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>
52 #include <linux/ratelimit.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
79 unsigned long overrun_time;
82 unsigned char lnext:1, erasing:1, raw:1, real_raw:1, icanon:1;
83 unsigned char echo_overrun:1;
85 DECLARE_BITMAP(process_char_map, 256);
86 DECLARE_BITMAP(read_flags, N_TTY_BUF_SIZE);
93 unsigned char *echo_buf;
94 unsigned int echo_pos;
95 unsigned int echo_cnt;
98 unsigned long canon_head;
99 unsigned int canon_column;
101 struct mutex atomic_read_lock;
102 struct mutex output_lock;
103 struct mutex echo_lock;
104 raw_spinlock_t read_lock;
107 static inline int tty_put_user(struct tty_struct *tty, unsigned char x,
108 unsigned char __user *ptr)
110 struct n_tty_data *ldata = tty->disc_data;
112 tty_audit_add_data(tty, &x, 1, ldata->icanon);
113 return put_user(x, ptr);
117 * n_tty_set__room - receive space
120 * Called by the driver to find out how much data it is
121 * permitted to feed to the line discipline without any being lost
122 * and thus to manage flow control. Not serialized. Answers for the
126 static void n_tty_set_room(struct tty_struct *tty)
128 struct n_tty_data *ldata = tty->disc_data;
132 /* ldata->read_cnt is not read locked ? */
134 /* Multiply read_cnt by 3, since each byte might take up to
135 * three times as many spaces when PARMRK is set (depending on
136 * its flags, e.g. parity error). */
137 left = N_TTY_BUF_SIZE - ldata->read_cnt * 3 - 1;
139 left = N_TTY_BUF_SIZE - ldata->read_cnt - 1;
142 * If we are doing input canonicalization, and there are no
143 * pending newlines, let characters through without limit, so
144 * that erase characters will be handled. Other excess
145 * characters will be beeped.
148 left = ldata->icanon && !ldata->canon_data;
149 old_left = tty->receive_room;
150 tty->receive_room = left;
152 /* Did this open up the receive buffer? We may need to flip */
153 if (left && !old_left) {
154 WARN_RATELIMIT(tty->port->itty == NULL,
155 "scheduling with invalid itty\n");
156 /* see if ldisc has been killed - if so, this means that
157 * even though the ldisc has been halted and ->buf.work
158 * cancelled, ->buf.work is about to be rescheduled
160 WARN_RATELIMIT(test_bit(TTY_LDISC_HALTED, &tty->flags),
161 "scheduling buffer work for halted ldisc\n");
162 schedule_work(&tty->port->buf.work);
166 static void put_tty_queue_nolock(unsigned char c, struct n_tty_data *ldata)
168 if (ldata->read_cnt < N_TTY_BUF_SIZE) {
169 ldata->read_buf[ldata->read_head] = c;
170 ldata->read_head = (ldata->read_head + 1) & (N_TTY_BUF_SIZE-1);
176 * put_tty_queue - add character to tty
180 * Add a character to the tty read_buf queue. This is done under the
181 * read_lock to serialize character addition and also to protect us
182 * against parallel reads or flushes
185 static void put_tty_queue(unsigned char c, struct n_tty_data *ldata)
189 * The problem of stomping on the buffers ends here.
190 * Why didn't anyone see this one coming? --AJK
192 raw_spin_lock_irqsave(&ldata->read_lock, flags);
193 put_tty_queue_nolock(c, ldata);
194 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
198 * reset_buffer_flags - reset buffer state
199 * @tty: terminal to reset
201 * Reset the read buffer counters and clear the flags.
202 * Called from n_tty_open() and n_tty_flush_buffer().
204 * Locking: tty_read_lock for read fields.
207 static void reset_buffer_flags(struct n_tty_data *ldata)
211 raw_spin_lock_irqsave(&ldata->read_lock, flags);
212 ldata->read_head = ldata->read_tail = ldata->read_cnt = 0;
213 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
215 mutex_lock(&ldata->echo_lock);
216 ldata->echo_pos = ldata->echo_cnt = ldata->echo_overrun = 0;
217 mutex_unlock(&ldata->echo_lock);
219 ldata->canon_head = ldata->canon_data = ldata->erasing = 0;
220 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
223 static void n_tty_packet_mode_flush(struct tty_struct *tty)
227 spin_lock_irqsave(&tty->ctrl_lock, flags);
228 if (tty->link->packet) {
229 tty->ctrl_status |= TIOCPKT_FLUSHREAD;
230 wake_up_interruptible(&tty->link->read_wait);
232 spin_unlock_irqrestore(&tty->ctrl_lock, flags);
236 * n_tty_flush_buffer - clean input queue
237 * @tty: terminal device
239 * Flush the input buffer. Called when the tty layer wants the
240 * buffer flushed (eg at hangup) or when the N_TTY line discipline
241 * internally has to clean the pending queue (for example some signals).
243 * Locking: ctrl_lock, read_lock.
246 static void n_tty_flush_buffer(struct tty_struct *tty)
248 reset_buffer_flags(tty->disc_data);
252 n_tty_packet_mode_flush(tty);
256 * n_tty_chars_in_buffer - report available bytes
259 * Report the number of characters buffered to be delivered to user
260 * at this instant in time.
265 static ssize_t n_tty_chars_in_buffer(struct tty_struct *tty)
267 struct n_tty_data *ldata = tty->disc_data;
271 raw_spin_lock_irqsave(&ldata->read_lock, flags);
272 if (!ldata->icanon) {
274 } else if (ldata->canon_data) {
275 n = (ldata->canon_head > ldata->read_tail) ?
276 ldata->canon_head - ldata->read_tail :
277 ldata->canon_head + (N_TTY_BUF_SIZE - ldata->read_tail);
279 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
284 * is_utf8_continuation - utf8 multibyte check
287 * Returns true if the utf8 character 'c' is a multibyte continuation
288 * character. We use this to correctly compute the on screen size
289 * of the character when printing
292 static inline int is_utf8_continuation(unsigned char c)
294 return (c & 0xc0) == 0x80;
298 * is_continuation - multibyte check
301 * Returns true if the utf8 character 'c' is a multibyte continuation
302 * character and the terminal is in unicode mode.
305 static inline int is_continuation(unsigned char c, struct tty_struct *tty)
307 return I_IUTF8(tty) && is_utf8_continuation(c);
311 * do_output_char - output one character
312 * @c: character (or partial unicode symbol)
313 * @tty: terminal device
314 * @space: space available in tty driver write buffer
316 * This is a helper function that handles one output character
317 * (including special characters like TAB, CR, LF, etc.),
318 * doing OPOST processing and putting the results in the
319 * tty driver's write buffer.
321 * Note that Linux currently ignores TABDLY, CRDLY, VTDLY, FFDLY
322 * and NLDLY. They simply aren't relevant in the world today.
323 * If you ever need them, add them here.
