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);
84 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
86 if (tty->read_cnt < N_TTY_BUF_SIZE) {
87 tty->read_buf[tty->read_head] = c;
88 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
94 * put_tty_queue - add character to tty
98 * Add a character to the tty read_buf queue. This is done under the
99 * read_lock to serialize character addition and also to protect us
100 * against parallel reads or flushes
103 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
107 * The problem of stomping on the buffers ends here.
108 * Why didn't anyone see this one coming? --AJK
110 spin_lock_irqsave(&tty->read_lock, flags);
111 put_tty_queue_nolock(c, tty);
112 spin_unlock_irqrestore(&tty->read_lock, flags);
116 * check_unthrottle - allow new receive data
119 * Check whether to call the driver unthrottle functions
121 * Can sleep, may be called under the atomic_read_lock mutex but
122 * this is not guaranteed.
124 static void check_unthrottle(struct tty_struct *tty)
131 * reset_buffer_flags - reset buffer state
132 * @tty: terminal to reset
134 * Reset the read buffer counters, clear the flags,
135 * and make sure the driver is unthrottled. Called
136 * from n_tty_open() and n_tty_flush_buffer().
138 * Locking: tty_read_lock for read fields.
141 static void reset_buffer_flags(struct tty_struct *tty)
145 spin_lock_irqsave(&tty->read_lock, flags);
146 tty->read_head = tty->read_tail = tty->read_cnt = 0;
147 spin_unlock_irqrestore(&tty->read_lock, flags);
149 mutex_lock(&tty->echo_lock);
150 tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
151 mutex_unlock(&tty->echo_lock);
153 tty->canon_head = tty->canon_data = tty->erasing = 0;
154 memset(&tty->read_flags, 0, sizeof tty->read_flags);
155 check_unthrottle(tty);
159 * n_tty_flush_buffer - clean input queue
160 * @tty: terminal device
162 * Flush the input buffer. Called when the line discipline is
163 * being closed, when the tty layer wants the buffer flushed (eg
164 * at hangup) or when the N_TTY line discipline internally has to
165 * clean the pending queue (for example some signals).
167 * Locking: ctrl_lock, read_lock.
170 static void n_tty_flush_buffer(struct tty_struct *tty)
173 /* clear everything and unthrottle the driver */
174 reset_buffer_flags(tty);
179 spin_lock_irqsave(&tty->ctrl_lock, flags);
180 if (tty->link->packet) {
181 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
182 wake_up_interruptible(&tty->link->read_wait);
184 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
188 * n_tty_chars_in_buffer - report available bytes
191 * Report the number of characters buffered to be delivered to user
192 * at this instant in time.
197 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
202 spin_lock_irqsave(&tty->read_lock, flags);
205 } else if (tty->canon_data) {
206 n = (tty->canon_head > tty->read_tail) ?
207 tty->canon_head - tty->read_tail :
208 tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
210 spin_unlock_irqrestore(&tty->read_lock, flags);
215 * is_utf8_continuation - utf8 multibyte check
218 * Returns true if the utf8 character 'c' is a multibyte continuation
219 * character. We use this to correctly compute the on screen size
220 * of the character when printing
223 static inline int is_utf8_continuation(unsigned char c)
225 return (c & 0xc0) == 0x80;
229 * is_continuation - multibyte check
232 * Returns true if the utf8 character 'c' is a multibyte continuation
233 * character and the terminal is in unicode mode.
236 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
238 return I_IUTF8(tty) && is_utf8_continuation(c);
242 * do_output_char - output one character
243 * @c: character (or partial unicode symbol)
244 * @tty: terminal device
245 * @space: space available in tty driver write buffer
247 * This is a helper function that handles one output character
248 * (including special characters like TAB, CR, LF, etc.),
249 * doing OPOST processing and putting the results in the
250 * tty driver's write buffer.
252 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
253 * and NLDLY. They simply aren't relevant in the world today.
254 * If you ever need them, add them here.
256 * Returns the number of bytes of buffer space used or -1 if
259 * Locking: should be called under the output_lock to protect
260 * the column state and space left in the buffer
263 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
277 tty->canon_column = tty->column = 0;
278 tty->ops->write(tty, "\r\n", 2);
281 tty->canon_column = tty->column;
284 if (O_ONOCR(tty) && tty->column == 0)
289 tty->canon_column = tty->column = 0;
292 tty->canon_column = tty->column = 0;
295 spaces = 8 - (tty->column & 7);
296 if (O_TABDLY(tty) == XTABS) {
299 tty->column += spaces;
300 tty->ops->write(tty, " ", spaces);
303 tty->column += spaces;
313 if (!is_continuation(c, tty))
319 tty_put_char(tty, c);
324 * process_output - output post processor
325 * @c: character (or partial unicode symbol)
326 * @tty: terminal device
328 * Output one character with OPOST processing.
329 * Returns -1 when the output device is full and the character
332 * Locking: output_lock to protect column state and space left
333 * (also, this is called from n_tty_write under the
334 * tty layer write lock)
337 static int process_output(unsigned char c, struct tty_struct *tty)
341 mutex_lock(&tty->output_lock);
343 space = tty_write_room(tty);
344 retval = do_output_char(c, tty, space);
346 mutex_unlock(&tty->output_lock);
354 * process_output_block - block post processor
355 * @tty: terminal device
356 * @buf: character buffer
357 * @nr: number of bytes to output
359 * Output a block of characters with OPOST processing.
