1 /*
2 * n_tty.c --- implements the N_TTY line discipline.
3 *
4 * This code used to be in tty_io.c, but things are getting hairy
5 * enough that it made sense to split things off. (The N_TTY
6 * processing has changed so much that it's hardly recognizable,
7 * anyway...)
8 *
9 * Note that the open routine for N_TTY is guaranteed never to return
10 * an error. This is because Linux will fall back to setting a line
11 * to N_TTY if it can not switch to any other line discipline.
12 *
13 * Written by Theodore Ts'o, Copyright 1994.
14 *
15 * This file also contains code originally written by Linus Torvalds,
16 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
17 *
18 * This file may be redistributed under the terms of the GNU General Public
19 * License.
20 *
21 * Reduced memory usage for older ARM systems - Russell King.
22 *
23 * 2000/01/20 Fixed SMP locking on put_tty_queue using bits of
24 * the patch by Andrew J. Kroll <ag784@freenet.buffalo.edu>
25 * who actually finally proved there really was a race.
26 *
27 * 2002/03/18 Implemented n_tty_wakeup to send SIGIO POLL_OUTs to
28 * waiting writing processes-Sapan Bhatia <sapan@corewars.org>.
29 * Also fixed a bug in BLOCKING mode where write_chan returns
30 * EAGAIN
31 */
32
33 #include <linux/types.h>
34 #include <linux/major.h>
35 #include <linux/errno.h>
36 #include <linux/signal.h>
37 #include <linux/fcntl.h>
38 #include <linux/sched.h>
39 #include <linux/interrupt.h>
40 #include <linux/tty.h>
41 #include <linux/timer.h>
42 #include <linux/ctype.h>
43 #include <linux/mm.h>
44 #include <linux/string.h>
45 #include <linux/slab.h>
46 #include <linux/poll.h>
47 #include <linux/bitops.h>
48
49 #include <asm/uaccess.h>
50 #include <asm/system.h>
51
52 /* number of characters left in xmit buffer before select has we have room */
53 #define WAKEUP_CHARS 256
54
55 /*
56 * This defines the low- and high-watermarks for throttling and
57 * unthrottling the TTY driver. These watermarks are used for
58 * controlling the space in the read buffer.
59 */
60 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
61 #define TTY_THRESHOLD_UNTHROTTLE 128
62
63 static inline unsigned char *alloc_buf(void)
64 {
65 int prio = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
66
67 if (PAGE_SIZE != N_TTY_BUF_SIZE)
68 return kmalloc(N_TTY_BUF_SIZE, prio);
69 else
70 return (unsigned char *)__get_free_page(prio);
71 }
72
73 static inline void free_buf(unsigned char *buf)
74 {
75 if (PAGE_SIZE != N_TTY_BUF_SIZE)
76 kfree(buf);
77 else
78 free_page((unsigned long) buf);
79 }
80
81 static inline void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
82 {
83 if (tty->read_cnt < N_TTY_BUF_SIZE) {
84 tty->read_buf[tty->read_head] = c;
85 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
86 tty->read_cnt++;
87 }
88 }
89
90 static inline void put_tty_queue(unsigned char c, struct tty_struct *tty)
91 {
92 unsigned long flags;
93 /*
94 * The problem of stomping on the buffers ends here.
95 * Why didn't anyone see this one coming? --AJK
96 */
97 spin_lock_irqsave(&tty->read_lock, flags);
98 put_tty_queue_nolock(c, tty);
99 spin_unlock_irqrestore(&tty->read_lock, flags);
100 }
101
102 /**
103 * check_unthrottle - allow new receive data
104 * @tty; tty device
105 *
106 * Check whether to call the driver.unthrottle function.
107 * We test the TTY_THROTTLED bit first so that it always
108 * indicates the current state. The decision about whether
109 * it is worth allowing more input has been taken by the caller.
110 * Can sleep, may be called under the atomic_read semaphore but
111 * this is not guaranteed.
112 */
113
114 static void check_unthrottle(struct tty_struct * tty)
115 {
116 if (tty->count &&
117 test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
118 tty->driver->unthrottle)
119 tty->driver->unthrottle(tty);
120 }
121
122 /**
123 * reset_buffer_flags - reset buffer state
124 * @tty: terminal to reset
125 *
126 * Reset the read buffer counters, clear the flags,
127 * and make sure the driver is unthrottled. Called
128 * from n_tty_open() and n_tty_flush_buffer().
129 */
130 static void reset_buffer_flags(struct tty_struct *tty)
131 {
132 unsigned long flags;
133
134 spin_lock_irqsave(&tty->read_lock, flags);
135 tty->read_head = tty->read_tail = tty->read_cnt = 0;
136 spin_unlock_irqrestore(&tty->read_lock, flags);
137 tty->canon_head = tty->canon_data = tty->erasing = 0;
138 memset(&tty->read_flags, 0, sizeof tty->read_flags);
139 check_unthrottle(tty);
140 }
141
142 /**
143 * n_tty_flush_buffer - clean input queue
144 * @tty: terminal device
145 *
146 * Flush the input buffer. Called when the line discipline is
147 * being closed, when the tty layer wants the buffer flushed (eg
148 * at hangup) or when the N_TTY line discipline internally has to
149 * clean the pending queue (for example some signals).
150 *
151 * FIXME: tty->ctrl_status is not spinlocked and relies on
152 * lock_kernel() still.
153 */
154
155 static void n_tty_flush_buffer(struct tty_struct * tty)
156 {
157 /* clear everything and unthrottle the driver */
158 reset_buffer_flags(tty);
159
160 if (!tty->link)
161 return;
162
163 if (tty->link->packet) {
164 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
165 wake_up_interruptible(&tty->link->read_wait);
166 }
167 }
168
169 /**
170 * n_tty_chars_in_buffer - report available bytes
171 * @tty: tty device
172 *
173 * Report the number of characters buffered to be delivered to user
174 * at this instant in time.
175 */
176
177 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
178 {
179 unsigned long flags;
180 ssize_t n = 0;
181
182 spin_lock_irqsave(&tty->read_lock, flags);
183 if (!tty->icanon) {
184 n = tty->read_cnt;
185 } else if (tty->canon_data) {
186 n = (tty->canon_head > tty->read_tail) ?