325 * Returns the number of bytes of buffer space used or -1 if
328 * Locking: should be called under the output_lock to protect
329 * the column state and space left in the buffer
332 static int do_output_char(unsigned char c, struct tty_struct *tty, int space)
334 struct n_tty_data *ldata = tty->disc_data;
347 ldata->canon_column = ldata->column = 0;
348 tty->ops->write(tty, "\r\n", 2);
351 ldata->canon_column = ldata->column;
354 if (O_ONOCR(tty) && ldata->column == 0)
359 ldata->canon_column = ldata->column = 0;
362 ldata->canon_column = ldata->column = 0;
365 spaces = 8 - (ldata->column & 7);
366 if (O_TABDLY(tty) == XTABS) {
369 ldata->column += spaces;
370 tty->ops->write(tty, " ", spaces);
373 ldata->column += spaces;
376 if (ldata->column > 0)
383 if (!is_continuation(c, tty))
389 tty_put_char(tty, c);
394 * process_output - output post processor
395 * @c: character (or partial unicode symbol)
396 * @tty: terminal device
398 * Output one character with OPOST processing.
399 * Returns -1 when the output device is full and the character
402 * Locking: output_lock to protect column state and space left
403 * (also, this is called from n_tty_write under the
404 * tty layer write lock)
407 static int process_output(unsigned char c, struct tty_struct *tty)
409 struct n_tty_data *ldata = tty->disc_data;
412 mutex_lock(&ldata->output_lock);
414 space = tty_write_room(tty);
415 retval = do_output_char(c, tty, space);
417 mutex_unlock(&ldata->output_lock);
425 * process_output_block - block post processor
426 * @tty: terminal device
427 * @buf: character buffer
428 * @nr: number of bytes to output
430 * Output a block of characters with OPOST processing.
431 * Returns the number of characters output.
433 * This path is used to speed up block console writes, among other
434 * things when processing blocks of output data. It handles only
435 * the simple cases normally found and helps to generate blocks of
436 * symbols for the console driver and thus improve performance.
438 * Locking: output_lock to protect column state and space left
439 * (also, this is called from n_tty_write under the
440 * tty layer write lock)
443 static ssize_t process_output_block(struct tty_struct *tty,
444 const unsigned char *buf, unsigned int nr)
446 struct n_tty_data *ldata = tty->disc_data;
449 const unsigned char *cp;
451 mutex_lock(&ldata->output_lock);
453 space = tty_write_room(tty);
455 mutex_unlock(&ldata->output_lock);
461 for (i = 0, cp = buf; i < nr; i++, cp++) {
462 unsigned char c = *cp;
470 ldata->canon_column = ldata->column;
473 if (O_ONOCR(tty) && ldata->column == 0)
477 ldata->canon_column = ldata->column = 0;
482 if (ldata->column > 0)
489 if (!is_continuation(c, tty))
496 i = tty->ops->write(tty, buf, i);
498 mutex_unlock(&ldata->output_lock);
503 * process_echoes - write pending echo characters
504 * @tty: terminal device
506 * Write previously buffered echo (and other ldisc-generated)
507 * characters to the tty.
509 * Characters generated by the ldisc (including echoes) need to
510 * be buffered because the driver's write buffer can fill during
511 * heavy program output. Echoing straight to the driver will
512 * often fail under these conditions, causing lost characters and
513 * resulting mismatches of ldisc state information.
515 * Since the ldisc state must represent the characters actually sent
516 * to the driver at the time of the write, operations like certain
517 * changes in column state are also saved in the buffer and executed
520 * A circular fifo buffer is used so that the most recent characters
521 * are prioritized. Also, when control characters are echoed with a
522 * prefixed "^", the pair is treated atomically and thus not separated.
524 * Locking: output_lock to protect column state and space left,
525 * echo_lock to protect the echo buffer
528 static void process_echoes(struct tty_struct *tty)
530 struct n_tty_data *ldata = tty->disc_data;
533 unsigned char *cp, *buf_end;
535 if (!ldata->echo_cnt)
538 mutex_lock(&ldata->output_lock);
539 mutex_lock(&ldata->echo_lock);
541 space = tty_write_room(tty);
543 buf_end = ldata->echo_buf + N_TTY_BUF_SIZE;
544 cp = ldata->echo_buf + ldata->echo_pos;
545 nr = ldata->echo_cnt;
548 if (c == ECHO_OP_START) {
551 int no_space_left = 0;
554 * If the buffer byte is the start of a multi-byte
555 * operation, get the next byte, which is either the
556 * op code or a control character value.
560 opp -= N_TTY_BUF_SIZE;
564 unsigned int num_chars, num_bs;
566 case ECHO_OP_ERASE_TAB:
567 if (++opp == buf_end)
568 opp -= N_TTY_BUF_SIZE;
572 * Determine how many columns to go back
573 * in order to erase the tab.
574 * This depends on the number of columns
575 * used by other characters within the tab
576 * area. If this (modulo 8) count is from
577 * the start of input rather than from a
578 * previous tab, we offset by canon column.
579 * Otherwise, tab spacing is normal.
581 if (!(num_chars & 0x80))
582 num_chars += ldata->canon_column;
583 num_bs = 8 - (num_chars & 7);
585 if (num_bs > space) {
591 tty_put_char(tty, '\b');
592 if (ldata->column > 0)
599 case ECHO_OP_SET_CANON_COL:
600 ldata->canon_column = ldata->column;
605 case ECHO_OP_MOVE_BACK_COL:
606 if (ldata->column > 0)
613 /* This is an escaped echo op start code */
618 tty_put_char(tty, ECHO_OP_START);
627 * If the op is not a special byte code,
628 * it is a ctrl char tagged to be echoed
629 * as "^X" (where X is the letter
630 * representing the control char).
631 * Note that we must ensure there is
632 * enough space for the whole ctrl pair.
639 tty_put_char(tty, '^');
640 tty_put_char(tty, op ^ 0100);
651 !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
652 int retval = do_output_char(c, tty, space);
659 tty_put_char(tty, c);
666 /* When end of circular buffer reached, wrap around */
668 cp -= N_TTY_BUF_SIZE;
674 ldata->echo_overrun = 0;
676 int num_processed = ldata->echo_cnt - nr;
677 ldata->echo_pos += num_processed;
678 ldata->echo_pos &= N_TTY_BUF_SIZE - 1;
679 ldata->echo_cnt = nr;
680 if (num_processed > 0)
681 ldata->echo_overrun = 0;
684 mutex_unlock(&ldata->echo_lock);
685 mutex_unlock(&ldata->output_lock);
687 if (tty->ops->flush_chars)
688 tty->ops->flush_chars(tty);
692 * add_echo_byte - add a byte to the echo buffer
693 * @c: unicode byte to echo
696 * Add a character or operation byte to the echo buffer.
698 * Should be called under the echo lock to protect the echo buffer.
