tty_ioctl.c 31.4 KB
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700 701 702 703 704 705 706 707 708 709 710 711 712 713 714 715 716 717 718 719 720 721 722 723 724 725 726 727 728 729 730 731 732 733 734 735 736 737 738 739 740 741 742 743 744 745 746 747 748 749 750 751 752 753 754 755 756 757 758 759 760 761 762 763 764 765 766 767 768 769 770 771 772 773 774 775 776 777 778 779 780 781 782 783 784 785 786 787 788 789 790 791 792 793 794 795 796 797 798 799 800 801 802 803 804 805 806 807 808 809 810 811 812 813 814 815 816 817 818 819 820 821 822 823 824 825 826 827 828 829 830 831 832 833 834 835 836 837 838 839 840 841 842 843 844 845 846 847 848 849 850 851 852 853 854 855 856 857 858 859 860 861 862 863 864 865 866 867 868 869 870 871 872 873 874 875 876 877 878 879 880 881 882 883 884 885 886 887 888 889 890 891 892 893 894 895 896 897 898 899 900 901 902 903 904 905 906 907 908 909 910 911 912 913 914 915 916 917 918 919 920 921 922 923 924 925 926 927 928 929 930 931 932 933 934 935 936 937 938 939 940 941 942 943 944 945 946 947 948 949 950 951 952 953 954 955 956 957 958 959 960 961 962 963 964 965 966 967 968 969 970 971 972 973 974 975 976 977 978 979 980 981 982 983 984 985 986 987 988 989 990 991 992 993 994 995 996 997 998 999 1000 1001 1002 1003 1004 1005 1006 1007 1008 1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064 1065 1066 1067 1068 1069 1070 1071 1072 1073 1074 1075 1076 1077 1078 1079 1080 1081 1082 1083 1084 1085 1086 1087 1088 1089 1090 1091 1092 1093 1094 1095 1096 1097 1098 1099 1100 1101 1102 1103 1104 1105 1106 1107 1108 1109 1110 1111 1112 1113 1114 1115 1116 1117 1118 1119 1120 1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176 1177 1178 1179 1180 1181 1182 1183 1184 1185 1186 1187 1188 1189 1190 1191 1192 1193 1194 1195 1196 1197 1198 1199 1200 1201 1202 1203 1204 1205 1206 1207 1208 1209 1210 1211 1212 1213 1214 1215 1216 1217 1218 1219 1220 1221 1222 1223 1224 1225 1226 1227 1228 1229
/*
 *  Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
 *
 * Modified by Fred N. van Kempen, 01/29/93, to add line disciplines
 * which can be dynamically activated and de-activated by the line
 * discipline handling modules (like SLIP).
 */

#include <linux/types.h>
#include <linux/termios.h>
#include <linux/errno.h>
#include <linux/sched.h>
#include <linux/kernel.h>
#include <linux/major.h>
#include <linux/tty.h>
#include <linux/fcntl.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/bitops.h>
#include <linux/mutex.h>
#include <linux/compat.h>

#include <asm/io.h>
#include <asm/uaccess.h>

#undef TTY_DEBUG_WAIT_UNTIL_SENT

#undef	DEBUG

/*
 * Internal flag options for termios setting behavior
 */
#define TERMIOS_FLUSH	1
#define TERMIOS_WAIT	2
#define TERMIOS_TERMIO	4
#define TERMIOS_OLD	8


/**
 *	tty_chars_in_buffer	-	characters pending
 *	@tty: terminal
 *
 *	Return the number of bytes of data in the device private
 *	output queue. If no private method is supplied there is assumed
 *	to be no queue on the device.
 */

int tty_chars_in_buffer(struct tty_struct *tty)
{
	if (tty->ops->chars_in_buffer)
		return tty->ops->chars_in_buffer(tty);
	else
		return 0;
}
EXPORT_SYMBOL(tty_chars_in_buffer);

/**
 *	tty_write_room		-	write queue space
 *	@tty: terminal
 *
 *	Return the number of bytes that can be queued to this device
 *	at the present time. The result should be treated as a guarantee
 *	and the driver cannot offer a value it later shrinks by more than
 *	the number of bytes written. If no method is provided 2K is always
 *	returned and data may be lost as there will be no flow control.
 */
 
int tty_write_room(struct tty_struct *tty)
{
	if (tty->ops->write_room)
		return tty->ops->write_room(tty);
	return 2048;
}
EXPORT_SYMBOL(tty_write_room);

/**
 *	tty_driver_flush_buffer	-	discard internal buffer
 *	@tty: terminal
 *
 *	Discard the internal output buffer for this device. If no method
 *	is provided then either the buffer cannot be hardware flushed or
 *	there is no buffer driver side.
 */
void tty_driver_flush_buffer(struct tty_struct *tty)
{
	if (tty->ops->flush_buffer)
		tty->ops->flush_buffer(tty);
}
EXPORT_SYMBOL(tty_driver_flush_buffer);

/**
 *	tty_throttle		-	flow control
 *	@tty: terminal
 *
 *	Indicate that a tty should stop transmitting data down the stack.
 *	Takes the termios rwsem to protect against parallel throttle/unthrottle
 *	and also to ensure the driver can consistently reference its own
 *	termios data at this point when implementing software flow control.
 */

void tty_throttle(struct tty_struct *tty)
{
	down_write(&tty->termios_rwsem);
	/* check TTY_THROTTLED first so it indicates our state */
	if (!test_and_set_bit(TTY_THROTTLED, &tty->flags) &&
	    tty->ops->throttle)
		tty->ops->throttle(tty);
	tty->flow_change = 0;
	up_write(&tty->termios_rwsem);
}
EXPORT_SYMBOL(tty_throttle);

