blob: cbb945b03cdbaa4ba2e958fe7cf2ee1771a2f052 [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 Siebenbd5d7ce2012-12-18 15:48:50 +010067
68 if (waitqueue_active(&ld->wq_idle))
69 wake_up(&ld->wq_idle);
Linus Torvalds65b77042009-08-03 11:11:19 -070070}
71
Alan Cox01e1abb2008-07-22 11:16:55 +010072/**
73 * tty_register_ldisc - install a line discipline
74 * @disc: ldisc number
75 * @new_ldisc: pointer to the ldisc object
76 *
77 * Installs a new line discipline into the kernel. The discipline
78 * is set up as unreferenced and then made available to the kernel
79 * from this point onwards.
80 *
81 * Locking:
82 * takes tty_ldisc_lock to guard against ldisc races
83 */
84
85int tty_register_ldisc(int disc, struct tty_ldisc_ops *new_ldisc)
86{
87 unsigned long flags;
88 int ret = 0;
89
90 if (disc < N_TTY || disc >= NR_LDISCS)
91 return -EINVAL;
92
Ivo Siebenc9739942012-10-17 14:03:14 +020093 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Alan Cox01e1abb2008-07-22 11:16:55 +010094 tty_ldiscs[disc] = new_ldisc;
95 new_ldisc->num = disc;
96 new_ldisc->refcount = 0;
Ivo Siebenc9739942012-10-17 14:03:14 +020097 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Alan Cox01e1abb2008-07-22 11:16:55 +010098
99 return ret;
100}
101EXPORT_SYMBOL(tty_register_ldisc);
102
103/**
104 * tty_unregister_ldisc - unload a line discipline
105 * @disc: ldisc number
106 * @new_ldisc: pointer to the ldisc object
107 *
108 * Remove a line discipline from the kernel providing it is not
109 * currently in use.
110 *
111 * Locking:
112 * takes tty_ldisc_lock to guard against ldisc races
113 */
114
115int tty_unregister_ldisc(int disc)
116{
117 unsigned long flags;
118 int ret = 0;
119
120 if (disc < N_TTY || disc >= NR_LDISCS)
121 return -EINVAL;
122
Ivo Siebenc9739942012-10-17 14:03:14 +0200123 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100124 if (tty_ldiscs[disc]->refcount)
125 ret = -EBUSY;
126 else
127 tty_ldiscs[disc] = NULL;
Ivo Siebenc9739942012-10-17 14:03:14 +0200128 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100129
130 return ret;
131}
132EXPORT_SYMBOL(tty_unregister_ldisc);
133
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700134static struct tty_ldisc_ops *get_ldops(int disc)
135{
136 unsigned long flags;
137 struct tty_ldisc_ops *ldops, *ret;
138
Ivo Siebenc9739942012-10-17 14:03:14 +0200139 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700140 ret = ERR_PTR(-EINVAL);
141 ldops = tty_ldiscs[disc];
142 if (ldops) {
143 ret = ERR_PTR(-EAGAIN);
144 if (try_module_get(ldops->owner)) {
145 ldops->refcount++;
146 ret = ldops;
147 }
148 }
Ivo Siebenc9739942012-10-17 14:03:14 +0200149 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700150 return ret;
151}
152
153static void put_ldops(struct tty_ldisc_ops *ldops)
154{
155 unsigned long flags;
156
Ivo Siebenc9739942012-10-17 14:03:14 +0200157 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700158 ldops->refcount--;
159 module_put(ldops->owner);
Ivo Siebenc9739942012-10-17 14:03:14 +0200160 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700161}
Alan Cox01e1abb2008-07-22 11:16:55 +0100162
163/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100164 * tty_ldisc_get - take a reference to an ldisc
165 * @disc: ldisc number
Alan Cox01e1abb2008-07-22 11:16:55 +0100166 *
167 * Takes a reference to a line discipline. Deals with refcounts and
168 * module locking counts. Returns NULL if the discipline is not available.
169 * Returns a pointer to the discipline and bumps the ref count if it is
170 * available
171 *
172 * Locking:
173 * takes tty_ldisc_lock to guard against ldisc races
174 */
175
Alan Coxc65c9bc2009-06-11 12:50:12 +0100176static struct tty_ldisc *tty_ldisc_get(int disc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100177{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100178 struct tty_ldisc *ld;
Linus Torvalds182274f2009-08-03 16:01:28 -0700179 struct tty_ldisc_ops *ldops;
Alan Cox01e1abb2008-07-22 11:16:55 +0100180
181 if (disc < N_TTY || disc >= NR_LDISCS)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100182 return ERR_PTR(-EINVAL);
Linus Torvalds182274f2009-08-03 16:01:28 -0700183
184 /*
185 * Get the ldisc ops - we may need to request them to be loaded
186 * dynamically and try again.
