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) {
54 llist = llist_del_all(&buf->free);
55 llist_for_each_entry_safe(p, next, llist, free)
63 * tty_buffer_alloc - allocate a tty buffer
65 * @size: desired size (characters)
67 * Allocate a new tty buffer to hold the desired number of characters.
68 * We round our buffers off in 256 character chunks to get better
69 * allocation behaviour.
70 * Return NULL if out of memory or the allocation would exceed the
74 static struct tty_buffer *tty_buffer_alloc(struct tty_port *port, size_t size)
76 struct llist_node *free;
79 /* Round the buffer size out */
80 size = __ALIGN_MASK(size, TTYB_ALIGN_MASK);
82 if (size <= MIN_TTYB_SIZE) {
83 free = llist_del_first(&port->buf.free);
85 p = llist_entry(free, struct tty_buffer, free);
90 /* Should possibly check if this fails for the largest buffer we
91 have queued and recycle that ? */
92 if (port->buf.memory_used + size > 65536)
94 p = kmalloc(sizeof(struct tty_buffer) + 2 * size, GFP_ATOMIC);
99 tty_buffer_reset(p, size);
100 port->buf.memory_used += size;
105 * tty_buffer_free - free a tty buffer
106 * @tty: tty owning the buffer
107 * @b: the buffer to free
109 * Free a tty buffer, or add it to the free list according to our
113 static void tty_buffer_free(struct tty_port *port, struct tty_buffer *b)
115 struct tty_bufhead *buf = &port->buf;
117 /* Dumb strategy for now - should keep some stats */
118 buf->memory_used -= b->size;
119 WARN_ON(buf->memory_used < 0);
121 if (b->size > MIN_TTYB_SIZE)
124 llist_add(&b->free, &buf->free);
128 * __tty_buffer_flush - flush full tty buffers
131 * flush all the buffers containing receive data. Caller must
132 * hold the buffer lock and must have ensured no parallel flush to
135 * Locking: Caller must hold tty->buf.lock
138 static void __tty_buffer_flush(struct tty_port *port)
140 struct tty_bufhead *buf = &port->buf;
141 struct tty_buffer *next;
143 if (unlikely(buf->head == NULL))
145 while ((next = buf->head->next) != NULL) {
146 tty_buffer_free(port, buf->head);
149 WARN_ON(buf->head != buf->tail);
150 buf->head->read = buf->head->commit;
154 * tty_buffer_flush - flush full tty buffers
157 * flush all the buffers containing receive data. If the buffer is
158 * being processed by flush_to_ldisc then we defer the processing
164 void tty_buffer_flush(struct tty_struct *tty)
166 struct tty_port *port = tty->port;
167 struct tty_bufhead *buf = &port->buf;
170 spin_lock_irqsave(&buf->lock, flags);
172 /* If the data is being pushed to the tty layer then we can't
173 process it here. Instead set a flag and the flush_to_ldisc
174 path will process the flush request before it exits */
175 if (test_bit(TTYP_FLUSHING, &port->iflags)) {
176 set_bit(TTYP_FLUSHPENDING, &port->iflags);
177 spin_unlock_irqrestore(&buf->lock, flags);
178 wait_event(tty->read_wait,
179 test_bit(TTYP_FLUSHPENDING, &port->iflags) == 0);
182 __tty_buffer_flush(port);
183 spin_unlock_irqrestore(&buf->lock, flags);
187 * tty_buffer_request_room - grow tty buffer if needed
188 * @tty: tty structure
189 * @size: size desired
191 * Make at least size bytes of linear space available for the tty
192 * buffer. If we fail return the size we managed to find.
194 * Locking: Takes port->buf.lock
196 int tty_buffer_request_room(struct tty_port *port, size_t size)
198 struct tty_bufhead *buf = &port->buf;
199 struct tty_buffer *b, *n;
202 spin_lock_irqsave(&buf->lock, flags);
203 /* OPTIMISATION: We could keep a per tty "zero" sized buffer to
204 remove this conditional if its worth it. This would be invisible
208 left = b->size - b->used;
213 /* This is the slow path - looking for new buffers to use */
214 if ((n = tty_buffer_alloc(port, size)) != NULL) {
224 spin_unlock_irqrestore(&buf->lock, flags);
227 EXPORT_SYMBOL_GPL(tty_buffer_request_room);
230 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
233 * @flag: flag value for each character
236 * Queue a series of bytes to the tty buffering. All the characters
237 * passed are marked with the supplied flag. Returns the number added.
