man2/ioctl_tty.2

   1 .\" Copyright 2002 Walter Harms <walter.harms@informatik.uni-oldenburg.de>
   2 .\" and Andries Brouwer <aeb@cwi.nl>.
   3 .\"
   4 .\" %%%LICENSE_START(GPL_NOVERSION_ONELINE)
   5 .\" Distributed under GPL
   6 .\" %%%LICENSE_END
   7 .\"
   8 .TH IOCTL_TTY 2 2021-08-27 "Linux" "Linux Programmer's Manual"
   9 .SH NAME
  10 ioctl_tty \- ioctls for terminals and serial lines
  11 .SH SYNOPSIS
  12 .nf
  13 .B #include <sys/ioctl.h>
  14 .BR "#include <asm/termbits.h>" "   /* Definition of " "struct termios" ,
  15 .BR    "                               struct termios2" ", and"
  16 .BR    "                               Bnnn" ", " BOTHER ", " CBAUD ", " CLOCAL ,
  17 .BR    "                               TC*" { FLUSH , ON , OFF "} and other constants */"
  18 .PP
  19 .BI "int ioctl(int " fd ", int " cmd ", ...);"
  20 .fi
  21 .SH DESCRIPTION
  22 The
  23 .BR ioctl (2)
  24 call for terminals and serial ports accepts many possible command arguments.
  25 Most require a third argument, of varying type, here called
  26 .I argp
  27 or
  28 .IR arg .
  29 .PP
  30 Use of
  31 .BR ioctl ()
  32 makes for nonportable programs.
  33 Use the POSIX interface described in
  34 .BR termios (3)
  35 whenever possible.
  36 .PP
  37 Please note that
  38 .B struct termios
  39 from
  40 .I <asm/termbits.h>
  41 is different and incompatible with
  42 .B struct termios
  43 from
  44 .IR <termios.h> .
  45 These ioctl calls require
  46 .B struct termios
  47 from
  48 .IR <asm/termbits.h> .
  49 .SS Get and set terminal attributes
  50 .TP
  51 .B TCGETS
  52 Argument:
  53 .BI "struct termios *" argp
  54 .IP
  55 Equivalent to
  56 .IR "tcgetattr(fd, argp)" .
  57 .IP
  58 Get the current serial port settings.
  59 .TP
  60 .B TCSETS
  61 Argument:
  62 .BI "const struct termios *" argp
  63 .IP
  64 Equivalent to
  65 .IR "tcsetattr(fd, TCSANOW, argp)" .
  66 .IP
  67 Set the current serial port settings.
  68 .TP
  69 .B TCSETSW
  70 Argument:
  71 .BI "const struct termios *" argp
  72 .IP
  73 Equivalent to
  74 .IR "tcsetattr(fd, TCSADRAIN, argp)" .
  75 .IP
  76 Allow the output buffer to drain, and
  77 set the current serial port settings.
  78 .TP
  79 .B TCSETSF
  80 Argument:
  81 .BI "const struct termios *" argp
  82 .IP
  83 Equivalent to
  84 .IR "tcsetattr(fd, TCSAFLUSH, argp)" .
  85 .IP
  86 Allow the output buffer to drain, discard pending input, and
  87 set the current serial port settings.
  88 .PP
  89 The following four ioctls, added in Linux 2.6.20,
  90 .\" commit 64bb6c5e1ddcd47c951740485026ef08975ee2e6
  91 .\" commit 592ee3a5e5e2a981ef2829a0380093006d045661
  92 are just like
  93 .BR TCGETS ,
  94 .BR TCSETS ,
  95 .BR TCSETSW ,
  96 .BR TCSETSF ,
  97 except that they take a
  98 .I "struct termios2\ *"
  99 instead of a
 100 .IR "struct termios\ *" .
 101 If the structure member
 102 .B c_cflag
 103 contains the flag
 104 .BR BOTHER ,
 105 then the baud rate is stored in the structure members
 106 .B c_ispeed
 107 and
 108 .B c_ospeed
 109 as integer values.
 110 These ioctls are not supported on all architectures.
 111 .RS
 112 .TS
 113 lb l.
