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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> | |
e0495736 AC |
14 | #include <linux/wait.h> |
15 | #include <linux/bitops.h> | |
16 | #include <linux/delay.h> | |
17 | #include <linux/module.h> | |
593fb1ae | 18 | #include <linux/ratelimit.h> |
e0495736 | 19 | |
1cef50e3 PH |
20 | |
21 | #define MIN_TTYB_SIZE 256 | |
22 | #define TTYB_ALIGN_MASK 255 | |
23 | ||
7bfe0b71 PH |
24 | /* |
25 | * Byte threshold to limit memory consumption for flip buffers. | |
26 | * The actual memory limit is > 2x this amount. | |
27 | */ | |
4d18e6ef | 28 | #define TTYB_DEFAULT_MEM_LIMIT 65536 |
7bfe0b71 | 29 | |
9114fe8c PH |
30 | /* |
31 | * We default to dicing tty buffer allocations to this many characters | |
32 | * in order to avoid multiple page allocations. We know the size of | |
33 | * tty_buffer itself but it must also be taken into account that the | |
34 | * the buffer is 256 byte aligned. See tty_buffer_find for the allocation | |
35 | * logic this must match | |
36 | */ | |
37 | ||
38 | #define TTY_BUFFER_PAGE (((PAGE_SIZE - sizeof(struct tty_buffer)) / 2) & ~0xFF) | |
39 | ||
7bfe0b71 | 40 | |
a7c8d58c PH |
41 | /** |
42 | * tty_buffer_lock_exclusive - gain exclusive access to buffer | |
43 | * tty_buffer_unlock_exclusive - release exclusive access | |
44 | * | |
45 | * @port - tty_port owning the flip buffer | |
46 | * | |
47 | * Guarantees safe use of the line discipline's receive_buf() method by | |
48 | * excluding the buffer work and any pending flush from using the flip | |
49 | * buffer. Data can continue to be added concurrently to the flip buffer | |
50 | * from the driver side. | |
51 | * | |
52 | * On release, the buffer work is restarted if there is data in the | |
53 | * flip buffer | |
54 | */ | |
55 | ||
56 | void tty_buffer_lock_exclusive(struct tty_port *port) | |
57 | { | |
58 | struct tty_bufhead *buf = &port->buf; | |
59 | ||
60 | atomic_inc(&buf->priority); | |
61 | mutex_lock(&buf->lock); | |
62 | } | |
63 | ||
64 | void tty_buffer_unlock_exclusive(struct tty_port *port) | |
65 | { | |
66 | struct tty_bufhead *buf = &port->buf; | |
67 | int restart; | |
68 | ||
69 | restart = buf->head->commit != buf->head->read; | |
70 | ||
71 | atomic_dec(&buf->priority); | |
72 | mutex_unlock(&buf->lock); | |
73 | if (restart) | |
74 | queue_work(system_unbound_wq, &buf->work); | |
75 | } | |
76 | ||
7bfe0b71 PH |
77 | /** |
78 | * tty_buffer_space_avail - return unused buffer space | |
79 | * @port - tty_port owning the flip buffer | |
80 | * | |
81 | * Returns the # of bytes which can be written by the driver without | |
82 | * reaching the buffer limit. | |
83 | * | |
84 | * Note: this does not guarantee that memory is available to write | |
85 | * the returned # of bytes (use tty_prepare_flip_string_xxx() to | |
86 | * pre-allocate if memory guarantee is required). | |
87 | */ | |
88 | ||
89 | int tty_buffer_space_avail(struct tty_port *port) | |
90 | { | |
5dda4ca5 | 91 | int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used); |
7bfe0b71 PH |
92 | return max(space, 0); |
93 | } | |
c4a8dab5 | 94 | EXPORT_SYMBOL_GPL(tty_buffer_space_avail); |
7bfe0b71 | 95 | |
9dd5139f PH |
96 | static void tty_buffer_reset(struct tty_buffer *p, size_t size) |
97 | { | |
98 | p->used = 0; | |
99 | p->size = size; | |
100 | p->next = NULL; | |
101 | p->commit = 0; | |
102 | p->read = 0; | |