360 * Returns the number of characters output.
362 * This path is used to speed up block console writes, among other
363 * things when processing blocks of output data. It handles only
364 * the simple cases normally found and helps to generate blocks of
365 * symbols for the console driver and thus improve performance.
367 * Locking: output_lock to protect column state and space left
368 * (also, this is called from n_tty_write under the
369 * tty layer write lock)
372 static ssize_t process_output_block(struct tty_struct *tty,
373 const unsigned char *buf, unsigned int nr)
377 const unsigned char *cp;
379 mutex_lock(&tty->output_lock);
381 space = tty_write_room(tty);
383 mutex_unlock(&tty->output_lock);
389 for (i = 0, cp = buf; i < nr; i++, cp++) {
390 unsigned char c = *cp;
398 tty->canon_column = tty->column;
401 if (O_ONOCR(tty) && tty->column == 0)
405 tty->canon_column = tty->column = 0;
417 if (!is_continuation(c, tty))
424 i = tty->ops->write(tty, buf, i);
426 mutex_unlock(&tty->output_lock);
431 * process_echoes - write pending echo characters
432 * @tty: terminal device
434 * Write previously buffered echo (and other ldisc-generated)
435 * characters to the tty.
437 * Characters generated by the ldisc (including echoes) need to
438 * be buffered because the driver's write buffer can fill during
439 * heavy program output. Echoing straight to the driver will
440 * often fail under these conditions, causing lost characters and
441 * resulting mismatches of ldisc state information.
443 * Since the ldisc state must represent the characters actually sent
444 * to the driver at the time of the write, operations like certain
445 * changes in column state are also saved in the buffer and executed
448 * A circular fifo buffer is used so that the most recent characters
449 * are prioritized. Also, when control characters are echoed with a
450 * prefixed "^", the pair is treated atomically and thus not separated.
452 * Locking: output_lock to protect column state and space left,
453 * echo_lock to protect the echo buffer
456 static void process_echoes(struct tty_struct *tty)
460 unsigned char *cp, *buf_end;
465 mutex_lock(&tty->output_lock);
466 mutex_lock(&tty->echo_lock);
468 space = tty_write_room(tty);
470 buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
471 cp = tty->echo_buf + tty->echo_pos;
475 if (c == ECHO_OP_START) {
478 int no_space_left = 0;
481 * If the buffer byte is the start of a multi-byte
482 * operation, get the next byte, which is either the
483 * op code or a control character value.
487 opp -= N_TTY_BUF_SIZE;
491 unsigned int num_chars, num_bs;
493 case ECHO_OP_ERASE_TAB:
494 if (++opp == buf_end)
495 opp -= N_TTY_BUF_SIZE;
499 * Determine how many columns to go back
500 * in order to erase the tab.
501 * This depends on the number of columns
502 * used by other characters within the tab
503 * area. If this (modulo 8) count is from
504 * the start of input rather than from a
505 * previous tab, we offset by canon column.
506 * Otherwise, tab spacing is normal.
508 if (!(num_chars & 0x80))
509 num_chars += tty->canon_column;
510 num_bs = 8 - (num_chars & 7);
512 if (num_bs > space) {
518 tty_put_char(tty, '\b');
526 case ECHO_OP_SET_CANON_COL:
527 tty->canon_column = tty->column;
532 case ECHO_OP_MOVE_BACK_COL:
540 /* This is an escaped echo op start code */
545 tty_put_char(tty, ECHO_OP_START);
554 * If the op is not a special byte code,
555 * it is a ctrl char tagged to be echoed
556 * as "^X" (where X is the letter
557 * representing the control char).
558 * Note that we must ensure there is
559 * enough space for the whole ctrl pair.
566 tty_put_char(tty, '^');
567 tty_put_char(tty, op ^ 0100);
578 !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
579 int retval = do_output_char(c, tty, space);
586 tty_put_char(tty, c);
593 /* When end of circular buffer reached, wrap around */
595 cp -= N_TTY_BUF_SIZE;
601 tty->echo_overrun = 0;
603 int num_processed = tty->echo_cnt - nr;
604 tty->echo_pos += num_processed;
605 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
607 if (num_processed > 0)
608 tty->echo_overrun = 0;
611 mutex_unlock(&tty->echo_lock);
612 mutex_unlock(&tty->output_lock);
614 if (tty->ops->flush_chars)
615 tty->ops->flush_chars(tty);
619 * add_echo_byte - add a byte to the echo buffer
620 * @c: unicode byte to echo
621 * @tty: terminal device
623 * Add a character or operation byte to the echo buffer.
625 * Should be called under the echo lock to protect the echo buffer.
628 static void add_echo_byte(unsigned char c, struct tty_struct *tty)
632 if (tty->echo_cnt == N_TTY_BUF_SIZE) {
633 /* Circular buffer is already at capacity */
634 new_byte_pos = tty->echo_pos;
637 * Since the buffer start position needs to be advanced,
638 * be sure to step by a whole operation byte group.
