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>
52 #include <asm/system.h>
54 /* number of characters left in xmit buffer before select has we have room */
55 #define WAKEUP_CHARS 256
58 * This defines the low- and high-watermarks for throttling and
59 * unthrottling the TTY driver. These watermarks are used for
60 * controlling the space in the read buffer.
62 #define TTY_THRESHOLD_THROTTLE 128 /* now based on remaining room */
63 #define TTY_THRESHOLD_UNTHROTTLE 128
66 * Special byte codes used in the echo buffer to represent operations
67 * or special handling of characters. Bytes in the echo buffer that
68 * are not part of such special blocks are treated as normal character
71 #define ECHO_OP_START 0xff
72 #define ECHO_OP_MOVE_BACK_COL 0x80
73 #define ECHO_OP_SET_CANON_COL 0x81
74 #define ECHO_OP_ERASE_TAB 0x82
76 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
77 unsigned char __user *ptr)
79 tty_audit_add_data(tty, &x, 1);
80 return put_user(x, ptr);
84 * n_tty_set__room - receive space
87 * Called by the driver to find out how much data it is
88 * permitted to feed to the line discipline without any being lost
89 * and thus to manage flow control. Not serialized. Answers for the
93 static void n_tty_set_room(struct tty_struct *tty)
95 /* tty->read_cnt is not read locked ? */
96 int left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
99 * If we are doing input canonicalization, and there are no
100 * pending newlines, let characters through without limit, so
101 * that erase characters will be handled. Other excess
102 * characters will be beeped.
105 left = tty->icanon && !tty->canon_data;
106 tty->receive_room = left;
109 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
111 if (tty->read_cnt < N_TTY_BUF_SIZE) {
112 tty->read_buf[tty->read_head] = c;
113 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
119 * put_tty_queue - add character to tty
123 * Add a character to the tty read_buf queue. This is done under the
124 * read_lock to serialize character addition and also to protect us
125 * against parallel reads or flushes
128 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
132 * The problem of stomping on the buffers ends here.
133 * Why didn't anyone see this one coming? --AJK
135 spin_lock_irqsave(&tty->read_lock, flags);
136 put_tty_queue_nolock(c, tty);
137 spin_unlock_irqrestore(&tty->read_lock, flags);
141 * check_unthrottle - allow new receive data
144 * Check whether to call the driver unthrottle functions
146 * Can sleep, may be called under the atomic_read_lock mutex but
147 * this is not guaranteed.
149 static void check_unthrottle(struct tty_struct *tty)
156 * reset_buffer_flags - reset buffer state
157 * @tty: terminal to reset
159 * Reset the read buffer counters, clear the flags,
160 * and make sure the driver is unthrottled. Called
161 * from n_tty_open() and n_tty_flush_buffer().
163 * Locking: tty_read_lock for read fields.
166 static void reset_buffer_flags(struct tty_struct *tty)
170 spin_lock_irqsave(&tty->read_lock, flags);
171 tty->read_head = tty->read_tail = tty->read_cnt = 0;
172 spin_unlock_irqrestore(&tty->read_lock, flags);
174 mutex_lock(&tty->echo_lock);
175 tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
176 mutex_unlock(&tty->echo_lock);
178 tty->canon_head = tty->canon_data = tty->erasing = 0;
179 memset(&tty->read_flags, 0, sizeof tty->read_flags);
181 check_unthrottle(tty);
185 * n_tty_flush_buffer - clean input queue
186 * @tty: terminal device
188 * Flush the input buffer. Called when the line discipline is
189 * being closed, when the tty layer wants the buffer flushed (eg
190 * at hangup) or when the N_TTY line discipline internally has to
191 * clean the pending queue (for example some signals).
193 * Locking: ctrl_lock, read_lock.
196 static void n_tty_flush_buffer(struct tty_struct *tty)
199 /* clear everything and unthrottle the driver */
200 reset_buffer_flags(tty);
205 spin_lock_irqsave(&tty->ctrl_lock, flags);
206 if (tty->link->packet) {
207 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
208 wake_up_interruptible(&tty->link->read_wait);
210 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
214 * n_tty_chars_in_buffer - report available bytes
217 * Report the number of characters buffered to be delivered to user
218 * at this instant in time.
223 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
228 spin_lock_irqsave(&tty->read_lock, flags);
231 } else if (tty->canon_data) {
232 n = (tty->canon_head > tty->read_tail) ?
233 tty->canon_head - tty->read_tail :
234 tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
236 spin_unlock_irqrestore(&tty->read_lock, flags);
241 * is_utf8_continuation - utf8 multibyte check
244 * Returns true if the utf8 character 'c' is a multibyte continuation
245 * character. We use this to correctly compute the on screen size
246 * of the character when printing
249 static inline int is_utf8_continuation(unsigned char c)
251 return (c & 0xc0) == 0x80;
255 * is_continuation - multibyte check
258 * Returns true if the utf8 character 'c' is a multibyte continuation
259 * character and the terminal is in unicode mode.
262 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
264 return I_IUTF8(tty) && is_utf8_continuation(c);
268 * do_output_char - output one character
269 * @c: character (or partial unicode symbol)
270 * @tty: terminal device
271 * @space: space available in tty driver write buffer
273 * This is a helper function that handles one output character
274 * (including special characters like TAB, CR, LF, etc.),
275 * putting the results in the tty driver's write buffer.