701 static void add_echo_byte(unsigned char c, struct n_tty_data *ldata)
705 if (ldata->echo_cnt == N_TTY_BUF_SIZE) {
706 /* Circular buffer is already at capacity */
707 new_byte_pos = ldata->echo_pos;
710 * Since the buffer start position needs to be advanced,
711 * be sure to step by a whole operation byte group.
713 if (ldata->echo_buf[ldata->echo_pos] == ECHO_OP_START) {
714 if (ldata->echo_buf[(ldata->echo_pos + 1) &
715 (N_TTY_BUF_SIZE - 1)] ==
717 ldata->echo_pos += 3;
718 ldata->echo_cnt -= 2;
720 ldata->echo_pos += 2;
721 ldata->echo_cnt -= 1;
726 ldata->echo_pos &= N_TTY_BUF_SIZE - 1;
728 ldata->echo_overrun = 1;
730 new_byte_pos = ldata->echo_pos + ldata->echo_cnt;
731 new_byte_pos &= N_TTY_BUF_SIZE - 1;
735 ldata->echo_buf[new_byte_pos] = c;
739 * echo_move_back_col - add operation to move back a column
742 * Add an operation to the echo buffer to move back one column.
744 * Locking: echo_lock to protect the echo buffer
747 static void echo_move_back_col(struct n_tty_data *ldata)
749 mutex_lock(&ldata->echo_lock);
750 add_echo_byte(ECHO_OP_START, ldata);
751 add_echo_byte(ECHO_OP_MOVE_BACK_COL, ldata);
752 mutex_unlock(&ldata->echo_lock);
756 * echo_set_canon_col - add operation to set the canon column
759 * Add an operation to the echo buffer to set the canon column
760 * to the current column.
762 * Locking: echo_lock to protect the echo buffer
765 static void echo_set_canon_col(struct n_tty_data *ldata)
767 mutex_lock(&ldata->echo_lock);
768 add_echo_byte(ECHO_OP_START, ldata);
769 add_echo_byte(ECHO_OP_SET_CANON_COL, ldata);
770 mutex_unlock(&ldata->echo_lock);
774 * echo_erase_tab - add operation to erase a tab
775 * @num_chars: number of character columns already used
776 * @after_tab: true if num_chars starts after a previous tab
779 * Add an operation to the echo buffer to erase a tab.
781 * Called by the eraser function, which knows how many character
782 * columns have been used since either a previous tab or the start
783 * of input. This information will be used later, along with
784 * canon column (if applicable), to go back the correct number
787 * Locking: echo_lock to protect the echo buffer
790 static void echo_erase_tab(unsigned int num_chars, int after_tab,
791 struct n_tty_data *ldata)
793 mutex_lock(&ldata->echo_lock);
795 add_echo_byte(ECHO_OP_START, ldata);
796 add_echo_byte(ECHO_OP_ERASE_TAB, ldata);
798 /* We only need to know this modulo 8 (tab spacing) */
801 /* Set the high bit as a flag if num_chars is after a previous tab */
805 add_echo_byte(num_chars, ldata);
807 mutex_unlock(&ldata->echo_lock);
811 * echo_char_raw - echo a character raw
812 * @c: unicode byte to echo
813 * @tty: terminal device
815 * Echo user input back onto the screen. This must be called only when
816 * L_ECHO(tty) is true. Called from the driver receive_buf path.
818 * This variant does not treat control characters specially.
820 * Locking: echo_lock to protect the echo buffer
823 static void echo_char_raw(unsigned char c, struct n_tty_data *ldata)
825 mutex_lock(&ldata->echo_lock);
826 if (c == ECHO_OP_START) {
827 add_echo_byte(ECHO_OP_START, ldata);
828 add_echo_byte(ECHO_OP_START, ldata);
830 add_echo_byte(c, ldata);
832 mutex_unlock(&ldata->echo_lock);
836 * echo_char - echo a character
837 * @c: unicode byte to echo
838 * @tty: terminal device
840 * Echo user input back onto the screen. This must be called only when
841 * L_ECHO(tty) is true. Called from the driver receive_buf path.
843 * This variant tags control characters to be echoed as "^X"
844 * (where X is the letter representing the control char).
846 * Locking: echo_lock to protect the echo buffer
849 static void echo_char(unsigned char c, struct tty_struct *tty)
851 struct n_tty_data *ldata = tty->disc_data;
853 mutex_lock(&ldata->echo_lock);
855 if (c == ECHO_OP_START) {
856 add_echo_byte(ECHO_OP_START, ldata);
857 add_echo_byte(ECHO_OP_START, ldata);
859 if (L_ECHOCTL(tty) && iscntrl(c) && c != '\t')
860 add_echo_byte(ECHO_OP_START, ldata);
861 add_echo_byte(c, ldata);
864 mutex_unlock(&ldata->echo_lock);
868 * finish_erasing - complete erase
872 static inline void finish_erasing(struct n_tty_data *ldata)
874 if (ldata->erasing) {
875 echo_char_raw('/', ldata);
881 * eraser - handle erase function
882 * @c: character input
883 * @tty: terminal device
885 * Perform erase and necessary output when an erase character is
886 * present in the stream from the driver layer. Handles the complexities
887 * of UTF-8 multibyte symbols.
