man4/console_ioctl.4

   1 .\" Copyright (c) 1995 Jim Van Zandt <jrv@vanzandt.mv.com> and aeb
   2 .\" Sun Feb 26 11:46:23 MET 1995
   3 .\"
   4 .\" %%%LICENSE_START(GPLv2+_DOC_FULL)
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   6 .\" modify it under the terms of the GNU General Public License as
   7 .\" published by the Free Software Foundation; either version 2 of
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  10 .\" The GNU General Public License's references to "object code"
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  15 .\" This manual is distributed in the hope that it will be useful,
  16 .\" but WITHOUT ANY WARRANTY; without even the implied warranty of
  17 .\" MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  18 .\" GNU General Public License for more details.
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  24 .\"
  25 .\" Modified, Sun Feb 26 15:04:20 1995, faith@cs.unc.edu
  26 .\" Modified, Thu Apr 20 22:08:17 1995, jrv@vanzandt.mv.com
  27 .\" Modified, Mon Sep 18 22:32:47 1995, hpa@storm.net (H. Peter Anvin)
  28 .\" FIXME The following are not documented:
  29 .\"     KDFONTOP (since 2.1.111)
  30 .\"     KDGKBDIACRUC (since 2.6.24)
  31 .\"     KDSKBDIACR
  32 .\"     KDSKBDIACRUC (since 2.6.24)
  33 .\"     KDKBDREP (since 2.1.113)
  34 .\"     KDMAPDISP (not implemented as at 2.6.27)
  35 .\"     KDUNMAPDISP (not implemented as at 2.6.27)
  36 .\"     VT_LOCKSWITCH (since 1.3.47, needs CAP_SYS_TTY_CONFIG)
  37 .\"     VT_UNLOCKSWITCH (since 1.3.47, needs CAP_SYS_TTY_CONFIG)
  38 .\"     VT_GETHIFONTMASK (since 2.6.18)
  39 .\"
  40 .TH CONSOLE_IOCTL 4 2016-07-17 "Linux" "Linux Programmer's Manual"
  41 .SH NAME
  42 console_ioctl \- ioctls for console terminal and virtual consoles
  43 .SH DESCRIPTION
  44 The following Linux-specific
  45 .BR ioctl (2)
  46 requests are supported.
  47 Each requires a third argument, assumed here to be
  48 .IR argp .
  49 .TP
  50 .B KDGETLED
  51 Get state of LEDs.
  52 .I argp
  53 points to a
  54 .IR char .
  55 The lower three bits
  56 of
  57 .I *argp
  58 are set to the state of the LEDs, as follows:
  59 .TS
  60 l l l.
  61 LED_CAP         0x04    caps lock led
  62 LED_NUM         0x02    num lock led
  63 LED_SCR         0x01    scroll lock led
  64 .TE
  65 .TP
  66 .B KDSETLED
  67 Set the LEDs.
  68 The LEDs are set to correspond to the lower three bits of
  69 .IR argp .
  70 However, if a higher order bit is set,
  71 the LEDs revert to normal: displaying the state of the
  72 keyboard functions of caps lock, num lock, and scroll lock.
  73 .LP
  74 Before Linux 1.1.54, the LEDs just reflected the state of the corresponding
  75 keyboard flags, and KDGETLED/KDSETLED would also change the keyboard
  76 flags.
  77 Since Linux 1.1.54 the LEDs can be made to display arbitrary
  78 information, but by default they display the keyboard flags.
  79 The following two ioctls are used to access the keyboard flags.
  80 .TP
  81 .B KDGKBLED
  82 Get keyboard flags CapsLock, NumLock, ScrollLock (not lights).
  83 .I argp
  84 points to a char which is set to the flag state.
  85 The low order three bits (mask 0x7) get the current flag state,
  86 and the low order bits of the next nibble (mask 0x70) get
  87 the default flag state.
  88 (Since Linux 1.1.54.)
  89 .TP
  90 .B KDSKBLED
  91 Set keyboard flags CapsLock, NumLock, ScrollLock (not lights).
  92 .I argp
  93 has the desired flag state.
