bdae8327143c3400497829c6080817535af52eb2
[linux-3.10.git] / drivers / char / 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 #include <asm/system.h>
54
55 /* number of characters left in xmit buffer before select has we have room */
56 #define WAKEUP_CHARS 256
57
58 /*
59  * This defines the low- and high-watermarks for throttling and
60  * unthrottling the TTY driver.  These watermarks are used for
61  * controlling the space in the read buffer.
62  */
63 #define TTY_THRESHOLD_THROTTLE          128 /* now based on remaining room */
64 #define TTY_THRESHOLD_UNTHROTTLE        128
65
66 /*
67  * Special byte codes used in the echo buffer to represent operations
68  * or special handling of characters.  Bytes in the echo buffer that
69  * are not part of such special blocks are treated as normal character
70  * codes.
71  */
72 #define ECHO_OP_START 0xff
73 #define ECHO_OP_MOVE_BACK_COL 0x80
74 #define ECHO_OP_SET_CANON_COL 0x81
75 #define ECHO_OP_ERASE_TAB 0x82
76
77 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
78                                unsigned char __user *ptr)
79 {
80         tty_audit_add_data(tty, &x, 1);
81         return put_user(x, ptr);
82 }
83
84 /**
85  *      n_tty_set__room -       receive space
86  *      @tty: terminal
87  *
88  *      Called by the driver to find out how much data it is
89  *      permitted to feed to the line discipline without any being lost
90  *      and thus to manage flow control. Not serialized. Answers for the
91  *      "instant".
92  */
93
94 static void n_tty_set_room(struct tty_struct *tty)
95 {
96         /* tty->read_cnt is not read locked ? */
97         int     left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
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         tty->receive_room = left;
108 }
109
110 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
111 {
112         if (tty->read_cnt < N_TTY_BUF_SIZE) {
113                 tty->read_buf[tty->read_head] = c;
114                 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
115                 tty->read_cnt++;
116         }
117 }
118
119 /**
120  *      put_tty_queue           -       add character to tty
121  *      @c: character
122  *      @tty: tty device
123  *
124  *      Add a character to the tty read_buf queue. This is done under the
125  *      read_lock to serialize character addition and also to protect us
126  *      against parallel reads or flushes
127  */
128
129 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
130 {
131         unsigned long flags;
132         /*
133          *      The problem of stomping on the buffers ends here.
134          *      Why didn't anyone see this one coming? --AJK
135         */
136         spin_lock_irqsave(&tty->read_lock, flags);
137         put_tty_queue_nolock(c, tty);
138         spin_unlock_irqrestore(&tty->read_lock, flags);
139 }
140
141 /**
142  *      check_unthrottle        -       allow new receive data
143  *      @tty; tty device
144  *
145  *      Check whether to call the driver unthrottle functions
146  *
147  *      Can sleep, may be called under the atomic_read_lock mutex but
148  *      this is not guaranteed.
149  */
150 static void check_unthrottle(struct tty_struct *tty)
151 {
152         if (tty->count)
153                 tty_unthrottle(tty);
154 }
155
156 /**
157  *      reset_buffer_flags      -       reset buffer state
158  *      @tty: terminal to reset
159  *
160  *      Reset the read buffer counters, clear the flags,
161  *      and make sure the driver is unthrottled. Called
162  *      from n_tty_open() and n_tty_flush_buffer().
163  *
164  *      Locking: tty_read_lock for read fields.
165  */
166
167 static void reset_buffer_flags(struct tty_struct *tty)
168 {
169         unsigned long flags;
170
171         spin_lock_irqsave(&tty->read_lock, flags);
172         tty->read_head = tty->read_tail = tty->read_cnt = 0;
173         spin_unlock_irqrestore(&tty->read_lock, flags);
174
175         mutex_lock(&tty->echo_lock);
176         tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
177         mutex_unlock(&tty->echo_lock);
178
179         tty->canon_head = tty->canon_data = tty->erasing = 0;
180         memset(&tty->read_flags, 0, sizeof tty->read_flags);
181         n_tty_set_room(tty);
182         check_unthrottle(tty);
183 }
184
185 /**
186  *      n_tty_flush_buffer      -       clean input queue
187  *      @tty:   terminal device
188  *
189  *      Flush the input buffer. Called when the line discipline is
190  *      being closed, when the tty layer wants the buffer flushed (eg
191  *      at hangup) or when the N_TTY line discipline internally has to
192  *      clean the pending queue (for example some signals).
193  *
194  *      Locking: ctrl_lock, read_lock.
195  */
196
197 static void n_tty_flush_buffer(struct tty_struct *tty)
198 {
199         unsigned long flags;
200         /* clear everything and unthrottle the driver */
201         reset_buffer_flags(tty);
202
203         if (!tty->link)
204                 return;
205
206         spin_lock_irqsave(&tty->ctrl_lock, flags);
207         if (tty->link->packet) {
208                 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
209                 wake_up_interruptible(&tty->link->read_wait);
210         }
211         spin_unlock_irqrestore(&tty->ctrl_lock, flags);
212 }
213
214 /**
215  *      n_tty_chars_in_buffer   -       report available bytes
216  *      @tty: tty device
217  *
218  *      Report the number of characters buffered to be delivered to user
219  *      at this instant in time.
220  *
221  *      Locking: read_lock
222  */
223
224 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
225 {
226         unsigned long flags;
227         ssize_t n = 0;
228
229         spin_lock_irqsave(&tty->read_lock, flags);
230         if (!tty->icanon) {
231                 n = tty->read_cnt;
232         } else if (tty->canon_data) {
233                 n = (tty->canon_head > tty->read_tail) ?
234                         tty->canon_head - tty->read_tail :
235                         tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
236         }
237         spin_unlock_irqrestore(&tty->read_lock, flags);
238         return n;
239 }
240
241 /**
242  *      is_utf8_continuation    -       utf8 multibyte check
243  *      @c: byte to check
244  *
245  *      Returns true if the utf8 character 'c' is a multibyte continuation
246  *      character. We use this to correctly compute the on screen size
247  *      of the character when printing
248  */
249
250 static inline int is_utf8_continuation(unsigned char c)
251 {
252         return (c & 0xc0) == 0x80;
253 }
254
255 /**
256  *      is_continuation         -       multibyte check
257  *      @c: byte to check
258  *
259  *      Returns true if the utf8 character 'c' is a multibyte continuation
260  *      character and the terminal is in unicode mode.
261  */
262
263 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
264 {
265         return I_IUTF8(tty) && is_utf8_continuation(c);
266 }
267
268 /**
269  *      do_output_char                  -       output one character
270  *      @c: character (or partial unicode symbol)
271  *      @tty: terminal device
272  *      @space: space available in tty driver write buffer
273  *
274  *      This is a helper function that handles one output character
275  *      (including special characters like TAB, CR, LF, etc.),
276  *      doing OPOST processing and putting the results in the
277  *      tty driver's write buffer.
278  *
279  *      Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
280  *      and NLDLY.  They simply aren't relevant in the world today.
281  *      If you ever need them, add them here.
282  *
283  *      Returns the number of bytes of buffer space used or -1 if
284  *      no space left.
285  *
286  *      Locking: should be called under the output_lock to protect
287  *               the column state and space left in the buffer
288  */
289
290 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
291 {
292         int     spaces;
293
294         if (!space)
295                 return -1;
296
297         switch (c) {
298         case '\n':
299                 if (O_ONLRET(tty))
300                         tty->column = 0;
301                 if (O_ONLCR(tty)) {
302                         if (space < 2)
303                                 return -1;
304                         tty->canon_column = tty->column = 0;
305                         tty->ops->write(tty, "\r\n", 2);
306                         return 2;
307                 }
308                 tty->canon_column = tty->column;
309                 break;
310         case '\r':
311                 if (O_ONOCR(tty) && tty->column == 0)
312                         return 0;
313                 if (O_OCRNL(tty)) {
314                         c = '\n';
315                         if (O_ONLRET(tty))
316                                 tty->canon_column = tty->column = 0;
317                         break;
318                 }
319                 tty->canon_column = tty->column = 0;
320                 break;
321         case '\t':
322                 spaces = 8 - (tty->column & 7);
323                 if (O_TABDLY(tty) == XTABS) {
324                         if (space < spaces)
325                                 return -1;
326                         tty->column += spaces;
327                         tty->ops->write(tty, "        ", spaces);
328                         return spaces;
329                 }
330                 tty->column += spaces;
331                 break;
332         case '\b':
333                 if (tty->column > 0)
334                         tty->column--;
335                 break;
336         default:
337                 if (!iscntrl(c)) {
338                         if (O_OLCUC(tty))
339                                 c = toupper(c);
340                         if (!is_continuation(c, tty))
341                                 tty->column++;
342                 }
343                 break;
344         }
345
346         tty_put_char(tty, c);
347         return 1;
348 }
349
350 /**
351  *      process_output                  -       output post processor
352  *      @c: character (or partial unicode symbol)
353  *      @tty: terminal device
354  *
355  *      Output one character with OPOST processing.