 114 TCGETS2 \fBstruct termios2 *\fPargp
 115 TCSETS2 \fBconst struct termios2 *\fPargp
 116 TCSETSW2        \fBconst struct termios2 *\fPargp
 117 TCSETSF2        \fBconst struct termios2 *\fPargp
 118 .TE
 119 .RE
 120 .PP
 121 The following four ioctls are just like
 122 .BR TCGETS ,
 123 .BR TCSETS ,
 124 .BR TCSETSW ,
 125 .BR TCSETSF ,
 126 except that they take a
 127 .I "struct termio\ *"
 128 instead of a
 129 .IR "struct termios\ *" .
 130 .RS
 131 .TS
 132 lb l.
 133 TCGETA  \fBstruct termio *\fPargp
 134 TCSETA  \fBconst struct termio *\fPargp
 135 TCSETAW \fBconst struct termio *\fPargp
 136 TCSETAF \fBconst struct termio *\fPargp
 137 .TE
 138 .RE
 139 .SS Locking the termios structure
 140 The
 141 .I termios
 142 structure of a terminal can be locked.
 143 The lock is itself a
 144 .I termios
 145 structure, with nonzero bits or fields indicating a
 146 locked value.
 147 .TP
 148 .B TIOCGLCKTRMIOS
 149 Argument:
 150 .BI "struct termios *" argp
 151 .IP
 152 Gets the locking status of the
 153 .I termios
 154 structure of the terminal.
 155 .TP
 156 .B TIOCSLCKTRMIOS
 157 Argument:
 158 .BI "const struct termios *" argp
 159 .IP
 160 Sets the locking status of the
 161 .I termios
 162 structure of the terminal.
 163 Only a process with the
 164 .BR CAP_SYS_ADMIN
 165 capability can do this.
 166 .SS Get and set window size
 167 Window sizes are kept in the kernel, but not used by the kernel
 168 (except in the case of virtual consoles, where the kernel will
 169 update the window size when the size of the virtual console changes,
 170 for example, by loading a new font).
 171 .TP
 172 .B TIOCGWINSZ
 173 Argument:
 174 .BI "struct winsize *" argp
 175 .IP
 176 Get window size.
 177 .TP
 178 .B TIOCSWINSZ
 179 Argument:
 180 .BI "const struct winsize *" argp
 181 .IP
 182 Set window size.
 183 .PP
 184 The struct used by these ioctls is defined as
 185 .PP
 186 .in +4n
 187 .EX
 188 struct winsize {
 189     unsigned short ws_row;
 190     unsigned short ws_col;
 191     unsigned short ws_xpixel;   /* unused */
 192     unsigned short ws_ypixel;   /* unused */
 193 };
 194 .EE
 195 .in
 196 .PP
 197 When the window size changes, a
 198 .B SIGWINCH
 199 signal is sent to the
 200 foreground process group.
 201 .SS Sending a break
 202 .TP
 203 .B TCSBRK
 204 Argument:
 205 .BI "int " arg
 206 .IP
 207 Equivalent to
 208 .IR "tcsendbreak(fd, arg)" .
 209 .IP
 210 If the terminal is using asynchronous serial data transmission, and
 211 .I arg
 212 is zero, then send a break (a stream of zero bits) for between
 213 0.25 and 0.5 seconds.
 214 If the terminal is not using asynchronous
 215 serial data transmission, then either a break is sent, or the function
 216 returns without doing anything.
 217 When
 218 .I arg
 219 is nonzero, nobody knows what will happen.
 220 .IP
 221 (SVr4, UnixWare, Solaris, and Linux treat
 222 .I "tcsendbreak(fd,arg)"
 223 with nonzero
 224 .I arg
 225 like
 226 .IR "tcdrain(fd)" .
 227 SunOS treats
 228 .I arg
 229 as a multiplier, and sends a stream of bits
 230 .I arg
 231 times as long as done for zero
 232 .IR arg .
 233 DG/UX and AIX treat
 234 .I arg
 235 (when nonzero) as a time interval measured in milliseconds.
 236 HP-UX ignores
 237 .IR arg .)
 238 .TP
 239 .B TCSBRKP
 240 Argument:
 241 .BI "int " arg
 242 .IP
 243 So-called "POSIX version" of
 244 .BR TCSBRK .
 245 It treats nonzero
 246 .I arg
 247 as a time interval measured in deciseconds, and does nothing
 248 when the driver does not support breaks.