/**
 *	tty_unthrottle		-	flow control
 *	@tty: terminal
 *
 *	Indicate that a tty may continue transmitting data down the stack.
 *	Takes the termios rwsem to protect against parallel throttle/unthrottle
 *	and also to ensure the driver can consistently reference its own
 *	termios data at this point when implementing software flow control.
 *
 *	Drivers should however remember that the stack can issue a throttle,
 *	then change flow control method, then unthrottle.
 */

void tty_unthrottle(struct tty_struct *tty)
{
	down_write(&tty->termios_rwsem);
	if (test_and_clear_bit(TTY_THROTTLED, &tty->flags) &&
	    tty->ops->unthrottle)
		tty->ops->unthrottle(tty);
	tty->flow_change = 0;
	up_write(&tty->termios_rwsem);
}
EXPORT_SYMBOL(tty_unthrottle);

/**
 *	tty_throttle_safe	-	flow control
 *	@tty: terminal
 *
 *	Similar to tty_throttle() but will only attempt throttle
 *	if tty->flow_change is TTY_THROTTLE_SAFE. Prevents an accidental
 *	throttle due to race conditions when throttling is conditional
 *	on factors evaluated prior to throttling.
 *
 *	Returns 0 if tty is throttled (or was already throttled)
 */

int tty_throttle_safe(struct tty_struct *tty)
{
	int ret = 0;

	mutex_lock(&tty->throttle_mutex);
	if (!test_bit(TTY_THROTTLED, &tty->flags)) {
		if (tty->flow_change != TTY_THROTTLE_SAFE)
			ret = 1;
		else {
			set_bit(TTY_THROTTLED, &tty->flags);
			if (tty->ops->throttle)
				tty->ops->throttle(tty);
		}
	}
	mutex_unlock(&tty->throttle_mutex);

	return ret;
}

/**
 *	tty_unthrottle_safe	-	flow control
 *	@tty: terminal
 *
 *	Similar to tty_unthrottle() but will only attempt unthrottle
 *	if tty->flow_change is TTY_UNTHROTTLE_SAFE. Prevents an accidental
 *	unthrottle due to race conditions when unthrottling is conditional
 *	on factors evaluated prior to unthrottling.
 *
 *	Returns 0 if tty is unthrottled (or was already unthrottled)
 */

int tty_unthrottle_safe(struct tty_struct *tty)
{
	int ret = 0;

	mutex_lock(&tty->throttle_mutex);
	if (test_bit(TTY_THROTTLED, &tty->flags)) {
		if (tty->flow_change != TTY_UNTHROTTLE_SAFE)
			ret = 1;
		else {
			clear_bit(TTY_THROTTLED, &tty->flags);
			if (tty->ops->unthrottle)
				tty->ops->unthrottle(tty);
		}
	}
	mutex_unlock(&tty->throttle_mutex);

	return ret;
}

/**
 *	tty_wait_until_sent	-	wait for I/O to finish
 *	@tty: tty we are waiting for
 *	@timeout: how long we will wait
 *
 *	Wait for characters pending in a tty driver to hit the wire, or
 *	for a timeout to occur (eg due to flow control)
 *
 *	Locking: none
 */

void tty_wait_until_sent(struct tty_struct *tty, long timeout)
{
#ifdef TTY_DEBUG_WAIT_UNTIL_SENT
	char buf[64];

	printk(KERN_DEBUG "%s wait until sent...\n", tty_name(tty, buf));
#endif
	if (!timeout)
		timeout = MAX_SCHEDULE_TIMEOUT;
	if (wait_event_interruptible_timeout(tty->write_wait,
			!tty_chars_in_buffer(tty), timeout) >= 0) {
		if (tty->ops->wait_until_sent)
			tty->ops->wait_until_sent(tty, timeout);
	}
}
EXPORT_SYMBOL(tty_wait_until_sent);


/*
 *		Termios Helper Methods
 */

static void unset_locked_termios(struct ktermios *termios,
				 struct ktermios *old,
				 struct ktermios *locked)
{
	int	i;

#define NOSET_MASK(x, y, z) (x = ((x) & ~(z)) | ((y) & (z)))

	if (!locked) {
		printk(KERN_WARNING "Warning?!? termios_locked is NULL.\n");
		return;
	}

	NOSET_MASK(termios->c_iflag, old->c_iflag, locked->c_iflag);
	NOSET_MASK(termios->c_oflag, old->c_oflag, locked->c_oflag);
	NOSET_MASK(termios->c_cflag, old->c_cflag, locked->c_cflag);
	NOSET_MASK(termios->c_lflag, old->c_lflag, locked->c_lflag);
	termios->c_line = locked->c_line ? old->c_line : termios->c_line;
	for (i = 0; i < NCCS; i++)
		termios->c_cc[i] = locked->c_cc[i] ?
			old->c_cc[i] : termios->c_cc[i];
	/* FIXME: What should we do for i/ospeed */
}