356  *      Returns -1 when the output device is full and the character
357  *      must be retried.
358  *
359  *      Locking: output_lock to protect column state and space left
360  *               (also, this is called from n_tty_write under the
361  *                tty layer write lock)
362  */
363
364 static int process_output(unsigned char c, struct tty_struct *tty)
365 {
366         int     space, retval;
367
368         mutex_lock(&tty->output_lock);
369
370         space = tty_write_room(tty);
371         retval = do_output_char(c, tty, space);
372
373         mutex_unlock(&tty->output_lock);
374         if (retval < 0)
375                 return -1;
376         else
377                 return 0;
378 }
379
380 /**
381  *      process_output_block            -       block post processor
382  *      @tty: terminal device
383  *      @buf: character buffer
384  *      @nr: number of bytes to output
385  *
386  *      Output a block of characters with OPOST processing.
387  *      Returns the number of characters output.
388  *
389  *      This path is used to speed up block console writes, among other
390  *      things when processing blocks of output data. It handles only
391  *      the simple cases normally found and helps to generate blocks of
392  *      symbols for the console driver and thus improve performance.
393  *
394  *      Locking: output_lock to protect column state and space left
395  *               (also, this is called from n_tty_write under the
396  *                tty layer write lock)
397  */
398
399 static ssize_t process_output_block(struct tty_struct *tty,
400                                     const unsigned char *buf, unsigned int nr)
401 {
402         int     space;
403         int     i;
404         const unsigned char *cp;
405
406         mutex_lock(&tty->output_lock);
407
408         space = tty_write_room(tty);
409         if (!space) {
410                 mutex_unlock(&tty->output_lock);
411                 return 0;
412         }
413         if (nr > space)
414                 nr = space;
415
416         for (i = 0, cp = buf; i < nr; i++, cp++) {
417                 unsigned char c = *cp;
418
419                 switch (c) {
420                 case '\n':
421                         if (O_ONLRET(tty))
422                                 tty->column = 0;
423                         if (O_ONLCR(tty))
424                                 goto break_out;
425                         tty->canon_column = tty->column;
426                         break;
427                 case '\r':
428                         if (O_ONOCR(tty) && tty->column == 0)
429                                 goto break_out;
430                         if (O_OCRNL(tty))
431                                 goto break_out;
432                         tty->canon_column = tty->column = 0;
433                         break;
434                 case '\t':
435                         goto break_out;
436                 case '\b':
437                         if (tty->column > 0)
438                                 tty->column--;
439                         break;
440                 default:
441                         if (!iscntrl(c)) {
442                                 if (O_OLCUC(tty))
443                                         goto break_out;
444                                 if (!is_continuation(c, tty))
445                                         tty->column++;
446                         }
447                         break;
448                 }
449         }
450 break_out:
451         i = tty->ops->write(tty, buf, i);
452
453         mutex_unlock(&tty->output_lock);
454         return i;
455 }
456
457 /**
458  *      process_echoes  -       write pending echo characters
459  *      @tty: terminal device
460  *
461  *      Write previously buffered echo (and other ldisc-generated)
462  *      characters to the tty.
463  *
464  *      Characters generated by the ldisc (including echoes) need to
465  *      be buffered because the driver's write buffer can fill during
466  *      heavy program output.  Echoing straight to the driver will
467  *      often fail under these conditions, causing lost characters and
468  *      resulting mismatches of ldisc state information.
469  *
470  *      Since the ldisc state must represent the characters actually sent
471  *      to the driver at the time of the write, operations like certain
472  *      changes in column state are also saved in the buffer and executed
473  *      here.
474  *
475  *      A circular fifo buffer is used so that the most recent characters
476  *      are prioritized.  Also, when control characters are echoed with a
477  *      prefixed "^", the pair is treated atomically and thus not separated.
478  *
479  *      Locking: output_lock to protect column state and space left,
480  *               echo_lock to protect the echo buffer
481  */
482
483 static void process_echoes(struct tty_struct *tty)
484 {
485         int     space, nr;
486         unsigned char c;
487         unsigned char *cp, *buf_end;
488
489         if (!tty->echo_cnt)
490                 return;
491
492         mutex_lock(&tty->output_lock);
493         mutex_lock(&tty->echo_lock);
494
495         space = tty_write_room(tty);
496
497         buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
498         cp = tty->echo_buf + tty->echo_pos;
499         nr = tty->echo_cnt;
500         while (nr > 0) {
501                 c = *cp;
502                 if (c == ECHO_OP_START) {
503                         unsigned char op;
504                         unsigned char *opp;
505                         int no_space_left = 0;
506
507                         /*
508                          * If the buffer byte is the start of a multi-byte
509                          * operation, get the next byte, which is either the
510                          * op code or a control character value.
511                          */
512                         opp = cp + 1;
513                         if (opp == buf_end)
514                                 opp -= N_TTY_BUF_SIZE;
515                         op = *opp;
516
517                         switch (op) {
518                                 unsigned int num_chars, num_bs;
519
520                         case ECHO_OP_ERASE_TAB:
521                                 if (++opp == buf_end)
522                                         opp -= N_TTY_BUF_SIZE;
523                                 num_chars = *opp;
524
525                                 /*
526                                  * Determine how many columns to go back
527                                  * in order to erase the tab.
528                                  * This depends on the number of columns
529                                  * used by other characters within the tab
530                                  * area.  If this (modulo 8) count is from
531                                  * the start of input rather than from a
532                                  * previous tab, we offset by canon column.
533                                  * Otherwise, tab spacing is normal.
534                                  */
535                                 if (!(num_chars & 0x80))
536                                         num_chars += tty->canon_column;
537                                 num_bs = 8 - (num_chars & 7);
538
539                                 if (num_bs > space) {
540                                         no_space_left = 1;
541                                         break;
542                                 }
543                                 space -= num_bs;
544                                 while (num_bs--) {
545                                         tty_put_char(tty, '\b');
546                                         if (tty->column > 0)
547                                                 tty->column--;
548                                 }
549                                 cp += 3;
550                                 nr -= 3;
551                                 break;
552
553                         case ECHO_OP_SET_CANON_COL:
554                                 tty->canon_column = tty->column;
555                                 cp += 2;
556                                 nr -= 2;
557                                 break;
558
559                         case ECHO_OP_MOVE_BACK_COL:
560                                 if (tty->column > 0)
561                                         tty->column--;
562                                 cp += 2;
563                                 nr -= 2;
564                                 break;
565
566                         case ECHO_OP_START:
567                                 /* This is an escaped echo op start code */
568                                 if (!space) {
569                                         no_space_left = 1;
570                                         break;
571                                 }
572                                 tty_put_char(tty, ECHO_OP_START);
573                                 tty->column++;
574                                 space--;
575                                 cp += 2;
576                                 nr -= 2;
577                                 break;
578
579                         default:
580                                 /*
581                                  * If the op is not a special byte code,
582                                  * it is a ctrl char tagged to be echoed
583                                  * as "^X" (where X is the letter
584                                  * representing the control char).
585                                  * Note that we must ensure there is
586                                  * enough space for the whole ctrl pair.
