blob: c5782294e53261e701f13292b5732c231cfb9d14 [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
Ivo Siebenc9739942012-10-17 14:03:14 +020029static DEFINE_RAW_SPINLOCK(tty_ldisc_lock);
Alan Cox01e1abb2008-07-22 11:16:55 +010030static DECLARE_WAIT_QUEUE_HEAD(tty_ldisc_wait);
31/* Line disc dispatch table */
32static struct tty_ldisc_ops *tty_ldiscs[NR_LDISCS];
33
Linus Torvalds65b77042009-08-03 11:11:19 -070034static inline struct tty_ldisc *get_ldisc(struct tty_ldisc *ld)
35{
36 if (ld)
37 atomic_inc(&ld->users);
38 return ld;
39}
40
Linus Torvaldscbe93522009-08-03 14:54:56 -070041static void put_ldisc(struct tty_ldisc *ld)
Linus Torvalds65b77042009-08-03 11:11:19 -070042{
Linus Torvaldscbe93522009-08-03 14:54:56 -070043 unsigned long flags;
44
Linus Torvalds65b77042009-08-03 11:11:19 -070045 if (WARN_ON_ONCE(!ld))
46 return;
47
48 /*
49 * If this is the last user, free the ldisc, and
50 * release the ldisc ops.
Linus Torvaldscbe93522009-08-03 14:54:56 -070051 *
Ivo Siebenc9739942012-10-17 14:03:14 +020052 * We really want an "atomic_dec_and_raw_lock_irqsave()",
Linus Torvaldscbe93522009-08-03 14:54:56 -070053 * but we don't have it, so this does it by hand.
Linus Torvalds65b77042009-08-03 11:11:19 -070054 */
Ivo Siebenc9739942012-10-17 14:03:14 +020055 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
56 if (atomic_dec_and_test(&ld->users)) {
Linus Torvalds65b77042009-08-03 11:11:19 -070057 struct tty_ldisc_ops *ldo = ld->ops;
58
Linus Torvalds65b77042009-08-03 11:11:19 -070059 ldo->refcount--;
60 module_put(ldo->owner);
Ivo Siebenc9739942012-10-17 14:03:14 +020061 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvaldscbe93522009-08-03 14:54:56 -070062
63 kfree(ld);
64 return;
Linus Torvalds65b77042009-08-03 11:11:19 -070065 }
Ivo Siebenc9739942012-10-17 14:03:14 +020066 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Ivo Sieben1541f842012-05-03 14:37:43 +020067 wake_up(&ld->wq_idle);
Linus Torvalds65b77042009-08-03 11:11:19 -070068}
69
Alan Cox01e1abb2008-07-22 11:16:55 +010070/**
71 * tty_register_ldisc - install a line discipline
72 * @disc: ldisc number
73 * @new_ldisc: pointer to the ldisc object
74 *
75 * Installs a new line discipline into the kernel. The discipline
76 * is set up as unreferenced and then made available to the kernel
77 * from this point onwards.
78 *
79 * Locking:
80 * takes tty_ldisc_lock to guard against ldisc races
81 */
82
83int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
84{
85 unsigned long flags;
86 int ret = 0;
87
88 if (disc < N_TTY || disc >= NR_LDISCS)
89 return -EINVAL;
90
Ivo Siebenc9739942012-10-17 14:03:14 +020091 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Alan Cox01e1abb2008-07-22 11:16:55 +010092 tty_ldiscs[disc] = new_ldisc;
93 new_ldisc->num = disc;
94 new_ldisc->refcount = 0;
Ivo Siebenc9739942012-10-17 14:03:14 +020095 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Alan Cox01e1abb2008-07-22 11:16:55 +010096
97 return ret;
98}
99EXPORT_SYMBOL(tty_register_ldisc);
100
101/**
102 * tty_unregister_ldisc - unload a line discipline
103 * @disc: ldisc number
104 * @new_ldisc: pointer to the ldisc object
105 *
106 * Remove a line discipline from the kernel providing it is not
107 * currently in use.
108 *
109 * Locking:
110 * takes tty_ldisc_lock to guard against ldisc races
111 */
112
113int tty_unregister_ldisc(int disc)
114{
115 unsigned long flags;
116 int ret = 0;
117
118 if (disc < N_TTY || disc >= NR_LDISCS)
119 return -EINVAL;
120
Ivo Siebenc9739942012-10-17 14:03:14 +0200121 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100122 if (tty_ldiscs[disc]->refcount)
123 ret = -EBUSY;
124 else
125 tty_ldiscs[disc] = NULL;
Ivo Siebenc9739942012-10-17 14:03:14 +0200126 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100127
128 return ret;
129}
130EXPORT_SYMBOL(tty_unregister_ldisc);
131
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700132static struct tty_ldisc_ops *get_ldops(int disc)
133{
134 unsigned long flags;
135 struct tty_ldisc_ops *ldops, *ret;
136
Ivo Siebenc9739942012-10-17 14:03:14 +0200137 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700138 ret = ERR_PTR(-EINVAL);
139 ldops = tty_ldiscs[disc];
140 if (ldops) {
141 ret = ERR_PTR(-EAGAIN);
142 if (try_module_get(ldops->owner)) {
143 ldops->refcount++;
144 ret = ldops;
145 }
146 }
Ivo Siebenc9739942012-10-17 14:03:14 +0200147 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700148 return ret;
149}
150
151static void put_ldops(struct tty_ldisc_ops *ldops)
152{
153 unsigned long flags;
154
Ivo Siebenc9739942012-10-17 14:03:14 +0200155 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700156 ldops->refcount--;
157 module_put(ldops->owner);
Ivo Siebenc9739942012-10-17 14:03:14 +0200158 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700159}
Alan Cox01e1abb2008-07-22 11:16:55 +0100160
161/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100162 * tty_ldisc_get - take a reference to an ldisc
163 * @disc: ldisc number
Alan Cox01e1abb2008-07-22 11:16:55 +0100164 *
165 * Takes a reference to a line discipline. Deals with refcounts and
166 * module locking counts. Returns NULL if the discipline is not available.