187 */
188 ldops = get_ldops(disc);
189 if (IS_ERR(ldops)) {
Alan Cox01e1abb2008-07-22 11:16:55 +0100190 request_module("tty-ldisc-%d", disc);
Linus Torvalds182274f2009-08-03 16:01:28 -0700191 ldops = get_ldops(disc);
192 if (IS_ERR(ldops))
193 return ERR_CAST(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100194 }
Linus Torvalds182274f2009-08-03 16:01:28 -0700195
196 ld = kmalloc(sizeof(struct tty_ldisc), GFP_KERNEL);
197 if (ld == NULL) {
198 put_ldops(ldops);
199 return ERR_PTR(-ENOMEM);
200 }
201
202 ld->ops = ldops;
203 atomic_set(&ld->users, 1);
Ivo Sieben1541f842012-05-03 14:37:43 +0200204 init_waitqueue_head(&ld->wq_idle);
205
Alan Coxc65c9bc2009-06-11 12:50:12 +0100206 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100207}
208
Alan Cox852e99d2009-06-11 12:51:41 +0100209static void *tty_ldiscs_seq_start(struct seq_file *m, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100210{
211 return (*pos < NR_LDISCS) ? pos : NULL;
212}
213
Alan Cox852e99d2009-06-11 12:51:41 +0100214static void *tty_ldiscs_seq_next(struct seq_file *m, void *v, loff_t *pos)
Alan Cox01e1abb2008-07-22 11:16:55 +0100215{
216 (*pos)++;
217 return (*pos < NR_LDISCS) ? pos : NULL;
218}
219
220static void tty_ldiscs_seq_stop(struct seq_file *m, void *v)
221{
222}
223
224static int tty_ldiscs_seq_show(struct seq_file *m, void *v)
225{
226 int i = *(loff_t *)v;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700227 struct tty_ldisc_ops *ldops;
Alan Cox852e99d2009-06-11 12:51:41 +0100228
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700229 ldops = get_ldops(i);
230 if (IS_ERR(ldops))
Alan Cox01e1abb2008-07-22 11:16:55 +0100231 return 0;
Linus Torvaldsf0de0e82009-08-03 16:00:15 -0700232 seq_printf(m, "%-10s %2d\n", ldops->name ? ldops->name : "???", i);
233 put_ldops(ldops);
Alan Cox01e1abb2008-07-22 11:16:55 +0100234 return 0;
235}
236
237static const struct seq_operations tty_ldiscs_seq_ops = {
238 .start = tty_ldiscs_seq_start,
239 .next = tty_ldiscs_seq_next,
240 .stop = tty_ldiscs_seq_stop,
241 .show = tty_ldiscs_seq_show,
242};
243
244static int proc_tty_ldiscs_open(struct inode *inode, struct file *file)
245{
246 return seq_open(file, &tty_ldiscs_seq_ops);
247}
248
249const struct file_operations tty_ldiscs_proc_fops = {
250 .owner = THIS_MODULE,
251 .open = proc_tty_ldiscs_open,
252 .read = seq_read,
253 .llseek = seq_lseek,
254 .release = seq_release,
255};
256
257/**
258 * tty_ldisc_assign - set ldisc on a tty
259 * @tty: tty to assign
260 * @ld: line discipline
261 *
262 * Install an instance of a line discipline into a tty structure. The
Alan Cox8d2ead72009-06-16 17:00:26 +0100263 * ldisc must have a reference count above zero to ensure it remains.
Alan Cox01e1abb2008-07-22 11:16:55 +0100264 * The tty instance refcount starts at zero.
265 *
266 * Locking:
267 * Caller must hold references
268 */
269
270static void tty_ldisc_assign(struct tty_struct *tty, struct tty_ldisc *ld)
271{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100272 tty->ldisc = ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100273}
274
275/**
276 * tty_ldisc_try - internal helper
277 * @tty: the tty
278 *
279 * Make a single attempt to grab and bump the refcount on
280 * the tty ldisc. Return 0 on failure or 1 on success. This is
281 * used to implement both the waiting and non waiting versions
282 * of tty_ldisc_ref
283 *
284 * Locking: takes tty_ldisc_lock
285 */
286
Linus Torvalds65b77042009-08-03 11:11:19 -0700287static struct tty_ldisc *tty_ldisc_try(struct tty_struct *tty)
Alan Cox01e1abb2008-07-22 11:16:55 +0100288{
289 unsigned long flags;
290 struct tty_ldisc *ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100291
Ivo Siebenc9739942012-10-17 14:03:14 +0200292 raw_spin_lock_irqsave(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700293 ld = NULL;
294 if (test_bit(TTY_LDISC, &tty->flags))
295 ld = get_ldisc(tty->ldisc);
Ivo Siebenc9739942012-10-17 14:03:14 +0200296 raw_spin_unlock_irqrestore(&tty_ldisc_lock, flags);
Linus Torvalds65b77042009-08-03 11:11:19 -0700297 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100298}
299
300/**
301 * tty_ldisc_ref_wait - wait for the tty ldisc
302 * @tty: tty device
303 *
304 * Dereference the line discipline for the terminal and take a
305 * reference to it. If the line discipline is in flux then
306 * wait patiently until it changes.
307 *
308 * Note: Must not be called from an IRQ/timer context. The caller
309 * must also be careful not to hold other locks that will deadlock
310 * against a discipline change, such as an existing ldisc reference
311 * (which we check for)
312 *
313 * Locking: call functions take tty_ldisc_lock
314 */
315
316struct tty_ldisc *tty_ldisc_ref_wait(struct tty_struct *tty)
317{
Linus Torvalds65b77042009-08-03 11:11:19 -0700318 struct tty_ldisc *ld;
319
Alan Cox01e1abb2008-07-22 11:16:55 +0100320 /* wait_event is a macro */
Linus Torvalds65b77042009-08-03 11:11:19 -0700321 wait_event(tty_ldisc_wait, (ld = tty_ldisc_try(tty)) != NULL);
322 return ld;
Alan Cox01e1abb2008-07-22 11:16:55 +0100323}
Alan Cox01e1abb2008-07-22 11:16:55 +0100324EXPORT_SYMBOL_GPL(tty_ldisc_ref_wait);
325
326/**
327 * tty_ldisc_ref - get the tty ldisc
328 * @tty: tty device
329 *
330 * Dereference the line discipline for the terminal and take a
331 * reference to it. If the line discipline is in flux then
332 * return NULL. Can be called from IRQ and timer functions.
333 *
334 * Locking: called functions take tty_ldisc_lock
335 */
336
337struct tty_ldisc *tty_ldisc_ref(struct tty_struct *tty)
338{
Linus Torvalds65b77042009-08-03 11:11:19 -0700339 return tty_ldisc_try(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100340}
Alan Cox01e1abb2008-07-22 11:16:55 +0100341EXPORT_SYMBOL_GPL(tty_ldisc_ref);
342
343/**
344 * tty_ldisc_deref - free a tty ldisc reference
345 * @ld: reference to free up
346 *
347 * Undoes the effect of tty_ldisc_ref or tty_ldisc_ref_wait. May
348 * be called in IRQ context.