587                                  *
588                                  */
589                                 if (space < 2) {
590                                         no_space_left = 1;
591                                         break;
592                                 }
593                                 tty_put_char(tty, '^');
594                                 tty_put_char(tty, op ^ 0100);
595                                 tty->column += 2;
596                                 space -= 2;
597                                 cp += 2;
598                                 nr -= 2;
599                         }
600
601                         if (no_space_left)
602                                 break;
603                 } else {
604                         if (O_OPOST(tty) &&
605                             !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
606                                 int retval = do_output_char(c, tty, space);
607                                 if (retval < 0)
608                                         break;
609                                 space -= retval;
610                         } else {
611                                 if (!space)
612                                         break;
613                                 tty_put_char(tty, c);
614                                 space -= 1;
615                         }
616                         cp += 1;
617                         nr -= 1;
618                 }
619
620                 /* When end of circular buffer reached, wrap around */
621                 if (cp >= buf_end)
622                         cp -= N_TTY_BUF_SIZE;
623         }
624
625         if (nr == 0) {
626                 tty->echo_pos = 0;
627                 tty->echo_cnt = 0;
628                 tty->echo_overrun = 0;
629         } else {
630                 int num_processed = tty->echo_cnt - nr;
631                 tty->echo_pos += num_processed;
632                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
633                 tty->echo_cnt = nr;
634                 if (num_processed > 0)
635                         tty->echo_overrun = 0;
636         }
637
638         mutex_unlock(&tty->echo_lock);
639         mutex_unlock(&tty->output_lock);
640
641         if (tty->ops->flush_chars)
642                 tty->ops->flush_chars(tty);
643 }
644
645 /**
646  *      add_echo_byte   -       add a byte to the echo buffer
647  *      @c: unicode byte to echo
648  *      @tty: terminal device
649  *
650  *      Add a character or operation byte to the echo buffer.
651  *
652  *      Should be called under the echo lock to protect the echo buffer.
653  */
654
655 static void add_echo_byte(unsigned char c, struct tty_struct *tty)
656 {
657         int     new_byte_pos;
658
659         if (tty->echo_cnt == N_TTY_BUF_SIZE) {
660                 /* Circular buffer is already at capacity */
661                 new_byte_pos = tty->echo_pos;
662
663                 /*
664                  * Since the buffer start position needs to be advanced,
665                  * be sure to step by a whole operation byte group.
666                  */
667                 if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
668                         if (tty->echo_buf[(tty->echo_pos + 1) &
669                                           (N_TTY_BUF_SIZE - 1)] ==
670                                                 ECHO_OP_ERASE_TAB) {
671                                 tty->echo_pos += 3;
672                                 tty->echo_cnt -= 2;
673                         } else {
674                                 tty->echo_pos += 2;
675                                 tty->echo_cnt -= 1;
676                         }
677                 } else {
678                         tty->echo_pos++;
679                 }
680                 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
681
682                 tty->echo_overrun = 1;
683         } else {
684                 new_byte_pos = tty->echo_pos + tty->echo_cnt;
685                 new_byte_pos &= N_TTY_BUF_SIZE - 1;
686                 tty->echo_cnt++;
687         }
688
689         tty->echo_buf[new_byte_pos] = c;
690 }
691
692 /**
693  *      echo_move_back_col      -       add operation to move back a column
694  *      @tty: terminal device
695  *
696  *      Add an operation to the echo buffer to move back one column.
697  *
698  *      Locking: echo_lock to protect the echo buffer
699  */
700
701 static void echo_move_back_col(struct tty_struct *tty)
702 {
703         mutex_lock(&tty->echo_lock);
704
705         add_echo_byte(ECHO_OP_START, tty);
706         add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
707
708         mutex_unlock(&tty->echo_lock);
709 }
710
711 /**
712  *      echo_set_canon_col      -       add operation to set the canon column
713  *      @tty: terminal device
714  *
715  *      Add an operation to the echo buffer to set the canon column
716  *      to the current column.
717  *
718  *      Locking: echo_lock to protect the echo buffer
719  */
720
721 static void echo_set_canon_col(struct tty_struct *tty)
722 {
723         mutex_lock(&tty->echo_lock);
724
725         add_echo_byte(ECHO_OP_START, tty);
726         add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
727
728         mutex_unlock(&tty->echo_lock);
729 }
730
731 /**
732  *      echo_erase_tab  -       add operation to erase a tab
733  *      @num_chars: number of character columns already used
734  *      @after_tab: true if num_chars starts after a previous tab
735  *      @tty: terminal device
736  *
737  *      Add an operation to the echo buffer to erase a tab.
738  *
739  *      Called by the eraser function, which knows how many character
740  *      columns have been used since either a previous tab or the start
741  *      of input.  This information will be used later, along with
742  *      canon column (if applicable), to go back the correct number
743  *      of columns.
744  *
745  *      Locking: echo_lock to protect the echo buffer
746  */
747
748 static void echo_erase_tab(unsigned int num_chars, int after_tab,
749                            struct tty_struct *tty)
750 {
751         mutex_lock(&tty->echo_lock);
752
753         add_echo_byte(ECHO_OP_START, tty);
754         add_echo_byte(ECHO_OP_ERASE_TAB, tty);
755
756         /* We only need to know this modulo 8 (tab spacing) */
757         num_chars &= 7;
758
759         /* Set the high bit as a flag if num_chars is after a previous tab */
760         if (after_tab)
761                 num_chars |= 0x80;
762
763         add_echo_byte(num_chars, tty);
764
765         mutex_unlock(&tty->echo_lock);
766 }
767
768 /**
769  *      echo_char_raw   -       echo a character raw
770  *      @c: unicode byte to echo
771  *      @tty: terminal device
772  *
773  *      Echo user input back onto the screen. This must be called only when
774  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
775  *
776  *      This variant does not treat control characters specially.
777  *
778  *      Locking: echo_lock to protect the echo buffer
779  */
780
781 static void echo_char_raw(unsigned char c, struct tty_struct *tty)
782 {
783         mutex_lock(&tty->echo_lock);
784
785         if (c == ECHO_OP_START) {
786                 add_echo_byte(ECHO_OP_START, tty);
787                 add_echo_byte(ECHO_OP_START, tty);
788         } else {
789                 add_echo_byte(c, tty);
790         }
791
792         mutex_unlock(&tty->echo_lock);
793 }
794
795 /**
796  *      echo_char       -       echo a character
797  *      @c: unicode byte to echo
798  *      @tty: terminal device
799  *
800  *      Echo user input back onto the screen. This must be called only when
801  *      L_ECHO(tty) is true. Called from the driver receive_buf path.
802  *
803  *      This variant tags control characters to be echoed as "^X"
804  *      (where X is the letter representing the control char).
805  *
806  *      Locking: echo_lock to protect the echo buffer
807  */
808
809 static void echo_char(unsigned char c, struct tty_struct *tty)
810 {
811         mutex_lock(&tty->echo_lock);
812
813         if (c == ECHO_OP_START) {
814                 add_echo_byte(ECHO_OP_START, tty);
815                 add_echo_byte(ECHO_OP_START, tty);
816         } else {
817                 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
818                         add_echo_byte(ECHO_OP_START, tty);
819                 add_echo_byte(c, tty);
820         }
821
822         mutex_unlock(&tty->echo_lock);
823 }
824
825 /**
826  *      finish_erasing          -       complete erase
827  *      @tty: tty doing the erase
828  */
829
830 static inline void finish_erasing(struct tty_struct *tty)
831 {
832         if (tty->erasing) {
833                 echo_char_raw('/', tty);
834                 tty->erasing = 0;
835         }
836 }
837
838 /**
839  *      eraser          -       handle erase function
840  *      @c: character input
841  *      @tty: terminal device
842  *
843  *      Perform erase and necessary output when an erase character is
844  *      present in the stream from the driver layer. Handles the complexities
845  *      of UTF-8 multibyte symbols.
