2 * n_tty.c --- implements the N_TTY line discipline.
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,
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.
13 * Written by Theodore Ts'o, Copyright 1994.
15 * This file also contains code originally written by Linus Torvalds,
16 * Copyright 1991, 1992, 1993, and by Julian Cowley, Copyright 1994.
18 * This file may be redistributed under the terms of the GNU General Public
21 * Reduced memory usage for older ARM systems - Russell King.
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.
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
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>
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>
53 #include <asm/system.h>
55 /* number of characters left in xmit buffer before select has we have room */
56 #define WAKEUP_CHARS 256
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.
63 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
64 #define TTY_THRESHOLD_UNTHROTTLE 128
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
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
77 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
78 unsigned char __user *ptr)
80 tty_audit_add_data(tty, &x, 1);
81 return put_user(x, ptr);
85 * n_tty_set__room - receive space
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
94 static void n_tty_set_room(struct tty_struct *tty)
96 /* tty->read_cnt is not read locked ? */
97 int left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
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.
106 left = tty->icanon && !tty->canon_data;
107 tty->receive_room = left;
110 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
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);
120 * put_tty_queue - add character to tty
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
129 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
133 * The problem of stomping on the buffers ends here.
134 * Why didn't anyone see this one coming? --AJK
136 spin_lock_irqsave(&tty->read_lock, flags);
137 put_tty_queue_nolock(c, tty);
138 spin_unlock_irqrestore(&tty->read_lock, flags);
142 * check_unthrottle - allow new receive data
145 * Check whether to call the driver unthrottle functions
147 * Can sleep, may be called under the atomic_read_lock mutex but
148 * this is not guaranteed.
150 static void check_unthrottle(struct tty_struct *tty)
157 * reset_buffer_flags - reset buffer state
158 * @tty: terminal to reset
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().
164 * Locking: tty_read_lock for read fields.
167 static void reset_buffer_flags(struct tty_struct *tty)
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);
175 mutex_lock(&tty->echo_lock);
176 tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
177 mutex_unlock(&tty->echo_lock);
179 tty->canon_head = tty->canon_data = tty->erasing = 0;
180 memset(&tty->read_flags, 0, sizeof tty->read_flags);
182 check_unthrottle(tty);
186 * n_tty_flush_buffer - clean input queue
187 * @tty: terminal device
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).
194 * Locking: ctrl_lock, read_lock.
197 static void n_tty_flush_buffer(struct tty_struct *tty)
200 /* clear everything and unthrottle the driver */
201 reset_buffer_flags(tty);
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);
211 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
215 * n_tty_chars_in_buffer - report available bytes
218 * Report the number of characters buffered to be delivered to user
219 * at this instant in time.
224 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
229 spin_lock_irqsave(&tty->read_lock, flags);
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);
237 spin_unlock_irqrestore(&tty->read_lock, flags);
242 * is_utf8_continuation - utf8 multibyte check
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
250 static inline int is_utf8_continuation(unsigned char c)
252 return (c & 0xc0) == 0x80;
256 * is_continuation - multibyte check
259 * Returns true if the utf8 character 'c' is a multibyte continuation
260 * character and the terminal is in unicode mode.
263 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
265 return I_IUTF8(tty) && is_utf8_continuation(c);
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
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.
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.
283 * Returns the number of bytes of buffer space used or -1 if
286 * Locking: should be called under the output_lock to protect
287 * the column state and space left in the buffer
290 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
304 tty->canon_column = tty->column = 0;
305 tty->ops->write(tty, "\r\n", 2);
308 tty->canon_column = tty->column;
311 if (O_ONOCR(tty) && tty->column == 0)
316 tty->canon_column = tty->column = 0;
319 tty->canon_column = tty->column = 0;
322 spaces = 8 - (tty->column & 7);
323 if (O_TABDLY(tty) == XTABS) {
326 tty->column += spaces;
327 tty->ops->write(tty, " ", spaces);
330 tty->column += spaces;
340 if (!is_continuation(c, tty))
346 tty_put_char(tty, c);
351 * process_output - output post processor
352 * @c: character (or partial unicode symbol)
353 * @tty: terminal device
355 * Output one character with OPOST processing.