187 tty->canon_head - tty->read_tail :
188 tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
189 }
190 spin_unlock_irqrestore(&tty->read_lock, flags);
191 return n;
192 }
193
194 /**
195 * is_utf8_continuation - utf8 multibyte check
196 * @c: byte to check
197 *
198 * Returns true if the utf8 character 'c' is a multibyte continuation
199 * character. We use this to correctly compute the on screen size
200 * of the character when printing
201 */
202
203 static inline int is_utf8_continuation(unsigned char c)
204 {
205 return (c & 0xc0) == 0x80;
206 }
207
208 /**
209 * is_continuation - multibyte check
210 * @c: byte to check
211 *
212 * Returns true if the utf8 character 'c' is a multibyte continuation
213 * character and the terminal is in unicode mode.
214 */
215
216 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
217 {
218 return I_IUTF8(tty) && is_utf8_continuation(c);
219 }
220
221 /**
222 * opost - output post processor
223 * @c: character (or partial unicode symbol)
224 * @tty: terminal device
225 *
226 * Perform OPOST processing. Returns -1 when the output device is
227 * full and the character must be retried. Note that Linux currently
228 * ignores TABDLY, CRDLY, VTDLY, FFDLY and NLDLY. They simply aren't
229 * relevant in the world today. If you ever need them, add them here.
230 *
231 * Called from both the receive and transmit sides and can be called
232 * re-entrantly. Relies on lock_kernel() still.
233 */
234
235 static int opost(unsigned char c, struct tty_struct *tty)
236 {
237 int space, spaces;
238
239 space = tty->driver->write_room(tty);
240 if (!space)
241 return -1;
242
243 if (O_OPOST(tty)) {
244 switch (c) {
245 case '\n':
246 if (O_ONLRET(tty))
247 tty->column = 0;
248 if (O_ONLCR(tty)) {
249 if (space < 2)
250 return -1;
251 tty->driver->put_char(tty, '\r');
252 tty->column = 0;
253 }
254 tty->canon_column = tty->column;
255 break;
256 case '\r':
257 if (O_ONOCR(tty) && tty->column == 0)
258 return 0;
259 if (O_OCRNL(tty)) {
260 c = '\n';
261 if (O_ONLRET(tty))
262 tty->canon_column = tty->column = 0;
263 break;
264 }
265 tty->canon_column = tty->column = 0;
266 break;
267 case '\t':
268 spaces = 8 - (tty->column & 7);
269 if (O_TABDLY(tty) == XTABS) {
270 if (space < spaces)
271 return -1;
272 tty->column += spaces;
273 tty->driver->write(tty, " ", spaces);
274 return 0;
275 }
276 tty->column += spaces;
277 break;
278 case '\b':
279 if (tty->column > 0)
280 tty->column--;
281 break;
282 default:
283 if (O_OLCUC(tty))
284 c = toupper(c);
285 if (!iscntrl(c) && !is_continuation(c, tty))
286 tty->column++;
287 break;
288 }
289 }
290 tty->driver->put_char(tty, c);
291 return 0;
292 }
293
294 /**
295 * opost_block - block postprocess
296 * @tty: terminal device
297 * @inbuf: user buffer
298 * @nr: number of bytes
299 *
300 * This path is used to speed up block console writes, among other
301 * things when processing blocks of output data. It handles only
302 * the simple cases normally found and helps to generate blocks of
303 * symbols for the console driver and thus improve performance.
304 *
305 * Called from write_chan under the tty layer write lock.
306 */
307
308 static ssize_t opost_block(struct tty_struct * tty,
309 const unsigned char * buf, unsigned int nr)
310 {
311 int space;
312 int i;
313 const unsigned char *cp;
314
315 space = tty->driver->write_room(tty);
316 if (!space)
317 return 0;
318 if (nr > space)
319 nr = space;
320
321 for (i = 0, cp = buf; i < nr; i++, cp++) {
322 switch (*cp) {
323 case '\n':
324 if (O_ONLRET(tty))
325 tty->column = 0;
326 if (O_ONLCR(tty))
327 goto break_out;
328 tty->canon_column = tty->column;
329 break;
330 case '\r':
331 if (O_ONOCR(tty) && tty->column == 0)
332 goto break_out;
333 if (O_OCRNL(tty))
334 goto break_out;
335 tty->canon_column = tty->column = 0;
336 break;
337 case '\t':
338 goto break_out;
339 case '\b':
340 if (tty->column > 0)
341 tty->column--;
342 break;
343 default:
344 if (O_OLCUC(tty))
345 goto break_out;
346 if (!iscntrl(*cp))
347 tty->column++;
348 break;
349 }
350 }
351 break_out:
352 if (tty->driver->flush_chars)
353 tty->driver->flush_chars(tty);
354 i = tty->driver->write(tty, buf, i);
355 return i;
356 }
357
358
359 /**
360 * put_char - write character to driver
361 * @c: character (or part of unicode symbol)
362 * @tty: terminal device
363 *
364 * Queue a byte to the driver layer for output
365 */
366
367 static inline void put_char(unsigned char c, struct tty_struct *tty)
368 {
369 tty->driver->put_char(tty, c);
370 }
371
372 /**
373 * echo_char - echo characters
374 * @c: unicode byte to echo
375 * @tty: terminal device
376 *
377 * Echo user input back onto the screen. This must be called only when
378 * L_ECHO(tty) is true. Called from the driver receive_buf path.
379 */
380
381 static void echo_char(unsigned char c, struct tty_struct *tty)
382 {
383 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t') {
384 put_char('^', tty);
385 put_char(c ^ 0100, tty);
386 tty->column += 2;
387 } else
388 opost(c, tty);
389 }
390
391 static inline void finish_erasing(struct tty_struct *tty)
392 {
393 if (tty->erasing) {
394 put_char('/', tty);
395 tty->column++;
396 tty->erasing = 0;
397 }
398 }
399
400 /**
401 * eraser - handle erase function
402 * @c: character input
403 * @tty: terminal device
404 *
405 * Perform erase and neccessary output when an erase character is
406 * present in the stream from the driver layer. Handles the complexities
407 * of UTF-8 multibyte symbols.