846  *
847  *      Locking: read_lock for tty buffers
848  */
849
850 static void eraser(unsigned char c, struct tty_struct *tty)
851 {
852         enum { ERASE, WERASE, KILL } kill_type;
853         int head, seen_alnums, cnt;
854         unsigned long flags;
855
856         /* FIXME: locking needed ? */
857         if (tty->read_head == tty->canon_head) {
858                 /* process_output('\a', tty); */ /* what do you think? */
859                 return;
860         }
861         if (c == ERASE_CHAR(tty))
862                 kill_type = ERASE;
863         else if (c == WERASE_CHAR(tty))
864                 kill_type = WERASE;
865         else {
866                 if (!L_ECHO(tty)) {
867                         spin_lock_irqsave(&tty->read_lock, flags);
868                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
869                                           (N_TTY_BUF_SIZE - 1));
870                         tty->read_head = tty->canon_head;
871                         spin_unlock_irqrestore(&tty->read_lock, flags);
872                         return;
873                 }
874                 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
875                         spin_lock_irqsave(&tty->read_lock, flags);
876                         tty->read_cnt -= ((tty->read_head - tty->canon_head) &
877                                           (N_TTY_BUF_SIZE - 1));
878                         tty->read_head = tty->canon_head;
879                         spin_unlock_irqrestore(&tty->read_lock, flags);
880                         finish_erasing(tty);
881                         echo_char(KILL_CHAR(tty), tty);
882                         /* Add a newline if ECHOK is on and ECHOKE is off. */
883                         if (L_ECHOK(tty))
884                                 echo_char_raw('\n', tty);
885                         return;
886                 }
887                 kill_type = KILL;
888         }
889
890         seen_alnums = 0;
891         /* FIXME: Locking ?? */
892         while (tty->read_head != tty->canon_head) {
893                 head = tty->read_head;
894
895                 /* erase a single possibly multibyte character */
896                 do {
897                         head = (head - 1) & (N_TTY_BUF_SIZE-1);
898                         c = tty->read_buf[head];
899                 } while (is_continuation(c, tty) && head != tty->canon_head);
900
901                 /* do not partially erase */
902                 if (is_continuation(c, tty))
903                         break;
904
905                 if (kill_type == WERASE) {
906                         /* Equivalent to BSD's ALTWERASE. */
907                         if (isalnum(c) || c == '_')
908                                 seen_alnums++;
909                         else if (seen_alnums)
910                                 break;
911                 }
912                 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
913                 spin_lock_irqsave(&tty->read_lock, flags);
914                 tty->read_head = head;
915                 tty->read_cnt -= cnt;
916                 spin_unlock_irqrestore(&tty->read_lock, flags);
917                 if (L_ECHO(tty)) {
918                         if (L_ECHOPRT(tty)) {
919                                 if (!tty->erasing) {
920                                         echo_char_raw('\\', tty);
921                                         tty->erasing = 1;
922                                 }
923                                 /* if cnt > 1, output a multi-byte character */
924                                 echo_char(c, tty);
925                                 while (--cnt > 0) {
926                                         head = (head+1) & (N_TTY_BUF_SIZE-1);
927                                         echo_char_raw(tty->read_buf[head], tty);
928                                         echo_move_back_col(tty);
929                                 }
930                         } else if (kill_type == ERASE && !L_ECHOE(tty)) {
931                                 echo_char(ERASE_CHAR(tty), tty);
932                         } else if (c == '\t') {
933                                 unsigned int num_chars = 0;
934                                 int after_tab = 0;
935                                 unsigned long tail = tty->read_head;
936
937                                 /*
938                                  * Count the columns used for characters
939                                  * since the start of input or after a
940                                  * previous tab.
941                                  * This info is used to go back the correct
942                                  * number of columns.
943                                  */
944                                 while (tail != tty->canon_head) {
945                                         tail = (tail-1) & (N_TTY_BUF_SIZE-1);
946                                         c = tty->read_buf[tail];
947                                         if (c == '\t') {
948                                                 after_tab = 1;
949                                                 break;
950                                         } else if (iscntrl(c)) {
951                                                 if (L_ECHOCTL(tty))
952                                                         num_chars += 2;
953                                         } else if (!is_continuation(c, tty)) {
954                                                 num_chars++;
955                                         }
956                                 }
957                                 echo_erase_tab(num_chars, after_tab, tty);
958                         } else {
959                                 if (iscntrl(c) && L_ECHOCTL(tty)) {
960                                         echo_char_raw('\b', tty);
961                                         echo_char_raw(' ', tty);
962                                         echo_char_raw('\b', tty);
963                                 }
964                                 if (!iscntrl(c) || L_ECHOCTL(tty)) {
965                                         echo_char_raw('\b', tty);
966                                         echo_char_raw(' ', tty);
967                                         echo_char_raw('\b', tty);
968                                 }
969                         }
970                 }
971                 if (kill_type == ERASE)
972                         break;
973         }
974         if (tty->read_head == tty->canon_head && L_ECHO(tty))
975                 finish_erasing(tty);
976 }
977
978 /**
979  *      isig            -       handle the ISIG optio
980  *      @sig: signal
981  *      @tty: terminal
982  *      @flush: force flush
983  *
984  *      Called when a signal is being sent due to terminal input. This
985  *      may caus terminal flushing to take place according to the termios
986  *      settings and character used. Called from the driver receive_buf
987  *      path so serialized.
988  *
989  *      Locking: ctrl_lock, read_lock (both via flush buffer)
990  */
991
992 static inline void isig(int sig, struct tty_struct *tty, int flush)
993 {
994         if (tty->pgrp)
995                 kill_pgrp(tty->pgrp, sig, 1);
996         if (flush || !L_NOFLSH(tty)) {
997                 n_tty_flush_buffer(tty);
998                 tty_driver_flush_buffer(tty);
999         }
1000 }
1001
1002 /**
1003  *      n_tty_receive_break     -       handle break
1004  *      @tty: terminal
1005  *
1006  *      An RS232 break event has been hit in the incoming bitstream. This
1007  *      can cause a variety of events depending upon the termios settings.
1008  *
1009  *      Called from the receive_buf path so single threaded.
1010  */
1011
1012 static inline void n_tty_receive_break(struct tty_struct *tty)
1013 {
1014         if (I_IGNBRK(tty))
1015                 return;
1016         if (I_BRKINT(tty)) {
1017                 isig(SIGINT, tty, 1);
1018                 return;
1019         }
1020         if (I_PARMRK(tty)) {
1021                 put_tty_queue('\377', tty);
1022                 put_tty_queue('\0', tty);
1023         }
1024         put_tty_queue('\0', tty);
1025         wake_up_interruptible(&tty->read_wait);
1026 }
1027
1028 /**
1029  *      n_tty_receive_overrun   -       handle overrun reporting
1030  *      @tty: terminal
1031  *
1032  *      Data arrived faster than we could process it. While the tty
1033  *      driver has flagged this the bits that were missed are gone
1034  *      forever.
1035  *
1036  *      Called from the receive_buf path so single threaded. Does not
1037  *      need locking as num_overrun and overrun_time are function
1038  *      private.
1039  */
1040
1041 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1042 {
1043         char buf[64];
1044
1045         tty->num_overrun++;
1046         if (time_before(tty->overrun_time, jiffies - HZ) ||
1047                         time_after(tty->overrun_time, jiffies)) {
1048                 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1049                         tty_name(tty, buf),
1050                         tty->num_overrun);
1051                 tty->overrun_time = jiffies;
1052                 tty->num_overrun = 0;
1053         }
1054 }
1055
1056 /**
1057  *      n_tty_receive_parity_error      -       error notifier
1058  *      @tty: terminal device
1059  *      @c: character
1060  *
1061  *      Process a parity error and queue the right data to indicate
1062  *      the error case if necessary. Locking as per n_tty_receive_buf.
1063  */
1064 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1065                                               unsigned char c)
1066 {
1067         if (I_IGNPAR(tty))
1068                 return;
1069         if (I_PARMRK(tty)) {
1070                 put_tty_queue('\377', tty);
1071                 put_tty_queue('\0', tty);
1072                 put_tty_queue(c, tty);
1073         } else  if (I_INPCK(tty))
1074                 put_tty_queue('\0', tty);
1075         else
1076                 put_tty_queue(c, tty);
1077         wake_up_interruptible(&tty->read_wait);
1078 }
1079
1080 /**
1081  *      n_tty_receive_char      -       perform processing
1082  *      @tty: terminal device
1083  *      @c: character
1084  *
1085  *      Process an individual character of input received from the driver.
1086  *      This is serialized with respect to itself by the rules for the
1087  *      driver above.