277 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
278 * and NLDLY. They simply aren't relevant in the world today.
279 * If you ever need them, add them here.
281 * Returns the number of bytes of buffer space used or -1 if
284 * Locking: should be called under the output_lock to protect
285 * the column state and space left in the buffer
288 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
302 tty->canon_column = tty->column = 0;
303 tty->ops->write(tty, "\r\n", 2);
306 tty->canon_column = tty->column;
309 if (O_ONOCR(tty) && tty->column == 0)
314 tty->canon_column = tty->column = 0;
317 tty->canon_column = tty->column = 0;
320 spaces = 8 - (tty->column & 7);
321 if (O_TABDLY(tty) == XTABS) {
324 tty->column += spaces;
325 tty->ops->write(tty, " ", spaces);
328 tty->column += spaces;
338 if (!is_continuation(c, tty))
344 tty_put_char(tty, c);
349 * process_output - output post processor
350 * @c: character (or partial unicode symbol)
351 * @tty: terminal device
353 * Perform OPOST processing. Returns -1 when the output device is
354 * full and the character must be retried.
356 * Locking: output_lock to protect column state and space left
357 * (also, this is called from n_tty_write under the
358 * tty layer write lock)
361 static int process_output(unsigned char c, struct tty_struct *tty)
365 mutex_lock(&tty->output_lock);
367 space = tty_write_room(tty);
368 retval = do_output_char(c, tty, space);
370 mutex_unlock(&tty->output_lock);
378 * process_output_block - block post processor
379 * @tty: terminal device
380 * @inbuf: user buffer
381 * @nr: number of bytes
383 * This path is used to speed up block console writes, among other
384 * things when processing blocks of output data. It handles only
385 * the simple cases normally found and helps to generate blocks of
386 * symbols for the console driver and thus improve performance.
388 * Locking: output_lock to protect column state and space left
389 * (also, this is called from n_tty_write under the
390 * tty layer write lock)
393 static ssize_t process_output_block(struct tty_struct *tty,
394 const unsigned char *buf, unsigned int nr)
398 const unsigned char *cp;
400 mutex_lock(&tty->output_lock);
402 space = tty_write_room(tty);
404 mutex_unlock(&tty->output_lock);
410 for (i = 0, cp = buf; i < nr; i++, cp++) {
411 unsigned char c = *cp;
419 tty->canon_column = tty->column;
422 if (O_ONOCR(tty) && tty->column == 0)
426 tty->canon_column = tty->column = 0;
438 if (!is_continuation(c, tty))
445 i = tty->ops->write(tty, buf, i);
447 mutex_unlock(&tty->output_lock);
452 * process_echoes - write pending echo characters
453 * @tty: terminal device
455 * Write previously buffered echo (and other ldisc-generated)
456 * characters to the tty.
458 * Characters generated by the ldisc (including echoes) need to
459 * be buffered because the driver's write buffer can fill during
460 * heavy program output. Echoing straight to the driver will
461 * often fail under these conditions, causing lost characters and
462 * resulting mismatches of ldisc state information.
464 * Since the ldisc state must represent the characters actually sent
465 * to the driver at the time of the write, operations like certain
466 * changes in column state are also saved in the buffer and executed
469 * A circular fifo buffer is used so that the most recent characters
470 * are prioritized. Also, when control characters are echoed with a
471 * prefixed "^", the pair is treated atomically and thus not separated.
473 * Locking: output_lock to protect column state and space left,
474 * echo_lock to protect the echo buffer
477 static void process_echoes(struct tty_struct *tty)
481 unsigned char *cp, *buf_end;
486 mutex_lock(&tty->output_lock);
487 mutex_lock(&tty->echo_lock);
489 space = tty_write_room(tty);
491 buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
492 cp = tty->echo_buf + tty->echo_pos;
496 if (c == ECHO_OP_START) {
499 int no_space_left = 0;
502 * If the buffer byte is the start of a multi-byte
503 * operation, get the next byte, which is either the
504 * op code or a control character value.
508 opp -= N_TTY_BUF_SIZE;
512 unsigned int num_chars, num_bs;
514 case ECHO_OP_ERASE_TAB:
515 if (++opp == buf_end)
516 opp -= N_TTY_BUF_SIZE;
520 * Determine how many columns to go back
521 * in order to erase the tab.
522 * This depends on the number of columns
523 * used by other characters within the tab
524 * area. If this (modulo 8) count is from
525 * the start of input rather than from a
526 * previous tab, we offset by canon column.
527 * Otherwise, tab spacing is normal.
529 if (!(num_chars & 0x80))
530 num_chars += tty->canon_column;
531 num_bs = 8 - (num_chars & 7);
533 if (num_bs > space) {
539 tty_put_char(tty, '\b');
547 case ECHO_OP_SET_CANON_COL:
548 tty->canon_column = tty->column;
553 case ECHO_OP_MOVE_BACK_COL:
561 /* This is an escaped echo op start code */
566 tty_put_char(tty, ECHO_OP_START);
575 if (L_ECHOCTL(tty)) {
577 * Ensure there is enough space
578 * for the whole ctrl pair.
