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)
   5 .\" This is free documentation; you can redistribute it and/or
   6 .\" modify it under the terms of the GNU General Public License as
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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 values shown above for
 140 .BR KDSETMODE .
 141 .TP
 142 .B KDMKTONE
 143 Generate tone of specified length.
 144 The lower 16 bits of
 145 .I argp
 146 specify the period in clock cycles,
 147 and the upper 16 bits give the duration in msec.
 148 If the duration is zero, the sound is turned off.
 149 Control returns immediately.
 150 For example,
 151 .I argp
 152 = (125<<16) + 0x637 would specify
 153 the beep normally associated with a ctrl-G.
 154 (Thus since Linux 0.99pl1; broken in Linux 2.1.49-50.)
 155 .TP
 156 .B KIOCSOUND
 157 Start or stop sound generation.
 158 The lower 16 bits of
 159 .I argp
 160 specify the period in clock cycles
 161 (that is,
 162 .I argp
 163 = 1193180/frequency).
 164 .I argp
 165 = 0 turns sound off.
 166 In either case, control returns immediately.
 167 .TP
 168 .B GIO_CMAP
 169 Get the current default color map from kernel.
 170 .I argp
 171 points to
 172 a 48-byte array.
 173 (Since Linux 1.3.3.)
 174 .TP
 175 .B PIO_CMAP
 176 Change the default text-mode color map.
 177 .I argp
 178 points to a
 179 48-byte array which contains, in order, the Red, Green, and Blue
 180 values for the 16 available screen colors: 0 is off, and 255 is full
 181 intensity.
 182 The default colors are, in order: black, dark red, dark
 183 green, brown, dark blue, dark purple, dark cyan, light grey, dark
 184 grey, bright red, bright green, yellow, bright blue, bright purple,
 185 bright cyan and white.
 186 (Since Linux 1.3.3.)
 187 .TP
 188 .B GIO_FONT
 189 Gets 256-character screen font in expanded form.
 190 .I argp
 191 points to an 8192 byte array.
 192 Fails with error code
 193 .B EINVAL
 194 if the
 195 currently loaded font is a 512-character font, or if the console is
 196 not in text mode.
 197 .TP
 198 .B GIO_FONTX
 199 Gets screen font and associated information.
 200 .I argp
 201 points to a
 202 .I "struct consolefontdesc"
 203 (see
 204 .BR PIO_FONTX ).
 205 On call, the
 206 .I charcount
 207 field should be set to the maximum number of
 208 characters that would fit in the buffer pointed to by
 209 .IR chardata .
 210 On return, the
 211 .I charcount
 212 and
 213 .I charheight
 214 are filled with
 215 the respective data for the currently loaded font, and the
 216 .I chardata
 217 array contains the font data if the initial value of
 218 .I charcount
 219 indicated enough space was available; otherwise the
 220 buffer is untouched and
 221 .I errno
 222 is set to
 223 .BR ENOMEM .
 224 (Since Linux 1.3.1.)
 225 .TP
 226 .B PIO_FONT
 227 Sets 256-character screen font.
 228 Load font into the EGA/VGA character
 229 generator.
 230 .I argp
 231 points to a 8192 byte map, with 32 bytes per
 232 character.
 233 Only the first
 234 .I N
 235 of them are used for an 8x\fIN\fP font
 236 (0 <
 237 .I N
 238 <= 32).
 239 This call also invalidates the Unicode mapping.
 240 .TP
 241 .B PIO_FONTX
 242 Sets screen font and associated rendering information.
 243 .I argp
 244 points to a
 245
 246 .in +4n
 247 .nf
 248 struct consolefontdesc {
 249     unsigned short charcount;  /* characters in font
 250                                   (256 or 512) */
 251     unsigned short charheight; /* scan lines per
 252                                   character (1-32) */
 253     char          *chardata;   /* font data in
 254                                   expanded form */
 255 };
 256 .fi
 257 .in
 258
 259 If necessary, the screen will be appropriately resized, and
 260 .B SIGWINCH
 261 sent to the appropriate processes.
 262 This call also invalidates the Unicode mapping.
 263 (Since Linux 1.3.1.)
 264 .TP
 265 .B PIO_FONTRESET
 266 Resets the screen font, size and Unicode mapping to the bootup
 267 defaults.
 268 .I argp
 269 is unused, but should be set to NULL to
 270 ensure compatibility with future versions of Linux.
 271 (Since Linux 1.3.28.)
 272 .TP
 273 .B GIO_SCRNMAP
 274 Get screen mapping from kernel.
 275 .I argp
 276 points to an area of size
 277 E_TABSZ, which is loaded with the font positions used to display each
 278 character.