 249 .TP
 250 .B TIOCSBRK
 251 Argument:
 252 .BI "void"
 253 .IP
 254 Turn break on, that is, start sending zero bits.
 255 .TP
 256 .B TIOCCBRK
 257 Argument:
 258 .BI "void"
 259 .IP
 260 Turn break off, that is, stop sending zero bits.
 261 .SS Software flow control
 262 .TP
 263 .B TCXONC
 264 Argument:
 265 .BI "int " arg
 266 .IP
 267 Equivalent to
 268 .IR "tcflow(fd, arg)" .
 269 .IP
 270 See
 271 .BR tcflow (3)
 272 for the argument values
 273 .BR TCOOFF ,
 274 .BR TCOON ,
 275 .BR TCIOFF ,
 276 .BR TCION .
 277 .SS Buffer count and flushing
 278 .TP
 279 .BI FIONREAD
 280 Argument:
 281 .BI "int *" argp
 282 .IP
 283 Get the number of bytes in the input buffer.
 284 .TP
 285 .B TIOCINQ
 286 Argument:
 287 .BI "int *" argp
 288 .IP
 289 Same as
 290 .BR FIONREAD .
 291 .TP
 292 .B TIOCOUTQ
 293 Argument:
 294 .BI "int *" argp
 295 .IP
 296 Get the number of bytes in the output buffer.
 297 .TP
 298 .B TCFLSH
 299 Argument:
 300 .BI "int " arg
 301 .IP
 302 Equivalent to
 303 .IR "tcflush(fd, arg)" .
 304 .IP
 305 See
 306 .BR tcflush (3)
 307 for the argument values
 308 .BR TCIFLUSH ,
 309 .BR TCOFLUSH ,
 310 .BR TCIOFLUSH .
 311 .SS Faking input
 312 .TP
 313 .B TIOCSTI
 314 Argument:
 315 .BI "const char *" argp
 316 .IP
 317 Insert the given byte in the input queue.
 318 .SS Redirecting console output
 319 .TP
 320 .B TIOCCONS
 321 Argument:
 322 .BI "void"
 323 .IP
 324 Redirect output that would have gone to
 325 .I /dev/console
 326 or
 327 .I /dev/tty0
 328 to the given terminal.
 329 If that was a pseudoterminal master, send it to the slave.
 330 In Linux before version 2.6.10,
 331 anybody can do this as long as the output was not redirected yet;
 332 since version 2.6.10, only a process with the
 333 .BR CAP_SYS_ADMIN
 334 capability may do this.
 335 If output was redirected already, then
 336 .B EBUSY
 337 is returned,
 338 but redirection can be stopped by using this ioctl with
 339 .I fd
 340 pointing at
 341 .I /dev/console
 342 or
 343 .IR /dev/tty0 .
 344 .SS Controlling terminal
 345 .TP
 346 .B TIOCSCTTY
 347 Argument:
 348 .BI "int " arg
 349 .IP
 350 Make the given terminal the controlling terminal of the calling process.
 351 The calling process must be a session leader and not have a
 352 controlling terminal already.
 353 For this case,
 354 .I arg
 355 should be specified as zero.
 356 .IP
 357 If this terminal is already the controlling terminal
 358 of a different session group, then the ioctl fails with
 359 .BR EPERM ,
 360 unless the caller has the
 361 .BR CAP_SYS_ADMIN
 362 capability and
 363 .I arg
 364 equals 1, in which case the terminal is stolen, and all processes that had
 365 it as controlling terminal lose it.
 366 .TP
 367 .B TIOCNOTTY
 368 Argument:
 369 .BI "void"
 370 .IP
 371 If the given terminal was the controlling terminal of the calling process,
 372 give up this controlling terminal.
 373 If the process was session leader,
 374 then send
 375 .B SIGHUP
 376 and
 377 .B SIGCONT
 378 to the foreground process group
 379 and all processes in the current session lose their controlling terminal.
 380 .SS Process group and session ID
 381 .TP
 382 .B TIOCGPGRP
 383 Argument:
 384 .BI "pid_t *" argp
 385 .IP
 386 When successful, equivalent to
 387 .IR "*argp = tcgetpgrp(fd)" .
 388 .IP
 389 Get the process group ID of the foreground process group on this terminal.
 390 .TP
 391 .B TIOCSPGRP
 392 Argument:
 393 .BI "const pid_t *" argp
 394 .IP
 395 Equivalent to
 396 .IR "tcsetpgrp(fd, *argp)" .
