blob: 24b95db75d84f8d6f42705bdfb57b622abcce322 [file] [log] [blame]
Alan Cox01e1abb2008-07-22 11:16:55 +01001#include <linux/types.h>
Alan Cox01e1abb2008-07-22 11:16:55 +01002#include <linux/errno.h>
Jiri Slaby8b3ffa12011-11-16 16:27:10 +01003#include <linux/kmod.h>
Alan Cox01e1abb2008-07-22 11:16:55 +01004#include <linux/sched.h>
5#include <linux/interrupt.h>
6#include <linux/tty.h>
7#include <linux/tty_driver.h>
Alan Cox01e1abb2008-07-22 11:16:55 +01008#include <linux/file.h>
Alan Cox01e1abb2008-07-22 11:16:55 +01009#include <linux/mm.h>
10#include <linux/string.h>
11#include <linux/slab.h>
12#include <linux/poll.h>
13#include <linux/proc_fs.h>
14#include <linux/init.h>
15#include <linux/module.h>
Alan Cox01e1abb2008-07-22 11:16:55 +010016#include <linux/device.h>
17#include <linux/wait.h>
18#include <linux/bitops.h>
Alan Cox01e1abb2008-07-22 11:16:55 +010019#include <linux/seq_file.h>
Alan Cox01e1abb2008-07-22 11:16:55 +010020#include <linux/uaccess.h>
Jiri Slaby0c73c082011-11-16 16:27:09 +010021#include <linux/ratelimit.h>
Alan Cox01e1abb2008-07-22 11:16:55 +010022
23/*
24 * This guards the refcounted line discipline lists. The lock
25 * must be taken with irqs off because there are hangup path
26 * callers who will do ldisc lookups and cannot sleep.
27 */
28
29static DEFINE_SPINLOCK(tty_ldisc_lock);
30static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
Jiri Slaby100eeae2010-10-31 23:17:51 +010031static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_idle);
Alan Cox01e1abb2008-07-22 11:16:55 +010032/* Line disc dispatch table */
33static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
34
Linus Torvalds65b77042009-08-03 11:11:19 -070035static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
36{
37 if (ld)
38 atomic_inc(&ld->users);
39 return ld;
40}
41
Linus Torvaldscbe93522009-08-03 14:54:56 -070042static void put_ldisc(struct tty_ldisc *ld)
Linus Torvalds65b77042009-08-03 11:11:19 -070043{
Linus Torvaldscbe93522009-08-03 14:54:56 -070044 unsigned long flags;
45
Linus Torvalds65b77042009-08-03 11:11:19 -070046 if (WARN_ON_ONCE(!ld))
47 return;
48
49 /*
50 * If this is the last user, free the ldisc, and
51 * release the ldisc ops.
Linus Torvaldscbe93522009-08-03 14:54:56 -070052 *
53 * We really want an "atomic_dec_and_lock_irqsave()",
54 * but we don't have it, so this does it by hand.
Linus Torvalds65b77042009-08-03 11:11:19 -070055 */
Linus Torvaldscbe93522009-08-03 14:54:56 -070056 local_irq_save(flags);
57 if (atomic_dec_and_lock(&ld->users, &tty_ldisc_lock)) {
Linus Torvalds65b77042009-08-03 11:11:19 -070058 struct tty_ldisc_ops *ldo = ld->ops;
59
Linus Torvalds65b77042009-08-03 11:11:19 -070060 ldo->refcount--;
61 module_put(ldo->owner);
62 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvaldscbe93522009-08-03 14:54:56 -070063
64 kfree(ld);
65 return;
Linus Torvalds65b77042009-08-03 11:11:19 -070066 }
Linus Torvaldscbe93522009-08-03 14:54:56 -070067 local_irq_restore(flags);
Jiri Slaby100eeae2010-10-31 23:17:51 +010068 wake_up(&tty_ldisc_idle);
Linus Torvalds65b77042009-08-03 11:11:19 -070069}
70
Alan Cox01e1abb2008-07-22 11:16:55 +010071/**
72 * tty_register_ldisc - install a line discipline
73 * @disc: ldisc number
74 * @new_ldisc: pointer to the ldisc object
75 *
76 * Installs a new line discipline into the kernel. The discipline
77 * is set up as unreferenced and then made available to the kernel
78 * from this point onwards.
79 *
80 * Locking:
81 * takes tty_ldisc_lock to guard against ldisc races
82 */
83
84int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
85{
86 unsigned long flags;
87 int ret = 0;
88
89 if (disc < N_TTY || disc >= NR_LDISCS)
90 return -EINVAL;
91
92 spin_lock_irqsave(&tty_ldisc_lock, flags);
93 tty_ldiscs[disc] = new_ldisc;
94 new_ldisc->num = disc;
95 new_ldisc->refcount = 0;
96 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
97
98 return ret;
99}
100EXPORT_SYMBOL(tty_register_ldisc);
101
102/**
103 * tty_unregister_ldisc - unload a line discipline
104 * @disc: ldisc number
105 * @new_ldisc: pointer to the ldisc object
106 *
107 * Remove a line discipline from the kernel providing it is not
108 * currently in use.