889 * Locking: read_lock for tty buffers
892 static void eraser(unsigned char c, struct tty_struct *tty)
894 struct n_tty_data *ldata = tty->disc_data;
895 enum { ERASE, WERASE, KILL } kill_type;
896 int head, seen_alnums, cnt;
899 /* FIXME: locking needed ? */
900 if (ldata->read_head == ldata->canon_head) {
901 /* process_output('\a', tty); */ /* what do you think? */
904 if (c == ERASE_CHAR(tty))
906 else if (c == WERASE_CHAR(tty))
910 raw_spin_lock_irqsave(&ldata->read_lock, flags);
911 ldata->read_cnt -= ((ldata->read_head - ldata->canon_head) &
912 (N_TTY_BUF_SIZE - 1));
913 ldata->read_head = ldata->canon_head;
914 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
917 if (!L_ECHOK(tty) || !L_ECHOKE(tty) || !L_ECHOE(tty)) {
918 raw_spin_lock_irqsave(&ldata->read_lock, flags);
919 ldata->read_cnt -= ((ldata->read_head - ldata->canon_head) &
920 (N_TTY_BUF_SIZE - 1));
921 ldata->read_head = ldata->canon_head;
922 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
923 finish_erasing(ldata);
924 echo_char(KILL_CHAR(tty), tty);
925 /* Add a newline if ECHOK is on and ECHOKE is off. */
927 echo_char_raw('\n', ldata);
934 /* FIXME: Locking ?? */
935 while (ldata->read_head != ldata->canon_head) {
936 head = ldata->read_head;
938 /* erase a single possibly multibyte character */
940 head = (head - 1) & (N_TTY_BUF_SIZE-1);
941 c = ldata->read_buf[head];
942 } while (is_continuation(c, tty) && head != ldata->canon_head);
944 /* do not partially erase */
945 if (is_continuation(c, tty))
948 if (kill_type == WERASE) {
949 /* Equivalent to BSD's ALTWERASE. */
950 if (isalnum(c) || c == '_')
952 else if (seen_alnums)
955 cnt = (ldata->read_head - head) & (N_TTY_BUF_SIZE-1);
956 raw_spin_lock_irqsave(&ldata->read_lock, flags);
957 ldata->read_head = head;
958 ldata->read_cnt -= cnt;
959 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
961 if (L_ECHOPRT(tty)) {
962 if (!ldata->erasing) {
963 echo_char_raw('\\', ldata);
966 /* if cnt > 1, output a multi-byte character */
969 head = (head+1) & (N_TTY_BUF_SIZE-1);
970 echo_char_raw(ldata->read_buf[head],
972 echo_move_back_col(ldata);
974 } else if (kill_type == ERASE && !L_ECHOE(tty)) {
975 echo_char(ERASE_CHAR(tty), tty);
976 } else if (c == '\t') {
977 unsigned int num_chars = 0;
979 unsigned long tail = ldata->read_head;
982 * Count the columns used for characters
983 * since the start of input or after a
985 * This info is used to go back the correct
988 while (tail != ldata->canon_head) {
989 tail = (tail-1) & (N_TTY_BUF_SIZE-1);
990 c = ldata->read_buf[tail];
994 } else if (iscntrl(c)) {
997 } else if (!is_continuation(c, tty)) {
1001 echo_erase_tab(num_chars, after_tab, ldata);
1003 if (iscntrl(c) && L_ECHOCTL(tty)) {
1004 echo_char_raw('\b', ldata);
1005 echo_char_raw(' ', ldata);
1006 echo_char_raw('\b', ldata);
1008 if (!iscntrl(c) || L_ECHOCTL(tty)) {
1009 echo_char_raw('\b', ldata);
1010 echo_char_raw(' ', ldata);
1011 echo_char_raw('\b', ldata);
1015 if (kill_type == ERASE)
1018 if (ldata->read_head == ldata->canon_head && L_ECHO(tty))
1019 finish_erasing(ldata);
1023 * isig - handle the ISIG optio
1027 * Called when a signal is being sent due to terminal input.
1028 * Called from the driver receive_buf path so serialized.
1030 * Locking: ctrl_lock
1033 static inline void isig(int sig, struct tty_struct *tty)
1035 struct pid *tty_pgrp = tty_get_pgrp(tty);
1037 kill_pgrp(tty_pgrp, sig, 1);
1043 * n_tty_receive_break - handle break
1046 * An RS232 break event has been hit in the incoming bitstream. This
1047 * can cause a variety of events depending upon the termios settings.
1049 * Called from the receive_buf path so single threaded.
1052 static inline void n_tty_receive_break(struct tty_struct *tty)
1054 struct n_tty_data *ldata = tty->disc_data;
1058 if (I_BRKINT(tty)) {
1060 if (!L_NOFLSH(tty)) {
1061 n_tty_flush_buffer(tty);
1062 tty_driver_flush_buffer(tty);
1066 if (I_PARMRK(tty)) {
1067 put_tty_queue('\377', ldata);
1068 put_tty_queue('\0', ldata);
1070 put_tty_queue('\0', ldata);
1071 wake_up_interruptible(&tty->read_wait);
1075 * n_tty_receive_overrun - handle overrun reporting
1078 * Data arrived faster than we could process it. While the tty
1079 * driver has flagged this the bits that were missed are gone
1082 * Called from the receive_buf path so single threaded. Does not
1083 * need locking as num_overrun and overrun_time are function
1087 static inline void n_tty_receive_overrun(struct tty_struct *tty)
1089 struct n_tty_data *ldata = tty->disc_data;
1092 ldata->num_overrun++;
1093 if (time_after(jiffies, ldata->overrun_time + HZ) ||
1094 time_after(ldata->overrun_time, jiffies)) {
1095 printk(KERN_WARNING "%s: %d input overrun(s)\n",
1097 ldata->num_overrun);
1098 ldata->overrun_time = jiffies;
1099 ldata->num_overrun = 0;
1104 * n_tty_receive_parity_error - error notifier
1105 * @tty: terminal device
1108 * Process a parity error and queue the right data to indicate
1109 * the error case if necessary. Locking as per n_tty_receive_buf.
1111 static inline void n_tty_receive_parity_error(struct tty_struct *tty,
1114 struct n_tty_data *ldata = tty->disc_data;
1118 if (I_PARMRK(tty)) {
1119 put_tty_queue('\377', ldata);
1120 put_tty_queue('\0', ldata);
1121 put_tty_queue(c, ldata);
1122 } else if (I_INPCK(tty))
1123 put_tty_queue('\0', ldata);
1125 put_tty_queue(c, ldata);
1126 wake_up_interruptible(&tty->read_wait);
1130 * n_tty_receive_char - perform processing
1131 * @tty: terminal device
1134 * Process an individual character of input received from the driver.