acc0f67f | 103 | p->flags = 0; |
9dd5139f PH |
104 | } |
105 | ||
e0495736 AC |
106 | /** |
107 | * tty_buffer_free_all - free buffers used by a tty | |
108 | * @tty: tty to free from | |
109 | * | |
110 | * Remove all the buffers pending on a tty whether queued with data | |
111 | * or in the free ring. Must be called when the tty is no longer in use | |
e0495736 AC |
112 | */ |
113 | ||
ecbbfd44 | 114 | void tty_buffer_free_all(struct tty_port *port) |
e0495736 | 115 | { |
ecbbfd44 | 116 | struct tty_bufhead *buf = &port->buf; |
809850b7 PH |
117 | struct tty_buffer *p, *next; |
118 | struct llist_node *llist; | |
5cff39c6 | 119 | |
2cf7b67e PH |
120 | while ((p = buf->head) != NULL) { |
121 | buf->head = p->next; | |
7391ee16 PH |
122 | if (p->size > 0) |
123 | kfree(p); | |
e0495736 | 124 | } |
809850b7 PH |
125 | llist = llist_del_all(&buf->free); |
126 | llist_for_each_entry_safe(p, next, llist, free) | |
2cf7b67e | 127 | kfree(p); |
809850b7 | 128 | |
7391ee16 PH |
129 | tty_buffer_reset(&buf->sentinel, 0); |
130 | buf->head = &buf->sentinel; | |
131 | buf->tail = &buf->sentinel; | |
7bfe0b71 | 132 | |
5dda4ca5 | 133 | atomic_set(&buf->mem_used, 0); |
e0495736 AC |
134 | } |
135 | ||
136 | /** | |
137 | * tty_buffer_alloc - allocate a tty buffer | |
138 | * @tty: tty device | |
139 | * @size: desired size (characters) | |
140 | * | |
141 | * Allocate a new tty buffer to hold the desired number of characters. | |
11b9faa4 PH |
142 | * We round our buffers off in 256 character chunks to get better |
143 | * allocation behaviour. | |
e0495736 AC |
144 | * Return NULL if out of memory or the allocation would exceed the |
145 | * per device queue | |
e0495736 AC |
146 | */ |
147 | ||
ecbbfd44 | 148 | static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) |
e0495736 | 149 | { |
809850b7 | 150 | struct llist_node *free; |
e0495736 AC |
151 | struct tty_buffer *p; |
152 | ||
11b9faa4 PH |
153 | /* Round the buffer size out */ |
154 | size = __ALIGN_MASK(size, TTYB_ALIGN_MASK); | |
155 | ||
156 | if (size <= MIN_TTYB_SIZE) { | |
809850b7 PH |
157 | free = llist_del_first(&port->buf.free); |
158 | if (free) { | |
159 | p = llist_entry(free, struct tty_buffer, free); | |
11b9faa4 PH |
160 | goto found; |
161 | } | |
162 | } | |
163 | ||
164 | /* Should possibly check if this fails for the largest buffer we | |
165 | have queued and recycle that ? */ | |
5dda4ca5 | 166 | if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit) |
e0495736 AC |
167 | return NULL; |
168 | p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); | |
169 | if (p == NULL) | |
170 | return NULL; | |
9dd5139f | 171 | |
11b9faa4 | 172 | found: |
9dd5139f | 173 | tty_buffer_reset(p, size); |
5dda4ca5 | 174 | atomic_add(size, &port->buf.mem_used); |
e0495736 AC |
175 | return p; |
176 | } | |
177 | ||
178 | /** | |
179 | * tty_buffer_free - free a tty buffer | |
180 | * @tty: tty owning the buffer | |
181 | * @b: the buffer to free | |
182 | * | |
183 | * Free a tty buffer, or add it to the free list according to our | |
184 | * internal strategy | |
e0495736 AC |
185 | */ |
186 | ||
ecbbfd44 | 187 | static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b) |
e0495736 | 188 | { |
ecbbfd44 | 189 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 190 | |
e0495736 | 191 | /* Dumb strategy for now - should keep some stats */ |