356 * Returns -1 when the output device is full and the character
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)
364 static int process_output(unsigned char c, struct tty_struct *tty)
368 mutex_lock(&tty->output_lock);
370 space = tty_write_room(tty);
371 retval = do_output_char(c, tty, space);
373 mutex_unlock(&tty->output_lock);
381 * process_output_block - block post processor
382 * @tty: terminal device
383 * @buf: character buffer
384 * @nr: number of bytes to output
386 * Output a block of characters with OPOST processing.
387 * Returns the number of characters output.
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.
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)
399 static ssize_t process_output_block(struct tty_struct *tty,
400 const unsigned char *buf, unsigned int nr)
404 const unsigned char *cp;
406 mutex_lock(&tty->output_lock);
408 space = tty_write_room(tty);
410 mutex_unlock(&tty->output_lock);
416 for (i = 0, cp = buf; i < nr; i++, cp++) {
417 unsigned char c = *cp;
425 tty->canon_column = tty->column;
428 if (O_ONOCR(tty) && tty->column == 0)
432 tty->canon_column = tty->column = 0;
444 if (!is_continuation(c, tty))
451 i = tty->ops->write(tty, buf, i);
453 mutex_unlock(&tty->output_lock);
458 * process_echoes - write pending echo characters
459 * @tty: terminal device
461 * Write previously buffered echo (and other ldisc-generated)
462 * characters to the tty.
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.
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
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.
479 * Locking: output_lock to protect column state and space left,
480 * echo_lock to protect the echo buffer
483 static void process_echoes(struct tty_struct *tty)
487 unsigned char *cp, *buf_end;
492 mutex_lock(&tty->output_lock);
493 mutex_lock(&tty->echo_lock);
495 space = tty_write_room(tty);
497 buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
498 cp = tty->echo_buf + tty->echo_pos;
502 if (c == ECHO_OP_START) {
505 int no_space_left = 0;
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.
514 opp -= N_TTY_BUF_SIZE;
518 unsigned int num_chars, num_bs;
520 case ECHO_OP_ERASE_TAB:
521 if (++opp == buf_end)
522 opp -= N_TTY_BUF_SIZE;
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.
535 if (!(num_chars & 0x80))
536 num_chars += tty->canon_column;
537 num_bs = 8 - (num_chars & 7);
539 if (num_bs > space) {
545 tty_put_char(tty, '\b');
553 case ECHO_OP_SET_CANON_COL:
554 tty->canon_column = tty->column;
559 case ECHO_OP_MOVE_BACK_COL:
567 /* This is an escaped echo op start code */
572 tty_put_char(tty, ECHO_OP_START);
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.
593 tty_put_char(tty, '^');
594 tty_put_char(tty, op ^ 0100);
605 !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
606 int retval = do_output_char(c, tty, space);
613 tty_put_char(tty, c);
620 /* When end of circular buffer reached, wrap around */
622 cp -= N_TTY_BUF_SIZE;
628 tty->echo_overrun = 0;
630 int num_processed = tty->echo_cnt - nr;
631 tty->echo_pos += num_processed;
632 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
634 if (num_processed > 0)
635 tty->echo_overrun = 0;
638 mutex_unlock(&tty->echo_lock);
639 mutex_unlock(&tty->output_lock);
641 if (tty->ops->flush_chars)
642 tty->ops->flush_chars(tty);
646 * add_echo_byte - add a byte to the echo buffer
647 * @c: unicode byte to echo
648 * @tty: terminal device
650 * Add a character or operation byte to the echo buffer.
652 * Should be called under the echo lock to protect the echo buffer.
655 static void add_echo_byte(unsigned char c, struct tty_struct *tty)
659 if (tty->echo_cnt == N_TTY_BUF_SIZE) {
660 /* Circular buffer is already at capacity */
661 new_byte_pos = tty->echo_pos;
664 * Since the buffer start position needs to be advanced,
665 * be sure to step by a whole operation byte group.
