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/smp_lock.h> /* For the moment */
39 #include <linux/kmod.h>
40 #include <linux/nsproxy.h>
43 * This guards the refcounted line discipline lists. The lock
44 * must be taken with irqs off because there are hangup path
45 * callers who will do ldisc lookups and cannot sleep.
48 static DEFINE_SPINLOCK(tty_ldisc_lock
);
49 static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait
);
50 /* Line disc dispatch table */
51 static struct tty_ldisc_ops
*tty_ldiscs
[NR_LDISCS
];
53 static inline struct tty_ldisc
*get_ldisc(struct tty_ldisc
*ld
)
56 atomic_inc(&ld
->users
);
60 static void put_ldisc(struct tty_ldisc
*ld
)
64 if (WARN_ON_ONCE(!ld
))
68 * If this is the last user, free the ldisc, and
69 * release the ldisc ops.
71 * We really want an "atomic_dec_and_lock_irqsave()",
72 * but we don't have it, so this does it by hand.
74 local_irq_save(flags
);
75 if (atomic_dec_and_lock(&ld
->users
, &tty_ldisc_lock
)) {
76 struct tty_ldisc_ops
*ldo
= ld
->ops
;
79 module_put(ldo
->owner
);
80 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
85 local_irq_restore(flags
);
89 * tty_register_ldisc - install a line discipline
91 * @new_ldisc: pointer to the ldisc object
93 * Installs a new line discipline into the kernel. The discipline
94 * is set up as unreferenced and then made available to the kernel
95 * from this point onwards.
98 * takes tty_ldisc_lock to guard against ldisc races
101 int tty_register_ldisc(int disc
, struct tty_ldisc_ops
*new_ldisc
)
106 if (disc
< N_TTY
|| disc
>= NR_LDISCS
)
109 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
110 tty_ldiscs
[disc
] = new_ldisc
;
111 new_ldisc
->num
= disc
;
112 new_ldisc
->refcount
= 0;
113 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
117 EXPORT_SYMBOL(tty_register_ldisc
);
120 * tty_unregister_ldisc - unload a line discipline
121 * @disc: ldisc number
122 * @new_ldisc: pointer to the ldisc object
124 * Remove a line discipline from the kernel providing it is not
128 * takes tty_ldisc_lock to guard against ldisc races
131 int tty_unregister_ldisc(int disc
)
136 if (disc
< N_TTY
|| disc
>= NR_LDISCS
)
139 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
140 if (tty_ldiscs
[disc
]->refcount
)
143 tty_ldiscs
[disc
] = NULL
;
144 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
148 EXPORT_SYMBOL(tty_unregister_ldisc
);
150 static struct tty_ldisc_ops
*get_ldops(int disc
)
153 struct tty_ldisc_ops
*ldops
, *ret
;
155 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
156 ret
= ERR_PTR(-EINVAL
);
157 ldops
= tty_ldiscs
[disc
];
159 ret
= ERR_PTR(-EAGAIN
);
160 if (try_module_get(ldops
->owner
)) {
165 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
169 static void put_ldops(struct tty_ldisc_ops
*ldops
)
173 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
175 module_put(ldops
->owner
);
176 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
180 * tty_ldisc_get - take a reference to an ldisc
181 * @disc: ldisc number
183 * Takes a reference to a line discipline. Deals with refcounts and
184 * module locking counts. Returns NULL if the discipline is not available.
185 * Returns a pointer to the discipline and bumps the ref count if it is
189 * takes tty_ldisc_lock to guard against ldisc races
192 static struct tty_ldisc
*tty_ldisc_get(int disc
)
194 struct tty_ldisc
*ld
;
195 struct tty_ldisc_ops
*ldops
;
197 if (disc
< N_TTY
|| disc
>= NR_LDISCS
)
198 return ERR_PTR(-EINVAL
);
201 * Get the ldisc ops - we may need to request them to be loaded
202 * dynamically and try again.
