2 * Tty buffer allocation management
5 #include <linux/types.h>
6 #include <linux/errno.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>
21 * tty_buffer_free_all - free buffers used by a tty
22 * @tty: tty to free from
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
30 void tty_buffer_free_all(struct tty_struct *tty)
32 struct tty_buffer *thead;
33 while ((thead = tty->buf.head) != NULL) {
34 tty->buf.head = thead->next;
37 while ((thead = tty->buf.free) != NULL) {
38 tty->buf.free = thead->next;
42 tty->buf.memory_used = 0;
46 * tty_buffer_alloc - allocate a tty buffer
48 * @size: desired size (characters)
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
54 * Locking: Caller must hold tty->buf.lock
57 static struct tty_buffer *tty_buffer_alloc(struct tty_struct *tty, size_t size)
61 if (tty->buf.memory_used + size > 65536)
63 p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
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;
78 * tty_buffer_free - free a tty buffer
79 * @tty: tty owning the buffer
80 * @b: the buffer to free
82 * Free a tty buffer, or add it to the free list according to our
85 * Locking: Caller must hold tty->buf.lock
88 static void tty_buffer_free(struct tty_struct *tty, struct tty_buffer *b)
90 /* Dumb strategy for now - should keep some stats */
91 tty->buf.memory_used -= b->size;
92 WARN_ON(tty->buf.memory_used < 0);
97 b->next = tty->buf.free;
103 * __tty_buffer_flush - flush full tty buffers
106 * flush all the buffers containing receive data. Caller must
107 * hold the buffer lock and must have ensured no parallel flush to
110 * Locking: Caller must hold tty->buf.lock
113 static void __tty_buffer_flush(struct tty_struct *tty)
115 struct tty_buffer *thead;
117 while ((thead = tty->buf.head) != NULL) {
118 tty->buf.head = thead->next;
119 tty_buffer_free(tty, thead);
121 tty->buf.tail = NULL;
125 * tty_buffer_flush - flush full tty buffers
128 * flush all the buffers containing receive data. If the buffer is
129 * being processed by flush_to_ldisc then we defer the processing
135 void tty_buffer_flush(struct tty_struct *tty)
138 spin_lock_irqsave(&tty->buf.lock, flags);
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);
150 __tty_buffer_flush(tty);
151 spin_unlock_irqrestore(&tty->buf.lock, flags);
155 * tty_buffer_find - find a free tty buffer
156 * @tty: tty owning the buffer
157 * @size: characters wanted
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.
163 * Locking: Caller must hold tty->buf.lock
166 static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
168 struct tty_buffer **tbh = &tty->buf.free;
169 while ((*tbh) != NULL) {
170 struct tty_buffer *t = *tbh;
171 if (t->size >= size) {
177 tty->buf.memory_used += t->size;
180 tbh = &((*tbh)->next);
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 ? */
189 * __tty_buffer_request_room - grow tty buffer if needed
190 * @tty: tty structure
191 * @size: size desired
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.
195 * Locking: Caller must hold tty->buf.lock
197 static int __tty_buffer_request_room(struct tty_struct *tty, size_t size)
199 struct tty_buffer *b, *n;
201 /* OPTIMISATION: We could keep a per tty "zero" sized buffer to
202 remove this conditional if its worth it. This would be invisible
204 if ((b = tty->buf.tail) != NULL)
205 left = b->size - b->used;
210 /* This is the slow path - looking for new buffers to use */
211 if ((n = tty_buffer_find(tty, size)) != NULL) {
227 * tty_buffer_request_room - grow tty buffer if needed
228 * @tty: tty structure
229 * @size: size desired
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.
234 * Locking: Takes tty->buf.lock
236 int tty_buffer_request_room(struct tty_struct *tty, size_t size)
241 spin_lock_irqsave(&tty->buf.lock, flags);
242 length = __tty_buffer_request_room(tty, size);
243 spin_unlock_irqrestore(&tty->buf.lock, flags);
246 EXPORT_SYMBOL_GPL(tty_buffer_request_room);
249 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
250 * @tty: tty structure
252 * @flag: flag value for each character
255 * Queue a series of bytes to the tty buffering. All the characters
256 * passed are marked with the supplied flag. Returns the number added.