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)] ==
680 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
682 tty->echo_overrun = 1;
684 new_byte_pos = tty->echo_pos + tty->echo_cnt;
685 new_byte_pos &= N_TTY_BUF_SIZE - 1;
689 tty->echo_buf[new_byte_pos] = c;
693 * echo_move_back_col - add operation to move back a column
694 * @tty: terminal device
696 * Add an operation to the echo buffer to move back one column.
698 * Locking: echo_lock to protect the echo buffer
701 static void echo_move_back_col(struct tty_struct *tty)
703 mutex_lock(&tty->echo_lock);
705 add_echo_byte(ECHO_OP_START, tty);
706 add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
708 mutex_unlock(&tty->echo_lock);
712 * echo_set_canon_col - add operation to set the canon column
713 * @tty: terminal device
715 * Add an operation to the echo buffer to set the canon column
716 * to the current column.
718 * Locking: echo_lock to protect the echo buffer
721 static void echo_set_canon_col(struct tty_struct *tty)
723 mutex_lock(&tty->echo_lock);
725 add_echo_byte(ECHO_OP_START, tty);
726 add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
728 mutex_unlock(&tty->echo_lock);
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
737 * Add an operation to the echo buffer to erase a tab.
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
745 * Locking: echo_lock to protect the echo buffer
748 static void echo_erase_tab(unsigned int num_chars, int after_tab,
749 struct tty_struct *tty)
751 mutex_lock(&tty->echo_lock);
753 add_echo_byte(ECHO_OP_START, tty);
754 add_echo_byte(ECHO_OP_ERASE_TAB, tty);
756 /* We only need to know this modulo 8 (tab spacing) */
759 /* Set the high bit as a flag if num_chars is after a previous tab */
763 add_echo_byte(num_chars, tty);
765 mutex_unlock(&tty->echo_lock);
769 * echo_char_raw - echo a character raw
770 * @c: unicode byte to echo
771 * @tty: terminal device
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.
776 * This variant does not treat control characters specially.
778 * Locking: echo_lock to protect the echo buffer
781 static void echo_char_raw(unsigned char c, struct tty_struct *tty)
783 mutex_lock(&tty->echo_lock);
785 if (c == ECHO_OP_START) {
786 add_echo_byte(ECHO_OP_START, tty);
787 add_echo_byte(ECHO_OP_START, tty);
789 add_echo_byte(c, tty);
792 mutex_unlock(&tty->echo_lock);
796 * echo_char - echo a character
797 * @c: unicode byte to echo
798 * @tty: terminal device
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.
803 * This variant tags control characters to be echoed as "^X"
804 * (where X is the letter representing the control char).
806 * Locking: echo_lock to protect the echo buffer
809 static void echo_char(unsigned char c, struct tty_struct *tty)
811 mutex_lock(&tty->echo_lock);
813 if (c == ECHO_OP_START) {
814 add_echo_byte(ECHO_OP_START, tty);
815 add_echo_byte(ECHO_OP_START, tty);
817 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
818 add_echo_byte(ECHO_OP_START, tty);
819 add_echo_byte(c, tty);
822 mutex_unlock(&tty->echo_lock);
826 * finish_erasing - complete erase
827 * @tty: tty doing the erase
830 static inline void finish_erasing(struct tty_struct *tty)
833 echo_char_raw('/', tty);
839 * eraser - handle erase function
840 * @c: character input
841 * @tty: terminal device
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.
