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);