisc_ref_wait(struct tty_struct
*tty
)
341 struct tty_ldisc
*ld
;
343 /* wait_event is a macro */
344 wait_event(tty_ldisc_wait
, (ld
= tty_ldisc_try(tty
)) != NULL
);
347 EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait
);
350 * tty_ldisc_ref - get the tty ldisc
353 * Dereference the line discipline for the terminal and take a
354 * reference to it. If the line discipline is in flux then
355 * return NULL. Can be called from IRQ and timer functions.
357 * Locking: called functions take tty_ldisc_lock
360 struct tty_ldisc
*tty_ldisc_ref(struct tty_struct
*tty
)
362 return tty_ldisc_try(tty
);
364 EXPORT_SYMBOL_GPL(tty_ldisc_ref
);
367 * tty_ldisc_deref - free a tty ldisc reference
368 * @ld: reference to free up
370 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
371 * be called in IRQ context.
373 * Locking: takes tty_ldisc_lock
376 void tty_ldisc_deref(struct tty_ldisc
*ld
)
380 EXPORT_SYMBOL_GPL(tty_ldisc_deref
);
382 static inline void tty_ldisc_put(struct tty_ldisc
*ld
)
388 * tty_ldisc_enable - allow ldisc use
389 * @tty: terminal to activate ldisc on
391 * Set the TTY_LDISC flag when the line discipline can be called
392 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
393 * changing flag to indicate any ldisc change is now over.
395 * Note: nobody should set the TTY_LDISC bit except via this function.
396 * Clearing directly is allowed.
399 void tty_ldisc_enable(struct tty_struct
*tty
)
401 set_bit(TTY_LDISC
, &tty
->flags
);
402 clear_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
403 wake_up(&tty_ldisc_wait
);
407 * tty_ldisc_flush - flush line discipline queue
410 * Flush the line discipline queue (if any) for this tty. If there
411 * is no line discipline active this is a no-op.
414 void tty_ldisc_flush(struct tty_struct
*tty
)
416 struct tty_ldisc
*ld
= tty_ldisc_ref(tty
);
418 if (ld
->ops
->flush_buffer
)
419 ld
->ops
->flush_buffer(tty
);
422 tty_buffer_flush(tty
);
424 EXPORT_SYMBOL_GPL(tty_ldisc_flush
);
427 * tty_set_termios_ldisc - set ldisc field
428 * @tty: tty structure
429 * @num: line discipline number
431 * This is probably overkill for real world processors but
432 * they are not on hot paths so a little discipline won't do
435 * Locking: takes termios_mutex
438 static void tty_set_termios_ldisc(struct tty_struct
*tty
, int num
)
440 mutex_lock(&tty
->termios_mutex
);
441 tty
->termios
->c_line
= num
;
442 mutex_unlock(&tty
->termios_mutex
);
446 * tty_ldisc_open - open a line discipline
447 * @tty: tty we are opening the ldisc on
448 * @ld: discipline to open
450 * A helper opening method. Also a convenient debugging and check
454 static int tty_ldisc_open(struct tty_struct
*tty
, struct tty_ldisc
*ld
)
456 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN
, &tty
->flags
));
458 return ld
->ops
->open(tty
);
463 * tty_ldisc_close - close a line discipline
464 * @tty: tty we are opening the ldisc on
465 * @ld: discipline to close
467 * A helper close method. Also a convenient debugging and check
471 static void tty_ldisc_close(struct tty_struct
*tty
, struct tty_ldisc
*ld
)
473 WARN_ON(!test_bit(TTY_LDISC_OPEN
, &tty
->flags
));
474 clear_bit(TTY_LDISC_OPEN
, &tty
->flags
);
480 * tty_ldisc_restore - helper for tty ldisc change
481 * @tty: tty to recover
482 * @old: previous ldisc
484 * Restore the previous line discipline or N_TTY when a line discipline
485 * change fails due to an open error
488 static void tty_ldisc_restore(struct tty_struct
*tty
, struct tty_ldisc
*old
)
491 struct tty_ldisc
*new_ldisc
;
494 /* There is an outstanding reference here so this is safe */
495 old
= tty_ldisc_get(old
->ops
->num
);
496 WARN_ON(IS_ERR(old
));
497 tty_ldisc_assign(tty
, old
);
498 tty_set_termios_ldisc(tty
, old
->ops
->num
);
499 if (tty_ldisc_open(tty
, old
) < 0) {
501 /* This driver is always present */
502 new_ldisc
= tty_ldisc_get(N_TTY
);
503 if (IS_ERR(new_ldisc
))
505 tty_ldisc_assign(tty
, new_ldisc
);
506 tty_set_termios_ldisc(tty
, N_TTY
);
507 r
= tty_ldisc_open(tty
, new_ldisc
);
509 panic("Couldn't open N_TTY ldisc for "
511 tty_name(tty
, buf
), r
);
516 * tty_ldisc_halt - shut down the line discipline
519 * Shut down the line discipline and work queue for this tty device.
