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>
19 #include <linux/ratelimit.h>
22 #define MIN_TTYB_SIZE 256
23 #define TTYB_ALIGN_MASK 255
25 static void tty_buffer_reset(struct tty_buffer *p, size_t size)
35 * tty_buffer_free_all - free buffers used by a tty
36 * @tty: tty to free from
38 * Remove all the buffers pending on a tty whether queued with data
39 * or in the free ring. Must be called when the tty is no longer in use
44 void tty_buffer_free_all(struct tty_port *port)
46 struct tty_bufhead *buf = &port->buf;
47 struct tty_buffer *p, *next;
48 struct llist_node *llist;
50 while ((p = buf->head) != NULL) {
55 llist = llist_del_all(&buf->free);
56 llist_for_each_entry_safe(p, next, llist, free)
59 tty_buffer_reset(&buf->sentinel, 0);
60 buf->head = &buf->sentinel;
61 buf->tail = &buf->sentinel;
66 * tty_buffer_alloc - allocate a tty buffer
68 * @size: desired size (characters)
70 * Allocate a new tty buffer to hold the desired number of characters.
71 * We round our buffers off in 256 character chunks to get better
72 * allocation behaviour.
73 * Return NULL if out of memory or the allocation would exceed the
77 static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
79 struct llist_node *free;
82 /* Round the buffer size out */
83 size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
85 if (size <= MIN_TTYB_SIZE) {
86 free = llist_del_first(&port->buf.free);
88 p = llist_entry(free, struct tty_buffer, free);
93 /* Should possibly check if this fails for the largest buffer we
94 have queued and recycle that ? */
95 if (port->buf.memory_used + size > 65536)
97 p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
102 tty_buffer_reset(p, size);
103 port->buf.memory_used += size;
108 * tty_buffer_free - free a tty buffer
109 * @tty: tty owning the buffer
110 * @b: the buffer to free
112 * Free a tty buffer, or add it to the free list according to our
116 static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
118 struct tty_bufhead *buf = &port->buf;
120 /* Dumb strategy for now - should keep some stats */
121 buf->memory_used -= b->size;
122 WARN_ON(buf->memory_used < 0);
124 if (b->size > MIN_TTYB_SIZE)
126 else if (b->size > 0)
127 llist_add(&b->free, &buf->free);
131 * __tty_buffer_flush - flush full tty buffers
134 * flush all the buffers containing receive data. Caller must
135 * hold the buffer lock and must have ensured no parallel flush to
138 * Locking: Caller must hold tty->buf.lock
141 static void __tty_buffer_flush(struct tty_port *port)
143 struct tty_bufhead *buf = &port->buf;
144 struct tty_buffer *next;
146 while ((next = buf->head->next) != NULL) {
147 tty_buffer_free(port, buf->head);
150 WARN_ON(buf->head != buf->tail);
151 buf->head->read = buf->head->commit;
155 * tty_buffer_flush - flush full tty buffers
158 * flush all the buffers containing receive data. If the buffer is
159 * being processed by flush_to_ldisc then we defer the processing
165 void tty_buffer_flush(struct tty_struct *tty)
167 struct tty_port *port = tty->port;
168 struct tty_bufhead *buf = &port->buf;
171 spin_lock_irqsave(&buf->lock, flags);
173 /* If the data is being pushed to the tty layer then we can't
174 process it here. Instead set a flag and the flush_to_ldisc
175 path will process the flush request before it exits */
176 if (test_bit(TTYP_FLUSHING, &port->iflags)) {
177 set_bit(TTYP_FLUSHPENDING, &port->iflags);
178 spin_unlock_irqrestore(&buf->lock, flags);
179 wait_event(tty->read_wait,
180 test_bit(TTYP_FLUSHPENDING, &port->iflags) == 0);
183 __tty_buffer_flush(port);
184 spin_unlock_irqrestore(&buf->lock, flags);
188 * tty_buffer_request_room - grow tty buffer if needed
189 * @tty: tty structure
190 * @size: size desired
192 * Make at least size bytes of linear space available for the tty
193 * buffer. If we fail return the size we managed to find.