349 *
350 * Locking: takes tty_ldisc_lock
351 */
352
353void tty_ldisc_deref(struct tty_ldisc *ld)
354{
Linus Torvalds65b77042009-08-03 11:11:19 -0700355 put_ldisc(ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100356}
Alan Cox01e1abb2008-07-22 11:16:55 +0100357EXPORT_SYMBOL_GPL(tty_ldisc_deref);
358
Linus Torvalds65b77042009-08-03 11:11:19 -0700359static inline void tty_ldisc_put(struct tty_ldisc *ld)
360{
361 put_ldisc(ld);
362}
363
Alan Cox01e1abb2008-07-22 11:16:55 +0100364/**
365 * tty_ldisc_enable - allow ldisc use
366 * @tty: terminal to activate ldisc on
367 *
368 * Set the TTY_LDISC flag when the line discipline can be called
Alan Coxc9b39762009-01-02 13:44:56 +0000369 * again. Do necessary wakeups for existing sleepers. Clear the LDISC
370 * changing flag to indicate any ldisc change is now over.
Alan Cox01e1abb2008-07-22 11:16:55 +0100371 *
Alan Coxc9b39762009-01-02 13:44:56 +0000372 * Note: nobody should set the TTY_LDISC bit except via this function.
373 * Clearing directly is allowed.
Alan Cox01e1abb2008-07-22 11:16:55 +0100374 */
375
Peter Hurleyd9121562013-03-11 16:44:33 -0400376static void tty_ldisc_enable(struct tty_struct *tty)
Alan Cox01e1abb2008-07-22 11:16:55 +0100377{
Peter Hurley21622932013-03-11 16:44:21 -0400378 clear_bit(TTY_LDISC_HALTED, &tty->flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100379 set_bit(TTY_LDISC, &tty->flags);
Alan Coxc9b39762009-01-02 13:44:56 +0000380 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox01e1abb2008-07-22 11:16:55 +0100381 wake_up(&tty_ldisc_wait);
382}
383
384/**
Alan Coxf2c4c652009-06-11 12:50:58 +0100385 * tty_ldisc_flush - flush line discipline queue
386 * @tty: tty
387 *
388 * Flush the line discipline queue (if any) for this tty. If there
389 * is no line discipline active this is a no-op.
390 */
391
392void tty_ldisc_flush(struct tty_struct *tty)
393{
394 struct tty_ldisc *ld = tty_ldisc_ref(tty);
395 if (ld) {
396 if (ld->ops->flush_buffer)
397 ld->ops->flush_buffer(tty);
398 tty_ldisc_deref(ld);
399 }
400 tty_buffer_flush(tty);
401}
Alan Coxf2c4c652009-06-11 12:50:58 +0100402EXPORT_SYMBOL_GPL(tty_ldisc_flush);
403
404/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100405 * tty_set_termios_ldisc - set ldisc field
406 * @tty: tty structure
407 * @num: line discipline number
408 *
409 * This is probably overkill for real world processors but
410 * they are not on hot paths so a little discipline won't do
411 * any harm.
412 *
413 * Locking: takes termios_mutex
414 */
415
416static void tty_set_termios_ldisc(struct tty_struct *tty, int num)
417{
418 mutex_lock(&tty->termios_mutex);
Alan Coxadc8d742012-07-14 15:31:47 +0100419 tty->termios.c_line = num;
Alan Cox01e1abb2008-07-22 11:16:55 +0100420 mutex_unlock(&tty->termios_mutex);
421}
422
Alan Coxc65c9bc2009-06-11 12:50:12 +0100423/**
424 * tty_ldisc_open - open a line discipline
425 * @tty: tty we are opening the ldisc on
426 * @ld: discipline to open
427 *
428 * A helper opening method. Also a convenient debugging and check
429 * point.
Arnd Bergmannec79d602010-06-01 22:53:01 +0200430 *
431 * Locking: always called with BTM already held.
Alan Coxc65c9bc2009-06-11 12:50:12 +0100432 */
433
434static int tty_ldisc_open(struct tty_struct *tty, struct tty_ldisc *ld)
435{
436 WARN_ON(test_and_set_bit(TTY_LDISC_OPEN, &tty->flags));
Alan Coxf18f9492009-11-30 13:18:35 +0000437 if (ld->ops->open) {
438 int ret;
Arnd Bergmannec79d602010-06-01 22:53:01 +0200439 /* BTM here locks versus a hangup event */
Alan Coxf18f9492009-11-30 13:18:35 +0000440 ret = ld->ops->open(tty);
Jiri Slaby7f90cfc2010-11-25 00:27:54 +0100441 if (ret)
442 clear_bit(TTY_LDISC_OPEN, &tty->flags);
Alan Coxf18f9492009-11-30 13:18:35 +0000443 return ret;
444 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100445 return 0;
446}
447
448/**
449 * tty_ldisc_close - close a line discipline
450 * @tty: tty we are opening the ldisc on
451 * @ld: discipline to close
452 *
453 * A helper close method. Also a convenient debugging and check
454 * point.