640 if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
641 if (tty->echo_buf[(tty->echo_pos + 1) &
642 (N_TTY_BUF_SIZE - 1)] ==
653 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
655 tty->echo_overrun = 1;
657 new_byte_pos = tty->echo_pos + tty->echo_cnt;
658 new_byte_pos &= N_TTY_BUF_SIZE - 1;
662 tty->echo_buf[new_byte_pos] = c;
666 * echo_move_back_col - add operation to move back a column
667 * @tty: terminal device
669 * Add an operation to the echo buffer to move back one column.
671 * Locking: echo_lock to protect the echo buffer
674 static void echo_move_back_col(struct tty_struct *tty)
676 mutex_lock(&tty->echo_lock);
678 add_echo_byte(ECHO_OP_START, tty);
679 add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
681 mutex_unlock(&tty->echo_lock);
685 * echo_set_canon_col - add operation to set the canon column
686 * @tty: terminal device
688 * Add an operation to the echo buffer to set the canon column
689 * to the current column.
691 * Locking: echo_lock to protect the echo buffer
694 static void echo_set_canon_col(struct tty_struct *tty)
696 mutex_lock(&tty->echo_lock);
698 add_echo_byte(ECHO_OP_START, tty);
699 add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
701 mutex_unlock(&tty->echo_lock);
705 * echo_erase_tab - add operation to erase a tab
706 * @num_chars: number of character columns already used
707 * @after_tab: true if num_chars starts after a previous tab
708 * @tty: terminal device
710 * Add an operation to the echo buffer to erase a tab.
712 * Called by the eraser function, which knows how many character
713 * columns have been used since either a previous tab or the start
714 * of input. This information will be used later, along with
715 * canon column (if applicable), to go back the correct number
718 * Locking: echo_lock to protect the echo buffer
721 static void echo_erase_tab(unsigned int num_chars, int after_tab,
722 struct tty_struct *tty)
724 mutex_lock(&tty->echo_lock);
726 add_echo_byte(ECHO_OP_START, tty);
727 add_echo_byte(ECHO_OP_ERASE_TAB, tty);
729 /* We only need to know this modulo 8 (tab spacing) */
732 /* Set the high bit as a flag if num_chars is after a previous tab */
736 add_echo_byte(num_chars, tty);
738 mutex_unlock(&tty->echo_lock);
742 * echo_char_raw - echo a character raw
743 * @c: unicode byte to echo
744 * @tty: terminal device
746 * Echo user input back onto the screen. This must be called only when
747 * L_ECHO(tty) is true. Called from the driver receive_buf path.
749 * This variant does not treat control characters specially.
751 * Locking: echo_lock to protect the echo buffer
754 static void echo_char_raw(unsigned char c, struct tty_struct *tty)
756 mutex_lock(&tty->echo_lock);
758 if (c == ECHO_OP_START) {
759 add_echo_byte(ECHO_OP_START, tty);
760 add_echo_byte(ECHO_OP_START, tty);
762 add_echo_byte(c, tty);
765 mutex_unlock(&tty->echo_lock);
769 * echo_char - echo a character
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 tags control characters to be echoed as "^X"
777 * (where X is the letter representing the control char).
779 * Locking: echo_lock to protect the echo buffer
782 static void echo_char(unsigned char c, struct tty_struct *tty)
784 mutex_lock(&tty->echo_lock);
786 if (c == ECHO_OP_START) {
787 add_echo_byte(ECHO_OP_START, tty);
788 add_echo_byte(ECHO_OP_START, tty);
790 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
791 add_echo_byte(ECHO_OP_START, tty);
792 add_echo_byte(c, tty);
795 mutex_unlock(&tty->echo_lock);
799 * finish_erasing - complete erase
800 * @tty: tty doing the erase
803 static inline void finish_erasing(struct tty_struct *tty)
806 echo_char_raw('/', tty);
812 * eraser - handle erase function
813 * @c: character input
814 * @tty: terminal device
816 * Perform erase and necessary output when an erase character is
817 * present in the stream from the driver layer. Handles the complexities
818 * of UTF-8 multibyte symbols.
