Commit | Line | Data |
---|---|---|
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 | } | |
28a821c3 | 63 | EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive); |
a7c8d58c PH |
64 | |
65 | void tty_buffer_unlock_exclusive(struct tty_port *port) | |
66 | { | |
67 | struct tty_bufhead *buf = &port->buf; | |
68 | int restart; | |
69 | ||
70 | restart = buf->head->commit != buf->head->read; | |
71 | ||
72 | atomic_dec(&buf->priority); | |
73 | mutex_unlock(&buf->lock); | |
74 | if (restart) | |
75 | queue_work(system_unbound_wq, &buf->work); | |
76 | } | |
28a821c3 | 77 | EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive); |
a7c8d58c | 78 | |
7bfe0b71 PH |
79 | /** |
80 | * tty_buffer_space_avail - return unused buffer space | |
81 | * @port - tty_port owning the flip buffer | |
82 | * | |
83 | * Returns the # of bytes which can be written by the driver without | |
84 | * reaching the buffer limit. | |
85 | * | |
86 | * Note: this does not guarantee that memory is available to write | |
87 | * the returned # of bytes (use tty_prepare_flip_string_xxx() to | |
88 | * pre-allocate if memory guarantee is required). | |
89 | */ | |
90 | ||
91 | int tty_buffer_space_avail(struct tty_port *port) | |
92 | { | |
5dda4ca5 | 93 | int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used); |
7bfe0b71 PH |
94 | return max(space, 0); |
95 | } | |
c4a8dab5 | 96 | EXPORT_SYMBOL_GPL(tty_buffer_space_avail); |
7bfe0b71 | 97 | |
9dd5139f PH |
98 | static void tty_buffer_reset(struct tty_buffer *p, size_t size) |
99 | { | |
100 | p->used = 0; | |
101 | p->size = size; | |
102 | p->next = NULL; | |
103 | p->commit = 0; | |
104 | p->read = 0; | |
acc0f67f | 105 | p->flags = 0; |
9dd5139f PH |
106 | } |
107 | ||
e0495736 AC |
108 | /** |
109 | * tty_buffer_free_all - free buffers used by a tty | |
110 | * @tty: tty to free from | |
111 | * | |
112 | * Remove all the buffers pending on a tty whether queued with data | |
113 | * or in the free ring. Must be called when the tty is no longer in use | |
e0495736 AC |
114 | */ |
115 | ||
ecbbfd44 | 116 | void tty_buffer_free_all(struct tty_port *port) |
e0495736 | 117 | { |
ecbbfd44 | 118 | struct tty_bufhead *buf = &port->buf; |
809850b7 PH |
119 | struct tty_buffer *p, *next; |
120 | struct llist_node *llist; | |
5cff39c6 | 121 | |
2cf7b67e PH |
122 | while ((p = buf->head) != NULL) { |
123 | buf->head = p->next; | |
7391ee16 PH |
124 | if (p->size > 0) |
125 | kfree(p); | |
e0495736 | 126 | } |
809850b7 PH |
127 | llist = llist_del_all(&buf->free); |
128 | llist_for_each_entry_safe(p, next, llist, free) | |
2cf7b67e | 129 | kfree(p); |
809850b7 | 130 | |
7391ee16 PH |
131 | tty_buffer_reset(&buf->sentinel, 0); |
132 | buf->head = &buf->sentinel; | |
133 | buf->tail = &buf->sentinel; | |
7bfe0b71 | 134 | |
5dda4ca5 | 135 | atomic_set(&buf->mem_used, 0); |
e0495736 AC |
136 | } |
137 | ||
138 | /** | |
139 | * tty_buffer_alloc - allocate a tty buffer | |
140 | * @tty: tty device | |
141 | * @size: desired size (characters) | |
142 | * | |
143 | * Allocate a new tty buffer to hold the desired number of characters. | |
11b9faa4 PH |
144 | * We round our buffers off in 256 character chunks to get better |
145 | * allocation behaviour. | |
e0495736 AC |
146 | * Return NULL if out of memory or the allocation would exceed the |
147 | * per device queue | |
e0495736 AC |
148 | */ |
149 | ||
ecbbfd44 | 150 | static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size) |
e0495736 | 151 | { |
809850b7 | 152 | struct llist_node *free; |
e0495736 AC |
153 | struct tty_buffer *p; |
154 | ||
11b9faa4 PH |
155 | /* Round the buffer size out */ |
156 | size = __ALIGN_MASK(size, TTYB_ALIGN_MASK); | |
157 | ||
158 | if (size <= MIN_TTYB_SIZE) { | |
809850b7 PH |
159 | free = llist_del_first(&port->buf.free); |
160 | if (free) { | |