109 *
110 * Locking:
111 * takes tty_ldisc_lock to guard against ldisc races
112 */
113
114int tty_unregister_ldisc(int disc)
115{
116 unsigned long flags;
117 int ret = 0;
118
119 if (disc < N_TTY || disc >= NR_LDISCS)
120 return -EINVAL;
121
122 spin_lock_irqsave(&tty_ldisc_lock, flags);
123 if (tty_ldiscs[disc]->refcount)
124 ret = -EBUSY;
125 else
126 tty_ldiscs[disc] = NULL;
127 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
128
129 return ret;
130}
131EXPORT_SYMBOL(tty_unregister_ldisc);
132
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700133static struct tty_ldisc_ops *get_ldops(int disc)
134{
135 unsigned long flags;
136 struct tty_ldisc_ops *ldops, *ret;
137
138 spin_lock_irqsave(&tty_ldisc_lock, flags);
139 ret = ERR_PTR(-EINVAL);
140 ldops = tty_ldiscs[disc];
141 if (ldops) {
142 ret = ERR_PTR(-EAGAIN);
143 if (try_module_get(ldops->owner)) {
144 ldops->refcount++;
145 ret = ldops;
146 }
147 }
148 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
149 return ret;
150}
151
152static void put_ldops(struct tty_ldisc_ops *ldops)
153{
154 unsigned long flags;
155
156 spin_lock_irqsave(&tty_ldisc_lock, flags);
157 ldops->refcount--;
158 module_put(ldops->owner);
159 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
160}
Alan Cox01e1abb2008-07-22 11:16:55 +0100161
162/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100163 * tty_ldisc_get - take a reference to an ldisc
164 * @disc: ldisc number
Alan Cox01e1abb2008-07-22 11:16:55 +0100165 *
166 * Takes a reference to a line discipline. Deals with refcounts and
167 * module locking counts. Returns NULL if the discipline is not available.
168 * Returns a pointer to the discipline and bumps the ref count if it is
169 * available
170 *
171 * Locking:
172 * takes tty_ldisc_lock to guard against ldisc races
173 */
174
Alan Coxc65c9bc2009-06-11 12:50:12 +0100175static struct tty_ldisc *tty_ldisc_get(int disc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100176{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100177 struct tty_ldisc *ld;
Linus Torvalds182274f2009-08-03 16:01:28 -0700178 struct tty_ldisc_ops *ldops;
Alan Cox01e1abb2008-07-22 11:16:55 +0100179
180 if (disc < N_TTY || disc >= NR_LDISCS)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100181 return ERR_PTR(-EINVAL);
Linus Torvalds182274f2009-08-03 16:01:28 -0700182
183 /*
184 * Get the ldisc ops - we may need to request them to be loaded
185 * dynamically and try again.
186 */
187 ldops = get_ldops(disc);
188 if (IS_ERR(ldops)) {
Alan Cox01e1abb2008-07-22 11:16:55 +0100189 request_module("tty-ldisc-%d", disc);
Linus Torvalds182274f2009-08-03 16:01:28 -0700190 ldops = get_ldops(disc);
191 if (IS_ERR(ldops))
192 return ERR_CAST(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100193 }
Linus Torvalds182274f2009-08-03 16:01:28 -0700194
195 ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
196 if (ld == NULL) {
197 put_ldops(ldops);
198 return ERR_PTR(-ENOMEM);
199 }
200
201 ld->ops = ldops;
202 atomic_set(&ld->users, 1);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100203 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100204}
205
Alan Cox852e99d2009-06-11 12:51:41 +0100206static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100207{
208 return (*pos < NR_LDISCS) ? pos : NULL;
209}
210
Alan Cox852e99d2009-06-11 12:51:41 +0100211static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100212{
213 (*pos)++;
214 return (*pos < NR_LDISCS) ? pos : NULL;
215}
216
217static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
218{
219}
220
221static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
222{
223 int i = *(loff_t *)v;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700224 struct tty_ldisc_ops *ldops;
Alan Cox852e99d2009-06-11 12:51:41 +0100225
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700226 ldops = get_ldops(i);
227 if (IS_ERR(ldops))
Alan Cox01e1abb2008-07-22 11:16:55 +0100228 return 0;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700229 seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
230 put_ldops(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100231 return 0;
232}
233
234static const struct seq_operations tty_ldiscs_seq_ops = {
235 .start = tty_ldiscs_seq_start,
236 .next = tty_ldiscs_seq_next,
237 .stop = tty_ldiscs_seq_stop,
238 .show = tty_ldiscs_seq_show,
239};
240
241static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
242{
243 return seq_open(file, &tty_ldiscs_seq_ops);
244}
245
246const struct file_operations tty_ldiscs_proc_fops = {
247 .owner = THIS_MODULE,
248 .open = proc_tty_ldiscs_open,
249 .read = seq_read,
250 .llseek = seq_lseek,
251 .release = seq_release,
252};
253
254/**
255 * tty_ldisc_assign - set ldisc on a tty
256 * @tty: tty to assign
257 * @ld: line discipline
258 *
259 * Install an instance of a line discipline into a tty structure. The
Alan Cox8d2ead72009-06-16 17:00:26 +0100260 * ldisc must have a reference count above zero to ensure it remains.