820 * Locking: read_lock for tty buffers
823 static void eraser(unsigned char c, struct tty_struct *tty)
825 enum { ERASE, WERASE, KILL } kill_type;
826 int head, seen_alnums, cnt;
829 /* FIXME: locking needed ? */
830 if (tty->read_head == tty->canon_head) {
831 /* process_output('\a', tty); */ /* what do you think? */
834 if (c == ERASE_CHAR(tty))
836 else if (c == WERASE_CHAR(tty))
840 spin_lock_irqsave(&tty->read_lock, flags);
841 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
842 (N_TTY_BUF_SIZE - 1));
843 tty->read_head = tty->canon_head;
844 spin_unlock_irqrestore(&tty->read_lock, flags);
847 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
848 spin_lock_irqsave(&tty->read_lock, flags);
849 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
850 (N_TTY_BUF_SIZE - 1));
851 tty->read_head = tty->canon_head;
852 spin_unlock_irqrestore(&tty->read_lock, flags);
854 echo_char(KILL_CHAR(tty), tty);
855 /* Add a newline if ECHOK is on and ECHOKE is off. */
857 echo_char_raw('\n', tty);
864 /* FIXME: Locking ?? */
865 while (tty->read_head != tty->canon_head) {
866 head = tty->read_head;
868 /* erase a single possibly multibyte character */
870 head = (head - 1) & (N_TTY_BUF_SIZE-1);
871 c = tty->read_buf[head];
872 } while (is_continuation(c, tty) && head != tty->canon_head);
874 /* do not partially erase */
875 if (is_continuation(c, tty))
878 if (kill_type == WERASE) {
879 /* Equivalent to BSD's ALTWERASE. */
880 if (isalnum(c) || c == '_')
882 else if (seen_alnums)
885 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
886 spin_lock_irqsave(&tty->read_lock, flags);
887 tty->read_head = head;
888 tty->read_cnt -= cnt;
889 spin_unlock_irqrestore(&tty->read_lock, flags);
891 if (L_ECHOPRT(tty)) {
893 echo_char_raw('\\', tty);
896 /* if cnt > 1, output a multi-byte character */
899 head = (head+1) & (N_TTY_BUF_SIZE-1);
900 echo_char_raw(tty->read_buf[head], tty);
901 echo_move_back_col(tty);
903 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
904 echo_char(ERASE_CHAR(tty), tty);
905 } else if (c == '\t') {
906 unsigned int num_chars = 0;
908 unsigned long tail = tty->read_head;
911 * Count the columns used for characters
912 * since the start of input or after a
914 * This info is used to go back the correct
917 while (tail != tty->canon_head) {
918 tail = (tail-1) & (N_TTY_BUF_SIZE-1);
919 c = tty->read_buf[tail];
923 } else if (iscntrl(c)) {
926 } else if (!is_continuation(c, tty)) {
930 echo_erase_tab(num_chars, after_tab, tty);
932 if (iscntrl(c) && L_ECHOCTL(tty)) {
933 echo_char_raw('\b', tty);
934 echo_char_raw(' ', tty);
935 echo_char_raw('\b', tty);
937 if (!iscntrl(c) || L_ECHOCTL(tty)) {
938 echo_char_raw('\b', tty);
939 echo_char_raw(' ', tty);
940 echo_char_raw('\b', tty);
944 if (kill_type == ERASE)
947 if (tty->read_head == tty->canon_head && L_ECHO(tty))
952 * isig - handle the ISIG optio
955 * @flush: force flush
957 * Called when a signal is being sent due to terminal input. This
958 * may caus terminal flushing to take place according to the termios
959 * settings and character used. Called from the driver receive_buf
960 * path so serialized.
962 * Locking: ctrl_lock, read_lock (both via flush buffer)
965 static inline void isig(int sig, struct tty_struct *tty, int flush)
968 kill_pgrp(tty->pgrp, sig, 1);
969 if (flush || !L_NOFLSH(tty)) {
970 n_tty_flush_buffer(tty);
971 tty_driver_flush_buffer(tty);
976 * n_tty_receive_break - handle break
979 * An RS232 break event has been hit in the incoming bitstream. This
980 * can cause a variety of events depending upon the termios settings.
982 * Called from the receive_buf path so single threaded.
985 static inline void n_tty_receive_break(struct tty_struct *tty)
990 isig(SIGINT, tty, 1);
994 put_tty_queue('\377', tty);
995 put_tty_queue('\0', tty);
997 put_tty_queue('\0', tty);
998 wake_up_interruptible(&tty->read_wait);
1002 * n_tty_receive_overrun - handle overrun reporting
1005 * Data arrived faster than we could process it. While the tty
1006 * driver has flagged this the bits that were missed are gone
1009 * Called from the receive_buf path so single threaded. Does not
1010 * need locking as num_overrun and overrun_time are function
1014 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1019 if (time_before(tty->overrun_time, jiffies - HZ) ||
1020 time_after(tty->overrun_time, jiffies)) {
1021 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1024 tty->overrun_time = jiffies;
1025 tty->num_overrun = 0;
1030 * n_tty_receive_parity_error - error notifier
1031 * @tty: terminal device
1034 * Process a parity error and queue the right data to indicate
1035 * the error case if necessary. Locking as per n_tty_receive_buf.
1037 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1042 if (I_PARMRK(tty)) {
1043 put_tty_queue('\377', tty);
1044 put_tty_queue('\0', tty);
1045 put_tty_queue(c, tty);
1046 } else if (I_INPCK(tty))
1047 put_tty_queue('\0', tty);
1049 put_tty_queue(c, tty);
1050 wake_up_interruptible(&tty->read_wait);
1054 * n_tty_receive_char - perform processing
1055 * @tty: terminal device
1058 * Process an individual character of input received from the driver.