161 | p = llist_entry(free, struct tty_buffer, free); | |
11b9faa4 PH |
162 | goto found; |
163 | } | |
164 | } | |
165 | ||
166 | /* Should possibly check if this fails for the largest buffer we | |
167 | have queued and recycle that ? */ | |
5dda4ca5 | 168 | if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit) |
e0495736 AC |
169 | return NULL; |
170 | p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC); | |
171 | if (p == NULL) | |
172 | return NULL; | |
9dd5139f | 173 | |
11b9faa4 | 174 | found: |
9dd5139f | 175 | tty_buffer_reset(p, size); |
5dda4ca5 | 176 | atomic_add(size, &port->buf.mem_used); |
e0495736 AC |
177 | return p; |
178 | } | |
179 | ||
180 | /** | |
181 | * tty_buffer_free - free a tty buffer | |
182 | * @tty: tty owning the buffer | |
183 | * @b: the buffer to free | |
184 | * | |
185 | * Free a tty buffer, or add it to the free list according to our | |
186 | * internal strategy | |
e0495736 AC |
187 | */ |
188 | ||
ecbbfd44 | 189 | static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b) |
e0495736 | 190 | { |
ecbbfd44 | 191 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 192 | |
e0495736 | 193 | /* Dumb strategy for now - should keep some stats */ |
5dda4ca5 | 194 | WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0); |
e0495736 | 195 | |
1cef50e3 | 196 | if (b->size > MIN_TTYB_SIZE) |
e0495736 | 197 | kfree(b); |
7391ee16 | 198 | else if (b->size > 0) |
809850b7 | 199 | llist_add(&b->free, &buf->free); |
e0495736 AC |
200 | } |
201 | ||
e0495736 AC |
202 | /** |
203 | * tty_buffer_flush - flush full tty buffers | |
204 | * @tty: tty to flush | |
205 | * | |
753023dc | 206 | * flush all the buffers containing receive data. |
e0495736 | 207 | * |
a7c8d58c | 208 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 209 | * 'consumer' |
e0495736 AC |
210 | */ |
211 | ||
212 | void tty_buffer_flush(struct tty_struct *tty) | |
213 | { | |
2fc20661 | 214 | struct tty_port *port = tty->port; |
ecbbfd44 | 215 | struct tty_bufhead *buf = &port->buf; |
47aa658a | 216 | struct tty_buffer *next; |
e0495736 | 217 | |
a7c8d58c | 218 | atomic_inc(&buf->priority); |
e9975fde | 219 | |
a7c8d58c | 220 | mutex_lock(&buf->lock); |
47aa658a PH |
221 | while ((next = buf->head->next) != NULL) { |
222 | tty_buffer_free(port, buf->head); | |
223 | buf->head = next; | |
224 | } | |
225 | buf->head->read = buf->head->commit; | |
a7c8d58c PH |
226 | atomic_dec(&buf->priority); |
227 | mutex_unlock(&buf->lock); | |
e0495736 AC |
228 | } |
229 | ||
e0495736 | 230 | /** |
64325a3b | 231 | * tty_buffer_request_room - grow tty buffer if needed |
e0495736 AC |
232 | * @tty: tty structure |
233 | * @size: size desired | |
acc0f67f | 234 | * @flags: buffer flags if new buffer allocated (default = 0) |
e0495736 AC |
235 | * |
236 | * Make at least size bytes of linear space available for the tty | |
237 | * buffer. If we fail return the size we managed to find. | |
acc0f67f PH |
238 | * |
239 | * Will change over to a new buffer if the current buffer is encoded as | |
240 | * TTY_NORMAL (so has no flags buffer) and the new buffer requires | |
241 | * a flags buffer. | |
e0495736 | 242 | */ |
acc0f67f PH |
243 | static int __tty_buffer_request_room(struct tty_port *port, size_t size, |
244 | int flags) | |
e0495736 | 245 | { |
ecbbfd44 | 246 | struct tty_bufhead *buf = &port->buf; |
e0495736 | 247 | struct tty_buffer *b, *n; |
acc0f67f | 248 | int left, change; |
e8437d7e | 249 | |
5cff39c6 | 250 | b = buf->tail; |
acc0f67f PH |
251 | if (b->flags & TTYB_NORMAL) |
252 | left = 2 * b->size - b->used; | |
253 | else | |
254 | left = b->size - b->used; | |
e0495736 | 255 | |
acc0f67f PH |
256 | change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL); |
257 | if (change || left < size) { | |
e0495736 | 258 | /* This is the slow path - looking for new buffers to use */ |
