Root/drivers/tty/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
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 * __tty_buffer_request_room - grow tty buffer if needed
190 * @tty: tty structure
191 * @size: size desired
192 *
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
196 */
197static int __tty_buffer_request_room(struct tty_struct *tty, size_t size)
198{
199    struct tty_buffer *b, *n;
200    int left;
201    /* OPTIMISATION: We could keep a per tty "zero" sized buffer to
202       remove this conditional if its worth it. This would be invisible
203       to the callers */
204    if ((b = tty->buf.tail) != NULL)
205        left = b->size - b->used;
206    else
207        left = 0;
208
209    if (left < size) {
210        /* This is the slow path - looking for new buffers to use */
211        if ((n = tty_buffer_find(tty, size)) != NULL) {
212            if (b != NULL) {
213                b->next = n;
214                b->commit = b->used;
215            } else
216                tty->buf.head = n;
217            tty->buf.tail = n;
218        } else
219            size = left;
220    }
221
222    return size;
223}
224
225
226/**
227 * tty_buffer_request_room - grow tty buffer if needed
228 * @tty: tty structure
229 * @size: size desired
230 *
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.
233 *
234 * Locking: Takes tty->buf.lock
235 */
236int tty_buffer_request_room(struct tty_struct *tty, size_t size)
237{
238    unsigned long flags;
239    int length;
240
241    spin_lock_irqsave(&tty->buf.lock, flags);
242    length = __tty_buffer_request_room(tty, size);
243    spin_unlock_irqrestore(&tty->buf.lock, flags);
244    return length;
245}
246EXPORT_SYMBOL_GPL(tty_buffer_request_room);
247
248/**
249 * tty_insert_flip_string_fixed_flag - Add characters to the tty buffer
250 * @tty: tty structure
251 * @chars: characters
252 * @flag: flag value for each character
253 * @size: size
254 *
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.
257 *
258 * Locking: Called functions may take tty->buf.lock
259 */
260
261int tty_insert_flip_string_fixed_flag(struct tty_struct *tty,
262        const unsigned char *chars, char flag, size_t size)
263{
264    int copied = 0;
265    do {
266        int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
267        int space;
268        unsigned long flags;
269        struct tty_buffer *tb;
270
271        spin_lock_irqsave(&tty->buf.lock, flags);
272        space = __tty_buffer_request_room(tty, goal);
273        tb = tty->buf.tail;
274        /* If there is no space then tb may be NULL */
275        if (unlikely(space == 0)) {
276            spin_unlock_irqrestore(&tty->buf.lock, flags);
277            break;
278        }
279        memcpy(tb->char_buf_ptr + tb->used, chars, space);
280        memset(tb->flag_buf_ptr + tb->used, flag, space);
281        tb->used += space;
282        spin_unlock_irqrestore(&tty->buf.lock, flags);
283        copied += space;
284        chars += space;
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));
288    return copied;
289}
290EXPORT_SYMBOL(tty_insert_flip_string_fixed_flag);
291
292/**
293 * tty_insert_flip_string_flags - Add characters to the tty buffer
294 * @tty: tty structure
295 * @chars: characters
296 * @flags: flag bytes
297 * @size: size
298 *
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
301 * number added.
302 *
303 * Locking: Called functions may take tty->buf.lock
304 */
305
306int tty_insert_flip_string_flags(struct tty_struct *tty,
307        const unsigned char *chars, const char *flags, size_t size)
308{
309    int copied = 0;
310    do {
311        int goal = min_t(size_t, size - copied, TTY_BUFFER_PAGE);
312        int space;
313        unsigned long __flags;
314        struct tty_buffer *tb;
315
316        spin_lock_irqsave(&tty->buf.lock, __flags);
317        space = __tty_buffer_request_room(tty, goal);
318        tb = tty->buf.tail;
319        /* If there is no space then tb may be NULL */
320        if (unlikely(space == 0)) {
321            spin_unlock_irqrestore(&tty->buf.lock, __flags);
322            break;
323        }
324        memcpy(tb->char_buf_ptr + tb->used, chars, space);
325        memcpy(tb->flag_buf_ptr + tb->used, flags, space);
326        tb->used += space;
327        spin_unlock_irqrestore(&tty->buf.lock, __flags);
328        copied += space;
329        chars += space;
330        flags += space;
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));
334    return copied;
335}
336EXPORT_SYMBOL(tty_insert_flip_string_flags);
337
338/**
339 * tty_schedule_flip - push characters to ldisc
340 * @tty: tty to push from
341 *
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.
345 *
346 * Locking: Takes tty->buf.lock
347 */
348
349void tty_schedule_flip(struct tty_struct *tty)
350{
351    unsigned long flags;
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);
357}
358EXPORT_SYMBOL(tty_schedule_flip);
359
360/**
361 * tty_prepare_flip_string - make room for characters
362 * @tty: tty
363 * @chars: return pointer for character write area
364 * @size: desired size
365 *
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!
371 *
372 * Locking: May call functions taking tty->buf.lock