847 * Locking: read_lock for tty buffers
850 static void eraser(unsigned char c, struct tty_struct *tty)
852 enum { ERASE, WERASE, KILL } kill_type;
853 int head, seen_alnums, cnt;
856 /* FIXME: locking needed ? */
857 if (tty->read_head == tty->canon_head) {
858 /* process_output('\a', tty); */ /* what do you think? */
861 if (c == ERASE_CHAR(tty))
863 else if (c == WERASE_CHAR(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);
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);
881 echo_char(KILL_CHAR(tty), tty);
882 /* Add a newline if ECHOK is on and ECHOKE is off. */
884 echo_char_raw('\n', tty);
891 /* FIXME: Locking ?? */
892 while (tty->read_head != tty->canon_head) {
893 head = tty->read_head;
895 /* erase a single possibly multibyte character */
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);
901 /* do not partially erase */
902 if (is_continuation(c, tty))
905 if (kill_type == WERASE) {
906 /* Equivalent to BSD's ALTWERASE. */
907 if (isalnum(c) || c == '_')
909 else if (seen_alnums)
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);
918 if (L_ECHOPRT(tty)) {
920 echo_char_raw('\\', tty);
923 /* if cnt > 1, output a multi-byte character */
926 head = (head+1) & (N_TTY_BUF_SIZE-1);
927 echo_char_raw(tty->read_buf[head], tty);
928 echo_move_back_col(tty);
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;
935 unsigned long tail = tty->read_head;
938 * Count the columns used for characters
939 * since the start of input or after a
941 * This info is used to go back the correct
944 while (tail != tty->canon_head) {
945 tail = (tail-1) & (N_TTY_BUF_SIZE-1);
946 c = tty->read_buf[tail];
950 } else if (iscntrl(c)) {
953 } else if (!is_continuation(c, tty)) {
957 echo_erase_tab(num_chars, after_tab, tty);
959 if (iscntrl(c) && L_ECHOCTL(tty)) {
960 echo_char_raw('\b', tty);
961 echo_char_raw(' ', tty);
962 echo_char_raw('\b', tty);
964 if (!iscntrl(c) || L_ECHOCTL(tty)) {
965 echo_char_raw('\b', tty);
966 echo_char_raw(' ', tty);
967 echo_char_raw('\b', tty);
971 if (kill_type == ERASE)
974 if (tty->read_head == tty->canon_head && L_ECHO(tty))
979 * isig - handle the ISIG optio
982 * @flush: force flush
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.
989 * Locking: ctrl_lock, read_lock (both via flush buffer)
992 static inline void isig(int sig, struct tty_struct *tty, int flush)
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);
1003 * n_tty_receive_break - handle break
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.
1009 * Called from the receive_buf path so single threaded.
1012 static inline void n_tty_receive_break(struct tty_struct *tty)
1016 if (I_BRKINT(tty)) {
1017 isig(SIGINT, tty, 1);
1020 if (I_PARMRK(tty)) {
1021 put_tty_queue('\377', tty);
1022 put_tty_queue('\0', tty);
1024 put_tty_queue('\0', tty);
1025 wake_up_interruptible(&tty->read_wait);
1029 * n_tty_receive_overrun - handle overrun reporting
1032 * Data arrived faster than we could process it. While the tty
1033 * driver has flagged this the bits that were missed are gone
1036 * Called from the receive_buf path so single threaded. Does not
1037 * need locking as num_overrun and overrun_time are function
1041 static inline void n_tty_receive_overrun(struct tty_struct *tty)
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",
1051 tty->overrun_time = jiffies;
1052 tty->num_overrun = 0;
1057 * n_tty_receive_parity_error - error notifier
1058 * @tty: terminal device
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.
1064 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
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);
1076 put_tty_queue(c, tty);
1077 wake_up_interruptible(&tty->read_wait);
1081 * n_tty_receive_char - perform processing
1082 * @tty: terminal device
1085 * Process an individual character of input received from the driver.
