Revert "ARM: tegra: tegratab: dummy change"
[linux-2.6.git] / drivers / tty / n_tty.c
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 n_tty_write 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 #include <linux/audit.h>
49 #include <linux/file.h>
50 #include <linux/uaccess.h>
51 #include <linux/module.h>
52
53
54 /* number of characters left in xmit buffer before select has we have room */
55 #define WAKEUP_CHARS 256
56
57 /*
58  * This defines the low- and high-watermarks for throttling and
59  * unthrottling the TTY driver.  These watermarks are used for
60  * controlling the space in the read buffer.
61  */
62 #define TTY_THRESHOLD_THROTTLE          128 /* now based on remaining room */
63 #define TTY_THRESHOLD_UNTHROTTLE        128
64
65 /*
66  * Special byte codes used in the echo buffer to represent operations
67  * or special handling of characters.  Bytes in the echo buffer that
68  * are not part of such special blocks are treated as normal character
69  * codes.
70  */
71 #define ECHO_OP_START 0xff
72 #define ECHO_OP_MOVE_BACK_COL 0x80
73 #define ECHO_OP_SET_CANON_COL 0x81
74 #define ECHO_OP_ERASE_TAB 0x82
75
76 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
77                                unsigned char __user *ptr)
78 {
79         tty_audit_add_data(tty, &x, 1);
80         return put_user(x, ptr);
81 }
82
83 /**
84  *      n_tty_set__room -       receive space
85  *      @tty: terminal
86  *
87  *      Called by the driver to find out how much data it is
88  *      permitted to feed to the line discipline without any being lost
89  *      and thus to manage flow control. Not serialized. Answers for the
90  *      "instant".
91  */
92
93 static void n_tty_set_room(struct tty_struct *tty)
94 {
95         /* tty->read_cnt is not read locked ? */
96         int     left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
97         int old_left;
98
99         /*
100          * If we are doing input canonicalization, and there are no
101          * pending newlines, let characters through without limit, so
102          * that erase characters will be handled.  Other excess
103          * characters will be beeped.
104          */
105         if (left <= 0)
106                 left = tty->icanon && !tty->canon_data;
107         old_left = tty->receive_room;
108         tty->receive_room = left;
109
110         /* Did this open up the receive buffer? We may need to flip */
111         if (left && !old_left)
112                 schedule_work(&tty->buf.work);
113 }
114
115 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
116 {
117         if (tty->read_cnt < N_TTY_BUF_SIZE) {
118                 tty->read_buf[tty->read_head] = c;
119                 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
120                 tty->read_cnt++;
121         }
122 }
123
124 /**
125  *      put_tty_queue           -       add character to tty
126  *      @c: character
127  *      @tty: tty device
128  *
129  *      Add a character to the tty read_buf queue. This is done under the
130  *      read_lock to serialize character addition and also to protect us
131  *      against parallel reads or flushes
132  */
133
134 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
135 {
136         unsigned long flags;
137         /*
138          *      The problem of stomping on the buffers ends here.
139          *      Why didn't anyone see this one coming? --AJK
140         */
141         spin_lock_irqsave(&tty->read_lock, flags);
142         put_tty_queue_nolock(c, tty);
143         spin_unlock_irqrestore(&tty->read_lock, flags);
144 }
145
146 /**
147  *      check_unthrottle        -       allow new receive data
148  *      @tty; tty device
149  *
150  *      Check whether to call the driver unthrottle functions
151  *
152  *      Can sleep, may be called under the atomic_read_lock mutex but
153  *      this is not guaranteed.
154  */
155 static void check_unthrottle(struct tty_struct *tty)
156 {
157         if (tty->count)
158                 tty_unthrottle(tty);
159 }
160
161 /**
162  *      reset_buffer_flags      -       reset buffer state
163  *      @tty: terminal to reset
164  *
165  *      Reset the read buffer counters, clear the flags,
166  *      and make sure the driver is unthrottled. Called
167  *      from n_tty_open() and n_tty_flush_buffer().
168  *
169  *      Locking: tty_read_lock for read fields.
170  */
171
172 static void reset_buffer_flags(struct tty_struct *tty)
173 {
174         unsigned long flags;
175
176         spin_lock_irqsave(&tty->read_lock, flags);
177         tty->read_head = tty->read_tail = tty->read_cnt = 0;
178         spin_unlock_irqrestore(&tty->read_lock, flags);
179
180         mutex_lock(&tty->echo_lock);
181         tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
182         mutex_unlock(&tty->echo_lock);
183
184         tty->canon_head = tty->canon_data = tty->erasing = 0;
185         memset(&tty->read_flags, 0, sizeof tty->read_flags);
186         n_tty_set_room(tty);
187 }
188
189 /**
190  *      n_tty_flush_buffer      -       clean input queue
191  *      @tty:   terminal device
192  *
193  *      Flush the input buffer. Called when the line discipline is
194  *      being closed, when the tty layer wants the buffer flushed (eg
195  *      at hangup) or when the N_TTY line discipline internally has to
196  *      clean the pending queue (for example some signals).
197  *
198  *      Locking: ctrl_lock, read_lock.
199  */
200
201 static void n_tty_flush_buffer(struct tty_struct *tty)
202 {
203         unsigned long flags;
204         /* clear everything and unthrottle the driver */
205         reset_buffer_flags(tty);
206
207         if (!tty->link)
208                 return;
209
210         spin_lock_irqsave(&tty->ctrl_lock, flags);
211         if (tty->link->packet) {
212                 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
213                 wake_up_interruptible(&tty->link->read_wait);
214         }
215         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
216 }
217
218 /**
219  *      n_tty_chars_in_buffer   -       report available bytes
220  *      @tty: tty device
221  *
222  *      Report the number of characters buffered to be delivered to user
223  *      at this instant in time.
224  *
225  *      Locking: read_lock
226  */
227
228 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
229 {
230         unsigned long flags;
231         ssize_t n = 0;
232
233         spin_lock_irqsave(&tty->read_lock, flags);
234         if (!tty->icanon) {
235                 n = tty->read_cnt;
236         } else if (tty->canon_data) {
237                 n = (tty->canon_head > tty->read_tail) ?
238                         tty->canon_head - tty->read_tail :
239                         tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
240         }
241         spin_unlock_irqrestore(&tty->read_lock, flags);
242         return n;
243 }
244
245 /**
246  *      is_utf8_continuation    -       utf8 multibyte check
247  *      @c: byte to check
248  *
249  *      Returns true if the utf8 character 'c' is a multibyte continuation
250  *      character. We use this to correctly compute the on screen size
251  *      of the character when printing
252  */
253
254 static inline int is_utf8_continuation(unsigned char c)
255 {
256         return (c & 0xc0) == 0x80;
257 }
258
259 /**
260  *      is_continuation         -       multibyte check
261  *      @c: byte to check
262  *
263  *      Returns true if the utf8 character 'c' is a multibyte continuation
264  *      character and the terminal is in unicode mode.
265  */
266
267 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
268 {
269         return I_IUTF8(tty) && is_utf8_continuation(c);
270 }
271
272 /**
273  *      do_output_char                  -       output one character
274  *      @c: character (or partial unicode symbol)
275  *      @tty: terminal device
276  *      @space: space available in tty driver write buffer
277  *
278  *      This is a helper function that handles one output character
279  *      (including special characters like TAB, CR, LF, etc.),
280  *      doing OPOST processing and putting the results in the
281  *      tty driver's write buffer.
282  *
283  *      Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
284  *      and NLDLY.  They simply aren't relevant in the world today.
285  *      If you ever need them, add them here.
286  *
287  *      Returns the number of bytes of buffer space used or -1 if
288  *      no space left.