/*
 * Routine which returns the baud rate of the tty
 *
 * Note that the baud_table needs to be kept in sync with the
 * include/asm/termbits.h file.
 */
static const speed_t baud_table[] = {
	0, 50, 75, 110, 134, 150, 200, 300, 600, 1200, 1800, 2400, 4800,
	9600, 19200, 38400, 57600, 115200, 230400, 460800,
#ifdef __sparc__
	76800, 153600, 307200, 614400, 921600
#else
	500000, 576000, 921600, 1000000, 1152000, 1500000, 2000000,
	2500000, 3000000, 3500000, 4000000
#endif
};

#ifndef __sparc__
static const tcflag_t baud_bits[] = {
	B0, B50, B75, B110, B134, B150, B200, B300, B600,
	B1200, B1800, B2400, B4800, B9600, B19200, B38400,
	B57600, B115200, B230400, B460800, B500000, B576000,
	B921600, B1000000, B1152000, B1500000, B2000000, B2500000,
	B3000000, B3500000, B4000000
};
#else
static const tcflag_t baud_bits[] = {
	B0, B50, B75, B110, B134, B150, B200, B300, B600,
	B1200, B1800, B2400, B4800, B9600, B19200, B38400,
	B57600, B115200, B230400, B460800, B76800, B153600,
	B307200, B614400, B921600
};
#endif

static int n_baud_table = ARRAY_SIZE(baud_table);

/**
 *	tty_termios_baud_rate
 *	@termios: termios structure
 *
 *	Convert termios baud rate data into a speed. This should be called
 *	with the termios lock held if this termios is a terminal termios
 *	structure. May change the termios data. Device drivers can call this
 *	function but should use ->c_[io]speed directly as they are updated.
 *
 *	Locking: none
 */

speed_t tty_termios_baud_rate(struct ktermios *termios)
{
	unsigned int cbaud;

	cbaud = termios->c_cflag & CBAUD;

#ifdef BOTHER
	/* Magic token for arbitrary speed via c_ispeed/c_ospeed */
	if (cbaud == BOTHER)
		return termios->c_ospeed;
#endif
	if (cbaud & CBAUDEX) {
		cbaud &= ~CBAUDEX;

		if (cbaud < 1 || cbaud + 15 > n_baud_table)
			termios->c_cflag &= ~CBAUDEX;
		else
			cbaud += 15;
	}
	return baud_table[cbaud];
}
EXPORT_SYMBOL(tty_termios_baud_rate);

/**
 *	tty_termios_input_baud_rate
 *	@termios: termios structure
 *
 *	Convert termios baud rate data into a speed. This should be called
 *	with the termios lock held if this termios is a terminal termios
 *	structure. May change the termios data. Device drivers can call this
 *	function but should use ->c_[io]speed directly as they are updated.
 *
 *	Locking: none
 */

speed_t tty_termios_input_baud_rate(struct ktermios *termios)
{
#ifdef IBSHIFT
	unsigned int cbaud = (termios->c_cflag >> IBSHIFT) & CBAUD;

	if (cbaud == B0)
		return tty_termios_baud_rate(termios);

	/* Magic token for arbitrary speed via c_ispeed*/
	if (cbaud == BOTHER)
		return termios->c_ispeed;

	if (cbaud & CBAUDEX) {
		cbaud &= ~CBAUDEX;

		if (cbaud < 1 || cbaud + 15 > n_baud_table)
			termios->c_cflag &= ~(CBAUDEX << IBSHIFT);
		else
			cbaud += 15;
	}
	return baud_table[cbaud];
#else
	return tty_termios_baud_rate(termios);
#endif
}
EXPORT_SYMBOL(tty_termios_input_baud_rate);

/**
 *	tty_termios_encode_baud_rate
 *	@termios: ktermios structure holding user requested state
 *	@ispeed: input speed
 *	@ospeed: output speed
 *
 *	Encode the speeds set into the passed termios structure. This is
 *	used as a library helper for drivers so that they can report back
 *	the actual speed selected when it differs from the speed requested
 *
 *	For maximal back compatibility with legacy SYS5/POSIX *nix behaviour
 *	we need to carefully set the bits when the user does not get the
 *	desired speed. We allow small margins and preserve as much of possible
 *	of the input intent to keep compatibility.
 *
 *	Locking: Caller should hold termios lock. This is already held
 *	when calling this function from the driver termios handler.
 *
 *	The ifdefs deal with platforms whose owners have yet to update them
 *	and will all go away once this is done.
 */

void tty_termios_encode_baud_rate(struct ktermios *termios,
				  speed_t ibaud, speed_t obaud)
{
	int i = 0;
	int ifound = -1, ofound = -1;
	int iclose = ibaud/50, oclose = obaud/50;
	int ibinput = 0;

	if (obaud == 0)			/* CD dropped 		  */
		ibaud = 0;		/* Clear ibaud to be sure */

	termios->c_ispeed = ibaud;
	termios->c_ospeed = obaud;

#ifdef BOTHER
	/* If the user asked for a precise weird speed give a precise weird
	   answer. If they asked for a Bfoo speed they many have problems
	   digesting non-exact replies so fuzz a bit */

	if ((termios->c_cflag & CBAUD) == BOTHER)
		oclose = 0;
	if (((termios->c_cflag >> IBSHIFT) & CBAUD) == BOTHER)
		iclose = 0;
	if ((termios->c_cflag >> IBSHIFT) & CBAUD)
		ibinput = 1;	/* An input speed was specified */
#endif
	termios->c_cflag &= ~CBAUD;