373 */
374
375int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars,
376                                size_t size)
377{
378    int space;
379    unsigned long flags;
380    struct tty_buffer *tb;
381
382    spin_lock_irqsave(&tty->buf.lock, flags);
383    space = __tty_buffer_request_room(tty, size);
384
385    tb = tty->buf.tail;
386    if (likely(space)) {
387        *chars = tb->char_buf_ptr + tb->used;
388        memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
389        tb->used += space;
390    }
391    spin_unlock_irqrestore(&tty->buf.lock, flags);
392    return space;
393}
394EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
395
396/**
397 * tty_prepare_flip_string_flags - make room for characters
398 * @tty: tty
399 * @chars: return pointer for character write area
400 * @flags: return pointer for status flag write area
401 * @size: desired size
402 *
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!
408 *
409 * Locking: May call functions taking tty->buf.lock
410 */
411
412int tty_prepare_flip_string_flags(struct tty_struct *tty,
413            unsigned char **chars, char **flags, size_t size)
414{
415    int space;
416    unsigned long __flags;
417    struct tty_buffer *tb;
418
419    spin_lock_irqsave(&tty->buf.lock, __flags);
420    space = __tty_buffer_request_room(tty, size);
421
422    tb = tty->buf.tail;
423    if (likely(space)) {
424        *chars = tb->char_buf_ptr + tb->used;
425        *flags = tb->flag_buf_ptr + tb->used;
426        tb->used += space;
427    }
428    spin_unlock_irqrestore(&tty->buf.lock, __flags);
429    return space;
430}
431EXPORT_SYMBOL_GPL(tty_prepare_flip_string_flags);
432
433
434
435/**
436 * flush_to_ldisc
437 * @work: tty structure passed from work queue.
438 *
439 * This routine is called out of the software interrupt to flush data
440 * from the buffer chain to the line discipline.
441 *
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.
445 */
446
447static void flush_to_ldisc(struct work_struct *work)
448{
449    struct tty_struct *tty =
450        container_of(work, struct tty_struct, buf.work);
451    unsigned long flags;
452    struct tty_ldisc *disc;
453
454    disc = tty_ldisc_ref(tty);
455    if (disc == NULL) /* !TTY_LDISC */
456        return;
457
458    spin_lock_irqsave(&tty->buf.lock, flags);
459
460    if (!test_and_set_bit(TTY_FLUSHING, &tty->flags)) {
461        struct tty_buffer *head;
462        while ((head = tty->buf.head) != NULL) {
463            int count;
464            char *char_buf;
465            unsigned char *flag_buf;
466
467            count = head->commit - head->read;
468            if (!count) {
469                if (head->next == NULL)
470                    break;
471                tty->buf.head = head->next;
472                tty_buffer_free(tty, head);
473                continue;
474            }
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))
479                break;
480            if (!tty->receive_room)
481                break;
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;
486            head->read += count;
487            spin_unlock_irqrestore(&tty->buf.lock, flags);
488            disc->ops->receive_buf(tty, char_buf,
489                            flag_buf, count);
490            spin_lock_irqsave(&tty->buf.lock, flags);
491        }
492        clear_bit(TTY_FLUSHING, &tty->flags);
493    }
494
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);
501    }
502    spin_unlock_irqrestore(&tty->buf.lock, flags);
503
504    tty_ldisc_deref(disc);
505}
506
507/**
508 * tty_flush_to_ldisc
509 * @tty: tty to push
510 *
511 * Push the terminal flip buffers to the line discipline.
512 *
513 * Must not be called from IRQ context.
514 */
515void tty_flush_to_ldisc(struct tty_struct *tty)
516{
517    flush_work(&tty->buf.work);
518}
519
520/**
521 * tty_flip_buffer_push - terminal
522 * @tty: tty to push
523 *
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.
526 *
527 * In the event of the queue being busy for flipping the work will be
528 * held off and retried later.
529 *
530 * Locking: tty buffer lock. Driver locks in low latency mode.
531 */
532
533void tty_flip_buffer_push(struct tty_struct *tty)
534{
535    unsigned long flags;
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);
540
541    if (tty->low_latency)
542        flush_to_ldisc(&tty->buf.work);
543    else
544        schedule_work(&tty->buf.work);
545}
546EXPORT_SYMBOL(tty_flip_buffer_push);
547
548/**
549 * tty_buffer_init - prepare a tty buffer structure
550 * @tty: tty to initialise
551 *
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.
554 *
555 * Locking: none
556 */
557
558void tty_buffer_init(struct tty_struct *tty)
559{
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);
566}
567
568

Archive Download this file

Branches:
ben-wpan
ben-wpan-stefan
javiroman/ks7010
jz-2.6.34
jz-2.6.34-rc5
jz-2.6.34-rc6
jz-2.6.34-rc7
jz-2.6.35
jz-2.6.36
jz-2.6.37
jz-2.6.38
jz-2.6.39
jz-3.0
jz-3.1
jz-3.11
jz-3.12
jz-3.13
jz-3.15
jz-3.16
jz-3.18-dt
jz-3.2
jz-3.3
jz-3.4
jz-3.5
jz-3.6
jz-3.6-rc2-pwm
jz-3.9
jz-3.9-clk
jz-3.9-rc8
jz47xx
jz47xx-2.6.38
master

Tags:
od-2011-09-04
od-2011-09-18
v2.6.34-rc5
v2.6.34-rc6
v2.6.34-rc7
v3.9



interactive