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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
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}
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 */
199int 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}
231EXPORT_SYMBOL_GPL(tty_buffer_request_room);
232
233/**
234 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
235 * @tty: tty structure
236 * @chars: characters
237 * @flag: flag value for each character
238 * @size: size
239 *
240 * Queue a series of bytes to the tty buffering. All the characters
241 * passed are marked with the supplied flag. Returns the number added.
242 *
243 * Locking: Called functions may take tty->buf.lock
244 */
245
246int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
247 const unsigned char *chars, char flag, size_t size)
248{
249 int copied = 0;
250 do {
251 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
252 int space = tty_buffer_request_room(tty, goal);
253 struct tty_buffer *tb = tty->buf.tail;
254 /* If there is no space then tb may be NULL */
255 if (unlikely(space == 0))
256 break;
257 memcpy(tb->char_buf_ptr + tb->used, chars, space);
258 memset(tb->flag_buf_ptr + tb->used, flag, space);
259 tb->used += space;
260 copied += space;
261 chars += space;
262 /* There is a small chance that we need to split the data over
263 several buffers. If this is the case we must loop */
264 } while (unlikely(size > copied));
265 return copied;
266}
267EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
268
269/**
270 * tty_insert_flip_string_flags - Add characters to the tty buffer
271 * @tty: tty structure
272 * @chars: characters
273 * @flags: flag bytes
274 * @size: size
275 *
276 * Queue a series of bytes to the tty buffering. For each character
277 * the flags array indicates the status of the character. Returns the
278 * number added.
279 *
280 * Locking: Called functions may take tty->buf.lock
281 */
282
283int tty_insert_flip_string_flags(struct tty_struct *tty,
284 const unsigned char *chars, const char *flags, size_t size)
285{
286 int copied = 0;
287 do {
288 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
289 int space = tty_buffer_request_room(tty, goal);
290 struct tty_buffer *tb = tty->buf.tail;
291 /* If there is no space then tb may be NULL */
292 if (unlikely(space == 0))
293 break;
294 memcpy(tb->char_buf_ptr + tb->used, chars, space);
295 memcpy(tb->flag_buf_ptr + tb->used, flags, space);
296 tb->used += space;
297 copied += space;
298 chars += space;
299 flags += space;
300 /* There is a small chance that we need to split the data over
301 several buffers. If this is the case we must loop */
302 } while (unlikely(size > copied));
303 return copied;
304}
305EXPORT_SYMBOL(tty_insert_flip_string_flags);
306
307/**
308 * tty_schedule_flip - push characters to ldisc
309 * @tty: tty to push from
310 *
311 * Takes any pending buffers and transfers their ownership to the
312 * ldisc side of the queue. It then schedules those characters for
313 * processing by the line discipline.
314 *
315 * Locking: Takes tty->buf.lock
316 */
317
318void tty_schedule_flip(struct tty_struct *tty)
319{
320 unsigned long flags;
321 spin_lock_irqsave(&tty->buf.lock, flags);
322 if (tty->buf.tail != NULL)
323 tty->buf.tail->commit = tty->buf.tail->used;
324 spin_unlock_irqrestore(&tty->buf.lock, flags);
325 schedule_work(&tty->buf.work);
326}
327EXPORT_SYMBOL(tty_schedule_flip);
328
329/**
330 * tty_prepare_flip_string - make room for characters
331 * @tty: tty
332 * @chars: return pointer for character write area
333 * @size: desired size
334 *
335 * Prepare a block of space in the buffer for data. Returns the length
336 * available and buffer pointer to the space which is now allocated and
337 * accounted for as ready for normal characters. This is used for drivers
338 * that need their own block copy routines into the buffer. There is no
339 * guarantee the buffer is a DMA target!