Alan Cox01e1abb2008-07-22 11:16:55 +0100261 * The tty instance refcount starts at zero.
262 *
263 * Locking:
264 * Caller must hold references
265 */
266
267static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
268{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100269 tty->ldisc = ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100270}
271
272/**
273 * tty_ldisc_try - internal helper
274 * @tty: the tty
275 *
276 * Make a single attempt to grab and bump the refcount on
277 * the tty ldisc. Return 0 on failure or 1 on success. This is
278 * used to implement both the waiting and non waiting versions
279 * of tty_ldisc_ref
280 *
281 * Locking: takes tty_ldisc_lock
282 */
283
Linus Torvalds65b77042009-08-03 11:11:19 -0700284static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
Alan Cox01e1abb2008-07-22 11:16:55 +0100285{
286 unsigned long flags;
287 struct tty_ldisc *ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100288
289 spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700290 ld = NULL;
291 if (test_bit(TTY_LDISC, &tty->flags))
292 ld = get_ldisc(tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100293 spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700294 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100295}
296
297/**
298 * tty_ldisc_ref_wait - wait for the tty ldisc
299 * @tty: tty device
300 *
301 * Dereference the line discipline for the terminal and take a
302 * reference to it. If the line discipline is in flux then
303 * wait patiently until it changes.
304 *
305 * Note: Must not be called from an IRQ/timer context. The caller
306 * must also be careful not to hold other locks that will deadlock
307 * against a discipline change, such as an existing ldisc reference
308 * (which we check for)
309 *
310 * Locking: call functions take tty_ldisc_lock
311 */
312
313struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
314{
Linus Torvalds65b77042009-08-03 11:11:19 -0700315 struct tty_ldisc *ld;
316
Alan Cox01e1abb2008-07-22 11:16:55 +0100317 /* wait_event is a macro */
Linus Torvalds65b77042009-08-03 11:11:19 -0700318 wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
319 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100320}
Alan Cox01e1abb2008-07-22 11:16:55 +0100321EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
322
323/**
324 * tty_ldisc_ref - get the tty ldisc
325 * @tty: tty device
326 *
327 * Dereference the line discipline for the terminal and take a
328 * reference to it. If the line discipline is in flux then
329 * return NULL. Can be called from IRQ and timer functions.
330 *
331 * Locking: called functions take tty_ldisc_lock
332 */
333
334struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
335{
Linus Torvalds65b77042009-08-03 11:11:19 -0700336 return tty_ldisc_try(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100337}
Alan Cox01e1abb2008-07-22 11:16:55 +0100338EXPORT_SYMBOL_GPL(tty_ldisc_ref);
339
340/**
341 * tty_ldisc_deref - free a tty ldisc reference
342 * @ld: reference to free up
343 *
344 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
345 * be called in IRQ context.
346 *
347 * Locking: takes tty_ldisc_lock
348 */
349
350void tty_ldisc_deref(struct tty_ldisc *ld)
351{
Linus Torvalds65b77042009-08-03 11:11:19 -0700352 put_ldisc(ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100353}
Alan Cox01e1abb2008-07-22 11:16:55 +0100354EXPORT_SYMBOL_GPL(tty_ldisc_deref);
355
Linus Torvalds65b77042009-08-03 11:11:19 -0700356static inline void tty_ldisc_put(struct tty_ldisc *ld)
357{
358 put_ldisc(ld);
359}
360
Alan Cox01e1abb2008-07-22 11:16:55 +0100361/**
362 * tty_ldisc_enable - allow ldisc use
363 * @tty: terminal to activate ldisc on
364 *
365 * Set the TTY_LDISC flag when the line discipline can be called
Alan Coxc9b39762009-01-02 13:44:56 +0000366 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
367 * changing flag to indicate any ldisc change is now over.
Alan Cox01e1abb2008-07-22 11:16:55 +0100368 *
Alan Coxc9b39762009-01-02 13:44:56 +0000369 * Note: nobody should set the TTY_LDISC bit except via this function.
370 * Clearing directly is allowed.
Alan Cox01e1abb2008-07-22 11:16:55 +0100371 */
372
373void tty_ldisc_enable(struct tty_struct *tty)
374{
375 set_bit(TTY_LDISC, &tty->flags);
Alan Coxc9b39762009-01-02 13:44:56 +0000376 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100377 wake_up(&tty_ldisc_wait);
378}
379
380/**
Alan Coxf2c4c652009-06-11 12:50:58 +0100381 * tty_ldisc_flush - flush line discipline queue
382 * @tty: tty
383 *
384 * Flush the line discipline queue (if any) for this tty. If there
385 * is no line discipline active this is a no-op.
