blob: ef925d5817139417764e7b3d6dfc2108d86971c5 [file] [log] [blame]
Alan Cox01e1abb2008-07-22 11:16:55 +01001#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>
8#include <linux/tty.h>
9#include <linux/tty_driver.h>
10#include <linux/tty_flip.h>
11#include <linux/devpts_fs.h>
12#include <linux/file.h>
Alan Cox01e1abb2008-07-22 11:16:55 +010013#include <linux/console.h>
14#include <linux/timer.h>
15#include <linux/ctype.h>
16#include <linux/kd.h>
17#include <linux/mm.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>
Alan Cox01e1abb2008-07-22 11:16:55 +010024#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>
29
30#include <linux/uaccess.h>
31#include <asm/system.h>
32
33#include <linux/kbd_kern.h>
34#include <linux/vt_kern.h>
35#include <linux/selection.h>
36
37#include <linux/kmod.h>
38#include <linux/nsproxy.h>
39
40/*
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.
44 */
45
46static DEFINE_SPINLOCK(tty_ldisc_lock);
47static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
Jiri Slaby100eeae2010-10-31 23:17:51 +010048static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_idle);
Alan Cox01e1abb2008-07-22 11:16:55 +010049/* Line disc dispatch table */
50static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
51
Linus Torvalds65b77042009-08-03 11:11:19 -070052static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
53{
54 if (ld)
55 atomic_inc(&ld->users);
56 return ld;
57}
58
Linus Torvaldscbe93522009-08-03 14:54:56 -070059static void put_ldisc(struct tty_ldisc *ld)
Linus Torvalds65b77042009-08-03 11:11:19 -070060{
Linus Torvaldscbe93522009-08-03 14:54:56 -070061 unsigned long flags;
62
Linus Torvalds65b77042009-08-03 11:11:19 -070063 if (WARN_ON_ONCE(!ld))
64 return;
65
66 /*
67 * If this is the last user, free the ldisc, and
68 * release the ldisc ops.
Linus Torvaldscbe93522009-08-03 14:54:56 -070069 *
70 * We really want an "atomic_dec_and_lock_irqsave()",
71 * but we don't have it, so this does it by hand.
Linus Torvalds65b77042009-08-03 11:11:19 -070072 */
Linus Torvaldscbe93522009-08-03 14:54:56 -070073 local_irq_save(flags);
74 if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) {
Linus Torvalds65b77042009-08-03 11:11:19 -070075 struct tty_ldisc_ops *ldo = ld->ops;
76
Linus Torvalds65b77042009-08-03 11:11:19 -070077 ldo->refcount--;
78 module_put(ldo->owner);
79 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvaldscbe93522009-08-03 14:54:56 -070080
81 kfree(ld);
82 return;
Linus Torvalds65b77042009-08-03 11:11:19 -070083 }
Linus Torvaldscbe93522009-08-03 14:54:56 -070084 local_irq_restore(flags);
Jiri Slaby100eeae2010-10-31 23:17:51 +010085 wake_up(&tty_ldisc_idle);
Linus Torvalds65b77042009-08-03 11:11:19 -070086}
87
Alan Cox01e1abb2008-07-22 11:16:55 +010088/**
89 * tty_register_ldisc - install a line discipline
90 * @disc: ldisc number
91 * @new_ldisc: pointer to the ldisc object
92 *
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.
96 *
97 * Locking:
98 * takes tty_ldisc_lock to guard against ldisc races
99 */
100
101int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
102{
103 unsigned long flags;
104 int ret = 0;
105
106 if (disc < N_TTY || disc >= NR_LDISCS)
107 return -EINVAL;
108
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);
114
115 return ret;
116}
117EXPORT_SYMBOL(tty_register_ldisc);
118
119/**
120 * tty_unregister_ldisc - unload a line discipline
121 * @disc: ldisc number
122 * @new_ldisc: pointer to the ldisc object
123 *
124 * Remove a line discipline from the kernel providing it is not
125 * currently in use.