1088  */
1089
1090 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1091 {
1092         unsigned long flags;
1093         int parmrk;
1094
1095         if (tty->raw) {
1096                 put_tty_queue(c, tty);
1097                 return;
1098         }
1099
1100         if (I_ISTRIP(tty))
1101                 c &= 0x7f;
1102         if (I_IUCLC(tty) && L_IEXTEN(tty))
1103                 c = tolower(c);
1104
1105         if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1106             I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1107             c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1108                 start_tty(tty);
1109                 process_echoes(tty);
1110         }
1111
1112         if (tty->closing) {
1113                 if (I_IXON(tty)) {
1114                         if (c == START_CHAR(tty)) {
1115                                 start_tty(tty);
1116                                 process_echoes(tty);
1117                         } else if (c == STOP_CHAR(tty))
1118                                 stop_tty(tty);
1119                 }
1120                 return;
1121         }
1122
1123         /*
1124          * If the previous character was LNEXT, or we know that this
1125          * character is not one of the characters that we'll have to
1126          * handle specially, do shortcut processing to speed things
1127          * up.
1128          */
1129         if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1130                 tty->lnext = 0;
1131                 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1132                 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1133                         /* beep if no space */
1134                         if (L_ECHO(tty))
1135                                 process_output('\a', tty);
1136                         return;
1137                 }
1138                 if (L_ECHO(tty)) {
1139                         finish_erasing(tty);
1140                         /* Record the column of first canon char. */
1141                         if (tty->canon_head == tty->read_head)
1142                                 echo_set_canon_col(tty);
1143                         echo_char(c, tty);
1144                         process_echoes(tty);
1145                 }
1146                 if (parmrk)
1147                         put_tty_queue(c, tty);
1148                 put_tty_queue(c, tty);
1149                 return;
1150         }
1151
1152         if (I_IXON(tty)) {
1153                 if (c == START_CHAR(tty)) {
1154                         start_tty(tty);
1155                         process_echoes(tty);
1156                         return;
1157                 }
1158                 if (c == STOP_CHAR(tty)) {
1159                         stop_tty(tty);
1160                         return;
1161                 }
1162         }
1163
1164         if (L_ISIG(tty)) {
1165                 int signal;
1166                 signal = SIGINT;
1167                 if (c == INTR_CHAR(tty))
1168                         goto send_signal;
1169                 signal = SIGQUIT;
1170                 if (c == QUIT_CHAR(tty))
1171                         goto send_signal;
1172                 signal = SIGTSTP;
1173                 if (c == SUSP_CHAR(tty)) {
1174 send_signal:
1175                         /*
1176                          * Note that we do not use isig() here because we want
1177                          * the order to be:
1178                          * 1) flush, 2) echo, 3) signal
1179                          */
1180                         if (!L_NOFLSH(tty)) {
1181                                 n_tty_flush_buffer(tty);
1182                                 tty_driver_flush_buffer(tty);
1183                         }
1184                         if (I_IXON(tty))
1185                                 start_tty(tty);
1186                         if (L_ECHO(tty)) {
1187                                 echo_char(c, tty);
1188                                 process_echoes(tty);
1189                         }
1190                         if (tty->pgrp)
1191                                 kill_pgrp(tty->pgrp, signal, 1);
1192                         return;
1193                 }
1194         }
1195
1196         if (c == '\r') {
1197                 if (I_IGNCR(tty))
1198                         return;
1199                 if (I_ICRNL(tty))
1200                         c = '\n';
1201         } else if (c == '\n' && I_INLCR(tty))
1202                 c = '\r';
1203
1204         if (tty->icanon) {
1205                 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1206                     (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1207                         eraser(c, tty);
1208                         process_echoes(tty);
1209                         return;
1210                 }
1211                 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1212                         tty->lnext = 1;
1213                         if (L_ECHO(tty)) {
1214                                 finish_erasing(tty);
1215                                 if (L_ECHOCTL(tty)) {
1216                                         echo_char_raw('^', tty);
1217                                         echo_char_raw('\b', tty);
1218                                         process_echoes(tty);
1219                                 }
1220                         }
1221                         return;
1222                 }
1223                 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1224                     L_IEXTEN(tty)) {
1225                         unsigned long tail = tty->canon_head;
1226
1227                         finish_erasing(tty);
1228                         echo_char(c, tty);
1229                         echo_char_raw('\n', tty);
1230                         while (tail != tty->read_head) {
1231                                 echo_char(tty->read_buf[tail], tty);
1232                                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1233                         }
1234                         process_echoes(tty);
1235                         return;
1236                 }
1237                 if (c == '\n') {
1238                         if (tty->read_cnt >= N_TTY_BUF_SIZE) {
1239                                 if (L_ECHO(tty))
1240                                         process_output('\a', tty);
1241                                 return;
1242                         }
1243                         if (L_ECHO(tty) || L_ECHONL(tty)) {
1244                                 echo_char_raw('\n', tty);
1245                                 process_echoes(tty);
1246                         }
1247                         goto handle_newline;
1248                 }
1249                 if (c == EOF_CHAR(tty)) {
1250                         if (tty->read_cnt >= N_TTY_BUF_SIZE)
1251                                 return;
1252                         if (tty->canon_head != tty->read_head)
1253                                 set_bit(TTY_PUSH, &tty->flags);
1254                         c = __DISABLED_CHAR;
1255                         goto handle_newline;
1256                 }
1257                 if ((c == EOL_CHAR(tty)) ||
1258                     (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1259                         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1260                                  ? 1 : 0;
1261                         if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1262                                 if (L_ECHO(tty))
1263                                         process_output('\a', tty);
1264                                 return;
1265                         }
1266                         /*
1267                          * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1268                          */
1269                         if (L_ECHO(tty)) {
1270                                 /* Record the column of first canon char. */
1271                                 if (tty->canon_head == tty->read_head)
1272                                         echo_set_canon_col(tty);
1273                                 echo_char(c, tty);
1274                                 process_echoes(tty);
1275                         }
1276                         /*
1277                          * XXX does PARMRK doubling happen for
1278                          * EOL_CHAR and EOL2_CHAR?
1279                          */
1280                         if (parmrk)
1281                                 put_tty_queue(c, tty);
1282
1283 handle_newline:
1284                         spin_lock_irqsave(&tty->read_lock, flags);
1285                         set_bit(tty->read_head, tty->read_flags);
1286                         put_tty_queue_nolock(c, tty);
1287                         tty->canon_head = tty->read_head;
1288                         tty->canon_data++;
1289                         spin_unlock_irqrestore(&tty->read_lock, flags);
1290                         kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1291                         if (waitqueue_active(&tty->read_wait))
1292                                 wake_up_interruptible(&tty->read_wait);
1293                         return;
1294                 }
1295         }
1296
1297         parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1298         if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1299                 /* beep if no space */
1300                 if (L_ECHO(tty))
1301                         process_output('\a', tty);
1302                 return;
1303         }
1304         if (L_ECHO(tty)) {
1305                 finish_erasing(tty);
1306                 if (c == '\n')
1307                         echo_char_raw('\n', tty);
1308                 else {
1309                         /* Record the column of first canon char. */
1310                         if (tty->canon_head == tty->read_head)
1311                                 echo_set_canon_col(tty);
1312                         echo_char(c, tty);
1313                 }
1314                 process_echoes(tty);
1315         }
1316
1317         if (parmrk)
1318                 put_tty_queue(c, tty);
1319
1320         put_tty_queue(c, tty);
1321 }
1322
1323
1324 /**
1325  *      n_tty_write_wakeup      -       asynchronous I/O notifier
1326  *      @tty: tty device
1327  *
1328  *      Required for the ptys, serial driver etc. since processes
1329  *      that attach themselves to the master and rely on ASYNC
1330  *      IO must be woken up
1331  */
1332
1333 static void n_tty_write_wakeup(struct tty_struct *tty)
1334 {
1335         if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1336                 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1337 }
1338
1339 /**
1340  *      n_tty_receive_buf       -       data receive
1341  *      @tty: terminal device
1342  *      @cp: buffer
1343  *      @fp: flag buffer
1344  *      @count: characters
1345  *
1346  *      Called by the terminal driver when a block of characters has
1347  *      been received. This function must be called from soft contexts
1348  *      not from interrupt context. The driver is responsible for making
1349  *      calls one at a time and in order (or using flush_to_ldisc)
1350  */
1351
1352 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1353                               char *fp, int count)
1354 {
1355         const unsigned char *p;
1356         char *f, flags = TTY_NORMAL;
1357         int     i;
1358         char    buf[64];
1359         unsigned long cpuflags;
1360
1361         if (!tty->read_buf)
1362                 return;
1363
1364         if (tty->real_raw) {
1365                 spin_lock_irqsave(&tty->read_lock, cpuflags);
1366                 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1367                         N_TTY_BUF_SIZE - tty->read_head);
1368                 i = min(count, i);
1369                 memcpy(tty->read_buf + tty->read_head, cp, i);
1370                 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1371                 tty->read_cnt += i;
1372                 cp += i;
1373                 count -= i;
1374
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                 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1382         } else {
1383                 for (i = count, p = cp, f = fp; i; i--, p++) {
1384                         if (f)
1385                                 flags = *f++;
1386                         switch (flags) {
1387                         case TTY_NORMAL:
1388                                 n_tty_receive_char(tty, *p);
1389                                 break;
1390                         case TTY_BREAK:
1391                                 n_tty_receive_break(tty);
1392                                 break;
1393                         case TTY_PARITY:
1394                         case TTY_FRAME:
1395                                 n_tty_receive_parity_error(tty, *p);
1396                                 break;
1397                         case TTY_OVERRUN:
1398                                 n_tty_receive_overrun(tty);
1399                                 break;
1400                         default:
1401                                 printk(KERN_ERR "%s: unknown flag %d\n",
1402                                        tty_name(tty, buf), flags);
1403                                 break;
1404                         }
1405                 }
1406                 if (tty->ops->flush_chars)
1407                         tty->ops->flush_chars(tty);
1408         }
1409
1410         n_tty_set_room(tty);
1411
1412         if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
1413                 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1414                 if (waitqueue_active(&tty->read_wait))
1415                         wake_up_interruptible(&tty->read_wait);
1416         }
1417
1418         /*
1419          * Check the remaining room for the input canonicalization
1420          * mode.  We don't want to throttle the driver if we're in
1421          * canonical mode and don't have a newline yet!