386 */
387
388void tty_ldisc_flush(struct tty_struct *tty)
389{
390 struct tty_ldisc *ld = tty_ldisc_ref(tty);
391 if (ld) {
392 if (ld->ops->flush_buffer)
393 ld->ops->flush_buffer(tty);
394 tty_ldisc_deref(ld);
395 }
396 tty_buffer_flush(tty);
397}
Alan Coxf2c4c652009-06-11 12:50:58 +0100398EXPORT_SYMBOL_GPL(tty_ldisc_flush);
399
400/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100401 * tty_set_termios_ldisc - set ldisc field
402 * @tty: tty structure
403 * @num: line discipline number
404 *
405 * This is probably overkill for real world processors but
406 * they are not on hot paths so a little discipline won't do
407 * any harm.
408 *
409 * Locking: takes termios_mutex
410 */
411
412static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
413{
414 mutex_lock(&tty->termios_mutex);
415 tty->termios->c_line = num;
416 mutex_unlock(&tty->termios_mutex);
417}
418
Alan Coxc65c9bc2009-06-11 12:50:12 +0100419/**
420 * tty_ldisc_open - open a line discipline
421 * @tty: tty we are opening the ldisc on
422 * @ld: discipline to open
423 *
424 * A helper opening method. Also a convenient debugging and check
425 * point.
Arnd Bergmannec79d602010-06-01 22:53:01 +0200426 *
427 * Locking: always called with BTM already held.
Alan Coxc65c9bc2009-06-11 12:50:12 +0100428 */
429
430static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
431{
432 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
Alan Coxf18f9492009-11-30 13:18:35 +0000433 if (ld->ops->open) {
434 int ret;
Arnd Bergmannec79d602010-06-01 22:53:01 +0200435 /* BTM here locks versus a hangup event */
Alan Coxf18f9492009-11-30 13:18:35 +0000436 ret = ld->ops->open(tty);
Jiri Slaby7f90cfc2010-11-25 00:27:54 +0100437 if (ret)
438 clear_bit(TTY_LDISC_OPEN, &tty->flags);
Alan Coxf18f9492009-11-30 13:18:35 +0000439 return ret;
440 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100441 return 0;
442}
443
444/**
445 * tty_ldisc_close - close a line discipline
446 * @tty: tty we are opening the ldisc on
447 * @ld: discipline to close
448 *
449 * A helper close method. Also a convenient debugging and check
450 * point.
451 */
452
453static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
454{
455 WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
456 clear_bit(TTY_LDISC_OPEN, &tty->flags);
457 if (ld->ops->close)
458 ld->ops->close(tty);
459}
Alan Cox01e1abb2008-07-22 11:16:55 +0100460
461/**
462 * tty_ldisc_restore - helper for tty ldisc change
463 * @tty: tty to recover
464 * @old: previous ldisc
465 *
466 * Restore the previous line discipline or N_TTY when a line discipline
467 * change fails due to an open error
468 */
469
470static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
471{
472 char buf[64];
Alan Coxc65c9bc2009-06-11 12:50:12 +0100473 struct tty_ldisc *new_ldisc;
474 int r;
Alan Cox01e1abb2008-07-22 11:16:55 +0100475
476 /* There is an outstanding reference here so this is safe */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100477 old = tty_ldisc_get(old->ops->num);
478 WARN_ON(IS_ERR(old));
Alan Cox01e1abb2008-07-22 11:16:55 +0100479 tty_ldisc_assign(tty, old);
480 tty_set_termios_ldisc(tty, old->ops->num);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100481 if (tty_ldisc_open(tty, old) < 0) {
482 tty_ldisc_put(old);
Alan Cox01e1abb2008-07-22 11:16:55 +0100483 /* This driver is always present */
Alan Cox852e99d2009-06-11 12:51:41 +0100484 new_ldisc = tty_ldisc_get(N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100485 if (IS_ERR(new_ldisc))
Alan Cox01e1abb2008-07-22 11:16:55 +0100486 panic("n_tty: get");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100487 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100488 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100489 r = tty_ldisc_open(tty, new_ldisc);
490 if (r < 0)
491 panic("Couldn't open N_TTY ldisc for "
492 "%s --- error %d.",
493 tty_name(tty, buf), r);
Alan Cox01e1abb2008-07-22 11:16:55 +0100494 }
495}
496
497/**
Alan Coxc65c9bc2009-06-11 12:50:12 +0100498 * tty_ldisc_halt - shut down the line discipline
Alan Coxe8b70e72009-06-11 12:48:02 +0100499 * @tty: tty device
500 *
501 * Shut down the line discipline and work queue for this tty device.
502 * The TTY_LDISC flag being cleared ensures no further references can
503 * be obtained while the delayed work queue halt ensures that no more
504 * data is fed to the ldisc.
505 *
Linus Torvalds5c58cef2009-08-25 09:12:43 -0700506 * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
507 * in order to make sure any currently executing ldisc work is also
508 * flushed.
Alan Coxe8b70e72009-06-11 12:48:02 +0100509 */
510
Alan Coxc65c9bc2009-06-11 12:50:12 +0100511static int tty_ldisc_halt(struct tty_struct *tty)
Alan Coxe8b70e72009-06-11 12:48:02 +0100512{
513 clear_bit(TTY_LDISC, &tty->flags);
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700514 return cancel_work_sync(&tty->buf.work);
Alan Coxe8b70e72009-06-11 12:48:02 +0100515}
516
517/**
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100518 * tty_ldisc_flush_works - flush all works of a tty
519 * @tty: tty device to flush works for
520 *
521 * Sync flush all works belonging to @tty.
