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>
51 #include <asm/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 unsigned char *alloc_buf(void)
78 gfp_t prio = in_interrupt() ? GFP_ATOMIC : GFP_KERNEL;
80 if (PAGE_SIZE != N_TTY_BUF_SIZE)
81 return kmalloc(N_TTY_BUF_SIZE, prio);
83 return (unsigned char *)__get_free_page(prio);
86 static inline void free_buf(unsigned char *buf)
88 if (PAGE_SIZE != N_TTY_BUF_SIZE)
91 free_page((unsigned long) buf);
94 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
95 unsigned char __user *ptr)
97 tty_audit_add_data(tty, &x, 1);
98 return put_user(x, ptr);
102 * n_tty_set__room - receive space
105 * Called by the driver to find out how much data it is
106 * permitted to feed to the line discipline without any being lost
107 * and thus to manage flow control. Not serialized. Answers for the
111 static void n_tty_set_room(struct tty_struct *tty)
113 /* tty->read_cnt is not read locked ? */
114 int left = N_TTY_BUF_SIZE - tty->read_cnt - 1;
117 * If we are doing input canonicalization, and there are no
118 * pending newlines, let characters through without limit, so
119 * that erase characters will be handled. Other excess
120 * characters will be beeped.
123 left = tty->icanon && !tty->canon_data;
124 tty->receive_room = left;
127 static void put_tty_queue_nolock(unsigned char c, struct tty_struct *tty)
129 if (tty->read_cnt < N_TTY_BUF_SIZE) {
130 tty->read_buf[tty->read_head] = c;
131 tty->read_head = (tty->read_head + 1) & (N_TTY_BUF_SIZE-1);
137 * put_tty_queue - add character to tty
141 * Add a character to the tty read_buf queue. This is done under the
142 * read_lock to serialize character addition and also to protect us
143 * against parallel reads or flushes
146 static void put_tty_queue(unsigned char c, struct tty_struct *tty)
150 * The problem of stomping on the buffers ends here.
151 * Why didn't anyone see this one coming? --AJK
153 spin_lock_irqsave(&tty->read_lock, flags);
154 put_tty_queue_nolock(c, tty);
155 spin_unlock_irqrestore(&tty->read_lock, flags);
159 * check_unthrottle - allow new receive data
162 * Check whether to call the driver unthrottle functions
164 * Can sleep, may be called under the atomic_read_lock mutex but
165 * this is not guaranteed.
167 static void check_unthrottle(struct tty_struct *tty)
174 * reset_buffer_flags - reset buffer state
175 * @tty: terminal to reset
177 * Reset the read buffer counters, clear the flags,
178 * and make sure the driver is unthrottled. Called
179 * from n_tty_open() and n_tty_flush_buffer().
181 * Locking: tty_read_lock for read fields.
184 static void reset_buffer_flags(struct tty_struct *tty)
188 spin_lock_irqsave(&tty->read_lock, flags);
189 tty->read_head = tty->read_tail = tty->read_cnt = 0;
190 spin_unlock_irqrestore(&tty->read_lock, flags);
192 mutex_lock(&tty->echo_lock);
193 tty->echo_pos = tty->echo_cnt = tty->echo_overrun = 0;
194 mutex_unlock(&tty->echo_lock);
196 tty->canon_head = tty->canon_data = tty->erasing = 0;
197 memset(&tty->read_flags, 0, sizeof tty->read_flags);
199 check_unthrottle(tty);
203 * n_tty_flush_buffer - clean input queue
204 * @tty: terminal device
206 * Flush the input buffer. Called when the line discipline is
207 * being closed, when the tty layer wants the buffer flushed (eg
208 * at hangup) or when the N_TTY line discipline internally has to
209 * clean the pending queue (for example some signals).
211 * Locking: ctrl_lock, read_lock.
214 static void n_tty_flush_buffer(struct tty_struct *tty)
217 /* clear everything and unthrottle the driver */
218 reset_buffer_flags(tty);
223 spin_lock_irqsave(&tty->ctrl_lock, flags);
224 if (tty->link->packet) {
225 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
226 wake_up_interruptible(&tty->link->read_wait);
228 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
232 * n_tty_chars_in_buffer - report available bytes
235 * Report the number of characters buffered to be delivered to user
236 * at this instant in time.
241 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
246 spin_lock_irqsave(&tty->read_lock, flags);
249 } else if (tty->canon_data) {
250 n = (tty->canon_head > tty->read_tail) ?
251 tty->canon_head - tty->read_tail :
252 tty->canon_head + (N_TTY_BUF_SIZE - tty->read_tail);
254 spin_unlock_irqrestore(&tty->read_lock, flags);
259 * is_utf8_continuation - utf8 multibyte check
262 * Returns true if the utf8 character 'c' is a multibyte continuation
263 * character. We use this to correctly compute the on screen size
264 * of the character when printing
267 static inline int is_utf8_continuation(unsigned char c)
269 return (c & 0xc0) == 0x80;
273 * is_continuation - multibyte check
276 * Returns true if the utf8 character 'c' is a multibyte continuation
277 * character and the terminal is in unicode mode.
280 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
282 return I_IUTF8(tty) && is_utf8_continuation(c);
286 * do_output_char - output one character
287 * @c: character (or partial unicode symbol)
288 * @tty: terminal device
289 * @space: space available in tty driver write buffer
291 * This is a helper function that handles one output character
292 * (including special characters like TAB, CR, LF, etc.),
293 * putting the results in the tty driver's write buffer.
295 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
296 * and NLDLY. They simply aren't relevant in the world today.
297 * If you ever need them, add them here.
