blob: 91e326ffe7db826054c2607c1ea2688ed047bb81 [file] [log] [blame]
Alan Coxe0495732008-10-13 10:36:58 +01001/*
2 * Tty buffer allocation management
3 */
4
5#include <linux/types.h>
6#include <linux/errno.h>
7#include <linux/tty.h>
8#include <linux/tty_driver.h>
9#include <linux/tty_flip.h>
10#include <linux/timer.h>
11#include <linux/string.h>
12#include <linux/slab.h>
13#include <linux/sched.h>
14#include <linux/init.h>
15#include <linux/wait.h>
16#include <linux/bitops.h>
17#include <linux/delay.h>
18#include <linux/module.h>
19
20/**
21 * tty_buffer_free_all - free buffers used by a tty
22 * @tty: tty to free from
23 *
24 * Remove all the buffers pending on a tty whether queued with data
25 * or in the free ring. Must be called when the tty is no longer in use
26 *
27 * Locking: none
28 */
29
30void tty_buffer_free_all(struct tty_struct *tty)
31{
32 struct tty_buffer *thead;
33 while ((thead = tty->buf.head) != NULL) {
34 tty->buf.head = thead->next;
35 kfree(thead);
36 }
37 while ((thead = tty->buf.free) != NULL) {
38 tty->buf.free = thead->next;
39 kfree(thead);
40 }
41 tty->buf.tail = NULL;
42 tty->buf.memory_used = 0;
43}
44
45/**
46 * tty_buffer_alloc - allocate a tty buffer
47 * @tty: tty device
48 * @size: desired size (characters)
49 *
50 * Allocate a new tty buffer to hold the desired number of characters.
51 * Return NULL if out of memory or the allocation would exceed the
52 * per device queue
53 *
54 * Locking: Caller must hold tty->buf.lock
55 */
56
57static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
58{
59 struct tty_buffer *p;
60
61 if (tty->buf.memory_used + size > 65536)
62 return NULL;
63 p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
64 if (p == NULL)
65 return NULL;
66 p->used = 0;
67 p->size = size;
68 p->next = NULL;
69 p->commit = 0;
70 p->read = 0;
71 p->char_buf_ptr = (char *)(p->data);
72 p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
73 tty->buf.memory_used += size;
74 return p;
75}
76
77/**
78 * tty_buffer_free - free a tty buffer
79 * @tty: tty owning the buffer
80 * @b: the buffer to free
81 *
82 * Free a tty buffer, or add it to the free list according to our
83 * internal strategy
84 *
85 * Locking: Caller must hold tty->buf.lock
86 */
87
88static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
89{
90 /* Dumb strategy for now - should keep some stats */
91 tty->buf.memory_used -= b->size;
92 WARN_ON(tty->buf.memory_used < 0);
93
94 if (b->size >= 512)
95 kfree(b);
96 else {
97 b->next = tty->buf.free;
98 tty->buf.free = b;
99 }
100}
101
102/**
103 * __tty_buffer_flush - flush full tty buffers
104 * @tty: tty to flush
105 *
106 * flush all the buffers containing receive data. Caller must
107 * hold the buffer lock and must have ensured no parallel flush to
108 * ldisc is running.
109 *
110 * Locking: Caller must hold tty->buf.lock
111 */
112
113static void __tty_buffer_flush(struct tty_struct *tty)
114{
115 struct tty_buffer *thead;
116
117 while ((thead = tty->buf.head) != NULL) {
118 tty->buf.head = thead->next;
119 tty_buffer_free(tty, thead);
120 }
121 tty->buf.tail = NULL;
122}
123
124/**
125 * tty_buffer_flush - flush full tty buffers
126 * @tty: tty to flush
127 *
128 * flush all the buffers containing receive data. If the buffer is
129 * being processed by flush_to_ldisc then we defer the processing
130 * to that function
131 *
132 * Locking: none
133 */
134
135void tty_buffer_flush(struct tty_struct *tty)
136{
137 unsigned long flags;
138 spin_lock_irqsave(&tty->buf.lock, flags);
139
140 /* If the data is being pushed to the tty layer then we can't
141 process it here. Instead set a flag and the flush_to_ldisc
142 path will process the flush request before it exits */
143 if (test_bit(TTY_FLUSHING, &tty->flags)) {
144 set_bit(TTY_FLUSHPENDING, &tty->flags);
145 spin_unlock_irqrestore(&tty->buf.lock, flags);
146 wait_event(tty->read_wait,
147 test_bit(TTY_FLUSHPENDING, &tty->flags) == 0);
148 return;
149 } else
150 __tty_buffer_flush(tty);
151 spin_unlock_irqrestore(&tty->buf.lock, flags);
152}
153
154/**
155 * tty_buffer_find - find a free tty buffer
156 * @tty: tty owning the buffer
157 * @size: characters wanted
158 *
159 * Locate an existing suitable tty buffer or if we are lacking one then
160 * allocate a new one. We round our buffers off in 256 character chunks
161 * to get better allocation behaviour.