289  *
290  *      Locking: should be called under the output_lock to protect
291  *               the column state and space left in the buffer
292  */
293
294 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
295 {
296         int     spaces;
297
298         if (!space)
299                 return -1;
300
301         switch (c) {
302         case '\n':
303                 if (O_ONLRET(tty))
304                         tty->column = 0;
305                 if (O_ONLCR(tty)) {
306                         if (space < 2)
307                                 return -1;
308                         tty->canon_column = tty->column = 0;
309                         tty->ops->write(tty, "\r\n", 2);
310                         return 2;
311                 }
312                 tty->canon_column = tty->column;
313                 break;
314         case '\r':
315                 if (O_ONOCR(tty) && tty->column == 0)
316                         return 0;
317                 if (O_OCRNL(tty)) {
318                         c = '\n';
319                         if (O_ONLRET(tty))
320                                 tty->canon_column = tty->column = 0;
321                         break;
322                 }
323                 tty->canon_column = tty->column = 0;
324                 break;
325         case '\t':
326                 spaces = 8 - (tty->column & 7);
327                 if (O_TABDLY(tty) == XTABS) {
328                         if (space < spaces)
329                                 return -1;
330                         tty->column += spaces;
331                         tty->ops->write(tty, "        ", spaces);
332                         return spaces;
333                 }
334                 tty->column += spaces;
335                 break;
336         case '\b':
337                 if (tty->column > 0)
338                         tty->column--;
339                 break;
340         default:
341                 if (!iscntrl(c)) {
342                         if (O_OLCUC(tty))
343                                 c = toupper(c);
344                         if (!is_continuation(c, tty))
345                                 tty->column++;
346                 }
347                 break;
348         }
349
350         tty_put_char(tty, c);
351         return 1;
352 }
353
354 /**
355  *      process_output                  -       output post processor
356  *      @c: character (or partial unicode symbol)
357  *      @tty: terminal device
358  *
359  *      Output one character with OPOST processing.
360  *      Returns -1 when the output device is full and the character
361  *      must be retried.
362  *
363  *      Locking: output_lock to protect column state and space left
364  *               (also, this is called from n_tty_write under the
365  *                tty layer write lock)
366  */
367
368 static int process_output(unsigned char c, struct tty_struct *tty)
369 {
370         int     space, retval;
371
372         mutex_lock(&tty->output_lock);
373
374         space = tty_write_room(tty);
375         retval = do_output_char(c, tty, space);
376
377         mutex_unlock(&tty->output_lock);
378         if (retval < 0)
379                 return -1;
380         else
381                 return 0;
382 }
383
384 /**
385  *      process_output_block            -       block post processor
386  *      @tty: terminal device
387  *      @buf: character buffer
388  *      @nr: number of bytes to output
389  *
390  *      Output a block of characters with OPOST processing.
391  *      Returns the number of characters output.
392  *
393  *      This path is used to speed up block console writes, among other
394  *      things when processing blocks of output data. It handles only
395  *      the simple cases normally found and helps to generate blocks of
396  *      symbols for the console driver and thus improve performance.
397  *
398  *      Locking: output_lock to protect column state and space left
399  *               (also, this is called from n_tty_write under the
400  *                tty layer write lock)
401  */
402
403 static ssize_t process_output_block(struct tty_struct *tty,
404                                     const unsigned char *buf, unsigned int nr)
405 {
406         int     space;
407         int     i;
408         const unsigned char *cp;
409
410         mutex_lock(&tty->output_lock);
411
412         space = tty_write_room(tty);
413         if (!space) {
414                 mutex_unlock(&tty->output_lock);
415                 return 0;
416         }
417         if (nr > space)
418                 nr = space;
419
420         for (i = 0, cp = buf; i < nr; i++, cp++) {
421                 unsigned char c = *cp;
422
423                 switch (c) {
424                 case '\n':
425                         if (O_ONLRET(tty))
426                                 tty->column = 0;
427                         if (O_ONLCR(tty))
428                                 goto break_out;
429                         tty->canon_column = tty->column;
430                         break;
431                 case '\r':
432                         if (O_ONOCR(tty) && tty->column == 0)
433                                 goto break_out;
434                         if (O_OCRNL(tty))
435                                 goto break_out;
436                         tty->canon_column = tty->column = 0;
437                         break;
438                 case '\t':
439                         goto break_out;
440                 case '\b':
441                         if (tty->column > 0)
442                                 tty->column--;
443                         break;
444                 default:
445                         if (!iscntrl(c)) {
446                                 if (O_OLCUC(tty))
447                                         goto break_out;
448                                 if (!is_continuation(c, tty))
449                                         tty->column++;
450                         }
451                         break;
452                 }
453         }
454 break_out:
455         i = tty->ops->write(tty, buf, i);
456
457         mutex_unlock(&tty->output_lock);
458         return i;
459 }
460
461 /**
462  *      process_echoes  -       write pending echo characters
463  *      @tty: terminal device
464  *
465  *      Write previously buffered echo (and other ldisc-generated)
466  *      characters to the tty.
467  *
468  *      Characters generated by the ldisc (including echoes) need to
469  *      be buffered because the driver's write buffer can fill during
470  *      heavy program output.  Echoing straight to the driver will
471  *      often fail under these conditions, causing lost characters and
472  *      resulting mismatches of ldisc state information.
473  *
474  *      Since the ldisc state must represent the characters actually sent
475  *      to the driver at the time of the write, operations like certain
476  *      changes in column state are also saved in the buffer and executed
477  *      here.
478  *
479  *      A circular fifo buffer is used so that the most recent characters
480  *      are prioritized.  Also, when control characters are echoed with a
481  *      prefixed "^", the pair is treated atomically and thus not separated.
482  *
483  *      Locking: output_lock to protect column state and space left,
484  *               echo_lock to protect the echo buffer
485  */
486
487 static void process_echoes(struct tty_struct *tty)
488 {
489         int     space, nr;
490         unsigned char c;
491         unsigned char *cp, *buf_end;
492
493         if (!tty->echo_cnt)
494                 return;
495
496         mutex_lock(&tty->output_lock);
497         mutex_lock(&tty->echo_lock);
498
499         space = tty_write_room(tty);
500
501         buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
502         cp = tty->echo_buf + tty->echo_pos;
503         nr = tty->echo_cnt;
504         while (nr > 0) {
505                 c = *cp;
506                 if (c == ECHO_OP_START) {
507                         unsigned char op;
508                         unsigned char *opp;
509                         int no_space_left = 0;
510
511                         /*
512                          * If the buffer byte is the start of a multi-byte
513                          * operation, get the next byte, which is either the
514                          * op code or a control character value.
515                          */
516                         opp = cp + 1;
517                         if (opp == buf_end)
518                                 opp -= N_TTY_BUF_SIZE;
519                         op = *opp;
520
521                         switch (op) {
522                                 unsigned int num_chars, num_bs;
523
524                         case ECHO_OP_ERASE_TAB:
525                                 if (++opp == buf_end)
526                                         opp -= N_TTY_BUF_SIZE;
527                                 num_chars = *opp;
528
529                                 /*
530                                  * Determine how many columns to go back
531                                  * in order to erase the tab.
532                                  * This depends on the number of columns
533                                  * used by other characters within the tab
534                                  * area.  If this (modulo 8) count is from
535                                  * the start of input rather than from a
536                                  * previous tab, we offset by canon column.
537                                  * Otherwise, tab spacing is normal.
538                                  */
539                                 if (!(num_chars & 0x80))
540                                         num_chars += tty->canon_column;
541                                 num_bs = 8 - (num_chars & 7);
542
543                                 if (num_bs > space) {
544                                         no_space_left = 1;
545                                         break;
546                                 }
547                                 space -= num_bs;
548                                 while (num_bs--) {
549                                         tty_put_char(tty, '\b');
550                                         if (tty->column > 0)
551                                                 tty->column--;
552                                 }
553                                 cp += 3;
554                                 nr -= 3;
555                                 break;
556
557                         case ECHO_OP_SET_CANON_COL:
558                                 tty->canon_column = tty->column;
559                                 cp += 2;
560                                 nr -= 2;
561                                 break;
562
563                         case ECHO_OP_MOVE_BACK_COL:
564                                 if (tty->column > 0)
565                                         tty->column--;
566                                 cp += 2;
567                                 nr -= 2;
568                                 break;
569
570                         case ECHO_OP_START:
571                                 /* This is an escaped echo op start code */
572                                 if (!space) {
573                                         no_space_left = 1;
574                                         break;
575                                 }
576                                 tty_put_char(tty, ECHO_OP_START);
577                                 tty->column++;
578                                 space--;
579                                 cp += 2;
580                                 nr -= 2;
581                                 break;
582
583                         default:
584                                 /*
585                                  * If the op is not a special byte code,
586                                  * it is a ctrl char tagged to be echoed
587                                  * as "^X" (where X is the letter
588                                  * representing the control char).
589                                  * Note that we must ensure there is
590                                  * enough space for the whole ctrl pair.