299 * Returns the number of bytes of buffer space used or -1 if
302 * Locking: should be called under the output_lock to protect
303 * the column state and space left in the buffer
306 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
320 tty->canon_column = tty->column = 0;
321 tty_put_char(tty, '\r');
322 tty_put_char(tty, c);
325 tty->canon_column = tty->column;
328 if (O_ONOCR(tty) && tty->column == 0)
333 tty->canon_column = tty->column = 0;
336 tty->canon_column = tty->column = 0;
339 spaces = 8 - (tty->column & 7);
340 if (O_TABDLY(tty) == XTABS) {
343 tty->column += spaces;
344 tty->ops->write(tty, " ", spaces);
347 tty->column += spaces;
356 if (!iscntrl(c) && !is_continuation(c, tty))
361 tty_put_char(tty, c);
366 * process_output - output post processor
367 * @c: character (or partial unicode symbol)
368 * @tty: terminal device
370 * Perform OPOST processing. Returns -1 when the output device is
371 * full and the character must be retried.
373 * Locking: output_lock to protect column state and space left
374 * (also, this is called from n_tty_write under the
375 * tty layer write lock)
378 static int process_output(unsigned char c, struct tty_struct *tty)
382 mutex_lock(&tty->output_lock);
384 space = tty_write_room(tty);
385 retval = do_output_char(c, tty, space);
387 mutex_unlock(&tty->output_lock);
395 * process_output_block - block post processor
396 * @tty: terminal device
397 * @inbuf: user buffer
398 * @nr: number of bytes
400 * This path is used to speed up block console writes, among other
401 * things when processing blocks of output data. It handles only
402 * the simple cases normally found and helps to generate blocks of
403 * symbols for the console driver and thus improve performance.
405 * Locking: output_lock to protect column state and space left
406 * (also, this is called from n_tty_write under the
407 * tty layer write lock)
410 static ssize_t process_output_block(struct tty_struct *tty,
411 const unsigned char *buf, unsigned int nr)
415 const unsigned char *cp;
417 mutex_lock(&tty->output_lock);
419 space = tty_write_room(tty);
422 mutex_unlock(&tty->output_lock);
428 for (i = 0, cp = buf; i < nr; i++, cp++) {
435 tty->canon_column = tty->column;
438 if (O_ONOCR(tty) && tty->column == 0)
442 tty->canon_column = tty->column = 0;
459 i = tty->ops->write(tty, buf, i);
461 mutex_unlock(&tty->output_lock);
466 * process_echoes - write pending echo characters
467 * @tty: terminal device
469 * Write previously buffered echo (and other ldisc-generated)
470 * characters to the tty.
472 * Characters generated by the ldisc (including echoes) need to
473 * be buffered because the driver's write buffer can fill during
474 * heavy program output. Echoing straight to the driver will
475 * often fail under these conditions, causing lost characters and
476 * resulting mismatches of ldisc state information.
478 * Since the ldisc state must represent the characters actually sent
479 * to the driver at the time of the write, operations like certain
480 * changes in column state are also saved in the buffer and executed
483 * A circular fifo buffer is used so that the most recent characters
484 * are prioritized. Also, when control characters are echoed with a
485 * prefixed "^", the pair is treated atomically and thus not separated.
487 * Locking: output_lock to protect column state and space left,
488 * echo_lock to protect the echo buffer
491 static void process_echoes(struct tty_struct *tty)
495 unsigned char *cp, *buf_end;
500 mutex_lock(&tty->output_lock);
501 mutex_lock(&tty->echo_lock);
503 space = tty_write_room(tty);
505 buf_end = tty->echo_buf + N_TTY_BUF_SIZE;
506 cp = tty->echo_buf + tty->echo_pos;
510 if (c == ECHO_OP_START) {
513 int no_space_left = 0;
516 * If the buffer byte is the start of a multi-byte
517 * operation, get the next byte, which is either the
518 * op code or a control character value.
522 opp -= N_TTY_BUF_SIZE;
526 unsigned int num_chars, num_bs;
528 case ECHO_OP_ERASE_TAB:
529 if (++opp == buf_end)
530 opp -= N_TTY_BUF_SIZE;
534 * Determine how many columns to go back
535 * in order to erase the tab.
536 * This depends on the number of columns
537 * used by other characters within the tab
538 * area. If this (modulo 8) count is from
539 * the start of input rather than from a
540 * previous tab, we offset by canon column.
541 * Otherwise, tab spacing is normal.
543 if (!(num_chars & 0x80))
544 num_chars += tty->canon_column;
545 num_bs = 8 - (num_chars & 7);
547 if (num_bs > space) {
553 tty_put_char(tty, '\b');
561 case ECHO_OP_SET_CANON_COL:
562 tty->canon_column = tty->column;
567 case ECHO_OP_MOVE_BACK_COL:
575 /* This is an escaped echo op start code */
580 tty_put_char(tty, ECHO_OP_START);
589 if (L_ECHOCTL(tty)) {
591 * Ensure there is enough space
592 * for the whole ctrl pair.
598 tty_put_char(tty, '^');
599 tty_put_char(tty, op ^ 0100);
607 tty_put_char(tty, op);
612 * If above falls through, this was an
624 if ((retval = do_output_char(c, tty, space)) < 0)
631 /* When end of circular buffer reached, wrap around */
633 cp -= N_TTY_BUF_SIZE;
639 tty->echo_overrun = 0;
641 int num_processed = tty->echo_cnt - nr;
642 tty->echo_pos += num_processed;
643 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
645 if (num_processed > 0)
646 tty->echo_overrun = 0;
649 mutex_unlock(&tty->echo_lock);
650 mutex_unlock(&tty->output_lock);
652 if (tty->ops->flush_chars)
653 tty->ops->flush_chars(tty);
657 * add_echo_byte - add a byte to the echo buffer
658 * @c: unicode byte to echo
659 * @tty: terminal device
661 * Add a character or operation byte to the echo buffer.