126 *
127 * Locking:
128 * takes tty_ldisc_lock to guard against ldisc races
129 */
130
131int tty_unregister_ldisc(int disc)
132{
133 unsigned long flags;
134 int ret = 0;
135
136 if (disc < N_TTY || disc >= NR_LDISCS)
137 return -EINVAL;
138
139 spin_lock_irqsave(&tty_ldisc_lock, flags);
140 if (tty_ldiscs[disc]->refcount)
141 ret = -EBUSY;
142 else
143 tty_ldiscs[disc] = NULL;
144 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
145
146 return ret;
147}
148EXPORT_SYMBOL(tty_unregister_ldisc);
149
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700150static struct tty_ldisc_ops *get_ldops(int disc)
151{
152 unsigned long flags;
153 struct tty_ldisc_ops *ldops, *ret;
154
155 spin_lock_irqsave(&tty_ldisc_lock, flags);
156 ret = ERR_PTR(-EINVAL);
157 ldops = tty_ldiscs[disc];
158 if (ldops) {
159 ret = ERR_PTR(-EAGAIN);
160 if (try_module_get(ldops->owner)) {
161 ldops->refcount++;
162 ret = ldops;
163 }
164 }
165 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
166 return ret;
167}
168
169static void put_ldops(struct tty_ldisc_ops *ldops)
170{
171 unsigned long flags;
172
173 spin_lock_irqsave(&tty_ldisc_lock, flags);
174 ldops->refcount--;
175 module_put(ldops->owner);
176 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
177}
Alan Cox01e1abb2008-07-22 11:16:55 +0100178
179/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100180 * tty_ldisc_get - take a reference to an ldisc
181 * @disc: ldisc number
Alan Cox01e1abb2008-07-22 11:16:55 +0100182 *
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
186 * available
187 *
188 * Locking:
189 * takes tty_ldisc_lock to guard against ldisc races
190 */
191
Alan Coxc65c9bc2009-06-11 12:50:12 +0100192static struct tty_ldisc *tty_ldisc_get(int disc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100193{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100194 struct tty_ldisc *ld;
Linus Torvalds182274f2009-08-03 16:01:28 -0700195 struct tty_ldisc_ops *ldops;
Alan Cox01e1abb2008-07-22 11:16:55 +0100196
197 if (disc < N_TTY || disc >= NR_LDISCS)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100198 return ERR_PTR(-EINVAL);
Linus Torvalds182274f2009-08-03 16:01:28 -0700199
200 /*
201 * Get the ldisc ops - we may need to request them to be loaded
202 * dynamically and try again.
203 */
204 ldops = get_ldops(disc);
205 if (IS_ERR(ldops)) {
Alan Cox01e1abb2008-07-22 11:16:55 +0100206 request_module("tty-ldisc-%d", disc);
Linus Torvalds182274f2009-08-03 16:01:28 -0700207 ldops = get_ldops(disc);
208 if (IS_ERR(ldops))
209 return ERR_CAST(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100210 }
Linus Torvalds182274f2009-08-03 16:01:28 -0700211
212 ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
213 if (ld == NULL) {
214 put_ldops(ldops);
215 return ERR_PTR(-ENOMEM);
216 }
217
218 ld->ops = ldops;
219 atomic_set(&ld->users, 1);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100220 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100221}
222
Alan Cox852e99d2009-06-11 12:51:41 +0100223static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100224{
225 return (*pos < NR_LDISCS) ? pos : NULL;
226}
227
Alan Cox852e99d2009-06-11 12:51:41 +0100228static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100229{
230 (*pos)++;
231 return (*pos < NR_LDISCS) ? pos : NULL;
232}
233
234static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
235{
236}
237
238static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
239{
240 int i = *(loff_t *)v;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700241 struct tty_ldisc_ops *ldops;
Alan Cox852e99d2009-06-11 12:51:41 +0100242
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700243 ldops = get_ldops(i);
244 if (IS_ERR(ldops))
Alan Cox01e1abb2008-07-22 11:16:55 +0100245 return 0;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700246 seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
247 put_ldops(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100248 return 0;
249}
250
251static 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,
256};
257
258static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
259{
260 return seq_open(file, &tty_ldiscs_seq_ops);
261}
262
263const struct file_operations tty_ldiscs_proc_fops = {
264 .owner = THIS_MODULE,
265 .open = proc_tty_ldiscs_open,
266 .read = seq_read,
267 .llseek = seq_lseek,
268 .release = seq_release,
269};
270
271/**
272 * tty_ldisc_assign - set ldisc on a tty
273 * @tty: tty to assign
274 * @ld: line discipline
275 *
276 * Install an instance of a line discipline into a tty structure. The
Alan Cox8d2ead72009-06-16 17:00:26 +0100277 * ldisc must have a reference count above zero to ensure it remains.
Alan Cox01e1abb2008-07-22 11:16:55 +0100278 * The tty instance refcount starts at zero.
279 *
280 * Locking:
281 * Caller must hold references
282 */
283
284static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
285{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100286 tty->ldisc = ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100287}
288
289/**
290 * tty_ldisc_try - internal helper
291 * @tty: the tty
292 *
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
296 * of tty_ldisc_ref
297 *
298 * Locking: takes tty_ldisc_lock
299 */
300
Linus Torvalds65b77042009-08-03 11:11:19 -0700301static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
Alan Cox01e1abb2008-07-22 11:16:55 +0100302{
303 unsigned long flags;
304 struct tty_ldisc *ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100305
306 spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700307 ld = NULL;
308 if (test_bit(TTY_LDISC, &tty->flags))
309 ld = get_ldisc(tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100310 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700311 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100312}
313
314/**
315 * tty_ldisc_ref_wait - wait for the tty ldisc
316 * @tty: tty device
317 *
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.