522 */
523static void tty_ldisc_flush_works(struct tty_struct *tty)
524{
525 flush_work_sync(&tty->hangup_work);
526 flush_work_sync(&tty->SAK_work);
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700527 flush_work_sync(&tty->buf.work);
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100528}
529
530/**
Jiri Slaby100eeae2010-10-31 23:17:51 +0100531 * tty_ldisc_wait_idle - wait for the ldisc to become idle
532 * @tty: tty to wait for
Jiri Slabydf92d052011-11-16 16:27:07 +0100533 * @timeout: for how long to wait at most
Jiri Slaby100eeae2010-10-31 23:17:51 +0100534 *
535 * Wait for the line discipline to become idle. The discipline must
536 * have been halted for this to guarantee it remains idle.
537 */
Jiri Slabydf92d052011-11-16 16:27:07 +0100538static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
Jiri Slaby100eeae2010-10-31 23:17:51 +0100539{
Jiri Slabydf92d052011-11-16 16:27:07 +0100540 long ret;
Jiri Slaby92f6fa02011-06-05 14:16:16 +0200541 ret = wait_event_timeout(tty_ldisc_idle,
Jiri Slabydf92d052011-11-16 16:27:07 +0100542 atomic_read(&tty->ldisc->users) == 1, timeout);
Jiri Slaby100eeae2010-10-31 23:17:51 +0100543 return ret > 0 ? 0 : -EBUSY;
544}
545
546/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100547 * tty_set_ldisc - set line discipline
548 * @tty: the terminal to set
549 * @ldisc: the line discipline
550 *
551 * Set the discipline of a tty line. Must be called from a process
Alan Coxc65c9bc2009-06-11 12:50:12 +0100552 * context. The ldisc change logic has to protect itself against any
553 * overlapping ldisc change (including on the other end of pty pairs),
554 * the close of one side of a tty/pty pair, and eventually hangup.
Alan Cox01e1abb2008-07-22 11:16:55 +0100555 *
Alan Coxc65c9bc2009-06-11 12:50:12 +0100556 * Locking: takes tty_ldisc_lock, termios_mutex
Alan Cox01e1abb2008-07-22 11:16:55 +0100557 */
558
559int tty_set_ldisc(struct tty_struct *tty, int ldisc)
560{
561 int retval;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100562 struct tty_ldisc *o_ldisc, *new_ldisc;
563 int work, o_work = 0;
Alan Cox01e1abb2008-07-22 11:16:55 +0100564 struct tty_struct *o_tty;
565
Alan Coxc65c9bc2009-06-11 12:50:12 +0100566 new_ldisc = tty_ldisc_get(ldisc);
567 if (IS_ERR(new_ldisc))
568 return PTR_ERR(new_ldisc);
569
Arnd Bergmannec79d602010-06-01 22:53:01 +0200570 tty_lock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100571 /*
572 * We need to look at the tty locking here for pty/tty pairs
573 * when both sides try to change in parallel.
574 */
575
576 o_tty = tty->link; /* o_tty is the pty side or NULL */
577
578
579 /*
580 * Check the no-op case
581 */
582
583 if (tty->ldisc->ops->num == ldisc) {
Arnd Bergmannec79d602010-06-01 22:53:01 +0200584 tty_unlock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100585 tty_ldisc_put(new_ldisc);
586 return 0;
587 }
Alan Cox01e1abb2008-07-22 11:16:55 +0100588
Arnd Bergmannec79d602010-06-01 22:53:01 +0200589 tty_unlock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100590 /*
591 * Problem: What do we do if this blocks ?
Alan Coxc65c9bc2009-06-11 12:50:12 +0100592 * We could deadlock here
Alan Cox01e1abb2008-07-22 11:16:55 +0100593 */
594
595 tty_wait_until_sent(tty, 0);
596
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200597 tty_lock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100598 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100599
600 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100601 * We could be midstream of another ldisc change which has
602 * dropped the lock during processing. If so we need to wait.
603 */
604
605 while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
606 mutex_unlock(&tty->ldisc_mutex);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200607 tty_unlock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100608 wait_event(tty_ldisc_wait,
609 test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200610 tty_lock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100611 mutex_lock(&tty->ldisc_mutex);
612 }
Alan Coxeeb89d92009-11-30 13:18:29 +0000613
Alan Coxc65c9bc2009-06-11 12:50:12 +0100614 set_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox852e99d2009-06-11 12:51:41 +0100615
Alan Coxc65c9bc2009-06-11 12:50:12 +0100616 /*
Alan Cox01e1abb2008-07-22 11:16:55 +0100617 * No more input please, we are switching. The new ldisc
618 * will update this value in the ldisc open function
619 */
620
621 tty->receive_room = 0;
622
623 o_ldisc = tty->ldisc;
Alan Coxeeb89d92009-11-30 13:18:29 +0000624
Arnd Bergmannec79d602010-06-01 22:53:01 +0200625 tty_unlock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100626 /*
627 * Make sure we don't change while someone holds a
628 * reference to the line discipline. The TTY_LDISC bit
629 * prevents anyone taking a reference once it is clear.