663 * Should be called under the echo lock to protect the echo buffer.
666 static void add_echo_byte(unsigned char c, struct tty_struct *tty)
670 if (tty->echo_cnt == N_TTY_BUF_SIZE) {
671 /* Circular buffer is already at capacity */
672 new_byte_pos = tty->echo_pos;
675 * Since the buffer start position needs to be advanced,
676 * be sure to step by a whole operation byte group.
678 if (tty->echo_buf[tty->echo_pos] == ECHO_OP_START)
680 if (tty->echo_buf[(tty->echo_pos + 1) &
681 (N_TTY_BUF_SIZE - 1)] ==
692 tty->echo_pos &= N_TTY_BUF_SIZE - 1;
694 tty->echo_overrun = 1;
696 new_byte_pos = tty->echo_pos + tty->echo_cnt;
697 new_byte_pos &= N_TTY_BUF_SIZE - 1;
701 tty->echo_buf[new_byte_pos] = c;
705 * echo_move_back_col - add operation to move back a column
706 * @tty: terminal device
708 * Add an operation to the echo buffer to move back one column.
710 * Locking: echo_lock to protect the echo buffer
713 static void echo_move_back_col(struct tty_struct *tty)
715 mutex_lock(&tty->echo_lock);
717 add_echo_byte(ECHO_OP_START, tty);
718 add_echo_byte(ECHO_OP_MOVE_BACK_COL, tty);
720 mutex_unlock(&tty->echo_lock);
724 * echo_set_canon_col - add operation to set the canon column
725 * @tty: terminal device
727 * Add an operation to the echo buffer to set the canon column
728 * to the current column.
730 * Locking: echo_lock to protect the echo buffer
733 static void echo_set_canon_col(struct tty_struct *tty)
735 mutex_lock(&tty->echo_lock);
737 add_echo_byte(ECHO_OP_START, tty);
738 add_echo_byte(ECHO_OP_SET_CANON_COL, tty);
740 mutex_unlock(&tty->echo_lock);
744 * echo_erase_tab - add operation to erase a tab
745 * @num_chars: number of character columns already used
746 * @after_tab: true if num_chars starts after a previous tab
747 * @tty: terminal device
749 * Add an operation to the echo buffer to erase a tab.
751 * Called by the eraser function, which knows how many character
752 * columns have been used since either a previous tab or the start
753 * of input. This information will be used later, along with
754 * canon column (if applicable), to go back the correct number
757 * Locking: echo_lock to protect the echo buffer
760 static void echo_erase_tab(unsigned int num_chars, int after_tab,
761 struct tty_struct *tty)
763 mutex_lock(&tty->echo_lock);
765 add_echo_byte(ECHO_OP_START, tty);
766 add_echo_byte(ECHO_OP_ERASE_TAB, tty);
768 /* We only need to know this modulo 8 (tab spacing) */
771 /* Set the high bit as a flag if num_chars is after a previous tab */
775 add_echo_byte(num_chars, tty);
777 mutex_unlock(&tty->echo_lock);
781 * echo_char_raw - echo a character raw
782 * @c: unicode byte to echo
783 * @tty: terminal device
785 * Echo user input back onto the screen. This must be called only when
786 * L_ECHO(tty) is true. Called from the driver receive_buf path.
788 * This variant does not treat control characters specially.
790 * Locking: echo_lock to protect the echo buffer
793 static void echo_char_raw(unsigned char c, struct tty_struct *tty)
795 mutex_lock(&tty->echo_lock);
797 if (c == ECHO_OP_START) {
798 add_echo_byte(ECHO_OP_START, tty);
799 add_echo_byte(ECHO_OP_START, tty);
801 add_echo_byte(c, tty);
804 mutex_unlock(&tty->echo_lock);
808 * echo_char - echo a character
809 * @c: unicode byte to echo
810 * @tty: terminal device
812 * Echo user input back onto the screen. This must be called only when
813 * L_ECHO(tty) is true. Called from the driver receive_buf path.
815 * This variant tags control characters to be possibly echoed as
816 * as "^X" (where X is the letter representing the control char).
818 * Locking: echo_lock to protect the echo buffer
821 static void echo_char(unsigned char c, struct tty_struct *tty)
823 mutex_lock(&tty->echo_lock);
825 if (c == ECHO_OP_START) {
826 add_echo_byte(ECHO_OP_START, tty);
827 add_echo_byte(ECHO_OP_START, tty);
829 if (iscntrl(c) && c != '\t')
830 add_echo_byte(ECHO_OP_START, tty);
831 add_echo_byte(c, tty);
834 mutex_unlock(&tty->echo_lock);
838 * finish_erasing - complete erase
839 * @tty: tty doing the erase
842 static inline void finish_erasing(struct tty_struct *tty)
845 echo_char_raw('/', tty);
851 * eraser - handle erase function
852 * @c: character input
853 * @tty: terminal device
855 * Perform erase and necessary output when an erase character is
856 * present in the stream from the driver layer. Handles the complexities
857 * of UTF-8 multibyte symbols.