  94 The low order three bits (mask 0x7) have the flag state,
  95 and the low order bits of the next nibble (mask 0x70) have
  96 the default flag state.
  97 (Since Linux 1.1.54.)
  98 .TP
  99 .B KDGKBTYPE
 100 Get keyboard type.
 101 This returns the value KB_101, defined as 0x02.
 102 .TP
 103 .B KDADDIO
 104 Add I/O port as valid.
 105 Equivalent to
 106 .IR ioperm(arg,1,1) .
 107 .TP
 108 .B KDDELIO
 109 Delete I/O port as valid.
 110 Equivalent to
 111 .IR ioperm(arg,1,0) .
 112 .TP
 113 .B KDENABIO
 114 Enable I/O to video board.
 115 Equivalent to
 116 .IR "ioperm(0x3b4, 0x3df-0x3b4+1, 1)" .
 117 .TP
 118 .B KDDISABIO
 119 Disable I/O to video board.
 120 Equivalent to
 121 .IR "ioperm(0x3b4, 0x3df-0x3b4+1, 0)" .
 122 .TP
 123 .B KDSETMODE
 124 Set text/graphics mode.
 125 .I argp
 126 is one of these:
 127 .TS
 128 l l.
 129 KD_TEXT 0x00
 130 KD_GRAPHICS     0x01
 131 .TE
 132 .TP
 133 .B KDGETMODE
 134 Get text/graphics mode.
 135 .I argp
 136 points to an
 137 .I int
 138 which is set to one
 139 of the above values.
 140 .TP
 141 .B KDMKTONE
 142 Generate tone of specified length.
 143 The lower 16 bits of
 144 .I argp
 145 specify the period in clock cycles,
 146 and the upper 16 bits give the duration in msec.
 147 If the duration is zero, the sound is turned off.
 148 Control returns immediately.
 149 For example,
 150 .I argp
 151 = (125<<16) + 0x637 would specify
 152 the beep normally associated with a ctrl-G.
 153 (Thus since Linux 0.99pl1; broken in Linux 2.1.49-50.)
 154 .TP
 155 .B KIOCSOUND
 156 Start or stop sound generation.
 157 The lower 16 bits of
 158 .I argp
 159 specify the period in clock cycles
 160 (that is,
 161 .I argp
 162 = 1193180/frequency).
 163 .I argp
 164 = 0 turns sound off.
 165 In either case, control returns immediately.
 166 .TP
 167 .B GIO_CMAP
 168 Get the current default color map from kernel.
 169 .I argp
 170 points to
 171 a 48-byte array.
 172 (Since Linux 1.3.3.)
 173 .TP
 174 .B PIO_CMAP
 175 Change the default text-mode color map.
 176 .I argp
 177 points to a
 178 48-byte array which contains, in order, the Red, Green, and Blue
 179 values for the 16 available screen colors: 0 is off, and 255 is full
 180 intensity.
 181 The default colors are, in order: black, dark red, dark
 182 green, brown, dark blue, dark purple, dark cyan, light grey, dark
 183 grey, bright red, bright green, yellow, bright blue, bright purple,
 184 bright cyan and white.
 185 (Since Linux 1.3.3.)
 186 .TP
 187 .B GIO_FONT
 188 Gets 256-character screen font in expanded form.
 189 .I argp
 190 points to an 8192 byte array.
 191 Fails with error code
 192 .B EINVAL
 193 if the
 194 currently loaded font is a 512-character font, or if the console is
 195 not in text mode.
 196 .TP
 197 .B GIO_FONTX
 198 Gets screen font and associated information.
 199 .I argp
 200 points to a
 201 .I "struct consolefontdesc"
 202 (see
 203 .BR PIO_FONTX ).
 204 On call, the
 205 .I charcount
 206 field should be set to the maximum number of
 207 characters that would fit in the buffer pointed to by
 208 .IR chardata .