162 *
163 * Locking: Caller must hold tty->buf.lock
164 */
165
166static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
167{
168 struct tty_buffer **tbh = &tty->buf.free;
169 while ((*tbh) != NULL) {
170 struct tty_buffer *t = *tbh;
171 if (t->size >= size) {
172 *tbh = t->next;
173 t->next = NULL;
174 t->used = 0;
175 t->commit = 0;
176 t->read = 0;
177 tty->buf.memory_used += t->size;
178 return t;
179 }
180 tbh = &((*tbh)->next);
181 }
182 /* Round the buffer size out */
183 size = (size + 0xFF) & ~0xFF;
184 return tty_buffer_alloc(tty, size);
185 /* Should possibly check if this fails for the largest buffer we
186 have queued and recycle that ? */
187}
Alan Coxe0495732008-10-13 10:36:58 +0100188/**
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000189 * __tty_buffer_request_room - grow tty buffer if needed
Alan Coxe0495732008-10-13 10:36:58 +0100190 * @tty: tty structure
191 * @size: size desired
192 *
193 * Make at least size bytes of linear space available for the tty
194 * buffer. If we fail return the size we managed to find.
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000195 * Locking: Caller must hold tty->buf.lock
Alan Coxe0495732008-10-13 10:36:58 +0100196 */
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000197static int __tty_buffer_request_room(struct tty_struct *tty, size_t size)
Alan Coxe0495732008-10-13 10:36:58 +0100198{
199 struct tty_buffer *b, *n;
200 int left;
Alan Coxe0495732008-10-13 10:36:58 +0100201 /* OPTIMISATION: We could keep a per tty "zero" sized buffer to
202 remove this conditional if its worth it. This would be invisible
203 to the callers */
204 if ((b = tty->buf.tail) != NULL)
205 left = b->size - b->used;
206 else
207 left = 0;
208
209 if (left < size) {
210 /* This is the slow path - looking for new buffers to use */
211 if ((n = tty_buffer_find(tty, size)) != NULL) {
212 if (b != NULL) {
213 b->next = n;
214 b->commit = b->used;
215 } else
216 tty->buf.head = n;
217 tty->buf.tail = n;
218 } else
219 size = left;
220 }
221
Alan Coxe0495732008-10-13 10:36:58 +0100222 return size;
223}
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000224
225
226/**
227 * tty_buffer_request_room - grow tty buffer if needed
228 * @tty: tty structure
229 * @size: size desired
230 *
231 * Make at least size bytes of linear space available for the tty
232 * buffer. If we fail return the size we managed to find.
233 *
234 * Locking: Takes tty->buf.lock
235 */
236int tty_buffer_request_room(struct tty_struct *tty, size_t size)
237{
238 unsigned long flags;
239 int length;
240
241 spin_lock_irqsave(&tty->buf.lock, flags);
242 length = __tty_buffer_request_room(tty, size);
243 spin_unlock_irqrestore(&tty->buf.lock, flags);
244 return length;
245}
Alan Coxe0495732008-10-13 10:36:58 +0100246EXPORT_SYMBOL_GPL(tty_buffer_request_room);
247
248/**
Alan Cox2832fc12010-02-18 16:43:54 +0000249 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
Alan Coxe0495732008-10-13 10:36:58 +0100250 * @tty: tty structure
251 * @chars: characters
Alan Cox2832fc12010-02-18 16:43:54 +0000252 * @flag: flag value for each character
Alan Coxe0495732008-10-13 10:36:58 +0100253 * @size: size
254 *
255 * Queue a series of bytes to the tty buffering. All the characters
Johan Hovoldccc5ca82010-05-07 19:58:32 +0200256 * passed are marked with the supplied flag. Returns the number added.