455 */
456
457static void tty_ldisc_close(struct tty_struct *tty, struct tty_ldisc *ld)
458{
459 WARN_ON(!test_bit(TTY_LDISC_OPEN, &tty->flags));
460 clear_bit(TTY_LDISC_OPEN, &tty->flags);
461 if (ld->ops->close)
462 ld->ops->close(tty);
463}
Alan Cox01e1abb2008-07-22 11:16:55 +0100464
465/**
466 * tty_ldisc_restore - helper for tty ldisc change
467 * @tty: tty to recover
468 * @old: previous ldisc
469 *
470 * Restore the previous line discipline or N_TTY when a line discipline
471 * change fails due to an open error
472 */
473
474static void tty_ldisc_restore(struct tty_struct *tty, struct tty_ldisc *old)
475{
476 char buf[64];
Alan Coxc65c9bc2009-06-11 12:50:12 +0100477 struct tty_ldisc *new_ldisc;
478 int r;
Alan Cox01e1abb2008-07-22 11:16:55 +0100479
480 /* There is an outstanding reference here so this is safe */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100481 old = tty_ldisc_get(old->ops->num);
482 WARN_ON(IS_ERR(old));
Alan Cox01e1abb2008-07-22 11:16:55 +0100483 tty_ldisc_assign(tty, old);
484 tty_set_termios_ldisc(tty, old->ops->num);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100485 if (tty_ldisc_open(tty, old) < 0) {
486 tty_ldisc_put(old);
Alan Cox01e1abb2008-07-22 11:16:55 +0100487 /* This driver is always present */
Alan Cox852e99d2009-06-11 12:51:41 +0100488 new_ldisc = tty_ldisc_get(N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100489 if (IS_ERR(new_ldisc))
Alan Cox01e1abb2008-07-22 11:16:55 +0100490 panic("n_tty: get");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100491 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100492 tty_set_termios_ldisc(tty, N_TTY);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100493 r = tty_ldisc_open(tty, new_ldisc);
494 if (r < 0)
495 panic("Couldn't open N_TTY ldisc for "
496 "%s --- error %d.",
497 tty_name(tty, buf), r);
Alan Cox01e1abb2008-07-22 11:16:55 +0100498 }
499}
500
501/**
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100502 * tty_ldisc_flush_works - flush all works of a tty
503 * @tty: tty device to flush works for
504 *
505 * Sync flush all works belonging to @tty.
506 */
507static void tty_ldisc_flush_works(struct tty_struct *tty)
508{
Tejun Heo43829732012-08-20 14:51:24 -0700509 flush_work(&tty->SAK_work);
Peter Hurley977066e2013-03-11 16:44:30 -0400510 flush_work(&tty->hangup_work);
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100511}
512
513/**
Jiri Slaby100eeae2010-10-31 23:17:51 +0100514 * tty_ldisc_wait_idle - wait for the ldisc to become idle
515 * @tty: tty to wait for
Jiri Slabydf92d052011-11-16 16:27:07 +0100516 * @timeout: for how long to wait at most
Jiri Slaby100eeae2010-10-31 23:17:51 +0100517 *
518 * Wait for the line discipline to become idle. The discipline must
519 * have been halted for this to guarantee it remains idle.
520 */
Jiri Slabydf92d052011-11-16 16:27:07 +0100521static int tty_ldisc_wait_idle(struct tty_struct *tty, long timeout)
Jiri Slaby100eeae2010-10-31 23:17:51 +0100522{
Jiri Slabydf92d052011-11-16 16:27:07 +0100523 long ret;
Ivo Sieben1541f842012-05-03 14:37:43 +0200524 ret = wait_event_timeout(tty->ldisc->wq_idle,
Jiri Slabydf92d052011-11-16 16:27:07 +0100525 atomic_read(&tty->ldisc->users) == 1, timeout);
Jiri Slaby100eeae2010-10-31 23:17:51 +0100526 return ret > 0 ? 0 : -EBUSY;
527}
528
529/**
Peter Hurley11cf48e2013-03-11 16:44:27 -0400530 * tty_ldisc_halt - shut down the line discipline
531 * @tty: tty device
Peter Hurleyf4cf7a32013-03-11 16:44:29 -0400532 * @o_tty: paired pty device (can be NULL)
Peter Hurleycf528472013-03-11 16:44:28 -0400533 * @timeout: # of jiffies to wait for ldisc refs to be released
Peter Hurley11cf48e2013-03-11 16:44:27 -0400534 *
Peter Hurleyf4cf7a32013-03-11 16:44:29 -0400535 * Shut down the line discipline and work queue for this tty device and
536 * its paired pty (if exists). Clearing the TTY_LDISC flag ensures
Peter Hurley4f98d462013-03-11 16:44:34 -0400537 * no further references can be obtained, while waiting for existing
538 * references to be released ensures no more data is fed to the ldisc.
Peter Hurleycf528472013-03-11 16:44:28 -0400539 *
Peter Hurley11cf48e2013-03-11 16:44:27 -0400540 * You need to do a 'flush_scheduled_work()' (outside the ldisc_mutex)
541 * in order to make sure any currently executing ldisc work is also
542 * flushed.
543 */
544
Peter Hurleyf4cf7a32013-03-11 16:44:29 -0400545static int tty_ldisc_halt(struct tty_struct *tty, struct tty_struct *o_tty,
Peter Hurley4f98d462013-03-11 16:44:34 -0400546 long timeout)
Peter Hurley11cf48e2013-03-11 16:44:27 -0400547{
Peter Hurley4f98d462013-03-11 16:44:34 -0400548 int retval;
Peter Hurleycf528472013-03-11 16:44:28 -0400549
Peter Hurley11cf48e2013-03-11 16:44:27 -0400550 clear_bit(TTY_LDISC, &tty->flags);
Peter Hurleyf4cf7a32013-03-11 16:44:29 -0400551 if (o_tty)
552 clear_bit(TTY_LDISC, &o_tty->flags);
553
Peter Hurleycf528472013-03-11 16:44:28 -0400554 retval = tty_ldisc_wait_idle(tty, timeout);
Peter Hurleyf4cf7a32013-03-11 16:44:29 -0400555 if (!retval && o_tty)
556 retval = tty_ldisc_wait_idle(o_tty, timeout);
Peter Hurleycf528472013-03-11 16:44:28 -0400557 if (retval)
558 return retval;
559
Peter Hurley11cf48e2013-03-11 16:44:27 -0400560 set_bit(TTY_LDISC_HALTED, &tty->flags);
Peter Hurley4f98d462013-03-11 16:44:34 -0400561 if (o_tty)
Peter Hurleyf4cf7a32013-03-11 16:44:29 -0400562 set_bit(TTY_LDISC_HALTED, &o_tty->flags);
Peter Hurleyf4cf7a32013-03-11 16:44:29 -0400563
Peter Hurleycf528472013-03-11 16:44:28 -0400564 return 0;
Peter Hurley11cf48e2013-03-11 16:44:27 -0400565}
566
567/**
Peter Hurley76bc35e2013-03-11 16:44:26 -0400568 * tty_ldisc_hangup_halt - halt the line discipline for hangup
569 * @tty: tty being hung up
Peter Hurley168942c2013-03-11 16:44:24 -0400570 *
Peter Hurley76bc35e2013-03-11 16:44:26 -0400571 * Shut down the line discipline and work queue for the tty device
572 * being hungup. Clear the TTY_LDISC flag to ensure no further
Peter Hurley4f98d462013-03-11 16:44:34 -0400573 * references can be obtained and wait for remaining references to be
574 * released to ensure no more data is fed to this ldisc.