 209 On return, the
 210 .I charcount
 211 and
 212 .I charheight
 213 are filled with
 214 the respective data for the currently loaded font, and the
 215 .I chardata
 216 array contains the font data if the initial value of
 217 .I charcount
 218 indicated enough space was available; otherwise the
 219 buffer is untouched and
 220 .I errno
 221 is set to
 222 .BR ENOMEM .
 223 (Since Linux 1.3.1.)
 224 .TP
 225 .B PIO_FONT
 226 Sets 256-character screen font.
 227 Load font into the EGA/VGA character
 228 generator.
 229 .I argp
 230 points to a 8192 byte map, with 32 bytes per
 231 character.
 232 Only the first
 233 .I N
 234 of them are used for an 8x\fIN\fP font
 235 (0 <
 236 .I N
 237 <= 32).
 238 This call also invalidates the Unicode mapping.
 239 .TP
 240 .B PIO_FONTX
 241 Sets screen font and associated rendering information.
 242 .I argp
 243 points to a
 244
 245 .in +4n
 246 .nf
 247 struct consolefontdesc {
 248     unsigned short charcount;  /* characters in font
 249                                   (256 or 512) */
 250     unsigned short charheight; /* scan lines per
 251                                   character (1-32) */
 252     char          *chardata;   /* font data in
 253                                   expanded form */
 254 };
 255 .fi
 256 .in
 257
 258 If necessary, the screen will be appropriately resized, and
 259 .B SIGWINCH
 260 sent to the appropriate processes.
 261 This call also invalidates the Unicode mapping.
 262 (Since Linux 1.3.1.)
 263 .TP
 264 .B PIO_FONTRESET
 265 Resets the screen font, size and Unicode mapping to the bootup
 266 defaults.
 267 .I argp
 268 is unused, but should be set to NULL to
 269 ensure compatibility with future versions of Linux.
 270 (Since Linux 1.3.28.)
 271 .TP
 272 .B GIO_SCRNMAP
 273 Get screen mapping from kernel.
 274 .I argp
 275 points to an area of size
 276 E_TABSZ, which is loaded with the font positions used to display each
 277 character.
 278 This call is likely to return useless information if the
 279 currently loaded font is more than 256 characters.
 280 .TP
 281 .B GIO_UNISCRNMAP
 282 Get full Unicode screen mapping from kernel.
 283 .I argp
 284 points to an
 285 area of size
 286 .IR "E_TABSZ*sizeof(unsigned short)" ,
 287 which is loaded with the
 288 Unicodes each character represent.
 289 A special set of Unicodes,
 290 starting at U+F000, are used to represent "direct to font" mappings.
 291 (Since Linux 1.3.1.)
 292 .TP
 293 .B PIO_SCRNMAP
 294 Loads the "user definable" (fourth) table in the kernel which maps
 295 bytes into console screen symbols.
 296 .I argp
 297 points to an area of
 298 size E_TABSZ.
 299 .TP
 300 .B PIO_UNISCRNMAP
 301 Loads the "user definable" (fourth) table in the kernel which maps
 302 bytes into Unicodes, which are then translated into screen symbols
 303 according to the currently loaded Unicode-to-font map.
 304 Special Unicodes starting at U+F000 can be used to map directly to the font
 305 symbols.
 306 (Since Linux 1.3.1.)
 307 .TP
 308 .B GIO_UNIMAP
 309 Get Unicode-to-font mapping from kernel.
 310 .I argp
 311 points to a
 312
 313 .in +4n
 314 .nf
 315 struct unimapdesc {
 316     unsigned short  entry_ct;
 317     struct unipair *entries;
 318 };
 319 .fi
 320 .in
 321
 322 where
 323 .I entries
 324 points to an array of
 325
 326 .in +4n
 327 .nf
 328 struct unipair {
 329     unsigned short unicode;
 330     unsigned short fontpos;
 331 };
 332 .fi
 333 .in
 334
 335 (Since Linux 1.1.92.)
 336 .TP
 337 .B PIO_UNIMAP
 338 Put unicode-to-font mapping in kernel.
 339 .I argp
 340 points to a
 341 .IR "struct unimapdesc" .