408 */
409
410 static void eraser(unsigned char c, struct tty_struct *tty)
411 {
412 enum { ERASE, WERASE, KILL } kill_type;
413 int head, seen_alnums, cnt;
414 unsigned long flags;
415
416 if (tty->read_head == tty->canon_head) {
417 /* opost('\a', tty); */ /* what do you think? */
418 return;
419 }
420 if (c == ERASE_CHAR(tty))
421 kill_type = ERASE;
422 else if (c == WERASE_CHAR(tty))
423 kill_type = WERASE;
424 else {
425 if (!L_ECHO(tty)) {
426 spin_lock_irqsave(&tty->read_lock, flags);
427 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
428 (N_TTY_BUF_SIZE - 1));
429 tty->read_head = tty->canon_head;
430 spin_unlock_irqrestore(&tty->read_lock, flags);
431 return;
432 }
433 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
434 spin_lock_irqsave(&tty->read_lock, flags);
435 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
436 (N_TTY_BUF_SIZE - 1));
437 tty->read_head = tty->canon_head;
438 spin_unlock_irqrestore(&tty->read_lock, flags);
439 finish_erasing(tty);
440 echo_char(KILL_CHAR(tty), tty);
441 /* Add a newline if ECHOK is on and ECHOKE is off. */
442 if (L_ECHOK(tty))
443 opost('\n', tty);
444 return;
445 }
446 kill_type = KILL;
447 }
448
449 seen_alnums = 0;
450 while (tty->read_head != tty->canon_head) {
451 head = tty->read_head;
452
453 /* erase a single possibly multibyte character */
454 do {
455 head = (head - 1) & (N_TTY_BUF_SIZE-1);
456 c = tty->read_buf[head];
457 } while (is_continuation(c, tty) && head != tty->canon_head);
458
459 /* do not partially erase */
460 if (is_continuation(c, tty))
461 break;
462
463 if (kill_type == WERASE) {
464 /* Equivalent to BSD's ALTWERASE. */
465 if (isalnum(c) || c == '_')
466 seen_alnums++;
467 else if (seen_alnums)
468 break;
469 }
470 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
471 spin_lock_irqsave(&tty->read_lock, flags);
472 tty->read_head = head;
473 tty->read_cnt -= cnt;
474 spin_unlock_irqrestore(&tty->read_lock, flags);
475 if (L_ECHO(tty)) {
476 if (L_ECHOPRT(tty)) {
477 if (!tty->erasing) {
478 put_char('\\', tty);
479 tty->column++;
480 tty->erasing = 1;
481 }
482 /* if cnt > 1, output a multi-byte character */
483 echo_char(c, tty);
484 while (--cnt > 0) {
485 head = (head+1) & (N_TTY_BUF_SIZE-1);
486 put_char(tty->read_buf[head], tty);
487 }
488 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
489 echo_char(ERASE_CHAR(tty), tty);
490 } else if (c == '\t') {
491 unsigned int col = tty->canon_column;
492 unsigned long tail = tty->canon_head;
493
494 /* Find the column of the last char. */
495 while (tail != tty->read_head) {
496 c = tty->read_buf[tail];
497 if (c == '\t')
498 col = (col | 7) + 1;
499 else if (iscntrl(c)) {
500 if (L_ECHOCTL(tty))
501 col += 2;
502 } else if (!is_continuation(c, tty))
503 col++;
504 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
505 }
506
507 /* should never happen */
508 if (tty->column > 0x80000000)
509 tty->column = 0;
510
511 /* Now backup to that column. */
512 while (tty->column > col) {
513 /* Can't use opost here. */
514 put_char('\b', tty);
515 if (tty->column > 0)
516 tty->column--;
517 }
518 } else {
519 if (iscntrl(c) && L_ECHOCTL(tty)) {
520 put_char('\b', tty);
521 put_char(' ', tty);
522 put_char('\b', tty);
523 if (tty->column > 0)
524 tty->column--;
525 }
526 if (!iscntrl(c) || L_ECHOCTL(tty)) {
527 put_char('\b', tty);
528 put_char(' ', tty);
529 put_char('\b', tty);
530 if (tty->column > 0)
531 tty->column--;
532 }
533 }
534 }
535 if (kill_type == ERASE)
536 break;
537 }
538 if (tty->read_head == tty->canon_head)
539 finish_erasing(tty);
540 }
541
542 /**
543 * isig - handle the ISIG optio
544 * @sig: signal
545 * @tty: terminal
546 * @flush: force flush
547 *
548 * Called when a signal is being sent due to terminal input. This
549 * may caus terminal flushing to take place according to the termios
550 * settings and character used. Called from the driver receive_buf
551 * path so serialized.
552 */
553
554 static inline void isig(int sig, struct tty_struct *tty, int flush)
555 {
556 if (tty->pgrp > 0)
557 kill_pg(tty->pgrp, sig, 1);
558 if (flush || !L_NOFLSH(tty)) {
559 n_tty_flush_buffer(tty);
560 if (tty->driver->flush_buffer)
561 tty->driver->flush_buffer(tty);
562 }
563 }
564
565 /**
566 * n_tty_receive_break - handle break
567 * @tty: terminal
568 *
569 * An RS232 break event has been hit in the incoming bitstream. This
570 * can cause a variety of events depending upon the termios settings.
571 *
572 * Called from the receive_buf path so single threaded.
573 */
574
575 static inline void n_tty_receive_break(struct tty_struct *tty)
576 {
577 if (I_IGNBRK(tty))
578 return;
579 if (I_BRKINT(tty)) {
580 isig(SIGINT, tty, 1);
581 return;
582 }
583 if (I_PARMRK(tty)) {
584 put_tty_queue('\377', tty);
585 put_tty_queue('\0', tty);
586 }
587 put_tty_queue('\0', tty);
588 wake_up_interruptible(&tty->read_wait);
589 }
590
591 /**
592 * n_tty_receive_overrun - handle overrun reporting
593 * @tty: terminal
594 *
595 * Data arrived faster than we could process it. While the tty
596 * driver has flagged this the bits that were missed are gone
597 * forever.