591                                  *
592                                  */
593                                 if (space < 2) {
594                                         no_space_left = 1;
595                                         break;
596                                 }
597                                 tty_put_char(tty, '^');
598                                 tty_put_char(tty, op ^ 0100);
599                                 tty->column += 2;
600                                 space -= 2;
601                                 cp += 2;
602                                 nr -= 2;
603                         }
604
605                         if (no_space_left)
606                                 break;
607                 } else {
608                         if (O_OPOST(tty) &&
609                             !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
610                                 int retval = do_output_char(c, tty, space);
611                                 if (retval < 0)
612                                         break;
613                                 space -= retval;
614                         } else {
615                                 if (!space)
616                                         break;
617                                 tty_put_char(tty, c);
618                                 space -= 1;
619                         }
620                         cp += 1;
621                         nr -= 1;
622                 }
623
624                 /* When end of circular buffer reached, wrap around */
625                 if (cp >= buf_end)
626                         cp -= N_TTY_BUF_SIZE;
627         }
628
629         if (nr == 0) {
630                 tty->echo_pos = 0;
631                 tty->echo_cnt = 0;
632                 tty->echo_overrun = 0;
633         } else {
634                 int num_processed = tty->echo_cnt - nr;
635                 tty->echo_pos += num_processed;
636                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
637                 tty->echo_cnt = nr;
638                 if (num_processed > 0)
639                         tty->echo_overrun = 0;
640         }
641
642         mutex_unlock(&tty->echo_lock);
643         mutex_unlock(&tty->output_lock);
644
645         if (tty->ops->flush_chars)
646                 tty->ops->flush_chars(tty);
647 }
648
649 /**
650  *      add_echo_byte   -       add a byte to the echo buffer
651  *      @c: unicode byte to echo
652  *      @tty: terminal device
653  *
654  *      Add a character or operation byte to the echo buffer.
655  *
656  *      Should be called under the echo lock to protect the echo buffer.
657  */
658
659 static void add_echo_byte(unsigned char c, struct tty_struct *tty)
660 {
661         int     new_byte_pos;
662
663         if (tty->echo_cnt == N_TTY_BUF_SIZE) {
664                 /* Circular buffer is already at capacity */
665                 new_byte_pos = tty->echo_pos;
666
667                 /*
668                  * Since the buffer start position needs to be advanced,
669                  * be sure to step by a whole operation byte group.
670                  */
671                 if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
672                         if (tty->echo_buf[(tty->echo_pos + 1) &
673                                           (N_TTY_BUF_SIZE - 1)] ==
674                                                 ECHO_OP_ERASE_TAB) {
675                                 tty->echo_pos += 3;
676                                 tty->echo_cnt -= 2;
677                         } else {
678                                 tty->echo_pos += 2;
679                                 tty->echo_cnt -= 1;
680                         }
681                 } else {
682                         tty->echo_pos++;
683                 }
684                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
685
686                 tty->echo_overrun = 1;
687         } else {
688                 new_byte_pos = tty->echo_pos + tty->echo_cnt;
689                 new_byte_pos &= N_TTY_BUF_SIZE - 1;
690                 tty->echo_cnt++;
691         }
692
693         tty->echo_buf[new_byte_pos] = c;
694 }
695
696 /**
697  *      echo_move_back_col      -       add operation to move back a column
698  *      @tty: terminal device
699  *
700  *      Add an operation to the echo buffer to move back one column.
701  *
702  *      Locking: echo_lock to protect the echo buffer
703  */
704
705 static void echo_move_back_col(struct tty_struct *tty)
706 {
707         mutex_lock(&tty->echo_lock);
708
709         add_echo_byte(ECHO_OP_START, tty);
710         add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
711
712         mutex_unlock(&tty->echo_lock);
713 }
714
715 /**
716  *      echo_set_canon_col      -       add operation to set the canon column
717  *      @tty: terminal device
718  *
719  *      Add an operation to the echo buffer to set the canon column
720  *      to the current column.
721  *
722  *      Locking: echo_lock to protect the echo buffer
723  */
724
725 static void echo_set_canon_col(struct tty_struct *tty)
726 {
727         mutex_lock(&tty->echo_lock);
728
729         add_echo_byte(ECHO_OP_START, tty);
730         add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
731
732         mutex_unlock(&tty->echo_lock);
733 }
734
735 /**
736  *      echo_erase_tab  -       add operation to erase a tab
737  *      @num_chars: number of character columns already used
738  *      @after_tab: true if num_chars starts after a previous tab
739  *      @tty: terminal device
740  *
741  *      Add an operation to the echo buffer to erase a tab.
742  *
743  *      Called by the eraser function, which knows how many character
744  *      columns have been used since either a previous tab or the start
745  *      of input.  This information will be used later, along with
746  *      canon column (if applicable), to go back the correct number
747  *      of columns.
748  *
749  *      Locking: echo_lock to protect the echo buffer
750  */
751
752 static void echo_erase_tab(unsigned int num_chars, int after_tab,
753                            struct tty_struct *tty)
754 {
755         mutex_lock(&tty->echo_lock);
756
757         add_echo_byte(ECHO_OP_START, tty);
758         add_echo_byte(ECHO_OP_ERASE_TAB, tty);
759
760         /* We only need to know this modulo 8 (tab spacing) */
761         num_chars &= 7;
762
763         /* Set the high bit as a flag if num_chars is after a previous tab */
764         if (after_tab)
765                 num_chars |= 0x80;
766
767         add_echo_byte(num_chars, tty);
768
769         mutex_unlock(&tty->echo_lock);
770 }
771
772 /**
773  *      echo_char_raw   -       echo a character raw
774  *      @c: unicode byte to echo
775  *      @tty: terminal device
776  *
777  *      Echo user input back onto the screen. This must be called only when
778  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
779  *
780  *      This variant does not treat control characters specially.
781  *
782  *      Locking: echo_lock to protect the echo buffer
783  */
784
785 static void echo_char_raw(unsigned char c, struct tty_struct *tty)
786 {
787         mutex_lock(&tty->echo_lock);
788
789         if (c == ECHO_OP_START) {
790                 add_echo_byte(ECHO_OP_START, tty);
791                 add_echo_byte(ECHO_OP_START, tty);
792         } else {
793                 add_echo_byte(c, tty);
794         }
795
796         mutex_unlock(&tty->echo_lock);
797 }
798
799 /**
800  *      echo_char       -       echo a character
801  *      @c: unicode byte to echo
802  *      @tty: terminal device
803  *
804  *      Echo user input back onto the screen. This must be called only when
805  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
806  *
807  *      This variant tags control characters to be echoed as "^X"
808  *      (where X is the letter representing the control char).
809  *
810  *      Locking: echo_lock to protect the echo buffer
811  */
812
813 static void echo_char(unsigned char c, struct tty_struct *tty)
814 {
815         mutex_lock(&tty->echo_lock);
816
817         if (c == ECHO_OP_START) {
818                 add_echo_byte(ECHO_OP_START, tty);
819                 add_echo_byte(ECHO_OP_START, tty);
820         } else {
821                 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
822                         add_echo_byte(ECHO_OP_START, tty);
823                 add_echo_byte(c, tty);
824         }
825
826         mutex_unlock(&tty->echo_lock);
827 }
828
829 /**
830  *      finish_erasing          -       complete erase
831  *      @tty: tty doing the erase
832  */
833
834 static inline void finish_erasing(struct tty_struct *tty)
835 {
836         if (tty->erasing) {
837                 echo_char_raw('/', tty);
838                 tty->erasing = 0;
839         }
840 }
841
842 /**
843  *      eraser          -       handle erase function
844  *      @c: character input
845  *      @tty: terminal device
846  *
847  *      Perform erase and necessary output when an erase character is
848  *      present in the stream from the driver layer. Handles the complexities
849  *      of UTF-8 multibyte symbols.