204 ldops
= get_ldops(disc
);
206 request_module("tty-ldisc-%d", disc
);
207 ldops
= get_ldops(disc
);
209 return ERR_CAST(ldops
);
212 ld
= kmalloc(sizeof(struct tty_ldisc
), GFP_KERNEL
);
215 return ERR_PTR(-ENOMEM
);
219 atomic_set(&ld
->users
, 1);
223 static void *tty_ldiscs_seq_start(struct seq_file
*m
, loff_t
*pos
)
225 return (*pos
< NR_LDISCS
) ? pos
: NULL
;
228 static void *tty_ldiscs_seq_next(struct seq_file
*m
, void *v
, loff_t
*pos
)
231 return (*pos
< NR_LDISCS
) ? pos
: NULL
;
234 static void tty_ldiscs_seq_stop(struct seq_file
*m
, void *v
)
238 static int tty_ldiscs_seq_show(struct seq_file
*m
, void *v
)
240 int i
= *(loff_t
*)v
;
241 struct tty_ldisc_ops
*ldops
;
243 ldops
= get_ldops(i
);
246 seq_printf(m
, "%-10s %2d\n", ldops
->name
? ldops
->name
: "???", i
);
251 static const struct seq_operations tty_ldiscs_seq_ops
= {
252 .start
= tty_ldiscs_seq_start
,
253 .next
= tty_ldiscs_seq_next
,
254 .stop
= tty_ldiscs_seq_stop
,
255 .show
= tty_ldiscs_seq_show
,
258 static int proc_tty_ldiscs_open(struct inode
*inode
, struct file
*file
)
260 return seq_open(file
, &tty_ldiscs_seq_ops
);
263 const struct file_operations tty_ldiscs_proc_fops
= {
264 .owner
= THIS_MODULE
,
265 .open
= proc_tty_ldiscs_open
,
268 .release
= seq_release
,
272 * tty_ldisc_assign - set ldisc on a tty
273 * @tty: tty to assign
274 * @ld: line discipline
276 * Install an instance of a line discipline into a tty structure. The
277 * ldisc must have a reference count above zero to ensure it remains.
278 * The tty instance refcount starts at zero.
281 * Caller must hold references
284 static void tty_ldisc_assign(struct tty_struct
*tty
, struct tty_ldisc
*ld
)
290 * tty_ldisc_try - internal helper
293 * Make a single attempt to grab and bump the refcount on
294 * the tty ldisc. Return 0 on failure or 1 on success. This is
295 * used to implement both the waiting and non waiting versions
298 * Locking: takes tty_ldisc_lock
301 static struct tty_ldisc
*tty_ldisc_try(struct tty_struct
*tty
)
304 struct tty_ldisc
*ld
;
306 spin_lock_irqsave(&tty_ldisc_lock
, flags
);
308 if (test_bit(TTY_LDISC
, &tty
->flags
))
309 ld
= get_ldisc(tty
->ldisc
);
310 spin_unlock_irqrestore(&tty_ldisc_lock
, flags
);
315 * tty_ldisc_ref_wait - wait for the tty ldisc
318 * Dereference the line discipline for the terminal and take a
319 * reference to it. If the line discipline is in flux then
320 * wait patiently until it changes.
322 * Note: Must not be called from an IRQ/timer context. The caller
323 * must also be careful not to hold other locks that will deadlock
324 * against a discipline change, such as an existing ldisc reference
325 * (which we check for)
327 * Locking: call functions take tty_ldisc_lock
330 struct tty_ldisc
*tty_ldisc_ref_wait(struct tty_struct
*tty
)
332 struct tty_ldisc
*ld
;
334 /* wait_event is a macro */
335 wait_event(tty_ldisc_wait
, (ld
= tty_ldisc_try(tty
)) != NULL
);
338 EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait
);
341 * tty_ldisc_ref - get the tty ldisc
344 * Dereference the line discipline for the terminal and take a
345 * reference to it. If the line discipline is in flux then
346 * return NULL. Can be called from IRQ and timer functions.
348 * Locking: called functions take tty_ldisc_lock
351 struct tty_ldisc
*tty_ldisc_ref(struct tty_struct
*tty
)
353 return tty_ldisc_try(tty
);
355 EXPORT_SYMBOL_GPL(tty_ldisc_ref
);
358 * tty_ldisc_deref - free a tty ldisc reference
359 * @ld: reference to free up
361 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
362 * be called in IRQ context.