 279 This call is likely to return useless information if the
 280 currently loaded font is more than 256 characters.
 281 .TP
 282 .B GIO_UNISCRNMAP
 283 Get full Unicode screen mapping from kernel.
 284 .I argp
 285 points to an
 286 area of size
 287 .IR "E_TABSZ*sizeof(unsigned short)" ,
 288 which is loaded with the
 289 Unicodes each character represent.
 290 A special set of Unicodes,
 291 starting at U+F000, are used to represent "direct to font" mappings.
 292 (Since Linux 1.3.1.)
 293 .TP
 294 .B PIO_SCRNMAP
 295 Loads the "user definable" (fourth) table in the kernel which maps
 296 bytes into console screen symbols.
 297 .I argp
 298 points to an area of
 299 size E_TABSZ.
 300 .TP
 301 .B PIO_UNISCRNMAP
 302 Loads the "user definable" (fourth) table in the kernel which maps
 303 bytes into Unicodes, which are then translated into screen symbols
 304 according to the currently loaded Unicode-to-font map.
 305 Special Unicodes starting at U+F000 can be used to map directly to the font
 306 symbols.
 307 (Since Linux 1.3.1.)
 308 .TP
 309 .B GIO_UNIMAP
 310 Get Unicode-to-font mapping from kernel.
 311 .I argp
 312 points to a
 313
 314 .in +4n
 315 .nf
 316 struct unimapdesc {
 317     unsigned short  entry_ct;
 318     struct unipair *entries;
 319 };
 320 .fi
 321 .in
 322
 323 where
 324 .I entries
 325 points to an array of
 326
 327 .in +4n
 328 .nf
 329 struct unipair {
 330     unsigned short unicode;
 331     unsigned short fontpos;
 332 };
 333 .fi
 334 .in
 335
 336 (Since Linux 1.1.92.)
 337 .TP
 338 .B PIO_UNIMAP
 339 Put unicode-to-font mapping in kernel.
 340 .I argp
 341 points to a
 342 .IR "struct unimapdesc" .
 343 (Since Linux 1.1.92)
 344 .TP
 345 .B PIO_UNIMAPCLR
 346 Clear table, possibly advise hash algorithm.
 347 .I argp
 348 points to a
 349
 350 .in +4n
 351 .nf
 352 struct unimapinit {
 353     unsigned short advised_hashsize;  /* 0 if no opinion */
 354     unsigned short advised_hashstep;  /* 0 if no opinion */
 355     unsigned short advised_hashlevel; /* 0 if no opinion */
 356 };
 357 .fi
 358 .in
 359
 360 (Since Linux 1.1.92.)
 361 .TP
 362 .B KDGKBMODE
 363 Gets current keyboard mode.
 364 .I argp
 365 points to a
 366 .I long
 367 which is set to one
 368 of these:
 369 .TS
 370 l l.
 371 K_RAW   0x00  /* Raw (scancode) mode */
 372 K_XLATE 0x01  /* Translate keycodes using keymap */
 373 K_MEDIUMRAW     0x02  /* Medium raw (scancode) mode */
 374 K_UNICODE       0x03  /* Unicode mode */
 375 K_OFF   0x04  /* Disabled mode; since Linux 2.6.39 */
 376 .\" K_OFF: commit 9fc3de9c83565fcaa23df74c2fc414bb6e7efb0a
 377 .TE
 378 .TP
 379 .B KDSKBMODE
 380 Sets current keyboard mode.
 381 .I argp
 382 is a
 383 .I long
 384 equal to one of the values shown for
 385 .BR KDGKBMODE .
 386 .TP
 387 .B KDGKBMETA
 388 Gets meta key handling mode.
 389 .I argp
 390 points to a
 391 .I long
 392 which is
 393 set to one of these:
 394 .TS
 395 l l l.
 396 K_METABIT       0x03    set high order bit
 397 K_ESCPREFIX     0x04    escape prefix
 398 .TE
 399 .TP
 400 .B KDSKBMETA
 401 Sets meta key handling mode.
 402 .I argp
 403 is a
 404 .I long
 405 equal to one of the values shown above for
 406 .BR KDGKBMETA .
 407 .TP
 408 .B KDGKBENT
 409 Gets one entry in key translation table (keycode to action code).
 410 .I argp
 411 points to a
 412
 413 .in +4n
 414 .nf
 415 struct kbentry {
 416     unsigned char  kb_table;
 417     unsigned char  kb_index;
 418     unsigned short kb_value;
 419 };
 420 .fi
 421 .in
 422
 423 with the first two members filled in:
 424 .I kb_table
 425 selects the key table (0 <=
 426 .I kb_table
 427 < MAX_NR_KEYMAPS),
 428 and
 429 .IR kb_index
 430 is the keycode (0 <=
 431 .I kb_index
 432 < NR_KEYS).