850  *
851  *      Locking: read_lock for tty buffers
852  */
853
854 static void eraser(unsigned char c, struct tty_struct *tty)
855 {
856         enum { ERASE, WERASE, KILL } kill_type;
857         int head, seen_alnums, cnt;
858         unsigned long flags;
859
860         /* FIXME: locking needed ? */
861         if (tty->read_head == tty->canon_head) {
862                 /* process_output('\a', tty); */ /* what do you think? */
863                 return;
864         }
865         if (c == ERASE_CHAR(tty))
866                 kill_type = ERASE;
867         else if (c == WERASE_CHAR(tty))
868                 kill_type = WERASE;
869         else {
870                 if (!L_ECHO(tty)) {
871                         spin_lock_irqsave(&tty->read_lock, flags);
872                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
873                                           (N_TTY_BUF_SIZE - 1));
874                         tty->read_head = tty->canon_head;
875                         spin_unlock_irqrestore(&tty->read_lock, flags);
876                         return;
877                 }
878                 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
879                         spin_lock_irqsave(&tty->read_lock, flags);
880                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
881                                           (N_TTY_BUF_SIZE - 1));
882                         tty->read_head = tty->canon_head;
883                         spin_unlock_irqrestore(&tty->read_lock, flags);
884                         finish_erasing(tty);
885                         echo_char(KILL_CHAR(tty), tty);
886                         /* Add a newline if ECHOK is on and ECHOKE is off. */
887                         if (L_ECHOK(tty))
888                                 echo_char_raw('\n', tty);
889                         return;
890                 }
891                 kill_type = KILL;
892         }
893
894         seen_alnums = 0;
895         /* FIXME: Locking ?? */
896         while (tty->read_head != tty->canon_head) {
897                 head = tty->read_head;
898
899                 /* erase a single possibly multibyte character */
900                 do {
901                         head = (head - 1) & (N_TTY_BUF_SIZE-1);
902                         c = tty->read_buf[head];
903                 } while (is_continuation(c, tty) && head != tty->canon_head);
904
905                 /* do not partially erase */
906                 if (is_continuation(c, tty))
907                         break;
908
909                 if (kill_type == WERASE) {
910                         /* Equivalent to BSD's ALTWERASE. */
911                         if (isalnum(c) || c == '_')
912                                 seen_alnums++;
913                         else if (seen_alnums)
914                                 break;
915                 }
916                 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
917                 spin_lock_irqsave(&tty->read_lock, flags);
918                 tty->read_head = head;
919                 tty->read_cnt -= cnt;
920                 spin_unlock_irqrestore(&tty->read_lock, flags);
921                 if (L_ECHO(tty)) {
922                         if (L_ECHOPRT(tty)) {
923                                 if (!tty->erasing) {
924                                         echo_char_raw('\\', tty);
925                                         tty->erasing = 1;
926                                 }
927                                 /* if cnt > 1, output a multi-byte character */
928                                 echo_char(c, tty);
929                                 while (--cnt > 0) {
930                                         head = (head+1) & (N_TTY_BUF_SIZE-1);
931                                         echo_char_raw(tty->read_buf[head], tty);
932                                         echo_move_back_col(tty);
933                                 }
934                         } else if (kill_type == ERASE && !L_ECHOE(tty)) {
935                                 echo_char(ERASE_CHAR(tty), tty);
936                         } else if (c == '\t') {
937                                 unsigned int num_chars = 0;
938                                 int after_tab = 0;
939                                 unsigned long tail = tty->read_head;
940
941                                 /*
942                                  * Count the columns used for characters
943                                  * since the start of input or after a
944                                  * previous tab.
945                                  * This info is used to go back the correct
946                                  * number of columns.
947                                  */
948                                 while (tail != tty->canon_head) {
949                                         tail = (tail-1) & (N_TTY_BUF_SIZE-1);
950                                         c = tty->read_buf[tail];
951                                         if (c == '\t') {
952                                                 after_tab = 1;
953                                                 break;
954                                         } else if (iscntrl(c)) {
955                                                 if (L_ECHOCTL(tty))
956                                                         num_chars += 2;
957                                         } else if (!is_continuation(c, tty)) {
958                                                 num_chars++;
959                                         }
960                                 }
961                                 echo_erase_tab(num_chars, after_tab, tty);
962                         } else {
963                                 if (iscntrl(c) && L_ECHOCTL(tty)) {
964                                         echo_char_raw('\b', tty);
965                                         echo_char_raw(' ', tty);
966                                         echo_char_raw('\b', tty);
967                                 }
968                                 if (!iscntrl(c) || L_ECHOCTL(tty)) {
969                                         echo_char_raw('\b', tty);
970                                         echo_char_raw(' ', tty);
971                                         echo_char_raw('\b', tty);
972                                 }
973                         }
974                 }
975                 if (kill_type == ERASE)
976                         break;
977         }
978         if (tty->read_head == tty->canon_head && L_ECHO(tty))
979                 finish_erasing(tty);
980 }
981
982 /**
983  *      isig            -       handle the ISIG optio
984  *      @sig: signal
985  *      @tty: terminal
986  *      @flush: force flush
987  *
988  *      Called when a signal is being sent due to terminal input. This
989  *      may caus terminal flushing to take place according to the termios
990  *      settings and character used. Called from the driver receive_buf
991  *      path so serialized.
992  *
993  *      Locking: ctrl_lock, read_lock (both via flush buffer)
994  */
995
996 static inline void isig(int sig, struct tty_struct *tty, int flush)
997 {
998         if (tty->pgrp)
999                 kill_pgrp(tty->pgrp, sig, 1);
1000         if (flush || !L_NOFLSH(tty)) {
1001                 n_tty_flush_buffer(tty);
1002                 tty_driver_flush_buffer(tty);
1003         }
1004 }
1005
1006 /**
1007  *      n_tty_receive_break     -       handle break
1008  *      @tty: terminal
1009  *
1010  *      An RS232 break event has been hit in the incoming bitstream. This
1011  *      can cause a variety of events depending upon the termios settings.
1012  *
1013  *      Called from the receive_buf path so single threaded.
1014  */
1015
1016 static inline void n_tty_receive_break(struct tty_struct *tty)
1017 {
1018         if (I_IGNBRK(tty))
1019                 return;
1020         if (I_BRKINT(tty)) {
1021                 isig(SIGINT, tty, 1);
1022                 return;
1023         }
1024         if (I_PARMRK(tty)) {
1025                 put_tty_queue('\377', tty);
1026                 put_tty_queue('\0', tty);
1027         }
1028         put_tty_queue('\0', tty);
1029         wake_up_interruptible(&tty->read_wait);
1030 }
1031
1032 /**
1033  *      n_tty_receive_overrun   -       handle overrun reporting
1034  *      @tty: terminal
1035  *
1036  *      Data arrived faster than we could process it. While the tty
1037  *      driver has flagged this the bits that were missed are gone
1038  *      forever.
1039  *
1040  *      Called from the receive_buf path so single threaded. Does not
1041  *      need locking as num_overrun and overrun_time are function
1042  *      private.
1043  */
1044
1045 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1046 {
1047         char buf[64];
1048
1049         tty->num_overrun++;
1050         if (time_before(tty->overrun_time, jiffies - HZ) ||
1051                         time_after(tty->overrun_time, jiffies)) {
1052                 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1053                         tty_name(tty, buf),
1054                         tty->num_overrun);
1055                 tty->overrun_time = jiffies;
1056                 tty->num_overrun = 0;
1057         }
1058 }
1059
1060 /**
1061  *      n_tty_receive_parity_error      -       error notifier
1062  *      @tty: terminal device
1063  *      @c: character
1064  *
1065  *      Process a parity error and queue the right data to indicate
1066  *      the error case if necessary. Locking as per n_tty_receive_buf.
1067  */
1068 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1069                                               unsigned char c)
1070 {
1071         if (I_IGNPAR(tty))
1072                 return;
1073         if (I_PARMRK(tty)) {
1074                 put_tty_queue('\377', tty);
1075                 put_tty_queue('\0', tty);
1076                 put_tty_queue(c, tty);
1077         } else  if (I_INPCK(tty))
1078                 put_tty_queue('\0', tty);
1079         else
1080                 put_tty_queue(c, tty);
1081         wake_up_interruptible(&tty->read_wait);
1082 }
1083
1084 /**
1085  *      n_tty_receive_char      -       perform processing
1086  *      @tty: terminal device
1087  *      @c: character
1088  *
1089  *      Process an individual character of input received from the driver.
1090  *      This is serialized with respect to itself by the rules for the
1091  *      driver above.
1092  */
1093
1094 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1095 {
1096         unsigned long flags;
1097         int parmrk;
1098
1099         if (tty->raw) {
1100                 put_tty_queue(c, tty);
1101                 return;
1102         }
1103
1104         if (I_ISTRIP(tty))
1105                 c &= 0x7f;
1106         if (I_IUCLC(tty) && L_IEXTEN(tty))
1107                 c = tolower(c);
1108
1109         if (L_EXTPROC(tty)) {
1110                 put_tty_queue(c, tty);
1111                 return;
1112         }
1113
1114         if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1115             I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1116             c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1117                 start_tty(tty);
1118                 process_echoes(tty);
1119         }
1120
1121         if (tty->closing) {
1122                 if (I_IXON(tty)) {
1123                         if (c == START_CHAR(tty)) {
1124                                 start_tty(tty);
1125                                 process_echoes(tty);
1126                         } else if (c == STOP_CHAR(tty))
1127                                 stop_tty(tty);
1128                 }
1129                 return;
1130         }
1131
1132         /*
1133          * If the previous character was LNEXT, or we know that this
1134          * character is not one of the characters that we'll have to
1135          * handle specially, do shortcut processing to speed things
1136          * up.