 342 (Since Linux 1.1.92)
 343 .TP
 344 .B PIO_UNIMAPCLR
 345 Clear table, possibly advise hash algorithm.
 346 .I argp
 347 points to a
 348
 349 .in +4n
 350 .nf
 351 struct unimapinit {
 352     unsigned short advised_hashsize;  /* 0 if no opinion */
 353     unsigned short advised_hashstep;  /* 0 if no opinion */
 354     unsigned short advised_hashlevel; /* 0 if no opinion */
 355 };
 356 .fi
 357 .in
 358
 359 (Since Linux 1.1.92.)
 360 .TP
 361 .B KDGKBMODE
 362 Gets current keyboard mode.
 363 .I argp
 364 points to a
 365 .I long
 366 which is set to one
 367 of these:
 368 .TS
 369 l l.
 370 K_RAW   0x00
 371 K_XLATE 0x01
 372 K_MEDIUMRAW     0x02
 373 K_UNICODE       0x03
 374 .TE
 375 .TP
 376 .B KDSKBMODE
 377 Sets current keyboard mode.
 378 .I argp
 379 is a
 380 .I long
 381 equal to one of the above values.
 382 .TP
 383 .B KDGKBMETA
 384 Gets meta key handling mode.
 385 .I argp
 386 points to a
 387 .I long
 388 which is
 389 set to one of these:
 390 .TS
 391 l l l.
 392 K_METABIT       0x03    set high order bit
 393 K_ESCPREFIX     0x04    escape prefix
 394 .TE
 395 .TP
 396 .B KDSKBMETA
 397 Sets meta key handling mode.
 398 .I argp
 399 is a
 400 .I long
 401 equal to one of the above values.
 402 .TP
 403 .B KDGKBENT
 404 Gets one entry in key translation table (keycode to action code).
 405 .I argp
 406 points to a
 407
 408 .in +4n
 409 .nf
 410 struct kbentry {
 411     unsigned char  kb_table;
 412     unsigned char  kb_index;
 413     unsigned short kb_value;
 414 };
 415 .fi
 416 .in
 417
 418 with the first two members filled in:
 419 .I kb_table
 420 selects the key table (0 <=
 421 .I kb_table
 422 < MAX_NR_KEYMAPS),
 423 and
 424 .IR kb_index
 425 is the keycode (0 <=
 426 .I kb_index
 427 < NR_KEYS).
 428 .I kb_value
 429 is set to the corresponding action code,
 430 or K_HOLE if there is no such key,
 431 or K_NOSUCHMAP if
 432 .I kb_table
 433 is invalid.
 434 .TP
 435 .B KDSKBENT
 436 Sets one entry in translation table.
 437 .I argp
 438 points to a
 439 .IR "struct kbentry" .
 440 .TP
 441 .B KDGKBSENT
 442 Gets one function key string.
 443 .I argp
 444 points to a
 445
 446 .in +4n
 447 .nf
 448 struct kbsentry {
 449     unsigned char kb_func;
 450     unsigned char kb_string[512];
 451 };
 452 .fi
 453 .in
 454
 455 .I kb_string
 456 is set to the (null-terminated) string corresponding to
 457 the
 458 .IR kb_func th
 459 function key action code.
 460 .TP
 461 .B KDSKBSENT
 462 Sets one function key string entry.
 463 .I argp
 464 points to a
 465 .IR "struct kbsentry" .
 466 .TP
 467 .B KDGKBDIACR
 468 Read kernel accent table.
 469 .I argp
 470 points to a
 471
 472 .in +4n
 473 .nf
 474 struct kbdiacrs {
 475     unsigned int   kb_cnt;
 476     struct kbdiacr kbdiacr[256];
 477 };
 478 .fi
 479 .in
 480
 481 where
 482 .I kb_cnt
 483 is the number of entries in the array, each of which
 484 is a
 485
 486 .in +4n
 487 .nf
 488 struct kbdiacr {
 489     unsigned char diacr;
 490     unsigned char base;
 491     unsigned char result;
 492 };
 493 .fi
 494 .in
 495 .TP
 496 .B KDGETKEYCODE
 497 Read kernel keycode table entry (scan code to keycode).
 498 .I argp
 499 points to a
 500
 501 .in +4n
 502 .nf
 503 struct kbkeycode {
 504     unsigned int scancode;
 505     unsigned int keycode;
 506 };
 507 .fi
 508 .in
 509
 510 .I keycode
 511 is set to correspond to the given
 512 .IR scancode .