1422          */
1423         if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1424                 tty_throttle(tty);
1425 }
1426
1427 int is_ignored(int sig)
1428 {
1429         return (sigismember(&current->blocked, sig) ||
1430                 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1431 }
1432
1433 /**
1434  *      n_tty_set_termios       -       termios data changed
1435  *      @tty: terminal
1436  *      @old: previous data
1437  *
1438  *      Called by the tty layer when the user changes termios flags so
1439  *      that the line discipline can plan ahead. This function cannot sleep
1440  *      and is protected from re-entry by the tty layer. The user is
1441  *      guaranteed that this function will not be re-entered or in progress
1442  *      when the ldisc is closed.
1443  *
1444  *      Locking: Caller holds tty->termios_mutex
1445  */
1446
1447 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1448 {
1449         int canon_change = 1;
1450         BUG_ON(!tty);
1451
1452         if (old)
1453                 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1454         if (canon_change) {
1455                 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1456                 tty->canon_head = tty->read_tail;
1457                 tty->canon_data = 0;
1458                 tty->erasing = 0;
1459         }
1460
1461         if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1462                 wake_up_interruptible(&tty->read_wait);
1463
1464         tty->icanon = (L_ICANON(tty) != 0);
1465         if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1466                 tty->raw = 1;
1467                 tty->real_raw = 1;
1468                 n_tty_set_room(tty);
1469                 return;
1470         }
1471         if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1472             I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1473             I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1474             I_PARMRK(tty)) {
1475                 memset(tty->process_char_map, 0, 256/8);
1476
1477                 if (I_IGNCR(tty) || I_ICRNL(tty))
1478                         set_bit('\r', tty->process_char_map);
1479                 if (I_INLCR(tty))
1480                         set_bit('\n', tty->process_char_map);
1481
1482                 if (L_ICANON(tty)) {
1483                         set_bit(ERASE_CHAR(tty), tty->process_char_map);
1484                         set_bit(KILL_CHAR(tty), tty->process_char_map);
1485                         set_bit(EOF_CHAR(tty), tty->process_char_map);
1486                         set_bit('\n', tty->process_char_map);
1487                         set_bit(EOL_CHAR(tty), tty->process_char_map);
1488                         if (L_IEXTEN(tty)) {
1489                                 set_bit(WERASE_CHAR(tty),
1490                                         tty->process_char_map);
1491                                 set_bit(LNEXT_CHAR(tty),
1492                                         tty->process_char_map);
1493                                 set_bit(EOL2_CHAR(tty),
1494                                         tty->process_char_map);
1495                                 if (L_ECHO(tty))
1496                                         set_bit(REPRINT_CHAR(tty),
1497                                                 tty->process_char_map);
1498                         }
1499                 }
1500                 if (I_IXON(tty)) {
1501                         set_bit(START_CHAR(tty), tty->process_char_map);
1502                         set_bit(STOP_CHAR(tty), tty->process_char_map);
1503                 }
1504                 if (L_ISIG(tty)) {
1505                         set_bit(INTR_CHAR(tty), tty->process_char_map);
1506                         set_bit(QUIT_CHAR(tty), tty->process_char_map);
1507                         set_bit(SUSP_CHAR(tty), tty->process_char_map);
1508                 }
1509                 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1510                 tty->raw = 0;
1511                 tty->real_raw = 0;
1512         } else {
1513                 tty->raw = 1;
1514                 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1515                     (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1516                     (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1517                         tty->real_raw = 1;
1518                 else
1519                         tty->real_raw = 0;
1520         }
1521         n_tty_set_room(tty);
1522         /* The termios change make the tty ready for I/O */
1523         wake_up_interruptible(&tty->write_wait);
1524         wake_up_interruptible(&tty->read_wait);
1525 }
1526
1527 /**
1528  *      n_tty_close             -       close the ldisc for this tty
1529  *      @tty: device
1530  *
1531  *      Called from the terminal layer when this line discipline is
1532  *      being shut down, either because of a close or becsuse of a
1533  *      discipline change. The function will not be called while other
1534  *      ldisc methods are in progress.
1535  */
1536
1537 static void n_tty_close(struct tty_struct *tty)
1538 {
1539         n_tty_flush_buffer(tty);
1540         if (tty->read_buf) {
1541                 kfree(tty->read_buf);
1542                 tty->read_buf = NULL;
1543         }
1544         if (tty->echo_buf) {
1545                 kfree(tty->echo_buf);
1546                 tty->echo_buf = NULL;
1547         }
1548 }
1549
1550 /**
1551  *      n_tty_open              -       open an ldisc
1552  *      @tty: terminal to open
1553  *
1554  *      Called when this line discipline is being attached to the
1555  *      terminal device. Can sleep. Called serialized so that no
1556  *      other events will occur in parallel. No further open will occur
1557  *      until a close.
1558  */
1559
1560 static int n_tty_open(struct tty_struct *tty)
1561 {
1562         if (!tty)
1563                 return -EINVAL;
1564
1565         /* These are ugly. Currently a malloc failure here can panic */
1566         if (!tty->read_buf) {
1567                 tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1568                 if (!tty->read_buf)
1569                         return -ENOMEM;
1570         }
1571         if (!tty->echo_buf) {
1572                 tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1573
1574                 if (!tty->echo_buf)
1575                         return -ENOMEM;
1576         }
1577         reset_buffer_flags(tty);
1578         tty->column = 0;
1579         n_tty_set_termios(tty, NULL);
1580         tty->minimum_to_wake = 1;
1581         tty->closing = 0;
1582         return 0;
1583 }
1584
1585 static inline int input_available_p(struct tty_struct *tty, int amt)
1586 {
1587         tty_flush_to_ldisc(tty);
1588         if (tty->icanon) {
1589                 if (tty->canon_data)
1590                         return 1;
1591         } else if (tty->read_cnt >= (amt ? amt : 1))
1592                 return 1;
1593
1594         return 0;
1595 }
1596
1597 /**
1598  *      copy_from_read_buf      -       copy read data directly
1599  *      @tty: terminal device
1600  *      @b: user data
1601  *      @nr: size of data
1602  *
1603  *      Helper function to speed up n_tty_read.  It is only called when
1604  *      ICANON is off; it copies characters straight from the tty queue to
1605  *      user space directly.  It can be profitably called twice; once to
1606  *      drain the space from the tail pointer to the (physical) end of the
1607  *      buffer, and once to drain the space from the (physical) beginning of
1608  *      the buffer to head pointer.