11b9faa4 | 259 | if ((n = tty_buffer_alloc(port, size)) != NULL) { |
acc0f67f | 260 | n->flags = flags; |
5cff39c6 | 261 | buf->tail = n; |
e8437d7e | 262 | b->commit = b->used; |
62a0d8d7 PH |
263 | /* paired w/ barrier in flush_to_ldisc(); ensures the |
264 | * latest commit value can be read before the head is | |
265 | * advanced to the next buffer | |
266 | */ | |
267 | smp_wmb(); | |
e8437d7e | 268 | b->next = n; |
acc0f67f PH |
269 | } else if (change) |
270 | size = 0; | |
271 | else | |
e0495736 AC |
272 | size = left; |
273 | } | |
e0495736 AC |
274 | return size; |
275 | } | |
acc0f67f PH |
276 | |
277 | int tty_buffer_request_room(struct tty_port *port, size_t size) | |
278 | { | |
279 | return __tty_buffer_request_room(port, size, 0); | |
280 | } | |
e0495736 AC |
281 | EXPORT_SYMBOL_GPL(tty_buffer_request_room); |
282 | ||
283 | /** | |
2832fc11 | 284 | * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer |
2f693357 | 285 | * @port: tty port |
e0495736 | 286 | * @chars: characters |
2832fc11 | 287 | * @flag: flag value for each character |
e0495736 AC |
288 | * @size: size |
289 | * | |
290 | * Queue a series of bytes to the tty buffering. All the characters | |
ccc5ca8d | 291 | * passed are marked with the supplied flag. Returns the number added. |
e0495736 AC |
292 | */ |
293 | ||
2f693357 | 294 | int tty_insert_flip_string_fixed_flag(struct tty_port *port, |
2832fc11 | 295 | const unsigned char *chars, char flag, size_t size) |
e0495736 AC |
296 | { |
297 | int copied = 0; | |
298 | do { | |
d4bee0a6 | 299 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
acc0f67f PH |
300 | int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0; |
301 | int space = __tty_buffer_request_room(port, goal, flags); | |
64325a3b | 302 | struct tty_buffer *tb = port->buf.tail; |
7391ee16 | 303 | if (unlikely(space == 0)) |
e0495736 | 304 | break; |
1fc359fc | 305 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
acc0f67f PH |
306 | if (~tb->flags & TTYB_NORMAL) |
307 | memset(flag_buf_ptr(tb, tb->used), flag, space); | |
e0495736 AC |
308 | tb->used += space; |
309 | copied += space; | |
310 | chars += space; | |
311 | /* There is a small chance that we need to split the data over | |
312 | several buffers. If this is the case we must loop */ | |
313 | } while (unlikely(size > copied)); | |
314 | return copied; | |
315 | } | |
2832fc11 | 316 | EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag); |
e0495736 AC |
317 | |
318 | /** | |
319 | * tty_insert_flip_string_flags - Add characters to the tty buffer | |
2f693357 | 320 | * @port: tty port |
e0495736 AC |
321 | * @chars: characters |
322 | * @flags: flag bytes | |
323 | * @size: size | |
324 | * | |
325 | * Queue a series of bytes to the tty buffering. For each character | |
326 | * the flags array indicates the status of the character. Returns the | |
327 | * number added. | |
e0495736 AC |
328 | */ |
329 | ||
2f693357 | 330 | int tty_insert_flip_string_flags(struct tty_port *port, |
e0495736 AC |
331 | const unsigned char *chars, const char *flags, size_t size) |
332 | { | |
333 | int copied = 0; | |
334 | do { | |
d4bee0a6 | 335 | int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE); |
64325a3b IZ |
336 | int space = tty_buffer_request_room(port, goal); |
337 | struct tty_buffer *tb = port->buf.tail; | |
7391ee16 | 338 | if (unlikely(space == 0)) |
e0495736 | 339 | break; |
1fc359fc PH |
340 | memcpy(char_buf_ptr(tb, tb->used), chars, space); |
341 | memcpy(flag_buf_ptr(tb, tb->used), flags, space); | |
e0495736 AC |
342 | tb->used += space; |
343 | copied += space; | |
344 | chars += space; | |
345 | flags += space; | |
346 | /* There is a small chance that we need to split the data over | |
347 | several buffers. If this is the case we must loop */ | |
348 | } while (unlikely(size > copied)); | |