859 * Locking: read_lock for tty buffers
862 static void eraser(unsigned char c, struct tty_struct *tty)
864 enum { ERASE, WERASE, KILL } kill_type;
865 int head, seen_alnums, cnt;
868 /* FIXME: locking needed ? */
869 if (tty->read_head == tty->canon_head) {
870 /* echo_char_raw('\a', tty); */ /* what do you think? */
873 if (c == ERASE_CHAR(tty))
875 else if (c == WERASE_CHAR(tty))
879 spin_lock_irqsave(&tty->read_lock, flags);
880 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
881 (N_TTY_BUF_SIZE - 1));
882 tty->read_head = tty->canon_head;
883 spin_unlock_irqrestore(&tty->read_lock, flags);
886 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
887 spin_lock_irqsave(&tty->read_lock, flags);
888 tty->read_cnt -= ((tty->read_head - tty->canon_head) &
889 (N_TTY_BUF_SIZE - 1));
890 tty->read_head = tty->canon_head;
891 spin_unlock_irqrestore(&tty->read_lock, flags);
893 echo_char(KILL_CHAR(tty), tty);
894 /* Add a newline if ECHOK is on and ECHOKE is off. */
896 echo_char_raw('\n', tty);
903 /* FIXME: Locking ?? */
904 while (tty->read_head != tty->canon_head) {
905 head = tty->read_head;
907 /* erase a single possibly multibyte character */
909 head = (head - 1) & (N_TTY_BUF_SIZE-1);
910 c = tty->read_buf[head];
911 } while (is_continuation(c, tty) && head != tty->canon_head);
913 /* do not partially erase */
914 if (is_continuation(c, tty))
917 if (kill_type == WERASE) {
918 /* Equivalent to BSD's ALTWERASE. */
919 if (isalnum(c) || c == '_')
921 else if (seen_alnums)
924 cnt = (tty->read_head - head) & (N_TTY_BUF_SIZE-1);
925 spin_lock_irqsave(&tty->read_lock, flags);
926 tty->read_head = head;
927 tty->read_cnt -= cnt;
928 spin_unlock_irqrestore(&tty->read_lock, flags);
930 if (L_ECHOPRT(tty)) {
932 echo_char_raw('\\', tty);
935 /* if cnt > 1, output a multi-byte character */
938 head = (head+1) & (N_TTY_BUF_SIZE-1);
939 echo_char_raw(tty->read_buf[head], tty);
940 echo_move_back_col(tty);
942 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
943 echo_char(ERASE_CHAR(tty), tty);
944 } else if (c == '\t') {
945 unsigned int num_chars = 0;
947 unsigned long tail = tty->read_head;
950 * Count the columns used for characters
951 * since the start of input or after a
953 * This info is used to go back the correct
956 while (tail != tty->canon_head) {
957 tail = (tail-1) & (N_TTY_BUF_SIZE-1);
958 c = tty->read_buf[tail];
963 else if (iscntrl(c)) {
966 } else if (!is_continuation(c, tty)) {
970 echo_erase_tab(num_chars, after_tab, tty);
972 if (iscntrl(c) && L_ECHOCTL(tty)) {
973 echo_char_raw('\b', tty);
974 echo_char_raw(' ', tty);
975 echo_char_raw('\b', tty);
977 if (!iscntrl(c) || L_ECHOCTL(tty)) {
978 echo_char_raw('\b', tty);
979 echo_char_raw(' ', tty);
980 echo_char_raw('\b', tty);
984 if (kill_type == ERASE)
987 if (tty->read_head == tty->canon_head && L_ECHO(tty))
992 * isig - handle the ISIG optio
995 * @flush: force flush
997 * Called when a signal is being sent due to terminal input. This
998 * may caus terminal flushing to take place according to the termios
999 * settings and character used. Called from the driver receive_buf
1000 * path so serialized.
1002 * Locking: ctrl_lock, read_lock (both via flush buffer)
1005 static inline void isig(int sig, struct tty_struct *tty, int flush)
1008 kill_pgrp(tty->pgrp, sig, 1);
1009 if (flush || !L_NOFLSH(tty)) {
1010 n_tty_flush_buffer(tty);
1011 tty_driver_flush_buffer(tty);
1016 * n_tty_receive_break - handle break
1019 * An RS232 break event has been hit in the incoming bitstream. This
1020 * can cause a variety of events depending upon the termios settings.
1022 * Called from the receive_buf path so single threaded.
1025 static inline void n_tty_receive_break(struct tty_struct *tty)
1029 if (I_BRKINT(tty)) {
1030 isig(SIGINT, tty, 1);
1033 if (I_PARMRK(tty)) {
1034 put_tty_queue('\377', tty);
1035 put_tty_queue('\0', tty);
1037 put_tty_queue('\0', tty);
1038 wake_up_interruptible(&tty->read_wait);
1042 * n_tty_receive_overrun - handle overrun reporting
1045 * Data arrived faster than we could process it. While the tty
1046 * driver has flagged this the bits that were missed are gone
1049 * Called from the receive_buf path so single threaded. Does not
1050 * need locking as num_overrun and overrun_time are function
1054 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1059 if (time_before(tty->overrun_time, jiffies - HZ) ||
1060 time_after(tty->overrun_time, jiffies)) {
1061 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1064 tty->overrun_time = jiffies;
1065 tty->num_overrun = 0;
1070 * n_tty_receive_parity_error - error notifier
1071 * @tty: terminal device
1074 * Process a parity error and queue the right data to indicate
1075 * the error case if necessary. Locking as per n_tty_receive_buf.
1077 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1082 if (I_PARMRK(tty)) {
1083 put_tty_queue('\377', tty);
1084 put_tty_queue('\0', tty);
1085 put_tty_queue(c, tty);
1086 } else if (I_INPCK(tty))
1087 put_tty_queue('\0', tty);
1089 put_tty_queue(c, tty);
1090 wake_up_interruptible(&tty->read_wait);
1094 * n_tty_receive_char - perform processing
1095 * @tty: terminal device
1098 * Process an individual character of input received from the driver.