1086 * This is serialized with respect to itself by the rules for the
1090 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1092 unsigned long flags;
1096 put_tty_queue(c, tty);
1102 if (I_IUCLC(tty) && L_IEXTEN(tty))
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)) {
1109 process_echoes(tty);
1114 if (c == START_CHAR(tty)) {
1116 process_echoes(tty);
1117 } else if (c == STOP_CHAR(tty))
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
1129 if (!test_bit(c, tty->process_char_map) || tty->lnext) {
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 */
1135 process_output('\a', 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);
1144 process_echoes(tty);
1147 put_tty_queue(c, tty);
1148 put_tty_queue(c, tty);
1153 if (c == START_CHAR(tty)) {
1155 process_echoes(tty);
1158 if (c == STOP_CHAR(tty)) {
1167 if (c == INTR_CHAR(tty))
1170 if (c == QUIT_CHAR(tty))
1173 if (c == SUSP_CHAR(tty)) {
1176 * Note that we do not use isig() here because we want
1178 * 1) flush, 2) echo, 3) signal
1180 if (!L_NOFLSH(tty)) {
1181 n_tty_flush_buffer(tty);
1182 tty_driver_flush_buffer(tty);
1188 process_echoes(tty);
1191 kill_pgrp(tty->pgrp, signal, 1);
1201 } else if (c == '\n' && I_INLCR(tty))
1205 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1206 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1208 process_echoes(tty);
1211 if (c == LNEXT_CHAR(tty) && L_IEXTEN(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);
1223 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1225 unsigned long tail = tty->canon_head;
1227 finish_erasing(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);
1234 process_echoes(tty);
1238 if (tty->read_cnt >= N_TTY_BUF_SIZE) {
1240 process_output('\a', tty);
1243 if (L_ECHO(tty) || L_ECHONL(tty)) {
1244 echo_char_raw('\n', tty);
1245 process_echoes(tty);
1247 goto handle_newline;
1249 if (c == EOF_CHAR(tty)) {
1250 if (tty->read_cnt >= N_TTY_BUF_SIZE)
1252 if (tty->canon_head != tty->read_head)
1253 set_bit(TTY_PUSH, &tty->flags);
1254 c = __DISABLED_CHAR;
1255 goto handle_newline;
1257 if ((c == EOL_CHAR(tty)) ||
1258 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1259 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1261 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1263 process_output('\a', tty);
1267 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1270 /* Record the column of first canon char. */
1271 if (tty->canon_head == tty->read_head)
1272 echo_set_canon_col(tty);
1274 process_echoes(tty);
1277 * XXX does PARMRK doubling happen for
1278 * EOL_CHAR and EOL2_CHAR?
1281 put_tty_queue(c, tty);
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;
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);
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 */
1301 process_output('\a', tty);
1305 finish_erasing(tty);
1307 echo_char_raw('\n', tty);
1309 /* Record the column of first canon char. */
1310 if (tty->canon_head == tty->read_head)
1311 echo_set_canon_col(tty);
1314 process_echoes(tty);
1318 put_tty_queue(c, tty);
1320 put_tty_queue(c, tty);
1325 * n_tty_write_wakeup - asynchronous I/O notifier
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
1333 static void n_tty_write_wakeup(struct tty_struct *tty)
1335 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1336 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1340 * n_tty_receive_buf - data receive
1341 * @tty: terminal device
1344 * @count: characters
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)
1352 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1353 char *fp, int count)
1355 const unsigned char *p;
1356 char *f, flags = TTY_NORMAL;
1359 unsigned long cpuflags;
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);
1369 memcpy(tty->read_buf + tty->read_head, cp, i);
1370 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1375 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1376 N_TTY_BUF_SIZE - tty->read_head);
1378 memcpy(tty->read_buf + tty->read_head, cp, i);
1379 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1381 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1383 for (i = count, p = cp, f = fp; i; i--, p++) {
1388 n_tty_receive_char(tty, *p);
1391 n_tty_receive_break(tty);
1395 n_tty_receive_parity_error(tty, *p);
1398 n_tty_receive_overrun(tty);
1401 printk(KERN_ERR "%s: unknown flag %d\n",
1402 tty_name(tty, buf), flags);
1406 if (tty->ops->flush_chars)
1407 tty->ops->flush_chars(tty);
1410 n_tty_set_room(tty);
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);
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!
1423 if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1427 int is_ignored(int sig)
1429 return (sigismember(¤t->blocked, sig) ||
1430 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1434 * n_tty_set_termios - termios data changed
1436 * @old: previous data
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.
1444 * Locking: Caller holds tty->termios_mutex
1447 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1449 int canon_change = 1;
1453 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1455 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1456 tty->canon_head = tty->read_tail;
1457 tty->canon_data = 0;
1461 if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1462 wake_up_interruptible(&tty->read_wait);
1464 tty->icanon = (L_ICANON(tty) != 0);
1465 if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1468 n_tty_set_room(tty);
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) ||
1475 memset(tty->process_char_map, 0, 256/8);
1477 if (I_IGNCR(tty) || I_ICRNL(tty))
1478 set_bit('\r', tty->process_char_map);
1480 set_bit('\n', tty->process_char_map);
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);
1496 set_bit(REPRINT_CHAR(tty),
1497 tty->process_char_map);
1501 set_bit(START_CHAR(tty), tty->process_char_map);
1502 set_bit(STOP_CHAR(tty), tty->process_char_map);
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);
1509 clear_bit(__DISABLED_CHAR, tty->process_char_map);
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))
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);
1528 * n_tty_close - close the ldisc for this tty
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.