1135 * This is serialized with respect to itself by the rules for the
1139 static inline void n_tty_receive_char(struct tty_struct *tty, unsigned char c)
1141 struct n_tty_data *ldata = tty->disc_data;
1142 unsigned long flags;
1146 put_tty_queue(c, ldata);
1152 if (I_IUCLC(tty) && L_IEXTEN(tty))
1155 if (L_EXTPROC(tty)) {
1156 put_tty_queue(c, ldata);
1160 if (tty->stopped && !tty->flow_stopped && I_IXON(tty) &&
1161 I_IXANY(tty) && c != START_CHAR(tty) && c != STOP_CHAR(tty) &&
1162 c != INTR_CHAR(tty) && c != QUIT_CHAR(tty) && c != SUSP_CHAR(tty)) {
1164 process_echoes(tty);
1169 if (c == START_CHAR(tty)) {
1171 process_echoes(tty);
1172 } else if (c == STOP_CHAR(tty))
1179 * If the previous character was LNEXT, or we know that this
1180 * character is not one of the characters that we'll have to
1181 * handle specially, do shortcut processing to speed things
1184 if (!test_bit(c, ldata->process_char_map) || ldata->lnext) {
1186 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1187 if (ldata->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1188 /* beep if no space */
1190 process_output('\a', tty);
1194 finish_erasing(ldata);
1195 /* Record the column of first canon char. */
1196 if (ldata->canon_head == ldata->read_head)
1197 echo_set_canon_col(ldata);
1199 process_echoes(tty);
1202 put_tty_queue(c, ldata);
1203 put_tty_queue(c, ldata);
1208 if (c == START_CHAR(tty)) {
1210 process_echoes(tty);
1213 if (c == STOP_CHAR(tty)) {
1222 if (c == INTR_CHAR(tty))
1225 if (c == QUIT_CHAR(tty))
1228 if (c == SUSP_CHAR(tty)) {
1230 if (!L_NOFLSH(tty)) {
1231 n_tty_flush_buffer(tty);
1232 tty_driver_flush_buffer(tty);
1238 process_echoes(tty);
1250 } else if (c == '\n' && I_INLCR(tty))
1253 if (ldata->icanon) {
1254 if (c == ERASE_CHAR(tty) || c == KILL_CHAR(tty) ||
1255 (c == WERASE_CHAR(tty) && L_IEXTEN(tty))) {
1257 process_echoes(tty);
1260 if (c == LNEXT_CHAR(tty) && L_IEXTEN(tty)) {
1263 finish_erasing(ldata);
1264 if (L_ECHOCTL(tty)) {
1265 echo_char_raw('^', ldata);
1266 echo_char_raw('\b', ldata);
1267 process_echoes(tty);
1272 if (c == REPRINT_CHAR(tty) && L_ECHO(tty) &&
1274 unsigned long tail = ldata->canon_head;
1276 finish_erasing(ldata);
1278 echo_char_raw('\n', ldata);
1279 while (tail != ldata->read_head) {
1280 echo_char(ldata->read_buf[tail], tty);
1281 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
1283 process_echoes(tty);
1287 if (ldata->read_cnt >= N_TTY_BUF_SIZE) {
1289 process_output('\a', tty);
1292 if (L_ECHO(tty) || L_ECHONL(tty)) {
1293 echo_char_raw('\n', ldata);
1294 process_echoes(tty);
1296 goto handle_newline;
1298 if (c == EOF_CHAR(tty)) {
1299 if (ldata->read_cnt >= N_TTY_BUF_SIZE)
1301 if (ldata->canon_head != ldata->read_head)
1302 set_bit(TTY_PUSH, &tty->flags);
1303 c = __DISABLED_CHAR;
1304 goto handle_newline;
1306 if ((c == EOL_CHAR(tty)) ||
1307 (c == EOL2_CHAR(tty) && L_IEXTEN(tty))) {
1308 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty))
1310 if (ldata->read_cnt >= (N_TTY_BUF_SIZE - parmrk)) {
1312 process_output('\a', tty);
1316 * XXX are EOL_CHAR and EOL2_CHAR echoed?!?
1319 /* Record the column of first canon char. */
1320 if (ldata->canon_head == ldata->read_head)
1321 echo_set_canon_col(ldata);
1323 process_echoes(tty);
1326 * XXX does PARMRK doubling happen for
1327 * EOL_CHAR and EOL2_CHAR?
1330 put_tty_queue(c, ldata);
1333 raw_spin_lock_irqsave(&ldata->read_lock, flags);
1334 set_bit(ldata->read_head, ldata->read_flags);
1335 put_tty_queue_nolock(c, ldata);
1336 ldata->canon_head = ldata->read_head;
1337 ldata->canon_data++;
1338 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
1339 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1340 if (waitqueue_active(&tty->read_wait))
1341 wake_up_interruptible(&tty->read_wait);
1346 parmrk = (c == (unsigned char) '\377' && I_PARMRK(tty)) ? 1 : 0;
1347 if (ldata->read_cnt >= (N_TTY_BUF_SIZE - parmrk - 1)) {
1348 /* beep if no space */
1350 process_output('\a', tty);
1354 finish_erasing(ldata);
1356 echo_char_raw('\n', ldata);
1358 /* Record the column of first canon char. */
1359 if (ldata->canon_head == ldata->read_head)
1360 echo_set_canon_col(ldata);
1363 process_echoes(tty);
1367 put_tty_queue(c, ldata);
1369 put_tty_queue(c, ldata);
1374 * n_tty_write_wakeup - asynchronous I/O notifier
1377 * Required for the ptys, serial driver etc. since processes
1378 * that attach themselves to the master and rely on ASYNC
1379 * IO must be woken up
1382 static void n_tty_write_wakeup(struct tty_struct *tty)
1384 if (tty->fasync && test_and_clear_bit(TTY_DO_WRITE_WAKEUP, &tty->flags))
1385 kill_fasync(&tty->fasync, SIGIO, POLL_OUT);
1389 * n_tty_receive_buf - data receive
1390 * @tty: terminal device
1393 * @count: characters
1395 * Called by the terminal driver when a block of characters has
1396 * been received. This function must be called from soft contexts
1397 * not from interrupt context. The driver is responsible for making
1398 * calls one at a time and in order (or using flush_to_ldisc)
1401 static void n_tty_receive_buf(struct tty_struct *tty, const unsigned char *cp,
1402 char *fp, int count)
1404 struct n_tty_data *ldata = tty->disc_data;
1405 const unsigned char *p;
1406 char *f, flags = TTY_NORMAL;
1409 unsigned long cpuflags;
1411 if (ldata->real_raw) {
1412 raw_spin_lock_irqsave(&ldata->read_lock, cpuflags);
1413 i = min(N_TTY_BUF_SIZE - ldata->read_cnt,
1414 N_TTY_BUF_SIZE - ldata->read_head);
1416 memcpy(ldata->read_buf + ldata->read_head, cp, i);
1417 ldata->read_head = (ldata->read_head + i) & (N_TTY_BUF_SIZE-1);
1418 ldata->read_cnt += i;
1422 i = min(N_TTY_BUF_SIZE - ldata->read_cnt,
1423 N_TTY_BUF_SIZE - ldata->read_head);
1425 memcpy(ldata->read_buf + ldata->read_head, cp, i);
1426 ldata->read_head = (ldata->read_head + i) & (N_TTY_BUF_SIZE-1);
1427 ldata->read_cnt += i;
1428 raw_spin_unlock_irqrestore(&ldata->read_lock, cpuflags);
1430 for (i = count, p = cp, f = fp; i; i--, p++) {
1435 n_tty_receive_char(tty, *p);
1438 n_tty_receive_break(tty);
1442 n_tty_receive_parity_error(tty, *p);
1445 n_tty_receive_overrun(tty);
1448 printk(KERN_ERR "%s: unknown flag %d\n",
1449 tty_name(tty, buf), flags);
1453 if (tty->ops->flush_chars)
1454 tty->ops->flush_chars(tty);
1457 n_tty_set_room(tty);
1459 if ((!ldata->icanon && (ldata->read_cnt >= tty->minimum_to_wake)) ||
1461 kill_fasync(&tty->fasync, SIGIO, POLL_IN);
1462 if (waitqueue_active(&tty->read_wait))
1463 wake_up_interruptible(&tty->read_wait);
1467 * Check the remaining room for the input canonicalization
1468 * mode. We don't want to throttle the driver if we're in
1469 * canonical mode and don't have a newline yet!