630 * We need the lock to avoid racing reference takers.
Alan Coxc9b39762009-01-02 13:44:56 +0000631 *
632 * We must clear the TTY_LDISC bit here to avoid a livelock
633 * with a userspace app continually trying to use the tty in
634 * parallel to the change and re-referencing the tty.
Alan Cox01e1abb2008-07-22 11:16:55 +0100635 */
636
Alan Coxc65c9bc2009-06-11 12:50:12 +0100637 work = tty_ldisc_halt(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100638 if (o_tty)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100639 o_work = tty_ldisc_halt(o_tty);
640
Alan Cox01e1abb2008-07-22 11:16:55 +0100641 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100642 * Wait for ->hangup_work and ->buf.work handlers to terminate.
643 * We must drop the mutex here in case a hangup is also in process.
Alan Cox01e1abb2008-07-22 11:16:55 +0100644 */
645
Alan Coxc65c9bc2009-06-11 12:50:12 +0100646 mutex_unlock(&tty->ldisc_mutex);
647
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100648 tty_ldisc_flush_works(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100649
Jiri Slabydf92d052011-11-16 16:27:07 +0100650 retval = tty_ldisc_wait_idle(tty, 5 * HZ);
Jiri Slaby100eeae2010-10-31 23:17:51 +0100651
Arnd Bergmannec79d602010-06-01 22:53:01 +0200652 tty_lock();
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200653 mutex_lock(&tty->ldisc_mutex);
Jiri Slaby100eeae2010-10-31 23:17:51 +0100654
655 /* handle wait idle failure locked */
656 if (retval) {
657 tty_ldisc_put(new_ldisc);
658 goto enable;
659 }
660
Alan Coxc65c9bc2009-06-11 12:50:12 +0100661 if (test_bit(TTY_HUPPED, &tty->flags)) {
662 /* We were raced by the hangup method. It will have stomped
663 the ldisc data and closed the ldisc down */
664 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
665 mutex_unlock(&tty->ldisc_mutex);
666 tty_ldisc_put(new_ldisc);
Arnd Bergmannec79d602010-06-01 22:53:01 +0200667 tty_unlock();
Alan Coxc65c9bc2009-06-11 12:50:12 +0100668 return -EIO;
669 }
670
Alan Cox01e1abb2008-07-22 11:16:55 +0100671 /* Shutdown the current discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100672 tty_ldisc_close(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100673
674 /* Now set up the new line discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100675 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100676 tty_set_termios_ldisc(tty, ldisc);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100677
678 retval = tty_ldisc_open(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100679 if (retval < 0) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100680 /* Back to the old one or N_TTY if we can't */
681 tty_ldisc_put(new_ldisc);
682 tty_ldisc_restore(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100683 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100684
Alan Cox01e1abb2008-07-22 11:16:55 +0100685 /* At this point we hold a reference to the new ldisc and a
686 a reference to the old ldisc. If we ended up flipping back
687 to the existing ldisc we have two references to it */
688
Alan Coxc65c9bc2009-06-11 12:50:12 +0100689 if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100690 tty->ops->set_ldisc(tty);
691
Alan Coxc65c9bc2009-06-11 12:50:12 +0100692 tty_ldisc_put(o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100693
Jiri Slaby100eeae2010-10-31 23:17:51 +0100694enable:
Alan Cox01e1abb2008-07-22 11:16:55 +0100695 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100696 * Allow ldisc referencing to occur again
Alan Cox01e1abb2008-07-22 11:16:55 +0100697 */
698
699 tty_ldisc_enable(tty);
700 if (o_tty)
701 tty_ldisc_enable(o_tty);
702
Alan Coxc65c9bc2009-06-11 12:50:12 +0100703 /* Restart the work queue in case no characters kick it off. Safe if
Alan Cox01e1abb2008-07-22 11:16:55 +0100704 already running */
705 if (work)
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700706 schedule_work(&tty->buf.work);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100707 if (o_work)
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700708 schedule_work(&o_tty->buf.work);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100709 mutex_unlock(&tty->ldisc_mutex);
Arnd Bergmannec79d602010-06-01 22:53:01 +0200710 tty_unlock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100711 return retval;
712}
713
Alan Coxc65c9bc2009-06-11 12:50:12 +0100714/**
715 * tty_reset_termios - reset terminal state
716 * @tty: tty to reset
717 *
718 * Restore a terminal to the driver default state.