364 * Locking: takes tty_ldisc_lock
367 void tty_ldisc_deref(struct tty_ldisc
*ld
)
371 EXPORT_SYMBOL_GPL(tty_ldisc_deref
);
373 static inline void tty_ldisc_put(struct tty_ldisc
*ld
)
379 * tty_ldisc_enable - allow ldisc use
380 * @tty: terminal to activate ldisc on
382 * Set the TTY_LDISC flag when the line discipline can be called
383 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
384 * changing flag to indicate any ldisc change is now over.
386 * Note: nobody should set the TTY_LDISC bit except via this function.
387 * Clearing directly is allowed.
390 void tty_ldisc_enable(struct tty_struct
*tty
)
392 set_bit(TTY_LDISC
, &tty
->flags
);
393 clear_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
394 wake_up(&tty_ldisc_wait
);
398 * tty_ldisc_flush - flush line discipline queue
401 * Flush the line discipline queue (if any) for this tty. If there
402 * is no line discipline active this is a no-op.
405 void tty_ldisc_flush(struct tty_struct
*tty
)
407 struct tty_ldisc
*ld
= tty_ldisc_ref(tty
);
409 if (ld
->ops
->flush_buffer
)
410 ld
->ops
->flush_buffer(tty
);
413 tty_buffer_flush(tty
);
415 EXPORT_SYMBOL_GPL(tty_ldisc_flush
);
418 * tty_set_termios_ldisc - set ldisc field
419 * @tty: tty structure
420 * @num: line discipline number
422 * This is probably overkill for real world processors but
423 * they are not on hot paths so a little discipline won't do
426 * Locking: takes termios_mutex
429 static void tty_set_termios_ldisc(struct tty_struct
*tty
, int num
)
431 mutex_lock(&tty
->termios_mutex
);
432 tty
->termios
->c_line
= num
;
433 mutex_unlock(&tty
->termios_mutex
);
437 * tty_ldisc_open - open a line discipline
438 * @tty: tty we are opening the ldisc on
439 * @ld: discipline to open
441 * A helper opening method. Also a convenient debugging and check
444 * Locking: always called with BTM already held.
447 static int tty_ldisc_open(struct tty_struct
*tty
, struct tty_ldisc
*ld
)
449 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN
, &tty
->flags
));
452 /* BTM here locks versus a hangup event */
453 WARN_ON(!tty_locked());
454 ret
= ld
->ops
->open(tty
);
461 * tty_ldisc_close - close a line discipline
462 * @tty: tty we are opening the ldisc on
463 * @ld: discipline to close
465 * A helper close method. Also a convenient debugging and check
469 static void tty_ldisc_close(struct tty_struct
*tty
, struct tty_ldisc
*ld
)
471 WARN_ON(!test_bit(TTY_LDISC_OPEN
, &tty
->flags
));
472 clear_bit(TTY_LDISC_OPEN
, &tty
->flags
);
478 * tty_ldisc_restore - helper for tty ldisc change
479 * @tty: tty to recover
480 * @old: previous ldisc
482 * Restore the previous line discipline or N_TTY when a line discipline
483 * change fails due to an open error
486 static void tty_ldisc_restore(struct tty_struct
*tty
, struct tty_ldisc
*old
)
489 struct tty_ldisc
*new_ldisc
;
492 /* There is an outstanding reference here so this is safe */
493 old
= tty_ldisc_get(old
->ops
->num
);
494 WARN_ON(IS_ERR(old
));
495 tty_ldisc_assign(tty
, old
);
496 tty_set_termios_ldisc(tty
, old
->ops
->num
);
497 if (tty_ldisc_open(tty
, old
) < 0) {
499 /* This driver is always present */
500 new_ldisc
= tty_ldisc_get(N_TTY
);
501 if (IS_ERR(new_ldisc
))
503 tty_ldisc_assign(tty
, new_ldisc
);
504 tty_set_termios_ldisc(tty
, N_TTY
);
505 r
= tty_ldisc_open(tty
, new_ldisc
);
507 panic("Couldn't open N_TTY ldisc for "
509 tty_name(tty
, buf
), r
);
514 * tty_ldisc_halt - shut down the line discipline
517 * Shut down the line discipline and work queue for this tty device.