1137          */
1138         if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1139                 tty->lnext = 0;
1140                 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1141                 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1142                         /* beep if no space */
1143                         if (L_ECHO(tty))
1144                                 process_output('\a', tty);
1145                         return;
1146                 }
1147                 if (L_ECHO(tty)) {
1148                         finish_erasing(tty);
1149                         /* Record the column of first canon char. */
1150                         if (tty->canon_head == tty->read_head)
1151                                 echo_set_canon_col(tty);
1152                         echo_char(c, tty);
1153                         process_echoes(tty);
1154                 }
1155                 if (parmrk)
1156                         put_tty_queue(c, tty);
1157                 put_tty_queue(c, tty);
1158                 return;
1159         }
1160
1161         if (I_IXON(tty)) {
1162                 if (c == START_CHAR(tty)) {
1163                         start_tty(tty);
1164                         process_echoes(tty);
1165                         return;
1166                 }
1167                 if (c == STOP_CHAR(tty)) {
1168                         stop_tty(tty);
1169                         return;
1170                 }
1171         }
1172
1173         if (L_ISIG(tty)) {
1174                 int signal;
1175                 signal = SIGINT;
1176                 if (c == INTR_CHAR(tty))
1177                         goto send_signal;
1178                 signal = SIGQUIT;
1179                 if (c == QUIT_CHAR(tty))
1180                         goto send_signal;
1181                 signal = SIGTSTP;
1182                 if (c == SUSP_CHAR(tty)) {
1183 send_signal:
1184                         /*
1185                          * Note that we do not use isig() here because we want
1186                          * the order to be:
1187                          * 1) flush, 2) echo, 3) signal
1188                          */
1189                         if (!L_NOFLSH(tty)) {
1190                                 n_tty_flush_buffer(tty);
1191                                 tty_driver_flush_buffer(tty);
1192                         }
1193                         if (I_IXON(tty))
1194                                 start_tty(tty);
1195                         if (L_ECHO(tty)) {
1196                                 echo_char(c, tty);
1197                                 process_echoes(tty);
1198                         }
1199                         if (tty->pgrp)
1200                                 kill_pgrp(tty->pgrp, signal, 1);
1201                         return;
1202                 }
1203         }
1204
1205         if (c == '\r') {
1206                 if (I_IGNCR(tty))
1207                         return;
1208                 if (I_ICRNL(tty))
1209                         c = '\n';
1210         } else if (c == '\n' && I_INLCR(tty))
1211                 c = '\r';
1212
1213         if (tty->icanon) {
1214                 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1215                     (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1216                         eraser(c, tty);
1217                         process_echoes(tty);
1218                         return;
1219                 }
1220                 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1221                         tty->lnext = 1;
1222                         if (L_ECHO(tty)) {
1223                                 finish_erasing(tty);
1224                                 if (L_ECHOCTL(tty)) {
1225                                         echo_char_raw('^', tty);
1226                                         echo_char_raw('\b', tty);
1227                                         process_echoes(tty);
1228                                 }
1229                         }
1230                         return;
1231                 }
1232                 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1233                     L_IEXTEN(tty)) {
1234                         unsigned long tail = tty->canon_head;
1235
1236                         finish_erasing(tty);
1237                         echo_char(c, tty);
1238                         echo_char_raw('\n', tty);
1239                         while (tail != tty->read_head) {
1240                                 echo_char(tty->read_buf[tail], tty);
1241                                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1242                         }
1243                         process_echoes(tty);
1244                         return;
1245                 }
1246                 if (c == '\n') {
1247                         if (tty->read_cnt >= N_TTY_BUF_SIZE) {
1248                                 if (L_ECHO(tty))
1249                                         process_output('\a', tty);
1250                                 return;
1251                         }
1252                         if (L_ECHO(tty) || L_ECHONL(tty)) {
1253                                 echo_char_raw('\n', tty);
1254                                 process_echoes(tty);
1255                         }
1256                         goto handle_newline;
1257                 }
1258                 if (c == EOF_CHAR(tty)) {
1259                         if (tty->read_cnt >= N_TTY_BUF_SIZE)
1260                                 return;
1261                         if (tty->canon_head != tty->read_head)
1262                                 set_bit(TTY_PUSH, &tty->flags);
1263                         c = __DISABLED_CHAR;
1264                         goto handle_newline;
1265                 }
1266                 if ((c == EOL_CHAR(tty)) ||
1267                     (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1268                         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1269                                  ? 1 : 0;
1270                         if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1271                                 if (L_ECHO(tty))
1272                                         process_output('\a', tty);
1273                                 return;
1274                         }
1275                         /*
1276                          * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1277                          */
1278                         if (L_ECHO(tty)) {
1279                                 /* Record the column of first canon char. */
1280                                 if (tty->canon_head == tty->read_head)
1281                                         echo_set_canon_col(tty);
1282                                 echo_char(c, tty);
1283                                 process_echoes(tty);
1284                         }
1285                         /*
1286                          * XXX does PARMRK doubling happen for
1287                          * EOL_CHAR and EOL2_CHAR?
1288                          */
1289                         if (parmrk)
1290                                 put_tty_queue(c, tty);
1291
1292 handle_newline:
1293                         spin_lock_irqsave(&tty->read_lock, flags);
1294                         set_bit(tty->read_head, tty->read_flags);
1295                         put_tty_queue_nolock(c, tty);
1296                         tty->canon_head = tty->read_head;
1297                         tty->canon_data++;
1298                         spin_unlock_irqrestore(&tty->read_lock, flags);
1299                         kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1300                         if (waitqueue_active(&tty->read_wait))
1301                                 wake_up_interruptible(&tty->read_wait);
1302                         return;
1303                 }
1304         }
1305
1306         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1307         if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1308                 /* beep if no space */
1309                 if (L_ECHO(tty))
1310                         process_output('\a', tty);
1311                 return;
1312         }
1313         if (L_ECHO(tty)) {
1314                 finish_erasing(tty);
1315                 if (c == '\n')
1316                         echo_char_raw('\n', tty);
1317                 else {
1318                         /* Record the column of first canon char. */
1319                         if (tty->canon_head == tty->read_head)
1320                                 echo_set_canon_col(tty);
1321                         echo_char(c, tty);
1322                 }
1323                 process_echoes(tty);
1324         }
1325
1326         if (parmrk)
1327                 put_tty_queue(c, tty);
1328
1329         put_tty_queue(c, tty);
1330 }
1331
1332
1333 /**
1334  *      n_tty_write_wakeup      -       asynchronous I/O notifier
1335  *      @tty: tty device
1336  *
1337  *      Required for the ptys, serial driver etc. since processes
1338  *      that attach themselves to the master and rely on ASYNC
1339  *      IO must be woken up
1340  */
1341
1342 static void n_tty_write_wakeup(struct tty_struct *tty)
1343 {
1344         if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1345                 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1346 }
1347
1348 /**
1349  *      n_tty_receive_buf       -       data receive
1350  *      @tty: terminal device
1351  *      @cp: buffer
1352  *      @fp: flag buffer
1353  *      @count: characters
1354  *
1355  *      Called by the terminal driver when a block of characters has
1356  *      been received. This function must be called from soft contexts
1357  *      not from interrupt context. The driver is responsible for making
1358  *      calls one at a time and in order (or using flush_to_ldisc)
1359  */
1360
1361 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1362                               char *fp, int count)
1363 {
1364         const unsigned char *p;
1365         char *f, flags = TTY_NORMAL;
1366         int     i;
1367         char    buf[64];
1368         unsigned long cpuflags;
1369
1370         if (!tty->read_buf)
1371                 return;
1372
1373         if (tty->real_raw) {
1374                 spin_lock_irqsave(&tty->read_lock, cpuflags);
1375                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1376                         N_TTY_BUF_SIZE - tty->read_head);
1377                 i = min(count, i);
1378                 memcpy(tty->read_buf + tty->read_head, cp, i);
1379                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1380                 tty->read_cnt += i;
1381                 cp += i;
1382                 count -= i;
1383
1384                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1385                         N_TTY_BUF_SIZE - tty->read_head);
1386                 i = min(count, i);
1387                 memcpy(tty->read_buf + tty->read_head, cp, i);
1388                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1389                 tty->read_cnt += i;
1390                 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1391         } else {
1392                 for (i = count, p = cp, f = fp; i; i--, p++) {
1393                         if (f)
1394                                 flags = *f++;
1395                         switch (flags) {
1396                         case TTY_NORMAL:
1397                                 n_tty_receive_char(tty, *p);
1398                                 break;
1399                         case TTY_BREAK:
1400                                 n_tty_receive_break(tty);
1401                                 break;
1402                         case TTY_PARITY:
1403                         case TTY_FRAME:
1404                                 n_tty_receive_parity_error(tty, *p);
1405                                 break;
1406                         case TTY_OVERRUN:
1407                                 n_tty_receive_overrun(tty);
1408                                 break;
1409                         default:
1410                                 printk(KERN_ERR "%s: unknown flag %d\n",
1411                                        tty_name(tty, buf), flags);
1412                                 break;
1413                         }
1414                 }
1415                 if (tty->ops->flush_chars)
1416                         tty->ops->flush_chars(tty);
1417         }
1418
1419         n_tty_set_room(tty);
1420
1421         if ((!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) ||
1422                 L_EXTPROC(tty)) {
1423                 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1424                 if (waitqueue_active(&tty->read_wait))
1425                         wake_up_interruptible(&tty->read_wait);
1426         }
1427
1428         /*
1429          * Check the remaining room for the input canonicalization
1430          * mode.  We don't want to throttle the driver if we're in
1431          * canonical mode and don't have a newline yet!