1059 * This is serialized with respect to itself by the rules for the
1063 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1065 unsigned long flags;
1069 put_tty_queue(c, tty);
1075 if (I_IUCLC(tty) && L_IEXTEN(tty))
1078 if (L_EXTPROC(tty)) {
1079 put_tty_queue(c, tty);
1083 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1084 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1085 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1087 process_echoes(tty);
1092 if (c == START_CHAR(tty)) {
1094 process_echoes(tty);
1095 } else if (c == STOP_CHAR(tty))
1102 * If the previous character was LNEXT, or we know that this
1103 * character is not one of the characters that we'll have to
1104 * handle specially, do shortcut processing to speed things
1107 if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1109 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1110 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1111 /* beep if no space */
1113 process_output('\a', tty);
1117 finish_erasing(tty);
1118 /* Record the column of first canon char. */
1119 if (tty->canon_head == tty->read_head)
1120 echo_set_canon_col(tty);
1122 process_echoes(tty);
1125 put_tty_queue(c, tty);
1126 put_tty_queue(c, tty);
1131 if (c == START_CHAR(tty)) {
1133 process_echoes(tty);
1136 if (c == STOP_CHAR(tty)) {
1145 if (c == INTR_CHAR(tty))
1148 if (c == QUIT_CHAR(tty))
1151 if (c == SUSP_CHAR(tty)) {
1154 * Note that we do not use isig() here because we want
1156 * 1) flush, 2) echo, 3) signal
1158 if (!L_NOFLSH(tty)) {
1159 n_tty_flush_buffer(tty);
1160 tty_driver_flush_buffer(tty);
1166 process_echoes(tty);
1169 kill_pgrp(tty->pgrp, signal, 1);
1179 } else if (c == '\n' && I_INLCR(tty))
1183 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1184 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1186 process_echoes(tty);
1189 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1192 finish_erasing(tty);
1193 if (L_ECHOCTL(tty)) {
1194 echo_char_raw('^', tty);
1195 echo_char_raw('\b', tty);
1196 process_echoes(tty);
1201 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1203 unsigned long tail = tty->canon_head;
1205 finish_erasing(tty);
1207 echo_char_raw('\n', tty);
1208 while (tail != tty->read_head) {
1209 echo_char(tty->read_buf[tail], tty);
1210 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1212 process_echoes(tty);
1216 if (tty->read_cnt >= N_TTY_BUF_SIZE) {
1218 process_output('\a', tty);
1221 if (L_ECHO(tty) || L_ECHONL(tty)) {
1222 echo_char_raw('\n', tty);
1223 process_echoes(tty);
1225 goto handle_newline;
1227 if (c == EOF_CHAR(tty)) {
1228 if (tty->read_cnt >= N_TTY_BUF_SIZE)
1230 if (tty->canon_head != tty->read_head)
1231 set_bit(TTY_PUSH, &tty->flags);
1232 c = __DISABLED_CHAR;
1233 goto handle_newline;
1235 if ((c == EOL_CHAR(tty)) ||
1236 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1237 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1239 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1241 process_output('\a', tty);
1245 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1248 /* Record the column of first canon char. */
1249 if (tty->canon_head == tty->read_head)
1250 echo_set_canon_col(tty);
1252 process_echoes(tty);
1255 * XXX does PARMRK doubling happen for
1256 * EOL_CHAR and EOL2_CHAR?
1259 put_tty_queue(c, tty);
1262 spin_lock_irqsave(&tty->read_lock, flags);
1263 set_bit(tty->read_head, tty->read_flags);
1264 put_tty_queue_nolock(c, tty);
1265 tty->canon_head = tty->read_head;
1267 spin_unlock_irqrestore(&tty->read_lock, flags);
1268 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1269 if (waitqueue_active(&tty->read_wait))
1270 wake_up_interruptible(&tty->read_wait);
1275 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1276 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1277 /* beep if no space */
1279 process_output('\a', tty);
1283 finish_erasing(tty);
1285 echo_char_raw('\n', tty);
1287 /* Record the column of first canon char. */
1288 if (tty->canon_head == tty->read_head)
1289 echo_set_canon_col(tty);
1292 process_echoes(tty);
1296 put_tty_queue(c, tty);
1298 put_tty_queue(c, tty);
1303 * n_tty_write_wakeup - asynchronous I/O notifier
1306 * Required for the ptys, serial driver etc. since processes
1307 * that attach themselves to the master and rely on ASYNC
1308 * IO must be woken up
1311 static void n_tty_write_wakeup(struct tty_struct *tty)
1313 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1314 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1318 * n_tty_receive_buf - data receive
1319 * @tty: terminal device
1322 * @count: characters
1324 * Called by the terminal driver when a block of characters has
1325 * been received. This function must be called from soft contexts
1326 * not from interrupt context. The driver is responsible for making
1327 * calls one at a time and in order (or using flush_to_ldisc)
1330 static unsigned int n_tty_receive_buf(struct tty_struct *tty,
1331 const unsigned char *cp, char *fp, int count)
1333 const unsigned char *p;
1334 char *f, flags = TTY_NORMAL;
1337 unsigned long cpuflags;
1344 if (tty->real_raw) {
1345 spin_lock_irqsave(&tty->read_lock, cpuflags);
1346 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1347 N_TTY_BUF_SIZE - tty->read_head);
1349 memcpy(tty->read_buf + tty->read_head, cp, i);
1350 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1356 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1357 N_TTY_BUF_SIZE - tty->read_head);
1359 memcpy(tty->read_buf + tty->read_head, cp, i);
1360 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1363 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1366 for (i = count, p = cp, f = fp; i; i--, p++) {
1371 n_tty_receive_char(tty, *p);
1374 n_tty_receive_break(tty);
1378 n_tty_receive_parity_error(tty, *p);
1381 n_tty_receive_overrun(tty);
1384 printk(KERN_ERR "%s: unknown flag %d\n",
1385 tty_name(tty, buf), flags);
1389 if (tty->ops->flush_chars)
1390 tty->ops->flush_chars(tty);
1393 if ((!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) ||
1395 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1396 if (waitqueue_active(&tty->read_wait))
1397 wake_up_interruptible(&tty->read_wait);
1401 * Check the remaining room for the input canonicalization
1402 * mode. We don't want to throttle the driver if we're in
1403 * canonical mode and don't have a newline yet!