340 *
341 * Locking: May call functions taking tty->buf.lock
342 */
343
344int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
345 size_t size)
346{
347 int space = tty_buffer_request_room(tty, size);
348 if (likely(space)) {
349 struct tty_buffer *tb = tty->buf.tail;
350 *chars = tb->char_buf_ptr + tb->used;
351 memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
352 tb->used += space;
353 }
354 return space;
355}
356EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
357
358/**
359 * tty_prepare_flip_string_flags - make room for characters
360 * @tty: tty
361 * @chars: return pointer for character write area
362 * @flags: return pointer for status flag write area
363 * @size: desired size
364 *
365 * Prepare a block of space in the buffer for data. Returns the length
366 * available and buffer pointer to the space which is now allocated and
367 * accounted for as ready for characters. This is used for drivers
368 * that need their own block copy routines into the buffer. There is no
369 * guarantee the buffer is a DMA target!
370 *
371 * Locking: May call functions taking tty->buf.lock
372 */
373
374int tty_prepare_flip_string_flags(struct tty_struct *tty,
375 unsigned char **chars, char **flags, size_t size)
376{
377 int space = tty_buffer_request_room(tty, size);
378 if (likely(space)) {
379 struct tty_buffer *tb = tty->buf.tail;
380 *chars = tb->char_buf_ptr + tb->used;
381 *flags = tb->flag_buf_ptr + tb->used;
382 tb->used += space;
383 }
384 return space;
385}
386EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
387
388
389
390/**
391 * flush_to_ldisc
392 * @work: tty structure passed from work queue.
393 *
394 * This routine is called out of the software interrupt to flush data
395 * from the buffer chain to the line discipline.
396 *
397 * Locking: holds tty->buf.lock to guard buffer list. Drops the lock
398 * while invoking the line discipline receive_buf method. The
399 * receive_buf method is single threaded for each tty instance.
400 */
401
402static void flush_to_ldisc(struct work_struct *work)
403{
404 struct tty_struct *tty =
405 container_of(work, struct tty_struct, buf.work);
406 unsigned long flags;
407 struct tty_ldisc *disc;
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
415 if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {
416 struct tty_buffer *head;
417 while ((head = tty->buf.head) != NULL) {
418 int count;
419 char *char_buf;
420 unsigned char *flag_buf;
421
422 count = head->commit - head->read;
423 if (!count) {
424 if (head->next == NULL)
425 break;
426 tty->buf.head = head->next;
427 tty_buffer_free(tty, head);
428 continue;
429 }
430 /* Ldisc or user is trying to flush the buffers
431 we are feeding to the ldisc, stop feeding the
432 line discipline as we want to empty the queue */
433 if (test_bit(TTY_FLUSHPENDING, &tty->flags))
434 break;
435 if (!tty->receive_room)
436 break;
437 if (count > tty->receive_room)
438 count = tty->receive_room;
439 char_buf = head->char_buf_ptr + head->read;
440 flag_buf = head->flag_buf_ptr + head->read;
441 head->read += count;
442 spin_unlock_irqrestore(&tty->buf.lock, flags);
443 disc->ops->receive_buf(tty, char_buf,
444 flag_buf, count);
445 spin_lock_irqsave(&tty->buf.lock, flags);
446 }
447 clear_bit(TTY_FLUSHING, &tty->flags);
448 }
449
450 /* We may have a deferred request to flush the input buffer,
451 if so pull the chain under the lock and empty the queue */
452 if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
453 __tty_buffer_flush(tty);
454 clear_bit(TTY_FLUSHPENDING, &tty->flags);
455 wake_up(&tty->read_wait);
456 }
457 spin_unlock_irqrestore(&tty->buf.lock, flags);
458
459 tty_ldisc_deref(disc);
460}
461
462/**
463 * tty_flush_to_ldisc
464 * @tty: tty to push
465 *
466 * Push the terminal flip buffers to the line discipline.
467 *
468 * Must not be called from IRQ context.
469 */
470void tty_flush_to_ldisc(struct tty_struct *tty)
471{
472 flush_work(&tty->buf.work);
473}
474
475/**
476 * tty_flip_buffer_push - terminal
477 * @tty: tty to push
478 *
479 * Queue a push of the terminal flip buffers to the line discipline. This
480 * function must not be called from IRQ context if tty->low_latency is set.
