Commit | Line | Data |
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e0495736 AC |
1 | /* |
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 | ||
30 | void 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 | ||
57 | static 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 | ||
88 | static 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 | ||
113 | static 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 | ||
135 | void 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 | ||
166 | static 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 | } | |
188 | ||
189 | /** | |
190 | * tty_buffer_request_room - grow tty buffer if needed | |
191 | * @tty: tty structure | |
192 | * @size: size desired | |
193 | * | |
194 | * Make at least size bytes of linear space available for the tty | |
195 | * buffer. If we fail return the size we managed to find. | |
196 | * | |
197 | * Locking: Takes tty->buf.lock | |
198 | */ | |
199 | int tty_buffer_request_room(struct tty_struct *tty, size_t size) | |
200 | { | |
201 | struct tty_buffer *b, *n; | |
202 | int left; | |
203 | unsigned long flags; | |
204 | ||
205 | spin_lock_irqsave(&tty->buf.lock, flags); | |
206 | ||
207 | /* OPTIMISATION: We could keep a per tty "zero" sized buffer to | |
208 | remove this conditional if its worth it. This would be invisible | |
209 | to the callers */ | |
210 | if ((b = tty->buf.tail) != NULL) | |
211 | left = b->size - b->used; | |
212 | else | |
213 | left = 0; | |
214 | ||
215 | if (left < size) { | |
216 | /* This is the slow path - looking for new buffers to use */ | |
217 | if ((n = tty_buffer_find(tty, size)) != NULL) { | |
218 | if (b != NULL) { | |
219 | b->next = n; | |
220 | b->commit = b->used; | |
221 | } else | |
222 | tty->buf.head = n; | |
223 | tty->buf.tail = n; | |
224 | } else | |
225 | size = left; | |
226 | } | |
227 | ||
228 | spin_unlock_irqrestore(&tty->buf.lock, flags); | |
229 | return size; | |
230 | } | |
231 | EXPORT_SYMBOL_GPL(tty_buffer_request_room); | |
232 | ||
233 | /** | |
234 | * tty_insert_flip_string - Add characters to the tty buffer | |
235 | * @tty: tty structure | |
236 | * @chars: characters | |
237 | * @size: size | |
238 | * | |
239 | * Queue a series of bytes to the tty buffering. All the characters | |
240 | * passed are marked as without error. Returns the number added. | |
241 | * | |
242 | * Locking: Called functions may take tty->buf.lock | |
243 | */ | |
244 | ||
245 | int tty_insert_flip_string(struct tty_struct *tty, const unsigned char *chars, | |
246 | size_t size) | |
247 | { | |
248 | int copied = 0; | |
249 | do { | |
250 | int space = tty_buffer_request_room(tty, size - copied); | |
251 | struct tty_buffer *tb = tty->buf.tail; | |
252 | /* If there is no space then tb may be NULL */ | |
253 | if (unlikely(space == 0)) | |
254 | break; | |
255 | memcpy(tb->char_buf_ptr + tb->used, chars, space); | |
256 | memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space); | |
257 | tb->used += space; | |
258 | copied += space; | |
259 | chars += space; | |
260 | /* There is a small chance that we need to split the data over | |
261 | several buffers. If this is the case we must loop */ | |
262 | } while (unlikely(size > copied)); | |
263 | return copied; | |
264 | } | |
265 | EXPORT_SYMBOL(tty_insert_flip_string); | |
266 | ||
267 | /** | |
268 | * tty_insert_flip_string_flags - Add characters to the tty buffer | |
269 | * @tty: tty structure | |
270 | * @chars: characters | |
271 | * @flags: flag bytes | |
272 | * @size: size | |
273 | * | |
274 | * Queue a series of bytes to the tty buffering. For each character | |
275 | * the flags array indicates the status of the character. Returns the | |
276 | * number added. | |
277 | * | |
278 | * Locking: Called functions may take tty->buf.lock | |
279 | */ | |
280 | ||
281 | int tty_insert_flip_string_flags(struct tty_struct *tty, | |
282 | const unsigned char *chars, const char *flags, size_t size) | |
283 | { | |
284 | int copied = 0; | |
285 | do { | |
286 | int space = tty_buffer_request_room(tty, size - copied); | |
287 | struct tty_buffer *tb = tty->buf.tail; | |
288 | /* If there is no space then tb may be NULL */ | |