Peter Hurley168942c2013-03-11 16:44:24 -0400575 * Caller must hold legacy and ->ldisc_mutex.
Peter Hurley2276ad92013-03-11 16:44:25 -0400576 *
577 * NB: tty_set_ldisc() is prevented from changing the ldisc concurrently
578 * with this function by checking the TTY_HUPPING flag.
Peter Hurley168942c2013-03-11 16:44:24 -0400579 */
Peter Hurley76bc35e2013-03-11 16:44:26 -0400580static bool tty_ldisc_hangup_halt(struct tty_struct *tty)
Peter Hurley168942c2013-03-11 16:44:24 -0400581{
Peter Hurley2276ad92013-03-11 16:44:25 -0400582 char cur_n[TASK_COMM_LEN], tty_n[64];
583 long timeout = 3 * HZ;
Peter Hurley168942c2013-03-11 16:44:24 -0400584
Peter Hurley76bc35e2013-03-11 16:44:26 -0400585 clear_bit(TTY_LDISC, &tty->flags);
586
Peter Hurley2276ad92013-03-11 16:44:25 -0400587 if (tty->ldisc) { /* Not yet closed */
588 tty_unlock(tty);
589
590 while (tty_ldisc_wait_idle(tty, timeout) == -EBUSY) {
591 timeout = MAX_SCHEDULE_TIMEOUT;
592 printk_ratelimited(KERN_WARNING
593 "%s: waiting (%s) for %s took too long, but we keep waiting...\n",
594 __func__, get_task_comm(cur_n, current),
595 tty_name(tty, tty_n));
Peter Hurley168942c2013-03-11 16:44:24 -0400596 }
Peter Hurley76bc35e2013-03-11 16:44:26 -0400597
Peter Hurley76bc35e2013-03-11 16:44:26 -0400598 set_bit(TTY_LDISC_HALTED, &tty->flags);
599
Peter Hurley2276ad92013-03-11 16:44:25 -0400600 /* must reacquire both locks and preserve lock order */
601 mutex_unlock(&tty->ldisc_mutex);
602 tty_lock(tty);
603 mutex_lock(&tty->ldisc_mutex);
Peter Hurley168942c2013-03-11 16:44:24 -0400604 }
605 return !!tty->ldisc;
606}
607
608/**
Alan Cox01e1abb2008-07-22 11:16:55 +0100609 * tty_set_ldisc - set line discipline
610 * @tty: the terminal to set
611 * @ldisc: the line discipline
612 *
613 * Set the discipline of a tty line. Must be called from a process
Alan Coxc65c9bc2009-06-11 12:50:12 +0100614 * context. The ldisc change logic has to protect itself against any
615 * overlapping ldisc change (including on the other end of pty pairs),
616 * the close of one side of a tty/pty pair, and eventually hangup.
Alan Cox01e1abb2008-07-22 11:16:55 +0100617 *
Alan Coxc65c9bc2009-06-11 12:50:12 +0100618 * Locking: takes tty_ldisc_lock, termios_mutex
Alan Cox01e1abb2008-07-22 11:16:55 +0100619 */
620
621int tty_set_ldisc(struct tty_struct *tty, int ldisc)
622{
623 int retval;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100624 struct tty_ldisc *o_ldisc, *new_ldisc;
Alan Cox01e1abb2008-07-22 11:16:55 +0100625 struct tty_struct *o_tty;
626
Alan Coxc65c9bc2009-06-11 12:50:12 +0100627 new_ldisc = tty_ldisc_get(ldisc);
628 if (IS_ERR(new_ldisc))
629 return PTR_ERR(new_ldisc);
630
Alan Cox89c8d912012-08-08 16:30:13 +0100631 tty_lock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100632 /*
633 * We need to look at the tty locking here for pty/tty pairs
634 * when both sides try to change in parallel.
635 */
636
637 o_tty = tty->link; /* o_tty is the pty side or NULL */
638
639
640 /*
641 * Check the no-op case
642 */
643
644 if (tty->ldisc->ops->num == ldisc) {
Alan Cox89c8d912012-08-08 16:30:13 +0100645 tty_unlock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100646 tty_ldisc_put(new_ldisc);
647 return 0;
648 }
Alan Cox01e1abb2008-07-22 11:16:55 +0100649
Alan Cox89c8d912012-08-08 16:30:13 +0100650 tty_unlock(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100651 /*
652 * Problem: What do we do if this blocks ?
Alan Coxc65c9bc2009-06-11 12:50:12 +0100653 * We could deadlock here
Alan Cox01e1abb2008-07-22 11:16:55 +0100654 */
655
656 tty_wait_until_sent(tty, 0);
657
Alan Cox89c8d912012-08-08 16:30:13 +0100658 tty_lock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100659 mutex_lock(&tty->ldisc_mutex);
Alan Cox01e1abb2008-07-22 11:16:55 +0100660
661 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100662 * We could be midstream of another ldisc change which has
663 * dropped the lock during processing. If so we need to wait.