518 * The TTY_LDISC flag being cleared ensures no further references can
519 * be obtained while the delayed work queue halt ensures that no more
520 * data is fed to the ldisc.
522 * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
523 * in order to make sure any currently executing ldisc work is also
527 static int tty_ldisc_halt(struct tty_struct
*tty
)
529 clear_bit(TTY_LDISC
, &tty
->flags
);
530 return cancel_delayed_work_sync(&tty
->buf
.work
);
534 * tty_set_ldisc - set line discipline
535 * @tty: the terminal to set
536 * @ldisc: the line discipline
538 * Set the discipline of a tty line. Must be called from a process
539 * context. The ldisc change logic has to protect itself against any
540 * overlapping ldisc change (including on the other end of pty pairs),
541 * the close of one side of a tty/pty pair, and eventually hangup.
543 * Locking: takes tty_ldisc_lock, termios_mutex
546 int tty_set_ldisc(struct tty_struct
*tty
, int ldisc
)
549 struct tty_ldisc
*o_ldisc
, *new_ldisc
;
550 int work
, o_work
= 0;
551 struct tty_struct
*o_tty
;
553 new_ldisc
= tty_ldisc_get(ldisc
);
554 if (IS_ERR(new_ldisc
))
555 return PTR_ERR(new_ldisc
);
559 * We need to look at the tty locking here for pty/tty pairs
560 * when both sides try to change in parallel.
563 o_tty
= tty
->link
; /* o_tty is the pty side or NULL */
567 * Check the no-op case
570 if (tty
->ldisc
->ops
->num
== ldisc
) {
572 tty_ldisc_put(new_ldisc
);
578 * Problem: What do we do if this blocks ?
579 * We could deadlock here
582 tty_wait_until_sent(tty
, 0);
585 mutex_lock(&tty
->ldisc_mutex
);
588 * We could be midstream of another ldisc change which has
589 * dropped the lock during processing. If so we need to wait.
592 while (test_bit(TTY_LDISC_CHANGING
, &tty
->flags
)) {
593 mutex_unlock(&tty
->ldisc_mutex
);
595 wait_event(tty_ldisc_wait
,
596 test_bit(TTY_LDISC_CHANGING
, &tty
->flags
) == 0);
598 mutex_lock(&tty
->ldisc_mutex
);
601 set_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
604 * No more input please, we are switching. The new ldisc
605 * will update this value in the ldisc open function
608 tty
->receive_room
= 0;
610 o_ldisc
= tty
->ldisc
;
614 * Make sure we don't change while someone holds a
615 * reference to the line discipline. The TTY_LDISC bit
616 * prevents anyone taking a reference once it is clear.
617 * We need the lock to avoid racing reference takers.
619 * We must clear the TTY_LDISC bit here to avoid a livelock
620 * with a userspace app continually trying to use the tty in
621 * parallel to the change and re-referencing the tty.
624 work
= tty_ldisc_halt(tty
);
626 o_work
= tty_ldisc_halt(o_tty
);
629 * Wait for ->hangup_work and ->buf.work handlers to terminate.
630 * We must drop the mutex here in case a hangup is also in process.