584 tty_put_char(tty, '^');
585 tty_put_char(tty, op ^ 0100);
593 tty_put_char(tty, op);
598 * If above falls through, this was an
610 retval = do_output_char(c, tty, space);
618 /* When end of circular buffer reached, wrap around */
620 cp -= N_TTY_BUF_SIZE;
626 tty->echo_overrun = 0;
628 int num_processed = tty->echo_cnt - nr;
629 tty->echo_pos += num_processed;
630 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
632 if (num_processed > 0)
633 tty->echo_overrun = 0;
636 mutex_unlock(&tty->echo_lock);
637 mutex_unlock(&tty->output_lock);
639 if (tty->ops->flush_chars)
640 tty->ops->flush_chars(tty);
644 * add_echo_byte - add a byte to the echo buffer
645 * @c: unicode byte to echo
646 * @tty: terminal device
648 * Add a character or operation byte to the echo buffer.
650 * Should be called under the echo lock to protect the echo buffer.
653 static void add_echo_byte(unsigned char c, struct tty_struct *tty)
657 if (tty->echo_cnt == N_TTY_BUF_SIZE) {
658 /* Circular buffer is already at capacity */
659 new_byte_pos = tty->echo_pos;
662 * Since the buffer start position needs to be advanced,
663 * be sure to step by a whole operation byte group.
665 if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START) {
666 if (tty->echo_buf[(tty->echo_pos + 1) &
667 (N_TTY_BUF_SIZE - 1)] ==
678 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
680 tty->echo_overrun = 1;
682 new_byte_pos = tty->echo_pos + tty->echo_cnt;
683 new_byte_pos &= N_TTY_BUF_SIZE - 1;
687 tty->echo_buf[new_byte_pos] = c;
691 * echo_move_back_col - add operation to move back a column
692 * @tty: terminal device
694 * Add an operation to the echo buffer to move back one column.
696 * Locking: echo_lock to protect the echo buffer
699 static void echo_move_back_col(struct tty_struct *tty)
701 mutex_lock(&tty->echo_lock);
703 add_echo_byte(ECHO_OP_START, tty);
704 add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
706 mutex_unlock(&tty->echo_lock);
710 * echo_set_canon_col - add operation to set the canon column
711 * @tty: terminal device
713 * Add an operation to the echo buffer to set the canon column
714 * to the current column.
716 * Locking: echo_lock to protect the echo buffer
719 static void echo_set_canon_col(struct tty_struct *tty)
721 mutex_lock(&tty->echo_lock);
723 add_echo_byte(ECHO_OP_START, tty);
724 add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
726 mutex_unlock(&tty->echo_lock);
730 * echo_erase_tab - add operation to erase a tab
731 * @num_chars: number of character columns already used
732 * @after_tab: true if num_chars starts after a previous tab
733 * @tty: terminal device
735 * Add an operation to the echo buffer to erase a tab.
737 * Called by the eraser function, which knows how many character
738 * columns have been used since either a previous tab or the start
739 * of input. This information will be used later, along with
740 * canon column (if applicable), to go back the correct number
743 * Locking: echo_lock to protect the echo buffer
746 static void echo_erase_tab(unsigned int num_chars, int after_tab,
747 struct tty_struct *tty)
749 mutex_lock(&tty->echo_lock);
751 add_echo_byte(ECHO_OP_START, tty);
752 add_echo_byte(ECHO_OP_ERASE_TAB, tty);
754 /* We only need to know this modulo 8 (tab spacing) */
757 /* Set the high bit as a flag if num_chars is after a previous tab */
761 add_echo_byte(num_chars, tty);
763 mutex_unlock(&tty->echo_lock);
767 * echo_char_raw - echo a character raw
768 * @c: unicode byte to echo
769 * @tty: terminal device
771 * Echo user input back onto the screen. This must be called only when
772 * L_ECHO(tty) is true. Called from the driver receive_buf path.
774 * This variant does not treat control characters specially.
776 * Locking: echo_lock to protect the echo buffer
779 static void echo_char_raw(unsigned char c, struct tty_struct *tty)
781 mutex_lock(&tty->echo_lock);
783 if (c == ECHO_OP_START) {
784 add_echo_byte(ECHO_OP_START, tty);
785 add_echo_byte(ECHO_OP_START, tty);
787 add_echo_byte(c, tty);
790 mutex_unlock(&tty->echo_lock);
794 * echo_char - echo a character
795 * @c: unicode byte to echo
796 * @tty: terminal device
798 * Echo user input back onto the screen. This must be called only when
799 * L_ECHO(tty) is true. Called from the driver receive_buf path.
801 * This variant tags control characters to be possibly echoed as
802 * as "^X" (where X is the letter representing the control char).
804 * Locking: echo_lock to protect the echo buffer
807 static void echo_char(unsigned char c, struct tty_struct *tty)
809 mutex_lock(&tty->echo_lock);
811 if (c == ECHO_OP_START) {
812 add_echo_byte(ECHO_OP_START, tty);
813 add_echo_byte(ECHO_OP_START, tty);
815 if (iscntrl(c) && c != '\t')
816 add_echo_byte(ECHO_OP_START, tty);
817 add_echo_byte(c, tty);
820 mutex_unlock(&tty->echo_lock);
824 * finish_erasing - complete erase
825 * @tty: tty doing the erase
828 static inline void finish_erasing(struct tty_struct *tty)
831 echo_char_raw('/', tty);
837 * eraser - handle erase function
838 * @c: character input
839 * @tty: terminal device
841 * Perform erase and necessary output when an erase character is
842 * present in the stream from the driver layer. Handles the complexities
843 * of UTF-8 multibyte symbols.