1432          */
1433         if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1434                 tty_throttle(tty);
1435 }
1436
1437 int is_ignored(int sig)
1438 {
1439         return (sigismember(&current->blocked, sig) ||
1440                 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1441 }
1442
1443 /**
1444  *      n_tty_set_termios       -       termios data changed
1445  *      @tty: terminal
1446  *      @old: previous data
1447  *
1448  *      Called by the tty layer when the user changes termios flags so
1449  *      that the line discipline can plan ahead. This function cannot sleep
1450  *      and is protected from re-entry by the tty layer. The user is
1451  *      guaranteed that this function will not be re-entered or in progress
1452  *      when the ldisc is closed.
1453  *
1454  *      Locking: Caller holds tty->termios_mutex
1455  */
1456
1457 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1458 {
1459         int canon_change = 1;
1460         BUG_ON(!tty);
1461
1462         if (old)
1463                 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1464         if (canon_change) {
1465                 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1466                 tty->canon_head = tty->read_tail;
1467                 tty->canon_data = 0;
1468                 tty->erasing = 0;
1469         }
1470
1471         if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1472                 wake_up_interruptible(&tty->read_wait);
1473
1474         tty->icanon = (L_ICANON(tty) != 0);
1475         if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1476                 tty->raw = 1;
1477                 tty->real_raw = 1;
1478                 n_tty_set_room(tty);
1479                 return;
1480         }
1481         if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1482             I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1483             I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1484             I_PARMRK(tty)) {
1485                 memset(tty->process_char_map, 0, 256/8);
1486
1487                 if (I_IGNCR(tty) || I_ICRNL(tty))
1488                         set_bit('\r', tty->process_char_map);
1489                 if (I_INLCR(tty))
1490                         set_bit('\n', tty->process_char_map);
1491
1492                 if (L_ICANON(tty)) {
1493                         set_bit(ERASE_CHAR(tty), tty->process_char_map);
1494                         set_bit(KILL_CHAR(tty), tty->process_char_map);
1495                         set_bit(EOF_CHAR(tty), tty->process_char_map);
1496                         set_bit('\n', tty->process_char_map);
1497                         set_bit(EOL_CHAR(tty), tty->process_char_map);
1498                         if (L_IEXTEN(tty)) {
1499                                 set_bit(WERASE_CHAR(tty),
1500                                         tty->process_char_map);
1501                                 set_bit(LNEXT_CHAR(tty),
1502                                         tty->process_char_map);
1503                                 set_bit(EOL2_CHAR(tty),
1504                                         tty->process_char_map);
1505                                 if (L_ECHO(tty))
1506                                         set_bit(REPRINT_CHAR(tty),
1507                                                 tty->process_char_map);
1508                         }
1509                 }
1510                 if (I_IXON(tty)) {
1511                         set_bit(START_CHAR(tty), tty->process_char_map);
1512                         set_bit(STOP_CHAR(tty), tty->process_char_map);
1513                 }
1514                 if (L_ISIG(tty)) {
1515                         set_bit(INTR_CHAR(tty), tty->process_char_map);
1516                         set_bit(QUIT_CHAR(tty), tty->process_char_map);
1517                         set_bit(SUSP_CHAR(tty), tty->process_char_map);
1518                 }
1519                 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1520                 tty->raw = 0;
1521                 tty->real_raw = 0;
1522         } else {
1523                 tty->raw = 1;
1524                 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1525                     (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1526                     (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1527                         tty->real_raw = 1;
1528                 else
1529                         tty->real_raw = 0;
1530         }
1531         n_tty_set_room(tty);
1532         /*
1533          * Fix tty hang when I_IXON(tty) is cleared, but the tty
1534          * been stopped by STOP_CHAR(tty) before it.
1535          */
1536         if (!I_IXON(tty) && old && (old->c_iflag & IXON) && !tty->flow_stopped) {
1537                 start_tty(tty);
1538         }
1539
1540         /* The termios change make the tty ready for I/O */
1541         wake_up_interruptible(&tty->write_wait);
1542         wake_up_interruptible(&tty->read_wait);
1543 }
1544
1545 /**
1546  *      n_tty_close             -       close the ldisc for this tty
1547  *      @tty: device
1548  *
1549  *      Called from the terminal layer when this line discipline is
1550  *      being shut down, either because of a close or becsuse of a
1551  *      discipline change. The function will not be called while other
1552  *      ldisc methods are in progress.
1553  */
1554
1555 static void n_tty_close(struct tty_struct *tty)
1556 {
1557         n_tty_flush_buffer(tty);
1558         if (tty->read_buf) {
1559                 kfree(tty->read_buf);
1560                 tty->read_buf = NULL;
1561         }
1562         if (tty->echo_buf) {
1563                 kfree(tty->echo_buf);
1564                 tty->echo_buf = NULL;
1565         }
1566 }
1567
1568 /**
1569  *      n_tty_open              -       open an ldisc
1570  *      @tty: terminal to open
1571  *
1572  *      Called when this line discipline is being attached to the
1573  *      terminal device. Can sleep. Called serialized so that no
1574  *      other events will occur in parallel. No further open will occur
1575  *      until a close.
1576  */
1577
1578 static int n_tty_open(struct tty_struct *tty)
1579 {
1580         if (!tty)
1581                 return -EINVAL;
1582
1583         /* These are ugly. Currently a malloc failure here can panic */
1584         if (!tty->read_buf) {
1585                 tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1586                 if (!tty->read_buf)
1587                         return -ENOMEM;
1588         }
1589         if (!tty->echo_buf) {
1590                 tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1591
1592                 if (!tty->echo_buf)
1593                         return -ENOMEM;
1594         }
1595         reset_buffer_flags(tty);
1596         tty_unthrottle(tty);
1597         tty->column = 0;
1598         n_tty_set_termios(tty, NULL);
1599         tty->minimum_to_wake = 1;
1600         tty->closing = 0;
1601         return 0;
1602 }
1603
1604 static inline int input_available_p(struct tty_struct *tty, int amt)
1605 {
1606         tty_flush_to_ldisc(tty);
1607         if (tty->icanon && !L_EXTPROC(tty)) {
1608                 if (tty->canon_data)
1609                         return 1;
1610         } else if (tty->read_cnt >= (amt ? amt : 1))
1611                 return 1;
1612
1613         return 0;
1614 }
1615
1616 /**
1617  *      copy_from_read_buf      -       copy read data directly
1618  *      @tty: terminal device
1619  *      @b: user data
1620  *      @nr: size of data
1621  *
1622  *      Helper function to speed up n_tty_read.  It is only called when
1623  *      ICANON is off; it copies characters straight from the tty queue to
1624  *      user space directly.  It can be profitably called twice; once to
1625  *      drain the space from the tail pointer to the (physical) end of the
1626  *      buffer, and once to drain the space from the (physical) beginning of
1627  *      the buffer to head pointer.