321 *
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)
326 *
327 * Locking: call functions take tty_ldisc_lock
328 */
329
330struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
331{
Linus Torvalds65b77042009-08-03 11:11:19 -0700332 struct tty_ldisc *ld;
333
Alan Cox01e1abb2008-07-22 11:16:55 +0100334 /* wait_event is a macro */
Linus Torvalds65b77042009-08-03 11:11:19 -0700335 wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
336 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100337}
Alan Cox01e1abb2008-07-22 11:16:55 +0100338EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
339
340/**
341 * tty_ldisc_ref - get the tty ldisc
342 * @tty: tty device
343 *
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.
347 *
348 * Locking: called functions take tty_ldisc_lock
349 */
350
351struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
352{
Linus Torvalds65b77042009-08-03 11:11:19 -0700353 return tty_ldisc_try(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100354}
Alan Cox01e1abb2008-07-22 11:16:55 +0100355EXPORT_SYMBOL_GPL(tty_ldisc_ref);
356
357/**
358 * tty_ldisc_deref - free a tty ldisc reference
359 * @ld: reference to free up
360 *
361 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
362 * be called in IRQ context.
363 *
364 * Locking: takes tty_ldisc_lock
365 */
366
367void tty_ldisc_deref(struct tty_ldisc *ld)
368{
Linus Torvalds65b77042009-08-03 11:11:19 -0700369 put_ldisc(ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100370}
Alan Cox01e1abb2008-07-22 11:16:55 +0100371EXPORT_SYMBOL_GPL(tty_ldisc_deref);
372
Linus Torvalds65b77042009-08-03 11:11:19 -0700373static inline void tty_ldisc_put(struct tty_ldisc *ld)
374{
375 put_ldisc(ld);
376}
377
Alan Cox01e1abb2008-07-22 11:16:55 +0100378/**
379 * tty_ldisc_enable - allow ldisc use
380 * @tty: terminal to activate ldisc on
381 *
382 * Set the TTY_LDISC flag when the line discipline can be called
Alan Coxc9b39762009-01-02 13:44:56 +0000383 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
384 * changing flag to indicate any ldisc change is now over.
Alan Cox01e1abb2008-07-22 11:16:55 +0100385 *
Alan Coxc9b39762009-01-02 13:44:56 +0000386 * Note: nobody should set the TTY_LDISC bit except via this function.
387 * Clearing directly is allowed.
Alan Cox01e1abb2008-07-22 11:16:55 +0100388 */
389
390void tty_ldisc_enable(struct tty_struct *tty)
391{
392 set_bit(TTY_LDISC, &tty->flags);
Alan Coxc9b39762009-01-02 13:44:56 +0000393 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100394 wake_up(&tty_ldisc_wait);
395}
396
397/**
Alan Coxf2c4c652009-06-11 12:50:58 +0100398 * tty_ldisc_flush - flush line discipline queue
399 * @tty: tty
400 *
401 * Flush the line discipline queue (if any) for this tty. If there
402 * is no line discipline active this is a no-op.
403 */
404
405void tty_ldisc_flush(struct tty_struct *tty)
406{
407 struct tty_ldisc *ld = tty_ldisc_ref(tty);
408 if (ld) {
409 if (ld->ops->flush_buffer)
410 ld->ops->flush_buffer(tty);
411 tty_ldisc_deref(ld);
412 }
413 tty_buffer_flush(tty);
414}
Alan Coxf2c4c652009-06-11 12:50:58 +0100415EXPORT_SYMBOL_GPL(tty_ldisc_flush);
416
417/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100418 * tty_set_termios_ldisc - set ldisc field
419 * @tty: tty structure
420 * @num: line discipline number
421 *
422 * This is probably overkill for real world processors but
423 * they are not on hot paths so a little discipline won't do
424 * any harm.
425 *
426 * Locking: takes termios_mutex
427 */
428
429static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
430{
431 mutex_lock(&tty->termios_mutex);
432 tty->termios->c_line = num;
433 mutex_unlock(&tty->termios_mutex);
434}
435
Alan Coxc65c9bc2009-06-11 12:50:12 +0100436/**
437 * tty_ldisc_open - open a line discipline
438 * @tty: tty we are opening the ldisc on
439 * @ld: discipline to open
440 *
441 * A helper opening method. Also a convenient debugging and check
442 * point.