845 * Locking: read_lock for tty buffers
848 static void eraser(unsigned char c, struct tty_struct *tty)
850 enum { ERASE, WERASE, KILL } kill_type;
851 int head, seen_alnums, cnt;
854 /* FIXME: locking needed ? */
855 if (tty->read_head == tty->canon_head) {
856 /* process_output('\a', tty); */ /* what do you think? */
859 if (c == ERASE_CHAR(tty))
861 else if (c == WERASE_CHAR(tty))
865 spin_lock_irqsave(&tty->read_lock, flags);
866 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
867 (N_TTY_BUF_SIZE - 1));
868 tty->read_head = tty->canon_head;
869 spin_unlock_irqrestore(&tty->read_lock, flags);
872 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
873 spin_lock_irqsave(&tty->read_lock, flags);
874 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
875 (N_TTY_BUF_SIZE - 1));
876 tty->read_head = tty->canon_head;
877 spin_unlock_irqrestore(&tty->read_lock, flags);
879 echo_char(KILL_CHAR(tty), tty);
880 /* Add a newline if ECHOK is on and ECHOKE is off. */
882 echo_char_raw('\n', tty);
889 /* FIXME: Locking ?? */
890 while (tty->read_head != tty->canon_head) {
891 head = tty->read_head;
893 /* erase a single possibly multibyte character */
895 head = (head - 1) & (N_TTY_BUF_SIZE-1);
896 c = tty->read_buf[head];
897 } while (is_continuation(c, tty) && head != tty->canon_head);
899 /* do not partially erase */
900 if (is_continuation(c, tty))
903 if (kill_type == WERASE) {
904 /* Equivalent to BSD's ALTWERASE. */
905 if (isalnum(c) || c == '_')
907 else if (seen_alnums)
910 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
911 spin_lock_irqsave(&tty->read_lock, flags);
912 tty->read_head = head;
913 tty->read_cnt -= cnt;
914 spin_unlock_irqrestore(&tty->read_lock, flags);
916 if (L_ECHOPRT(tty)) {
918 echo_char_raw('\\', tty);
921 /* if cnt > 1, output a multi-byte character */
924 head = (head+1) & (N_TTY_BUF_SIZE-1);
925 echo_char_raw(tty->read_buf[head], tty);
926 echo_move_back_col(tty);
928 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
929 echo_char(ERASE_CHAR(tty), tty);
930 } else if (c == '\t') {
931 unsigned int num_chars = 0;
933 unsigned long tail = tty->read_head;
936 * Count the columns used for characters
937 * since the start of input or after a
939 * This info is used to go back the correct
942 while (tail != tty->canon_head) {
943 tail = (tail-1) & (N_TTY_BUF_SIZE-1);
944 c = tty->read_buf[tail];
948 } else if (iscntrl(c)) {
951 } else if (!is_continuation(c, tty)) {
955 echo_erase_tab(num_chars, after_tab, tty);
957 if (iscntrl(c) && L_ECHOCTL(tty)) {
958 echo_char_raw('\b', tty);
959 echo_char_raw(' ', tty);
960 echo_char_raw('\b', tty);
962 if (!iscntrl(c) || L_ECHOCTL(tty)) {
963 echo_char_raw('\b', tty);
964 echo_char_raw(' ', tty);
965 echo_char_raw('\b', tty);
969 if (kill_type == ERASE)
972 if (tty->read_head == tty->canon_head && L_ECHO(tty))
977 * isig - handle the ISIG optio
980 * @flush: force flush
982 * Called when a signal is being sent due to terminal input. This
983 * may caus terminal flushing to take place according to the termios
984 * settings and character used. Called from the driver receive_buf
985 * path so serialized.
987 * Locking: ctrl_lock, read_lock (both via flush buffer)
990 static inline void isig(int sig, struct tty_struct *tty, int flush)
993 kill_pgrp(tty->pgrp, sig, 1);
994 if (flush || !L_NOFLSH(tty)) {
995 n_tty_flush_buffer(tty);
996 tty_driver_flush_buffer(tty);
1001 * n_tty_receive_break - handle break
1004 * An RS232 break event has been hit in the incoming bitstream. This
1005 * can cause a variety of events depending upon the termios settings.
1007 * Called from the receive_buf path so single threaded.
1010 static inline void n_tty_receive_break(struct tty_struct *tty)
1014 if (I_BRKINT(tty)) {
1015 isig(SIGINT, tty, 1);
1018 if (I_PARMRK(tty)) {
1019 put_tty_queue('\377', tty);
1020 put_tty_queue('\0', tty);
1022 put_tty_queue('\0', tty);
1023 wake_up_interruptible(&tty->read_wait);
1027 * n_tty_receive_overrun - handle overrun reporting
1030 * Data arrived faster than we could process it. While the tty
1031 * driver has flagged this the bits that were missed are gone
1034 * Called from the receive_buf path so single threaded. Does not
1035 * need locking as num_overrun and overrun_time are function
1039 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1044 if (time_before(tty->overrun_time, jiffies - HZ) ||
1045 time_after(tty->overrun_time, jiffies)) {
1046 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1049 tty->overrun_time = jiffies;
1050 tty->num_overrun = 0;
1055 * n_tty_receive_parity_error - error notifier
1056 * @tty: terminal device
1059 * Process a parity error and queue the right data to indicate
1060 * the error case if necessary. Locking as per n_tty_receive_buf.