1472 tty_set_flow_change(tty, TTY_THROTTLE_SAFE);
1473 if (tty->receive_room >= TTY_THRESHOLD_THROTTLE)
1475 if (!tty_throttle_safe(tty))
1478 __tty_set_flow_change(tty, 0);
1481 int is_ignored(int sig)
1483 return (sigismember(¤t->blocked, sig) ||
1484 current->sighand->action[sig-1].sa.sa_handler == SIG_IGN);
1488 * n_tty_set_termios - termios data changed
1490 * @old: previous data
1492 * Called by the tty layer when the user changes termios flags so
1493 * that the line discipline can plan ahead. This function cannot sleep
1494 * and is protected from re-entry by the tty layer. The user is
1495 * guaranteed that this function will not be re-entered or in progress
1496 * when the ldisc is closed.
1498 * Locking: Caller holds tty->termios_mutex
1501 static void n_tty_set_termios(struct tty_struct *tty, struct ktermios *old)
1503 struct n_tty_data *ldata = tty->disc_data;
1504 int canon_change = 1;
1507 canon_change = (old->c_lflag ^ tty->termios.c_lflag) & ICANON;
1509 bitmap_zero(ldata->read_flags, N_TTY_BUF_SIZE);
1510 ldata->canon_head = ldata->read_tail;
1511 ldata->canon_data = 0;
1515 if (canon_change && !L_ICANON(tty) && ldata->read_cnt)
1516 wake_up_interruptible(&tty->read_wait);
1518 ldata->icanon = (L_ICANON(tty) != 0);
1519 if (test_bit(TTY_HW_COOK_IN, &tty->flags)) {
1521 ldata->real_raw = 1;
1522 n_tty_set_room(tty);
1525 if (I_ISTRIP(tty) || I_IUCLC(tty) || I_IGNCR(tty) ||
1526 I_ICRNL(tty) || I_INLCR(tty) || L_ICANON(tty) ||
1527 I_IXON(tty) || L_ISIG(tty) || L_ECHO(tty) ||
1529 bitmap_zero(ldata->process_char_map, 256);
1531 if (I_IGNCR(tty) || I_ICRNL(tty))
1532 set_bit('\r', ldata->process_char_map);
1534 set_bit('\n', ldata->process_char_map);
1536 if (L_ICANON(tty)) {
1537 set_bit(ERASE_CHAR(tty), ldata->process_char_map);
1538 set_bit(KILL_CHAR(tty), ldata->process_char_map);
1539 set_bit(EOF_CHAR(tty), ldata->process_char_map);
1540 set_bit('\n', ldata->process_char_map);
1541 set_bit(EOL_CHAR(tty), ldata->process_char_map);
1542 if (L_IEXTEN(tty)) {
1543 set_bit(WERASE_CHAR(tty),
1544 ldata->process_char_map);
1545 set_bit(LNEXT_CHAR(tty),
1546 ldata->process_char_map);
1547 set_bit(EOL2_CHAR(tty),
1548 ldata->process_char_map);
1550 set_bit(REPRINT_CHAR(tty),
1551 ldata->process_char_map);
1555 set_bit(START_CHAR(tty), ldata->process_char_map);
1556 set_bit(STOP_CHAR(tty), ldata->process_char_map);
1559 set_bit(INTR_CHAR(tty), ldata->process_char_map);
1560 set_bit(QUIT_CHAR(tty), ldata->process_char_map);
1561 set_bit(SUSP_CHAR(tty), ldata->process_char_map);
1563 clear_bit(__DISABLED_CHAR, ldata->process_char_map);
1565 ldata->real_raw = 0;
1568 if ((I_IGNBRK(tty) || (!I_BRKINT(tty) && !I_PARMRK(tty))) &&
1569 (I_IGNPAR(tty) || !I_INPCK(tty)) &&
1570 (tty->driver->flags & TTY_DRIVER_REAL_RAW))
1571 ldata->real_raw = 1;
1573 ldata->real_raw = 0;
1575 n_tty_set_room(tty);
1576 /* The termios change make the tty ready for I/O */
1577 wake_up_interruptible(&tty->write_wait);
1578 wake_up_interruptible(&tty->read_wait);
1582 * n_tty_close - close the ldisc for this tty
1585 * Called from the terminal layer when this line discipline is
1586 * being shut down, either because of a close or becsuse of a
1587 * discipline change. The function will not be called while other
1588 * ldisc methods are in progress.
1591 static void n_tty_close(struct tty_struct *tty)
1593 struct n_tty_data *ldata = tty->disc_data;
1596 n_tty_packet_mode_flush(tty);
1598 kfree(ldata->read_buf);
1599 kfree(ldata->echo_buf);
1601 tty->disc_data = NULL;
1605 * n_tty_open - open an ldisc
1606 * @tty: terminal to open
1608 * Called when this line discipline is being attached to the
1609 * terminal device. Can sleep. Called serialized so that no
1610 * other events will occur in parallel. No further open will occur
1614 static int n_tty_open(struct tty_struct *tty)
1616 struct n_tty_data *ldata;
1618 ldata = kzalloc(sizeof(*ldata), GFP_KERNEL);
1622 ldata->overrun_time = jiffies;
1623 mutex_init(&ldata->atomic_read_lock);
1624 mutex_init(&ldata->output_lock);
1625 mutex_init(&ldata->echo_lock);
1626 raw_spin_lock_init(&ldata->read_lock);
1628 /* These are ugly. Currently a malloc failure here can panic */
1629 ldata->read_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1630 ldata->echo_buf = kzalloc(N_TTY_BUF_SIZE, GFP_KERNEL);
1631 if (!ldata->read_buf || !ldata->echo_buf)
1634 tty->disc_data = ldata;
1635 reset_buffer_flags(tty->disc_data);
1637 tty->minimum_to_wake = 1;
1639 /* indicate buffer work may resume */
1640 clear_bit(TTY_LDISC_HALTED, &tty->flags);
1641 n_tty_set_termios(tty, NULL);
1642 tty_unthrottle(tty);
1646 kfree(ldata->read_buf);
1647 kfree(ldata->echo_buf);
1653 static inline int input_available_p(struct tty_struct *tty, int amt)
1655 struct n_tty_data *ldata = tty->disc_data;
1657 tty_flush_to_ldisc(tty);
1658 if (ldata->icanon && !L_EXTPROC(tty)) {
1659 if (ldata->canon_data)
1661 } else if (ldata->read_cnt >= (amt ? amt : 1))
1668 * copy_from_read_buf - copy read data directly
1669 * @tty: terminal device
1673 * Helper function to speed up n_tty_read. It is only called when
1674 * ICANON is off; it copies characters straight from the tty queue to
1675 * user space directly. It can be profitably called twice; once to
1676 * drain the space from the tail pointer to the (physical) end of the
1677 * buffer, and once to drain the space from the (physical) beginning of
1678 * the buffer to head pointer.