349 | return copied; | |
350 | } | |
351 | EXPORT_SYMBOL(tty_insert_flip_string_flags); | |
352 | ||
353 | /** | |
354 | * tty_schedule_flip - push characters to ldisc | |
6732c8bb | 355 | * @port: tty port to push from |
e0495736 AC |
356 | * |
357 | * Takes any pending buffers and transfers their ownership to the | |
358 | * ldisc side of the queue. It then schedules those characters for | |
359 | * processing by the line discipline. | |
e0495736 AC |
360 | */ |
361 | ||
6732c8bb | 362 | void tty_schedule_flip(struct tty_port *port) |
e0495736 | 363 | { |
6732c8bb | 364 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 365 | |
7391ee16 | 366 | buf->tail->commit = buf->tail->used; |
5cff39c6 | 367 | schedule_work(&buf->work); |
e0495736 AC |
368 | } |
369 | EXPORT_SYMBOL(tty_schedule_flip); | |
370 | ||
371 | /** | |
372 | * tty_prepare_flip_string - make room for characters | |
2f693357 | 373 | * @port: tty port |
e0495736 AC |
374 | * @chars: return pointer for character write area |
375 | * @size: desired size | |
376 | * | |
377 | * Prepare a block of space in the buffer for data. Returns the length | |
378 | * available and buffer pointer to the space which is now allocated and | |
379 | * accounted for as ready for normal characters. This is used for drivers | |
380 | * that need their own block copy routines into the buffer. There is no | |
381 | * guarantee the buffer is a DMA target! | |
e0495736 AC |
382 | */ |
383 | ||
2f693357 | 384 | int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars, |
ecbbfd44 | 385 | size_t size) |
e0495736 | 386 | { |
acc0f67f | 387 | int space = __tty_buffer_request_room(port, size, TTYB_NORMAL); |
e0495736 | 388 | if (likely(space)) { |
64325a3b | 389 | struct tty_buffer *tb = port->buf.tail; |
1fc359fc | 390 | *chars = char_buf_ptr(tb, tb->used); |
acc0f67f PH |
391 | if (~tb->flags & TTYB_NORMAL) |
392 | memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space); | |
e0495736 AC |
393 | tb->used += space; |
394 | } | |
395 | return space; | |
396 | } | |
397 | EXPORT_SYMBOL_GPL(tty_prepare_flip_string); | |
398 | ||
e0495736 | 399 | |
da261e7f PH |
400 | static int |
401 | receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count) | |
402 | { | |
403 | struct tty_ldisc *disc = tty->ldisc; | |
1fc359fc | 404 | unsigned char *p = char_buf_ptr(head, head->read); |
acc0f67f PH |
405 | char *f = NULL; |
406 | ||
407 | if (~head->flags & TTYB_NORMAL) | |
408 | f = flag_buf_ptr(head, head->read); | |
da261e7f | 409 | |
24a89d1c PH |
410 | if (disc->ops->receive_buf2) |
411 | count = disc->ops->receive_buf2(tty, p, f, count); | |
412 | else { | |
413 | count = min_t(int, count, tty->receive_room); | |
414 | if (count) | |
415 | disc->ops->receive_buf(tty, p, f, count); | |
416 | } | |
da261e7f PH |
417 | head->read += count; |
418 | return count; | |
419 | } | |
e0495736 AC |
420 | |
421 | /** | |
422 | * flush_to_ldisc | |
423 | * @work: tty structure passed from work queue. | |
424 | * | |
425 | * This routine is called out of the software interrupt to flush data | |
426 | * from the buffer chain to the line discipline. | |
427 | * | |
e9975fde PH |
428 | * The receive_buf method is single threaded for each tty instance. |
429 | * | |
a7c8d58c | 430 | * Locking: takes buffer lock to ensure single-threaded flip buffer |
e9975fde | 431 | * 'consumer' |
e0495736 AC |
432 | */ |
433 | ||
434 | static void flush_to_ldisc(struct work_struct *work) | |
435 | { | |
ecbbfd44 JS |
436 | struct tty_port *port = container_of(work, struct tty_port, buf.work); |
437 | struct tty_bufhead *buf = &port->buf; | |
438 | struct tty_struct *tty; | |
e0495736 | 439 | struct tty_ldisc *disc; |
e0495736 | 440 | |
ecbbfd44 | 441 | tty = port->itty; |
34dcfb84 | 442 | if (tty == NULL) |
ecbbfd44 JS |
443 | return; |
444 | ||
e0495736 | 445 | disc = tty_ldisc_ref(tty); |