1609  *
1610  *      Called under the tty->atomic_read_lock sem
1611  *
1612  */
1613
1614 static int copy_from_read_buf(struct tty_struct *tty,
1615                                       unsigned char __user **b,
1616                                       size_t *nr)
1617
1618 {
1619         int retval;
1620         size_t n;
1621         unsigned long flags;
1622
1623         retval = 0;
1624         spin_lock_irqsave(&tty->read_lock, flags);
1625         n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1626         n = min(*nr, n);
1627         spin_unlock_irqrestore(&tty->read_lock, flags);
1628         if (n) {
1629                 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1630                 n -= retval;
1631                 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1632                 spin_lock_irqsave(&tty->read_lock, flags);
1633                 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1634                 tty->read_cnt -= n;
1635                 spin_unlock_irqrestore(&tty->read_lock, flags);
1636                 *b += n;
1637                 *nr -= n;
1638         }
1639         return retval;
1640 }
1641
1642 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1643                                                         size_t, loff_t *);
1644
1645 /**
1646  *      job_control             -       check job control
1647  *      @tty: tty
1648  *      @file: file handle
1649  *
1650  *      Perform job control management checks on this file/tty descriptor
1651  *      and if appropriate send any needed signals and return a negative
1652  *      error code if action should be taken.
1653  *
1654  *      FIXME:
1655  *      Locking: None - redirected write test is safe, testing
1656  *      current->signal should possibly lock current->sighand
1657  *      pgrp locking ?
1658  */
1659
1660 static int job_control(struct tty_struct *tty, struct file *file)
1661 {
1662         /* Job control check -- must be done at start and after
1663            every sleep (POSIX.1 7.1.1.4). */
1664         /* NOTE: not yet done after every sleep pending a thorough
1665            check of the logic of this change. -- jlc */
1666         /* don't stop on /dev/console */
1667         if (file->f_op->write != redirected_tty_write &&
1668             current->signal->tty == tty) {
1669                 if (!tty->pgrp)
1670                         printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1671                 else if (task_pgrp(current) != tty->pgrp) {
1672                         if (is_ignored(SIGTTIN) ||
1673                             is_current_pgrp_orphaned())
1674                                 return -EIO;
1675                         kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1676                         set_thread_flag(TIF_SIGPENDING);
1677                         return -ERESTARTSYS;
1678                 }
1679         }
1680         return 0;
1681 }
1682
1683
1684 /**
1685  *      n_tty_read              -       read function for tty
1686  *      @tty: tty device
1687  *      @file: file object
1688  *      @buf: userspace buffer pointer
1689  *      @nr: size of I/O
1690  *
1691  *      Perform reads for the line discipline. We are guaranteed that the
1692  *      line discipline will not be closed under us but we may get multiple
1693  *      parallel readers and must handle this ourselves. We may also get
1694  *      a hangup. Always called in user context, may sleep.
1695  *
1696  *      This code must be sure never to sleep through a hangup.
1697  */
1698
1699 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1700                          unsigned char __user *buf, size_t nr)
1701 {
1702         unsigned char __user *b = buf;
1703         DECLARE_WAITQUEUE(wait, current);
1704         int c;
1705         int minimum, time;
1706         ssize_t retval = 0;
1707         ssize_t size;
1708         long timeout;
1709         unsigned long flags;
1710         int packet;
1711
1712 do_it_again:
1713
1714         BUG_ON(!tty->read_buf);
1715
1716         c = job_control(tty, file);
1717         if (c < 0)
1718                 return c;
1719
1720         minimum = time = 0;
1721         timeout = MAX_SCHEDULE_TIMEOUT;
1722         if (!tty->icanon) {
1723                 time = (HZ / 10) * TIME_CHAR(tty);
1724                 minimum = MIN_CHAR(tty);
1725                 if (minimum) {
1726                         if (time)
1727                                 tty->minimum_to_wake = 1;
1728                         else if (!waitqueue_active(&tty->read_wait) ||
1729                                  (tty->minimum_to_wake > minimum))
1730                                 tty->minimum_to_wake = minimum;
1731                 } else {
1732                         timeout = 0;
1733                         if (time) {
1734                                 timeout = time;
1735                                 time = 0;
1736                         }
1737                         tty->minimum_to_wake = minimum = 1;
1738                 }
1739         }
1740
1741         /*
1742          *      Internal serialization of reads.
1743          */
1744         if (file->f_flags & O_NONBLOCK) {
1745                 if (!mutex_trylock(&tty->atomic_read_lock))
1746                         return -EAGAIN;
1747         } else {
1748                 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1749                         return -ERESTARTSYS;
1750         }
1751         packet = tty->packet;
1752
1753         add_wait_queue(&tty->read_wait, &wait);
1754         while (nr) {
1755                 /* First test for status change. */
1756                 if (packet && tty->link->ctrl_status) {
1757                         unsigned char cs;
1758                         if (b != buf)
1759                                 break;
1760                         spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1761                         cs = tty->link->ctrl_status;
1762                         tty->link->ctrl_status = 0;
1763                         spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1764                         if (tty_put_user(tty, cs, b++)) {
1765                                 retval = -EFAULT;
1766                                 b--;
1767                                 break;
1768                         }
1769                         nr--;
1770                         break;
1771                 }
1772                 /* This statement must be first before checking for input
1773                    so that any interrupt will set the state back to
1774                    TASK_RUNNING. */
1775                 set_current_state(TASK_INTERRUPTIBLE);
1776
1777                 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1778                     ((minimum - (b - buf)) >= 1))
1779                         tty->minimum_to_wake = (minimum - (b - buf));
1780
1781                 if (!input_available_p(tty, 0)) {
1782                         if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1783                                 retval = -EIO;
1784                                 break;
1785                         }
1786                         if (tty_hung_up_p(file))
1787                                 break;
1788                         if (!timeout)
1789                                 break;
1790                         if (file->f_flags & O_NONBLOCK) {
1791                                 retval = -EAGAIN;
1792                                 break;
1793                         }
1794                         if (signal_pending(current)) {
1795                                 retval = -ERESTARTSYS;
1796                                 break;
1797                         }
1798                         /* FIXME: does n_tty_set_room need locking ? */
1799                         n_tty_set_room(tty);
1800                         timeout = schedule_timeout(timeout);
1801                         continue;
1802                 }
1803                 __set_current_state(TASK_RUNNING);
1804
1805                 /* Deal with packet mode. */
1806                 if (packet && b == buf) {
1807                         if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1808                                 retval = -EFAULT;
1809                                 b--;
1810                                 break;
1811                         }
1812                         nr--;
1813                 }
1814
1815                 if (tty->icanon) {
1816                         /* N.B. avoid overrun if nr == 0 */
1817                         while (nr && tty->read_cnt) {
1818                                 int eol;
1819
1820                                 eol = test_and_clear_bit(tty->read_tail,
1821                                                 tty->read_flags);
1822                                 c = tty->read_buf[tty->read_tail];
1823                                 spin_lock_irqsave(&tty->read_lock, flags);
1824                                 tty->read_tail = ((tty->read_tail+1) &
1825                                                   (N_TTY_BUF_SIZE-1));
1826                                 tty->read_cnt--;
1827                                 if (eol) {
1828                                         /* this test should be redundant:
1829                                          * we shouldn't be reading data if
1830                                          * canon_data is 0
1831                                          */
1832                                         if (--tty->canon_data < 0)
1833                                                 tty->canon_data = 0;
1834                                 }
1835                                 spin_unlock_irqrestore(&tty->read_lock, flags);
1836
1837                                 if (!eol || (c != __DISABLED_CHAR)) {
1838                                         if (tty_put_user(tty, c, b++)) {
1839                                                 retval = -EFAULT;
1840                                                 b--;
1841                                                 break;
1842                                         }
1843                                         nr--;
1844                                 }
1845                                 if (eol) {
1846                                         tty_audit_push(tty);
1847                                         break;
1848                                 }
1849                         }
1850                         if (retval)
1851                                 break;
1852                 } else {
1853                         int uncopied;
1854                         /* The copy function takes the read lock and handles
1855                            locking internally for this case */
1856                         uncopied = copy_from_read_buf(tty, &b, &nr);
1857                         uncopied += copy_from_read_buf(tty, &b, &nr);
1858                         if (uncopied) {
1859                                 retval = -EFAULT;
1860                                 break;
1861                         }
1862                 }
1863
1864                 /* If there is enough space in the read buffer now, let the
1865                  * low-level driver know. We use n_tty_chars_in_buffer() to
1866                  * check the buffer, as it now knows about canonical mode.