1680 * Called under the ldata->atomic_read_lock sem
1684 static int copy_from_read_buf(struct tty_struct *tty,
1685 unsigned char __user **b,
1689 struct n_tty_data *ldata = tty->disc_data;
1692 unsigned long flags;
1696 raw_spin_lock_irqsave(&ldata->read_lock, flags);
1697 n = min(ldata->read_cnt, N_TTY_BUF_SIZE - ldata->read_tail);
1699 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
1701 retval = copy_to_user(*b, &ldata->read_buf[ldata->read_tail], n);
1704 ldata->read_buf[ldata->read_tail] == EOF_CHAR(tty);
1705 tty_audit_add_data(tty, &ldata->read_buf[ldata->read_tail], n,
1707 raw_spin_lock_irqsave(&ldata->read_lock, flags);
1708 ldata->read_tail = (ldata->read_tail + n) & (N_TTY_BUF_SIZE-1);
1709 ldata->read_cnt -= n;
1710 /* Turn single EOF into zero-length read */
1711 if (L_EXTPROC(tty) && ldata->icanon && is_eof && !ldata->read_cnt)
1713 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
1720 extern ssize_t redirected_tty_write(struct file *, const char __user *,
1724 * job_control - check job control
1726 * @file: file handle
1728 * Perform job control management checks on this file/tty descriptor
1729 * and if appropriate send any needed signals and return a negative
1730 * error code if action should be taken.
1732 * Locking: redirected write test is safe
1733 * current->signal->tty check is safe
1734 * ctrl_lock to safely reference tty->pgrp
1737 static int job_control(struct tty_struct *tty, struct file *file)
1739 /* Job control check -- must be done at start and after
1740 every sleep (POSIX.1 7.1.1.4). */
1741 /* NOTE: not yet done after every sleep pending a thorough
1742 check of the logic of this change. -- jlc */
1743 /* don't stop on /dev/console */
1744 if (file->f_op->write == redirected_tty_write ||
1745 current->signal->tty != tty)
1748 spin_lock_irq(&tty->ctrl_lock);
1750 printk(KERN_ERR "n_tty_read: no tty->pgrp!\n");
1751 else if (task_pgrp(current) != tty->pgrp) {
1752 spin_unlock_irq(&tty->ctrl_lock);
1753 if (is_ignored(SIGTTIN) || is_current_pgrp_orphaned())
1755 kill_pgrp(task_pgrp(current), SIGTTIN, 1);
1756 set_thread_flag(TIF_SIGPENDING);
1757 return -ERESTARTSYS;
1759 spin_unlock_irq(&tty->ctrl_lock);
1765 * n_tty_read - read function for tty
1767 * @file: file object
1768 * @buf: userspace buffer pointer
1771 * Perform reads for the line discipline. We are guaranteed that the
1772 * line discipline will not be closed under us but we may get multiple
1773 * parallel readers and must handle this ourselves. We may also get
1774 * a hangup. Always called in user context, may sleep.
1776 * This code must be sure never to sleep through a hangup.
1779 static ssize_t n_tty_read(struct tty_struct *tty, struct file *file,
1780 unsigned char __user *buf, size_t nr)
1782 struct n_tty_data *ldata = tty->disc_data;
1783 unsigned char __user *b = buf;
1784 DECLARE_WAITQUEUE(wait, current);
1790 unsigned long flags;
1794 c = job_control(tty, file);
1799 timeout = MAX_SCHEDULE_TIMEOUT;
1800 if (!ldata->icanon) {
1801 time = (HZ / 10) * TIME_CHAR(tty);
1802 minimum = MIN_CHAR(tty);
1805 tty->minimum_to_wake = 1;
1806 else if (!waitqueue_active(&tty->read_wait) ||
1807 (tty->minimum_to_wake > minimum))
1808 tty->minimum_to_wake = minimum;
1815 tty->minimum_to_wake = minimum = 1;
1820 * Internal serialization of reads.
1822 if (file->f_flags & O_NONBLOCK) {
1823 if (!mutex_trylock(&ldata->atomic_read_lock))
1826 if (mutex_lock_interruptible(&ldata->atomic_read_lock))
1827 return -ERESTARTSYS;
1829 packet = tty->packet;
1831 add_wait_queue(&tty->read_wait, &wait);
1833 /* First test for status change. */
1834 if (packet && tty->link->ctrl_status) {
1838 spin_lock_irqsave(&tty->link->ctrl_lock, flags);
1839 cs = tty->link->ctrl_status;
1840 tty->link->ctrl_status = 0;
1841 spin_unlock_irqrestore(&tty->link->ctrl_lock, flags);
1842 if (tty_put_user(tty, cs, b++)) {
1850 /* This statement must be first before checking for input
1851 so that any interrupt will set the state back to
1853 set_current_state(TASK_INTERRUPTIBLE);
1855 if (((minimum - (b - buf)) < tty->minimum_to_wake) &&
1856 ((minimum - (b - buf)) >= 1))
1857 tty->minimum_to_wake = (minimum - (b - buf));
1859 if (!input_available_p(tty, 0)) {
1860 if (test_bit(TTY_OTHER_CLOSED, &tty->flags)) {
1864 if (tty_hung_up_p(file))
1868 if (file->f_flags & O_NONBLOCK) {
1872 if (signal_pending(current)) {
1873 retval = -ERESTARTSYS;
1876 /* FIXME: does n_tty_set_room need locking ? */
1877 n_tty_set_room(tty);
1878 timeout = schedule_timeout(timeout);
1881 __set_current_state(TASK_RUNNING);
1883 /* Deal with packet mode. */
1884 if (packet && b == buf) {
1885 if (tty_put_user(tty, TIOCPKT_DATA, b++)) {
1893 if (ldata->icanon && !L_EXTPROC(tty)) {
1894 /* N.B. avoid overrun if nr == 0 */
1895 raw_spin_lock_irqsave(&ldata->read_lock, flags);
1896 while (nr && ldata->read_cnt) {
1899 eol = test_and_clear_bit(ldata->read_tail,
1901 c = ldata->read_buf[ldata->read_tail];
1902 ldata->read_tail = ((ldata->read_tail+1) &
1903 (N_TTY_BUF_SIZE-1));
1906 /* this test should be redundant:
1907 * we shouldn't be reading data if
1910 if (--ldata->canon_data < 0)
1911 ldata->canon_data = 0;
1913 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
1915 if (!eol || (c != __DISABLED_CHAR)) {
1916 if (tty_put_user(tty, c, b++)) {
1919 raw_spin_lock_irqsave(&ldata->read_lock, flags);
1925 tty_audit_push(tty);
1926 raw_spin_lock_irqsave(&ldata->read_lock, flags);
1929 raw_spin_lock_irqsave(&ldata->read_lock, flags);
1931 raw_spin_unlock_irqrestore(&ldata->read_lock, flags);
1936 /* The copy function takes the read lock and handles
1937 locking internally for this case */
1938 uncopied = copy_from_read_buf(tty, &b, &nr);
1939 uncopied += copy_from_read_buf(tty, &b, &nr);
1946 /* If there is enough space in the read buffer now, let the
1947 * low-level driver know. We use n_tty_chars_in_buffer() to
1948 * check the buffer, as it now knows about canonical mode.