481 *
482 * In the event of the queue being busy for flipping the work will be
483 * held off and retried later.
484 *
485 * Locking: tty buffer lock. Driver locks in low latency mode.
486 */
487
488void tty_flip_buffer_push(struct tty_struct *tty)
489{
490 unsigned long flags;
491 spin_lock_irqsave(&tty->buf.lock, flags);
492 if (tty->buf.tail != NULL)
493 tty->buf.tail->commit = tty->buf.tail->used;
494 spin_unlock_irqrestore(&tty->buf.lock, flags);
495
496 if (tty->low_latency)
497 flush_to_ldisc(&tty->buf.work);
498 else
499 schedule_work(&tty->buf.work);
500}
501EXPORT_SYMBOL(tty_flip_buffer_push);
502
503/**
504 * tty_buffer_init - prepare a tty buffer structure
505 * @tty: tty to initialise
506 *
507 * Set up the initial state of the buffer management for a tty device.
508 * Must be called before the other tty buffer functions are used.
509 *
510 * Locking: none
511 */
512
513void tty_buffer_init(struct tty_struct *tty)
514{
515 spin_lock_init(&tty->buf.lock);
516 tty->buf.head = NULL;
517 tty->buf.tail = NULL;
518 tty->buf.free = NULL;
519 tty->buf.memory_used = 0;
520 INIT_WORK(&tty->buf.work, flush_to_ldisc);
521}
522
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/wait.h>
15#include <linux/bitops.h>
16#include <linux/delay.h>
17#include <linux/module.h>
18#include <linux/ratelimit.h>
19
20
21#define MIN_TTYB_SIZE 256
22#define TTYB_ALIGN_MASK 255
23
24/*
25 * Byte threshold to limit memory consumption for flip buffers.
26 * The actual memory limit is > 2x this amount.
27 */
28#define TTYB_DEFAULT_MEM_LIMIT 65536
29
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
40
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
56void 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}
63EXPORT_SYMBOL_GPL(tty_buffer_lock_exclusive);
64
65void 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}
77EXPORT_SYMBOL_GPL(tty_buffer_unlock_exclusive);
78
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
91int tty_buffer_space_avail(struct tty_port *port)
92{
93 int space = port->buf.mem_limit - atomic_read(&port->buf.mem_used);
94 return max(space, 0);
95}
96EXPORT_SYMBOL_GPL(tty_buffer_space_avail);
97
98static 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;
105 p->flags = 0;
106}
107
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
114 */
115
116void tty_buffer_free_all(struct tty_port *port)
117{
118 struct tty_bufhead *buf = &port->buf;
119 struct tty_buffer *p, *next;
120 struct llist_node *llist;
121
122 while ((p = buf->head) != NULL) {
123 buf->head = p->next;
124 if (p->size > 0)
125 kfree(p);
126 }
127 llist = llist_del_all(&buf->free);
128 llist_for_each_entry_safe(p, next, llist, free)
129 kfree(p);
130
131 tty_buffer_reset(&buf->sentinel, 0);
132 buf->head = &buf->sentinel;
133 buf->tail = &buf->sentinel;
134
135 atomic_set(&buf->mem_used, 0);
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.
144 * We round our buffers off in 256 character chunks to get better
145 * allocation behaviour.
146 * Return NULL if out of memory or the allocation would exceed the
147 * per device queue
148 */
149
150static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
151{
152 struct llist_node *free;
153 struct tty_buffer *p;
154
155 /* Round the buffer size out */
156 size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
157
158 if (size <= MIN_TTYB_SIZE) {
159 free = llist_del_first(&port->buf.free);
160 if (free) {
161 p = llist_entry(free, struct tty_buffer, free);
162 goto found;
163 }
164 }
165
166 /* Should possibly check if this fails for the largest buffer we
167 have queued and recycle that ? */
168 if (atomic_read(&port->buf.mem_used) > port->buf.mem_limit)
169 return NULL;
170 p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
171 if (p == NULL)
172 return NULL;
173
174found:
175 tty_buffer_reset(p, size);
176 atomic_add(size, &port->buf.mem_used);
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
187 */
188
189static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
190{
191 struct tty_bufhead *buf = &port->buf;
192
193 /* Dumb strategy for now - should keep some stats */
194 WARN_ON(atomic_sub_return(b->size, &buf->mem_used) < 0);
195
196 if (b->size > MIN_TTYB_SIZE)
197 kfree(b);
198 else if (b->size > 0)
199 llist_add(&b->free, &buf->free);
200}
201
202/**
203 * tty_buffer_flush - flush full tty buffers
204 * @tty: tty to flush
205 *
206 * flush all the buffers containing receive data.