 397 .IP
 398 Set the foreground process group ID of this terminal.
 399 .TP
 400 .B TIOCGSID
 401 Argument:
 402 .BI "pid_t *" argp
 403 .IP
 404 When successful, equivalent to
 405 .IR "*argp = tcgetsid(fd)" .
 406 .IP
 407 Get the session ID of the given terminal.
 408 This fails with the error
 409 .B ENOTTY
 410 if the terminal is not a master pseudoterminal
 411 and not our controlling terminal.
 412 Strange.
 413 .SS Exclusive mode
 414 .TP
 415 .B TIOCEXCL
 416 Argument:
 417 .BI "void"
 418 .IP
 419 Put the terminal into exclusive mode.
 420 No further
 421 .BR open (2)
 422 operations on the terminal are permitted.
 423 (They fail with
 424 .BR EBUSY ,
 425 except for a process with the
 426 .BR CAP_SYS_ADMIN
 427 capability.)
 428 .TP
 429 .B TIOCGEXCL
 430 Argument:
 431 .BI "int *" argp
 432 .IP
 433 (since Linux 3.8)
 434 If the terminal is currently in exclusive mode,
 435 place a nonzero value in the location pointed to by
 436 .IR argp ;
 437 otherwise, place zero in
 438 .IR *argp .
 439 .TP
 440 .B TIOCNXCL
 441 Argument:
 442 .BI "void"
 443 .IP
 444 Disable exclusive mode.
 445 .SS Line discipline
 446 .TP
 447 .B TIOCGETD
 448 Argument:
 449 .BI "int *" argp
 450 .IP
 451 Get the line discipline of the terminal.
 452 .TP
 453 .B TIOCSETD
 454 Argument:
 455 .BI "const int *" argp
 456 .IP
 457 Set the line discipline of the terminal.
 458 .SS Pseudoterminal ioctls
 459 .TP
 460 .B TIOCPKT
 461 Argument:
 462 .BI "const int *" argp
 463 .IP
 464 Enable (when
 465 .RI * argp
 466 is nonzero) or disable packet mode.
 467 Can be applied to the master side of a pseudoterminal only (and will return
 468 .B ENOTTY
 469 otherwise).
 470 In packet mode, each subsequent
 471 .BR read (2)
 472 will return a packet that either contains a single nonzero control byte,
 473 or has a single byte containing zero (\(aq\e0\(aq) followed by data
 474 written on the slave side of the pseudoterminal.
 475 If the first byte is not
 476 .B TIOCPKT_DATA
 477 (0), it is an OR of one
 478 or more of the following bits:
 479 .IP
 480 .ad l
 481 .TS
 482 lb l.
 483 TIOCPKT_FLUSHREAD       T{
 484 The read queue for the terminal is flushed.
 485 T}
 486 TIOCPKT_FLUSHWRITE      T{
 487 The write queue for the terminal is flushed.
 488 T}
 489 TIOCPKT_STOP    T{
 490 Output to the terminal is stopped.
 491 T}
 492 TIOCPKT_START   T{
 493 Output to the terminal is restarted.
 494 T}
 495 TIOCPKT_DOSTOP  T{
 496 The start and stop characters are \fB\(haS\fP/\fB\(haQ\fP.
 497 T}
 498 TIOCPKT_NOSTOP  T{
 499 The start and stop characters are not \fB\(haS\fP/\fB\(haQ\fP.
 500 T}
 501 .TE
 502 .ad
 503 .IP
 504 While packet mode is in use, the presence
 505 of control status information to be read
 506 from the master side may be detected by a
 507 .BR select (2)
 508 for exceptional conditions or a
 509 .BR poll (2)
 510 for the
 511 .B POLLPRI
 512 event.
 513 .IP
 514 This mode is used by
 515 .BR rlogin (1)
 516 and
 517 .BR rlogind (8)
 518 to implement a remote-echoed,
 519 locally \fB\(haS\fP/\fB\(haQ\fP flow-controlled remote login.
 520 .TP
 521 .B TIOCGPKT
 522 Argument:
 523 .BI "const int *" argp
 524 .IP
 525 (since Linux 3.8)
 526 Return the current packet mode setting in the integer pointed to by
 527 .IR argp .