1405 left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
1407 if (left < TTY_THRESHOLD_THROTTLE)
1413 int is_ignored(int sig)
1415 return (sigismember(¤t->blocked, sig) ||
1416 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1420 * n_tty_set_termios - termios data changed
1422 * @old: previous data
1424 * Called by the tty layer when the user changes termios flags so
1425 * that the line discipline can plan ahead. This function cannot sleep
1426 * and is protected from re-entry by the tty layer. The user is
1427 * guaranteed that this function will not be re-entered or in progress
1428 * when the ldisc is closed.
1430 * Locking: Caller holds tty->termios_mutex
1433 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1435 int canon_change = 1;
1439 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1441 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1442 tty->canon_head = tty->read_tail;
1443 tty->canon_data = 0;
1447 if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1448 wake_up_interruptible(&tty->read_wait);
1450 tty->icanon = (L_ICANON(tty) != 0);
1451 if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1456 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1457 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1458 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1460 memset(tty->process_char_map, 0, 256/8);
1462 if (I_IGNCR(tty) || I_ICRNL(tty))
1463 set_bit('\r', tty->process_char_map);
1465 set_bit('\n', tty->process_char_map);
1467 if (L_ICANON(tty)) {
1468 set_bit(ERASE_CHAR(tty), tty->process_char_map);
1469 set_bit(KILL_CHAR(tty), tty->process_char_map);
1470 set_bit(EOF_CHAR(tty), tty->process_char_map);
1471 set_bit('\n', tty->process_char_map);
1472 set_bit(EOL_CHAR(tty), tty->process_char_map);
1473 if (L_IEXTEN(tty)) {
1474 set_bit(WERASE_CHAR(tty),
1475 tty->process_char_map);
1476 set_bit(LNEXT_CHAR(tty),
1477 tty->process_char_map);
1478 set_bit(EOL2_CHAR(tty),
1479 tty->process_char_map);
1481 set_bit(REPRINT_CHAR(tty),
1482 tty->process_char_map);
1486 set_bit(START_CHAR(tty), tty->process_char_map);
1487 set_bit(STOP_CHAR(tty), tty->process_char_map);
1490 set_bit(INTR_CHAR(tty), tty->process_char_map);
1491 set_bit(QUIT_CHAR(tty), tty->process_char_map);
1492 set_bit(SUSP_CHAR(tty), tty->process_char_map);
1494 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1499 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1500 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1501 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1506 /* The termios change make the tty ready for I/O */
1507 wake_up_interruptible(&tty->write_wait);
1508 wake_up_interruptible(&tty->read_wait);
1512 * n_tty_close - close the ldisc for this tty
1515 * Called from the terminal layer when this line discipline is
1516 * being shut down, either because of a close or becsuse of a
1517 * discipline change. The function will not be called while other
1518 * ldisc methods are in progress.
1521 static void n_tty_close(struct tty_struct *tty)
1523 n_tty_flush_buffer(tty);
1524 if (tty->read_buf) {
1525 kfree(tty->read_buf);
1526 tty->read_buf = NULL;
1528 if (tty->echo_buf) {
1529 kfree(tty->echo_buf);
1530 tty->echo_buf = NULL;
1535 * n_tty_open - open an ldisc
1536 * @tty: terminal to open
1538 * Called when this line discipline is being attached to the
1539 * terminal device. Can sleep. Called serialized so that no
1540 * other events will occur in parallel. No further open will occur
1544 static int n_tty_open(struct tty_struct *tty)
1549 /* These are ugly. Currently a malloc failure here can panic */
1550 if (!tty->read_buf) {
1551 tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1555 if (!tty->echo_buf) {
1556 tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1561 reset_buffer_flags(tty);
1563 n_tty_set_termios(tty, NULL);
1564 tty->minimum_to_wake = 1;
1569 static inline int input_available_p(struct tty_struct *tty, int amt)
1571 tty_flush_to_ldisc(tty);
1572 if (tty->icanon && !L_EXTPROC(tty)) {
1573 if (tty->canon_data)
1575 } else if (tty->read_cnt >= (amt ? amt : 1))
1582 * copy_from_read_buf - copy read data directly
1583 * @tty: terminal device
1587 * Helper function to speed up n_tty_read. It is only called when
1588 * ICANON is off; it copies characters straight from the tty queue to
1589 * user space directly. It can be profitably called twice; once to
1590 * drain the space from the tail pointer to the (physical) end of the
1591 * buffer, and once to drain the space from the (physical) beginning of
1592 * the buffer to head pointer.