5dda4ca5 | 192 | WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0); |
e0495736 | 193 | |
1cef50e3 | 194 | if (b->size > MIN_TTYB_SIZE) |
e0495736 | 195 | kfree(b); |
7391ee16 | 196 | else if (b->size > 0) |
809850b7 | 197 | llist_add(&b->free, &buf->free); |
e0495736 AC |
198 | } |
199 | ||
e0495736 AC |
200 | /** |
201 | * tty_buffer_flush - flush full tty buffers | |
202 | * @tty: tty to flush | |
203 | * | |
753023dc | 204 | * flush all the buffers containing receive data. |
e0495736 | 205 | * |
a7c8d58c | 206 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 207 | * 'consumer' |
e0495736 AC |
208 | */ |
209 | ||
210 | void tty_buffer_flush(struct tty_struct *tty) | |
211 | { | |
2fc20661 | 212 | struct tty_port *port = tty->port; |
ecbbfd44 | 213 | struct tty_bufhead *buf = &port->buf; |
47aa658a | 214 | struct tty_buffer *next; |
e0495736 | 215 | |
a7c8d58c | 216 | atomic_inc(&buf->priority); |
e9975fde | 217 | |
a7c8d58c | 218 | mutex_lock(&buf->lock); |
47aa658a PH |
219 | while ((next = buf->head->next) != NULL) { |
220 | tty_buffer_free(port, buf->head); | |
221 | buf->head = next; | |
222 | } | |
223 | buf->head->read = buf->head->commit; | |
a7c8d58c PH |
224 | atomic_dec(&buf->priority); |
225 | mutex_unlock(&buf->lock); | |
e0495736 AC |
226 | } |
227 | ||
e0495736 | 228 | /** |
64325a3b | 229 | * tty_buffer_request_room - grow tty buffer if needed |
e0495736 AC |
230 | * @tty: tty structure |
231 | * @size: size desired | |
acc0f67f | 232 | * @flags: buffer flags if new buffer allocated (default = 0) |
e0495736 AC |
233 | * |
234 | * Make at least size bytes of linear space available for the tty | |
235 | * buffer. If we fail return the size we managed to find. | |
acc0f67f PH |
236 | * |
237 | * Will change over to a new buffer if the current buffer is encoded as | |
238 | * TTY_NORMAL (so has no flags buffer) and the new buffer requires | |
239 | * a flags buffer. | |
e0495736 | 240 | */ |
acc0f67f PH |
241 | static int __tty_buffer_request_room(struct tty_port *port, size_t size, |
242 | int flags) | |
e0495736 | 243 | { |
ecbbfd44 | 244 | struct tty_bufhead *buf = &port->buf; |
e0495736 | 245 | struct tty_buffer *b, *n; |
acc0f67f | 246 | int left, change; |
e8437d7e | 247 | |
5cff39c6 | 248 | b = buf->tail; |
acc0f67f PH |
249 | if (b->flags & TTYB_NORMAL) |
250 | left = 2 * b->size - b->used; | |
251 | else | |
252 | left = b->size - b->used; | |
e0495736 | 253 | |
acc0f67f PH |
254 | change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL); |
255 | if (change || left < size) { | |
e0495736 | 256 | /* This is the slow path - looking for new buffers to use */ |
11b9faa4 | 257 | if ((n = tty_buffer_alloc(port, size)) != NULL) { |
acc0f67f | 258 | n->flags = flags; |
5cff39c6 | 259 | buf->tail = n; |
e8437d7e PH |
260 | b->commit = b->used; |
261 | smp_mb(); | |
262 | b->next = n; | |
acc0f67f PH |
263 | } else if (change) |
264 | size = 0; | |
265 | else | |
e0495736 AC |
266 | size = left; |
267 | } | |
e0495736 AC |
268 | return size; |
269 | } | |
acc0f67f PH |
270 | |
271 | int tty_buffer_request_room(struct tty_port *port, size_t size) | |
272 | { | |
273 | return __tty_buffer_request_room(port, size, 0); | |
274 | } | |
e0495736 AC |
275 | EXPORT_SYMBOL_GPL(tty_buffer_request_room); |
276 | ||
277 | /** | |
2832fc11 | 278 | * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer |
2f693357 | 279 | * @port: tty port |