167 * Returns a pointer to the discipline and bumps the ref count if it is
168 * available
169 *
170 * Locking:
171 * takes tty_ldisc_lock to guard against ldisc races
172 */
173
Alan Coxc65c9bc2009-06-11 12:50:12 +0100174static struct tty_ldisc *tty_ldisc_get(int disc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100175{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100176 struct tty_ldisc *ld;
Linus Torvalds182274f2009-08-03 16:01:28 -0700177 struct tty_ldisc_ops *ldops;
Alan Cox01e1abb2008-07-22 11:16:55 +0100178
179 if (disc < N_TTY || disc >= NR_LDISCS)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100180 return ERR_PTR(-EINVAL);
Linus Torvalds182274f2009-08-03 16:01:28 -0700181
182 /*
183 * Get the ldisc ops - we may need to request them to be loaded
184 * dynamically and try again.
185 */
186 ldops = get_ldops(disc);
187 if (IS_ERR(ldops)) {
Alan Cox01e1abb2008-07-22 11:16:55 +0100188 request_module("tty-ldisc-%d", disc);
Linus Torvalds182274f2009-08-03 16:01:28 -0700189 ldops = get_ldops(disc);
190 if (IS_ERR(ldops))
191 return ERR_CAST(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100192 }
Linus Torvalds182274f2009-08-03 16:01:28 -0700193
194 ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
195 if (ld == NULL) {
196 put_ldops(ldops);
197 return ERR_PTR(-ENOMEM);
198 }
199
200 ld->ops = ldops;
201 atomic_set(&ld->users, 1);
Ivo Sieben1541f842012-05-03 14:37:43 +0200202 init_waitqueue_head(&ld->wq_idle);
203
Alan Coxc65c9bc2009-06-11 12:50:12 +0100204 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100205}
206
Alan Cox852e99d2009-06-11 12:51:41 +0100207static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100208{
209 return (*pos < NR_LDISCS) ? pos : NULL;
210}
211
Alan Cox852e99d2009-06-11 12:51:41 +0100212static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100213{
214 (*pos)++;
215 return (*pos < NR_LDISCS) ? pos : NULL;
216}
217
218static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
219{
220}
221
222static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
223{
224 int i = *(loff_t *)v;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700225 struct tty_ldisc_ops *ldops;
Alan Cox852e99d2009-06-11 12:51:41 +0100226
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700227 ldops = get_ldops(i);
228 if (IS_ERR(ldops))
Alan Cox01e1abb2008-07-22 11:16:55 +0100229 return 0;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700230 seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
231 put_ldops(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100232 return 0;
233}
234
235static const struct seq_operations tty_ldiscs_seq_ops = {
236 .start = tty_ldiscs_seq_start,
237 .next = tty_ldiscs_seq_next,
238 .stop = tty_ldiscs_seq_stop,
239 .show = tty_ldiscs_seq_show,
240};
241
242static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
243{
244 return seq_open(file, &tty_ldiscs_seq_ops);
245}
246
247const struct file_operations tty_ldiscs_proc_fops = {
248 .owner = THIS_MODULE,
249 .open = proc_tty_ldiscs_open,
250 .read = seq_read,
251 .llseek = seq_lseek,
252 .release = seq_release,
253};
254
255/**
256 * tty_ldisc_assign - set ldisc on a tty
257 * @tty: tty to assign
258 * @ld: line discipline
259 *
260 * Install an instance of a line discipline into a tty structure. The
Alan Cox8d2ead72009-06-16 17:00:26 +0100261 * ldisc must have a reference count above zero to ensure it remains.
Alan Cox01e1abb2008-07-22 11:16:55 +0100262 * The tty instance refcount starts at zero.
263 *
264 * Locking:
265 * Caller must hold references
266 */
267
268static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
269{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100270 tty->ldisc = ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100271}
272
273/**
274 * tty_ldisc_try - internal helper
275 * @tty: the tty
276 *
277 * Make a single attempt to grab and bump the refcount on
278 * the tty ldisc. Return 0 on failure or 1 on success. This is
279 * used to implement both the waiting and non waiting versions
280 * of tty_ldisc_ref
281 *
282 * Locking: takes tty_ldisc_lock
283 */
284
Linus Torvalds65b77042009-08-03 11:11:19 -0700285static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
Alan Cox01e1abb2008-07-22 11:16:55 +0100286{
287 unsigned long flags;
288 struct tty_ldisc *ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100289
Ivo Siebenc9739942012-10-17 14:03:14 +0200290 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700291 ld = NULL;
292 if (test_bit(TTY_LDISC, &tty->flags))
293 ld = get_ldisc(tty->ldisc);
Ivo Siebenc9739942012-10-17 14:03:14 +0200294 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700295 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100296}
297
298/**
299 * tty_ldisc_ref_wait - wait for the tty ldisc
300 * @tty: tty device
301 *
302 * Dereference the line discipline for the terminal and take a
303 * reference to it. If the line discipline is in flux then
304 * wait patiently until it changes.