664 */
665
666 while (test_bit(TTY_LDISC_CHANGING, &tty->flags)) {
667 mutex_unlock(&tty->ldisc_mutex);
Alan Cox89c8d912012-08-08 16:30:13 +0100668 tty_unlock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100669 wait_event(tty_ldisc_wait,
670 test_bit(TTY_LDISC_CHANGING, &tty->flags) == 0);
Alan Cox89c8d912012-08-08 16:30:13 +0100671 tty_lock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100672 mutex_lock(&tty->ldisc_mutex);
673 }
Alan Coxeeb89d92009-11-30 13:18:29 +0000674
Alan Coxc65c9bc2009-06-11 12:50:12 +0100675 set_bit(TTY_LDISC_CHANGING, &tty->flags);
Alan Cox852e99d2009-06-11 12:51:41 +0100676
Alan Coxc65c9bc2009-06-11 12:50:12 +0100677 /*
Alan Cox01e1abb2008-07-22 11:16:55 +0100678 * No more input please, we are switching. The new ldisc
679 * will update this value in the ldisc open function
680 */
681
682 tty->receive_room = 0;
683
684 o_ldisc = tty->ldisc;
Alan Coxeeb89d92009-11-30 13:18:29 +0000685
Alan Cox89c8d912012-08-08 16:30:13 +0100686 tty_unlock(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100687 /*
688 * Make sure we don't change while someone holds a
689 * reference to the line discipline. The TTY_LDISC bit
690 * prevents anyone taking a reference once it is clear.
691 * We need the lock to avoid racing reference takers.
Alan Coxc9b39762009-01-02 13:44:56 +0000692 *
693 * We must clear the TTY_LDISC bit here to avoid a livelock
694 * with a userspace app continually trying to use the tty in
695 * parallel to the change and re-referencing the tty.
Alan Cox01e1abb2008-07-22 11:16:55 +0100696 */
697
Peter Hurley4f98d462013-03-11 16:44:34 -0400698 retval = tty_ldisc_halt(tty, o_tty, 5 * HZ);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100699
Alan Cox01e1abb2008-07-22 11:16:55 +0100700 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100701 * Wait for ->hangup_work and ->buf.work handlers to terminate.
702 * We must drop the mutex here in case a hangup is also in process.
Alan Cox01e1abb2008-07-22 11:16:55 +0100703 */
704
Alan Coxc65c9bc2009-06-11 12:50:12 +0100705 mutex_unlock(&tty->ldisc_mutex);
706
Tejun Heo0a1f1a02011-01-24 17:54:12 +0100707 tty_ldisc_flush_works(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100708
Alan Cox89c8d912012-08-08 16:30:13 +0100709 tty_lock(tty);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200710 mutex_lock(&tty->ldisc_mutex);
Jiri Slaby100eeae2010-10-31 23:17:51 +0100711
712 /* handle wait idle failure locked */
713 if (retval) {
714 tty_ldisc_put(new_ldisc);
715 goto enable;
716 }
717
Shachar Shemesh40c9f612012-07-10 07:54:13 +0300718 if (test_bit(TTY_HUPPING, &tty->flags)) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100719 /* We were raced by the hangup method. It will have stomped
720 the ldisc data and closed the ldisc down */
721 clear_bit(TTY_LDISC_CHANGING, &tty->flags);
722 mutex_unlock(&tty->ldisc_mutex);
723 tty_ldisc_put(new_ldisc);
Alan Cox89c8d912012-08-08 16:30:13 +0100724 tty_unlock(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100725 return -EIO;
726 }
727
Alan Cox01e1abb2008-07-22 11:16:55 +0100728 /* Shutdown the current discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100729 tty_ldisc_close(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100730
731 /* Now set up the new line discipline. */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100732 tty_ldisc_assign(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100733 tty_set_termios_ldisc(tty, ldisc);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100734
735 retval = tty_ldisc_open(tty, new_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100736 if (retval < 0) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100737 /* Back to the old one or N_TTY if we can't */
738 tty_ldisc_put(new_ldisc);
739 tty_ldisc_restore(tty, o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100740 }
Alan Coxc65c9bc2009-06-11 12:50:12 +0100741
Alan Cox01e1abb2008-07-22 11:16:55 +0100742 /* At this point we hold a reference to the new ldisc and a
743 a reference to the old ldisc. If we ended up flipping back
744 to the existing ldisc we have two references to it */
745
Alan Coxc65c9bc2009-06-11 12:50:12 +0100746 if (tty->ldisc->ops->num != o_ldisc->ops->num && tty->ops->set_ldisc)
Alan Cox01e1abb2008-07-22 11:16:55 +0100747 tty->ops->set_ldisc(tty);
748
Alan Coxc65c9bc2009-06-11 12:50:12 +0100749 tty_ldisc_put(o_ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100750
Jiri Slaby100eeae2010-10-31 23:17:51 +0100751enable:
Alan Cox01e1abb2008-07-22 11:16:55 +0100752 /*
Alan Coxc65c9bc2009-06-11 12:50:12 +0100753 * Allow ldisc referencing to occur again
Alan Cox01e1abb2008-07-22 11:16:55 +0100754 */
755
756 tty_ldisc_enable(tty);
757 if (o_tty)
758 tty_ldisc_enable(o_tty);
759
Alan Coxc65c9bc2009-06-11 12:50:12 +0100760 /* Restart the work queue in case no characters kick it off. Safe if
Alan Cox01e1abb2008-07-22 11:16:55 +0100761 already running */
Peter Hurley4f98d462013-03-11 16:44:34 -0400762 schedule_work(&tty->port->buf.work);
763 if (o_tty)
Jiri Slabyecbbfd42012-10-18 22:26:47 +0200764 schedule_work(&o_tty->port->buf.work);
Peter Hurley4f98d462013-03-11 16:44:34 -0400765
Alan Coxc65c9bc2009-06-11 12:50:12 +0100766 mutex_unlock(&tty->ldisc_mutex);
Alan Cox89c8d912012-08-08 16:30:13 +0100767 tty_unlock(tty);
Alan Cox01e1abb2008-07-22 11:16:55 +0100768 return retval;
769}
770
Alan Coxc65c9bc2009-06-11 12:50:12 +0100771/**
772 * tty_reset_termios - reset terminal state
773 * @tty: tty to reset
774 *
775 * Restore a terminal to the driver default state.