195 * Locking: Takes port->buf.lock
197 int tty_buffer_request_room(struct tty_port *port, size_t size)
199 struct tty_bufhead *buf = &port->buf;
200 struct tty_buffer *b, *n;
203 spin_lock_irqsave(&buf->lock, flags);
205 left = b->size - b->used;
208 /* This is the slow path - looking for new buffers to use */
209 if ((n = tty_buffer_alloc(port, size)) != NULL) {
216 spin_unlock_irqrestore(&buf->lock, flags);
219 EXPORT_SYMBOL_GPL(tty_buffer_request_room);
222 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
225 * @flag: flag value for each character
228 * Queue a series of bytes to the tty buffering. All the characters
229 * passed are marked with the supplied flag. Returns the number added.
231 * Locking: Called functions may take port->buf.lock
234 int tty_insert_flip_string_fixed_flag(struct tty_port *port,
235 const unsigned char *chars, char flag, size_t size)
239 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
240 int space = tty_buffer_request_room(port, goal);
241 struct tty_buffer *tb = port->buf.tail;
242 if (unlikely(space == 0))
244 memcpy(char_buf_ptr(tb, tb->used), chars, space);
245 memset(flag_buf_ptr(tb, tb->used), flag, space);
249 /* There is a small chance that we need to split the data over
250 several buffers. If this is the case we must loop */
251 } while (unlikely(size > copied));
254 EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
257 * tty_insert_flip_string_flags - Add characters to the tty buffer
263 * Queue a series of bytes to the tty buffering. For each character
264 * the flags array indicates the status of the character. Returns the
267 * Locking: Called functions may take port->buf.lock
270 int tty_insert_flip_string_flags(struct tty_port *port,
271 const unsigned char *chars, const char *flags, size_t size)
275 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
276 int space = tty_buffer_request_room(port, goal);
277 struct tty_buffer *tb = port->buf.tail;
278 if (unlikely(space == 0))
280 memcpy(char_buf_ptr(tb, tb->used), chars, space);
281 memcpy(flag_buf_ptr(tb, tb->used), flags, space);
286 /* There is a small chance that we need to split the data over
287 several buffers. If this is the case we must loop */
288 } while (unlikely(size > copied));
291 EXPORT_SYMBOL(tty_insert_flip_string_flags);
294 * tty_schedule_flip - push characters to ldisc
295 * @port: tty port to push from
297 * Takes any pending buffers and transfers their ownership to the
298 * ldisc side of the queue. It then schedules those characters for
299 * processing by the line discipline.
300 * Note that this function can only be used when the low_latency flag
301 * is unset. Otherwise the workqueue won't be flushed.
303 * Locking: Takes port->buf.lock
306 void tty_schedule_flip(struct tty_port *port)
308 struct tty_bufhead *buf = &port->buf;
310 WARN_ON(port->low_latency);
312 spin_lock_irqsave(&buf->lock, flags);
313 buf->tail->commit = buf->tail->used;
314 spin_unlock_irqrestore(&buf->lock, flags);
315 schedule_work(&buf->work);
317 EXPORT_SYMBOL(tty_schedule_flip);
320 * tty_prepare_flip_string - make room for characters
322 * @chars: return pointer for character write area
323 * @size: desired size
325 * Prepare a block of space in the buffer for data. Returns the length
326 * available and buffer pointer to the space which is now allocated and
327 * accounted for as ready for normal characters. This is used for drivers
328 * that need their own block copy routines into the buffer. There is no
329 * guarantee the buffer is a DMA target!
331 * Locking: May call functions taking port->buf.lock
334 int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
337 int space = tty_buffer_request_room(port, size);
339 struct tty_buffer *tb = port->buf.tail;
340 *chars = char_buf_ptr(tb, tb->used);
341 memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
346 EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
349 * tty_prepare_flip_string_flags - make room for characters
351 * @chars: return pointer for character write area
352 * @flags: return pointer for status flag write area
353 * @size: desired size
355 * Prepare a block of space in the buffer for data. Returns the length
356 * available and buffer pointer to the space which is now allocated and
357 * accounted for as ready for characters. This is used for drivers
358 * that need their own block copy routines into the buffer. There is no
359 * guarantee the buffer is a DMA target!