207 *
208 * Locking: takes buffer lock to ensure single-threaded flip buffer
209 * 'consumer'
210 */
211
212void tty_buffer_flush(struct tty_struct *tty)
213{
214 struct tty_port *port = tty->port;
215 struct tty_bufhead *buf = &port->buf;
216 struct tty_buffer *next;
217
218 atomic_inc(&buf->priority);
219
220 mutex_lock(&buf->lock);
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;
226 atomic_dec(&buf->priority);
227 mutex_unlock(&buf->lock);
228}
229
230/**
231 * tty_buffer_request_room - grow tty buffer if needed
232 * @tty: tty structure
233 * @size: size desired
234 * @flags: buffer flags if new buffer allocated (default = 0)
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.
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.
242 */
243static int __tty_buffer_request_room(struct tty_port *port, size_t size,
244 int flags)
245{
246 struct tty_bufhead *buf = &port->buf;
247 struct tty_buffer *b, *n;
248 int left, change;
249
250 b = buf->tail;
251 if (b->flags & TTYB_NORMAL)
252 left = 2 * b->size - b->used;
253 else
254 left = b->size - b->used;
255
256 change = (b->flags & TTYB_NORMAL) && (~flags & TTYB_NORMAL);
257 if (change || left < size) {
258 /* This is the slow path - looking for new buffers to use */
259 if ((n = tty_buffer_alloc(port, size)) != NULL) {
260 n->flags = flags;
261 buf->tail = n;
262 b->commit = b->used;
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();
268 b->next = n;
269 } else if (change)
270 size = 0;
271 else
272 size = left;
273 }
274 return size;
275}
276
277int tty_buffer_request_room(struct tty_port *port, size_t size)
278{
279 return __tty_buffer_request_room(port, size, 0);
280}
281EXPORT_SYMBOL_GPL(tty_buffer_request_room);
282
283/**
284 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
285 * @port: tty port
286 * @chars: characters
287 * @flag: flag value for each character
288 * @size: size
289 *
290 * Queue a series of bytes to the tty buffering. All the characters
291 * passed are marked with the supplied flag. Returns the number added.
292 */
293
294int tty_insert_flip_string_fixed_flag(struct tty_port *port,
295 const unsigned char *chars, char flag, size_t size)
296{
297 int copied = 0;
298 do {
299 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
300 int flags = (flag == TTY_NORMAL) ? TTYB_NORMAL : 0;
301 int space = __tty_buffer_request_room(port, goal, flags);
302 struct tty_buffer *tb = port->buf.tail;
303 if (unlikely(space == 0))
304 break;
305 memcpy(char_buf_ptr(tb, tb->used), chars, space);
306 if (~tb->flags & TTYB_NORMAL)
307 memset(flag_buf_ptr(tb, tb->used), flag, space);
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}
316EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
317
318/**
319 * tty_insert_flip_string_flags - Add characters to the tty buffer
320 * @port: tty port
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.
328 */
329
330int tty_insert_flip_string_flags(struct tty_port *port,
331 const unsigned char *chars, const char *flags, size_t size)
332{
333 int copied = 0;
334 do {
335 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
336 int space = tty_buffer_request_room(port, goal);
337 struct tty_buffer *tb = port->buf.tail;
338 if (unlikely(space == 0))
339 break;
340 memcpy(char_buf_ptr(tb, tb->used), chars, space);
341 memcpy(flag_buf_ptr(tb, tb->used), flags, space);
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}
351EXPORT_SYMBOL(tty_insert_flip_string_flags);
352
353/**
354 * tty_schedule_flip - push characters to ldisc
355 * @port: tty port to push from
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.