1537 static void n_tty_close(struct tty_struct *tty)
1539 n_tty_flush_buffer(tty);
1540 if (tty->read_buf) {
1541 kfree(tty->read_buf);
1542 tty->read_buf = NULL;
1544 if (tty->echo_buf) {
1545 kfree(tty->echo_buf);
1546 tty->echo_buf = NULL;
1551 * n_tty_open - open an ldisc
1552 * @tty: terminal to open
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
1560 static int n_tty_open(struct tty_struct *tty)
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);
1571 if (!tty->echo_buf) {
1572 tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1577 reset_buffer_flags(tty);
1579 n_tty_set_termios(tty, NULL);
1580 tty->minimum_to_wake = 1;
1585 static inline int input_available_p(struct tty_struct *tty, int amt)
1587 tty_flush_to_ldisc(tty);
1589 if (tty->canon_data)
1591 } else if (tty->read_cnt >= (amt ? amt : 1))
1598 * copy_from_read_buf - copy read data directly
1599 * @tty: terminal device
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.
1610 * Called under the tty->atomic_read_lock sem
1614 static int copy_from_read_buf(struct tty_struct *tty,
1615 unsigned char __user **b,
1621 unsigned long flags;
1624 spin_lock_irqsave(&tty->read_lock, flags);
1625 n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1627 spin_unlock_irqrestore(&tty->read_lock, flags);
1629 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
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);
1635 spin_unlock_irqrestore(&tty->read_lock, flags);
1642 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1646 * job_control - check job control
1648 * @file: file handle
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.
1655 * Locking: None - redirected write test is safe, testing
1656 * current->signal should possibly lock current->sighand
1660 static int job_control(struct tty_struct *tty, struct file *file)
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) {
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())
1675 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1676 set_thread_flag(TIF_SIGPENDING);
1677 return -ERESTARTSYS;
1685 * n_tty_read - read function for tty
1687 * @file: file object
1688 * @buf: userspace buffer pointer
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.
1696 * This code must be sure never to sleep through a hangup.
1699 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1700 unsigned char __user *buf, size_t nr)
1702 unsigned char __user *b = buf;
1703 DECLARE_WAITQUEUE(wait, current);
1709 unsigned long flags;
1714 BUG_ON(!tty->read_buf);
1716 c = job_control(tty, file);
1721 timeout = MAX_SCHEDULE_TIMEOUT;
1723 time = (HZ / 10) * TIME_CHAR(tty);
1724 minimum = MIN_CHAR(tty);
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;
1737 tty->minimum_to_wake = minimum = 1;
1742 * Internal serialization of reads.
1744 if (file->f_flags & O_NONBLOCK) {
1745 if (!mutex_trylock(&tty->atomic_read_lock))
1748 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1749 return -ERESTARTSYS;
1751 packet = tty->packet;
1753 add_wait_queue(&tty->read_wait, &wait);
1755 /* First test for status change. */
1756 if (packet && tty->link->ctrl_status) {
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++)) {
1772 /* This statement must be first before checking for input
1773 so that any interrupt will set the state back to
1775 set_current_state(TASK_INTERRUPTIBLE);
1777 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1778 ((minimum - (b - buf)) >= 1))
1779 tty->minimum_to_wake = (minimum - (b - buf));
1781 if (!input_available_p(tty, 0)) {
1782 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1786 if (tty_hung_up_p(file))
1790 if (file->f_flags & O_NONBLOCK) {
1794 if (signal_pending(current)) {
1795 retval = -ERESTARTSYS;
1798 /* FIXME: does n_tty_set_room need locking ? */
1799 n_tty_set_room(tty);
1800 timeout = schedule_timeout(timeout);
1803 __set_current_state(TASK_RUNNING);
1805 /* Deal with packet mode. */
1806 if (packet && b == buf) {
1807 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1816 /* N.B. avoid overrun if nr == 0 */
1817 while (nr && tty->read_cnt) {
1820 eol = test_and_clear_bit(tty->read_tail,
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));
1828 /* this test should be redundant:
1829 * we shouldn't be reading data if
1832 if (--tty->canon_data < 0)
1833 tty->canon_data = 0;
1835 spin_unlock_irqrestore(&tty->read_lock, flags);
1837 if (!eol || (c != __DISABLED_CHAR)) {
1838 if (tty_put_user(tty, c, b++)) {
1846 tty_audit_push(tty);
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);
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.