e0495736 | 280 | * @chars: characters |
2832fc11 | 281 | * @flag: flag value for each character |
e0495736 AC |
282 | * @size: size |
283 | * | |
284 | * Queue a series of bytes to the tty buffering. All the characters | |
ccc5ca8d | 285 | * passed are marked with the supplied flag. Returns the number added. |
e0495736 AC |
286 | */ |
287 | ||
2f693357 | 288 | int tty_insert_flip_string_fixed_flag(struct tty_port *port, |
2832fc11 | 289 | const unsigned char *chars, char flag, size_t size) |
e0495736 AC |
290 | { |
291 | int copied = 0; | |
292 | do { | |
d4bee0a6 | 293 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
acc0f67f PH |
294 | int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; |
295 | int space = __tty_buffer_request_room(port, goal, flags); | |
64325a3b | 296 | struct tty_buffer *tb = port->buf.tail; |
7391ee16 | 297 | if (unlikely(space == 0)) |
e0495736 | 298 | break; |
1fc359fc | 299 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
acc0f67f PH |
300 | if (~tb->flags & TTYB_NORMAL) |
301 | memset(flag_buf_ptr(tb, tb->used), flag, space); | |
e0495736 AC |
302 | tb->used += space; |
303 | copied += space; | |
304 | chars += space; | |
305 | /* There is a small chance that we need to split the data over | |
306 | several buffers. If this is the case we must loop */ | |
307 | } while (unlikely(size > copied)); | |
308 | return copied; | |
309 | } | |
2832fc11 | 310 | EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag); |
e0495736 AC |
311 | |
312 | /** | |
313 | * tty_insert_flip_string_flags - Add characters to the tty buffer | |
2f693357 | 314 | * @port: tty port |
e0495736 AC |
315 | * @chars: characters |
316 | * @flags: flag bytes | |
317 | * @size: size | |
318 | * | |
319 | * Queue a series of bytes to the tty buffering. For each character | |
320 | * the flags array indicates the status of the character. Returns the | |
321 | * number added. | |
e0495736 AC |
322 | */ |
323 | ||
2f693357 | 324 | int tty_insert_flip_string_flags(struct tty_port *port, |
e0495736 AC |
325 | const unsigned char *chars, const char *flags, size_t size) |
326 | { | |
327 | int copied = 0; | |
328 | do { | |
d4bee0a6 | 329 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
64325a3b IZ |
330 | int space = tty_buffer_request_room(port, goal); |
331 | struct tty_buffer *tb = port->buf.tail; | |
7391ee16 | 332 | if (unlikely(space == 0)) |
e0495736 | 333 | break; |
1fc359fc PH |
334 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
335 | memcpy(flag_buf_ptr(tb, tb->used), flags, space); | |
e0495736 AC |
336 | tb->used += space; |
337 | copied += space; | |
338 | chars += space; | |
339 | flags += space; | |
340 | /* There is a small chance that we need to split the data over | |
341 | several buffers. If this is the case we must loop */ | |
342 | } while (unlikely(size > copied)); | |
343 | return copied; | |
344 | } | |
345 | EXPORT_SYMBOL(tty_insert_flip_string_flags); | |
346 | ||
347 | /** | |
348 | * tty_schedule_flip - push characters to ldisc | |
6732c8bb | 349 | * @port: tty port to push from |
e0495736 AC |
350 | * |
351 | * Takes any pending buffers and transfers their ownership to the | |
352 | * ldisc side of the queue. It then schedules those characters for | |
353 | * processing by the line discipline. | |
e0495736 AC |
354 | */ |
355 | ||
6732c8bb | 356 | void tty_schedule_flip(struct tty_port *port) |