 513 (89 <=
 514 .I scancode
 515 <= 255 only.
 516 For 1 <=
 517 .I scancode
 518 <= 88,
 519 .IR keycode == scancode .)
 520 (Since Linux 1.1.63.)
 521 .TP
 522 .B KDSETKEYCODE
 523 Write kernel keycode table entry.
 524 .I argp
 525 points to a
 526 .IR "struct kbkeycode" .
 527 (Since Linux 1.1.63.)
 528 .TP
 529 .B KDSIGACCEPT
 530 The calling process indicates its willingness to accept the signal
 531 .I argp
 532 when it is generated by pressing an appropriate key combination.
 533 (1 <=
 534 .I argp
 535 <= NSIG).
 536 (See
 537 .IR spawn_console ()
 538 in
 539 .IR linux/drivers/char/keyboard.c .)
 540 .TP
 541 .B VT_OPENQRY
 542 Returns the first available (non-opened) console.
 543 .I argp
 544 points to an
 545 .I int
 546 which is set to the
 547 number of the vt (1 <=
 548 .I *argp
 549 <= MAX_NR_CONSOLES).
 550 .TP
 551 .B VT_GETMODE
 552 Get mode of active vt.
 553 .I argp
 554 points to a
 555
 556 .in +4n
 557 .nf
 558 struct vt_mode {
 559     char  mode;    /* vt mode */
 560     char  waitv;   /* if set, hang on writes if not active */
 561     short relsig;  /* signal to raise on release req */
 562     short acqsig;  /* signal to raise on acquisition */
 563     short frsig;   /* unused (set to 0) */
 564 };
 565 .fi
 566 .in
 567
 568 which is set to the mode of the active vt.
 569 .I mode
 570 is set to one of these values:
 571 .TS
 572 l l.
 573 VT_AUTO auto vt switching
 574 VT_PROCESS      process controls switching
 575 VT_ACKACQ       acknowledge switch
 576 .TE
 577 .TP
 578 .B VT_SETMODE
 579 Set mode of active vt.
 580 .I argp
 581 points to a
 582 .IR "struct vt_mode" .
 583 .TP
 584 .B VT_GETSTATE
 585 Get global vt state info.
 586 .I argp
 587 points to a
 588
 589 .in +4n
 590 .nf
 591 struct vt_stat {
 592     unsigned short v_active;  /* active vt */
 593     unsigned short v_signal;  /* signal to send */
 594     unsigned short v_state;   /* vt bit mask */
 595 };
 596 .fi
 597 .in
 598
 599 For each vt in use, the corresponding bit in the
 600 .I v_state
 601 member is set.
 602 (Kernels 1.0 through 1.1.92.)
 603 .TP
 604 .B VT_RELDISP
 605 Release a display.
 606 .TP
 607 .B VT_ACTIVATE
 608 Switch to vt
 609 .IR argp
 610 (1 <=
 611 .I argp
 612 <= MAX_NR_CONSOLES).
 613 .TP
 614 .B VT_WAITACTIVE
 615 Wait until vt
 616 .I argp
 617 has been activated.
 618 .TP
 619 .B VT_DISALLOCATE
 620 Deallocate the memory associated with vt
 621 .IR argp .
 622 (Since Linux 1.1.54.)