	/*
	 *	Our goal is to find a close match to the standard baud rate
	 *	returned. Walk the baud rate table and if we get a very close
	 *	match then report back the speed as a POSIX Bxxxx value by
	 *	preference
	 */

	do {
		if (obaud - oclose <= baud_table[i] &&
		    obaud + oclose >= baud_table[i]) {
			termios->c_cflag |= baud_bits[i];
			ofound = i;
		}
		if (ibaud - iclose <= baud_table[i] &&
		    ibaud + iclose >= baud_table[i]) {
			/* For the case input == output don't set IBAUD bits
			   if the user didn't do so */
			if (ofound == i && !ibinput)
				ifound  = i;
#ifdef IBSHIFT
			else {
				ifound = i;
				termios->c_cflag |= (baud_bits[i] << IBSHIFT);
			}
#endif
		}
	} while (++i < n_baud_table);

	/*
	 *	If we found no match then use BOTHER if provided or warn
	 *	the user their platform maintainer needs to wake up if not.
	 */
#ifdef BOTHER
	if (ofound == -1)
		termios->c_cflag |= BOTHER;
	/* Set exact input bits only if the input and output differ or the
	   user already did */
	if (ifound == -1 && (ibaud != obaud || ibinput))
		termios->c_cflag |= (BOTHER << IBSHIFT);
#else
	if (ifound == -1 || ofound == -1) {
		printk_once(KERN_WARNING "tty: Unable to return correct "
			  "speed data as your architecture needs updating.\n");
	}
#endif
}
EXPORT_SYMBOL_GPL(tty_termios_encode_baud_rate);

/**
 *	tty_encode_baud_rate		-	set baud rate of the tty
 *	@ibaud: input baud rate
 *	@obad: output baud rate
 *
 *	Update the current termios data for the tty with the new speed
 *	settings. The caller must hold the termios_rwsem for the tty in
 *	question.
 */

void tty_encode_baud_rate(struct tty_struct *tty, speed_t ibaud, speed_t obaud)
{
	tty_termios_encode_baud_rate(&tty->termios, ibaud, obaud);
}
EXPORT_SYMBOL_GPL(tty_encode_baud_rate);

/**
 *	tty_termios_copy_hw	-	copy hardware settings
 *	@new: New termios
 *	@old: Old termios
 *
 *	Propagate the hardware specific terminal setting bits from
 *	the old termios structure to the new one. This is used in cases
 *	where the hardware does not support reconfiguration or as a helper
 *	in some cases where only minimal reconfiguration is supported
 */

void tty_termios_copy_hw(struct ktermios *new, struct ktermios *old)
{
	/* The bits a dumb device handles in software. Smart devices need
	   to always provide a set_termios method */
	new->c_cflag &= HUPCL | CREAD | CLOCAL;
	new->c_cflag |= old->c_cflag & ~(HUPCL | CREAD | CLOCAL);
	new->c_ispeed = old->c_ispeed;
	new->c_ospeed = old->c_ospeed;
}
EXPORT_SYMBOL(tty_termios_copy_hw);

/**
 *	tty_termios_hw_change	-	check for setting change
 *	@a: termios
 *	@b: termios to compare
 *
 *	Check if any of the bits that affect a dumb device have changed
 *	between the two termios structures, or a speed change is needed.
 */

int tty_termios_hw_change(struct ktermios *a, struct ktermios *b)
{
	if (a->c_ispeed != b->c_ispeed || a->c_ospeed != b->c_ospeed)
		return 1;
	if ((a->c_cflag ^ b->c_cflag) & ~(HUPCL | CREAD | CLOCAL))
		return 1;
	return 0;
}
EXPORT_SYMBOL(tty_termios_hw_change);

/**
 *	tty_set_termios		-	update termios values
 *	@tty: tty to update
 *	@new_termios: desired new value
 *
 *	Perform updates to the termios values set on this terminal. There
 *	is a bit of layering violation here with n_tty in terms of the
 *	internal knowledge of this function.
 *
 *	Locking: termios_rwsem
 */

int tty_set_termios(struct tty_struct *tty, struct ktermios *new_termios)
{
	struct ktermios old_termios;
	struct tty_ldisc *ld;
	unsigned long flags;

	/*
	 *	Perform the actual termios internal changes under lock.
	 */


	/* FIXME: we need to decide on some locking/ordering semantics
	   for the set_termios notification eventually */
	down_write(&tty->termios_rwsem);
	old_termios = tty->termios;
	tty->termios = *new_termios;
	unset_locked_termios(&tty->termios, &old_termios, &tty->termios_locked);

	/* See if packet mode change of state. */
	if (tty->link && tty->link->packet) {
		int extproc = (old_termios.c_lflag & EXTPROC) |
				(tty->termios.c_lflag & EXTPROC);
		int old_flow = ((old_termios.c_iflag & IXON) &&
				(old_termios.c_cc[VSTOP] == '\023') &&
				(old_termios.c_cc[VSTART] == '\021'));
		int new_flow = (I_IXON(tty) &&
				STOP_CHAR(tty) == '\023' &&
				START_CHAR(tty) == '\021');
		if ((old_flow != new_flow) || extproc) {
			spin_lock_irqsave(&tty->ctrl_lock, flags);
			if (old_flow != new_flow) {
				tty->ctrl_status &= ~(TIOCPKT_DOSTOP | TIOCPKT_NOSTOP);
				if (new_flow)
					tty->ctrl_status |= TIOCPKT_DOSTOP;
				else
					tty->ctrl_status |= TIOCPKT_NOSTOP;
			}
			if (extproc)
				tty->ctrl_status |= TIOCPKT_IOCTL;
			spin_unlock_irqrestore(&tty->ctrl_lock, flags);
			wake_up_interruptible(&tty->link->read_wait);
		}
	}