Arnd Bergmannec79d602010-06-01 22:53:01 +0200443 *
444 * Locking: always called with BTM already held.
Alan Coxc65c9bc2009-06-11 12:50:12 +0100445 */
446
447static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
448{
449 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
Alan Coxf18f9492009-11-30 13:18:35 +0000450 if (ld->ops->open) {
451 int ret;
Arnd Bergmannec79d602010-06-01 22:53:01 +0200452 /* BTM here locks versus a hangup event */
Arnd Bergmannddcd9fb2010-06-01 22:53:08 +0200453 WARN_ON(!tty_locked());
Alan Coxf18f9492009-11-30 13:18:35 +0000454 ret = ld->ops->open(tty);
Jiri Slaby7f90cfc2010-11-25 00:27:54 +0100455 if (ret)
456 clear_bit(TTY_LDISC_OPEN, &tty->flags);
Alan Coxf18f9492009-11-30 13:18:35 +0000457 return ret;
458 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100459 return 0;
460}
461
462/**
463 * tty_ldisc_close - close a line discipline
464 * @tty: tty we are opening the ldisc on
465 * @ld: discipline to close
466 *
467 * A helper close method. Also a convenient debugging and check
468 * point.
469 */
470
471static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
472{
473 WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
474 clear_bit(TTY_LDISC_OPEN, &tty->flags);
475 if (ld->ops->close)
476 ld->ops->close(tty);
477}
Alan Cox01e1abb2008-07-22 11:16:55 +0100478
479/**
480 * tty_ldisc_restore - helper for tty ldisc change
481 * @tty: tty to recover
482 * @old: previous ldisc
483 *
484 * Restore the previous line discipline or N_TTY when a line discipline
485 * change fails due to an open error
486 */
487
488static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
489{
490 char buf[64];
Alan Coxc65c9bc2009-06-11 12:50:12 +0100491 struct tty_ldisc *new_ldisc;
492 int r;
Alan Cox01e1abb2008-07-22 11:16:55 +0100493
494 /* There is an outstanding reference here so this is safe */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100495 old = tty_ldisc_get(old->ops->num);
496 WARN_ON(IS_ERR(old));
Alan Cox01e1abb2008-07-22 11:16:55 +0100497 tty_ldisc_assign(tty, old);
498 tty_set_termios_ldisc(tty, old->ops->num);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100499 if (tty_ldisc_open(tty, old) < 0) {
500 tty_ldisc_put(old);
Alan Cox01e1abb2008-07-22 11:16:55 +0100501 /* This driver is always present */
Alan Cox852e99d2009-06-11 12:51:41 +0100502 new_ldisc = tty_ldisc_get(N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100503 if (IS_ERR(new_ldisc))
Alan Cox01e1abb2008-07-22 11:16:55 +0100504 panic("n_tty: get");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100505 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100506 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100507 r = tty_ldisc_open(tty, new_ldisc);
508 if (r < 0)
509 panic("Couldn't open N_TTY ldisc for "
510 "%s --- error %d.",
511 tty_name(tty, buf), r);
Alan Cox01e1abb2008-07-22 11:16:55 +0100512 }
513}
514
515/**
Alan Coxc65c9bc2009-06-11 12:50:12 +0100516 * tty_ldisc_halt - shut down the line discipline
Alan Coxe8b70e72009-06-11 12:48:02 +0100517 * @tty: tty device
518 *
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.
523 *
Linus Torvalds5c58cef2009-08-25 09:12:43 -0700524 * 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
526 * flushed.
Alan Coxe8b70e72009-06-11 12:48:02 +0100527 */
528
Alan Coxc65c9bc2009-06-11 12:50:12 +0100529static int tty_ldisc_halt(struct tty_struct *tty)
Alan Coxe8b70e72009-06-11 12:48:02 +0100530{
531 clear_bit(TTY_LDISC, &tty->flags);
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700532 return cancel_work_sync(&tty->buf.work);
Alan Coxe8b70e72009-06-11 12:48:02 +0100533}
534
535/**
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100536 * tty_ldisc_flush_works - flush all works of a tty
537 * @tty: tty device to flush works for
538 *
539 * Sync flush all works belonging to @tty.
540 */
541static void tty_ldisc_flush_works(struct tty_struct *tty)
542{
543 flush_work_sync(&tty->hangup_work);
544 flush_work_sync(&tty->SAK_work);
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700545 flush_work_sync(&tty->buf.work);
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100546}
547
548/**
Jiri Slaby100eeae2010-10-31 23:17:51 +0100549 * tty_ldisc_wait_idle - wait for the ldisc to become idle
550 * @tty: tty to wait for
551 *
552 * Wait for the line discipline to become idle. The discipline must
553 * have been halted for this to guarantee it remains idle.