239 * Locking: Called functions may take port->buf.lock
242 int tty_insert_flip_string_fixed_flag(struct tty_port *port,
243 const unsigned char *chars, char flag, size_t size)
247 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
248 int space = tty_buffer_request_room(port, goal);
249 struct tty_buffer *tb = port->buf.tail;
250 /* If there is no space then tb may be NULL */
251 if (unlikely(space == 0)) {
254 memcpy(char_buf_ptr(tb, tb->used), chars, space);
255 memset(flag_buf_ptr(tb, tb->used), flag, space);
259 /* There is a small chance that we need to split the data over
260 several buffers. If this is the case we must loop */
261 } while (unlikely(size > copied));
264 EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
267 * tty_insert_flip_string_flags - Add characters to the tty buffer
273 * Queue a series of bytes to the tty buffering. For each character
274 * the flags array indicates the status of the character. Returns the
277 * Locking: Called functions may take port->buf.lock
280 int tty_insert_flip_string_flags(struct tty_port *port,
281 const unsigned char *chars, const char *flags, size_t size)
285 int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
286 int space = tty_buffer_request_room(port, goal);
287 struct tty_buffer *tb = port->buf.tail;
288 /* If there is no space then tb may be NULL */
289 if (unlikely(space == 0)) {
292 memcpy(char_buf_ptr(tb, tb->used), chars, space);
293 memcpy(flag_buf_ptr(tb, tb->used), flags, space);
298 /* There is a small chance that we need to split the data over
299 several buffers. If this is the case we must loop */
300 } while (unlikely(size > copied));
303 EXPORT_SYMBOL(tty_insert_flip_string_flags);
306 * tty_schedule_flip - push characters to ldisc
307 * @port: tty port to push from
309 * Takes any pending buffers and transfers their ownership to the
310 * ldisc side of the queue. It then schedules those characters for
311 * processing by the line discipline.
312 * Note that this function can only be used when the low_latency flag
313 * is unset. Otherwise the workqueue won't be flushed.
315 * Locking: Takes port->buf.lock
318 void tty_schedule_flip(struct tty_port *port)
320 struct tty_bufhead *buf = &port->buf;
322 WARN_ON(port->low_latency);
324 spin_lock_irqsave(&buf->lock, flags);
325 if (buf->tail != NULL)
326 buf->tail->commit = buf->tail->used;
327 spin_unlock_irqrestore(&buf->lock, flags);
328 schedule_work(&buf->work);
330 EXPORT_SYMBOL(tty_schedule_flip);
333 * tty_prepare_flip_string - make room for characters
335 * @chars: return pointer for character write area
336 * @size: desired size
338 * Prepare a block of space in the buffer for data. Returns the length
339 * available and buffer pointer to the space which is now allocated and
340 * accounted for as ready for normal characters. This is used for drivers
341 * that need their own block copy routines into the buffer. There is no
342 * guarantee the buffer is a DMA target!
344 * Locking: May call functions taking port->buf.lock
347 int tty_prepare_flip_string(struct tty_port *port, unsigned char **chars,
350 int space = tty_buffer_request_room(port, size);
352 struct tty_buffer *tb = port->buf.tail;
353 *chars = char_buf_ptr(tb, tb->used);
354 memset(flag_buf_ptr(tb, tb->used), TTY_NORMAL, space);
359 EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
362 * tty_prepare_flip_string_flags - make room for characters
364 * @chars: return pointer for character write area
365 * @flags: return pointer for status flag write area
366 * @size: desired size
368 * Prepare a block of space in the buffer for data. Returns the length
369 * available and buffer pointer to the space which is now allocated and
370 * accounted for as ready for characters. This is used for drivers
371 * that need their own block copy routines into the buffer. There is no
372 * guarantee the buffer is a DMA target!