	if (tty->ops->set_termios)
		(*tty->ops->set_termios)(tty, &old_termios);
	else
		tty_termios_copy_hw(&tty->termios, &old_termios);

	ld = tty_ldisc_ref(tty);
	if (ld != NULL) {
		if (ld->ops->set_termios)
			(ld->ops->set_termios)(tty, &old_termios);
		tty_ldisc_deref(ld);
	}
	up_write(&tty->termios_rwsem);
	return 0;
}
EXPORT_SYMBOL_GPL(tty_set_termios);

/**
 *	set_termios		-	set termios values for a tty
 *	@tty: terminal device
 *	@arg: user data
 *	@opt: option information
 *
 *	Helper function to prepare termios data and run necessary other
 *	functions before using tty_set_termios to do the actual changes.
 *
 *	Locking:
 *		Called functions take ldisc and termios_rwsem locks
 */

static int set_termios(struct tty_struct *tty, void __user *arg, int opt)
{
	struct ktermios tmp_termios;
	struct tty_ldisc *ld;
	int retval = tty_check_change(tty);

	if (retval)
		return retval;

	down_read(&tty->termios_rwsem);
	tmp_termios = tty->termios;
	up_read(&tty->termios_rwsem);

	if (opt & TERMIOS_TERMIO) {
		if (user_termio_to_kernel_termios(&tmp_termios,
						(struct termio __user *)arg))
			return -EFAULT;
#ifdef TCGETS2
	} else if (opt & TERMIOS_OLD) {
		if (user_termios_to_kernel_termios_1(&tmp_termios,
						(struct termios __user *)arg))
			return -EFAULT;
	} else {
		if (user_termios_to_kernel_termios(&tmp_termios,
						(struct termios2 __user *)arg))
			return -EFAULT;
	}
#else
	} else if (user_termios_to_kernel_termios(&tmp_termios,
					(struct termios __user *)arg))
		return -EFAULT;
#endif

	/* If old style Bfoo values are used then load c_ispeed/c_ospeed
	 * with the real speed so its unconditionally usable */
	tmp_termios.c_ispeed = tty_termios_input_baud_rate(&tmp_termios);
	tmp_termios.c_ospeed = tty_termios_baud_rate(&tmp_termios);

	ld = tty_ldisc_ref(tty);

	if (ld != NULL) {
		if ((opt & TERMIOS_FLUSH) && ld->ops->flush_buffer)
			ld->ops->flush_buffer(tty);
		tty_ldisc_deref(ld);
	}

	if (opt & TERMIOS_WAIT) {
		tty_wait_until_sent(tty, 0);
		if (signal_pending(current))
			return -ERESTARTSYS;
	}

	tty_set_termios(tty, &tmp_termios);

	/* FIXME: Arguably if tmp_termios == tty->termios AND the
	   actual requested termios was not tmp_termios then we may
	   want to return an error as no user requested change has
	   succeeded */
	return 0;
}

static void copy_termios(struct tty_struct *tty, struct ktermios *kterm)
{
	down_read(&tty->termios_rwsem);
	*kterm = tty->termios;
	up_read(&tty->termios_rwsem);
}

static void copy_termios_locked(struct tty_struct *tty, struct ktermios *kterm)
{
	down_read(&tty->termios_rwsem);
	*kterm = tty->termios_locked;
	up_read(&tty->termios_rwsem);
}

static int get_termio(struct tty_struct *tty, struct termio __user *termio)
{
	struct ktermios kterm;
	copy_termios(tty, &kterm);
	if (kernel_termios_to_user_termio(termio, &kterm))
		return -EFAULT;
	return 0;
}


#ifdef TCGETX

/**
 *	set_termiox	-	set termiox fields if possible
 *	@tty: terminal
 *	@arg: termiox structure from user
 *	@opt: option flags for ioctl type
 *
 *	Implement the device calling points for the SYS5 termiox ioctl
 *	interface in Linux
 */

static int set_termiox(struct tty_struct *tty, void __user *arg, int opt)
{
	struct termiox tnew;
	struct tty_ldisc *ld;

	if (tty->termiox == NULL)
		return -EINVAL;
	if (copy_from_user(&tnew, arg, sizeof(struct termiox)))
		return -EFAULT;

	ld = tty_ldisc_ref(tty);
	if (ld != NULL) {
		if ((opt & TERMIOS_FLUSH) && ld->ops->flush_buffer)
			ld->ops->flush_buffer(tty);
		tty_ldisc_deref(ld);
	}
	if (opt & TERMIOS_WAIT) {
		tty_wait_until_sent(tty, 0);
		if (signal_pending(current))
			return -ERESTARTSYS;
	}

	down_write(&tty->termios_rwsem);
	if (tty->ops->set_termiox)
		tty->ops->set_termiox(tty, &tnew);
	up_write(&tty->termios_rwsem);
	return 0;
}