305 *
306 * Note: Must not be called from an IRQ/timer context. The caller
307 * must also be careful not to hold other locks that will deadlock
308 * against a discipline change, such as an existing ldisc reference
309 * (which we check for)
310 *
311 * Locking: call functions take tty_ldisc_lock
312 */
313
314struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
315{
Linus Torvalds65b77042009-08-03 11:11:19 -0700316 struct tty_ldisc *ld;
317
Alan Cox01e1abb2008-07-22 11:16:55 +0100318 /* wait_event is a macro */
Linus Torvalds65b77042009-08-03 11:11:19 -0700319 wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
320 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100321}
Alan Cox01e1abb2008-07-22 11:16:55 +0100322EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
323
324/**
325 * tty_ldisc_ref - get the tty ldisc
326 * @tty: tty device
327 *
328 * Dereference the line discipline for the terminal and take a
329 * reference to it. If the line discipline is in flux then
330 * return NULL. Can be called from IRQ and timer functions.
331 *
332 * Locking: called functions take tty_ldisc_lock
333 */
334
335struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
336{
Linus Torvalds65b77042009-08-03 11:11:19 -0700337 return tty_ldisc_try(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100338}
Alan Cox01e1abb2008-07-22 11:16:55 +0100339EXPORT_SYMBOL_GPL(tty_ldisc_ref);
340
341/**
342 * tty_ldisc_deref - free a tty ldisc reference
343 * @ld: reference to free up
344 *
345 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
346 * be called in IRQ context.
347 *
348 * Locking: takes tty_ldisc_lock
349 */
350
351void tty_ldisc_deref(struct tty_ldisc *ld)
352{
Linus Torvalds65b77042009-08-03 11:11:19 -0700353 put_ldisc(ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100354}
Alan Cox01e1abb2008-07-22 11:16:55 +0100355EXPORT_SYMBOL_GPL(tty_ldisc_deref);
356
Linus Torvalds65b77042009-08-03 11:11:19 -0700357static inline void tty_ldisc_put(struct tty_ldisc *ld)
358{
359 put_ldisc(ld);
360}
361
Alan Cox01e1abb2008-07-22 11:16:55 +0100362/**
363 * tty_ldisc_enable - allow ldisc use
364 * @tty: terminal to activate ldisc on
365 *
366 * Set the TTY_LDISC flag when the line discipline can be called
Alan Coxc9b39762009-01-02 13:44:56 +0000367 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
368 * changing flag to indicate any ldisc change is now over.
Alan Cox01e1abb2008-07-22 11:16:55 +0100369 *
Alan Coxc9b39762009-01-02 13:44:56 +0000370 * Note: nobody should set the TTY_LDISC bit except via this function.
371 * Clearing directly is allowed.
Alan Cox01e1abb2008-07-22 11:16:55 +0100372 */
373
374void tty_ldisc_enable(struct tty_struct *tty)
375{
376 set_bit(TTY_LDISC, &tty->flags);
Alan Coxc9b39762009-01-02 13:44:56 +0000377 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100378 wake_up(&tty_ldisc_wait);
379}
380
381/**
Alan Coxf2c4c652009-06-11 12:50:58 +0100382 * tty_ldisc_flush - flush line discipline queue
383 * @tty: tty
384 *
385 * Flush the line discipline queue (if any) for this tty. If there
386 * is no line discipline active this is a no-op.
387 */
388
389void tty_ldisc_flush(struct tty_struct *tty)
390{
391 struct tty_ldisc *ld = tty_ldisc_ref(tty);
392 if (ld) {
393 if (ld->ops->flush_buffer)
394 ld->ops->flush_buffer(tty);
395 tty_ldisc_deref(ld);
396 }
397 tty_buffer_flush(tty);
398}
Alan Coxf2c4c652009-06-11 12:50:58 +0100399EXPORT_SYMBOL_GPL(tty_ldisc_flush);
400
401/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100402 * tty_set_termios_ldisc - set ldisc field
403 * @tty: tty structure
404 * @num: line discipline number
405 *
406 * This is probably overkill for real world processors but
407 * they are not on hot paths so a little discipline won't do
408 * any harm.
409 *
410 * Locking: takes termios_mutex
411 */
412
413static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
414{
415 mutex_lock(&tty->termios_mutex);
Alan Coxadc8d742012-07-14 15:31:47 +0100416 tty->termios.c_line = num;
Alan Cox01e1abb2008-07-22 11:16:55 +0100417 mutex_unlock(&tty->termios_mutex);
418}
419
Alan Coxc65c9bc2009-06-11 12:50:12 +0100420/**
421 * tty_ldisc_open - open a line discipline
422 * @tty: tty we are opening the ldisc on
423 * @ld: discipline to open
424 *
425 * A helper opening method. Also a convenient debugging and check
426 * point.