Alan Coxe0495732008-10-13 10:36:58 +0100257 *
258 * Locking: Called functions may take tty->buf.lock
259 */
260
Alan Cox2832fc12010-02-18 16:43:54 +0000261int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
262 const unsigned char *chars, char flag, size_t size)
Alan Coxe0495732008-10-13 10:36:58 +0100263{
264 int copied = 0;
265 do {
Fang Wenqid4bee0a2010-03-09 18:54:28 +0800266 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000267 int space;
268 unsigned long flags;
269 struct tty_buffer *tb;
270
271 spin_lock_irqsave(&tty->buf.lock, flags);
272 space = __tty_buffer_request_room(tty, goal);
273 tb = tty->buf.tail;
Alan Coxe0495732008-10-13 10:36:58 +0100274 /* If there is no space then tb may be NULL */
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000275 if (unlikely(space == 0)) {
276 spin_unlock_irqrestore(&tty->buf.lock, flags);
Alan Coxe0495732008-10-13 10:36:58 +0100277 break;
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000278 }
Alan Coxe0495732008-10-13 10:36:58 +0100279 memcpy(tb->char_buf_ptr + tb->used, chars, space);
Alan Cox2832fc12010-02-18 16:43:54 +0000280 memset(tb->flag_buf_ptr + tb->used, flag, space);
Alan Coxe0495732008-10-13 10:36:58 +0100281 tb->used += space;
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000282 spin_unlock_irqrestore(&tty->buf.lock, flags);
Alan Coxe0495732008-10-13 10:36:58 +0100283 copied += space;
284 chars += space;
285 /* There is a small chance that we need to split the data over
286 several buffers. If this is the case we must loop */
287 } while (unlikely(size > copied));
288 return copied;
289}
Alan Cox2832fc12010-02-18 16:43:54 +0000290EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
Alan Coxe0495732008-10-13 10:36:58 +0100291
292/**
293 * tty_insert_flip_string_flags - Add characters to the tty buffer
294 * @tty: tty structure
295 * @chars: characters
296 * @flags: flag bytes
297 * @size: size
298 *
299 * Queue a series of bytes to the tty buffering. For each character
300 * the flags array indicates the status of the character. Returns the
301 * number added.
302 *
303 * Locking: Called functions may take tty->buf.lock
304 */
305
306int tty_insert_flip_string_flags(struct tty_struct *tty,
307 const unsigned char *chars, const char *flags, size_t size)
308{
309 int copied = 0;
310 do {
Fang Wenqid4bee0a2010-03-09 18:54:28 +0800311 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000312 int space;
313 unsigned long __flags;
314 struct tty_buffer *tb;
315
316 spin_lock_irqsave(&tty->buf.lock, __flags);
317 space = __tty_buffer_request_room(tty, goal);
318 tb = tty->buf.tail;
Alan Coxe0495732008-10-13 10:36:58 +0100319 /* If there is no space then tb may be NULL */
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000320 if (unlikely(space == 0)) {
321 spin_unlock_irqrestore(&tty->buf.lock, __flags);
Alan Coxe0495732008-10-13 10:36:58 +0100322 break;
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000323 }
Alan Coxe0495732008-10-13 10:36:58 +0100324 memcpy(tb->char_buf_ptr + tb->used, chars, space);
325 memcpy(tb->flag_buf_ptr + tb->used, flags, space);
326 tb->used += space;
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000327 spin_unlock_irqrestore(&tty->buf.lock, __flags);
Alan Coxe0495732008-10-13 10:36:58 +0100328 copied += space;
329 chars += space;
330 flags += space;
331 /* There is a small chance that we need to split the data over
332 several buffers. If this is the case we must loop */
333 } while (unlikely(size > copied));
334 return copied;
335}
336EXPORT_SYMBOL(tty_insert_flip_string_flags);
337
338/**
339 * tty_schedule_flip - push characters to ldisc
340 * @tty: tty to push from
341 *
342 * Takes any pending buffers and transfers their ownership to the
343 * ldisc side of the queue. It then schedules those characters for
344 * processing by the line discipline.
345 *
346 * Locking: Takes tty->buf.lock
347 */
348
349void tty_schedule_flip(struct tty_struct *tty)
350{
351 unsigned long flags;
352 spin_lock_irqsave(&tty->buf.lock, flags);
353 if (tty->buf.tail != NULL)
354 tty->buf.tail->commit = tty->buf.tail->used;
355 spin_unlock_irqrestore(&tty->buf.lock, flags);
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700356 schedule_work(&tty->buf.work);
Alan Coxe0495732008-10-13 10:36:58 +0100357}
358EXPORT_SYMBOL(tty_schedule_flip);
359
360/**
361 * tty_prepare_flip_string - make room for characters
362 * @tty: tty
363 * @chars: return pointer for character write area
364 * @size: desired size
365 *
366 * Prepare a block of space in the buffer for data. Returns the length
367 * available and buffer pointer to the space which is now allocated and
368 * accounted for as ready for normal characters. This is used for drivers
369 * that need their own block copy routines into the buffer. There is no
370 * guarantee the buffer is a DMA target!