554 */
555static int tty_ldisc_wait_idle(struct tty_struct *tty)
556{
557 int ret;
Jiri Slaby92f6fa02011-06-05 14:16:16 +0200558 ret = wait_event_timeout(tty_ldisc_idle,
Jiri Slaby100eeae2010-10-31 23:17:51 +0100559 atomic_read(&tty->ldisc->users) == 1, 5 * HZ);
560 if (ret < 0)
561 return ret;
562 return ret > 0 ? 0 : -EBUSY;
563}
564
565/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100566 * tty_set_ldisc - set line discipline
567 * @tty: the terminal to set
568 * @ldisc: the line discipline
569 *
570 * Set the discipline of a tty line. Must be called from a process
Alan Coxc65c9bc2009-06-11 12:50:12 +0100571 * context. The ldisc change logic has to protect itself against any
572 * overlapping ldisc change (including on the other end of pty pairs),
573 * the close of one side of a tty/pty pair, and eventually hangup.
Alan Cox01e1abb2008-07-22 11:16:55 +0100574 *
Alan Coxc65c9bc2009-06-11 12:50:12 +0100575 * Locking: takes tty_ldisc_lock, termios_mutex
Alan Cox01e1abb2008-07-22 11:16:55 +0100576 */
577
578int tty_set_ldisc(struct tty_struct *tty, int ldisc)
579{
580 int retval;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100581 struct tty_ldisc *o_ldisc, *new_ldisc;
582 int work, o_work = 0;
Alan Cox01e1abb2008-07-22 11:16:55 +0100583 struct tty_struct *o_tty;
584
Alan Coxc65c9bc2009-06-11 12:50:12 +0100585 new_ldisc = tty_ldisc_get(ldisc);
586 if (IS_ERR(new_ldisc))
587 return PTR_ERR(new_ldisc);
588
Arnd Bergmannec79d602010-06-01 22:53:01 +0200589 tty_lock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100590 /*
591 * We need to look at the tty locking here for pty/tty pairs
592 * when both sides try to change in parallel.
593 */
594
595 o_tty = tty->link; /* o_tty is the pty side or NULL */
596
597
598 /*
599 * Check the no-op case
600 */
601
602 if (tty->ldisc->ops->num == ldisc) {
Arnd Bergmannec79d602010-06-01 22:53:01 +0200603 tty_unlock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100604 tty_ldisc_put(new_ldisc);
605 return 0;
606 }
Alan Cox01e1abb2008-07-22 11:16:55 +0100607
Arnd Bergmannec79d602010-06-01 22:53:01 +0200608 tty_unlock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100609 /*
610 * Problem: What do we do if this blocks ?
Alan Coxc65c9bc2009-06-11 12:50:12 +0100611 * We could deadlock here
Alan Cox01e1abb2008-07-22 11:16:55 +0100612 */
613
614 tty_wait_until_sent(tty, 0);
615
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200616 tty_lock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100617 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100618
619 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100620 * We could be midstream of another ldisc change which has
621 * dropped the lock during processing. If so we need to wait.
622 */
623
624 while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
625 mutex_unlock(&tty->ldisc_mutex);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200626 tty_unlock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100627 wait_event(tty_ldisc_wait,
628 test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200629 tty_lock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100630 mutex_lock(&tty->ldisc_mutex);
631 }
Alan Coxeeb89d92009-11-30 13:18:29 +0000632
Alan Coxc65c9bc2009-06-11 12:50:12 +0100633 set_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox852e99d2009-06-11 12:51:41 +0100634
Alan Coxc65c9bc2009-06-11 12:50:12 +0100635 /*
Alan Cox01e1abb2008-07-22 11:16:55 +0100636 * No more input please, we are switching. The new ldisc
637 * will update this value in the ldisc open function
638 */
639
640 tty->receive_room = 0;
641
642 o_ldisc = tty->ldisc;
Alan Coxeeb89d92009-11-30 13:18:29 +0000643
Arnd Bergmannec79d602010-06-01 22:53:01 +0200644 tty_unlock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100645 /*
646 * Make sure we don't change while someone holds a
647 * reference to the line discipline. The TTY_LDISC bit
648 * prevents anyone taking a reference once it is clear.
649 * We need the lock to avoid racing reference takers.
Alan Coxc9b39762009-01-02 13:44:56 +0000650 *
651 * We must clear the TTY_LDISC bit here to avoid a livelock
652 * with a userspace app continually trying to use the tty in
653 * parallel to the change and re-referencing the tty.