1628  *
1629  *      Called under the tty->atomic_read_lock sem
1630  *
1631  */
1632
1633 static int copy_from_read_buf(struct tty_struct *tty,
1634                                       unsigned char __user **b,
1635                                       size_t *nr)
1636
1637 {
1638         int retval;
1639         size_t n;
1640         unsigned long flags;
1641
1642         retval = 0;
1643         spin_lock_irqsave(&tty->read_lock, flags);
1644         n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1645         n = min(*nr, n);
1646         spin_unlock_irqrestore(&tty->read_lock, flags);
1647         if (n) {
1648                 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1649                 n -= retval;
1650                 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1651                 spin_lock_irqsave(&tty->read_lock, flags);
1652                 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1653                 tty->read_cnt -= n;
1654                 /* Turn single EOF into zero-length read */
1655                 if (L_EXTPROC(tty) && tty->icanon && n == 1) {
1656                         if (!tty->read_cnt && (*b)[n-1] == EOF_CHAR(tty))
1657                                 n--;
1658                 }
1659                 spin_unlock_irqrestore(&tty->read_lock, flags);
1660                 *b += n;
1661                 *nr -= n;
1662         }
1663         return retval;
1664 }
1665
1666 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1667                                                         size_t, loff_t *);
1668
1669 /**
1670  *      job_control             -       check job control
1671  *      @tty: tty
1672  *      @file: file handle
1673  *
1674  *      Perform job control management checks on this file/tty descriptor
1675  *      and if appropriate send any needed signals and return a negative
1676  *      error code if action should be taken.
1677  *
1678  *      FIXME:
1679  *      Locking: None - redirected write test is safe, testing
1680  *      current->signal should possibly lock current->sighand
1681  *      pgrp locking ?
1682  */
1683
1684 static int job_control(struct tty_struct *tty, struct file *file)
1685 {
1686         /* Job control check -- must be done at start and after
1687            every sleep (POSIX.1 7.1.1.4). */
1688         /* NOTE: not yet done after every sleep pending a thorough
1689            check of the logic of this change. -- jlc */
1690         /* don't stop on /dev/console */
1691         if (file->f_op->write != redirected_tty_write &&
1692             current->signal->tty == tty) {
1693                 if (!tty->pgrp)
1694                         printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1695                 else if (task_pgrp(current) != tty->pgrp) {
1696                         if (is_ignored(SIGTTIN) ||
1697                             is_current_pgrp_orphaned())
1698                                 return -EIO;
1699                         kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1700                         set_thread_flag(TIF_SIGPENDING);
1701                         return -ERESTARTSYS;
1702                 }
1703         }
1704         return 0;
1705 }
1706
1707
1708 /**
1709  *      n_tty_read              -       read function for tty
1710  *      @tty: tty device
1711  *      @file: file object
1712  *      @buf: userspace buffer pointer
1713  *      @nr: size of I/O
1714  *
1715  *      Perform reads for the line discipline. We are guaranteed that the
1716  *      line discipline will not be closed under us but we may get multiple
1717  *      parallel readers and must handle this ourselves. We may also get
1718  *      a hangup. Always called in user context, may sleep.
1719  *
1720  *      This code must be sure never to sleep through a hangup.
1721  */
1722
1723 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1724                          unsigned char __user *buf, size_t nr)
1725 {
1726         unsigned char __user *b = buf;
1727         DECLARE_WAITQUEUE(wait, current);
1728         int c;
1729         int minimum, time;
1730         ssize_t retval = 0;
1731         ssize_t size;
1732         long timeout;
1733         unsigned long flags;
1734         int packet;
1735
1736 do_it_again:
1737
1738         if (WARN_ON(!tty->read_buf))
1739                 return -EAGAIN;
1740
1741         c = job_control(tty, file);
1742         if (c < 0)
1743                 return c;
1744
1745         minimum = time = 0;
1746         timeout = MAX_SCHEDULE_TIMEOUT;
1747         if (!tty->icanon) {
1748                 time = (HZ / 10) * TIME_CHAR(tty);
1749                 minimum = MIN_CHAR(tty);
1750                 if (minimum) {
1751                         if (time)
1752                                 tty->minimum_to_wake = 1;
1753                         else if (!waitqueue_active(&tty->read_wait) ||
1754                                  (tty->minimum_to_wake > minimum))
1755                                 tty->minimum_to_wake = minimum;
1756                 } else {
1757                         timeout = 0;
1758                         if (time) {
1759                                 timeout = time;
1760                                 time = 0;
1761                         }
1762                         tty->minimum_to_wake = minimum = 1;
1763                 }
1764         }
1765
1766         /*
1767          *      Internal serialization of reads.
1768          */
1769         if (file->f_flags & O_NONBLOCK) {
1770                 if (!mutex_trylock(&tty->atomic_read_lock))
1771                         return -EAGAIN;
1772         } else {
1773                 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1774                         return -ERESTARTSYS;
1775         }
1776         packet = tty->packet;
1777
1778         add_wait_queue(&tty->read_wait, &wait);
1779         while (nr) {
1780                 /* First test for status change. */
1781                 if (packet && tty->link->ctrl_status) {
1782                         unsigned char cs;
1783                         if (b != buf)
1784                                 break;
1785                         spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1786                         cs = tty->link->ctrl_status;
1787                         tty->link->ctrl_status = 0;
1788                         spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1789                         if (tty_put_user(tty, cs, b++)) {
1790                                 retval = -EFAULT;
1791                                 b--;
1792                                 break;
1793                         }
1794                         nr--;
1795                         break;
1796                 }
1797                 /* This statement must be first before checking for input
1798                    so that any interrupt will set the state back to
1799                    TASK_RUNNING. */
1800                 set_current_state(TASK_INTERRUPTIBLE);
1801
1802                 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1803                     ((minimum - (b - buf)) >= 1))
1804                         tty->minimum_to_wake = (minimum - (b - buf));
1805
1806                 if (!input_available_p(tty, 0)) {
1807                         if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1808                                 retval = -EIO;
1809                                 break;
1810                         }
1811                         if (tty_hung_up_p(file))
1812                                 break;
1813                         if (!timeout)
1814                                 break;
1815                         if (file->f_flags & O_NONBLOCK) {
1816                                 retval = -EAGAIN;
1817                                 break;
1818                         }
1819                         if (signal_pending(current)) {
1820                                 retval = -ERESTARTSYS;
1821                                 break;
1822                         }
1823                         /* FIXME: does n_tty_set_room need locking ? */
1824                         n_tty_set_room(tty);
1825                         timeout = schedule_timeout(timeout);
1826                         BUG_ON(!tty->read_buf);
1827                         continue;
1828                 }
1829                 __set_current_state(TASK_RUNNING);
1830
1831                 /* Deal with packet mode. */
1832                 if (packet && b == buf) {
1833                         if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1834                                 retval = -EFAULT;
1835                                 b--;
1836                                 break;
1837                         }
1838                         nr--;
1839                 }
1840
1841                 if (tty->icanon && !L_EXTPROC(tty)) {
1842                         /* N.B. avoid overrun if nr == 0 */
1843                         while (nr && tty->read_cnt) {
1844                                 int eol;
1845
1846                                 eol = test_and_clear_bit(tty->read_tail,
1847                                                 tty->read_flags);
1848                                 c = tty->read_buf[tty->read_tail];
1849                                 spin_lock_irqsave(&tty->read_lock, flags);
1850                                 tty->read_tail = ((tty->read_tail+1) &
1851                                                   (N_TTY_BUF_SIZE-1));
1852                                 tty->read_cnt--;
1853                                 if (eol) {
1854                                         /* this test should be redundant:
1855                                          * we shouldn't be reading data if
1856                                          * canon_data is 0
1857                                          */
1858                                         if (--tty->canon_data < 0)
1859                                                 tty->canon_data = 0;
1860                                 }
1861                                 spin_unlock_irqrestore(&tty->read_lock, flags);
1862
1863                                 if (!eol || (c != __DISABLED_CHAR)) {
1864                                         if (tty_put_user(tty, c, b++)) {
1865                                                 retval = -EFAULT;
1866                                                 b--;
1867                                                 break;
1868                                         }
1869                                         nr--;
1870                                 }
1871                                 if (eol) {
1872                                         tty_audit_push(tty);
1873                                         break;
1874                                 }
1875                         }
1876                         if (retval)
1877                                 break;
1878                 } else {
1879                         int uncopied;
1880                         /* The copy function takes the read lock and handles
1881                            locking internally for this case */
1882                         uncopied = copy_from_read_buf(tty, &b, &nr);
1883                         uncopied += copy_from_read_buf(tty, &b, &nr);
1884                         if (uncopied) {
1885                                 retval = -EFAULT;
1886                                 break;
1887                         }
1888                 }
1889
1890                 /* If there is enough space in the read buffer now, let the
1891                  * low-level driver know. We use n_tty_chars_in_buffer() to
1892                  * check the buffer, as it now knows about canonical mode.