598 *
599 * Called from the receive_buf path so single threaded. Does not
600 * need locking as num_overrun and overrun_time are function
601 * private.
602 */
603
604 static inline void n_tty_receive_overrun(struct tty_struct *tty)
605 {
606 char buf[64];
607
608 tty->num_overrun++;
609 if (time_before(tty->overrun_time, jiffies - HZ)) {
610 printk(KERN_WARNING "%s: %d input overrun(s)\n", tty_name(tty, buf),
611 tty->num_overrun);
612 tty->overrun_time = jiffies;
613 tty->num_overrun = 0;
614 }
615 }
616
617 /**
618 * n_tty_receive_parity_error - error notifier
619 * @tty: terminal device
620 * @c: character
621 *
622 * Process a parity error and queue the right data to indicate
623 * the error case if neccessary. Locking as per n_tty_receive_buf.
624 */
625 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
626 unsigned char c)
627 {
628 if (I_IGNPAR(tty)) {
629 return;
630 }
631 if (I_PARMRK(tty)) {
632 put_tty_queue('\377', tty);
633 put_tty_queue('\0', tty);
634 put_tty_queue(c, tty);
635 } else if (I_INPCK(tty))
636 put_tty_queue('\0', tty);
637 else
638 put_tty_queue(c, tty);
639 wake_up_interruptible(&tty->read_wait);
640 }
641
642 /**
643 * n_tty_receive_char - perform processing
644 * @tty: terminal device
645 * @c: character
646 *
647 * Process an individual character of input received from the driver.
648 * This is serialized with respect to itself by the rules for the
649 * driver above.
650 */
651
652 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
653 {
654 unsigned long flags;
655
656 if (tty->raw) {
657 put_tty_queue(c, tty);
658 return;
659 }
660
661 if (tty->stopped && !tty->flow_stopped &&
662 I_IXON(tty) && I_IXANY(tty)) {
663 start_tty(tty);
664 return;
665 }
666
667 if (I_ISTRIP(tty))
668 c &= 0x7f;
669 if (I_IUCLC(tty) && L_IEXTEN(tty))
670 c=tolower(c);
671
672 if (tty->closing) {
673 if (I_IXON(tty)) {
674 if (c == START_CHAR(tty))
675 start_tty(tty);
676 else if (c == STOP_CHAR(tty))
677 stop_tty(tty);
678 }
679 return;
680 }
681
682 /*
683 * If the previous character was LNEXT, or we know that this
684 * character is not one of the characters that we'll have to
685 * handle specially, do shortcut processing to speed things
686 * up.
687 */
688 if (!test_bit(c, tty->process_char_map) || tty->lnext) {
689 finish_erasing(tty);
690 tty->lnext = 0;
691 if (L_ECHO(tty)) {
692 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
693 put_char('\a', tty); /* beep if no space */
694 return;
695 }
696 /* Record the column of first canon char. */
697 if (tty->canon_head == tty->read_head)
698 tty->canon_column = tty->column;
699 echo_char(c, tty);
700 }
701 if (I_PARMRK(tty) && c == (unsigned char) '\377')
702 put_tty_queue(c, tty);
703 put_tty_queue(c, tty);
704 return;
705 }
706
707 if (c == '\r') {
708 if (I_IGNCR(tty))
709 return;
710 if (I_ICRNL(tty))
711 c = '\n';
712 } else if (c == '\n' && I_INLCR(tty))
713 c = '\r';
714 if (I_IXON(tty)) {
715 if (c == START_CHAR(tty)) {
716 start_tty(tty);
717 return;
718 }
719 if (c == STOP_CHAR(tty)) {
720 stop_tty(tty);
721 return;
722 }
723 }
724 if (L_ISIG(tty)) {
725 int signal;
726 signal = SIGINT;
727 if (c == INTR_CHAR(tty))
728 goto send_signal;
729 signal = SIGQUIT;
730 if (c == QUIT_CHAR(tty))
731 goto send_signal;
732 signal = SIGTSTP;
733 if (c == SUSP_CHAR(tty)) {
734 send_signal:
735 isig(signal, tty, 0);
736 return;
737 }
738 }
739 if (tty->icanon) {
740 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
741 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
742 eraser(c, tty);
743 return;
744 }
745 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
746 tty->lnext = 1;
747 if (L_ECHO(tty)) {
748 finish_erasing(tty);
749 if (L_ECHOCTL(tty)) {
750 put_char('^', tty);
751 put_char('\b', tty);
752 }
753 }
754 return;
755 }
756 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
757 L_IEXTEN(tty)) {
758 unsigned long tail = tty->canon_head;
759
760 finish_erasing(tty);
761 echo_char(c, tty);
762 opost('\n', tty);
763 while (tail != tty->read_head) {
764 echo_char(tty->read_buf[tail], tty);
765 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
766 }
767 return;
768 }
769 if (c == '\n') {
770 if (L_ECHO(tty) || L_ECHONL(tty)) {
771 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
772 put_char('\a', tty);
773 return;
774 }
775 opost('\n', tty);
776 }
777 goto handle_newline;
778 }
779 if (c == EOF_CHAR(tty)) {
780 if (tty->canon_head != tty->read_head)
781 set_bit(TTY_PUSH, &tty->flags);
782 c = __DISABLED_CHAR;
783 goto handle_newline;
784 }
785 if ((c == EOL_CHAR(tty)) ||
786 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
787 /*
788 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
789 */
790 if (L_ECHO(tty)) {
791 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
792 put_char('\a', tty);
793 return;
794 }
795 /* Record the column of first canon char. */
796 if (tty->canon_head == tty->read_head)
797 tty->canon_column = tty->column;
798 echo_char(c, tty);
799 }
800 /*
801 * XXX does PARMRK doubling happen for
802 * EOL_CHAR and EOL2_CHAR?