 528 .TP
 529 .B TIOCSPTLCK
 530 Argument:
 531 .BI "int *" argp
 532 .IP
 533 Set (if
 534 .IR *argp
 535 is nonzero) or remove (if
 536 .IR *argp
 537 is zero) the lock on the pseudoterminal slave device.
 538 (See also
 539 .BR unlockpt (3).)
 540 .TP
 541 .B TIOCGPTLCK
 542 Argument:
 543 .BI "int *" argp
 544 .IP
 545 (since Linux 3.8)
 546 Place the current lock state of the pseudoterminal slave device
 547 in the location pointed to by
 548 .IR argp .
 549 .TP
 550 .B TIOCGPTPEER
 551 Argument:
 552 .BI "int " flags
 553 .IP
 554 .\" commit 54ebbfb1603415d9953c150535850d30609ef077
 555 (since Linux 4.13)
 556 Given a file descriptor in
 557 .I fd
 558 that refers to a pseudoterminal master,
 559 open (with the given
 560 .BR open (2)-style
 561 .IR flags )
 562 and return a new file descriptor that refers to the peer
 563 pseudoterminal slave device.
 564 This operation can be performed
 565 regardless of whether the pathname of the slave device
 566 is accessible through the calling process's mount namespace.
 567 .IP
 568 Security-conscious programs interacting with namespaces may wish to use this
 569 operation rather than
 570 .BR open (2)
 571 with the pathname returned by
 572 .BR ptsname (3),
 573 and similar library functions that have insecure APIs.
 574 (For example, confusion can occur in some cases using
 575 .BR ptsname (3)
 576 with a pathname where a devpts filesystem
 577 has been mounted in a different mount namespace.)
 578 .PP
 579 The BSD ioctls
 580 .BR TIOCSTOP ,
 581 .BR TIOCSTART ,
 582 .BR TIOCUCNTL ,
 583 and
 584 .B TIOCREMOTE
 585 have not been implemented under Linux.
 586 .SS Modem control
 587 .TP
 588 .B TIOCMGET
 589 Argument:
 590 .BI "int *" argp
 591 .IP
 592 Get the status of modem bits.
 593 .TP
 594 .B TIOCMSET
 595 Argument:
 596 .BI "const int *" argp
 597 .IP
 598 Set the status of modem bits.
 599 .TP
 600 .B TIOCMBIC
 601 Argument:
 602 .BI "const int *" argp
 603 .IP
 604 Clear the indicated modem bits.
 605 .TP
 606 .B TIOCMBIS
 607 Argument:
 608 .BI "const int *" argp
 609 .IP
 610 Set the indicated modem bits.
 611 .PP
 612 The following bits are used by the above ioctls:
 613 .PP
 614 .TS
 615 lb l.
 616 TIOCM_LE        DSR (data set ready/line enable)
 617 TIOCM_DTR       DTR (data terminal ready)
 618 TIOCM_RTS       RTS (request to send)
 619 TIOCM_ST        Secondary TXD (transmit)
 620 TIOCM_SR        Secondary RXD (receive)
 621 TIOCM_CTS       CTS (clear to send)
 622 TIOCM_CAR       DCD (data carrier detect)
 623 TIOCM_CD        see TIOCM_CAR
 624 TIOCM_RNG       RNG (ring)
 625 TIOCM_RI        see TIOCM_RNG
 626 TIOCM_DSR       DSR (data set ready)
 627 .TE
 628 .TP
 629 .B TIOCMIWAIT
 630 Argument:
 631 .BI "int " arg
 632 .IP
 633 Wait for any of the 4 modem bits (DCD, RI, DSR, CTS) to change.
 634 The bits of interest are specified as a bit mask in
 635 .IR arg ,
 636 by ORing together any of the bit values,
 637 .BR TIOCM_RNG ,
 638 .BR TIOCM_DSR ,
 639 .BR TIOCM_CD ,
 640 and
 641 .BR TIOCM_CTS .
 642 The caller should use
 643 .B TIOCGICOUNT
 644 to see which bit has changed.
 645 .TP
 646 .B TIOCGICOUNT
 647 Argument:
 648 .BI "struct serial_icounter_struct *" argp
 649 .IP
 650 Get counts of input serial line interrupts (DCD, RI, DSR, CTS).
 651 The counts are written to the
 652 .I serial_icounter_struct
 653 structure pointed to by
 654 .IR argp .