36697529 | 446 | if (disc == NULL) |
e0495736 AC |
447 | return; |
448 | ||
a7c8d58c | 449 | mutex_lock(&buf->lock); |
45242006 | 450 | |
d7a68be4 PH |
451 | while (1) { |
452 | struct tty_buffer *head = buf->head; | |
62a0d8d7 | 453 | struct tty_buffer *next; |
d7a68be4 PH |
454 | int count; |
455 | ||
a7c8d58c PH |
456 | /* Ldisc or user is trying to gain exclusive access */ |
457 | if (atomic_read(&buf->priority)) | |
d7a68be4 PH |
458 | break; |
459 | ||
62a0d8d7 PH |
460 | next = head->next; |
461 | /* paired w/ barrier in __tty_buffer_request_room(); | |
462 | * ensures commit value read is not stale if the head | |
463 | * is advancing to the next buffer | |
464 | */ | |
465 | smp_rmb(); | |
d7a68be4 PH |
466 | count = head->commit - head->read; |
467 | if (!count) { | |
62a0d8d7 | 468 | if (next == NULL) |
da261e7f | 469 | break; |
62a0d8d7 | 470 | buf->head = next; |
d7a68be4 PH |
471 | tty_buffer_free(port, head); |
472 | continue; | |
e0495736 | 473 | } |
d7a68be4 PH |
474 | |
475 | count = receive_buf(tty, head, count); | |
476 | if (!count) | |
477 | break; | |
e0495736 | 478 | } |
45242006 | 479 | |
a7c8d58c | 480 | mutex_unlock(&buf->lock); |
e0495736 AC |
481 | |
482 | tty_ldisc_deref(disc); | |
483 | } | |
484 | ||
e043e42b OH |
485 | /** |
486 | * tty_flush_to_ldisc | |
487 | * @tty: tty to push | |
488 | * | |
489 | * Push the terminal flip buffers to the line discipline. | |
490 | * | |
491 | * Must not be called from IRQ context. | |
492 | */ | |
493 | void tty_flush_to_ldisc(struct tty_struct *tty) | |
494 | { | |
a9c3f68f | 495 | flush_work(&tty->port->buf.work); |
e043e42b OH |
496 | } |
497 | ||
e0495736 AC |
498 | /** |
499 | * tty_flip_buffer_push - terminal | |
2e124b4a | 500 | * @port: tty port to push |
e0495736 | 501 | * |
a9c3f68f PH |
502 | * Queue a push of the terminal flip buffers to the line discipline. |
503 | * Can be called from IRQ/atomic context. | |
e0495736 AC |
504 | * |
505 | * In the event of the queue being busy for flipping the work will be | |
506 | * held off and retried later. | |
e0495736 AC |
507 | */ |
508 | ||
2e124b4a | 509 | void tty_flip_buffer_push(struct tty_port *port) |
e0495736 | 510 | { |
a9c3f68f | 511 | tty_schedule_flip(port); |
e0495736 AC |
512 | } |
513 | EXPORT_SYMBOL(tty_flip_buffer_push); | |
514 | ||
515 | /** | |
516 | * tty_buffer_init - prepare a tty buffer structure | |
517 | * @tty: tty to initialise | |
518 | * | |
519 | * Set up the initial state of the buffer management for a tty device. | |
520 | * Must be called before the other tty buffer functions are used. | |
e0495736 AC |
521 | */ |
522 | ||
ecbbfd44 | 523 | void tty_buffer_init(struct tty_port *port) |
e0495736 | 524 | { |
ecbbfd44 | 525 | struct tty_bufhead *buf = &port->buf; |
5cff39c6 | 526 | |
a7c8d58c | 527 | mutex_init(&buf->lock); |
7391ee16 PH |
528 | tty_buffer_reset(&buf->sentinel, 0); |
529 | buf->head = &buf->sentinel; | |
530 | buf->tail = &buf->sentinel; | |
809850b7 | 531 | init_llist_head(&buf->free); |
5dda4ca5 | 532 | atomic_set(&buf->mem_used, 0); |
a7c8d58c | 533 | atomic_set(&buf->priority, 0); |
5cff39c6 | 534 | INIT_WORK(&buf->work, flush_to_ldisc); |
4d18e6ef | 535 | buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT; |
e0495736 | 536 | } |
4d18e6ef PH |
537 | |
538 | /** | |
539 | * tty_buffer_set_limit - change the tty buffer memory limit | |
540 | * @port: tty port to change | |
541 | * | |
542 | * Change the tty buffer memory limit. | |
543 | * Must be called before the other tty buffer functions are used. | |
544 | */ | |
545 | ||
546 | int tty_buffer_set_limit(struct tty_port *port, int limit) | |
547 | { | |
548 | if (limit < MIN_TTYB_SIZE) | |
549 | return -EINVAL; | |
550 | port->buf.mem_limit = limit; | |
551 | return 0; | |
552 | } | |
553 | EXPORT_SYMBOL_GPL(tty_buffer_set_limit); |