 623 .TP
 624 .B VT_RESIZE
 625 Set the kernel's idea of screensize.
 626 .I argp
 627 points to a
 628
 629 .in +4n
 630 .nf
 631 struct vt_sizes {
 632     unsigned short v_rows;       /* # rows */
 633     unsigned short v_cols;       /* # columns */
 634     unsigned short v_scrollsize; /* no longer used */
 635 };
 636 .fi
 637 .in
 638
 639 Note that this does not change the videomode.
 640 See
 641 .BR resizecons (8).
 642 (Since Linux 1.1.54.)
 643 .TP
 644 .B VT_RESIZEX
 645 Set the kernel's idea of various screen parameters.
 646 .I argp
 647 points to a
 648
 649 .in +4n
 650 .nf
 651 struct vt_consize {
 652     unsigned short v_rows;  /* number of rows */
 653     unsigned short v_cols;  /* number of columns */
 654     unsigned short v_vlin;  /* number of pixel rows
 655                                on screen */
 656     unsigned short v_clin;  /* number of pixel rows
 657                                per character */
 658     unsigned short v_vcol;  /* number of pixel columns
 659                                on screen */
 660     unsigned short v_ccol;  /* number of pixel columns
 661                                per character */
 662 };
 663 .fi
 664 .in
 665
 666 Any parameter may be set to zero, indicating "no change", but if
 667 multiple parameters are set, they must be self-consistent.
 668 Note that this does not change the videomode.
 669 See
 670 .BR resizecons (8).
 671 (Since Linux 1.3.3.)
 672 .PP
 673 The action of the following ioctls depends on the first byte in the struct
 674 pointed to by
 675 .IR argp ,
 676 referred to here as the
 677 .IR subcode .
 678 These are legal only for the superuser or the owner of the current terminal.
 679 .TP
 680 .B "TIOCLINUX, subcode=0"
 681 Dump the screen.
 682 Disappeared in Linux 1.1.92.  (With kernel 1.1.92 or later, read from
 683 .I /dev/vcsN
 684 or
 685 .I /dev/vcsaN
 686 instead.)
 687 .TP
 688 .B "TIOCLINUX, subcode=1"
 689 Get task information.
 690 Disappeared in Linux 1.1.92.
 691 .TP
 692 .B "TIOCLINUX, subcode=2"
 693 Set selection.
 694 .I argp
 695 points to a
 696 .in +4n
 697 .nf
 698
 699 struct {
 700    char  subcode;
 701    short xs, ys, xe, ye;
 702    short sel_mode;
 703 };
 704
 705 .fi
 706 .in
 707 .I xs
 708 and
 709 .I ys
 710 are the starting column and row.
 711 .I xe
 712 and
 713 .I ye
 714 are the ending
 715 column and row.
 716 (Upper left corner is row=column=1.)
 717 .I sel_mode
 718 is 0 for character-by-character selection,
 719 1 for word-by-word selection,
 720 or 2 for line-by-line selection.
 721 The indicated screen characters are highlighted and saved
 722 in the static array sel_buffer in
 723 .IR devices/char/console.c .
 724 .TP
 725 .B "TIOCLINUX, subcode=3"
 726 Paste selection.
 727 The characters in the selection buffer are
 728 written to
 729 .IR fd .
 730 .TP
 731 .B "TIOCLINUX, subcode=4"
 732 Unblank the screen.
 733 .TP
 734 .B "TIOCLINUX, subcode=5"
 735 Sets contents of a 256-bit look up table defining characters in a "word",
 736 for word-by-word selection.
 737 (Since Linux 1.1.32.)
 738 .TP
 739 .B "TIOCLINUX, subcode=6"
 740 .I argp
 741 points to a char which is set to the value of the kernel
 742 variable
 743 .IR shift_state .
 744 (Since Linux 1.1.32.)
 745 .TP
 746 .B "TIOCLINUX, subcode=7"
 747 .I argp
 748 points to a char which is set to the value of the kernel
 749 variable
 750 .IR report_mouse .
 751 (Since Linux 1.1.33.)
 752 .TP
 753 .B "TIOCLINUX, subcode=8"
 754 Dump screen width and height, cursor position, and all the
 755 character-attribute pairs.
 756 (Kernels 1.1.67 through 1.1.91 only.