 655 .IP
 656 Note: both 1->0 and 0->1 transitions are counted, except for
 657 RI, where only 0->1 transitions are counted.
 658 .SS Marking a line as local
 659 .TP
 660 .B TIOCGSOFTCAR
 661 Argument:
 662 .BI "int *" argp
 663 .IP
 664 ("Get software carrier flag")
 665 Get the status of the CLOCAL flag in the c_cflag field of the
 666 .I termios
 667 structure.
 668 .TP
 669 .B TIOCSSOFTCAR
 670 Argument:
 671 .BI "const int *" argp
 672 .IP
 673 ("Set software carrier flag")
 674 Set the CLOCAL flag in the
 675 .I termios
 676 structure when
 677 .RI * argp
 678 is nonzero, and clear it otherwise.
 679 .PP
 680 If the
 681 .B CLOCAL
 682 flag for a line is off, the hardware carrier detect (DCD)
 683 signal is significant, and an
 684 .BR open (2)
 685 of the corresponding terminal will block until DCD is asserted,
 686 unless the
 687 .B O_NONBLOCK
 688 flag is given.
 689 If
 690 .B CLOCAL
 691 is set, the line behaves as if DCD is always asserted.
 692 The software carrier flag is usually turned on for local devices,
 693 and is off for lines with modems.
 694 .SS Linux-specific
 695 For the
 696 .B TIOCLINUX
 697 ioctl, see
 698 .BR ioctl_console (2).
 699 .SS Kernel debugging
 700 .B "#include <linux/tty.h>"
 701 .TP
 702 .B TIOCTTYGSTRUCT
 703 Argument:
 704 .BI "struct tty_struct *" argp
 705 .IP
 706 Get the
 707 .I tty_struct
 708 corresponding to
 709 .IR fd .
 710 This command was removed in Linux 2.5.67.
 711 .\"     commit b3506a09d15dc5aee6d4bb88d759b157016e1864
 712 .\"     Author: Andries E. Brouwer <andries.brouwer@cwi.nl>
 713 .\"     Date:   Tue Apr 1 04:42:46 2003 -0800
 714 .\"
 715 .\"     [PATCH] kill TIOCTTYGSTRUCT
 716 .\"
 717 .\"     Only used for (dubious) debugging purposes, and exposes
 718 .\"     internal kernel state.
 719 .\"
 720 .\" .SS Serial info
 721 .\" .BR "#include <linux/serial.h>"
 722 .\" .PP
 723 .\" .TP
 724 .\" .BI "TIOCGSERIAL    struct serial_struct *" argp
 725 .\" Get serial info.
 726 .\" .TP
 727 .\" .BI "TIOCSSERIAL    const struct serial_struct *" argp
 728 .\" Set serial info.
 729 .SH RETURN VALUE
 730 The
 731 .BR ioctl (2)
 732 system call returns 0 on success.
 733 On error, it returns \-1 and sets
 734 .I errno
 735 to indicate the error.
 736 .SH ERRORS
 737 .TP
 738 .B EINVAL
 739 Invalid command parameter.
 740 .TP
 741 .B ENOIOCTLCMD
 742 Unknown command.
 743 .TP
 744 .B ENOTTY
 745 Inappropriate
 746 .IR fd .
 747 .TP
 748 .B EPERM
 749 Insufficient permission.
 750 .SH EXAMPLES
 751 Check the condition of DTR on the serial port.
 752 .PP
 753 .EX
 754 #include <stdio.h>
 755 #include <unistd.h>
 756 #include <fcntl.h>
 757 #include <sys/ioctl.h>
 758
 759 int
 760 main(void)
 761 {
 762     int fd, serial;
 763
 764     fd = open("/dev/ttyS0", O_RDONLY);
 765     ioctl(fd, TIOCMGET, &serial);
 766     if (serial & TIOCM_DTR)
 767         puts("TIOCM_DTR is set");
 768     else
 769         puts("TIOCM_DTR is not set");
 770     close(fd);