1062 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1067 if (I_PARMRK(tty)) {
1068 put_tty_queue('\377', tty);
1069 put_tty_queue('\0', tty);
1070 put_tty_queue(c, tty);
1071 } else if (I_INPCK(tty))
1072 put_tty_queue('\0', tty);
1074 put_tty_queue(c, tty);
1075 wake_up_interruptible(&tty->read_wait);
1079 * n_tty_receive_char - perform processing
1080 * @tty: terminal device
1083 * Process an individual character of input received from the driver.
1084 * This is serialized with respect to itself by the rules for the
1088 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1090 unsigned long flags;
1094 put_tty_queue(c, tty);
1100 if (I_IUCLC(tty) && L_IEXTEN(tty))
1103 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1104 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1105 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1107 process_echoes(tty);
1112 if (c == START_CHAR(tty)) {
1114 process_echoes(tty);
1115 } else if (c == STOP_CHAR(tty))
1122 * If the previous character was LNEXT, or we know that this
1123 * character is not one of the characters that we'll have to
1124 * handle specially, do shortcut processing to speed things
1127 if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1129 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1130 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1131 /* beep if no space */
1133 process_output('\a', tty);
1137 finish_erasing(tty);
1138 /* Record the column of first canon char. */
1139 if (tty->canon_head == tty->read_head)
1140 echo_set_canon_col(tty);
1142 process_echoes(tty);
1145 put_tty_queue(c, tty);
1146 put_tty_queue(c, tty);
1151 if (c == START_CHAR(tty)) {
1153 process_echoes(tty);
1156 if (c == STOP_CHAR(tty)) {
1165 if (c == INTR_CHAR(tty))
1168 if (c == QUIT_CHAR(tty))
1171 if (c == SUSP_CHAR(tty)) {
1174 * Note that we do not use isig() here because we want
1176 * 1) flush, 2) echo, 3) signal
1178 if (!L_NOFLSH(tty)) {
1179 n_tty_flush_buffer(tty);
1180 tty_driver_flush_buffer(tty);
1186 process_echoes(tty);
1189 kill_pgrp(tty->pgrp, signal, 1);
1199 } else if (c == '\n' && I_INLCR(tty))
1203 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1204 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1206 process_echoes(tty);
1209 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1212 finish_erasing(tty);
1213 if (L_ECHOCTL(tty)) {
1214 echo_char_raw('^', tty);
1215 echo_char_raw('\b', tty);
1216 process_echoes(tty);
1221 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1223 unsigned long tail = tty->canon_head;
1225 finish_erasing(tty);
1227 echo_char_raw('\n', tty);
1228 while (tail != tty->read_head) {
1229 echo_char(tty->read_buf[tail], tty);
1230 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1232 process_echoes(tty);
1236 if (tty->read_cnt >= N_TTY_BUF_SIZE) {
1238 process_output('\a', tty);
1241 if (L_ECHO(tty) || L_ECHONL(tty)) {
1242 echo_char_raw('\n', tty);
1243 process_echoes(tty);
1245 goto handle_newline;
1247 if (c == EOF_CHAR(tty)) {
1248 if (tty->read_cnt >= N_TTY_BUF_SIZE)
1250 if (tty->canon_head != tty->read_head)
1251 set_bit(TTY_PUSH, &tty->flags);
1252 c = __DISABLED_CHAR;
1253 goto handle_newline;
1255 if ((c == EOL_CHAR(tty)) ||
1256 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1257 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1259 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1261 process_output('\a', tty);
1265 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1268 /* Record the column of first canon char. */
1269 if (tty->canon_head == tty->read_head)
1270 echo_set_canon_col(tty);
1272 process_echoes(tty);
1275 * XXX does PARMRK doubling happen for
1276 * EOL_CHAR and EOL2_CHAR?