289 | if (unlikely(space == 0)) | |
290 | break; | |
291 | memcpy(tb->char_buf_ptr + tb->used, chars, space); | |
292 | memcpy(tb->flag_buf_ptr + tb->used, flags, space); | |
293 | tb->used += space; | |
294 | copied += space; | |
295 | chars += space; | |
296 | flags += space; | |
297 | /* There is a small chance that we need to split the data over | |
298 | several buffers. If this is the case we must loop */ | |
299 | } while (unlikely(size > copied)); | |
300 | return copied; | |
301 | } | |
302 | EXPORT_SYMBOL(tty_insert_flip_string_flags); | |
303 | ||
304 | /** | |
305 | * tty_schedule_flip - push characters to ldisc | |
306 | * @tty: tty to push from | |
307 | * | |
308 | * Takes any pending buffers and transfers their ownership to the | |
309 | * ldisc side of the queue. It then schedules those characters for | |
310 | * processing by the line discipline. | |
311 | * | |
312 | * Locking: Takes tty->buf.lock | |
313 | */ | |
314 | ||
315 | void tty_schedule_flip(struct tty_struct *tty) | |
316 | { | |
317 | unsigned long flags; | |
318 | spin_lock_irqsave(&tty->buf.lock, flags); | |
319 | if (tty->buf.tail != NULL) | |
320 | tty->buf.tail->commit = tty->buf.tail->used; | |
321 | spin_unlock_irqrestore(&tty->buf.lock, flags); | |
322 | schedule_delayed_work(&tty->buf.work, 1); | |
323 | } | |
324 | EXPORT_SYMBOL(tty_schedule_flip); | |
325 | ||
326 | /** | |
327 | * tty_prepare_flip_string - make room for characters | |
328 | * @tty: tty | |
329 | * @chars: return pointer for character write area | |
330 | * @size: desired size | |
331 | * | |
332 | * Prepare a block of space in the buffer for data. Returns the length | |
333 | * available and buffer pointer to the space which is now allocated and | |
334 | * accounted for as ready for normal characters. This is used for drivers | |
335 | * that need their own block copy routines into the buffer. There is no | |
336 | * guarantee the buffer is a DMA target! | |
337 | * | |
338 | * Locking: May call functions taking tty->buf.lock | |
339 | */ | |
340 | ||
341 | int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars, | |
342 | size_t size) | |
343 | { | |
344 | int space = tty_buffer_request_room(tty, size); | |
345 | if (likely(space)) { | |
346 | struct tty_buffer *tb = tty->buf.tail; | |
347 | *chars = tb->char_buf_ptr + tb->used; | |
348 | memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space); | |
349 | tb->used += space; | |
350 | } | |
351 | return space; | |
352 | } | |
353 | EXPORT_SYMBOL_GPL(tty_prepare_flip_string); | |
354 | ||
355 | /** | |
356 | * tty_prepare_flip_string_flags - make room for characters | |
357 | * @tty: tty | |
358 | * @chars: return pointer for character write area | |
359 | * @flags: return pointer for status flag write area | |
360 | * @size: desired size | |
361 | * | |
362 | * Prepare a block of space in the buffer for data. Returns the length | |
363 | * available and buffer pointer to the space which is now allocated and | |
364 | * accounted for as ready for characters. This is used for drivers | |
365 | * that need their own block copy routines into the buffer. There is no | |
366 | * guarantee the buffer is a DMA target! | |
367 | * | |
368 | * Locking: May call functions taking tty->buf.lock | |
369 | */ | |
370 | ||
371 | int tty_prepare_flip_string_flags(struct tty_struct *tty, | |
372 | unsigned char **chars, char **flags, size_t size) | |
373 | { | |
374 | int space = tty_buffer_request_room(tty, size); | |
375 | if (likely(space)) { | |
376 | struct tty_buffer *tb = tty->buf.tail; | |
377 | *chars = tb->char_buf_ptr + tb->used; | |
378 | *flags = tb->flag_buf_ptr + tb->used; | |
379 | tb->used += space; | |
380 | } | |
381 | return space; | |
382 | } | |
383 | EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags); | |
384 | ||
385 | ||
386 | ||
387 | /** | |
388 | * flush_to_ldisc | |
389 | * @work: tty structure passed from work queue. | |
390 | * | |
391 | * This routine is called out of the software interrupt to flush data | |
392 | * from the buffer chain to the line discipline. | |
393 | * | |
394 | * Locking: holds tty->buf.lock to guard buffer list. Drops the lock | |