Arnd Bergmannec79d602010-06-01 22:53:01 +0200427 *
428 * Locking: always called with BTM already held.
Alan Coxc65c9bc2009-06-11 12:50:12 +0100429 */
430
431static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
432{
433 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
Alan Coxf18f9492009-11-30 13:18:35 +0000434 if (ld->ops->open) {
435 int ret;
Arnd Bergmannec79d602010-06-01 22:53:01 +0200436 /* BTM here locks versus a hangup event */
Alan Coxf18f9492009-11-30 13:18:35 +0000437 ret = ld->ops->open(tty);
Jiri Slaby7f90cfc2010-11-25 00:27:54 +0100438 if (ret)
439 clear_bit(TTY_LDISC_OPEN, &tty->flags);
Alan Coxf18f9492009-11-30 13:18:35 +0000440 return ret;
441 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100442 return 0;
443}
444
445/**
446 * tty_ldisc_close - close a line discipline
447 * @tty: tty we are opening the ldisc on
448 * @ld: discipline to close
449 *
450 * A helper close method. Also a convenient debugging and check
451 * point.
452 */
453
454static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
455{
456 WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
457 clear_bit(TTY_LDISC_OPEN, &tty->flags);
458 if (ld->ops->close)
459 ld->ops->close(tty);
460}
Alan Cox01e1abb2008-07-22 11:16:55 +0100461
462/**
463 * tty_ldisc_restore - helper for tty ldisc change
464 * @tty: tty to recover
465 * @old: previous ldisc
466 *
467 * Restore the previous line discipline or N_TTY when a line discipline
468 * change fails due to an open error
469 */
470
471static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
472{
473 char buf[64];
Alan Coxc65c9bc2009-06-11 12:50:12 +0100474 struct tty_ldisc *new_ldisc;
475 int r;
Alan Cox01e1abb2008-07-22 11:16:55 +0100476
477 /* There is an outstanding reference here so this is safe */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100478 old = tty_ldisc_get(old->ops->num);
479 WARN_ON(IS_ERR(old));
Alan Cox01e1abb2008-07-22 11:16:55 +0100480 tty_ldisc_assign(tty, old);
481 tty_set_termios_ldisc(tty, old->ops->num);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100482 if (tty_ldisc_open(tty, old) < 0) {
483 tty_ldisc_put(old);
Alan Cox01e1abb2008-07-22 11:16:55 +0100484 /* This driver is always present */
Alan Cox852e99d2009-06-11 12:51:41 +0100485 new_ldisc = tty_ldisc_get(N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100486 if (IS_ERR(new_ldisc))
Alan Cox01e1abb2008-07-22 11:16:55 +0100487 panic("n_tty: get");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100488 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100489 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100490 r = tty_ldisc_open(tty, new_ldisc);
491 if (r < 0)
492 panic("Couldn't open N_TTY ldisc for "
493 "%s --- error %d.",
494 tty_name(tty, buf), r);
Alan Cox01e1abb2008-07-22 11:16:55 +0100495 }
496}
497
498/**
Alan Coxc65c9bc2009-06-11 12:50:12 +0100499 * tty_ldisc_halt - shut down the line discipline
Alan Coxe8b70e72009-06-11 12:48:02 +0100500 * @tty: tty device
501 *
502 * Shut down the line discipline and work queue for this tty device.
503 * The TTY_LDISC flag being cleared ensures no further references can
504 * be obtained while the delayed work queue halt ensures that no more
505 * data is fed to the ldisc.
506 *
Linus Torvalds5c58cef2009-08-25 09:12:43 -0700507 * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
508 * in order to make sure any currently executing ldisc work is also
509 * flushed.
Alan Coxe8b70e72009-06-11 12:48:02 +0100510 */
511
Alan Coxc65c9bc2009-06-11 12:50:12 +0100512static int tty_ldisc_halt(struct tty_struct *tty)
Alan Coxe8b70e72009-06-11 12:48:02 +0100513{
514 clear_bit(TTY_LDISC, &tty->flags);
Jiri Slabyecbbfd42012-10-18 22:26:47 +0200515 return cancel_work_sync(&tty->port->buf.work);
Alan Coxe8b70e72009-06-11 12:48:02 +0100516}
517
518/**
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100519 * tty_ldisc_flush_works - flush all works of a tty
520 * @tty: tty device to flush works for
521 *
522 * Sync flush all works belonging to @tty.
523 */
524static void tty_ldisc_flush_works(struct tty_struct *tty)
525{
Tejun Heo43829732012-08-20 14:51:24 -0700526 flush_work(&tty->hangup_work);
527 flush_work(&tty->SAK_work);
Jiri Slabyecbbfd42012-10-18 22:26:47 +0200528 flush_work(&tty->port->buf.work);
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100529}
530
531/**
Jiri Slaby100eeae2010-10-31 23:17:51 +0100532 * tty_ldisc_wait_idle - wait for the ldisc to become idle
533 * @tty: tty to wait for
Jiri Slabydf92d052011-11-16 16:27:07 +0100534 * @timeout: for how long to wait at most
Jiri Slaby100eeae2010-10-31 23:17:51 +0100535 *
536 * Wait for the line discipline to become idle. The discipline must
537 * have been halted for this to guarantee it remains idle.