1279 put_tty_queue(c, tty);
1282 spin_lock_irqsave(&tty->read_lock, flags);
1283 set_bit(tty->read_head, tty->read_flags);
1284 put_tty_queue_nolock(c, tty);
1285 tty->canon_head = tty->read_head;
1287 spin_unlock_irqrestore(&tty->read_lock, flags);
1288 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1289 if (waitqueue_active(&tty->read_wait))
1290 wake_up_interruptible(&tty->read_wait);
1295 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1296 if (tty->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1297 /* beep if no space */
1299 process_output('\a', tty);
1303 finish_erasing(tty);
1305 echo_char_raw('\n', tty);
1307 /* Record the column of first canon char. */
1308 if (tty->canon_head == tty->read_head)
1309 echo_set_canon_col(tty);
1312 process_echoes(tty);
1316 put_tty_queue(c, tty);
1318 put_tty_queue(c, tty);
1323 * n_tty_write_wakeup - asynchronous I/O notifier
1326 * Required for the ptys, serial driver etc. since processes
1327 * that attach themselves to the master and rely on ASYNC
1328 * IO must be woken up
1331 static void n_tty_write_wakeup(struct tty_struct *tty)
1333 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1334 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1338 * n_tty_receive_buf - data receive
1339 * @tty: terminal device
1342 * @count: characters
1344 * Called by the terminal driver when a block of characters has
1345 * been received. This function must be called from soft contexts
1346 * not from interrupt context. The driver is responsible for making
1347 * calls one at a time and in order (or using flush_to_ldisc)
1350 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1351 char *fp, int count)
1353 const unsigned char *p;
1354 char *f, flags = TTY_NORMAL;
1357 unsigned long cpuflags;
1362 if (tty->real_raw) {
1363 spin_lock_irqsave(&tty->read_lock, cpuflags);
1364 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1365 N_TTY_BUF_SIZE - tty->read_head);
1367 memcpy(tty->read_buf + tty->read_head, cp, i);
1368 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1373 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1374 N_TTY_BUF_SIZE - tty->read_head);
1376 memcpy(tty->read_buf + tty->read_head, cp, i);
1377 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1379 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1381 for (i = count, p = cp, f = fp; i; i--, p++) {
1386 n_tty_receive_char(tty, *p);
1389 n_tty_receive_break(tty);
1393 n_tty_receive_parity_error(tty, *p);
1396 n_tty_receive_overrun(tty);
1399 printk(KERN_ERR "%s: unknown flag %d\n",
1400 tty_name(tty, buf), flags);
1404 if (tty->ops->flush_chars)
1405 tty->ops->flush_chars(tty);
1408 n_tty_set_room(tty);
1410 if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
1411 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1412 if (waitqueue_active(&tty->read_wait))
1413 wake_up_interruptible(&tty->read_wait);
1417 * Check the remaining room for the input canonicalization
1418 * mode. We don't want to throttle the driver if we're in
1419 * canonical mode and don't have a newline yet!
1421 if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1425 int is_ignored(int sig)
1427 return (sigismember(¤t->blocked, sig) ||
1428 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1432 * n_tty_set_termios - termios data changed
1434 * @old: previous data
1436 * Called by the tty layer when the user changes termios flags so
1437 * that the line discipline can plan ahead. This function cannot sleep
1438 * and is protected from re-entry by the tty layer. The user is
1439 * guaranteed that this function will not be re-entered or in progress
1440 * when the ldisc is closed.
1442 * Locking: Caller holds tty->termios_mutex
1445 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1447 int canon_change = 1;
1451 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1453 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1454 tty->canon_head = tty->read_tail;
1455 tty->canon_data = 0;
1459 if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1460 wake_up_interruptible(&tty->read_wait);
1462 tty->icanon = (L_ICANON(tty) != 0);
1463 if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1466 n_tty_set_room(tty);
1469 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1470 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1471 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1473 memset(tty->process_char_map, 0, 256/8);
1475 if (I_IGNCR(tty) || I_ICRNL(tty))
1476 set_bit('\r', tty->process_char_map);
1478 set_bit('\n', tty->process_char_map);
1480 if (L_ICANON(tty)) {
1481 set_bit(ERASE_CHAR(tty), tty->process_char_map);
1482 set_bit(KILL_CHAR(tty), tty->process_char_map);
1483 set_bit(EOF_CHAR(tty), tty->process_char_map);
1484 set_bit('\n', tty->process_char_map);
1485 set_bit(EOL_CHAR(tty), tty->process_char_map);
1486 if (L_IEXTEN(tty)) {
1487 set_bit(WERASE_CHAR(tty),
1488 tty->process_char_map);
1489 set_bit(LNEXT_CHAR(tty),
1490 tty->process_char_map);
1491 set_bit(EOL2_CHAR(tty),
1492 tty->process_char_map);
1494 set_bit(REPRINT_CHAR(tty),
1495 tty->process_char_map);
1499 set_bit(START_CHAR(tty), tty->process_char_map);
1500 set_bit(STOP_CHAR(tty), tty->process_char_map);
1503 set_bit(INTR_CHAR(tty), tty->process_char_map);
1504 set_bit(QUIT_CHAR(tty), tty->process_char_map);
1505 set_bit(SUSP_CHAR(tty), tty->process_char_map);
1507 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1512 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1513 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1514 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1519 n_tty_set_room(tty);
1520 /* The termios change make the tty ready for I/O */
1521 wake_up_interruptible(&tty->write_wait);
1522 wake_up_interruptible(&tty->read_wait);
1526 * n_tty_close - close the ldisc for this tty
1529 * Called from the terminal layer when this line discipline is
1530 * being shut down, either because of a close or becsuse of a
1531 * discipline change. The function will not be called while other
1532 * ldisc methods are in progress.
1535 static void n_tty_close(struct tty_struct *tty)
1537 n_tty_flush_buffer(tty);
1538 if (tty->read_buf) {
1539 kfree(tty->read_buf);
1540 tty->read_buf = NULL;
1542 if (tty->echo_buf) {
1543 kfree(tty->echo_buf);
1544 tty->echo_buf = NULL;
1549 * n_tty_open - open an ldisc
1550 * @tty: terminal to open
1552 * Called when this line discipline is being attached to the
1553 * terminal device. Can sleep. Called serialized so that no
1554 * other events will occur in parallel. No further open will occur
1558 static int n_tty_open(struct tty_struct *tty)
1563 /* These are ugly. Currently a malloc failure here can panic */
1564 if (!tty->read_buf) {
1565 tty->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1569 if (!tty->echo_buf) {
1570 tty->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1575 reset_buffer_flags(tty);
1577 n_tty_set_termios(tty, NULL);
1578 tty->minimum_to_wake = 1;
1583 static inline int input_available_p(struct tty_struct *tty, int amt)
1585 tty_flush_to_ldisc(tty);
1587 if (tty->canon_data)
1589 } else if (tty->read_cnt >= (amt ? amt : 1))
1596 * copy_from_read_buf - copy read data directly
1597 * @tty: terminal device
1601 * Helper function to speed up n_tty_read. It is only called when
1602 * ICANON is off; it copies characters straight from the tty queue to
1603 * user space directly. It can be profitably called twice; once to
1604 * drain the space from the tail pointer to the (physical) end of the
1605 * buffer, and once to drain the space from the (physical) beginning of
1606 * the buffer to head pointer.
