Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes...
[linux-2.6.git] / drivers / char / tty_buffer.c
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
30 void 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
57 static 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
88 static 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
113 static 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
135 void 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
166 static 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  */
199 int 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 }
231 EXPORT_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 as without error. Returns the number added.
242  *
243  *      Locking: Called functions may take tty->buf.lock
244  */
245
246 int 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 }
267 EXPORT_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
283 int 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 }
305 EXPORT_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
318 void 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_delayed_work(&tty->buf.work, 1);
326 }
327 EXPORT_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
344 int 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 }
356 EXPORT_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
374 int 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 }
386 EXPORT_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
402 static void flush_to_ldisc(struct work_struct *work)
403 {
404         struct tty_struct *tty =
405                 container_of(work, struct tty_struct, buf.work.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                                 schedule_delayed_work(&tty->buf.work, 1);
437                                 break;
438                         }
439                         if (count > tty->receive_room)
440                                 count = tty->receive_room;
441                         char_buf = head->char_buf_ptr + head->read;
442                         flag_buf = head->flag_buf_ptr + head->read;
443                         head->read += count;
444                         spin_unlock_irqrestore(&tty->buf.lock, flags);
445                         disc->ops->receive_buf(tty, char_buf,
446                                                         flag_buf, count);
447                         spin_lock_irqsave(&tty->buf.lock, flags);
448                 }
449                 clear_bit(TTY_FLUSHING, &tty->flags);
450         }
451
452         /* We may have a deferred request to flush the input buffer,
453            if so pull the chain under the lock and empty the queue */
454         if (test_bit(TTY_FLUSHPENDING, &tty->flags)) {
455                 __tty_buffer_flush(tty);
456                 clear_bit(TTY_FLUSHPENDING, &tty->flags);
457                 wake_up(&tty->read_wait);
458         }
459         spin_unlock_irqrestore(&tty->buf.lock, flags);
460
461         tty_ldisc_deref(disc);
462 }
463
464 /**
465  *      tty_flush_to_ldisc
466  *      @tty: tty to push
467  *
468  *      Push the terminal flip buffers to the line discipline.
469  *
470  *      Must not be called from IRQ context.
471  */
472 void tty_flush_to_ldisc(struct tty_struct *tty)
473 {
474         flush_delayed_work(&tty->buf.work);
475 }
476
477 /**
478  *      tty_flip_buffer_push    -       terminal
479  *      @tty: tty to push
480  *
481  *      Queue a push of the terminal flip buffers to the line discipline. This
482  *      function must not be called from IRQ context if tty->low_latency is set.
483  *
484  *      In the event of the queue being busy for flipping the work will be
485  *      held off and retried later.
486  *
487  *      Locking: tty buffer lock. Driver locks in low latency mode.
488  */
489
490 void tty_flip_buffer_push(struct tty_struct *tty)
491 {
492         unsigned long flags;
493         spin_lock_irqsave(&tty->buf.lock, flags);
494         if (tty->buf.tail != NULL)
495                 tty->buf.tail->commit = tty->buf.tail->used;
496         spin_unlock_irqrestore(&tty->buf.lock, flags);
497
498         if (tty->low_latency)
499                 flush_to_ldisc(&tty->buf.work.work);
500         else
501                 schedule_delayed_work(&tty->buf.work, 1);
502 }
503 EXPORT_SYMBOL(tty_flip_buffer_push);
504
505 /**
506  *      tty_buffer_init         -       prepare a tty buffer structure
507  *      @tty: tty to initialise
508  *
509  *      Set up the initial state of the buffer management for a tty device.
510  *      Must be called before the other tty buffer functions are used.
511  *
512  *      Locking: none
513  */
514
515 void tty_buffer_init(struct tty_struct *tty)
516 {
517         spin_lock_init(&tty->buf.lock);
518         tty->buf.head = NULL;
519         tty->buf.tail = NULL;
520         tty->buf.free = NULL;
521         tty->buf.memory_used = 0;
522         INIT_DELAYED_WORK(&tty->buf.work, flush_to_ldisc);
523 }
524