1594 * Called under the tty->atomic_read_lock sem
1598 static int copy_from_read_buf(struct tty_struct *tty,
1599 unsigned char __user **b,
1605 unsigned long flags;
1608 spin_lock_irqsave(&tty->read_lock, flags);
1609 n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1611 spin_unlock_irqrestore(&tty->read_lock, flags);
1613 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1615 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1616 spin_lock_irqsave(&tty->read_lock, flags);
1617 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1619 /* Turn single EOF into zero-length read */
1620 if (L_EXTPROC(tty) && tty->icanon && n == 1) {
1621 if (!tty->read_cnt && (*b)[n-1] == EOF_CHAR(tty))
1624 spin_unlock_irqrestore(&tty->read_lock, flags);
1631 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1635 * job_control - check job control
1637 * @file: file handle
1639 * Perform job control management checks on this file/tty descriptor
1640 * and if appropriate send any needed signals and return a negative
1641 * error code if action should be taken.
1644 * Locking: None - redirected write test is safe, testing
1645 * current->signal should possibly lock current->sighand
1649 static int job_control(struct tty_struct *tty, struct file *file)
1651 /* Job control check -- must be done at start and after
1652 every sleep (POSIX.1 7.1.1.4). */
1653 /* NOTE: not yet done after every sleep pending a thorough
1654 check of the logic of this change. -- jlc */
1655 /* don't stop on /dev/console */
1656 if (file->f_op->write != redirected_tty_write &&
1657 current->signal->tty == tty) {
1659 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1660 else if (task_pgrp(current) != tty->pgrp) {
1661 if (is_ignored(SIGTTIN) ||
1662 is_current_pgrp_orphaned())
1664 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1665 set_thread_flag(TIF_SIGPENDING);
1666 return -ERESTARTSYS;
1674 * n_tty_read - read function for tty
1676 * @file: file object
1677 * @buf: userspace buffer pointer
1680 * Perform reads for the line discipline. We are guaranteed that the
1681 * line discipline will not be closed under us but we may get multiple
1682 * parallel readers and must handle this ourselves. We may also get
1683 * a hangup. Always called in user context, may sleep.
1685 * This code must be sure never to sleep through a hangup.
1688 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1689 unsigned char __user *buf, size_t nr)
1691 unsigned char __user *b = buf;
1692 DECLARE_WAITQUEUE(wait, current);
1698 unsigned long flags;
1703 BUG_ON(!tty->read_buf);
1705 c = job_control(tty, file);
1710 timeout = MAX_SCHEDULE_TIMEOUT;
1712 time = (HZ / 10) * TIME_CHAR(tty);
1713 minimum = MIN_CHAR(tty);
1716 tty->minimum_to_wake = 1;
1717 else if (!waitqueue_active(&tty->read_wait) ||
1718 (tty->minimum_to_wake > minimum))
1719 tty->minimum_to_wake = minimum;
1726 tty->minimum_to_wake = minimum = 1;
1731 * Internal serialization of reads.
1733 if (file->f_flags & O_NONBLOCK) {
1734 if (!mutex_trylock(&tty->atomic_read_lock))
1737 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1738 return -ERESTARTSYS;
1740 packet = tty->packet;
1742 add_wait_queue(&tty->read_wait, &wait);
1744 /* First test for status change. */
1745 if (packet && tty->link->ctrl_status) {
1749 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1750 cs = tty->link->ctrl_status;
1751 tty->link->ctrl_status = 0;
1752 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1753 if (tty_put_user(tty, cs, b++)) {
1761 /* This statement must be first before checking for input
1762 so that any interrupt will set the state back to
1764 set_current_state(TASK_INTERRUPTIBLE);
1766 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1767 ((minimum - (b - buf)) >= 1))
1768 tty->minimum_to_wake = (minimum - (b - buf));
1770 if (!input_available_p(tty, 0)) {
1771 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1775 if (tty_hung_up_p(file))
1779 if (file->f_flags & O_NONBLOCK) {
1783 if (signal_pending(current)) {
1784 retval = -ERESTARTSYS;
1787 timeout = schedule_timeout(timeout);
1790 __set_current_state(TASK_RUNNING);
1792 /* Deal with packet mode. */
1793 if (packet && b == buf) {
1794 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1802 if (tty->icanon && !L_EXTPROC(tty)) {
1803 /* N.B. avoid overrun if nr == 0 */
1804 while (nr && tty->read_cnt) {
1807 eol = test_and_clear_bit(tty->read_tail,
1809 c = tty->read_buf[tty->read_tail];
1810 spin_lock_irqsave(&tty->read_lock, flags);
1811 tty->read_tail = ((tty->read_tail+1) &
1812 (N_TTY_BUF_SIZE-1));
1815 /* this test should be redundant:
1816 * we shouldn't be reading data if
1819 if (--tty->canon_data < 0)
1820 tty->canon_data = 0;
1822 spin_unlock_irqrestore(&tty->read_lock, flags);
1824 if (!eol || (c != __DISABLED_CHAR)) {
1825 if (tty_put_user(tty, c, b++)) {
1833 tty_audit_push(tty);
1841 /* The copy function takes the read lock and handles
1842 locking internally for this case */
1843 uncopied = copy_from_read_buf(tty, &b, &nr);
1844 uncopied += copy_from_read_buf(tty, &b, &nr);
1851 /* If there is enough space in the read buffer now, let the
1852 * low-level driver know. We use n_tty_chars_in_buffer() to
1853 * check the buffer, as it now knows about canonical mode.