776 */
777
778static void tty_reset_termios(struct tty_struct *tty)
779{
780 mutex_lock(&tty->termios_mutex);
Alan Coxadc8d742012-07-14 15:31:47 +0100781 tty->termios = tty->driver->init_termios;
782 tty->termios.c_ispeed = tty_termios_input_baud_rate(&tty->termios);
783 tty->termios.c_ospeed = tty_termios_baud_rate(&tty->termios);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100784 mutex_unlock(&tty->termios_mutex);
785}
786
787
788/**
789 * tty_ldisc_reinit - reinitialise the tty ldisc
790 * @tty: tty to reinit
Alan Cox638b9642010-02-08 10:09:26 +0000791 * @ldisc: line discipline to reinitialize
Alan Coxc65c9bc2009-06-11 12:50:12 +0100792 *
Alan Cox638b9642010-02-08 10:09:26 +0000793 * Switch the tty to a line discipline and leave the ldisc
794 * state closed
Alan Coxc65c9bc2009-06-11 12:50:12 +0100795 */
796
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200797static int tty_ldisc_reinit(struct tty_struct *tty, int ldisc)
Alan Coxc65c9bc2009-06-11 12:50:12 +0100798{
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200799 struct tty_ldisc *ld = tty_ldisc_get(ldisc);
800
801 if (IS_ERR(ld))
802 return -1;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100803
804 tty_ldisc_close(tty, tty->ldisc);
805 tty_ldisc_put(tty->ldisc);
806 tty->ldisc = NULL;
807 /*
808 * Switch the line discipline back
809 */
Alan Coxc65c9bc2009-06-11 12:50:12 +0100810 tty_ldisc_assign(tty, ld);
Alan Cox638b9642010-02-08 10:09:26 +0000811 tty_set_termios_ldisc(tty, ldisc);
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200812
813 return 0;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100814}
815
816/**
817 * tty_ldisc_hangup - hangup ldisc reset
818 * @tty: tty being hung up
819 *
820 * Some tty devices reset their termios when they receive a hangup
821 * event. In that situation we must also switch back to N_TTY properly
822 * before we reset the termios data.
823 *
824 * Locking: We can take the ldisc mutex as the rest of the code is
825 * careful to allow for this.
826 *
827 * In the pty pair case this occurs in the close() path of the
828 * tty itself so we must be careful about locking rules.
829 */
830
831void tty_ldisc_hangup(struct tty_struct *tty)
832{
833 struct tty_ldisc *ld;
Alan Cox638b9642010-02-08 10:09:26 +0000834 int reset = tty->driver->flags & TTY_DRIVER_RESET_TERMIOS;
835 int err = 0;
Alan Coxc65c9bc2009-06-11 12:50:12 +0100836
837 /*
838 * FIXME! What are the locking issues here? This may me overdoing
839 * things... This question is especially important now that we've
840 * removed the irqlock.
841 */
842 ld = tty_ldisc_ref(tty);
843 if (ld != NULL) {
844 /* We may have no line discipline at this point */
845 if (ld->ops->flush_buffer)
846 ld->ops->flush_buffer(tty);
847 tty_driver_flush_buffer(tty);
848 if ((test_bit(TTY_DO_WRITE_WAKEUP, &tty->flags)) &&
849 ld->ops->write_wakeup)
850 ld->ops->write_wakeup(tty);
851 if (ld->ops->hangup)
852 ld->ops->hangup(tty);
853 tty_ldisc_deref(ld);
854 }
855 /*
856 * FIXME: Once we trust the LDISC code better we can wait here for
857 * ldisc completion and fix the driver call race
858 */
859 wake_up_interruptible_poll(&tty->write_wait, POLLOUT);
860 wake_up_interruptible_poll(&tty->read_wait, POLLIN);
861 /*
862 * Shutdown the current line discipline, and reset it to
Alan Cox638b9642010-02-08 10:09:26 +0000863 * N_TTY if need be.
864 *
865 * Avoid racing set_ldisc or tty_ldisc_release
Alan Coxc65c9bc2009-06-11 12:50:12 +0100866 */
Alan Cox638b9642010-02-08 10:09:26 +0000867 mutex_lock(&tty->ldisc_mutex);
Arnd Bergmann60af22d2010-06-01 22:53:06 +0200868
Alan Cox638b9642010-02-08 10:09:26 +0000869 /* At this point we have a closed ldisc and we want to
870 reopen it. We could defer this to the next open but
871 it means auditing a lot of other paths so this is
872 a FIXME */
Peter Hurley76bc35e2013-03-11 16:44:26 -0400873 if (tty_ldisc_hangup_halt(tty)) {
Alan Cox638b9642010-02-08 10:09:26 +0000874 if (reset == 0) {
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200875
Alan Coxadc8d742012-07-14 15:31:47 +0100876 if (!tty_ldisc_reinit(tty, tty->termios.c_line))
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200877 err = tty_ldisc_open(tty, tty->ldisc);
878 else
879 err = 1;
Alan Coxc8d50042009-07-16 16:05:08 +0100880 }
Alan Cox638b9642010-02-08 10:09:26 +0000881 /* If the re-open fails or we reset then go to N_TTY. The
882 N_TTY open cannot fail */
883 if (reset || err) {
Philippe Rétornaz1c95ba12010-10-27 17:13:21 +0200884 BUG_ON(tty_ldisc_reinit(tty, N_TTY));
Alan Cox638b9642010-02-08 10:09:26 +0000885 WARN_ON(tty_ldisc_open(tty, tty->ldisc));
886 }
887 tty_ldisc_enable(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100888 }
Alan Cox638b9642010-02-08 10:09:26 +0000889 mutex_unlock(&tty->ldisc_mutex);
890 if (reset)
891 tty_reset_termios(tty);
Alan Coxc65c9bc2009-06-11 12:50:12 +0100892}
Alan Cox01e1abb2008-07-22 11:16:55 +0100893
894/**
895 * tty_ldisc_setup - open line discipline
896 * @tty: tty being shut down
897 * @o_tty: pair tty for pty/tty pairs
898 *
899 * Called during the initial open of a tty/pty pair in order to set up the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100900 * line disciplines and bind them to the tty. This has no locking issues
901 * as the device isn't yet active.