1608 * Called under the tty->atomic_read_lock sem
1612 static int copy_from_read_buf(struct tty_struct *tty,
1613 unsigned char __user **b,
1619 unsigned long flags;
1622 spin_lock_irqsave(&tty->read_lock, flags);
1623 n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1625 spin_unlock_irqrestore(&tty->read_lock, flags);
1627 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1629 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1630 spin_lock_irqsave(&tty->read_lock, flags);
1631 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1633 spin_unlock_irqrestore(&tty->read_lock, flags);
1640 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1644 * job_control - check job control
1646 * @file: file handle
1648 * Perform job control management checks on this file/tty descriptor
1649 * and if appropriate send any needed signals and return a negative
1650 * error code if action should be taken.
1653 * Locking: None - redirected write test is safe, testing
1654 * current->signal should possibly lock current->sighand
1658 static int job_control(struct tty_struct *tty, struct file *file)
1660 /* Job control check -- must be done at start and after
1661 every sleep (POSIX.1 7.1.1.4). */
1662 /* NOTE: not yet done after every sleep pending a thorough
1663 check of the logic of this change. -- jlc */
1664 /* don't stop on /dev/console */
1665 if (file->f_op->write != redirected_tty_write &&
1666 current->signal->tty == tty) {
1668 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1669 else if (task_pgrp(current) != tty->pgrp) {
1670 if (is_ignored(SIGTTIN) ||
1671 is_current_pgrp_orphaned())
1673 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1674 set_thread_flag(TIF_SIGPENDING);
1675 return -ERESTARTSYS;
1683 * n_tty_read - read function for tty
1685 * @file: file object
1686 * @buf: userspace buffer pointer
1689 * Perform reads for the line discipline. We are guaranteed that the
1690 * line discipline will not be closed under us but we may get multiple
1691 * parallel readers and must handle this ourselves. We may also get
1692 * a hangup. Always called in user context, may sleep.
1694 * This code must be sure never to sleep through a hangup.
1697 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1698 unsigned char __user *buf, size_t nr)
1700 unsigned char __user *b = buf;
1701 DECLARE_WAITQUEUE(wait, current);
1707 unsigned long flags;
1712 BUG_ON(!tty->read_buf);
1714 c = job_control(tty, file);
1719 timeout = MAX_SCHEDULE_TIMEOUT;
1721 time = (HZ / 10) * TIME_CHAR(tty);
1722 minimum = MIN_CHAR(tty);
1725 tty->minimum_to_wake = 1;
1726 else if (!waitqueue_active(&tty->read_wait) ||
1727 (tty->minimum_to_wake > minimum))
1728 tty->minimum_to_wake = minimum;
1735 tty->minimum_to_wake = minimum = 1;
1740 * Internal serialization of reads.
1742 if (file->f_flags & O_NONBLOCK) {
1743 if (!mutex_trylock(&tty->atomic_read_lock))
1746 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1747 return -ERESTARTSYS;
1749 packet = tty->packet;
1751 add_wait_queue(&tty->read_wait, &wait);
1753 /* First test for status change. */
1754 if (packet && tty->link->ctrl_status) {
1758 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1759 cs = tty->link->ctrl_status;
1760 tty->link->ctrl_status = 0;
1761 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1762 if (tty_put_user(tty, cs, b++)) {
1770 /* This statement must be first before checking for input
1771 so that any interrupt will set the state back to
1773 set_current_state(TASK_INTERRUPTIBLE);
1775 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1776 ((minimum - (b - buf)) >= 1))
1777 tty->minimum_to_wake = (minimum - (b - buf));
1779 if (!input_available_p(tty, 0)) {
1780 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1784 if (tty_hung_up_p(file))
1788 if (file->f_flags & O_NONBLOCK) {
1792 if (signal_pending(current)) {
1793 retval = -ERESTARTSYS;
1796 /* FIXME: does n_tty_set_room need locking ? */
1797 n_tty_set_room(tty);
1798 timeout = schedule_timeout(timeout);
1801 __set_current_state(TASK_RUNNING);
1803 /* Deal with packet mode. */
1804 if (packet && b == buf) {
1805 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1814 /* N.B. avoid overrun if nr == 0 */
1815 while (nr && tty->read_cnt) {
1818 eol = test_and_clear_bit(tty->read_tail,
1820 c = tty->read_buf[tty->read_tail];
1821 spin_lock_irqsave(&tty->read_lock, flags);
1822 tty->read_tail = ((tty->read_tail+1) &
1823 (N_TTY_BUF_SIZE-1));
1826 /* this test should be redundant:
1827 * we shouldn't be reading data if
1830 if (--tty->canon_data < 0)
1831 tty->canon_data = 0;
1833 spin_unlock_irqrestore(&tty->read_lock, flags);
1835 if (!eol || (c != __DISABLED_CHAR)) {
1836 if (tty_put_user(tty, c, b++)) {
1844 tty_audit_push(tty);
1852 /* The copy function takes the read lock and handles
1853 locking internally for this case */
1854 uncopied = copy_from_read_buf(tty, &b, &nr);
1855 uncopied += copy_from_read_buf(tty, &b, &nr);
1862 /* If there is enough space in the read buffer now, let the
1863 * low-level driver know. We use n_tty_chars_in_buffer() to
1864 * check the buffer, as it now knows about canonical mode.