374 * Locking: May call functions taking port->buf.lock
377 int tty_prepare_flip_string_flags(struct tty_port *port,
378 unsigned char **chars, char **flags, size_t size)
380 int space = tty_buffer_request_room(port, size);
382 struct tty_buffer *tb = port->buf.tail;
383 *chars = char_buf_ptr(tb, tb->used);
384 *flags = flag_buf_ptr(tb, tb->used);
389 EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
393 receive_buf(struct tty_struct *tty, struct tty_buffer *head, int count)
395 struct tty_ldisc *disc = tty->ldisc;
396 unsigned char *p = char_buf_ptr(head, head->read);
397 char *f = flag_buf_ptr(head, head->read);
399 if (disc->ops->receive_buf2)
400 count = disc->ops->receive_buf2(tty, p, f, count);
402 count = min_t(int, count, tty->receive_room);
404 disc->ops->receive_buf(tty, p, f, count);
412 * @work: tty structure passed from work queue.
414 * This routine is called out of the software interrupt to flush data
415 * from the buffer chain to the line discipline.
417 * Locking: holds tty->buf.lock to guard buffer list. Drops the lock
418 * while invoking the line discipline receive_buf method. The
419 * receive_buf method is single threaded for each tty instance.
422 static void flush_to_ldisc(struct work_struct *work)
424 struct tty_port *port = container_of(work, struct tty_port, buf.work);
425 struct tty_bufhead *buf = &port->buf;
426 struct tty_struct *tty;
428 struct tty_ldisc *disc;
434 disc = tty_ldisc_ref(tty);
438 spin_lock_irqsave(&buf->lock, flags);
440 if (!test_and_set_bit(TTYP_FLUSHING, &port->iflags)) {
441 struct tty_buffer *head;
442 while ((head = buf->head) != NULL) {
445 count = head->commit - head->read;
447 if (head->next == NULL)
449 buf->head = head->next;
450 tty_buffer_free(port, head);
453 spin_unlock_irqrestore(&buf->lock, flags);
455 count = receive_buf(tty, head, count);
457 spin_lock_irqsave(&buf->lock, flags);
458 /* Ldisc or user is trying to flush the buffers.
459 We may have a deferred request to flush the
460 input buffer, if so pull the chain under the lock
461 and empty the queue */
462 if (test_bit(TTYP_FLUSHPENDING, &port->iflags)) {
463 __tty_buffer_flush(port);
464 clear_bit(TTYP_FLUSHPENDING, &port->iflags);
465 wake_up(&tty->read_wait);
470 clear_bit(TTYP_FLUSHING, &port->iflags);
473 spin_unlock_irqrestore(&buf->lock, flags);
475 tty_ldisc_deref(disc);
482 * Push the terminal flip buffers to the line discipline.
484 * Must not be called from IRQ context.
486 void tty_flush_to_ldisc(struct tty_struct *tty)
488 if (!tty->port->low_latency)
489 flush_work(&tty->port->buf.work);
493 * tty_flip_buffer_push - terminal
494 * @port: tty port to push
496 * Queue a push of the terminal flip buffers to the line discipline. This
497 * function must not be called from IRQ context if port->low_latency is
500 * In the event of the queue being busy for flipping the work will be
501 * held off and retried later.
503 * Locking: tty buffer lock. Driver locks in low latency mode.
506 void tty_flip_buffer_push(struct tty_port *port)
508 struct tty_bufhead *buf = &port->buf;
511 spin_lock_irqsave(&buf->lock, flags);
512 if (buf->tail != NULL)
513 buf->tail->commit = buf->tail->used;
514 spin_unlock_irqrestore(&buf->lock, flags);
516 if (port->low_latency)
517 flush_to_ldisc(&buf->work);
519 schedule_work(&buf->work);
521 EXPORT_SYMBOL(tty_flip_buffer_push);
524 * tty_buffer_init - prepare a tty buffer structure
525 * @tty: tty to initialise
527 * Set up the initial state of the buffer management for a tty device.
528 * Must be called before the other tty buffer functions are used.
533 void tty_buffer_init(struct tty_port *port)
535 struct tty_bufhead *buf = &port->buf;
537 spin_lock_init(&buf->lock);
540 init_llist_head(&buf->free);
541 buf->memory_used = 0;
542 INIT_WORK(&buf->work, flush_to_ldisc);