803 */
804 if (I_PARMRK(tty) && c == (unsigned char) '\377')
805 put_tty_queue(c, tty);
806
807 handle_newline:
808 spin_lock_irqsave(&tty->read_lock, flags);
809 set_bit(tty->read_head, tty->read_flags);
810 put_tty_queue_nolock(c, tty);
811 tty->canon_head = tty->read_head;
812 tty->canon_data++;
813 spin_unlock_irqrestore(&tty->read_lock, flags);
814 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
815 if (waitqueue_active(&tty->read_wait))
816 wake_up_interruptible(&tty->read_wait);
817 return;
818 }
819 }
820
821 finish_erasing(tty);
822 if (L_ECHO(tty)) {
823 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
824 put_char('\a', tty); /* beep if no space */
825 return;
826 }
827 if (c == '\n')
828 opost('\n', tty);
829 else {
830 /* Record the column of first canon char. */
831 if (tty->canon_head == tty->read_head)
832 tty->canon_column = tty->column;
833 echo_char(c, tty);
834 }
835 }
836
837 if (I_PARMRK(tty) && c == (unsigned char) '\377')
838 put_tty_queue(c, tty);
839
840 put_tty_queue(c, tty);
841 }
842
843 /**
844 * n_tty_receive_room - receive space
845 * @tty: terminal
846 *
847 * Called by the driver to find out how much data it is
848 * permitted to feed to the line discipline without any being lost
849 * and thus to manage flow control. Not serialized. Answers for the
850 * "instant".
851 */
852
853 static int n_tty_receive_room(struct tty_struct *tty)
854 {
855 int left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
856
857 /*
858 * If we are doing input canonicalization, and there are no
859 * pending newlines, let characters through without limit, so
860 * that erase characters will be handled. Other excess
861 * characters will be beeped.
862 */
863 if (tty->icanon && !tty->canon_data)
864 return N_TTY_BUF_SIZE;
865
866 if (left > 0)
867 return left;
868 return 0;
869 }
870
871 /**
872 * n_tty_write_wakeup - asynchronous I/O notifier
873 * @tty: tty device
874 *
875 * Required for the ptys, serial driver etc. since processes
876 * that attach themselves to the master and rely on ASYNC
877 * IO must be woken up
878 */
879
880 static void n_tty_write_wakeup(struct tty_struct *tty)
881 {
882 if (tty->fasync)
883 {
884 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
885 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
886 }
887 return;
888 }
889
890 /**
891 * n_tty_receive_buf - data receive
892 * @tty: terminal device
893 * @cp: buffer
894 * @fp: flag buffer
895 * @count: characters
896 *
897 * Called by the terminal driver when a block of characters has
898 * been received. This function must be called from soft contexts
899 * not from interrupt context. The driver is responsible for making
900 * calls one at a time and in order (or using flush_to_ldisc)
901 */
902
903 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
904 char *fp, int count)
905 {
906 const unsigned char *p;
907 char *f, flags = TTY_NORMAL;
908 int i;
909 char buf[64];
910 unsigned long cpuflags;
911
912 if (!tty->read_buf)
913 return;
914
915 if (tty->real_raw) {
916 spin_lock_irqsave(&tty->read_lock, cpuflags);
917 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
918 N_TTY_BUF_SIZE - tty->read_head);
919 i = min(count, i);
920 memcpy(tty->read_buf + tty->read_head, cp, i);
921 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
922 tty->read_cnt += i;
923 cp += i;
924 count -= i;
925
926 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
927 N_TTY_BUF_SIZE - tty->read_head);
928 i = min(count, i);
929 memcpy(tty->read_buf + tty->read_head, cp, i);
930 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
931 tty->read_cnt += i;
932 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
933 } else {
934 for (i=count, p = cp, f = fp; i; i--, p++) {
935 if (f)
936 flags = *f++;
937 switch (flags) {
938 case TTY_NORMAL:
939 n_tty_receive_char(tty, *p);
940 break;
941 case TTY_BREAK:
942 n_tty_receive_break(tty);
943 break;
944 case TTY_PARITY:
945 case TTY_FRAME:
946 n_tty_receive_parity_error(tty, *p);
947 break;
948 case TTY_OVERRUN:
949 n_tty_receive_overrun(tty);
950 break;
951 default:
952 printk("%s: unknown flag %d\n",
953 tty_name(tty, buf), flags);
954 break;
955 }
956 }
957 if (tty->driver->flush_chars)
958 tty->driver->flush_chars(tty);
959 }
960
961 if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
962 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
963 if (waitqueue_active(&tty->read_wait))
964 wake_up_interruptible(&tty->read_wait);
965 }
966
967 /*
968 * Check the remaining room for the input canonicalization
969 * mode. We don't want to throttle the driver if we're in
970 * canonical mode and don't have a newline yet!
971 */
972 if (n_tty_receive_room(tty) < TTY_THRESHOLD_THROTTLE) {
973 /* check TTY_THROTTLED first so it indicates our state */
974 if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
975 tty->driver->throttle)
976 tty->driver->throttle(tty);
977 }
978 }
979
980 int is_ignored(int sig)
981 {
982 return (sigismember(¤t->blocked, sig) ||
983 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
984 }
985
986 /**
987 * n_tty_set_termios - termios data changed
988 * @tty: terminal
989 * @old: previous data
990 *
991 * Called by the tty layer when the user changes termios flags so
992 * that the line discipline can plan ahead. This function cannot sleep
993 * and is protected from re-entry by the tty layer. The user is
994 * guaranteed that this function will not be re-entered or in progress
995 * when the ldisc is closed.