1949 * Otherwise, if the driver is throttled and the line is
1950 * longer than TTY_THRESHOLD_UNTHROTTLE in canonical mode,
1951 * we won't get any more characters.
1954 tty_set_flow_change(tty, TTY_UNTHROTTLE_SAFE);
1955 if (n_tty_chars_in_buffer(tty) > TTY_THRESHOLD_UNTHROTTLE)
1959 n_tty_set_room(tty);
1960 if (!tty_unthrottle_safe(tty))
1963 __tty_set_flow_change(tty, 0);
1965 if (b - buf >= minimum)
1970 mutex_unlock(&ldata->atomic_read_lock);
1971 remove_wait_queue(&tty->read_wait, &wait);
1973 if (!waitqueue_active(&tty->read_wait))
1974 tty->minimum_to_wake = minimum;
1976 __set_current_state(TASK_RUNNING);
1981 clear_bit(TTY_PUSH, &tty->flags);
1982 } else if (test_and_clear_bit(TTY_PUSH, &tty->flags))
1985 n_tty_set_room(tty);
1990 * n_tty_write - write function for tty
1992 * @file: file object
1993 * @buf: userspace buffer pointer
1996 * Write function of the terminal device. This is serialized with
1997 * respect to other write callers but not to termios changes, reads
1998 * and other such events. Since the receive code will echo characters,
1999 * thus calling driver write methods, the output_lock is used in
2000 * the output processing functions called here as well as in the
2001 * echo processing function to protect the column state and space
2002 * left in the buffer.
2004 * This code must be sure never to sleep through a hangup.
2006 * Locking: output_lock to protect column state and space left
2007 * (note that the process_output*() functions take this
2011 static ssize_t n_tty_write(struct tty_struct *tty, struct file *file,
2012 const unsigned char *buf, size_t nr)
2014 const unsigned char *b = buf;
2015 DECLARE_WAITQUEUE(wait, current);
2019 /* Job control check -- must be done at start (POSIX.1 7.1.1.4). */
2020 if (L_TOSTOP(tty) && file->f_op->write != redirected_tty_write) {
2021 retval = tty_check_change(tty);
2026 /* Write out any echoed characters that are still pending */
2027 process_echoes(tty);
2029 add_wait_queue(&tty->write_wait, &wait);
2031 set_current_state(TASK_INTERRUPTIBLE);
2032 if (signal_pending(current)) {
2033 retval = -ERESTARTSYS;
2036 if (tty_hung_up_p(file) || (tty->link && !tty->link->count)) {
2040 if (O_OPOST(tty) && !(test_bit(TTY_HW_COOK_OUT, &tty->flags))) {
2042 ssize_t num = process_output_block(tty, b, nr);
2054 if (process_output(c, tty) < 0)
2058 if (tty->ops->flush_chars)
2059 tty->ops->flush_chars(tty);
2062 c = tty->ops->write(tty, b, nr);
2075 if (file->f_flags & O_NONBLOCK) {
2082 __set_current_state(TASK_RUNNING);
2083 remove_wait_queue(&tty->write_wait, &wait);
2084 if (b - buf != nr && tty->fasync)
2085 set_bit(TTY_DO_WRITE_WAKEUP, &tty->flags);
2086 return (b - buf) ? b - buf : retval;
2090 * n_tty_poll - poll method for N_TTY
2091 * @tty: terminal device
2092 * @file: file accessing it
2095 * Called when the line discipline is asked to poll() for data or
2096 * for special events. This code is not serialized with respect to
2097 * other events save open/close.
2099 * This code must be sure never to sleep through a hangup.
2100 * Called without the kernel lock held - fine
2103 static unsigned int n_tty_poll(struct tty_struct *tty, struct file *file,
2106 unsigned int mask = 0;
2108 poll_wait(file, &tty->read_wait, wait);
2109 poll_wait(file, &tty->write_wait, wait);
2110 if (input_available_p(tty, TIME_CHAR(tty) ? 0 : MIN_CHAR(tty)))
2111 mask |= POLLIN | POLLRDNORM;
2112 if (tty->packet && tty->link->ctrl_status)
2113 mask |= POLLPRI | POLLIN | POLLRDNORM;
2114 if (test_bit(TTY_OTHER_CLOSED, &tty->flags))
2116 if (tty_hung_up_p(file))
2118 if (!(mask & (POLLHUP | POLLIN | POLLRDNORM))) {
2119 if (MIN_CHAR(tty) && !TIME_CHAR(tty))
2120 tty->minimum_to_wake = MIN_CHAR(tty);
2122 tty->minimum_to_wake = 1;
2124 if (tty->ops->write && !tty_is_writelocked(tty) &&
2125 tty_chars_in_buffer(tty) < WAKEUP_CHARS &&
2126 tty_write_room(tty) > 0)
2127 mask |= POLLOUT | POLLWRNORM;
2131 static unsigned long inq_canon(struct n_tty_data *ldata)
2135 if (!ldata->canon_data)
2137 head = ldata->canon_head;
2138 tail = ldata->read_tail;
2139 nr = (head - tail) & (N_TTY_BUF_SIZE-1);
2140 /* Skip EOF-chars.. */
2141 while (head != tail) {
2142 if (test_bit(tail, ldata->read_flags) &&
2143 ldata->read_buf[tail] == __DISABLED_CHAR)
2145 tail = (tail+1) & (N_TTY_BUF_SIZE-1);
2150 static int n_tty_ioctl(struct tty_struct *tty, struct file *file,
2151 unsigned int cmd, unsigned long arg)
2153 struct n_tty_data *ldata = tty->disc_data;
2158 return put_user(tty_chars_in_buffer(tty), (int __user *) arg);
2160 /* FIXME: Locking */
2161 retval = ldata->read_cnt;
2163 retval = inq_canon(ldata);
2164 return put_user(retval, (unsigned int __user *) arg);
2166 return n_tty_ioctl_helper(tty, file, cmd, arg);
2170 struct tty_ldisc_ops tty_ldisc_N_TTY = {
2171 .magic = TTY_LDISC_MAGIC,
2174 .close = n_tty_close,
2175 .flush_buffer = n_tty_flush_buffer,
2176 .chars_in_buffer = n_tty_chars_in_buffer,
2178 .write = n_tty_write,
2179 .ioctl = n_tty_ioctl,
2180 .set_termios = n_tty_set_termios,
2182 .receive_buf = n_tty_receive_buf,
2183 .write_wakeup = n_tty_write_wakeup
2187 * n_tty_inherit_ops - inherit N_TTY methods
2188 * @ops: struct tty_ldisc_ops where to save N_TTY methods
2190 * Enables a 'subclass' line discipline to 'inherit' N_TTY
2194 void n_tty_inherit_ops(struct tty_ldisc_ops *ops)
2196 *ops = tty_ldisc_N_TTY;
2198 ops->refcount = ops->flags = 0;
2200 EXPORT_SYMBOL_GPL(n_tty_inherit_ops);