#endif


#ifdef TIOCGETP
/*
 * These are deprecated, but there is limited support..
 *
 * The "sg_flags" translation is a joke..
 */
static int get_sgflags(struct tty_struct *tty)
{
	int flags = 0;

	if (!(tty->termios.c_lflag & ICANON)) {
		if (tty->termios.c_lflag & ISIG)
			flags |= 0x02;		/* cbreak */
		else
			flags |= 0x20;		/* raw */
	}
	if (tty->termios.c_lflag & ECHO)
		flags |= 0x08;			/* echo */
	if (tty->termios.c_oflag & OPOST)
		if (tty->termios.c_oflag & ONLCR)
			flags |= 0x10;		/* crmod */
	return flags;
}

static int get_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
{
	struct sgttyb tmp;

	down_read(&tty->termios_rwsem);
	tmp.sg_ispeed = tty->termios.c_ispeed;
	tmp.sg_ospeed = tty->termios.c_ospeed;
	tmp.sg_erase = tty->termios.c_cc[VERASE];
	tmp.sg_kill = tty->termios.c_cc[VKILL];
	tmp.sg_flags = get_sgflags(tty);
	up_read(&tty->termios_rwsem);

	return copy_to_user(sgttyb, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}

static void set_sgflags(struct ktermios *termios, int flags)
{
	termios->c_iflag = ICRNL | IXON;
	termios->c_oflag = 0;
	termios->c_lflag = ISIG | ICANON;
	if (flags & 0x02) {	/* cbreak */
		termios->c_iflag = 0;
		termios->c_lflag &= ~ICANON;
	}
	if (flags & 0x08) {		/* echo */
		termios->c_lflag |= ECHO | ECHOE | ECHOK |
				    ECHOCTL | ECHOKE | IEXTEN;
	}
	if (flags & 0x10) {		/* crmod */
		termios->c_oflag |= OPOST | ONLCR;
	}
	if (flags & 0x20) {	/* raw */
		termios->c_iflag = 0;
		termios->c_lflag &= ~(ISIG | ICANON);
	}
	if (!(termios->c_lflag & ICANON)) {
		termios->c_cc[VMIN] = 1;
		termios->c_cc[VTIME] = 0;
	}
}

/**
 *	set_sgttyb		-	set legacy terminal values
 *	@tty: tty structure
 *	@sgttyb: pointer to old style terminal structure
 *
 *	Updates a terminal from the legacy BSD style terminal information
 *	structure.
 *
 *	Locking: termios_rwsem
 */

static int set_sgttyb(struct tty_struct *tty, struct sgttyb __user *sgttyb)
{
	int retval;
	struct sgttyb tmp;
	struct ktermios termios;

	retval = tty_check_change(tty);
	if (retval)
		return retval;

	if (copy_from_user(&tmp, sgttyb, sizeof(tmp)))
		return -EFAULT;

	down_write(&tty->termios_rwsem);
	termios = tty->termios;
	termios.c_cc[VERASE] = tmp.sg_erase;
	termios.c_cc[VKILL] = tmp.sg_kill;
	set_sgflags(&termios, tmp.sg_flags);
	/* Try and encode into Bfoo format */
#ifdef BOTHER
	tty_termios_encode_baud_rate(&termios, termios.c_ispeed,
						termios.c_ospeed);
#endif
	up_write(&tty->termios_rwsem);
	tty_set_termios(tty, &termios);
	return 0;
}
#endif

#ifdef TIOCGETC
static int get_tchars(struct tty_struct *tty, struct tchars __user *tchars)
{
	struct tchars tmp;

	down_read(&tty->termios_rwsem);
	tmp.t_intrc = tty->termios.c_cc[VINTR];
	tmp.t_quitc = tty->termios.c_cc[VQUIT];
	tmp.t_startc = tty->termios.c_cc[VSTART];
	tmp.t_stopc = tty->termios.c_cc[VSTOP];
	tmp.t_eofc = tty->termios.c_cc[VEOF];
	tmp.t_brkc = tty->termios.c_cc[VEOL2];	/* what is brkc anyway? */
	up_read(&tty->termios_rwsem);
	return copy_to_user(tchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}

static int set_tchars(struct tty_struct *tty, struct tchars __user *tchars)
{
	struct tchars tmp;

	if (copy_from_user(&tmp, tchars, sizeof(tmp)))
		return -EFAULT;
	down_write(&tty->termios_rwsem);
	tty->termios.c_cc[VINTR] = tmp.t_intrc;
	tty->termios.c_cc[VQUIT] = tmp.t_quitc;
	tty->termios.c_cc[VSTART] = tmp.t_startc;
	tty->termios.c_cc[VSTOP] = tmp.t_stopc;
	tty->termios.c_cc[VEOF] = tmp.t_eofc;
	tty->termios.c_cc[VEOL2] = tmp.t_brkc;	/* what is brkc anyway? */
	up_write(&tty->termios_rwsem);
	return 0;
}
#endif