1867                  * Otherwise, if the driver is throttled and the line is
1868                  * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1869                  * we won't get any more characters.
1870                  */
1871                 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1872                         n_tty_set_room(tty);
1873                         check_unthrottle(tty);
1874                 }
1875
1876                 if (b - buf >= minimum)
1877                         break;
1878                 if (time)
1879                         timeout = time;
1880         }
1881         mutex_unlock(&tty->atomic_read_lock);
1882         remove_wait_queue(&tty->read_wait, &wait);
1883
1884         if (!waitqueue_active(&tty->read_wait))
1885                 tty->minimum_to_wake = minimum;
1886
1887         __set_current_state(TASK_RUNNING);
1888         size = b - buf;
1889         if (size) {
1890                 retval = size;
1891                 if (nr)
1892                         clear_bit(TTY_PUSH, &tty->flags);
1893         } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1894                  goto do_it_again;
1895
1896         n_tty_set_room(tty);
1897         return retval;
1898 }
1899
1900 /**
1901  *      n_tty_write             -       write function for tty
1902  *      @tty: tty device
1903  *      @file: file object
1904  *      @buf: userspace buffer pointer
1905  *      @nr: size of I/O
1906  *
1907  *      Write function of the terminal device.  This is serialized with
1908  *      respect to other write callers but not to termios changes, reads
1909  *      and other such events.  Since the receive code will echo characters,
1910  *      thus calling driver write methods, the output_lock is used in
1911  *      the output processing functions called here as well as in the
1912  *      echo processing function to protect the column state and space
1913  *      left in the buffer.
1914  *
1915  *      This code must be sure never to sleep through a hangup.
1916  *
1917  *      Locking: output_lock to protect column state and space left
1918  *               (note that the process_output*() functions take this
1919  *                lock themselves)
1920  */
1921
1922 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1923                            const unsigned char *buf, size_t nr)
1924 {
1925         const unsigned char *b = buf;
1926         DECLARE_WAITQUEUE(wait, current);
1927         int c;
1928         ssize_t retval = 0;
1929
1930         /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1931         if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1932                 retval = tty_check_change(tty);
1933                 if (retval)
1934                         return retval;
1935         }
1936
1937         /* Write out any echoed characters that are still pending */
1938         process_echoes(tty);
1939
1940         add_wait_queue(&tty->write_wait, &wait);
1941         while (1) {
1942                 set_current_state(TASK_INTERRUPTIBLE);
1943                 if (signal_pending(current)) {
1944                         retval = -ERESTARTSYS;
1945                         break;
1946                 }
1947                 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1948                         retval = -EIO;
1949                         break;
1950                 }
1951                 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1952                         while (nr > 0) {
1953                                 ssize_t num = process_output_block(tty, b, nr);
1954                                 if (num < 0) {
1955                                         if (num == -EAGAIN)
1956                                                 break;
1957                                         retval = num;
1958                                         goto break_out;
1959                                 }
1960                                 b += num;
1961                                 nr -= num;
1962                                 if (nr == 0)
1963                                         break;
1964                                 c = *b;
1965                                 if (process_output(c, tty) < 0)
1966                                         break;
1967                                 b++; nr--;
1968                         }
1969                         if (tty->ops->flush_chars)
1970                                 tty->ops->flush_chars(tty);
1971                 } else {
1972                         while (nr > 0) {
1973                                 c = tty->ops->write(tty, b, nr);
1974                                 if (c < 0) {
1975                                         retval = c;
1976                                         goto break_out;
1977                                 }
1978                                 if (!c)
1979                                         break;
1980                                 b += c;
1981                                 nr -= c;
1982                         }
1983                 }
1984                 if (!nr)
1985                         break;
1986                 if (file->f_flags & O_NONBLOCK) {
1987                         retval = -EAGAIN;
1988                         break;
1989                 }
1990                 schedule();
1991         }
1992 break_out:
1993         __set_current_state(TASK_RUNNING);
1994         remove_wait_queue(&tty->write_wait, &wait);
1995         if (b - buf != nr && tty->fasync)
1996                 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
1997         return (b - buf) ? b - buf : retval;
1998 }
1999
2000 /**
2001  *      n_tty_poll              -       poll method for N_TTY
2002  *      @tty: terminal device
2003  *      @file: file accessing it
2004  *      @wait: poll table
2005  *
2006  *      Called when the line discipline is asked to poll() for data or
2007  *      for special events. This code is not serialized with respect to
2008  *      other events save open/close.
2009  *
2010  *      This code must be sure never to sleep through a hangup.
2011  *      Called without the kernel lock held - fine
2012  */
2013
2014 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2015                                                         poll_table *wait)
2016 {
2017         unsigned int mask = 0;
2018
2019         poll_wait(file, &tty->read_wait, wait);
2020         poll_wait(file, &tty->write_wait, wait);
2021         if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2022                 mask |= POLLIN | POLLRDNORM;
2023         if (tty->packet && tty->link->ctrl_status)
2024                 mask |= POLLPRI | POLLIN | POLLRDNORM;
2025         if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2026                 mask |= POLLHUP;
2027         if (tty_hung_up_p(file))
2028                 mask |= POLLHUP;
2029         if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2030                 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2031                         tty->minimum_to_wake = MIN_CHAR(tty);
2032                 else
2033                         tty->minimum_to_wake = 1;
2034         }
2035         if (tty->ops->write && !tty_is_writelocked(tty) &&
2036                         tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2037                         tty_write_room(tty) > 0)
2038                 mask |= POLLOUT | POLLWRNORM;
2039         return mask;
2040 }
2041
2042 static unsigned long inq_canon(struct tty_struct *tty)
2043 {
2044         int nr, head, tail;
2045
2046         if (!tty->canon_data)
2047                 return 0;
2048         head = tty->canon_head;
2049         tail = tty->read_tail;
2050         nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2051         /* Skip EOF-chars.. */
2052         while (head != tail) {
2053                 if (test_bit(tail, tty->read_flags) &&
2054                     tty->read_buf[tail] == __DISABLED_CHAR)
2055                         nr--;
2056                 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2057         }
2058         return nr;
2059 }
2060
2061 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2062                        unsigned int cmd, unsigned long arg)
2063 {
2064         int retval;
2065
2066         switch (cmd) {
2067         case TIOCOUTQ:
2068                 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2069         case TIOCINQ:
2070                 /* FIXME: Locking */
2071                 retval = tty->read_cnt;
2072                 if (L_ICANON(tty))
2073                         retval = inq_canon(tty);
2074                 return put_user(retval, (unsigned int __user *) arg);
2075         default:
2076                 return n_tty_ioctl_helper(tty, file, cmd, arg);
2077         }
2078 }
2079
2080 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2081         .magic           = TTY_LDISC_MAGIC,
2082         .name            = "n_tty",
2083         .open            = n_tty_open,
2084         .close           = n_tty_close,
2085         .flush_buffer    = n_tty_flush_buffer,
2086         .chars_in_buffer = n_tty_chars_in_buffer,
2087         .read            = n_tty_read,
2088         .write           = n_tty_write,
2089         .ioctl           = n_tty_ioctl,
2090         .set_termios     = n_tty_set_termios,
2091         .poll            = n_tty_poll,
2092         .receive_buf     = n_tty_receive_buf,
2093         .write_wakeup    = n_tty_write_wakeup
2094 };
2095
2096 /**
2097  *      n_tty_inherit_ops       -       inherit N_TTY methods
2098  *      @ops: struct tty_ldisc_ops where to save N_TTY methods
2099  *
2100  *      Used by a generic struct tty_ldisc_ops to easily inherit N_TTY
2101  *      methods.
2102  */
2103
2104 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2105 {
2106         *ops = tty_ldisc_N_TTY;
2107         ops->owner = NULL;
2108         ops->refcount = ops->flags = 0;
2109 }
2110 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);