633 mutex_unlock(&tty
->ldisc_mutex
);
635 flush_scheduled_work();
638 mutex_lock(&tty
->ldisc_mutex
);
639 if (test_bit(TTY_HUPPED
, &tty
->flags
)) {
640 /* We were raced by the hangup method. It will have stomped
641 the ldisc data and closed the ldisc down */
642 clear_bit(TTY_LDISC_CHANGING
, &tty
->flags
);
643 mutex_unlock(&tty
->ldisc_mutex
);
644 tty_ldisc_put(new_ldisc
);
649 /* Shutdown the current discipline. */
650 tty_ldisc_close(tty
, o_ldisc
);
652 /* Now set up the new line discipline. */
653 tty_ldisc_assign(tty
, new_ldisc
);
654 tty_set_termios_ldisc(tty
, ldisc
);
656 retval
= tty_ldisc_open(tty
, new_ldisc
);
658 /* Back to the old one or N_TTY if we can't */
659 tty_ldisc_put(new_ldisc
);
660 tty_ldisc_restore(tty
, o_ldisc
);
663 /* At this point we hold a reference to the new ldisc and a
664 a reference to the old ldisc. If we ended up flipping back
665 to the existing ldisc we have two references to it */
667 if (tty
->ldisc
->ops
->num
!= o_ldisc
->ops
->num
&& tty
->ops
->set_ldisc
)
668 tty
->ops
->set_ldisc(tty
);
670 tty_ldisc_put(o_ldisc
);
673 * Allow ldisc referencing to occur again
676 tty_ldisc_enable(tty
);
678 tty_ldisc_enable(o_tty
);
680 /* Restart the work queue in case no characters kick it off. Safe if
683 schedule_delayed_work(&tty
->buf
.work
, 1);
685 schedule_delayed_work(&o_tty
->buf
.work
, 1);
686 mutex_unlock(&tty
->ldisc_mutex
);
692 * tty_reset_termios - reset terminal state
695 * Restore a terminal to the driver default state.
698 static void tty_reset_termios(struct tty_struct
*tty
)
700 mutex_lock(&tty
->termios_mutex
);
701 *tty
->termios
= tty
->driver
->init_termios
;
702 tty
->termios
->c_ispeed
= tty_termios_input_baud_rate(tty
->termios
);
703 tty
->termios
->c_ospeed
= tty_termios_baud_rate(tty
->termios
);
704 mutex_unlock(&tty
->termios_mutex
);
709 * tty_ldisc_reinit - reinitialise the tty ldisc
710 * @tty: tty to reinit
711 * @ldisc: line discipline to reinitialize
713 * Switch the tty to a line discipline and leave the ldisc
717 static void tty_ldisc_reinit(struct tty_struct
*tty
, int ldisc
)
719 struct tty_ldisc
*ld
;
721 tty_ldisc_close(tty
, tty
->ldisc
);
722 tty_ldisc_put(tty
->ldisc
);
725 * Switch the line discipline back
727 ld
= tty_ldisc_get(ldisc
);
729 tty_ldisc_assign(tty
, ld
);
730 tty_set_termios_ldisc(tty
, ldisc
);
734 * tty_ldisc_hangup - hangup ldisc reset
735 * @tty: tty being hung up
737 * Some tty devices reset their termios when they receive a hangup
738 * event. In that situation we must also switch back to N_TTY properly
739 * before we reset the termios data.
741 * Locking: We can take the ldisc mutex as the rest of the code is
742 * careful to allow for this.
744 * In the pty pair case this occurs in the close() path of the
745 * tty itself so we must be careful about locking rules.
748 void tty_ldisc_hangup(struct tty_struct
*tty
)
750 struct tty_ldisc
*ld
;
751 int reset
= tty
->driver
->flags
& TTY_DRIVER_RESET_TERMIOS
;
755 * FIXME! What are the locking issues here? This may me overdoing
756 * things... This question is especially important now that we've
757 * removed the irqlock.