520 * The TTY_LDISC flag being cleared ensures no further references can
521 * be obtained while the delayed work queue halt ensures that no more
522 * data is fed to the ldisc.
524 * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
525 * in order to make sure any currently executing ldisc work is also
529 static int tty_ldisc_halt(struct tty_struct
*tty
)
531 clear_bit(TTY_LDISC
, &tty
->flags
);
532 return cancel_delayed_work(&tty
->buf
.work
);
536 * tty_set_ldisc - set line discipline
537 * @tty: the terminal to set
538 * @ldisc: the line discipline
540 * Set the discipline of a tty line. Must be called from a process
541 * context. The ldisc change logic has to protect itself against any
542 * overlapping ldisc change (including on the other end of pty pairs),
543 * the close of one side of a tty/pty pair, and eventually hangup.
545 * Locking: takes tty_ldisc_lock, termios_mutex
548 int tty_set_ldisc(struct tty_struct
*tty
, int ldisc
)
551 struct tty_ldisc
*o_ldisc
, *new_ldisc
;
552 int work
, o_work
= 0;
553 struct tty_struct
*o_tty
;
555 new_ldisc
= tty_ldisc_get(ldisc
);
556 if (IS_ERR(new_ldisc
))
557 return PTR_ERR(new_ldisc
);
560 * We need to look at the tty locking here for pty/tty pairs
561 * when both sides try to change in parallel.
564 o_tty
= tty
->link
; /* o_tty is the pty side or NULL */
568 * Check the no-op case
571 if (tty
->ldisc
->ops
->num
== ldisc
) {
572 tty_ldisc_put(new_ldisc
);
577 * Problem: What do we do if this blocks ?
578 * We could deadlock here
581 tty_wait_until_sent(tty
, 0);
583 mutex_lock(&tty
->ldisc_mutex
);
586 * We could be midstream of another ldisc change which has
587 * dropped the lock during processing. If so we need to wait.
590 while (test_bit(TTY_LDISC_CHANGING
, &tty
->flags
)) {
591 mutex_unlock(&tty
->ldisc_mutex
);
592 wait_event(tty_ldisc_wait
,
593 test_bit(TTY_LDISC_CHANGING
, &tty
->flags
) == 0);
594 mutex_lock(&tty
->ldisc_mutex
);
596 set_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
599 * No more input please, we are switching. The new ldisc
600 * will update this value in the ldisc open function
603 tty
->receive_room
= 0;
605 o_ldisc
= tty
->ldisc
;
607 * Make sure we don't change while someone holds a
608 * reference to the line discipline. The TTY_LDISC bit
609 * prevents anyone taking a reference once it is clear.
610 * We need the lock to avoid racing reference takers.
612 * We must clear the TTY_LDISC bit here to avoid a livelock
613 * with a userspace app continually trying to use the tty in
614 * parallel to the change and re-referencing the tty.
617 work
= tty_ldisc_halt(tty
);
619 o_work
= tty_ldisc_halt(o_tty
);
622 * Wait for ->hangup_work and ->buf.work handlers to terminate.