996 */
997
998 static void n_tty_set_termios(struct tty_struct *tty, struct termios * old)
999 {
1000 if (!tty)
1001 return;
1002
1003 tty->icanon = (L_ICANON(tty) != 0);
1004 if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1005 tty->raw = 1;
1006 tty->real_raw = 1;
1007 return;
1008 }
1009 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1010 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1011 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1012 I_PARMRK(tty)) {
1013 memset(tty->process_char_map, 0, 256/8);
1014
1015 if (I_IGNCR(tty) || I_ICRNL(tty))
1016 set_bit('\r', tty->process_char_map);
1017 if (I_INLCR(tty))
1018 set_bit('\n', tty->process_char_map);
1019
1020 if (L_ICANON(tty)) {
1021 set_bit(ERASE_CHAR(tty), tty->process_char_map);
1022 set_bit(KILL_CHAR(tty), tty->process_char_map);
1023 set_bit(EOF_CHAR(tty), tty->process_char_map);
1024 set_bit('\n', tty->process_char_map);
1025 set_bit(EOL_CHAR(tty), tty->process_char_map);
1026 if (L_IEXTEN(tty)) {
1027 set_bit(WERASE_CHAR(tty),
1028 tty->process_char_map);
1029 set_bit(LNEXT_CHAR(tty),
1030 tty->process_char_map);
1031 set_bit(EOL2_CHAR(tty),
1032 tty->process_char_map);
1033 if (L_ECHO(tty))
1034 set_bit(REPRINT_CHAR(tty),
1035 tty->process_char_map);
1036 }
1037 }
1038 if (I_IXON(tty)) {
1039 set_bit(START_CHAR(tty), tty->process_char_map);
1040 set_bit(STOP_CHAR(tty), tty->process_char_map);
1041 }
1042 if (L_ISIG(tty)) {
1043 set_bit(INTR_CHAR(tty), tty->process_char_map);
1044 set_bit(QUIT_CHAR(tty), tty->process_char_map);
1045 set_bit(SUSP_CHAR(tty), tty->process_char_map);
1046 }
1047 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1048 tty->raw = 0;
1049 tty->real_raw = 0;
1050 } else {
1051 tty->raw = 1;
1052 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1053 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1054 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1055 tty->real_raw = 1;
1056 else
1057 tty->real_raw = 0;
1058 }
1059 }
1060
1061 /**
1062 * n_tty_close - close the ldisc for this tty
1063 * @tty: device
1064 *
1065 * Called from the terminal layer when this line discipline is
1066 * being shut down, either because of a close or becsuse of a
1067 * discipline change. The function will not be called while other
1068 * ldisc methods are in progress.
1069 */
1070
1071 static void n_tty_close(struct tty_struct *tty)
1072 {
1073 n_tty_flush_buffer(tty);
1074 if (tty->read_buf) {
1075 free_buf(tty->read_buf);
1076 tty->read_buf = NULL;
1077 }
1078 }
1079
1080 /**
1081 * n_tty_open - open an ldisc
1082 * @tty: terminal to open
1083 *
1084 * Called when this line discipline is being attached to the
1085 * terminal device. Can sleep. Called serialized so that no
1086 * other events will occur in parallel. No further open will occur
1087 * until a close.
1088 */
1089
1090 static int n_tty_open(struct tty_struct *tty)
1091 {
1092 if (!tty)
1093 return -EINVAL;
1094
1095 /* This one is ugly. Currently a malloc failure here can panic */
1096 if (!tty->read_buf) {
1097 tty->read_buf = alloc_buf();
1098 if (!tty->read_buf)
1099 return -ENOMEM;
1100 }
1101 memset(tty->read_buf, 0, N_TTY_BUF_SIZE);
1102 reset_buffer_flags(tty);
1103 tty->column = 0;
1104 n_tty_set_termios(tty, NULL);
1105 tty->minimum_to_wake = 1;
1106 tty->closing = 0;
1107 return 0;
1108 }
1109
1110 static inline int input_available_p(struct tty_struct *tty, int amt)
1111 {
1112 if (tty->icanon) {
1113 if (tty->canon_data)
1114 return 1;
1115 } else if (tty->read_cnt >= (amt ? amt : 1))
1116 return 1;
1117
1118 return 0;
1119 }
1120
1121 /**
1122 * copy_from_read_buf - copy read data directly
1123 * @tty: terminal device
1124 * @b: user data
1125 * @nr: size of data
1126 *
1127 * Helper function to speed up read_chan. It is only called when
1128 * ICANON is off; it copies characters straight from the tty queue to
1129 * user space directly. It can be profitably called twice; once to
1130 * drain the space from the tail pointer to the (physical) end of the
1131 * buffer, and once to drain the space from the (physical) beginning of
1132 * the buffer to head pointer.
1133 *
1134 * Called under the tty->atomic_read sem and with TTY_DONT_FLIP set
1135 *
1136 */
1137
1138 static inline int copy_from_read_buf(struct tty_struct *tty,
1139 unsigned char __user **b,
1140 size_t *nr)
1141
1142 {
1143 int retval;
1144 size_t n;
1145 unsigned long flags;
1146
1147 retval = 0;
1148 spin_lock_irqsave(&tty->read_lock, flags);
1149 n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1150 n = min(*nr, n);
1151 spin_unlock_irqrestore(&tty->read_lock, flags);
1152 if (n) {
1153 mb();
1154 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1155 n -= retval;
1156 spin_lock_irqsave(&tty->read_lock, flags);
1157 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1158 tty->read_cnt -= n;
1159 spin_unlock_irqrestore(&tty->read_lock, flags);
1160 *b += n;
1161 *nr -= n;
1162 }
1163 return retval;
1164 }
1165
1166 extern ssize_t redirected_tty_write(struct file *,const char *,size_t,loff_t *);
1167
1168 /**
1169 * job_control - check job control
1170 * @tty: tty
1171 * @file: file handle
1172 *
1173 * Perform job control management checks on this file/tty descriptor
1174 * and if appropriate send any needed signals and return a negative
1175 * error code if action should be taken.