Alan Cox01e1abb2008-07-22 11:16:55 +0100654 */
655
Alan Coxc65c9bc2009-06-11 12:50:12 +0100656 work = tty_ldisc_halt(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100657 if (o_tty)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100658 o_work = tty_ldisc_halt(o_tty);
659
Alan Cox01e1abb2008-07-22 11:16:55 +0100660 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100661 * Wait for ->hangup_work and ->buf.work handlers to terminate.
662 * We must drop the mutex here in case a hangup is also in process.
Alan Cox01e1abb2008-07-22 11:16:55 +0100663 */
664
Alan Coxc65c9bc2009-06-11 12:50:12 +0100665 mutex_unlock(&tty->ldisc_mutex);
666
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100667 tty_ldisc_flush_works(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100668
Jiri Slaby100eeae2010-10-31 23:17:51 +0100669 retval = tty_ldisc_wait_idle(tty);
670
Arnd Bergmannec79d602010-06-01 22:53:01 +0200671 tty_lock();
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200672 mutex_lock(&tty->ldisc_mutex);
Jiri Slaby100eeae2010-10-31 23:17:51 +0100673
674 /* handle wait idle failure locked */
675 if (retval) {
676 tty_ldisc_put(new_ldisc);
677 goto enable;
678 }
679
Alan Coxc65c9bc2009-06-11 12:50:12 +0100680 if (test_bit(TTY_HUPPED, &tty->flags)) {
681 /* We were raced by the hangup method. It will have stomped
682 the ldisc data and closed the ldisc down */
683 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
684 mutex_unlock(&tty->ldisc_mutex);
685 tty_ldisc_put(new_ldisc);
Arnd Bergmannec79d602010-06-01 22:53:01 +0200686 tty_unlock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100687 return -EIO;
688 }
689
Alan Cox01e1abb2008-07-22 11:16:55 +0100690 /* Shutdown the current discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100691 tty_ldisc_close(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100692
693 /* Now set up the new line discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100694 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100695 tty_set_termios_ldisc(tty, ldisc);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100696
697 retval = tty_ldisc_open(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100698 if (retval < 0) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100699 /* Back to the old one or N_TTY if we can't */
700 tty_ldisc_put(new_ldisc);
701 tty_ldisc_restore(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100702 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100703
Alan Cox01e1abb2008-07-22 11:16:55 +0100704 /* At this point we hold a reference to the new ldisc and a
705 a reference to the old ldisc. If we ended up flipping back
706 to the existing ldisc we have two references to it */
707
Alan Coxc65c9bc2009-06-11 12:50:12 +0100708 if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100709 tty->ops->set_ldisc(tty);
710
Alan Coxc65c9bc2009-06-11 12:50:12 +0100711 tty_ldisc_put(o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100712
Jiri Slaby100eeae2010-10-31 23:17:51 +0100713enable:
Alan Cox01e1abb2008-07-22 11:16:55 +0100714 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100715 * Allow ldisc referencing to occur again
Alan Cox01e1abb2008-07-22 11:16:55 +0100716 */
717
718 tty_ldisc_enable(tty);
719 if (o_tty)
720 tty_ldisc_enable(o_tty);
721
Alan Coxc65c9bc2009-06-11 12:50:12 +0100722 /* Restart the work queue in case no characters kick it off. Safe if
Alan Cox01e1abb2008-07-22 11:16:55 +0100723 already running */
724 if (work)
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700725 schedule_work(&tty->buf.work);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100726 if (o_work)
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700727 schedule_work(&o_tty->buf.work);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100728 mutex_unlock(&tty->ldisc_mutex);
Arnd Bergmannec79d602010-06-01 22:53:01 +0200729 tty_unlock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100730 return retval;
731}
732
Alan Coxc65c9bc2009-06-11 12:50:12 +0100733/**
734 * tty_reset_termios - reset terminal state
735 * @tty: tty to reset
736 *
737 * Restore a terminal to the driver default state.