538 */
Jiri Slabydf92d052011-11-16 16:27:07 +0100539static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
Jiri Slaby100eeae2010-10-31 23:17:51 +0100540{
Jiri Slabydf92d052011-11-16 16:27:07 +0100541 long ret;
Ivo Sieben1541f842012-05-03 14:37:43 +0200542 ret = wait_event_timeout(tty->ldisc->wq_idle,
Jiri Slabydf92d052011-11-16 16:27:07 +0100543 atomic_read(&tty->ldisc->users) == 1, timeout);
Jiri Slaby100eeae2010-10-31 23:17:51 +0100544 return ret > 0 ? 0 : -EBUSY;
545}
546
547/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100548 * tty_set_ldisc - set line discipline
549 * @tty: the terminal to set
550 * @ldisc: the line discipline
551 *
552 * Set the discipline of a tty line. Must be called from a process
Alan Coxc65c9bc2009-06-11 12:50:12 +0100553 * context. The ldisc change logic has to protect itself against any
554 * overlapping ldisc change (including on the other end of pty pairs),
555 * the close of one side of a tty/pty pair, and eventually hangup.
Alan Cox01e1abb2008-07-22 11:16:55 +0100556 *
Alan Coxc65c9bc2009-06-11 12:50:12 +0100557 * Locking: takes tty_ldisc_lock, termios_mutex
Alan Cox01e1abb2008-07-22 11:16:55 +0100558 */
559
560int tty_set_ldisc(struct tty_struct *tty, int ldisc)
561{
562 int retval;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100563 struct tty_ldisc *o_ldisc, *new_ldisc;
564 int work, o_work = 0;
Alan Cox01e1abb2008-07-22 11:16:55 +0100565 struct tty_struct *o_tty;
566
Alan Coxc65c9bc2009-06-11 12:50:12 +0100567 new_ldisc = tty_ldisc_get(ldisc);
568 if (IS_ERR(new_ldisc))
569 return PTR_ERR(new_ldisc);
570
Alan Cox89c8d912012-08-08 16:30:13 +0100571 tty_lock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100572 /*
573 * We need to look at the tty locking here for pty/tty pairs
574 * when both sides try to change in parallel.
575 */
576
577 o_tty = tty->link; /* o_tty is the pty side or NULL */
578
579
580 /*
581 * Check the no-op case
582 */
583
584 if (tty->ldisc->ops->num == ldisc) {
Alan Cox89c8d912012-08-08 16:30:13 +0100585 tty_unlock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100586 tty_ldisc_put(new_ldisc);
587 return 0;
588 }
Alan Cox01e1abb2008-07-22 11:16:55 +0100589
Alan Cox89c8d912012-08-08 16:30:13 +0100590 tty_unlock(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100591 /*
592 * Problem: What do we do if this blocks ?
Alan Coxc65c9bc2009-06-11 12:50:12 +0100593 * We could deadlock here
Alan Cox01e1abb2008-07-22 11:16:55 +0100594 */
595
596 tty_wait_until_sent(tty, 0);
597
Alan Cox89c8d912012-08-08 16:30:13 +0100598 tty_lock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100599 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100600
601 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100602 * We could be midstream of another ldisc change which has
603 * dropped the lock during processing. If so we need to wait.
604 */
605
606 while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
607 mutex_unlock(&tty->ldisc_mutex);
Alan Cox89c8d912012-08-08 16:30:13 +0100608 tty_unlock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100609 wait_event(tty_ldisc_wait,
610 test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
Alan Cox89c8d912012-08-08 16:30:13 +0100611 tty_lock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100612 mutex_lock(&tty->ldisc_mutex);
613 }
Alan Coxeeb89d92009-11-30 13:18:29 +0000614
Alan Coxc65c9bc2009-06-11 12:50:12 +0100615 set_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox852e99d2009-06-11 12:51:41 +0100616
Alan Coxc65c9bc2009-06-11 12:50:12 +0100617 /*
Alan Cox01e1abb2008-07-22 11:16:55 +0100618 * No more input please, we are switching. The new ldisc
619 * will update this value in the ldisc open function
620 */
621
622 tty->receive_room = 0;
623
624 o_ldisc = tty->ldisc;
Alan Coxeeb89d92009-11-30 13:18:29 +0000625
Alan Cox89c8d912012-08-08 16:30:13 +0100626 tty_unlock(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100627 /*
628 * Make sure we don't change while someone holds a
629 * reference to the line discipline. The TTY_LDISC bit
630 * prevents anyone taking a reference once it is clear.
631 * We need the lock to avoid racing reference takers.
Alan Coxc9b39762009-01-02 13:44:56 +0000632 *
633 * We must clear the TTY_LDISC bit here to avoid a livelock
634 * with a userspace app continually trying to use the tty in
635 * parallel to the change and re-referencing the tty.
Alan Cox01e1abb2008-07-22 11:16:55 +0100636 */
637
Alan Coxc65c9bc2009-06-11 12:50:12 +0100638 work = tty_ldisc_halt(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100639 if (o_tty)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100640 o_work = tty_ldisc_halt(o_tty);
641
Alan Cox01e1abb2008-07-22 11:16:55 +0100642 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100643 * Wait for ->hangup_work and ->buf.work handlers to terminate.