1099 * This is serialized with respect to itself by the rules for the
1103 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1105 unsigned long flags;
1108 put_tty_queue(c, tty);
1114 if (I_IUCLC(tty) && L_IEXTEN(tty))
1117 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1118 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1119 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1121 process_echoes(tty);
1126 if (c == START_CHAR(tty)) {
1128 process_echoes(tty);
1130 else if (c == STOP_CHAR(tty))
1137 * If the previous character was LNEXT, or we know that this
1138 * character is not one of the characters that we'll have to
1139 * handle specially, do shortcut processing to speed things
1142 if (!test_bit(c, tty->process_char_map) || tty->lnext) {
1145 finish_erasing(tty);
1146 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
1147 /* beep if no space */
1148 echo_char_raw('\a', tty);
1149 process_echoes(tty);
1152 /* Record the column of first canon char. */
1153 if (tty->canon_head == tty->read_head)
1154 echo_set_canon_col(tty);
1156 process_echoes(tty);
1158 if (I_PARMRK(tty) && c == (unsigned char) '\377')
1159 put_tty_queue(c, tty);
1160 put_tty_queue(c, tty);
1165 if (c == START_CHAR(tty)) {
1167 process_echoes(tty);
1170 if (c == STOP_CHAR(tty)) {
1179 if (c == INTR_CHAR(tty))
1182 if (c == QUIT_CHAR(tty))
1185 if (c == SUSP_CHAR(tty)) {
1188 * Note that we do not use isig() here because we want
1190 * 1) flush, 2) echo, 3) signal
1192 if (!L_NOFLSH(tty)) {
1193 n_tty_flush_buffer(tty);
1194 tty_driver_flush_buffer(tty);
1200 process_echoes(tty);
1203 kill_pgrp(tty->pgrp, signal, 1);
1213 } else if (c == '\n' && I_INLCR(tty))
1217 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1218 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1220 process_echoes(tty);
1223 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1226 finish_erasing(tty);
1227 if (L_ECHOCTL(tty)) {
1228 echo_char_raw('^', tty);
1229 echo_char_raw('\b', tty);
1230 process_echoes(tty);
1235 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1237 unsigned long tail = tty->canon_head;
1239 finish_erasing(tty);
1241 echo_char_raw('\n', tty);
1242 while (tail != tty->read_head) {
1243 echo_char(tty->read_buf[tail], tty);
1244 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1246 process_echoes(tty);
1250 if (L_ECHO(tty) || L_ECHONL(tty)) {
1251 if (tty->read_cnt >= N_TTY_BUF_SIZE-1)
1252 echo_char_raw('\a', tty);
1253 echo_char_raw('\n', tty);
1254 process_echoes(tty);
1256 goto handle_newline;
1258 if (c == EOF_CHAR(tty)) {
1259 if (tty->canon_head != tty->read_head)
1260 set_bit(TTY_PUSH, &tty->flags);
1261 c = __DISABLED_CHAR;
1262 goto handle_newline;
1264 if ((c == EOL_CHAR(tty)) ||
1265 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1267 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1270 if (tty->read_cnt >= N_TTY_BUF_SIZE-1)
1271 echo_char_raw('\a', tty);
1272 /* Record the column of first canon char. */
1273 if (tty->canon_head == tty->read_head)
1274 echo_set_canon_col(tty);
1276 process_echoes(tty);
1279 * XXX does PARMRK doubling happen for
1280 * EOL_CHAR and EOL2_CHAR?
1282 if (I_PARMRK(tty) && c == (unsigned char) '\377')
1283 put_tty_queue(c, tty);
1286 spin_lock_irqsave(&tty->read_lock, flags);
1287 set_bit(tty->read_head, tty->read_flags);
1288 put_tty_queue_nolock(c, tty);
1289 tty->canon_head = tty->read_head;
1291 spin_unlock_irqrestore(&tty->read_lock, flags);
1292 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1293 if (waitqueue_active(&tty->read_wait))
1294 wake_up_interruptible(&tty->read_wait);
1300 finish_erasing(tty);
1301 if (tty->read_cnt >= N_TTY_BUF_SIZE-1) {
1302 /* beep if no space */
1303 echo_char_raw('\a', tty);
1304 process_echoes(tty);
1308 echo_char_raw('\n', tty);
1310 /* Record the column of first canon char. */
1311 if (tty->canon_head == tty->read_head)
1312 echo_set_canon_col(tty);
1315 process_echoes(tty);
1318 if (I_PARMRK(tty) && c == (unsigned char) '\377')
1319 put_tty_queue(c, tty);
1321 put_tty_queue(c, tty);
1326 * n_tty_write_wakeup - asynchronous I/O notifier
1329 * Required for the ptys, serial driver etc. since processes
1330 * that attach themselves to the master and rely on ASYNC
1331 * IO must be woken up
1334 static void n_tty_write_wakeup(struct tty_struct *tty)
1336 /* Write out any echoed characters that are still pending */
1337 process_echoes(tty);
1340 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
1341 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1346 * n_tty_receive_buf - data receive
1347 * @tty: terminal device
1350 * @count: characters
1352 * Called by the terminal driver when a block of characters has
1353 * been received. This function must be called from soft contexts
1354 * not from interrupt context. The driver is responsible for making
1355 * calls one at a time and in order (or using flush_to_ldisc)
1358 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1359 char *fp, int count)
1361 const unsigned char *p;
1362 char *f, flags = TTY_NORMAL;
1365 unsigned long cpuflags;
1370 if (tty->real_raw) {
1371 spin_lock_irqsave(&tty->read_lock, cpuflags);
1372 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1373 N_TTY_BUF_SIZE - tty->read_head);
1375 memcpy(tty->read_buf + tty->read_head, cp, i);
1376 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1381 i = min(N_TTY_BUF_SIZE - tty->read_cnt,
1382 N_TTY_BUF_SIZE - tty->read_head);
1384 memcpy(tty->read_buf + tty->read_head, cp, i);
1385 tty->read_head = (tty->read_head + i) & (N_TTY_BUF_SIZE-1);
1387 spin_unlock_irqrestore(&tty->read_lock, cpuflags);
1389 for (i = count, p = cp, f = fp; i; i--, p++) {
1394 n_tty_receive_char(tty, *p);
1397 n_tty_receive_break(tty);
1401 n_tty_receive_parity_error(tty, *p);
1404 n_tty_receive_overrun(tty);
1407 printk(KERN_ERR "%s: unknown flag %d\n",
1408 tty_name(tty, buf), flags);
1412 if (tty->ops->flush_chars)
1413 tty->ops->flush_chars(tty);
1416 n_tty_set_room(tty);
1418 if (!tty->icanon && (tty->read_cnt >= tty->minimum_to_wake)) {
1419 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1420 if (waitqueue_active(&tty->read_wait))
1421 wake_up_interruptible(&tty->read_wait);
1425 * Check the remaining room for the input canonicalization
1426 * mode. We don't want to throttle the driver if we're in
1427 * canonical mode and don't have a newline yet!