371 *
372 * Locking: May call functions taking tty->buf.lock
373 */
374
375int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
376 size_t size)
377{
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000378 int space;
379 unsigned long flags;
380 struct tty_buffer *tb;
381
382 spin_lock_irqsave(&tty->buf.lock, flags);
383 space = __tty_buffer_request_room(tty, size);
384
385 tb = tty->buf.tail;
Alan Coxe0495732008-10-13 10:36:58 +0100386 if (likely(space)) {
Alan Coxe0495732008-10-13 10:36:58 +0100387 *chars = tb->char_buf_ptr + tb->used;
388 memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
389 tb->used += space;
390 }
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000391 spin_unlock_irqrestore(&tty->buf.lock, flags);
Alan Coxe0495732008-10-13 10:36:58 +0100392 return space;
393}
394EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
395
396/**
397 * tty_prepare_flip_string_flags - make room for characters
398 * @tty: tty
399 * @chars: return pointer for character write area
400 * @flags: return pointer for status flag write area
401 * @size: desired size
402 *
403 * Prepare a block of space in the buffer for data. Returns the length
404 * available and buffer pointer to the space which is now allocated and
405 * accounted for as ready for characters. This is used for drivers
406 * that need their own block copy routines into the buffer. There is no
407 * guarantee the buffer is a DMA target!
408 *
409 * Locking: May call functions taking tty->buf.lock
410 */
411
412int tty_prepare_flip_string_flags(struct tty_struct *tty,
413 unsigned char **chars, char **flags, size_t size)
414{
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000415 int space;
416 unsigned long __flags;
417 struct tty_buffer *tb;
418
419 spin_lock_irqsave(&tty->buf.lock, __flags);
420 space = __tty_buffer_request_room(tty, size);
421
422 tb = tty->buf.tail;
Alan Coxe0495732008-10-13 10:36:58 +0100423 if (likely(space)) {
Alan Coxe0495732008-10-13 10:36:58 +0100424 *chars = tb->char_buf_ptr + tb->used;
425 *flags = tb->flag_buf_ptr + tb->used;
426 tb->used += space;
427 }
Xiaobing Tuc56a00a2012-03-16 03:00:26 +0000428 spin_unlock_irqrestore(&tty->buf.lock, __flags);
Alan Coxe0495732008-10-13 10:36:58 +0100429 return space;
430}
431EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
432
433
434
435/**
436 * flush_to_ldisc
437 * @work: tty structure passed from work queue.
438 *
439 * This routine is called out of the software interrupt to flush data
440 * from the buffer chain to the line discipline.
441 *
442 * Locking: holds tty->buf.lock to guard buffer list. Drops the lock
443 * while invoking the line discipline receive_buf method. The
444 * receive_buf method is single threaded for each tty instance.
445 */
446
447static void flush_to_ldisc(struct work_struct *work)
448{
449 struct tty_struct *tty =
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700450 container_of(work, struct tty_struct, buf.work);
Alan Coxe0495732008-10-13 10:36:58 +0100451 unsigned long flags;
452 struct tty_ldisc *disc;
Alan Coxe0495732008-10-13 10:36:58 +0100453
454 disc = tty_ldisc_ref(tty);
455 if (disc == NULL) /* !TTY_LDISC */
456 return;
457
458 spin_lock_irqsave(&tty->buf.lock, flags);
Linus Torvalds45242002009-10-14 08:59:49 -0700459
460 if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {
Linus Torvalds81de9162011-06-08 07:46:30 -0700461 struct tty_buffer *head;
Linus Torvalds45242002009-10-14 08:59:49 -0700462 while ((head = tty->buf.head) != NULL) {
463 int count;
464 char *char_buf;
465 unsigned char *flag_buf;
466
467 count = head->commit - head->read;
Alan Coxe0495732008-10-13 10:36:58 +0100468 if (!count) {
469 if (head->next == NULL)
470 break;
Linus Torvalds45242002009-10-14 08:59:49 -0700471 tty->buf.head = head->next;