#ifdef TIOCGLTC
static int get_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
{
	struct ltchars tmp;

	down_read(&tty->termios_rwsem);
	tmp.t_suspc = tty->termios.c_cc[VSUSP];
	/* what is dsuspc anyway? */
	tmp.t_dsuspc = tty->termios.c_cc[VSUSP];
	tmp.t_rprntc = tty->termios.c_cc[VREPRINT];
	/* what is flushc anyway? */
	tmp.t_flushc = tty->termios.c_cc[VEOL2];
	tmp.t_werasc = tty->termios.c_cc[VWERASE];
	tmp.t_lnextc = tty->termios.c_cc[VLNEXT];
	up_read(&tty->termios_rwsem);
	return copy_to_user(ltchars, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}

static int set_ltchars(struct tty_struct *tty, struct ltchars __user *ltchars)
{
	struct ltchars tmp;

	if (copy_from_user(&tmp, ltchars, sizeof(tmp)))
		return -EFAULT;

	down_write(&tty->termios_rwsem);
	tty->termios.c_cc[VSUSP] = tmp.t_suspc;
	/* what is dsuspc anyway? */
	tty->termios.c_cc[VEOL2] = tmp.t_dsuspc;
	tty->termios.c_cc[VREPRINT] = tmp.t_rprntc;
	/* what is flushc anyway? */
	tty->termios.c_cc[VEOL2] = tmp.t_flushc;
	tty->termios.c_cc[VWERASE] = tmp.t_werasc;
	tty->termios.c_cc[VLNEXT] = tmp.t_lnextc;
	up_write(&tty->termios_rwsem);
	return 0;
}
#endif

/**
 *	send_prio_char		-	send priority character
 *
 *	Send a high priority character to the tty even if stopped
 *
 *	Locking: none for xchar method, write ordering for write method.
 */

static int send_prio_char(struct tty_struct *tty, char ch)
{
	int	was_stopped = tty->stopped;

	if (tty->ops->send_xchar) {
		tty->ops->send_xchar(tty, ch);
		return 0;
	}

	if (tty_write_lock(tty, 0) < 0)
		return -ERESTARTSYS;

	if (was_stopped)
		start_tty(tty);
	tty->ops->write(tty, &ch, 1);
	if (was_stopped)
		stop_tty(tty);
	tty_write_unlock(tty);
	return 0;
}

/**
 *	tty_change_softcar	-	carrier change ioctl helper
 *	@tty: tty to update
 *	@arg: enable/disable CLOCAL
 *
 *	Perform a change to the CLOCAL state and call into the driver
 *	layer to make it visible. All done with the termios rwsem
 */

static int tty_change_softcar(struct tty_struct *tty, int arg)
{
	int ret = 0;
	int bit = arg ? CLOCAL : 0;
	struct ktermios old;

	down_write(&tty->termios_rwsem);
	old = tty->termios;
	tty->termios.c_cflag &= ~CLOCAL;
	tty->termios.c_cflag |= bit;
	if (tty->ops->set_termios)
		tty->ops->set_termios(tty, &old);
	if ((tty->termios.c_cflag & CLOCAL) != bit)
		ret = -EINVAL;
	up_write(&tty->termios_rwsem);
	return ret;
}

/**
 *	tty_mode_ioctl		-	mode related ioctls
 *	@tty: tty for the ioctl
 *	@file: file pointer for the tty
 *	@cmd: command
 *	@arg: ioctl argument
 *
 *	Perform non line discipline specific mode control ioctls. This
 *	is designed to be called by line disciplines to ensure they provide
 *	consistent mode setting.
 */

int tty_mode_ioctl(struct tty_struct *tty, struct file *file,
			unsigned int cmd, unsigned long arg)
{
	struct tty_struct *real_tty;
	void __user *p = (void __user *)arg;
	int ret = 0;
	struct ktermios kterm;

	BUG_ON(file == NULL);

	if (tty->driver->type == TTY_DRIVER_TYPE_PTY &&
	    tty->driver->subtype == PTY_TYPE_MASTER)
		real_tty = tty->link;
	else
		real_tty = tty;