1429 if (tty->receive_room < TTY_THRESHOLD_THROTTLE)
1433 int is_ignored(int sig)
1435 return (sigismember(¤t->blocked, sig) ||
1436 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1440 * n_tty_set_termios - termios data changed
1442 * @old: previous data
1444 * Called by the tty layer when the user changes termios flags so
1445 * that the line discipline can plan ahead. This function cannot sleep
1446 * and is protected from re-entry by the tty layer. The user is
1447 * guaranteed that this function will not be re-entered or in progress
1448 * when the ldisc is closed.
1450 * Locking: Caller holds tty->termios_mutex
1453 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1455 int canon_change = 1;
1459 canon_change = (old->c_lflag ^ tty->termios->c_lflag) & ICANON;
1461 memset(&tty->read_flags, 0, sizeof tty->read_flags);
1462 tty->canon_head = tty->read_tail;
1463 tty->canon_data = 0;
1467 if (canon_change && !L_ICANON(tty) && tty->read_cnt)
1468 wake_up_interruptible(&tty->read_wait);
1470 tty->icanon = (L_ICANON(tty) != 0);
1471 if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1474 n_tty_set_room(tty);
1477 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1478 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1479 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1481 memset(tty->process_char_map, 0, 256/8);
1483 if (I_IGNCR(tty) || I_ICRNL(tty))
1484 set_bit('\r', tty->process_char_map);
1486 set_bit('\n', tty->process_char_map);
1488 if (L_ICANON(tty)) {
1489 set_bit(ERASE_CHAR(tty), tty->process_char_map);
1490 set_bit(KILL_CHAR(tty), tty->process_char_map);
1491 set_bit(EOF_CHAR(tty), tty->process_char_map);
1492 set_bit('\n', tty->process_char_map);
1493 set_bit(EOL_CHAR(tty), tty->process_char_map);
1494 if (L_IEXTEN(tty)) {
1495 set_bit(WERASE_CHAR(tty),
1496 tty->process_char_map);
1497 set_bit(LNEXT_CHAR(tty),
1498 tty->process_char_map);
1499 set_bit(EOL2_CHAR(tty),
1500 tty->process_char_map);
1502 set_bit(REPRINT_CHAR(tty),
1503 tty->process_char_map);
1507 set_bit(START_CHAR(tty), tty->process_char_map);
1508 set_bit(STOP_CHAR(tty), tty->process_char_map);
1511 set_bit(INTR_CHAR(tty), tty->process_char_map);
1512 set_bit(QUIT_CHAR(tty), tty->process_char_map);
1513 set_bit(SUSP_CHAR(tty), tty->process_char_map);
1515 clear_bit(__DISABLED_CHAR, tty->process_char_map);
1520 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1521 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1522 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1527 n_tty_set_room(tty);
1528 /* The termios change make the tty ready for I/O */
1529 wake_up_interruptible(&tty->write_wait);
1530 wake_up_interruptible(&tty->read_wait);
1534 * n_tty_close - close the ldisc for this tty
1537 * Called from the terminal layer when this line discipline is
1538 * being shut down, either because of a close or becsuse of a
1539 * discipline change. The function will not be called while other
1540 * ldisc methods are in progress.
1543 static void n_tty_close(struct tty_struct *tty)
1545 n_tty_flush_buffer(tty);
1546 if (tty->read_buf) {
1547 free_buf(tty->read_buf);
1548 tty->read_buf = NULL;
1550 if (tty->echo_buf) {
1551 free_buf(tty->echo_buf);
1552 tty->echo_buf = NULL;
1557 * n_tty_open - open an ldisc
1558 * @tty: terminal to open
1560 * Called when this line discipline is being attached to the
1561 * terminal device. Can sleep. Called serialized so that no
1562 * other events will occur in parallel. No further open will occur
1566 static int n_tty_open(struct tty_struct *tty)
1571 /* These are ugly. Currently a malloc failure here can panic */
1572 if (!tty->read_buf) {
1573 tty->read_buf = alloc_buf();
1577 if (!tty->echo_buf) {
1578 tty->echo_buf = alloc_buf();
1582 memset(tty->read_buf, 0, N_TTY_BUF_SIZE);
1583 memset(tty->echo_buf, 0, N_TTY_BUF_SIZE);
1584 reset_buffer_flags(tty);
1586 n_tty_set_termios(tty, NULL);
1587 tty->minimum_to_wake = 1;
1592 static inline int input_available_p(struct tty_struct *tty, int amt)
1595 if (tty->canon_data)
1597 } else if (tty->read_cnt >= (amt ? amt : 1))
1604 * copy_from_read_buf - copy read data directly
1605 * @tty: terminal device
1609 * Helper function to speed up n_tty_read. It is only called when
1610 * ICANON is off; it copies characters straight from the tty queue to
1611 * user space directly. It can be profitably called twice; once to
1612 * drain the space from the tail pointer to the (physical) end of the
1613 * buffer, and once to drain the space from the (physical) beginning of
1614 * the buffer to head pointer.