623 * We must drop the mutex here in case a hangup is also in process.
626 mutex_unlock(&tty
->ldisc_mutex
);
628 flush_scheduled_work();
630 mutex_lock(&tty
->ldisc_mutex
);
631 if (test_bit(TTY_HUPPED
, &tty
->flags
)) {
632 /* We were raced by the hangup method. It will have stomped
633 the ldisc data and closed the ldisc down */
634 clear_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
635 mutex_unlock(&tty
->ldisc_mutex
);
636 tty_ldisc_put(new_ldisc
);
640 /* Shutdown the current discipline. */
641 tty_ldisc_close(tty
, o_ldisc
);
643 /* Now set up the new line discipline. */
644 tty_ldisc_assign(tty
, new_ldisc
);
645 tty_set_termios_ldisc(tty
, ldisc
);
647 retval
= tty_ldisc_open(tty
, new_ldisc
);
649 /* Back to the old one or N_TTY if we can't */
650 tty_ldisc_put(new_ldisc
);
651 tty_ldisc_restore(tty
, o_ldisc
);
654 /* At this point we hold a reference to the new ldisc and a
655 a reference to the old ldisc. If we ended up flipping back
656 to the existing ldisc we have two references to it */
658 if (tty
->ldisc
->ops
->num
!= o_ldisc
->ops
->num
&& tty
->ops
->set_ldisc
)
659 tty
->ops
->set_ldisc(tty
);
661 tty_ldisc_put(o_ldisc
);
664 * Allow ldisc referencing to occur again
667 tty_ldisc_enable(tty
);
669 tty_ldisc_enable(o_tty
);
671 /* Restart the work queue in case no characters kick it off. Safe if
674 schedule_delayed_work(&tty
->buf
.work
, 1);
676 schedule_delayed_work(&o_tty
->buf
.work
, 1);
677 mutex_unlock(&tty
->ldisc_mutex
);
682 * tty_reset_termios - reset terminal state
685 * Restore a terminal to the driver default state.
688 static void tty_reset_termios(struct tty_struct
*tty
)
690 mutex_lock(&tty
->termios_mutex
);
691 *tty
->termios
= tty
->driver
->init_termios
;
692 tty
->termios
->c_ispeed
= tty_termios_input_baud_rate(tty
->termios
);
693 tty
->termios
->c_ospeed
= tty_termios_baud_rate(tty
->termios
);
694 mutex_unlock(&tty
->termios_mutex
);
699 * tty_ldisc_reinit - reinitialise the tty ldisc
700 * @tty: tty to reinit
702 * Switch the tty back to N_TTY line discipline and leave the
706 static void tty_ldisc_reinit(struct tty_struct
*tty
)
708 struct tty_ldisc
*ld
;
710 tty_ldisc_close(tty
, tty
->ldisc
);
711 tty_ldisc_put(tty
->ldisc
);
714 * Switch the line discipline back
716 ld
= tty_ldisc_get(N_TTY
);
718 tty_ldisc_assign(tty
, ld
);
719 tty_set_termios_ldisc(tty
, N_TTY
);
723 * tty_ldisc_hangup - hangup ldisc reset
724 * @tty: tty being hung up
726 * Some tty devices reset their termios when they receive a hangup
727 * event. In that situation we must also switch back to N_TTY properly
728 * before we reset the termios data.
730 * Locking: We can take the ldisc mutex as the rest of the code is
731 * careful to allow for this.
733 * In the pty pair case this occurs in the close() path of the
734 * tty itself so we must be careful about locking rules.
737 void tty_ldisc_hangup(struct tty_struct
*tty
)
739 struct tty_ldisc
*ld
;
742 * FIXME! What are the locking issues here? This may me overdoing
743 * things... This question is especially important now that we've
744 * removed the irqlock.