644 * We must drop the mutex here in case a hangup is also in process.
Alan Cox01e1abb2008-07-22 11:16:55 +0100645 */
646
Alan Coxc65c9bc2009-06-11 12:50:12 +0100647 mutex_unlock(&tty->ldisc_mutex);
648
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100649 tty_ldisc_flush_works(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100650
Jiri Slabydf92d052011-11-16 16:27:07 +0100651 retval = tty_ldisc_wait_idle(tty, 5 * HZ);
Jiri Slaby100eeae2010-10-31 23:17:51 +0100652
Alan Cox89c8d912012-08-08 16:30:13 +0100653 tty_lock(tty);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200654 mutex_lock(&tty->ldisc_mutex);
Jiri Slaby100eeae2010-10-31 23:17:51 +0100655
656 /* handle wait idle failure locked */
657 if (retval) {
658 tty_ldisc_put(new_ldisc);
659 goto enable;
660 }
661
Shachar Shemesh40c9f612012-07-10 07:54:13 +0300662 if (test_bit(TTY_HUPPING, &tty->flags)) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100663 /* We were raced by the hangup method. It will have stomped
664 the ldisc data and closed the ldisc down */
665 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
666 mutex_unlock(&tty->ldisc_mutex);
667 tty_ldisc_put(new_ldisc);
Alan Cox89c8d912012-08-08 16:30:13 +0100668 tty_unlock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100669 return -EIO;
670 }
671
Alan Cox01e1abb2008-07-22 11:16:55 +0100672 /* Shutdown the current discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100673 tty_ldisc_close(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100674
675 /* Now set up the new line discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100676 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100677 tty_set_termios_ldisc(tty, ldisc);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100678
679 retval = tty_ldisc_open(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100680 if (retval < 0) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100681 /* Back to the old one or N_TTY if we can't */
682 tty_ldisc_put(new_ldisc);
683 tty_ldisc_restore(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100684 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100685
Alan Cox01e1abb2008-07-22 11:16:55 +0100686 /* At this point we hold a reference to the new ldisc and a
687 a reference to the old ldisc. If we ended up flipping back
688 to the existing ldisc we have two references to it */
689
Alan Coxc65c9bc2009-06-11 12:50:12 +0100690 if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100691 tty->ops->set_ldisc(tty);
692
Alan Coxc65c9bc2009-06-11 12:50:12 +0100693 tty_ldisc_put(o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100694
Jiri Slaby100eeae2010-10-31 23:17:51 +0100695enable:
Alan Cox01e1abb2008-07-22 11:16:55 +0100696 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100697 * Allow ldisc referencing to occur again
Alan Cox01e1abb2008-07-22 11:16:55 +0100698 */
699
700 tty_ldisc_enable(tty);
701 if (o_tty)
702 tty_ldisc_enable(o_tty);
703
Alan Coxc65c9bc2009-06-11 12:50:12 +0100704 /* Restart the work queue in case no characters kick it off. Safe if
Alan Cox01e1abb2008-07-22 11:16:55 +0100705 already running */
706 if (work)
Jiri Slabyecbbfd42012-10-18 22:26:47 +0200707 schedule_work(&tty->port->buf.work);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100708 if (o_work)
Jiri Slabyecbbfd42012-10-18 22:26:47 +0200709 schedule_work(&o_tty->port->buf.work);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100710 mutex_unlock(&tty->ldisc_mutex);
Alan Cox89c8d912012-08-08 16:30:13 +0100711 tty_unlock(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100712 return retval;
713}
714
Alan Coxc65c9bc2009-06-11 12:50:12 +0100715/**
716 * tty_reset_termios - reset terminal state
717 * @tty: tty to reset
718 *
719 * Restore a terminal to the driver default state.
720 */
721
722static void tty_reset_termios(struct tty_struct *tty)
723{
724 mutex_lock(&tty->termios_mutex);
Alan Coxadc8d742012-07-14 15:31:47 +0100725 tty->termios = tty->driver->init_termios;
726 tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
727 tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100728 mutex_unlock(&tty->termios_mutex);
729}
730
731
732/**
733 * tty_ldisc_reinit - reinitialise the tty ldisc
734 * @tty: tty to reinit
Alan Cox638b9642010-02-08 10:09:26 +0000735 * @ldisc: line discipline to reinitialize
Alan Coxc65c9bc2009-06-11 12:50:12 +0100736 *
Alan Cox638b9642010-02-08 10:09:26 +0000737 * Switch the tty to a line discipline and leave the ldisc
738 * state closed
Alan Coxc65c9bc2009-06-11 12:50:12 +0100739 */
740
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200741static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100742{
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200743 struct tty_ldisc *ld = tty_ldisc_get(ldisc);
744
745 if (IS_ERR(ld))
746 return -1;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100747
748 tty_ldisc_close(tty, tty->ldisc);
749 tty_ldisc_put(tty->ldisc);
750 tty->ldisc = NULL;
751 /*
752 * Switch the line discipline back
753 */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100754 tty_ldisc_assign(tty, ld);
Alan Cox638b9642010-02-08 10:09:26 +0000755 tty_set_termios_ldisc(tty, ldisc);
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200756
757 return 0;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100758}
759
760/**
761 * tty_ldisc_hangup - hangup ldisc reset
762 * @tty: tty being hung up
763 *
764 * Some tty devices reset their termios when they receive a hangup
765 * event. In that situation we must also switch back to N_TTY properly
766 * before we reset the termios data.