1176 */
1177
1178 static int job_control(struct tty_struct *tty, struct file *file)
1179 {
1180 /* Job control check -- must be done at start and after
1181 every sleep (POSIX.1 7.1.1.4). */
1182 /* NOTE: not yet done after every sleep pending a thorough
1183 check of the logic of this change. -- jlc */
1184 /* don't stop on /dev/console */
1185 if (file->f_op->write != redirected_tty_write &&
1186 current->signal->tty == tty) {
1187 if (tty->pgrp <= 0)
1188 printk("read_chan: tty->pgrp <= 0!\n");
1189 else if (process_group(current) != tty->pgrp) {
1190 if (is_ignored(SIGTTIN) ||
1191 is_orphaned_pgrp(process_group(current)))
1192 return -EIO;
1193 kill_pg(process_group(current), SIGTTIN, 1);
1194 return -ERESTARTSYS;
1195 }
1196 }
1197 return 0;
1198 }
1199
1200
1201 /**
1202 * read_chan - read function for tty
1203 * @tty: tty device
1204 * @file: file object
1205 * @buf: userspace buffer pointer
1206 * @nr: size of I/O
1207 *
1208 * Perform reads for the line discipline. We are guaranteed that the
1209 * line discipline will not be closed under us but we may get multiple
1210 * parallel readers and must handle this ourselves. We may also get
1211 * a hangup. Always called in user context, may sleep.
1212 *
1213 * This code must be sure never to sleep through a hangup.
1214 */
1215
1216 static ssize_t read_chan(struct tty_struct *tty, struct file *file,
1217 unsigned char __user *buf, size_t nr)
1218 {
1219 unsigned char __user *b = buf;
1220 DECLARE_WAITQUEUE(wait, current);
1221 int c;
1222 int minimum, time;
1223 ssize_t retval = 0;
1224 ssize_t size;
1225 long timeout;
1226 unsigned long flags;
1227
1228 do_it_again:
1229
1230 if (!tty->read_buf) {
1231 printk("n_tty_read_chan: called with read_buf == NULL?!?\n");
1232 return -EIO;
1233 }
1234
1235 c = job_control(tty, file);
1236 if(c < 0)
1237 return c;
1238
1239 minimum = time = 0;
1240 timeout = MAX_SCHEDULE_TIMEOUT;
1241 if (!tty->icanon) {
1242 time = (HZ / 10) * TIME_CHAR(tty);
1243 minimum = MIN_CHAR(tty);
1244 if (minimum) {
1245 if (time)
1246 tty->minimum_to_wake = 1;
1247 else if (!waitqueue_active(&tty->read_wait) ||
1248 (tty->minimum_to_wake > minimum))
1249 tty->minimum_to_wake = minimum;
1250 } else {
1251 timeout = 0;
1252 if (time) {
1253 timeout = time;
1254 time = 0;
1255 }
1256 tty->minimum_to_wake = minimum = 1;
1257 }
1258 }
1259
1260 /*
1261 * Internal serialization of reads.
1262 */
1263 if (file->f_flags & O_NONBLOCK) {
1264 if (down_trylock(&tty->atomic_read))
1265 return -EAGAIN;
1266 }
1267 else {
1268 if (down_interruptible(&tty->atomic_read))
1269 return -ERESTARTSYS;
1270 }
1271
1272 add_wait_queue(&tty->read_wait, &wait);
1273 set_bit(TTY_DONT_FLIP, &tty->flags);
1274 while (nr) {
1275 /* First test for status change. */
1276 if (tty->packet && tty->link->ctrl_status) {
1277 unsigned char cs;
1278 if (b != buf)
1279 break;
1280 cs = tty->link->ctrl_status;
1281 tty->link->ctrl_status = 0;
1282 if (put_user(cs, b++)) {
1283 retval = -EFAULT;
1284 b--;
1285 break;
1286 }
1287 nr--;
1288 break;
1289 }
1290 /* This statement must be first before checking for input
1291 so that any interrupt will set the state back to
1292 TASK_RUNNING. */
1293 set_current_state(TASK_INTERRUPTIBLE);
1294
1295 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1296 ((minimum - (b - buf)) >= 1))
1297 tty->minimum_to_wake = (minimum - (b - buf));
1298
1299 if (!input_available_p(tty, 0)) {
1300 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1301 retval = -EIO;
1302 break;
1303 }
1304 if (tty_hung_up_p(file))
1305 break;
1306 if (!timeout)
1307 break;
1308 if (file->f_flags & O_NONBLOCK) {
1309 retval = -EAGAIN;
1310 break;
1311 }
1312 if (signal_pending(current)) {
1313 retval = -ERESTARTSYS;
1314 break;
1315 }
1316 clear_bit(TTY_DONT_FLIP, &tty->flags);
1317 timeout = schedule_timeout(timeout);
1318 set_bit(TTY_DONT_FLIP, &tty->flags);
1319 continue;
1320 }
1321 __set_current_state(TASK_RUNNING);
1322
1323 /* Deal with packet mode. */
1324 if (tty->packet && b == buf) {
1325 if (put_user(TIOCPKT_DATA, b++)) {
1326 retval = -EFAULT;
1327 b--;
1328 break;
1329 }
1330 nr--;
1331 }
1332
1333 if (tty->icanon) {
1334 /* N.B. avoid overrun if nr == 0 */
1335 while (nr && tty->read_cnt) {
1336 int eol;
1337
1338 eol = test_and_clear_bit(tty->read_tail,
1339 tty->read_flags);
1340 c = tty->read_buf[tty->read_tail];
1341 spin_lock_irqsave(&tty->read_lock, flags);
1342 tty->read_tail = ((tty->read_tail+1) &
1343 (N_TTY_BUF_SIZE-1));
1344 tty->read_cnt--;
1345 if (eol) {
1346 /* this test should be redundant:
1347 * we shouldn't be reading data if
1348 * canon_data is 0
1349 */
1350 if (--tty->canon_data < 0)
1351 tty->canon_data = 0;
1352 }
1353 spin_unlock_irqrestore(&tty->read_lock, flags);
1354
1355 if (!eol || (c != __DISABLED_CHAR)) {
1356 if (put_user(c, b++)) {
1357 retval = -EFAULT;
1358 b--;
1359 break;
1360 }
1361 nr--;
1362 }
1363 if (eol)
1364 break;
1365 }
1366 if (retval)
1367 break;
1368 } else {
1369 int uncopied;
1370 uncopied = copy_from_read_buf(tty, &b, &nr);
1371 uncopied += copy_from_read_buf(tty, &b, &nr);
1372 if (uncopied) {
1373 retval = -EFAULT;
1374 break;
1375 }
1376 }
1377
1378 /* If there is enough space in the read buffer now, let the
1379 * low-level driver know. We use n_tty_chars_in_buffer() to
1380 * check the buffer, as it now knows about canonical mode.