361 * Locking: May call functions taking port->buf.lock
364 int tty_prepare_flip_string_flags(struct tty_port *port,
365 unsigned char **chars, char **flags, size_t size)
367 int space = tty_buffer_request_room(port, size);
369 struct tty_buffer *tb = port->buf.tail;
370 *chars = char_buf_ptr(tb, tb->used);
371 *flags = flag_buf_ptr(tb, tb->used);
376 EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
380 receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
382 struct tty_ldisc *disc = tty->ldisc;
383 unsigned char *p = char_buf_ptr(head, head->read);
384 char *f = flag_buf_ptr(head, head->read);
386 if (disc->ops->receive_buf2)
387 count = disc->ops->receive_buf2(tty, p, f, count);
389 count = min_t(int, count, tty->receive_room);
391 disc->ops->receive_buf(tty, p, f, count);
399 * @work: tty structure passed from work queue.
401 * This routine is called out of the software interrupt to flush data
402 * from the buffer chain to the line discipline.
404 * Locking: holds tty->buf.lock to guard buffer list. Drops the lock
405 * while invoking the line discipline receive_buf method. The
406 * receive_buf method is single threaded for each tty instance.
409 static void flush_to_ldisc(struct work_struct *work)
411 struct tty_port *port = container_of(work, struct tty_port, buf.work);
412 struct tty_bufhead *buf = &port->buf;
413 struct tty_struct *tty;
415 struct tty_ldisc *disc;
421 disc = tty_ldisc_ref(tty);
425 spin_lock_irqsave(&buf->lock, flags);
427 if (!test_and_set_bit(TTYP_FLUSHING, &port->iflags)) {
429 struct tty_buffer *head = buf->head;
432 count = head->commit - head->read;
434 if (head->next == NULL)
436 buf->head = head->next;
437 tty_buffer_free(port, head);
440 spin_unlock_irqrestore(&buf->lock, flags);
442 count = receive_buf(tty, head, count);
444 spin_lock_irqsave(&buf->lock, flags);
445 /* Ldisc or user is trying to flush the buffers.
446 We may have a deferred request to flush the
447 input buffer, if so pull the chain under the lock
448 and empty the queue */
449 if (test_bit(TTYP_FLUSHPENDING, &port->iflags)) {
450 __tty_buffer_flush(port);
451 clear_bit(TTYP_FLUSHPENDING, &port->iflags);
452 wake_up(&tty->read_wait);
457 clear_bit(TTYP_FLUSHING, &port->iflags);
460 spin_unlock_irqrestore(&buf->lock, flags);
462 tty_ldisc_deref(disc);
469 * Push the terminal flip buffers to the line discipline.
471 * Must not be called from IRQ context.
473 void tty_flush_to_ldisc(struct tty_struct *tty)
475 if (!tty->port->low_latency)
476 flush_work(&tty->port->buf.work);
480 * tty_flip_buffer_push - terminal
481 * @port: tty port to push
483 * Queue a push of the terminal flip buffers to the line discipline. This
484 * function must not be called from IRQ context if port->low_latency is
487 * In the event of the queue being busy for flipping the work will be
488 * held off and retried later.
490 * Locking: tty buffer lock. Driver locks in low latency mode.
493 void tty_flip_buffer_push(struct tty_port *port)
495 struct tty_bufhead *buf = &port->buf;
498 spin_lock_irqsave(&buf->lock, flags);
499 buf->tail->commit = buf->tail->used;
500 spin_unlock_irqrestore(&buf->lock, flags);
502 if (port->low_latency)
503 flush_to_ldisc(&buf->work);
505 schedule_work(&buf->work);
507 EXPORT_SYMBOL(tty_flip_buffer_push);
510 * tty_buffer_init - prepare a tty buffer structure
511 * @tty: tty to initialise
513 * Set up the initial state of the buffer management for a tty device.
514 * Must be called before the other tty buffer functions are used.
519 void tty_buffer_init(struct tty_port *port)
521 struct tty_bufhead *buf = &port->buf;
523 spin_lock_init(&buf->lock);
524 tty_buffer_reset(&buf->sentinel, 0);
525 buf->head = &buf->sentinel;
526 buf->tail = &buf->sentinel;
527 init_llist_head(&buf->free);
528 buf->memory_used = 0;
529 INIT_WORK(&buf->work, flush_to_ldisc);