719 */
720
721static void tty_reset_termios(struct tty_struct *tty)
722{
723 mutex_lock(&tty->termios_mutex);
724 *tty->termios = tty->driver->init_termios;
725 tty->termios->c_ispeed = tty_termios_input_baud_rate(tty->termios);
726 tty->termios->c_ospeed = tty_termios_baud_rate(tty->termios);
727 mutex_unlock(&tty->termios_mutex);
728}
729
730
731/**
732 * tty_ldisc_reinit - reinitialise the tty ldisc
733 * @tty: tty to reinit
Alan Cox638b9642010-02-08 10:09:26 +0000734 * @ldisc: line discipline to reinitialize
Alan Coxc65c9bc2009-06-11 12:50:12 +0100735 *
Alan Cox638b9642010-02-08 10:09:26 +0000736 * Switch the tty to a line discipline and leave the ldisc
737 * state closed
Alan Coxc65c9bc2009-06-11 12:50:12 +0100738 */
739
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200740static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100741{
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200742 struct tty_ldisc *ld = tty_ldisc_get(ldisc);
743
744 if (IS_ERR(ld))
745 return -1;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100746
747 tty_ldisc_close(tty, tty->ldisc);
748 tty_ldisc_put(tty->ldisc);
749 tty->ldisc = NULL;
750 /*
751 * Switch the line discipline back
752 */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100753 tty_ldisc_assign(tty, ld);
Alan Cox638b9642010-02-08 10:09:26 +0000754 tty_set_termios_ldisc(tty, ldisc);
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200755
756 return 0;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100757}
758
759/**
760 * tty_ldisc_hangup - hangup ldisc reset
761 * @tty: tty being hung up
762 *
763 * Some tty devices reset their termios when they receive a hangup
764 * event. In that situation we must also switch back to N_TTY properly
765 * before we reset the termios data.
766 *
767 * Locking: We can take the ldisc mutex as the rest of the code is
768 * careful to allow for this.
769 *
770 * In the pty pair case this occurs in the close() path of the
771 * tty itself so we must be careful about locking rules.
772 */
773
774void tty_ldisc_hangup(struct tty_struct *tty)
775{
776 struct tty_ldisc *ld;
Alan Cox638b9642010-02-08 10:09:26 +0000777 int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
778 int err = 0;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100779
780 /*
781 * FIXME! What are the locking issues here? This may me overdoing
782 * things... This question is especially important now that we've
783 * removed the irqlock.
784 */
785 ld = tty_ldisc_ref(tty);
786 if (ld != NULL) {
787 /* We may have no line discipline at this point */
788 if (ld->ops->flush_buffer)
789 ld->ops->flush_buffer(tty);
790 tty_driver_flush_buffer(tty);
791 if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
792 ld->ops->write_wakeup)
793 ld->ops->write_wakeup(tty);
794 if (ld->ops->hangup)
795 ld->ops->hangup(tty);
796 tty_ldisc_deref(ld);
797 }
798 /*
799 * FIXME: Once we trust the LDISC code better we can wait here for
800 * ldisc completion and fix the driver call race
801 */
802 wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
803 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
804 /*
805 * Shutdown the current line discipline, and reset it to
Alan Cox638b9642010-02-08 10:09:26 +0000806 * N_TTY if need be.
807 *
808 * Avoid racing set_ldisc or tty_ldisc_release
Alan Coxc65c9bc2009-06-11 12:50:12 +0100809 */
Alan Cox638b9642010-02-08 10:09:26 +0000810 mutex_lock(&tty->ldisc_mutex);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200811
812 /*
813 * this is like tty_ldisc_halt, but we need to give up
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700814 * the BTM before calling cancel_work_sync, which may
815 * need to wait for another function taking the BTM
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200816 */
817 clear_bit(TTY_LDISC, &tty->flags);
818 tty_unlock();
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700819 cancel_work_sync(&tty->buf.work);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200820 mutex_unlock(&tty->ldisc_mutex);
Jiri Slaby0c73c082011-11-16 16:27:09 +0100821retry:
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200822 tty_lock();
823 mutex_lock(&tty->ldisc_mutex);
824
Alan Cox638b9642010-02-08 10:09:26 +0000825 /* At this point we have a closed ldisc and we want to
826 reopen it. We could defer this to the next open but
827 it means auditing a lot of other paths so this is
828 a FIXME */
829 if (tty->ldisc) { /* Not yet closed */
Jiri Slaby0c73c082011-11-16 16:27:09 +0100830 if (atomic_read(&tty->ldisc->users) != 1) {
831 char cur_n[TASK_COMM_LEN], tty_n[64];
832 long timeout = 3 * HZ;
833 tty_unlock();
834
835 while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
836 timeout = MAX_SCHEDULE_TIMEOUT;
837 printk_ratelimited(KERN_WARNING
838 "%s: waiting (%s) for %s took too long, but we keep waiting...\n",
839 __func__, get_task_comm(cur_n, current),
840 tty_name(tty, tty_n));
841 }
842 mutex_unlock(&tty->ldisc_mutex);
843 goto retry;
844 }
Jiri Slaby30042072011-11-16 16:27:08 +0100845
Alan Cox638b9642010-02-08 10:09:26 +0000846 if (reset == 0) {
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200847
848 if (!tty_ldisc_reinit(tty, tty->termios->c_line))
849 err = tty_ldisc_open(tty, tty->ldisc);
850 else
851 err = 1;
Alan Coxc8d50042009-07-16 16:05:08 +0100852 }
Alan Cox638b9642010-02-08 10:09:26 +0000853 /* If the re-open fails or we reset then go to N_TTY. The
854 N_TTY open cannot fail */
855 if (reset || err) {
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200856 BUG_ON(tty_ldisc_reinit(tty, N_TTY));
Alan Cox638b9642010-02-08 10:09:26 +0000857 WARN_ON(tty_ldisc_open(tty, tty->ldisc));
858 }
859 tty_ldisc_enable(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100860 }
Alan Cox638b9642010-02-08 10:09:26 +0000861 mutex_unlock(&tty->ldisc_mutex);
862 if (reset)
863 tty_reset_termios(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100864}
Alan Cox01e1abb2008-07-22 11:16:55 +0100865
866/**
867 * tty_ldisc_setup - open line discipline
868 * @tty: tty being shut down
869 * @o_tty: pair tty for pty/tty pairs
870 *
871 * Called during the initial open of a tty/pty pair in order to set up the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100872 * line disciplines and bind them to the tty. This has no locking issues
873 * as the device isn't yet active.