1865 * Otherwise, if the driver is throttled and the line is
1866 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1867 * we won't get any more characters.
1869 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1870 n_tty_set_room(tty);
1871 check_unthrottle(tty);
1874 if (b - buf >= minimum)
1879 mutex_unlock(&tty->atomic_read_lock);
1880 remove_wait_queue(&tty->read_wait, &wait);
1882 if (!waitqueue_active(&tty->read_wait))
1883 tty->minimum_to_wake = minimum;
1885 __set_current_state(TASK_RUNNING);
1890 clear_bit(TTY_PUSH, &tty->flags);
1891 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1894 n_tty_set_room(tty);
1899 * n_tty_write - write function for tty
1901 * @file: file object
1902 * @buf: userspace buffer pointer
1905 * Write function of the terminal device. This is serialized with
1906 * respect to other write callers but not to termios changes, reads
1907 * and other such events. Since the receive code will echo characters,
1908 * thus calling driver write methods, the output_lock is used in
1909 * the output processing functions called here as well as in the
1910 * echo processing function to protect the column state and space
1911 * left in the buffer.
1913 * This code must be sure never to sleep through a hangup.
1915 * Locking: output_lock to protect column state and space left
1916 * (note that the process_output*() functions take this
1920 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1921 const unsigned char *buf, size_t nr)
1923 const unsigned char *b = buf;
1924 DECLARE_WAITQUEUE(wait, current);
1928 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1929 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1930 retval = tty_check_change(tty);
1935 /* Write out any echoed characters that are still pending */
1936 process_echoes(tty);
1938 add_wait_queue(&tty->write_wait, &wait);
1940 set_current_state(TASK_INTERRUPTIBLE);
1941 if (signal_pending(current)) {
1942 retval = -ERESTARTSYS;
1945 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1949 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1951 ssize_t num = process_output_block(tty, b, nr);
1963 if (process_output(c, tty) < 0)
1967 if (tty->ops->flush_chars)
1968 tty->ops->flush_chars(tty);
1971 c = tty->ops->write(tty, b, nr);
1984 if (file->f_flags & O_NONBLOCK) {
1991 __set_current_state(TASK_RUNNING);
1992 remove_wait_queue(&tty->write_wait, &wait);
1993 if (b - buf != nr && tty->fasync)
1994 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
1995 return (b - buf) ? b - buf : retval;
1999 * n_tty_poll - poll method for N_TTY
2000 * @tty: terminal device
2001 * @file: file accessing it
2004 * Called when the line discipline is asked to poll() for data or
2005 * for special events. This code is not serialized with respect to
2006 * other events save open/close.
2008 * This code must be sure never to sleep through a hangup.
2009 * Called without the kernel lock held - fine
2012 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2015 unsigned int mask = 0;
2017 poll_wait(file, &tty->read_wait, wait);
2018 poll_wait(file, &tty->write_wait, wait);
2019 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2020 mask |= POLLIN | POLLRDNORM;
2021 if (tty->packet && tty->link->ctrl_status)
2022 mask |= POLLPRI | POLLIN | POLLRDNORM;
2023 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2025 if (tty_hung_up_p(file))
2027 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2028 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2029 tty->minimum_to_wake = MIN_CHAR(tty);
2031 tty->minimum_to_wake = 1;
2033 if (tty->ops->write && !tty_is_writelocked(tty) &&
2034 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2035 tty_write_room(tty) > 0)
2036 mask |= POLLOUT | POLLWRNORM;
2040 static unsigned long inq_canon(struct tty_struct *tty)
2044 if (!tty->canon_data)
2046 head = tty->canon_head;
2047 tail = tty->read_tail;
2048 nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2049 /* Skip EOF-chars.. */
2050 while (head != tail) {
2051 if (test_bit(tail, tty->read_flags) &&
2052 tty->read_buf[tail] == __DISABLED_CHAR)
2054 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2059 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2060 unsigned int cmd, unsigned long arg)
2066 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2068 /* FIXME: Locking */
2069 retval = tty->read_cnt;
2071 retval = inq_canon(tty);
2072 return put_user(retval, (unsigned int __user *) arg);
2074 return n_tty_ioctl_helper(tty, file, cmd, arg);
2078 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2079 .magic = TTY_LDISC_MAGIC,
2082 .close = n_tty_close,
2083 .flush_buffer = n_tty_flush_buffer,
2084 .chars_in_buffer = n_tty_chars_in_buffer,
2086 .write = n_tty_write,
2087 .ioctl = n_tty_ioctl,
2088 .set_termios = n_tty_set_termios,
2090 .receive_buf = n_tty_receive_buf,
2091 .write_wakeup = n_tty_write_wakeup