 433 .I kb_value
 434 is set to the corresponding action code,
 435 or K_HOLE if there is no such key,
 436 or K_NOSUCHMAP if
 437 .I kb_table
 438 is invalid.
 439 .TP
 440 .B KDSKBENT
 441 Sets one entry in translation table.
 442 .I argp
 443 points to a
 444 .IR "struct kbentry" .
 445 .TP
 446 .B KDGKBSENT
 447 Gets one function key string.
 448 .I argp
 449 points to a
 450
 451 .in +4n
 452 .nf
 453 struct kbsentry {
 454     unsigned char kb_func;
 455     unsigned char kb_string[512];
 456 };
 457 .fi
 458 .in
 459
 460 .I kb_string
 461 is set to the (null-terminated) string corresponding to
 462 the
 463 .IR kb_func th
 464 function key action code.
 465 .TP
 466 .B KDSKBSENT
 467 Sets one function key string entry.
 468 .I argp
 469 points to a
 470 .IR "struct kbsentry" .
 471 .TP
 472 .B KDGKBDIACR
 473 Read kernel accent table.
 474 .I argp
 475 points to a
 476
 477 .in +4n
 478 .nf
 479 struct kbdiacrs {
 480     unsigned int   kb_cnt;
 481     struct kbdiacr kbdiacr[256];
 482 };
 483 .fi
 484 .in
 485
 486 where
 487 .I kb_cnt
 488 is the number of entries in the array, each of which
 489 is a
 490
 491 .in +4n
 492 .nf
 493 struct kbdiacr {
 494     unsigned char diacr;
 495     unsigned char base;
 496     unsigned char result;
 497 };
 498 .fi
 499 .in
 500 .TP
 501 .B KDGETKEYCODE
 502 Read kernel keycode table entry (scan code to keycode).
 503 .I argp
 504 points to a
 505
 506 .in +4n
 507 .nf
 508 struct kbkeycode {
 509     unsigned int scancode;
 510     unsigned int keycode;
 511 };
 512 .fi
 513 .in
 514
 515 .I keycode
 516 is set to correspond to the given
 517 .IR scancode .
 518 (89 <=
 519 .I scancode
 520 <= 255 only.
 521 For 1 <=
 522 .I scancode
 523 <= 88,
 524 .IR keycode == scancode .)
 525 (Since Linux 1.1.63.)
 526 .TP
 527 .B KDSETKEYCODE
 528 Write kernel keycode table entry.
 529 .I argp
 530 points to a
 531 .IR "struct kbkeycode" .
 532 (Since Linux 1.1.63.)
 533 .TP
 534 .B KDSIGACCEPT
 535 The calling process indicates its willingness to accept the signal
 536 .I argp
 537 when it is generated by pressing an appropriate key combination.
 538 (1 <=
 539 .I argp
 540 <= NSIG).
 541 (See
 542 .IR spawn_console ()
 543 in
 544 .IR linux/drivers/char/keyboard.c .)
 545 .TP
 546 .B VT_OPENQRY
 547 Returns the first available (non-opened) console.
 548 .I argp
 549 points to an
 550 .I int
 551 which is set to the
 552 number of the vt (1 <=
 553 .I *argp
 554 <= MAX_NR_CONSOLES).
 555 .TP
 556 .B VT_GETMODE
 557 Get mode of active vt.
 558 .I argp
 559 points to a
 560
 561 .in +4n
 562 .nf
 563 struct vt_mode {
 564     char  mode;    /* vt mode */
 565     char  waitv;   /* if set, hang on writes if not active */
 566     short relsig;  /* signal to raise on release req */
 567     short acqsig;  /* signal to raise on acquisition */
 568     short frsig;   /* unused (set to 0) */
 569 };
 570 .fi
 571 .in
 572
 573 which is set to the mode of the active vt.
 574 .I mode
 575 is set to one of these values:
 576 .TS
 577 l l.
 578 VT_AUTO auto vt switching
 579 VT_PROCESS      process controls switching
 580 VT_ACKACQ       acknowledge switch
 581 .TE
 582 .TP
 583 .B VT_SETMODE
 584 Set mode of active vt.
 585 .I argp
 586 points to a
 587 .IR "struct vt_mode" .
