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