Alan Cox01e1abb2008-07-22 11:16:55 +0100902 */
903
904int tty_ldisc_setup(struct tty_struct *tty, struct tty_struct *o_tty)
905{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100906 struct tty_ldisc *ld = tty->ldisc;
Alan Cox01e1abb2008-07-22 11:16:55 +0100907 int retval;
908
Alan Coxc65c9bc2009-06-11 12:50:12 +0100909 retval = tty_ldisc_open(tty, ld);
910 if (retval)
911 return retval;
912
913 if (o_tty) {
914 retval = tty_ldisc_open(o_tty, o_tty->ldisc);
Alan Cox01e1abb2008-07-22 11:16:55 +0100915 if (retval) {
Alan Coxc65c9bc2009-06-11 12:50:12 +0100916 tty_ldisc_close(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100917 return retval;
918 }
919 tty_ldisc_enable(o_tty);
920 }
921 tty_ldisc_enable(tty);
922 return 0;
923}
Alan Cox89c8d912012-08-08 16:30:13 +0100924
925static void tty_ldisc_kill(struct tty_struct *tty)
926{
927 mutex_lock(&tty->ldisc_mutex);
928 /*
929 * Now kill off the ldisc
930 */
931 tty_ldisc_close(tty, tty->ldisc);
932 tty_ldisc_put(tty->ldisc);
933 /* Force an oops if we mess this up */
934 tty->ldisc = NULL;
935
936 /* Ensure the next open requests the N_TTY ldisc */
937 tty_set_termios_ldisc(tty, N_TTY);
938 mutex_unlock(&tty->ldisc_mutex);
939}
940
Alan Cox01e1abb2008-07-22 11:16:55 +0100941/**
942 * tty_ldisc_release - release line discipline
943 * @tty: tty being shut down
944 * @o_tty: pair tty for pty/tty pairs
945 *
Alan Cox852e99d2009-06-11 12:51:41 +0100946 * Called during the final close of a tty/pty pair in order to shut down
947 * the line discpline layer. On exit the ldisc assigned is N_TTY and the
Alan Coxc65c9bc2009-06-11 12:50:12 +0100948 * ldisc has not been opened.
Alan Cox01e1abb2008-07-22 11:16:55 +0100949 */
950
951void tty_ldisc_release(struct tty_struct *tty, struct tty_struct *o_tty)
952{
Alan Cox01e1abb2008-07-22 11:16:55 +0100953 /*
954 * Prevent flush_to_ldisc() from rescheduling the work for later. Then
955 * kill any delayed work. As this is the final close it does not
956 * race with the set_ldisc code path.
957 */
Alan Cox01e1abb2008-07-22 11:16:55 +0100958
Peter Hurley4f98d462013-03-11 16:44:34 -0400959 tty_ldisc_halt(tty, o_tty, MAX_SCHEDULE_TIMEOUT);
Sebastian Andrzej Siewior852e4a82012-12-25 23:02:48 +0100960 tty_ldisc_flush_works(tty);
Peter Hurleyf4cf7a32013-03-11 16:44:29 -0400961 if (o_tty)
Sebastian Andrzej Siewior852e4a82012-12-25 23:02:48 +0100962 tty_ldisc_flush_works(o_tty);
963
964 tty_lock_pair(tty, o_tty);
Alan Cox6d31a882012-07-14 15:31:27 +0100965 /* This will need doing differently if we need to lock */
Alan Cox89c8d912012-08-08 16:30:13 +0100966 tty_ldisc_kill(tty);
Alan Cox89c8d912012-08-08 16:30:13 +0100967 if (o_tty)
968 tty_ldisc_kill(o_tty);
969
970 tty_unlock_pair(tty, o_tty);
Alan Coxaef29bc2009-06-29 15:21:47 +0100971 /* And the memory resources remaining (buffers, termios) will be
972 disposed of when the kref hits zero */
Alan Cox01e1abb2008-07-22 11:16:55 +0100973}
974
975/**
976 * tty_ldisc_init - ldisc setup for new tty
977 * @tty: tty being allocated
978 *
979 * Set up the line discipline objects for a newly allocated tty. Note that
980 * the tty structure is not completely set up when this call is made.
981 */
982
983void tty_ldisc_init(struct tty_struct *tty)
984{
Alan Coxc65c9bc2009-06-11 12:50:12 +0100985 struct tty_ldisc *ld = tty_ldisc_get(N_TTY);
986 if (IS_ERR(ld))
Alan Cox01e1abb2008-07-22 11:16:55 +0100987 panic("n_tty: init_tty");
Alan Coxc65c9bc2009-06-11 12:50:12 +0100988 tty_ldisc_assign(tty, ld);
Alan Cox01e1abb2008-07-22 11:16:55 +0100989}
990
Jiri Slaby67166712011-03-23 10:48:35 +0100991/**
992 * tty_ldisc_init - ldisc cleanup for new tty
993 * @tty: tty that was allocated recently
994 *
995 * The tty structure must not becompletely set up (tty_ldisc_setup) when
996 * this call is made.
997 */
998void tty_ldisc_deinit(struct tty_struct *tty)
999{
1000 put_ldisc(tty->ldisc);
1001 tty_ldisc_assign(tty, NULL);
1002}
1003
Alan Cox01e1abb2008-07-22 11:16:55 +01001004void tty_ldisc_begin(void)
1005{
1006 /* Setup the default TTY line discipline. */
1007 (void) tty_register_ldisc(N_TTY, &tty_ldisc_N_TTY);
1008}