1893                  * Otherwise, if the driver is throttled and the line is
1894                  * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1895                  * we won't get any more characters.
1896                  */
1897                 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1898                         n_tty_set_room(tty);
1899                         check_unthrottle(tty);
1900                 }
1901
1902                 if (b - buf >= minimum)
1903                         break;
1904                 if (time)
1905                         timeout = time;
1906         }
1907         mutex_unlock(&tty->atomic_read_lock);
1908         remove_wait_queue(&tty->read_wait, &wait);
1909
1910         if (!waitqueue_active(&tty->read_wait))
1911                 tty->minimum_to_wake = minimum;
1912
1913         __set_current_state(TASK_RUNNING);
1914         size = b - buf;
1915         if (size) {
1916                 retval = size;
1917                 if (nr)
1918                         clear_bit(TTY_PUSH, &tty->flags);
1919         } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1920                 goto do_it_again;
1921
1922         n_tty_set_room(tty);
1923         return retval;
1924 }
1925
1926 /**
1927  *      n_tty_write             -       write function for tty
1928  *      @tty: tty device
1929  *      @file: file object
1930  *      @buf: userspace buffer pointer
1931  *      @nr: size of I/O
1932  *
1933  *      Write function of the terminal device.  This is serialized with
1934  *      respect to other write callers but not to termios changes, reads
1935  *      and other such events.  Since the receive code will echo characters,
1936  *      thus calling driver write methods, the output_lock is used in
1937  *      the output processing functions called here as well as in the
1938  *      echo processing function to protect the column state and space
1939  *      left in the buffer.
1940  *
1941  *      This code must be sure never to sleep through a hangup.
1942  *
1943  *      Locking: output_lock to protect column state and space left
1944  *               (note that the process_output*() functions take this
1945  *                lock themselves)
1946  */
1947
1948 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1949                            const unsigned char *buf, size_t nr)
1950 {
1951         const unsigned char *b = buf;
1952         DECLARE_WAITQUEUE(wait, current);
1953         int c;
1954         ssize_t retval = 0;
1955
1956         /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1957         if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1958                 retval = tty_check_change(tty);
1959                 if (retval)
1960                         return retval;
1961         }
1962
1963         /* Write out any echoed characters that are still pending */
1964         process_echoes(tty);
1965
1966         add_wait_queue(&tty->write_wait, &wait);
1967         while (1) {
1968                 set_current_state(TASK_INTERRUPTIBLE);
1969                 if (signal_pending(current)) {
1970                         retval = -ERESTARTSYS;
1971                         break;
1972                 }
1973                 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1974                         retval = -EIO;
1975                         break;
1976                 }
1977                 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1978                         while (nr > 0) {
1979                                 ssize_t num = process_output_block(tty, b, nr);
1980                                 if (num < 0) {
1981                                         if (num == -EAGAIN)
1982                                                 break;
1983                                         retval = num;
1984                                         goto break_out;
1985                                 }
1986                                 b += num;
1987                                 nr -= num;
1988                                 if (nr == 0)
1989                                         break;
1990                                 c = *b;
1991                                 if (process_output(c, tty) < 0)
1992                                         break;
1993                                 b++; nr--;
1994                         }
1995                         if (tty->ops->flush_chars)
1996                                 tty->ops->flush_chars(tty);
1997                 } else {
1998                         while (nr > 0) {
1999                                 c = tty->ops->write(tty, b, nr);
2000                                 if (c < 0) {
2001                                         retval = c;
2002                                         goto break_out;
2003                                 }
2004                                 if (!c)
2005                                         break;
2006                                 b += c;
2007                                 nr -= c;
2008                         }
2009                 }
2010                 if (!nr)
2011                         break;
2012                 if (file->f_flags & O_NONBLOCK) {
2013                         retval = -EAGAIN;
2014                         break;
2015                 }
2016                 schedule();
2017         }
2018 break_out:
2019         __set_current_state(TASK_RUNNING);
2020         remove_wait_queue(&tty->write_wait, &wait);
2021         if (b - buf != nr && tty->fasync)
2022                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2023         return (b - buf) ? b - buf : retval;
2024 }
2025
2026 /**
2027  *      n_tty_poll              -       poll method for N_TTY
2028  *      @tty: terminal device
2029  *      @file: file accessing it
2030  *      @wait: poll table
2031  *
2032  *      Called when the line discipline is asked to poll() for data or
2033  *      for special events. This code is not serialized with respect to
2034  *      other events save open/close.
2035  *
2036  *      This code must be sure never to sleep through a hangup.
2037  *      Called without the kernel lock held - fine
2038  */
2039
2040 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2041                                                         poll_table *wait)
2042 {
2043         unsigned int mask = 0;
2044
2045         poll_wait(file, &tty->read_wait, wait);
2046         poll_wait(file, &tty->write_wait, wait);
2047         if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2048                 mask |= POLLIN | POLLRDNORM;
2049         if (tty->packet && tty->link->ctrl_status)
2050                 mask |= POLLPRI | POLLIN | POLLRDNORM;
2051         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2052                 mask |= POLLHUP;
2053         if (tty_hung_up_p(file))
2054                 mask |= POLLHUP;
2055         if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2056                 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2057                         tty->minimum_to_wake = MIN_CHAR(tty);
2058                 else
2059                         tty->minimum_to_wake = 1;
2060         }
2061         if (tty->ops->write && !tty_is_writelocked(tty) &&
2062                         tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2063                         tty_write_room(tty) > 0)
2064                 mask |= POLLOUT | POLLWRNORM;
2065         return mask;
2066 }
2067
2068 static unsigned long inq_canon(struct tty_struct *tty)
2069 {
2070         int nr, head, tail;
2071
2072         if (!tty->canon_data)
2073                 return 0;
2074         head = tty->canon_head;
2075         tail = tty->read_tail;
2076         nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2077         /* Skip EOF-chars.. */
2078         while (head != tail) {
2079                 if (test_bit(tail, tty->read_flags) &&
2080                     tty->read_buf[tail] == __DISABLED_CHAR)
2081                         nr--;
2082                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2083         }
2084         return nr;
2085 }
2086
2087 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2088                        unsigned int cmd, unsigned long arg)
2089 {
2090         int retval;
2091
2092         switch (cmd) {
2093         case TIOCOUTQ:
2094                 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2095         case TIOCINQ:
2096                 /* FIXME: Locking */
2097                 retval = tty->read_cnt;
2098                 if (L_ICANON(tty))
2099                         retval = inq_canon(tty);
2100                 return put_user(retval, (unsigned int __user *) arg);
2101         default:
2102                 return n_tty_ioctl_helper(tty, file, cmd, arg);
2103         }
2104 }
2105
2106 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2107         .magic           = TTY_LDISC_MAGIC,
2108         .name            = "n_tty",
2109         .open            = n_tty_open,
2110         .close           = n_tty_close,
2111         .flush_buffer    = n_tty_flush_buffer,
2112         .chars_in_buffer = n_tty_chars_in_buffer,
2113         .read            = n_tty_read,
2114         .write           = n_tty_write,
2115         .ioctl           = n_tty_ioctl,
2116         .set_termios     = n_tty_set_termios,
2117         .poll            = n_tty_poll,
2118         .receive_buf     = n_tty_receive_buf,
2119         .write_wakeup    = n_tty_write_wakeup
2120 };
2121
2122 /**
2123  *      n_tty_inherit_ops       -       inherit N_TTY methods
2124  *      @ops: struct tty_ldisc_ops where to save N_TTY methods
2125  *
2126  *      Used by a generic struct tty_ldisc_ops to easily inherit N_TTY
2127  *      methods.
2128  */
2129
2130 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2131 {
2132         *ops = tty_ldisc_N_TTY;
2133         ops->owner = NULL;
2134         ops->refcount = ops->flags = 0;
2135 }
2136 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);