1871 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1872 n_tty_set_room(tty);
1873 check_unthrottle(tty);
1876 if (b - buf >= minimum)
1881 mutex_unlock(&tty->atomic_read_lock);
1882 remove_wait_queue(&tty->read_wait, &wait);
1884 if (!waitqueue_active(&tty->read_wait))
1885 tty->minimum_to_wake = minimum;
1887 __set_current_state(TASK_RUNNING);
1892 clear_bit(TTY_PUSH, &tty->flags);
1893 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1896 n_tty_set_room(tty);
1901 * n_tty_write - write function for tty
1903 * @file: file object
1904 * @buf: userspace buffer pointer
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.
1915 * This code must be sure never to sleep through a hangup.
1917 * Locking: output_lock to protect column state and space left
1918 * (note that the process_output*() functions take this
1922 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1923 const unsigned char *buf, size_t nr)
1925 const unsigned char *b = buf;
1926 DECLARE_WAITQUEUE(wait, current);
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);
1937 /* Write out any echoed characters that are still pending */
1938 process_echoes(tty);
1940 add_wait_queue(&tty->write_wait, &wait);
1942 set_current_state(TASK_INTERRUPTIBLE);
1943 if (signal_pending(current)) {
1944 retval = -ERESTARTSYS;
1947 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1951 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1953 ssize_t num = process_output_block(tty, b, nr);
1965 if (process_output(c, tty) < 0)
1969 if (tty->ops->flush_chars)
1970 tty->ops->flush_chars(tty);
1973 c = tty->ops->write(tty, b, nr);
1986 if (file->f_flags & O_NONBLOCK) {
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;
2001 * n_tty_poll - poll method for N_TTY
2002 * @tty: terminal device
2003 * @file: file accessing it
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.
2010 * This code must be sure never to sleep through a hangup.
2011 * Called without the kernel lock held - fine
2014 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2017 unsigned int mask = 0;
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))
2027 if (tty_hung_up_p(file))
2029 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2030 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2031 tty->minimum_to_wake = MIN_CHAR(tty);
2033 tty->minimum_to_wake = 1;
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;
2042 static unsigned long inq_canon(struct tty_struct *tty)
2046 if (!tty->canon_data)
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)
2056 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2061 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2062 unsigned int cmd, unsigned long arg)
2068 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2070 /* FIXME: Locking */
2071 retval = tty->read_cnt;
2073 retval = inq_canon(tty);
2074 return put_user(retval, (unsigned int __user *) arg);
2076 return n_tty_ioctl_helper(tty, file, cmd, arg);
2080 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2081 .magic = TTY_LDISC_MAGIC,
2084 .close = n_tty_close,
2085 .flush_buffer = n_tty_flush_buffer,
2086 .chars_in_buffer = n_tty_chars_in_buffer,
2088 .write = n_tty_write,
2089 .ioctl = n_tty_ioctl,
2090 .set_termios = n_tty_set_termios,
2092 .receive_buf = n_tty_receive_buf,
2093 .write_wakeup = n_tty_write_wakeup
2097 * n_tty_inherit_ops - inherit N_TTY methods
2098 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2100 * Used by a generic struct tty_ldisc_ops to easily inherit N_TTY
2104 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2106 *ops = tty_ldisc_N_TTY;
2108 ops->refcount = ops->flags = 0;
2110 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);