767 *
768 * Locking: We can take the ldisc mutex as the rest of the code is
769 * careful to allow for this.
770 *
771 * In the pty pair case this occurs in the close() path of the
772 * tty itself so we must be careful about locking rules.
773 */
774
775void tty_ldisc_hangup(struct tty_struct *tty)
776{
777 struct tty_ldisc *ld;
Alan Cox638b9642010-02-08 10:09:26 +0000778 int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
779 int err = 0;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100780
781 /*
782 * FIXME! What are the locking issues here? This may me overdoing
783 * things... This question is especially important now that we've
784 * removed the irqlock.
785 */
786 ld = tty_ldisc_ref(tty);
787 if (ld != NULL) {
788 /* We may have no line discipline at this point */
789 if (ld->ops->flush_buffer)
790 ld->ops->flush_buffer(tty);
791 tty_driver_flush_buffer(tty);
792 if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
793 ld->ops->write_wakeup)
794 ld->ops->write_wakeup(tty);
795 if (ld->ops->hangup)
796 ld->ops->hangup(tty);
797 tty_ldisc_deref(ld);
798 }
799 /*
800 * FIXME: Once we trust the LDISC code better we can wait here for
801 * ldisc completion and fix the driver call race
802 */
803 wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
804 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
805 /*
806 * Shutdown the current line discipline, and reset it to
Alan Cox638b9642010-02-08 10:09:26 +0000807 * N_TTY if need be.
808 *
809 * Avoid racing set_ldisc or tty_ldisc_release
Alan Coxc65c9bc2009-06-11 12:50:12 +0100810 */
Alan Cox638b9642010-02-08 10:09:26 +0000811 mutex_lock(&tty->ldisc_mutex);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200812
813 /*
814 * this is like tty_ldisc_halt, but we need to give up
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700815 * the BTM before calling cancel_work_sync, which may
816 * need to wait for another function taking the BTM
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200817 */
818 clear_bit(TTY_LDISC, &tty->flags);
Alan Cox89c8d912012-08-08 16:30:13 +0100819 tty_unlock(tty);
Jiri Slabyecbbfd42012-10-18 22:26:47 +0200820 cancel_work_sync(&tty->port->buf.work);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200821 mutex_unlock(&tty->ldisc_mutex);
Jiri Slaby0c73c082011-11-16 16:27:09 +0100822retry:
Alan Cox89c8d912012-08-08 16:30:13 +0100823 tty_lock(tty);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200824 mutex_lock(&tty->ldisc_mutex);
825
Alan Cox638b9642010-02-08 10:09:26 +0000826 /* At this point we have a closed ldisc and we want to
827 reopen it. We could defer this to the next open but
828 it means auditing a lot of other paths so this is
829 a FIXME */
830 if (tty->ldisc) { /* Not yet closed */
Jiri Slaby0c73c082011-11-16 16:27:09 +0100831 if (atomic_read(&tty->ldisc->users) != 1) {
832 char cur_n[TASK_COMM_LEN], tty_n[64];
833 long timeout = 3 * HZ;
Alan Cox89c8d912012-08-08 16:30:13 +0100834 tty_unlock(tty);
Jiri Slaby0c73c082011-11-16 16:27:09 +0100835
836 while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
837 timeout = MAX_SCHEDULE_TIMEOUT;
838 printk_ratelimited(KERN_WARNING
839 "%s: waiting (%s) for %s took too long, but we keep waiting...\n",
840 __func__, get_task_comm(cur_n, current),
841 tty_name(tty, tty_n));
842 }
843 mutex_unlock(&tty->ldisc_mutex);
844 goto retry;
845 }
Jiri Slaby30042072011-11-16 16:27:08 +0100846
Alan Cox638b9642010-02-08 10:09:26 +0000847 if (reset == 0) {
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200848
Alan Coxadc8d742012-07-14 15:31:47 +0100849 if (!tty_ldisc_reinit(tty, tty->termios.c_line))
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200850 err = tty_ldisc_open(tty, tty->ldisc);
851 else
852 err = 1;
Alan Coxc8d50042009-07-16 16:05:08 +0100853 }
Alan Cox638b9642010-02-08 10:09:26 +0000854 /* If the re-open fails or we reset then go to N_TTY. The
855 N_TTY open cannot fail */
856 if (reset || err) {
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200857 BUG_ON(tty_ldisc_reinit(tty, N_TTY));
Alan Cox638b9642010-02-08 10:09:26 +0000858 WARN_ON(tty_ldisc_open(tty, tty->ldisc));
859 }
860 tty_ldisc_enable(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100861 }
Alan Cox638b9642010-02-08 10:09:26 +0000862 mutex_unlock(&tty->ldisc_mutex);
863 if (reset)
864 tty_reset_termios(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100865}
Alan Cox01e1abb2008-07-22 11:16:55 +0100866
867/**
868 * tty_ldisc_setup - open line discipline
869 * @tty: tty being shut down
870 * @o_tty: pair tty for pty/tty pairs
871 *
872 * Called during the initial open of a tty/pty pair in order to set up the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100873 * line disciplines and bind them to the tty. This has no locking issues
874 * as the device isn't yet active.