395 | * while invoking the line discipline receive_buf method. The | |
396 | * receive_buf method is single threaded for each tty instance. | |
397 | */ | |
398 | ||
399 | static void flush_to_ldisc(struct work_struct *work) | |
400 | { | |
401 | struct tty_struct *tty = | |
402 | container_of(work, struct tty_struct, buf.work.work); | |
403 | unsigned long flags; | |
404 | struct tty_ldisc *disc; | |
405 | struct tty_buffer *tbuf, *head; | |
406 | char *char_buf; | |
407 | unsigned char *flag_buf; | |
408 | ||
409 | disc = tty_ldisc_ref(tty); | |
410 | if (disc == NULL) /* !TTY_LDISC */ | |
411 | return; | |
412 | ||
413 | spin_lock_irqsave(&tty->buf.lock, flags); | |
414 | /* So we know a flush is running */ | |
415 | set_bit(TTY_FLUSHING, &tty->flags); | |
416 | head = tty->buf.head; | |
417 | if (head != NULL) { | |
418 | tty->buf.head = NULL; | |
419 | for (;;) { | |
420 | int count = head->commit - head->read; | |
421 | if (!count) { | |
422 | if (head->next == NULL) | |
423 | break; | |
424 | tbuf = head; | |
425 | head = head->next; | |
426 | tty_buffer_free(tty, tbuf); | |
427 | continue; | |
428 | } | |
429 | /* Ldisc or user is trying to flush the buffers | |
430 | we are feeding to the ldisc, stop feeding the | |
431 | line discipline as we want to empty the queue */ | |
432 | if (test_bit(TTY_FLUSHPENDING, &tty->flags)) | |
433 | break; | |
434 | if (!tty->receive_room) { | |
435 | schedule_delayed_work(&tty->buf.work, 1); | |
436 | break; | |
437 | } | |
438 | if (count > tty->receive_room) | |
439 | count = tty->receive_room; | |
440 | char_buf = head->char_buf_ptr + head->read; | |
441 | flag_buf = head->flag_buf_ptr + head->read; | |
442 | head->read += count; | |
443 | spin_unlock_irqrestore(&tty->buf.lock, flags); | |
444 | disc->ops->receive_buf(tty, char_buf, | |
445 | flag_buf, count); | |
446 | spin_lock_irqsave(&tty->buf.lock, flags); | |
447 | } | |
448 | /* Restore the queue head */ | |
449 | tty->buf.head = head; | |
450 | } | |
451 | /* We may have a deferred request to flush the input buffer, | |
452 | if so pull the chain under the lock and empty the queue */ | |
453 | if (test_bit(TTY_FLUSHPENDING, &tty->flags)) { | |
454 | __tty_buffer_flush(tty); | |
455 | clear_bit(TTY_FLUSHPENDING, &tty->flags); | |
456 | wake_up(&tty->read_wait); | |
457 | } | |
458 | clear_bit(TTY_FLUSHING, &tty->flags); | |
459 | spin_unlock_irqrestore(&tty->buf.lock, flags); | |
460 | ||
461 | tty_ldisc_deref(disc); | |
462 | } | |
463 | ||
464 | /** | |
465 | * tty_flip_buffer_push - terminal | |
466 | * @tty: tty to push | |
467 | * | |
468 | * Queue a push of the terminal flip buffers to the line discipline. This | |
469 | * function must not be called from IRQ context if tty->low_latency is set. | |
470 | * | |
471 | * In the event of the queue being busy for flipping the work will be | |
472 | * held off and retried later. | |
473 | * | |
474 | * Locking: tty buffer lock. Driver locks in low latency mode. | |
475 | */ | |
476 | ||
477 | void tty_flip_buffer_push(struct tty_struct *tty) | |
478 | { | |
479 | unsigned long flags; | |
480 | spin_lock_irqsave(&tty->buf.lock, flags); | |
481 | if (tty->buf.tail != NULL) | |
482 | tty->buf.tail->commit = tty->buf.tail->used; | |
483 | spin_unlock_irqrestore(&tty->buf.lock, flags); | |
484 | ||
485 | if (tty->low_latency) | |
486 | flush_to_ldisc(&tty->buf.work.work); | |
487 | else | |
488 | schedule_delayed_work(&tty->buf.work, 1); | |
489 | } | |
490 | EXPORT_SYMBOL(tty_flip_buffer_push); | |
491 | ||
492 | /** | |
493 | * tty_buffer_init - prepare a tty buffer structure | |
494 | * @tty: tty to initialise | |
495 | * | |
496 | * Set up the initial state of the buffer management for a tty device. | |
497 | * Must be called before the other tty buffer functions are used. | |
498 | * | |
499 | * Locking: none | |
500 | */ | |
501 | ||
502 | void tty_buffer_init(struct tty_struct *tty) | |
503 | { | |
504 | spin_lock_init(&tty->buf.lock); | |
505 | tty->buf.head = NULL; | |
506 | tty->buf.tail = NULL; | |
507 | tty->buf.free = NULL; | |
508 | tty->buf.memory_used = 0; | |
509 | INIT_DELAYED_WORK(&tty->buf.work, flush_to_ldisc); | |
510 | } | |
511 |