 771 }
 772 .EE
 773 .PP
 774 Get or set arbitrary baudrate on the serial port.
 775 .PP
 776 .EX
 777 /* SPDX-License-Identifier: GPL-2.0-or-later */
 778
 779 #include <asm/termbits.h>
 780 #include <fcntl.h>
 781 #include <stdio.h>
 782 #include <stdlib.h>
 783 #include <sys/ioctl.h>
 784 #include <sys/types.h>
 785 #include <unistd.h>
 786
 787 int
 788 main(int argc, char *argv[])
 789 {
 790 #if !defined BOTHER
 791     fprintf(stderr, "BOTHER is unsupported\en");
 792     /* Program may fallback to TCGETS/TCSETS with Bnnn constants */
 793     exit(EXIT_FAILURE);
 794 #else
 795     /* Declare tio structure, its type depends on supported ioctl */
 796 # if defined TCGETS2
 797     struct termios2 tio;
 798 # else
 799     struct termios tio;
 800 # endif
 801     int fd, rc;
 802
 803     if (argc != 2 && argc != 3 && argc != 4) {
 804         fprintf(stderr, "Usage: %s device [output [input] ]\en", argv[0]);
 805         exit(EXIT_FAILURE);
 806     }
 807
 808     fd = open(argv[1], O_RDWR | O_NONBLOCK | O_NOCTTY);
 809     if (fd < 0) {
 810         perror("open");
 811         exit(EXIT_FAILURE);
 812     }
 813
 814     /* Get the current serial port settings via supported ioctl */
 815 # if defined TCGETS2
 816     rc = ioctl(fd, TCGETS2, &tio);
 817 # else
 818     rc = ioctl(fd, TCGETS, &tio);
 819 # endif
 820     if (rc) {
 821         perror("TCGETS");
 822         close(fd);
 823         exit(EXIT_FAILURE);
 824     }
 825
 826     /* Change baud rate when more arguments were provided */
 827     if (argc == 3 || argc == 4) {
 828         /* Clear the current output baud rate and fill a new value */
 829         tio.c_cflag &= ~CBAUD;
 830         tio.c_cflag |= BOTHER;
 831         tio.c_ospeed = atoi(argv[2]);
 832
 833         /* Clear the current input baud rate and fill a new value */
 834         tio.c_cflag &= ~(CBAUD << IBSHIFT);
 835         tio.c_cflag |= BOTHER << IBSHIFT;
 836         /* When 4th argument is not provided reuse output baud rate */
 837         tio.c_ispeed = (argc == 4) ? atoi(argv[3]) : atoi(argv[2]);
 838
 839         /* Set new serial port settings via supported ioctl */
 840 # if defined TCSETS2
 841         rc = ioctl(fd, TCSETS2, &tio);
 842 # else
 843         rc = ioctl(fd, TCSETS, &tio);
 844 # endif
 845         if (rc) {
 846             perror("TCSETS");
 847             close(fd);
 848             exit(EXIT_FAILURE);
 849         }
 850
 851         /* And get new values which were really configured */
 852 # if defined TCGETS2
 853         rc = ioctl(fd, TCGETS2, &tio);
 854 # else
 855         rc = ioctl(fd, TCGETS, &tio);
 856 # endif
 857         if (rc) {
 858             perror("TCGETS");
 859             close(fd);
 860             exit(EXIT_FAILURE);
 861         }
 862     }
 863
 864     close(fd);
 865
 866     printf("output baud rate: %u\en", tio.c_ospeed);
 867     printf("input baud rate: %u\en", tio.c_ispeed);
 868
 869     exit(EXIT_SUCCESS);
 870 #endif
 871 }
 872 .EE
 873 .SH SEE ALSO
 874 .BR ldattach (8),
 875 .BR ioctl (2),
 876 .BR ioctl_console (2),
 877 .BR termios (3),
 878 .BR pty (7)
 879 .\"
 880 .\" FIONBIO                     const int *
 881 .\" FIONCLEX                    void
 882 .\" FIOCLEX                     void
 883 .\" FIOASYNC                    const int *
 884 .\" from serial.c:
 885 .\" TIOCSERCONFIG               void
 886 .\" TIOCSERGWILD                int *
 887 .\" TIOCSERSWILD                const int *
 888 .\" TIOCSERGSTRUCT              struct async_struct *
 889 .\" TIOCSERGETLSR               int *
 890 .\" TIOCSERGETMULTI             struct serial_multiport_struct *
 891 .\" TIOCSERSETMULTI             const struct serial_multiport_struct *
 892 .\" TIOCGSERIAL, TIOCSSERIAL (see above)