738 */
739
740static void tty_reset_termios(struct tty_struct *tty)
741{
742 mutex_lock(&tty->termios_mutex);
743 *tty->termios = tty->driver->init_termios;
744 tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
745 tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
746 mutex_unlock(&tty->termios_mutex);
747}
748
749
750/**
751 * tty_ldisc_reinit - reinitialise the tty ldisc
752 * @tty: tty to reinit
Alan Cox638b9642010-02-08 10:09:26 +0000753 * @ldisc: line discipline to reinitialize
Alan Coxc65c9bc2009-06-11 12:50:12 +0100754 *
Alan Cox638b9642010-02-08 10:09:26 +0000755 * Switch the tty to a line discipline and leave the ldisc
756 * state closed
Alan Coxc65c9bc2009-06-11 12:50:12 +0100757 */
758
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200759static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100760{
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200761 struct tty_ldisc *ld = tty_ldisc_get(ldisc);
762
763 if (IS_ERR(ld))
764 return -1;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100765
Jiri Slaby92f6fa02011-06-05 14:16:16 +0200766 WARN_ON_ONCE(tty_ldisc_wait_idle(tty));
767
Alan Coxc65c9bc2009-06-11 12:50:12 +0100768 tty_ldisc_close(tty, tty->ldisc);
769 tty_ldisc_put(tty->ldisc);
770 tty->ldisc = NULL;
771 /*
772 * Switch the line discipline back
773 */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100774 tty_ldisc_assign(tty, ld);
Alan Cox638b9642010-02-08 10:09:26 +0000775 tty_set_termios_ldisc(tty, ldisc);
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200776
777 return 0;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100778}
779
780/**
781 * tty_ldisc_hangup - hangup ldisc reset
782 * @tty: tty being hung up
783 *
784 * Some tty devices reset their termios when they receive a hangup
785 * event. In that situation we must also switch back to N_TTY properly
786 * before we reset the termios data.
787 *
788 * Locking: We can take the ldisc mutex as the rest of the code is
789 * careful to allow for this.
790 *
791 * In the pty pair case this occurs in the close() path of the
792 * tty itself so we must be careful about locking rules.
793 */
794
795void tty_ldisc_hangup(struct tty_struct *tty)
796{
797 struct tty_ldisc *ld;
Alan Cox638b9642010-02-08 10:09:26 +0000798 int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
799 int err = 0;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100800
801 /*
802 * FIXME! What are the locking issues here? This may me overdoing
803 * things... This question is especially important now that we've
804 * removed the irqlock.
805 */
806 ld = tty_ldisc_ref(tty);
807 if (ld != NULL) {
808 /* We may have no line discipline at this point */
809 if (ld->ops->flush_buffer)
810 ld->ops->flush_buffer(tty);
811 tty_driver_flush_buffer(tty);
812 if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
813 ld->ops->write_wakeup)
814 ld->ops->write_wakeup(tty);
815 if (ld->ops->hangup)
816 ld->ops->hangup(tty);
817 tty_ldisc_deref(ld);
818 }
819 /*
820 * FIXME: Once we trust the LDISC code better we can wait here for
821 * ldisc completion and fix the driver call race
822 */
823 wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
824 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
825 /*
826 * Shutdown the current line discipline, and reset it to
Alan Cox638b9642010-02-08 10:09:26 +0000827 * N_TTY if need be.
828 *
829 * Avoid racing set_ldisc or tty_ldisc_release
Alan Coxc65c9bc2009-06-11 12:50:12 +0100830 */
Alan Cox638b9642010-02-08 10:09:26 +0000831 mutex_lock(&tty->ldisc_mutex);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200832
833 /*
834 * this is like tty_ldisc_halt, but we need to give up
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700835 * the BTM before calling cancel_work_sync, which may
836 * need to wait for another function taking the BTM
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200837 */
838 clear_bit(TTY_LDISC, &tty->flags);
839 tty_unlock();
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700840 cancel_work_sync(&tty->buf.work);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200841 mutex_unlock(&tty->ldisc_mutex);
842
843 tty_lock();
844 mutex_lock(&tty->ldisc_mutex);
845
Alan Cox638b9642010-02-08 10:09:26 +0000846 /* At this point we have a closed ldisc and we want to
847 reopen it. We could defer this to the next open but
848 it means auditing a lot of other paths so this is
849 a FIXME */
850 if (tty->ldisc) { /* Not yet closed */
851 if (reset == 0) {
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200852
853 if (!tty_ldisc_reinit(tty, tty->termios->c_line))
854 err = tty_ldisc_open(tty, tty->ldisc);
855 else
856 err = 1;
Alan Coxc8d50042009-07-16 16:05:08 +0100857 }
Alan Cox638b9642010-02-08 10:09:26 +0000858 /* If the re-open fails or we reset then go to N_TTY. The
859 N_TTY open cannot fail */
860 if (reset || err) {
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200861 BUG_ON(tty_ldisc_reinit(tty, N_TTY));
Alan Cox638b9642010-02-08 10:09:26 +0000862 WARN_ON(tty_ldisc_open(tty, tty->ldisc));
863 }
864 tty_ldisc_enable(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100865 }
Alan Cox638b9642010-02-08 10:09:26 +0000866 mutex_unlock(&tty->ldisc_mutex);
867 if (reset)
868 tty_reset_termios(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100869}
Alan Cox01e1abb2008-07-22 11:16:55 +0100870
871/**
872 * tty_ldisc_setup - open line discipline
873 * @tty: tty being shut down
874 * @o_tty: pair tty for pty/tty pairs
875 *
876 * Called during the initial open of a tty/pty pair in order to set up the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100877 * line disciplines and bind them to the tty. This has no locking issues
878 * as the device isn't yet active.