	switch (cmd) {
#ifdef TIOCGETP
	case TIOCGETP:
		return get_sgttyb(real_tty, (struct sgttyb __user *) arg);
	case TIOCSETP:
	case TIOCSETN:
		return set_sgttyb(real_tty, (struct sgttyb __user *) arg);
#endif
#ifdef TIOCGETC
	case TIOCGETC:
		return get_tchars(real_tty, p);
	case TIOCSETC:
		return set_tchars(real_tty, p);
#endif
#ifdef TIOCGLTC
	case TIOCGLTC:
		return get_ltchars(real_tty, p);
	case TIOCSLTC:
		return set_ltchars(real_tty, p);
#endif
	case TCSETSF:
		return set_termios(real_tty, p,  TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_OLD);
	case TCSETSW:
		return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_OLD);
	case TCSETS:
		return set_termios(real_tty, p, TERMIOS_OLD);
#ifndef TCGETS2
	case TCGETS:
		copy_termios(real_tty, &kterm);
		if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
#else
	case TCGETS:
		copy_termios(real_tty, &kterm);
		if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
	case TCGETS2:
		copy_termios(real_tty, &kterm);
		if (kernel_termios_to_user_termios((struct termios2 __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
	case TCSETSF2:
		return set_termios(real_tty, p,  TERMIOS_FLUSH | TERMIOS_WAIT);
	case TCSETSW2:
		return set_termios(real_tty, p, TERMIOS_WAIT);
	case TCSETS2:
		return set_termios(real_tty, p, 0);
#endif
	case TCGETA:
		return get_termio(real_tty, p);
	case TCSETAF:
		return set_termios(real_tty, p, TERMIOS_FLUSH | TERMIOS_WAIT | TERMIOS_TERMIO);
	case TCSETAW:
		return set_termios(real_tty, p, TERMIOS_WAIT | TERMIOS_TERMIO);
	case TCSETA:
		return set_termios(real_tty, p, TERMIOS_TERMIO);
#ifndef TCGETS2
	case TIOCGLCKTRMIOS:
		copy_termios_locked(real_tty, &kterm);
		if (kernel_termios_to_user_termios((struct termios __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
	case TIOCSLCKTRMIOS:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		copy_termios_locked(real_tty, &kterm);
		if (user_termios_to_kernel_termios(&kterm,
					       (struct termios __user *) arg))
			return -EFAULT;
		down_write(&real_tty->termios_rwsem);
		real_tty->termios_locked = kterm;
		up_write(&real_tty->termios_rwsem);
		return 0;
#else
	case TIOCGLCKTRMIOS:
		copy_termios_locked(real_tty, &kterm);
		if (kernel_termios_to_user_termios_1((struct termios __user *)arg, &kterm))
			ret = -EFAULT;
		return ret;
	case TIOCSLCKTRMIOS:
		if (!capable(CAP_SYS_ADMIN))
			return -EPERM;
		copy_termios_locked(real_tty, &kterm);
		if (user_termios_to_kernel_termios_1(&kterm,
					       (struct termios __user *) arg))
			return -EFAULT;
		down_write(&real_tty->termios_rwsem);
		real_tty->termios_locked = kterm;
		up_write(&real_tty->termios_rwsem);
		return ret;
#endif
#ifdef TCGETX
	case TCGETX: {
		struct termiox ktermx;
		if (real_tty->termiox == NULL)
			return -EINVAL;
		down_read(&real_tty->termios_rwsem);
		memcpy(&ktermx, real_tty->termiox, sizeof(struct termiox));
		up_read(&real_tty->termios_rwsem);
		if (copy_to_user(p, &ktermx, sizeof(struct termiox)))
			ret = -EFAULT;
		return ret;
	}
	case TCSETX:
		return set_termiox(real_tty, p, 0);
	case TCSETXW:
		return set_termiox(real_tty, p, TERMIOS_WAIT);
	case TCSETXF:
		return set_termiox(real_tty, p, TERMIOS_FLUSH);
#endif		
	case TIOCGSOFTCAR:
		copy_termios(real_tty, &kterm);
		ret = put_user((kterm.c_cflag & CLOCAL) ? 1 : 0,
						(int __user *)arg);
		return ret;
	case TIOCSSOFTCAR:
		if (get_user(arg, (unsigned int __user *) arg))
			return -EFAULT;
		return tty_change_softcar(real_tty, arg);
	default:
		return -ENOIOCTLCMD;
	}
}
EXPORT_SYMBOL_GPL(tty_mode_ioctl);


/* Caller guarantees ldisc reference is held */
static int __tty_perform_flush(struct tty_struct *tty, unsigned long arg)
{
	struct tty_ldisc *ld = tty->ldisc;

	switch (arg) {
	case TCIFLUSH:
		if (ld && ld->ops->flush_buffer) {
			ld->ops->flush_buffer(tty);
			tty_unthrottle(tty);
		}
		break;
	case TCIOFLUSH:
		if (ld && ld->ops->flush_buffer) {
			ld->ops->flush_buffer(tty);
			tty_unthrottle(tty);
		}
		/* fall through */
	case TCOFLUSH:
		tty_driver_flush_buffer(tty);
		break;
	default:
		return -EINVAL;
	}
	return 0;
}

int tty_perform_flush(struct tty_struct *tty, unsigned long arg)
{
	struct tty_ldisc *ld;
	int retval = tty_check_change(tty);
	if (retval)
		return retval;

	ld = tty_ldisc_ref_wait(tty);
	retval = __tty_perform_flush(tty, arg);
	if (ld)
		tty_ldisc_deref(ld);
	return retval;
}
EXPORT_SYMBOL_GPL(tty_perform_flush);

int n_tty_ioctl_helper(struct tty_struct *tty, struct file *file,
		       unsigned int cmd, unsigned long arg)
{
	int retval;

	switch (cmd) {
	case TCXONC:
		retval = tty_check_change(tty);
		if (retval)
			return retval;
		switch (arg) {
		case TCOOFF:
			if (!tty->flow_stopped) {
				tty->flow_stopped = 1;
				stop_tty(tty);
			}
			break;
		case TCOON:
			if (tty->flow_stopped) {
				tty->flow_stopped = 0;
				start_tty(tty);
			}
			break;
		case TCIOFF:
			if (STOP_CHAR(tty) != __DISABLED_CHAR)
				return send_prio_char(tty, STOP_CHAR(tty));
			break;
		case TCION:
			if (START_CHAR(tty) != __DISABLED_CHAR)
				return send_prio_char(tty, START_CHAR(tty));
			break;
		default:
			return -EINVAL;
		}
		return 0;
	case TCFLSH:
		retval = tty_check_change(tty);
		if (retval)
			return retval;
		return __tty_perform_flush(tty, arg);
	default:
		/* Try the mode commands */
		return tty_mode_ioctl(tty, file, cmd, arg);
	}
}
EXPORT_SYMBOL(n_tty_ioctl_helper);

#ifdef CONFIG_COMPAT
long n_tty_compat_ioctl_helper(struct tty_struct *tty, struct file *file,
					unsigned int cmd, unsigned long arg)
{
	switch (cmd) {
	case TIOCGLCKTRMIOS:
	case TIOCSLCKTRMIOS:
		return tty_mode_ioctl(tty, file, cmd, (unsigned long) compat_ptr(arg));
	default:
		return -ENOIOCTLCMD;
	}
}
EXPORT_SYMBOL(n_tty_compat_ioctl_helper);
#endif