e0495736 | 357 | { |
6732c8bb | 358 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 359 | |
7391ee16 | 360 | buf->tail->commit = buf->tail->used; |
5cff39c6 | 361 | schedule_work(&buf->work); |
e0495736 AC |
362 | } |
363 | EXPORT_SYMBOL(tty_schedule_flip); | |
364 | ||
365 | /** | |
366 | * tty_prepare_flip_string - make room for characters | |
2f693357 | 367 | * @port: tty port |
e0495736 AC |
368 | * @chars: return pointer for character write area |
369 | * @size: desired size | |
370 | * | |
371 | * Prepare a block of space in the buffer for data. Returns the length | |
372 | * available and buffer pointer to the space which is now allocated and | |
373 | * accounted for as ready for normal characters. This is used for drivers | |
374 | * that need their own block copy routines into the buffer. There is no | |
375 | * guarantee the buffer is a DMA target! | |
e0495736 AC |
376 | */ |
377 | ||
2f693357 | 378 | int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars, |
ecbbfd44 | 379 | size_t size) |
e0495736 | 380 | { |
acc0f67f | 381 | int space = __tty_buffer_request_room(port, size, TTYB_NORMAL); |
e0495736 | 382 | if (likely(space)) { |
64325a3b | 383 | struct tty_buffer *tb = port->buf.tail; |
1fc359fc | 384 | *chars = char_buf_ptr(tb, tb->used); |
acc0f67f PH |
385 | if (~tb->flags & TTYB_NORMAL) |
386 | memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space); | |
e0495736 AC |
387 | tb->used += space; |
388 | } | |
389 | return space; | |
390 | } | |
391 | EXPORT_SYMBOL_GPL(tty_prepare_flip_string); | |
392 | ||
e0495736 | 393 | |
da261e7f PH |
394 | static int |
395 | receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count) | |
396 | { | |
397 | struct tty_ldisc *disc = tty->ldisc; | |
1fc359fc | 398 | unsigned char *p = char_buf_ptr(head, head->read); |
acc0f67f PH |
399 | char *f = NULL; |
400 | ||
401 | if (~head->flags & TTYB_NORMAL) | |
402 | f = flag_buf_ptr(head, head->read); | |
da261e7f | 403 | |
24a89d1c PH |
404 | if (disc->ops->receive_buf2) |
405 | count = disc->ops->receive_buf2(tty, p, f, count); | |
406 | else { | |
407 | count = min_t(int, count, tty->receive_room); | |
408 | if (count) | |
409 | disc->ops->receive_buf(tty, p, f, count); | |
410 | } | |
da261e7f PH |
411 | head->read += count; |
412 | return count; | |
413 | } | |
e0495736 AC |
414 | |
415 | /** | |
416 | * flush_to_ldisc | |
417 | * @work: tty structure passed from work queue. | |
418 | * | |
419 | * This routine is called out of the software interrupt to flush data | |
420 | * from the buffer chain to the line discipline. | |
421 | * | |
e9975fde PH |
422 | * The receive_buf method is single threaded for each tty instance. |
423 | * | |
a7c8d58c | 424 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 425 | * 'consumer' |
e0495736 AC |
426 | */ |
427 | ||
428 | static void flush_to_ldisc(struct work_struct *work) | |
429 | { | |
ecbbfd44 JS |
430 | struct tty_port *port = container_of(work, struct tty_port, buf.work); |
431 | struct tty_bufhead *buf = &port->buf; | |
432 | struct tty_struct *tty; | |
e0495736 | 433 | struct tty_ldisc *disc; |
e0495736 | 434 | |
ecbbfd44 | 435 | tty = port->itty; |
34dcfb84 | 436 | if (tty == NULL) |
ecbbfd44 JS |
437 | return; |
438 | ||
e0495736 | 439 | disc = tty_ldisc_ref(tty); |
36697529 | 440 | if (disc == NULL) |
e0495736 AC |
441 | return; |
442 | ||
a7c8d58c | 443 | mutex_lock(&buf->lock); |