759 ld
= tty_ldisc_ref(tty
);
761 /* We may have no line discipline at this point */
762 if (ld
->ops
->flush_buffer
)
763 ld
->ops
->flush_buffer(tty
);
764 tty_driver_flush_buffer(tty
);
765 if ((test_bit(TTY_DO_WRITE_WAKEUP
, &tty
->flags
)) &&
766 ld
->ops
->write_wakeup
)
767 ld
->ops
->write_wakeup(tty
);
769 ld
->ops
->hangup(tty
);
773 * FIXME: Once we trust the LDISC code better we can wait here for
774 * ldisc completion and fix the driver call race
776 wake_up_interruptible_poll(&tty
->write_wait
, POLLOUT
);
777 wake_up_interruptible_poll(&tty
->read_wait
, POLLIN
);
779 * Shutdown the current line discipline, and reset it to
782 * Avoid racing set_ldisc or tty_ldisc_release
784 mutex_lock(&tty
->ldisc_mutex
);
787 * this is like tty_ldisc_halt, but we need to give up
788 * the BTM before calling cancel_delayed_work_sync,
789 * which may need to wait for another function taking the BTM
791 clear_bit(TTY_LDISC
, &tty
->flags
);
793 cancel_delayed_work_sync(&tty
->buf
.work
);
794 mutex_unlock(&tty
->ldisc_mutex
);
797 mutex_lock(&tty
->ldisc_mutex
);
799 /* At this point we have a closed ldisc and we want to
800 reopen it. We could defer this to the next open but
801 it means auditing a lot of other paths so this is
803 if (tty
->ldisc
) { /* Not yet closed */
805 tty_ldisc_reinit(tty
, tty
->termios
->c_line
);
806 err
= tty_ldisc_open(tty
, tty
->ldisc
);
808 /* If the re-open fails or we reset then go to N_TTY. The
809 N_TTY open cannot fail */
811 tty_ldisc_reinit(tty
, N_TTY
);
812 WARN_ON(tty_ldisc_open(tty
, tty
->ldisc
));
814 tty_ldisc_enable(tty
);
816 mutex_unlock(&tty
->ldisc_mutex
);
818 tty_reset_termios(tty
);
822 * tty_ldisc_setup - open line discipline
823 * @tty: tty being shut down
824 * @o_tty: pair tty for pty/tty pairs
826 * Called during the initial open of a tty/pty pair in order to set up the
827 * line disciplines and bind them to the tty. This has no locking issues
828 * as the device isn't yet active.
831 int tty_ldisc_setup(struct tty_struct
*tty
, struct tty_struct
*o_tty
)
833 struct tty_ldisc
*ld
= tty
->ldisc
;
836 retval
= tty_ldisc_open(tty
, ld
);
841 retval
= tty_ldisc_open(o_tty
, o_tty
->ldisc
);
843 tty_ldisc_close(tty
, ld
);
846 tty_ldisc_enable(o_tty
);
848 tty_ldisc_enable(tty
);
852 * tty_ldisc_release - release line discipline
853 * @tty: tty being shut down
854 * @o_tty: pair tty for pty/tty pairs
856 * Called during the final close of a tty/pty pair in order to shut down
857 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
858 * ldisc has not been opened.
861 void tty_ldisc_release(struct tty_struct
*tty
, struct tty_struct
*o_tty
)
864 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
865 * kill any delayed work. As this is the final close it does not
866 * race with the set_ldisc code path.
871 flush_scheduled_work();
874 mutex_lock(&tty
->ldisc_mutex
);
876 * Now kill off the ldisc
878 tty_ldisc_close(tty
, tty
->ldisc
);
879 tty_ldisc_put(tty
->ldisc
);
880 /* Force an oops if we mess this up */
883 /* Ensure the next open requests the N_TTY ldisc */
884 tty_set_termios_ldisc(tty
, N_TTY
);
885 mutex_unlock(&tty
->ldisc_mutex
);
887 /* This will need doing differently if we need to lock */
889 tty_ldisc_release(o_tty
, NULL
);
891 /* And the memory resources remaining (buffers, termios) will be
892 disposed of when the kref hits zero */
896 * tty_ldisc_init - ldisc setup for new tty
897 * @tty: tty being allocated
899 * Set up the line discipline objects for a newly allocated tty. Note that
900 * the tty structure is not completely set up when this call is made.
903 void tty_ldisc_init(struct tty_struct
*tty
)
905 struct tty_ldisc
*ld
= tty_ldisc_get(N_TTY
);
907 panic("n_tty: init_tty");
908 tty_ldisc_assign(tty
, ld
);
911 void tty_ldisc_begin(void)
913 /* Setup the default TTY line discipline. */
914 (void) tty_register_ldisc(N_TTY
, &tty_ldisc_N_TTY
);