Alan Cox01e1abb2008-07-22 11:16:55 +0100879 */
880
881int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
882{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100883 struct tty_ldisc *ld = tty->ldisc;
Alan Cox01e1abb2008-07-22 11:16:55 +0100884 int retval;
885
Alan Coxc65c9bc2009-06-11 12:50:12 +0100886 retval = tty_ldisc_open(tty, ld);
887 if (retval)
888 return retval;
889
890 if (o_tty) {
891 retval = tty_ldisc_open(o_tty, o_tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100892 if (retval) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100893 tty_ldisc_close(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100894 return retval;
895 }
896 tty_ldisc_enable(o_tty);
897 }
898 tty_ldisc_enable(tty);
899 return 0;
900}
Alan Cox01e1abb2008-07-22 11:16:55 +0100901/**
902 * tty_ldisc_release - release line discipline
903 * @tty: tty being shut down
904 * @o_tty: pair tty for pty/tty pairs
905 *
Alan Cox852e99d2009-06-11 12:51:41 +0100906 * Called during the final close of a tty/pty pair in order to shut down
907 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100908 * ldisc has not been opened.
Alan Cox01e1abb2008-07-22 11:16:55 +0100909 */
910
911void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
912{
Alan Cox01e1abb2008-07-22 11:16:55 +0100913 /*
914 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
915 * kill any delayed work. As this is the final close it does not
916 * race with the set_ldisc code path.
917 */
Alan Cox01e1abb2008-07-22 11:16:55 +0100918
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200919 tty_unlock();
Alan Coxe8b70e72009-06-11 12:48:02 +0100920 tty_ldisc_halt(tty);
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100921 tty_ldisc_flush_works(tty);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200922 tty_lock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100923
Alan Coxc8d50042009-07-16 16:05:08 +0100924 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100925 /*
Alan Coxaef29bc2009-06-29 15:21:47 +0100926 * Now kill off the ldisc
Alan Cox01e1abb2008-07-22 11:16:55 +0100927 */
Alan Coxaef29bc2009-06-29 15:21:47 +0100928 tty_ldisc_close(tty, tty->ldisc);
929 tty_ldisc_put(tty->ldisc);
930 /* Force an oops if we mess this up */
931 tty->ldisc = NULL;
Alan Cox01e1abb2008-07-22 11:16:55 +0100932
Alan Coxaef29bc2009-06-29 15:21:47 +0100933 /* Ensure the next open requests the N_TTY ldisc */
934 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc8d50042009-07-16 16:05:08 +0100935 mutex_unlock(&tty->ldisc_mutex);
Alan Coxaef29bc2009-06-29 15:21:47 +0100936
Alan Coxc65c9bc2009-06-11 12:50:12 +0100937 /* This will need doing differently if we need to lock */
938 if (o_tty)
939 tty_ldisc_release(o_tty, NULL);
Alan Coxaef29bc2009-06-29 15:21:47 +0100940
941 /* And the memory resources remaining (buffers, termios) will be
942 disposed of when the kref hits zero */
Alan Cox01e1abb2008-07-22 11:16:55 +0100943}
944
945/**
946 * tty_ldisc_init - ldisc setup for new tty
947 * @tty: tty being allocated
948 *
949 * Set up the line discipline objects for a newly allocated tty. Note that
950 * the tty structure is not completely set up when this call is made.
951 */
952
953void tty_ldisc_init(struct tty_struct *tty)
954{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100955 struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
956 if (IS_ERR(ld))
Alan Cox01e1abb2008-07-22 11:16:55 +0100957 panic("n_tty: init_tty");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100958 tty_ldisc_assign(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100959}
960
Jiri Slaby67166712011-03-23 10:48:35 +0100961/**
962 * tty_ldisc_init - ldisc cleanup for new tty
963 * @tty: tty that was allocated recently
964 *
965 * The tty structure must not becompletely set up (tty_ldisc_setup) when
966 * this call is made.
967 */
968void tty_ldisc_deinit(struct tty_struct *tty)
969{
970 put_ldisc(tty->ldisc);
971 tty_ldisc_assign(tty, NULL);
972}
973
Alan Cox01e1abb2008-07-22 11:16:55 +0100974void tty_ldisc_begin(void)
975{
976 /* Setup the default TTY line discipline. */
977 (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
978}