45242006 | 444 | |
d7a68be4 PH |
445 | while (1) { |
446 | struct tty_buffer *head = buf->head; | |
447 | int count; | |
448 | ||
a7c8d58c PH |
449 | /* Ldisc or user is trying to gain exclusive access */ |
450 | if (atomic_read(&buf->priority)) | |
d7a68be4 PH |
451 | break; |
452 | ||
453 | count = head->commit - head->read; | |
454 | if (!count) { | |
455 | if (head->next == NULL) | |
da261e7f | 456 | break; |
d7a68be4 PH |
457 | buf->head = head->next; |
458 | tty_buffer_free(port, head); | |
459 | continue; | |
e0495736 | 460 | } |
d7a68be4 PH |
461 | |
462 | count = receive_buf(tty, head, count); | |
463 | if (!count) | |
464 | break; | |
e0495736 | 465 | } |
45242006 | 466 | |
a7c8d58c | 467 | mutex_unlock(&buf->lock); |
e0495736 AC |
468 | |
469 | tty_ldisc_deref(disc); | |
470 | } | |
471 | ||
e043e42b OH |
472 | /** |
473 | * tty_flush_to_ldisc | |
474 | * @tty: tty to push | |
475 | * | |
476 | * Push the terminal flip buffers to the line discipline. | |
477 | * | |
478 | * Must not be called from IRQ context. | |
479 | */ | |
480 | void tty_flush_to_ldisc(struct tty_struct *tty) | |
481 | { | |
a9c3f68f | 482 | flush_work(&tty->port->buf.work); |
e043e42b OH |
483 | } |
484 | ||
e0495736 AC |
485 | /** |
486 | * tty_flip_buffer_push - terminal | |
2e124b4a | 487 | * @port: tty port to push |
e0495736 | 488 | * |
a9c3f68f PH |
489 | * Queue a push of the terminal flip buffers to the line discipline. |
490 | * Can be called from IRQ/atomic context. | |
e0495736 AC |
491 | * |
492 | * In the event of the queue being busy for flipping the work will be | |
493 | * held off and retried later. | |
e0495736 AC |
494 | */ |
495 | ||
2e124b4a | 496 | void tty_flip_buffer_push(struct tty_port *port) |
e0495736 | 497 | { |
a9c3f68f | 498 | tty_schedule_flip(port); |
e0495736 AC |
499 | } |
500 | EXPORT_SYMBOL(tty_flip_buffer_push); | |
501 | ||
502 | /** | |
503 | * tty_buffer_init - prepare a tty buffer structure | |
504 | * @tty: tty to initialise | |
505 | * | |
506 | * Set up the initial state of the buffer management for a tty device. | |
507 | * Must be called before the other tty buffer functions are used. | |
e0495736 AC |
508 | */ |
509 | ||
ecbbfd44 | 510 | void tty_buffer_init(struct tty_port *port) |
e0495736 | 511 | { |
ecbbfd44 | 512 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 513 | |
a7c8d58c | 514 | mutex_init(&buf->lock); |
7391ee16 PH |
515 | tty_buffer_reset(&buf->sentinel, 0); |
516 | buf->head = &buf->sentinel; | |
517 | buf->tail = &buf->sentinel; | |
809850b7 | 518 | init_llist_head(&buf->free); |
5dda4ca5 | 519 | atomic_set(&buf->mem_used, 0); |
a7c8d58c | 520 | atomic_set(&buf->priority, 0); |
5cff39c6 | 521 | INIT_WORK(&buf->work, flush_to_ldisc); |
4d18e6ef | 522 | buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT; |
e0495736 | 523 | } |
4d18e6ef PH |
524 | |
525 | /** | |
526 | * tty_buffer_set_limit - change the tty buffer memory limit | |
527 | * @port: tty port to change | |
528 | * | |
529 | * Change the tty buffer memory limit. | |
530 | * Must be called before the other tty buffer functions are used. | |
531 | */ | |
532 | ||
533 | int tty_buffer_set_limit(struct tty_port *port, int limit) | |
534 | { | |
535 | if (limit < MIN_TTYB_SIZE) | |
536 | return -EINVAL; | |
537 | port->buf.mem_limit = limit; | |
538 | return 0; | |
539 | } | |
540 | EXPORT_SYMBOL_GPL(tty_buffer_set_limit); |