746 ld
= tty_ldisc_ref(tty
);
748 /* We may have no line discipline at this point */
749 if (ld
->ops
->flush_buffer
)
750 ld
->ops
->flush_buffer(tty
);
751 tty_driver_flush_buffer(tty
);
752 if ((test_bit(TTY_DO_WRITE_WAKEUP
, &tty
->flags
)) &&
753 ld
->ops
->write_wakeup
)
754 ld
->ops
->write_wakeup(tty
);
756 ld
->ops
->hangup(tty
);
760 * FIXME: Once we trust the LDISC code better we can wait here for
761 * ldisc completion and fix the driver call race
763 wake_up_interruptible_poll(&tty
->write_wait
, POLLOUT
);
764 wake_up_interruptible_poll(&tty
->read_wait
, POLLIN
);
766 * Shutdown the current line discipline, and reset it to
769 if (tty
->driver
->flags
& TTY_DRIVER_RESET_TERMIOS
) {
770 /* Make sure the old ldisc is quiescent */
772 flush_scheduled_work();
774 /* Avoid racing set_ldisc or tty_ldisc_release */
775 mutex_lock(&tty
->ldisc_mutex
);
776 if (tty
->ldisc
) { /* Not yet closed */
777 /* Switch back to N_TTY */
778 tty_ldisc_reinit(tty
);
779 /* At this point we have a closed ldisc and we want to
780 reopen it. We could defer this to the next open but
781 it means auditing a lot of other paths so this is
783 WARN_ON(tty_ldisc_open(tty
, tty
->ldisc
));
784 tty_ldisc_enable(tty
);
786 mutex_unlock(&tty
->ldisc_mutex
);
787 tty_reset_termios(tty
);
792 * tty_ldisc_setup - open line discipline
793 * @tty: tty being shut down
794 * @o_tty: pair tty for pty/tty pairs
796 * Called during the initial open of a tty/pty pair in order to set up the
797 * line disciplines and bind them to the tty. This has no locking issues
798 * as the device isn't yet active.
801 int tty_ldisc_setup(struct tty_struct
*tty
, struct tty_struct
*o_tty
)
803 struct tty_ldisc
*ld
= tty
->ldisc
;
806 retval
= tty_ldisc_open(tty
, ld
);
811 retval
= tty_ldisc_open(o_tty
, o_tty
->ldisc
);
813 tty_ldisc_close(tty
, ld
);
816 tty_ldisc_enable(o_tty
);
818 tty_ldisc_enable(tty
);
822 * tty_ldisc_release - release line discipline
823 * @tty: tty being shut down
824 * @o_tty: pair tty for pty/tty pairs
826 * Called during the final close of a tty/pty pair in order to shut down
827 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
828 * ldisc has not been opened.
831 void tty_ldisc_release(struct tty_struct
*tty
, struct tty_struct
*o_tty
)
834 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
835 * kill any delayed work. As this is the final close it does not
836 * race with the set_ldisc code path.
840 flush_scheduled_work();
842 mutex_lock(&tty
->ldisc_mutex
);
844 * Now kill off the ldisc
846 tty_ldisc_close(tty
, tty
->ldisc
);
847 tty_ldisc_put(tty
->ldisc
);
848 /* Force an oops if we mess this up */
851 /* Ensure the next open requests the N_TTY ldisc */
852 tty_set_termios_ldisc(tty
, N_TTY
);
853 mutex_unlock(&tty
->ldisc_mutex
);
855 /* This will need doing differently if we need to lock */
857 tty_ldisc_release(o_tty
, NULL
);
859 /* And the memory resources remaining (buffers, termios) will be
860 disposed of when the kref hits zero */
864 * tty_ldisc_init - ldisc setup for new tty
865 * @tty: tty being allocated
867 * Set up the line discipline objects for a newly allocated tty. Note that
868 * the tty structure is not completely set up when this call is made.
871 void tty_ldisc_init(struct tty_struct
*tty
)
873 struct tty_ldisc
*ld
= tty_ldisc_get(N_TTY
);
875 panic("n_tty: init_tty");
876 tty_ldisc_assign(tty
, ld
);
879 void tty_ldisc_begin(void)
881 /* Setup the default TTY line discipline. */
882 (void) tty_register_ldisc(N_TTY
, &tty_ldisc_N_TTY
);