1854 * Otherwise, if the driver is throttled and the line is
1855 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1856 * we won't get any more characters.
1858 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE)
1859 check_unthrottle(tty);
1861 if (b - buf >= minimum)
1866 mutex_unlock(&tty->atomic_read_lock);
1867 remove_wait_queue(&tty->read_wait, &wait);
1869 if (!waitqueue_active(&tty->read_wait))
1870 tty->minimum_to_wake = minimum;
1872 __set_current_state(TASK_RUNNING);
1877 clear_bit(TTY_PUSH, &tty->flags);
1878 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1885 * n_tty_write - write function for tty
1887 * @file: file object
1888 * @buf: userspace buffer pointer
1891 * Write function of the terminal device. This is serialized with
1892 * respect to other write callers but not to termios changes, reads
1893 * and other such events. Since the receive code will echo characters,
1894 * thus calling driver write methods, the output_lock is used in
1895 * the output processing functions called here as well as in the
1896 * echo processing function to protect the column state and space
1897 * left in the buffer.
1899 * This code must be sure never to sleep through a hangup.
1901 * Locking: output_lock to protect column state and space left
1902 * (note that the process_output*() functions take this
1906 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1907 const unsigned char *buf, size_t nr)
1909 const unsigned char *b = buf;
1910 DECLARE_WAITQUEUE(wait, current);
1914 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1915 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1916 retval = tty_check_change(tty);
1921 /* Write out any echoed characters that are still pending */
1922 process_echoes(tty);
1924 add_wait_queue(&tty->write_wait, &wait);
1926 set_current_state(TASK_INTERRUPTIBLE);
1927 if (signal_pending(current)) {
1928 retval = -ERESTARTSYS;
1931 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1935 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1937 ssize_t num = process_output_block(tty, b, nr);
1949 if (process_output(c, tty) < 0)
1953 if (tty->ops->flush_chars)
1954 tty->ops->flush_chars(tty);
1957 c = tty->ops->write(tty, b, nr);
1970 if (file->f_flags & O_NONBLOCK) {
1977 __set_current_state(TASK_RUNNING);
1978 remove_wait_queue(&tty->write_wait, &wait);
1979 if (b - buf != nr && tty->fasync)
1980 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
1981 return (b - buf) ? b - buf : retval;
1985 * n_tty_poll - poll method for N_TTY
1986 * @tty: terminal device
1987 * @file: file accessing it
1990 * Called when the line discipline is asked to poll() for data or
1991 * for special events. This code is not serialized with respect to
1992 * other events save open/close.
1994 * This code must be sure never to sleep through a hangup.
1995 * Called without the kernel lock held - fine
1998 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2001 unsigned int mask = 0;
2003 poll_wait(file, &tty->read_wait, wait);
2004 poll_wait(file, &tty->write_wait, wait);
2005 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2006 mask |= POLLIN | POLLRDNORM;
2007 if (tty->packet && tty->link->ctrl_status)
2008 mask |= POLLPRI | POLLIN | POLLRDNORM;
2009 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2011 if (tty_hung_up_p(file))
2013 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2014 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2015 tty->minimum_to_wake = MIN_CHAR(tty);
2017 tty->minimum_to_wake = 1;
2019 if (tty->ops->write && !tty_is_writelocked(tty) &&
2020 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2021 tty_write_room(tty) > 0)
2022 mask |= POLLOUT | POLLWRNORM;
2026 static unsigned long inq_canon(struct tty_struct *tty)
2030 if (!tty->canon_data)
2032 head = tty->canon_head;
2033 tail = tty->read_tail;
2034 nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2035 /* Skip EOF-chars.. */
2036 while (head != tail) {
2037 if (test_bit(tail, tty->read_flags) &&
2038 tty->read_buf[tail] == __DISABLED_CHAR)
2040 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2045 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2046 unsigned int cmd, unsigned long arg)
2052 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2054 /* FIXME: Locking */
2055 retval = tty->read_cnt;
2057 retval = inq_canon(tty);
2058 return put_user(retval, (unsigned int __user *) arg);
2060 return n_tty_ioctl_helper(tty, file, cmd, arg);
2064 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2065 .magic = TTY_LDISC_MAGIC,
2068 .close = n_tty_close,
2069 .flush_buffer = n_tty_flush_buffer,
2070 .chars_in_buffer = n_tty_chars_in_buffer,
2072 .write = n_tty_write,
2073 .ioctl = n_tty_ioctl,
2074 .set_termios = n_tty_set_termios,
2076 .receive_buf = n_tty_receive_buf,
2077 .write_wakeup = n_tty_write_wakeup
2081 * n_tty_inherit_ops - inherit N_TTY methods
2082 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2084 * Used by a generic struct tty_ldisc_ops to easily inherit N_TTY
2088 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2090 *ops = tty_ldisc_N_TTY;
2092 ops->refcount = ops->flags = 0;
2094 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);