360 */
361
362void tty_schedule_flip(struct tty_port *port)
363{
364 struct tty_bufhead *buf = &port->buf;
365
366 buf->tail->commit = buf->tail->used;
367 schedule_work(&buf->work);
368}
369EXPORT_SYMBOL(tty_schedule_flip);
370
371/**
372 * tty_prepare_flip_string - make room for characters
373 * @port: tty port
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!
382 */
383
384int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
385 size_t size)
386{
387 int space = __tty_buffer_request_room(port, size, TTYB_NORMAL);
388 if (likely(space)) {
389 struct tty_buffer *tb = port->buf.tail;
390 *chars = char_buf_ptr(tb, tb->used);
391 if (~tb->flags & TTYB_NORMAL)
392 memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
393 tb->used += space;
394 }
395 return space;
396}
397EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
398
399
400static int
401receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
402{
403 struct tty_ldisc *disc = tty->ldisc;
404 unsigned char *p = char_buf_ptr(head, head->read);
405 char *f = NULL;
406
407 if (~head->flags & TTYB_NORMAL)
408 f = flag_buf_ptr(head, head->read);
409
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 }
417 head->read += count;
418 return count;
419}
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 *
428 * The receive_buf method is single threaded for each tty instance.
429 *
430 * Locking: takes buffer lock to ensure single-threaded flip buffer
431 * 'consumer'
432 */
433
434static void flush_to_ldisc(struct work_struct *work)
435{
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;
439 struct tty_ldisc *disc;
440
441 tty = port->itty;
442 if (tty == NULL)
443 return;
444
445 disc = tty_ldisc_ref(tty);
446 if (disc == NULL)
447 return;
448
449 mutex_lock(&buf->lock);
450
451 while (1) {
452 struct tty_buffer *head = buf->head;
453 struct tty_buffer *next;
454 int count;
455
456 /* Ldisc or user is trying to gain exclusive access */
457 if (atomic_read(&buf->priority))
458 break;
459
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();
466 count = head->commit - head->read;
467 if (!count) {
468 if (next == NULL)
469 break;
470 buf->head = next;
471 tty_buffer_free(port, head);
472 continue;
473 }
474
475 count = receive_buf(tty, head, count);
476 if (!count)
477 break;
478 }
479
480 mutex_unlock(&buf->lock);
481
482 tty_ldisc_deref(disc);
483}
484
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 */
493void tty_flush_to_ldisc(struct tty_struct *tty)
494{
495 flush_work(&tty->port->buf.work);
496}
497
498/**
499 * tty_flip_buffer_push - terminal
500 * @port: tty port to push
501 *
502 * Queue a push of the terminal flip buffers to the line discipline.
503 * Can be called from IRQ/atomic context.
504 *
505 * In the event of the queue being busy for flipping the work will be
506 * held off and retried later.
507 */
508
509void tty_flip_buffer_push(struct tty_port *port)
510{
511 tty_schedule_flip(port);
512}
513EXPORT_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.
521 */
522
523void tty_buffer_init(struct tty_port *port)
524{
525 struct tty_bufhead *buf = &port->buf;
526
527 mutex_init(&buf->lock);
528 tty_buffer_reset(&buf->sentinel, 0);
529 buf->head = &buf->sentinel;
530 buf->tail = &buf->sentinel;
531 init_llist_head(&buf->free);
532 atomic_set(&buf->mem_used, 0);
533 atomic_set(&buf->priority, 0);
534 INIT_WORK(&buf->work, flush_to_ldisc);
535 buf->mem_limit = TTYB_DEFAULT_MEM_LIMIT;
536}
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
546int 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}
553EXPORT_SYMBOL_GPL(tty_buffer_set_limit);