 588 .TP
 589 .B VT_GETSTATE
 590 Get global vt state info.
 591 .I argp
 592 points to a
 593
 594 .in +4n
 595 .nf
 596 struct vt_stat {
 597     unsigned short v_active;  /* active vt */
 598     unsigned short v_signal;  /* signal to send */
 599     unsigned short v_state;   /* vt bit mask */
 600 };
 601 .fi
 602 .in
 603
 604 For each vt in use, the corresponding bit in the
 605 .I v_state
 606 member is set.
 607 (Kernels 1.0 through 1.1.92.)
 608 .TP
 609 .B VT_RELDISP
 610 Release a display.
 611 .TP
 612 .B VT_ACTIVATE
 613 Switch to vt
 614 .IR argp
 615 (1 <=
 616 .I argp
 617 <= MAX_NR_CONSOLES).
 618 .TP
 619 .B VT_WAITACTIVE
 620 Wait until vt
 621 .I argp
 622 has been activated.
 623 .TP
 624 .B VT_DISALLOCATE
 625 Deallocate the memory associated with vt
 626 .IR argp .
 627 (Since Linux 1.1.54.)
 628 .TP
 629 .B VT_RESIZE
 630 Set the kernel's idea of screensize.
 631 .I argp
 632 points to a
 633
 634 .in +4n
 635 .nf
 636 struct vt_sizes {
 637     unsigned short v_rows;       /* # rows */
 638     unsigned short v_cols;       /* # columns */
 639     unsigned short v_scrollsize; /* no longer used */
 640 };
 641 .fi
 642 .in
 643
 644 Note that this does not change the videomode.
 645 See
 646 .BR resizecons (8).
 647 (Since Linux 1.1.54.)
 648 .TP
 649 .B VT_RESIZEX
 650 Set the kernel's idea of various screen parameters.
 651 .I argp
 652 points to a
 653
 654 .in +4n
 655 .nf
 656 struct vt_consize {
 657     unsigned short v_rows;  /* number of rows */
 658     unsigned short v_cols;  /* number of columns */
 659     unsigned short v_vlin;  /* number of pixel rows
 660                                on screen */
 661     unsigned short v_clin;  /* number of pixel rows
 662                                per character */
 663     unsigned short v_vcol;  /* number of pixel columns
 664                                on screen */
 665     unsigned short v_ccol;  /* number of pixel columns
 666                                per character */
 667 };
 668 .fi
 669 .in
 670
 671 Any parameter may be set to zero, indicating "no change", but if
 672 multiple parameters are set, they must be self-consistent.
 673 Note that this does not change the videomode.
 674 See
 675 .BR resizecons (8).
 676 (Since Linux 1.3.3.)
 677 .PP
 678 The action of the following ioctls depends on the first byte in the struct
 679 pointed to by
 680 .IR argp ,
 681 referred to here as the
 682 .IR subcode .
 683 These are legal only for the superuser or the owner of the current terminal.
 684 .TP
 685 .B "TIOCLINUX, subcode=0"
 686 Dump the screen.
 687 Disappeared in Linux 1.1.92.  (With kernel 1.1.92 or later, read from
 688 .I /dev/vcsN
 689 or
 690 .I /dev/vcsaN
 691 instead.)
 692 .TP
 693 .B "TIOCLINUX, subcode=1"
 694 Get task information.
 695 Disappeared in Linux 1.1.92.
 696 .TP
 697 .B "TIOCLINUX, subcode=2"
 698 Set selection.
 699 .I argp
 700 points to a
 701 .in +4n
 702 .nf
 703
 704 struct {
 705    char  subcode;
 706    short xs, ys, xe, ye;
 707    short sel_mode;
 708 };
 709
 710 .fi
 711 .in
 712 .I xs
 713 and
 714 .I ys
 715 are the starting column and row.
 716 .I xe
 717 and
 718 .I ye
 719 are the ending
 720 column and row.
 721 (Upper left corner is row=column=1.)
 722 .I sel_mode
 723 is 0 for character-by-character selection,
 724 1 for word-by-word selection,
 725 or 2 for line-by-line selection.
 726 The indicated screen characters are highlighted and saved
 727 in the static array sel_buffer in
 728 .IR devices/char/console.c .
 729 .TP
 730 .B "TIOCLINUX, subcode=3"
 731 Paste selection.
 732 The characters in the selection buffer are
 733 written to
 734 .IR fd .
 735 .TP
 736 .B "TIOCLINUX, subcode=4"
 737 Unblank the screen.
 738 .TP
 739 .B "TIOCLINUX, subcode=5"
 740 Sets contents of a 256-bit look up table defining characters in a "word",
 741 for word-by-word selection.
 742 (Since Linux 1.1.32.)