Alan Cox01e1abb2008-07-22 11:16:55 +0100875 */
876
877int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
878{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100879 struct tty_ldisc *ld = tty->ldisc;
Alan Cox01e1abb2008-07-22 11:16:55 +0100880 int retval;
881
Alan Coxc65c9bc2009-06-11 12:50:12 +0100882 retval = tty_ldisc_open(tty, ld);
883 if (retval)
884 return retval;
885
886 if (o_tty) {
887 retval = tty_ldisc_open(o_tty, o_tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100888 if (retval) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100889 tty_ldisc_close(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100890 return retval;
891 }
892 tty_ldisc_enable(o_tty);
893 }
894 tty_ldisc_enable(tty);
895 return 0;
896}
Alan Cox89c8d912012-08-08 16:30:13 +0100897
898static void tty_ldisc_kill(struct tty_struct *tty)
899{
Jiri Slaby31e12122012-10-18 22:26:33 +0200900 /* There cannot be users from userspace now. But there still might be
901 * drivers holding a reference via tty_ldisc_ref. Do not steal them the
902 * ldisc until they are done. */
903 tty_ldisc_wait_idle(tty, MAX_SCHEDULE_TIMEOUT);
904
Alan Cox89c8d912012-08-08 16:30:13 +0100905 mutex_lock(&tty->ldisc_mutex);
906 /*
907 * Now kill off the ldisc
908 */
909 tty_ldisc_close(tty, tty->ldisc);
910 tty_ldisc_put(tty->ldisc);
911 /* Force an oops if we mess this up */
912 tty->ldisc = NULL;
913
914 /* Ensure the next open requests the N_TTY ldisc */
915 tty_set_termios_ldisc(tty, N_TTY);
916 mutex_unlock(&tty->ldisc_mutex);
917}
918
Alan Cox01e1abb2008-07-22 11:16:55 +0100919/**
920 * tty_ldisc_release - release line discipline
921 * @tty: tty being shut down
922 * @o_tty: pair tty for pty/tty pairs
923 *
Alan Cox852e99d2009-06-11 12:51:41 +0100924 * Called during the final close of a tty/pty pair in order to shut down
925 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100926 * ldisc has not been opened.
Alan Cox01e1abb2008-07-22 11:16:55 +0100927 */
928
929void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
930{
Alan Cox01e1abb2008-07-22 11:16:55 +0100931 /*
932 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
933 * kill any delayed work. As this is the final close it does not
934 * race with the set_ldisc code path.
935 */
Alan Cox01e1abb2008-07-22 11:16:55 +0100936
Alan Cox89c8d912012-08-08 16:30:13 +0100937 tty_lock_pair(tty, o_tty);
Alan Coxe8b70e72009-06-11 12:48:02 +0100938 tty_ldisc_halt(tty);
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100939 tty_ldisc_flush_works(tty);
Alan Cox89c8d912012-08-08 16:30:13 +0100940 if (o_tty) {
941 tty_ldisc_halt(o_tty);
942 tty_ldisc_flush_works(o_tty);
943 }
Alan Coxd1552552012-07-27 18:02:54 +0100944
Alan Cox6d31a882012-07-14 15:31:27 +0100945 /* This will need doing differently if we need to lock */
Alan Cox89c8d912012-08-08 16:30:13 +0100946 tty_ldisc_kill(tty);
Alan Coxaef29bc2009-06-29 15:21:47 +0100947
Alan Cox89c8d912012-08-08 16:30:13 +0100948 if (o_tty)
949 tty_ldisc_kill(o_tty);
950
951 tty_unlock_pair(tty, o_tty);
Alan Coxaef29bc2009-06-29 15:21:47 +0100952 /* And the memory resources remaining (buffers, termios) will be
953 disposed of when the kref hits zero */
Alan Cox01e1abb2008-07-22 11:16:55 +0100954}
955
956/**
957 * tty_ldisc_init - ldisc setup for new tty
958 * @tty: tty being allocated
959 *
960 * Set up the line discipline objects for a newly allocated tty. Note that
961 * the tty structure is not completely set up when this call is made.
962 */
963
964void tty_ldisc_init(struct tty_struct *tty)
965{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100966 struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
967 if (IS_ERR(ld))
Alan Cox01e1abb2008-07-22 11:16:55 +0100968 panic("n_tty: init_tty");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100969 tty_ldisc_assign(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100970}
971
Jiri Slaby67166712011-03-23 10:48:35 +0100972/**
973 * tty_ldisc_init - ldisc cleanup for new tty
974 * @tty: tty that was allocated recently
975 *
976 * The tty structure must not becompletely set up (tty_ldisc_setup) when
977 * this call is made.
978 */
979void tty_ldisc_deinit(struct tty_struct *tty)
980{
981 put_ldisc(tty->ldisc);
982 tty_ldisc_assign(tty, NULL);
983}
984
Alan Cox01e1abb2008-07-22 11:16:55 +0100985void tty_ldisc_begin(void)
986{
987 /* Setup the default TTY line discipline. */
988 (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
989}