Alan Cox01e1abb2008-07-22 11:16:55 +0100874 */
875
876int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
877{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100878 struct tty_ldisc *ld = tty->ldisc;
Alan Cox01e1abb2008-07-22 11:16:55 +0100879 int retval;
880
Alan Coxc65c9bc2009-06-11 12:50:12 +0100881 retval = tty_ldisc_open(tty, ld);
882 if (retval)
883 return retval;
884
885 if (o_tty) {
886 retval = tty_ldisc_open(o_tty, o_tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100887 if (retval) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100888 tty_ldisc_close(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100889 return retval;
890 }
891 tty_ldisc_enable(o_tty);
892 }
893 tty_ldisc_enable(tty);
894 return 0;
895}
Alan Cox01e1abb2008-07-22 11:16:55 +0100896/**
897 * tty_ldisc_release - release line discipline
898 * @tty: tty being shut down
899 * @o_tty: pair tty for pty/tty pairs
900 *
Alan Cox852e99d2009-06-11 12:51:41 +0100901 * Called during the final close of a tty/pty pair in order to shut down
902 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100903 * ldisc has not been opened.
Alan Cox01e1abb2008-07-22 11:16:55 +0100904 */
905
906void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
907{
Alan Cox01e1abb2008-07-22 11:16:55 +0100908 /*
909 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
910 * kill any delayed work. As this is the final close it does not
911 * race with the set_ldisc code path.
912 */
Alan Cox01e1abb2008-07-22 11:16:55 +0100913
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200914 tty_unlock();
Alan Coxe8b70e72009-06-11 12:48:02 +0100915 tty_ldisc_halt(tty);
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100916 tty_ldisc_flush_works(tty);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200917 tty_lock();
Alan Cox01e1abb2008-07-22 11:16:55 +0100918
Alan Coxc8d50042009-07-16 16:05:08 +0100919 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100920 /*
Alan Coxaef29bc2009-06-29 15:21:47 +0100921 * Now kill off the ldisc
Alan Cox01e1abb2008-07-22 11:16:55 +0100922 */
Alan Coxaef29bc2009-06-29 15:21:47 +0100923 tty_ldisc_close(tty, tty->ldisc);
924 tty_ldisc_put(tty->ldisc);
925 /* Force an oops if we mess this up */
926 tty->ldisc = NULL;
Alan Cox01e1abb2008-07-22 11:16:55 +0100927
Alan Coxaef29bc2009-06-29 15:21:47 +0100928 /* Ensure the next open requests the N_TTY ldisc */
929 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc8d50042009-07-16 16:05:08 +0100930 mutex_unlock(&tty->ldisc_mutex);
Alan Coxaef29bc2009-06-29 15:21:47 +0100931
Alan Coxc65c9bc2009-06-11 12:50:12 +0100932 /* This will need doing differently if we need to lock */
933 if (o_tty)
934 tty_ldisc_release(o_tty, NULL);
Alan Coxaef29bc2009-06-29 15:21:47 +0100935
936 /* And the memory resources remaining (buffers, termios) will be
937 disposed of when the kref hits zero */
Alan Cox01e1abb2008-07-22 11:16:55 +0100938}
939
940/**
941 * tty_ldisc_init - ldisc setup for new tty
942 * @tty: tty being allocated
943 *
944 * Set up the line discipline objects for a newly allocated tty. Note that
945 * the tty structure is not completely set up when this call is made.
946 */
947
948void tty_ldisc_init(struct tty_struct *tty)
949{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100950 struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
951 if (IS_ERR(ld))
Alan Cox01e1abb2008-07-22 11:16:55 +0100952 panic("n_tty: init_tty");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100953 tty_ldisc_assign(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100954}
955
Jiri Slaby67166712011-03-23 10:48:35 +0100956/**
957 * tty_ldisc_init - ldisc cleanup for new tty
958 * @tty: tty that was allocated recently
959 *
960 * The tty structure must not becompletely set up (tty_ldisc_setup) when
961 * this call is made.
962 */
963void tty_ldisc_deinit(struct tty_struct *tty)
964{
965 put_ldisc(tty->ldisc);
966 tty_ldisc_assign(tty, NULL);
967}
968
Alan Cox01e1abb2008-07-22 11:16:55 +0100969void tty_ldisc_begin(void)
970{
971 /* Setup the default TTY line discipline. */
972 (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
973}