258 * Locking: Called functions may take tty->buf.lock
261 int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
262 const unsigned char *chars, char flag, size_t size)
266 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
269 struct tty_buffer *tb;
271 spin_lock_irqsave(&tty->buf.lock, flags);
272 space = __tty_buffer_request_room(tty, goal);
274 /* If there is no space then tb may be NULL */
275 if (unlikely(space == 0)) {
276 spin_unlock_irqrestore(&tty->buf.lock, flags);
279 memcpy(tb->char_buf_ptr + tb->used, chars, space);
280 memset(tb->flag_buf_ptr + tb->used, flag, space);
282 spin_unlock_irqrestore(&tty->buf.lock, flags);
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));
290 EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
293 * tty_insert_flip_string_flags - Add characters to the tty buffer
294 * @tty: tty structure
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
303 * Locking: Called functions may take tty->buf.lock
306 int tty_insert_flip_string_flags(struct tty_struct *tty,
307 const unsigned char *chars, const char *flags, size_t size)
311 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
313 unsigned long __flags;
314 struct tty_buffer *tb;
316 spin_lock_irqsave(&tty->buf.lock, __flags);
317 space = __tty_buffer_request_room(tty, goal);
319 /* If there is no space then tb may be NULL */
320 if (unlikely(space == 0)) {
321 spin_unlock_irqrestore(&tty->buf.lock, __flags);
324 memcpy(tb->char_buf_ptr + tb->used, chars, space);
325 memcpy(tb->flag_buf_ptr + tb->used, flags, space);
327 spin_unlock_irqrestore(&tty->buf.lock, __flags);
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));
336 EXPORT_SYMBOL(tty_insert_flip_string_flags);
339 * tty_schedule_flip - push characters to ldisc
340 * @tty: tty to push from
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.
346 * Locking: Takes tty->buf.lock
349 void tty_schedule_flip(struct tty_struct *tty)
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);
356 schedule_work(&tty->buf.work);
358 EXPORT_SYMBOL(tty_schedule_flip);
361 * tty_prepare_flip_string - make room for characters
363 * @chars: return pointer for character write area
364 * @size: desired size
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!
372 * Locking: May call functions taking tty->buf.lock
375 int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
380 struct tty_buffer *tb;
382 spin_lock_irqsave(&tty->buf.lock, flags);
383 space = __tty_buffer_request_room(tty, size);
387 *chars = tb->char_buf_ptr + tb->used;
388 memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
391 spin_unlock_irqrestore(&tty->buf.lock, flags);
394 EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
397 * tty_prepare_flip_string_flags - make room for characters
399 * @chars: return pointer for character write area
400 * @flags: return pointer for status flag write area
401 * @size: desired size
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!
409 * Locking: May call functions taking tty->buf.lock
412 int tty_prepare_flip_string_flags(struct tty_struct *tty,
413 unsigned char **chars, char **flags, size_t size)
416 unsigned long __flags;
417 struct tty_buffer *tb;
419 spin_lock_irqsave(&tty->buf.lock, __flags);
420 space = __tty_buffer_request_room(tty, size);
424 *chars = tb->char_buf_ptr + tb->used;
425 *flags = tb->flag_buf_ptr + tb->used;
428 spin_unlock_irqrestore(&tty->buf.lock, __flags);
431 EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
437 * @work: tty structure passed from work queue.
439 * This routine is called out of the software interrupt to flush data
440 * from the buffer chain to the line discipline.
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.
447 static void flush_to_ldisc(struct work_struct *work)
449 struct tty_struct *tty =
450 container_of(work, struct tty_struct, buf.work);
452 struct tty_ldisc *disc;
454 disc = tty_ldisc_ref(tty);
455 if (disc == NULL) /* !TTY_LDISC */
458 spin_lock_irqsave(&tty->buf.lock, flags);
460 if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {
461 struct tty_buffer *head;
462 while ((head = tty->buf.head) != NULL) {
465 unsigned char *flag_buf;
467 count = head->commit - head->read;
469 if (head->next == NULL)
471 tty->buf.head = head->next;
472 tty_buffer_free(tty, head);
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))
480 if (!tty->receive_room)
482 if (count > tty->receive_room)
483 count = tty->receive_room;
484 char_buf = head->char_buf_ptr + head->read;
485 flag_buf = head->flag_buf_ptr + head->read;
487 spin_unlock_irqrestore(&tty->buf.lock, flags);
488 disc->ops->receive_buf(tty, char_buf,
490 spin_lock_irqsave(&tty->buf.lock, flags);
492 clear_bit(TTY_FLUSHING, &tty->flags);
495 /* 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);
502 spin_unlock_irqrestore(&tty->buf.lock, flags);
504 tty_ldisc_deref(disc);
511 * Push the terminal flip buffers to the line discipline.
513 * Must not be called from IRQ context.
515 void tty_flush_to_ldisc(struct tty_struct *tty)
517 flush_work(&tty->buf.work);
521 * tty_flip_buffer_push - terminal
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.
527 * In the event of the queue being busy for flipping the work will be
528 * held off and retried later.
530 * Locking: tty buffer lock. Driver locks in low latency mode.
533 void tty_flip_buffer_push(struct tty_struct *tty)
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);
541 if (tty->low_latency)
542 flush_to_ldisc(&tty->buf.work);
544 schedule_work(&tty->buf.work);
546 EXPORT_SYMBOL(tty_flip_buffer_push);
549 * tty_buffer_init - prepare a tty buffer structure
550 * @tty: tty to initialise
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.
558 void tty_buffer_init(struct tty_struct *tty)
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;
565 INIT_WORK(&tty->buf.work, flush_to_ldisc);