 743 .TP
 744 .B "TIOCLINUX, subcode=6"
 745 .I argp
 746 points to a char which is set to the value of the kernel
 747 variable
 748 .IR shift_state .
 749 (Since Linux 1.1.32.)
 750 .TP
 751 .B "TIOCLINUX, subcode=7"
 752 .I argp
 753 points to a char which is set to the value of the kernel
 754 variable
 755 .IR report_mouse .
 756 (Since Linux 1.1.33.)
 757 .TP
 758 .B "TIOCLINUX, subcode=8"
 759 Dump screen width and height, cursor position, and all the
 760 character-attribute pairs.
 761 (Kernels 1.1.67 through 1.1.91 only.
 762 With kernel 1.1.92 or later, read from
 763 .I /dev/vcsa*
 764 instead.)
 765 .TP
 766 .B "TIOCLINUX, subcode=9"
 767 Restore screen width and height, cursor position, and all the
 768 character-attribute pairs.
 769 (Kernels 1.1.67 through 1.1.91 only.
 770 With kernel 1.1.92 or later, write to
 771 .I /dev/vcsa*
 772 instead.)
 773 .TP
 774 .B "TIOCLINUX, subcode=10"
 775 Handles the Power Saving
 776 feature of the new generation of monitors.
 777 VESA screen blanking mode is set to
 778 .IR argp[1] ,
 779 which governs what
 780 screen blanking does:
 781 .RS
 782 .IP 0: 3
 783 Screen blanking is disabled.
 784 .IP 1:
 785 The current video adapter
 786 register settings are saved, then the controller is programmed to turn off
 787 the vertical synchronization pulses.
 788 This puts the monitor into "standby" mode.
 789 If your monitor has an Off_Mode timer, then
 790 it will eventually power down by itself.
 791 .IP 2:
 792 The current settings are saved, then both the vertical and horizontal
 793 synchronization pulses are turned off.
 794 This puts the monitor into "off" mode.
 795 If your monitor has no Off_Mode timer,
 796 or if you want your monitor to power down immediately when the
 797 blank_timer times out, then you choose this option.
 798 .RI ( Caution:
 799 Powering down frequently will damage the monitor.)
 800 (Since Linux 1.1.76.)
 801 .RE
 802 .SH RETURN VALUE
 803 On success, 0 is returned.
 804 On error, \-1 is returned, and
 805 .I errno
 806 is set.
 807 .SH ERRORS
 808 .I errno
 809 may take on these values:
 810 .TP
 811 .B EBADF
 812 The file descriptor is invalid.
 813 .TP
 814 .B EINVAL
 815 The file descriptor or
 816 .I argp
 817 is invalid.
 818 .TP
 819 .B ENOTTY
 820 The file descriptor is not associated with a character special device,
 821 or the specified request does not apply to it.
 822 .TP
 823 .B EPERM
 824 Insufficient permission.
 825 .SH NOTES
 826 .BR Warning :
 827 Do not regard this man page as documentation of the Linux console ioctls.
 828 This is provided for the curious only, as an alternative to reading the
 829 source.
 830 Ioctl's are undocumented Linux internals, liable to be changed
 831 without warning.
 832 (And indeed, this page more or less describes the
 833 situation as of kernel version 1.1.94;
 834 there are many minor and not-so-minor
 835 differences with earlier versions.)
 836
 837 Very often, ioctls are introduced for communication between the
 838 kernel and one particular well-known program (fdisk, hdparm, setserial,
 839 tunelp, loadkeys, selection, setfont, etc.), and their behavior will be
 840 changed when required by this particular program.
 841
 842 Programs using these ioctls will not be portable to other versions
 843 of UNIX, will not work on older versions of Linux, and will not work
 844 on future versions of Linux.
 845
 846 Use POSIX functions.
 847 .SH SEE ALSO
 848 .BR dumpkeys (1),
 849 .BR kbd_mode (1),
 850 .BR loadkeys (1),
 851 .BR mknod (1),
 852 .BR setleds (1),
 853 .BR setmetamode (1),
 854 .BR execve (2),
 855 .BR fcntl (2),
 856 .BR ioperm (2),
 857 .BR termios (3),
 858 .BR console_codes (4),
 859 .BR mt (4),
 860 .BR sd (4),
 861 .BR tty (4),
 862 .BR tty_ioctl (4),
 863 .BR ttyS (4),
 864 .BR vcs (4),
 865 .BR vcsa (4),
 866 .BR charsets (7),
 867 .BR mapscrn (8),
 868 .BR resizecons (8),
 869 .BR setfont (8)
 870
 871 .IR /usr/include/linux/kd.h ,
 872 .I /usr/include/linux/vt.h