1381 * Otherwise, if the driver is throttled and the line is
1382 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1383 * we won't get any more characters.
1384 */
1385 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE)
1386 check_unthrottle(tty);
1387
1388 if (b - buf >= minimum)
1389 break;
1390 if (time)
1391 timeout = time;
1392 }
1393 clear_bit(TTY_DONT_FLIP, &tty->flags);
1394 up(&tty->atomic_read);
1395 remove_wait_queue(&tty->read_wait, &wait);
1396
1397 if (!waitqueue_active(&tty->read_wait))
1398 tty->minimum_to_wake = minimum;
1399
1400 __set_current_state(TASK_RUNNING);
1401 size = b - buf;
1402 if (size) {
1403 retval = size;
1404 if (nr)
1405 clear_bit(TTY_PUSH, &tty->flags);
1406 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1407 goto do_it_again;
1408
1409 return retval;
1410 }
1411
1412 /**
1413 * write_chan - write function for tty
1414 * @tty: tty device
1415 * @file: file object
1416 * @buf: userspace buffer pointer
1417 * @nr: size of I/O
1418 *
1419 * Write function of the terminal device. This is serialized with
1420 * respect to other write callers but not to termios changes, reads
1421 * and other such events. We must be careful with N_TTY as the receive
1422 * code will echo characters, thus calling driver write methods.
1423 *
1424 * This code must be sure never to sleep through a hangup.
1425 */
1426
1427 static ssize_t write_chan(struct tty_struct * tty, struct file * file,
1428 const unsigned char * buf, size_t nr)
1429 {
1430 const unsigned char *b = buf;
1431 DECLARE_WAITQUEUE(wait, current);
1432 int c;
1433 ssize_t retval = 0;
1434
1435 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1436 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1437 retval = tty_check_change(tty);
1438 if (retval)
1439 return retval;
1440 }
1441
1442 add_wait_queue(&tty->write_wait, &wait);
1443 while (1) {
1444 set_current_state(TASK_INTERRUPTIBLE);
1445 if (signal_pending(current)) {
1446 retval = -ERESTARTSYS;
1447 break;
1448 }
1449 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1450 retval = -EIO;
1451 break;
1452 }
1453 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1454 while (nr > 0) {
1455 ssize_t num = opost_block(tty, b, nr);
1456 if (num < 0) {
1457 if (num == -EAGAIN)
1458 break;
1459 retval = num;
1460 goto break_out;
1461 }
1462 b += num;
1463 nr -= num;
1464 if (nr == 0)
1465 break;
1466 c = *b;
1467 if (opost(c, tty) < 0)
1468 break;
1469 b++; nr--;
1470 }
1471 if (tty->driver->flush_chars)
1472 tty->driver->flush_chars(tty);
1473 } else {
1474 c = tty->driver->write(tty, b, nr);
1475 if (c < 0) {
1476 retval = c;
1477 goto break_out;
1478 }
1479 b += c;
1480 nr -= c;
1481 }
1482 if (!nr)
1483 break;
1484 if (file->f_flags & O_NONBLOCK) {
1485 retval = -EAGAIN;
1486 break;
1487 }
1488 schedule();
1489 }
1490 break_out:
1491 __set_current_state(TASK_RUNNING);
1492 remove_wait_queue(&tty->write_wait, &wait);
1493 return (b - buf) ? b - buf : retval;
1494 }
1495
1496 /**
1497 * normal_poll - poll method for N_TTY
1498 * @tty: terminal device
1499 * @file: file accessing it
1500 * @wait: poll table
1501 *
1502 * Called when the line discipline is asked to poll() for data or
1503 * for special events. This code is not serialized with respect to
1504 * other events save open/close.
1505 *
1506 * This code must be sure never to sleep through a hangup.
1507 * Called without the kernel lock held - fine
1508 *
1509 * FIXME: if someone changes the VMIN or discipline settings for the
1510 * terminal while another process is in poll() the poll does not
1511 * recompute the new limits. Possibly set_termios should issue
1512 * a read wakeup to fix this bug.
1513 */
1514
1515 static unsigned int normal_poll(struct tty_struct * tty, struct file * file, poll_table *wait)
1516 {
1517 unsigned int mask = 0;
1518
1519 poll_wait(file, &tty->read_wait, wait);
1520 poll_wait(file, &tty->write_wait, wait);
1521 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
1522 mask |= POLLIN | POLLRDNORM;
1523 if (tty->packet && tty->link->ctrl_status)
1524 mask |= POLLPRI | POLLIN | POLLRDNORM;
1525 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
1526 mask |= POLLHUP;
1527 if (tty_hung_up_p(file))
1528 mask |= POLLHUP;
1529 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
1530 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
1531 tty->minimum_to_wake = MIN_CHAR(tty);
1532 else
1533 tty->minimum_to_wake = 1;
1534 }
1535 if (tty->driver->chars_in_buffer(tty) < WAKEUP_CHARS &&
1536 tty->driver->write_room(tty) > 0)
1537 mask |= POLLOUT | POLLWRNORM;
1538 return mask;
1539 }
1540
1541 struct tty_ldisc tty_ldisc_N_TTY = {
1542 TTY_LDISC_MAGIC, /* magic */
1543 "n_tty", /* name */
1544 0, /* num */
1545 0, /* flags */
1546 n_tty_open, /* open */
1547 n_tty_close, /* close */
1548 n_tty_flush_buffer, /* flush_buffer */
1549 n_tty_chars_in_buffer, /* chars_in_buffer */
1550 read_chan, /* read */
1551 write_chan, /* write */
1552 n_tty_ioctl, /* ioctl */
1553 n_tty_set_termios, /* set_termios */
1554 normal_poll, /* poll */
1555 NULL, /* hangup */
1556 n_tty_receive_buf, /* receive_buf */
1557 n_tty_receive_room, /* receive_room */
1558 n_tty_write_wakeup /* write_wakeup */
1559 };
1560
1561
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