 757 With kernel 1.1.92 or later, read from
 758 .I /dev/vcsa*
 759 instead.)
 760 .TP
 761 .B "TIOCLINUX, subcode=9"
 762 Restore screen width and height, cursor position, and all the
 763 character-attribute pairs.
 764 (Kernels 1.1.67 through 1.1.91 only.
 765 With kernel 1.1.92 or later, write to
 766 .I /dev/vcsa*
 767 instead.)
 768 .TP
 769 .B "TIOCLINUX, subcode=10"
 770 Handles the Power Saving
 771 feature of the new generation of monitors.
 772 VESA screen blanking mode is set to
 773 .IR argp[1] ,
 774 which governs what
 775 screen blanking does:
 776 .RS
 777 .IP 0: 3
 778 Screen blanking is disabled.
 779 .IP 1:
 780 The current video adapter
 781 register settings are saved, then the controller is programmed to turn off
 782 the vertical synchronization pulses.
 783 This puts the monitor into "standby" mode.
 784 If your monitor has an Off_Mode timer, then
 785 it will eventually power down by itself.
 786 .IP 2:
 787 The current settings are saved, then both the vertical and horizontal
 788 synchronization pulses are turned off.
 789 This puts the monitor into "off" mode.
 790 If your monitor has no Off_Mode timer,
 791 or if you want your monitor to power down immediately when the
 792 blank_timer times out, then you choose this option.
 793 .RI ( Caution:
 794 Powering down frequently will damage the monitor.)
 795 (Since Linux 1.1.76.)
 796 .RE
 797 .SH RETURN VALUE
 798 On success, 0 is returned.
 799 On error, \-1 is returned, and
 800 .I errno
 801 is set.
 802 .SH ERRORS
 803 .I errno
 804 may take on these values:
 805 .TP
 806 .B EBADF
 807 The file descriptor is invalid.
 808 .TP
 809 .B ENOTTY
 810 The file descriptor is not associated with a character special device,
 811 or the specified request does not apply to it.
 812 .TP
 813 .B EINVAL
 814 The file descriptor or
 815 .I argp
 816 is invalid.
 817 .TP
 818 .B EPERM
 819 Insufficient permission.
 820 .SH NOTES
 821 .BR Warning :
 822 Do not regard this man page as documentation of the Linux console ioctls.
 823 This is provided for the curious only, as an alternative to reading the
 824 source.
 825 Ioctl's are undocumented Linux internals, liable to be changed
 826 without warning.
 827 (And indeed, this page more or less describes the
 828 situation as of kernel version 1.1.94;
 829 there are many minor and not-so-minor
 830 differences with earlier versions.)
 831
 832 Very often, ioctls are introduced for communication between the
 833 kernel and one particular well-known program (fdisk, hdparm, setserial,
 834 tunelp, loadkeys, selection, setfont, etc.), and their behavior will be
 835 changed when required by this particular program.
 836
 837 Programs using these ioctls will not be portable to other versions
 838 of UNIX, will not work on older versions of Linux, and will not work
 839 on future versions of Linux.
 840
 841 Use POSIX functions.
 842 .SH SEE ALSO
 843 .BR dumpkeys (1),
 844 .BR kbd_mode (1),
 845 .BR loadkeys (1),
 846 .BR mknod (1),
 847 .BR setleds (1),
 848 .BR setmetamode (1),
 849 .BR execve (2),
 850 .BR fcntl (2),
 851 .BR ioperm (2),
 852 .BR termios (3),
 853 .BR console_codes (4),
 854 .BR mt (4),
 855 .BR sd (4),
 856 .BR tty (4),
 857 .BR tty_ioctl (4),
 858 .BR ttyS (4),
 859 .BR vcs (4),
 860 .BR vcsa (4),
 861 .BR charsets (7),
 862 .BR mapscrn (8),
 863 .BR resizecons (8),
 864 .BR setfont (8)
 865
 866 .IR /usr/include/linux/kd.h ,
 867 .I /usr/include/linux/vt.h