472 tty_buffer_free(tty, head);
Alan Coxe0495732008-10-13 10:36:58 +0100473 continue;
474 }
475 /* Ldisc or user is trying to flush the buffers
476 we are feeding to the ldisc, stop feeding the
477 line discipline as we want to empty the queue */
478 if (test_bit(TTY_FLUSHPENDING, &tty->flags))
479 break;
Linus Torvalds81de9162011-06-08 07:46:30 -0700480 if (!tty->receive_room)
Linus Torvalds55db4c62011-06-04 06:33:24 +0900481 break;
482 if (count > tty->receive_room)
483 count = tty->receive_room;
Alan Coxe0495732008-10-13 10:36:58 +0100484 char_buf = head->char_buf_ptr + head->read;
485 flag_buf = head->flag_buf_ptr + head->read;
Linus Torvalds55db4c62011-06-04 06:33:24 +0900486 head->read += count;
Alan Coxe0495732008-10-13 10:36:58 +0100487 spin_unlock_irqrestore(&tty->buf.lock, flags);
Linus Torvalds55db4c62011-06-04 06:33:24 +0900488 disc->ops->receive_buf(tty, char_buf,
Alan Coxe0495732008-10-13 10:36:58 +0100489 flag_buf, count);
490 spin_lock_irqsave(&tty->buf.lock, flags);
491 }
Linus Torvalds45242002009-10-14 08:59:49 -0700492 clear_bit(TTY_FLUSHING, &tty->flags);
Alan Coxe0495732008-10-13 10:36:58 +0100493 }
Linus Torvalds45242002009-10-14 08:59:49 -0700494
Alan Coxe0495732008-10-13 10:36:58 +0100495 /* We may have a deferred request to flush the input buffer,
496 if so pull the chain under the lock and empty the queue */
497 if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
498 __tty_buffer_flush(tty);
499 clear_bit(TTY_FLUSHPENDING, &tty->flags);
500 wake_up(&tty->read_wait);
501 }
Alan Coxe0495732008-10-13 10:36:58 +0100502 spin_unlock_irqrestore(&tty->buf.lock, flags);
503
504 tty_ldisc_deref(disc);
505}
506
507/**
OGAWA Hirofumie043e422009-07-29 12:15:56 -0700508 * tty_flush_to_ldisc
509 * @tty: tty to push
510 *
511 * Push the terminal flip buffers to the line discipline.
512 *
513 * Must not be called from IRQ context.
514 */
515void tty_flush_to_ldisc(struct tty_struct *tty)
516{
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700517 flush_work(&tty->buf.work);
OGAWA Hirofumie043e422009-07-29 12:15:56 -0700518}
519
520/**
Alan Coxe0495732008-10-13 10:36:58 +0100521 * tty_flip_buffer_push - terminal
522 * @tty: tty to push
523 *
524 * Queue a push of the terminal flip buffers to the line discipline. This
525 * function must not be called from IRQ context if tty->low_latency is set.
526 *
527 * In the event of the queue being busy for flipping the work will be
528 * held off and retried later.
529 *
530 * Locking: tty buffer lock. Driver locks in low latency mode.
531 */
532
533void tty_flip_buffer_push(struct tty_struct *tty)
534{
535 unsigned long flags;
536 spin_lock_irqsave(&tty->buf.lock, flags);
537 if (tty->buf.tail != NULL)
538 tty->buf.tail->commit = tty->buf.tail->used;
539 spin_unlock_irqrestore(&tty->buf.lock, flags);
540
541 if (tty->low_latency)
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700542 flush_to_ldisc(&tty->buf.work);
Alan Coxe0495732008-10-13 10:36:58 +0100543 else
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700544 schedule_work(&tty->buf.work);
Alan Coxe0495732008-10-13 10:36:58 +0100545}
546EXPORT_SYMBOL(tty_flip_buffer_push);
547
548/**
549 * tty_buffer_init - prepare a tty buffer structure
550 * @tty: tty to initialise
551 *
552 * Set up the initial state of the buffer management for a tty device.
553 * Must be called before the other tty buffer functions are used.
554 *
555 * Locking: none
556 */
557
558void tty_buffer_init(struct tty_struct *tty)
559{
560 spin_lock_init(&tty->buf.lock);
561 tty->buf.head = NULL;
562 tty->buf.tail = NULL;
563 tty->buf.free = NULL;
564 tty->buf.memory_used = 0;
Linus Torvaldsf23eb2b2011-03-22 16:17:32 -0700565 INIT_WORK(&tty->buf.work, flush_to_ldisc);
Alan Coxe0495732008-10-13 10:36:58 +0100566}
567