1616 * Called under the tty->atomic_read_lock sem
1620 static int copy_from_read_buf(struct tty_struct *tty,
1621 unsigned char __user **b,
1627 unsigned long flags;
1630 spin_lock_irqsave(&tty->read_lock, flags);
1631 n = min(tty->read_cnt, N_TTY_BUF_SIZE - tty->read_tail);
1633 spin_unlock_irqrestore(&tty->read_lock, flags);
1635 retval = copy_to_user(*b, &tty->read_buf[tty->read_tail], n);
1637 tty_audit_add_data(tty, &tty->read_buf[tty->read_tail], n);
1638 spin_lock_irqsave(&tty->read_lock, flags);
1639 tty->read_tail = (tty->read_tail + n) & (N_TTY_BUF_SIZE-1);
1641 spin_unlock_irqrestore(&tty->read_lock, flags);
1648 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1652 * job_control - check job control
1654 * @file: file handle
1656 * Perform job control management checks on this file/tty descriptor
1657 * and if appropriate send any needed signals and return a negative
1658 * error code if action should be taken.
1661 * Locking: None - redirected write test is safe, testing
1662 * current->signal should possibly lock current->sighand
1666 static int job_control(struct tty_struct *tty, struct file *file)
1668 /* Job control check -- must be done at start and after
1669 every sleep (POSIX.1 7.1.1.4). */
1670 /* NOTE: not yet done after every sleep pending a thorough
1671 check of the logic of this change. -- jlc */
1672 /* don't stop on /dev/console */
1673 if (file->f_op->write != redirected_tty_write &&
1674 current->signal->tty == tty) {
1676 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1677 else if (task_pgrp(current) != tty->pgrp) {
1678 if (is_ignored(SIGTTIN) ||
1679 is_current_pgrp_orphaned())
1681 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1682 set_thread_flag(TIF_SIGPENDING);
1683 return -ERESTARTSYS;
1691 * n_tty_read - read function for tty
1693 * @file: file object
1694 * @buf: userspace buffer pointer
1697 * Perform reads for the line discipline. We are guaranteed that the
1698 * line discipline will not be closed under us but we may get multiple
1699 * parallel readers and must handle this ourselves. We may also get
1700 * a hangup. Always called in user context, may sleep.
1702 * This code must be sure never to sleep through a hangup.
1705 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1706 unsigned char __user *buf, size_t nr)
1708 unsigned char __user *b = buf;
1709 DECLARE_WAITQUEUE(wait, current);
1715 unsigned long flags;
1720 BUG_ON(!tty->read_buf);
1722 c = job_control(tty, file);
1727 timeout = MAX_SCHEDULE_TIMEOUT;
1729 time = (HZ / 10) * TIME_CHAR(tty);
1730 minimum = MIN_CHAR(tty);
1733 tty->minimum_to_wake = 1;
1734 else if (!waitqueue_active(&tty->read_wait) ||
1735 (tty->minimum_to_wake > minimum))
1736 tty->minimum_to_wake = minimum;
1743 tty->minimum_to_wake = minimum = 1;
1748 * Internal serialization of reads.
1750 if (file->f_flags & O_NONBLOCK) {
1751 if (!mutex_trylock(&tty->atomic_read_lock))
1754 if (mutex_lock_interruptible(&tty->atomic_read_lock))
1755 return -ERESTARTSYS;
1757 packet = tty->packet;
1759 add_wait_queue(&tty->read_wait, &wait);
1761 /* First test for status change. */
1762 if (packet && tty->link->ctrl_status) {
1766 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1767 cs = tty->link->ctrl_status;
1768 tty->link->ctrl_status = 0;
1769 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1770 if (tty_put_user(tty, cs, b++)) {
1778 /* This statement must be first before checking for input
1779 so that any interrupt will set the state back to
1781 set_current_state(TASK_INTERRUPTIBLE);
1783 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1784 ((minimum - (b - buf)) >= 1))
1785 tty->minimum_to_wake = (minimum - (b - buf));
1787 if (!input_available_p(tty, 0)) {
1788 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1792 if (tty_hung_up_p(file))
1796 if (file->f_flags & O_NONBLOCK) {
1800 if (signal_pending(current)) {
1801 retval = -ERESTARTSYS;
1804 /* FIXME: does n_tty_set_room need locking ? */
1805 n_tty_set_room(tty);
1806 timeout = schedule_timeout(timeout);
1809 __set_current_state(TASK_RUNNING);
1811 /* Deal with packet mode. */
1812 if (packet && b == buf) {
1813 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1822 /* N.B. avoid overrun if nr == 0 */
1823 while (nr && tty->read_cnt) {
1826 eol = test_and_clear_bit(tty->read_tail,
1828 c = tty->read_buf[tty->read_tail];
1829 spin_lock_irqsave(&tty->read_lock, flags);
1830 tty->read_tail = ((tty->read_tail+1) &
1831 (N_TTY_BUF_SIZE-1));
1834 /* this test should be redundant:
1835 * we shouldn't be reading data if
1838 if (--tty->canon_data < 0)
1839 tty->canon_data = 0;
1841 spin_unlock_irqrestore(&tty->read_lock, flags);
1843 if (!eol || (c != __DISABLED_CHAR)) {
1844 if (tty_put_user(tty, c, b++)) {
1852 tty_audit_push(tty);
1860 /* The copy function takes the read lock and handles
1861 locking internally for this case */
1862 uncopied = copy_from_read_buf(tty, &b, &nr);
1863 uncopied += copy_from_read_buf(tty, &b, &nr);
1870 /* If there is enough space in the read buffer now, let the
1871 * low-level driver know. We use n_tty_chars_in_buffer() to
1872 * check the buffer, as it now knows about canonical mode.
1873 * Otherwise, if the driver is throttled and the line is
1874 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1875 * we won't get any more characters.
1877 if (n_tty_chars_in_buffer(tty) <= TTY_THRESHOLD_UNTHROTTLE) {
1878 n_tty_set_room(tty);
1879 check_unthrottle(tty);
1882 if (b - buf >= minimum)
1887 mutex_unlock(&tty->atomic_read_lock);
1888 remove_wait_queue(&tty->read_wait, &wait);
1890 if (!waitqueue_active(&tty->read_wait))
1891 tty->minimum_to_wake = minimum;
1893 __set_current_state(TASK_RUNNING);
1898 clear_bit(TTY_PUSH, &tty->flags);
1899 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1902 n_tty_set_room(tty);
1907 * n_tty_write - write function for tty
1909 * @file: file object
1910 * @buf: userspace buffer pointer
1913 * Write function of the terminal device. This is serialized with
1914 * respect to other write callers but not to termios changes, reads
1915 * and other such events. Since the receive code will echo characters,
1916 * thus calling driver write methods, the output_lock is used in
1917 * the output processing functions called here as well as in the
1918 * echo processing function to protect the column state and space
1919 * left in the buffer.
1921 * This code must be sure never to sleep through a hangup.
1923 * Locking: output_lock to protect column state and space left
1924 * (note that the process_output*() functions take this
1928 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
1929 const unsigned char *buf, size_t nr)
1931 const unsigned char *b = buf;
1932 DECLARE_WAITQUEUE(wait, current);
1936 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
1937 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
1938 retval = tty_check_change(tty);
1943 /* Write out any echoed characters that are still pending */
1944 process_echoes(tty);
1946 add_wait_queue(&tty->write_wait, &wait);
1948 set_current_state(TASK_INTERRUPTIBLE);
1949 if (signal_pending(current)) {
1950 retval = -ERESTARTSYS;
1953 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
1957 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
1959 ssize_t num = process_output_block(tty, b, nr);
1971 if (process_output(c, tty) < 0)
1975 if (tty->ops->flush_chars)
1976 tty->ops->flush_chars(tty);
1979 c = tty->ops->write(tty, b, nr);
1992 if (file->f_flags & O_NONBLOCK) {
1999 __set_current_state(TASK_RUNNING);
2000 remove_wait_queue(&tty->write_wait, &wait);
2001 return (b - buf) ? b - buf : retval;
2005 * n_tty_poll - poll method for N_TTY
2006 * @tty: terminal device
2007 * @file: file accessing it
2010 * Called when the line discipline is asked to poll() for data or
2011 * for special events. This code is not serialized with respect to
2012 * other events save open/close.
2014 * This code must be sure never to sleep through a hangup.
2015 * Called without the kernel lock held - fine
2018 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2021 unsigned int mask = 0;
2023 poll_wait(file, &tty->read_wait, wait);
2024 poll_wait(file, &tty->write_wait, wait);
2025 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2026 mask |= POLLIN | POLLRDNORM;
2027 if (tty->packet && tty->link->ctrl_status)
2028 mask |= POLLPRI | POLLIN | POLLRDNORM;
2029 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2031 if (tty_hung_up_p(file))
2033 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2034 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2035 tty->minimum_to_wake = MIN_CHAR(tty);
2037 tty->minimum_to_wake = 1;
2039 if (tty->ops->write && !tty_is_writelocked(tty) &&
2040 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2041 tty_write_room(tty) > 0)
2042 mask |= POLLOUT | POLLWRNORM;
2046 static unsigned long inq_canon(struct tty_struct *tty)
2050 if (!tty->canon_data)
2052 head = tty->canon_head;
2053 tail = tty->read_tail;
2054 nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2055 /* Skip EOF-chars.. */
2056 while (head != tail) {
2057 if (test_bit(tail, tty->read_flags) &&
2058 tty->read_buf[tail] == __DISABLED_CHAR)
2060 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2065 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2066 unsigned int cmd, unsigned long arg)
2072 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2074 /* FIXME: Locking */
2075 retval = tty->read_cnt;
2077 retval = inq_canon(tty);
2078 return put_user(retval, (unsigned int __user *) arg);
2080 return n_tty_ioctl_helper(tty, file, cmd, arg);
2084 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2085 .magic = TTY_LDISC_MAGIC,
2088 .close = n_tty_close,
2089 .flush_buffer = n_tty_flush_buffer,
2090 .chars_in_buffer = n_tty_chars_in_buffer,
2092 .write = n_tty_write,
2093 .ioctl = n_tty_ioctl,
2094 .set_termios = n_tty_set_termios,
2096 .receive_buf = n_tty_receive_buf,
2097 .write_wakeup = n_tty_write_wakeup