man2/ioctl_console.2

   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
   8 .\" the License, or (at your option) any later version.
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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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  20 .\" You should have received a copy of the GNU General Public
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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 IOCTL_CONSOLE 2 2017-09-15 "Linux" "Linux Programmer's Manual"
  41 .SH NAME
  42 ioctl_console \- ioctls for console terminal and virtual consoles
  43 .SH DESCRIPTION
  44 The following Linux-specific
  45 .BR ioctl (2)
  46 requests are supported for console terminals and virtual consoles.
  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 the
  69 unsigned long integer in
  70 .IR argp .
  71 However, if a higher order bit is set,
  72 the LEDs revert to normal: displaying the state of the
  73 keyboard functions of caps lock, num lock, and scroll lock.
  74 .PP
  75 Before Linux 1.1.54, the LEDs just reflected the state of the corresponding
  76 keyboard flags, and KDGETLED/KDSETLED would also change the keyboard
  77 flags.
  78 Since Linux 1.1.54 the LEDs can be made to display arbitrary
  79 information, but by default they display the keyboard flags.
  80 The following two ioctls are used to access the keyboard flags.
  81 .TP
  82 .B KDGKBLED
  83 Get keyboard flags CapsLock, NumLock, ScrollLock (not lights).
  84 .I argp
  85 points to a char which is set to the flag state.
  86 The low order three bits (mask 0x7) get the current flag state,
  87 and the low order bits of the next nibble (mask 0x70) get
  88 the default flag state.
  89 (Since Linux 1.1.54.)
  90 .TP
  91 .B KDSKBLED
  92 Set keyboard flags CapsLock, NumLock, ScrollLock (not lights).
  93 .I argp
  94 is an unsigned long integer that has the desired flag state.
  95 The low order three bits (mask 0x7) have the flag state,
  96 and the low order bits of the next nibble (mask 0x70) have
  97 the default flag state.
  98 (Since Linux 1.1.54.)
  99 .TP
 100 .B KDGKBTYPE
 101 Get keyboard type.
 102 This returns the value KB_101, defined as 0x02.
 103 .TP
 104 .B KDADDIO
 105 Add I/O port as valid.
 106 Equivalent to
 107 .IR ioperm(arg,1,1) .
 108 .TP
 109 .B KDDELIO
 110 Delete I/O port as valid.
 111 Equivalent to
 112 .IR ioperm(arg,1,0) .
 113 .TP
 114 .B KDENABIO
 115 Enable I/O to video board.
 116 Equivalent to
 117 .IR "ioperm(0x3b4, 0x3df\-0x3b4+1, 1)" .
 118 .TP
 119 .B KDDISABIO
 120 Disable I/O to video board.
 121 Equivalent to
 122 .IR "ioperm(0x3b4, 0x3df\-0x3b4+1, 0)" .
 123 .TP
 124 .B KDSETMODE
 125 Set text/graphics mode.
 126 .I argp
 127 is an unsigned integer containing one of:
 128 .TS
 129 l l.
 130 KD_TEXT 0x00
 131 KD_GRAPHICS     0x01
 132 .TE
 133 .TP
 134 .B KDGETMODE
 135 Get text/graphics mode.
 136 .I argp
 137 points to an
 138 .I int
 139 which is set to one
 140 of the values shown above for
 141 .BR KDSETMODE .
 142 .TP
 143 .B KDMKTONE
 144 Generate tone of specified length.
 145 The lower 16 bits of the unsigned long integer in
 146 .I argp
 147 specify the period in clock cycles,
 148 and the upper 16 bits give the duration in msec.
 149 If the duration is zero, the sound is turned off.
 150 Control returns immediately.
 151 For example,
 152 .I argp
 153 = (125<<16) + 0x637 would specify
 154 the beep normally associated with a ctrl-G.
 155 (Thus since Linux 0.99pl1; broken in Linux 2.1.49-50.)
 156 .TP
 157 .B KIOCSOUND
 158 Start or stop sound generation.
 159 The lower 16 bits of
 160 .I argp
 161 specify the period in clock cycles
 162 (that is,
 163 .I argp
 164 = 1193180/frequency).
 165 .I argp
 166 = 0 turns sound off.
 167 In either case, control returns immediately.
 168 .TP
 169 .B GIO_CMAP
 170 Get the current default color map from kernel.
 171 .I argp
 172 points to
 173 a 48-byte array.
 174 (Since Linux 1.3.3.)
 175 .TP
 176 .B PIO_CMAP
 177 Change the default text-mode color map.
 178 .I argp
 179 points to a
 180 48-byte array which contains, in order, the Red, Green, and Blue
 181 values for the 16 available screen colors: 0 is off, and 255 is full
 182 intensity.
 183 The default colors are, in order: black, dark red, dark
 184 green, brown, dark blue, dark purple, dark cyan, light grey, dark
 185 grey, bright red, bright green, yellow, bright blue, bright purple,
 186 bright cyan and white.
 187 (Since Linux 1.3.3.)
 188 .TP
 189 .B GIO_FONT
 190 Gets 256-character screen font in expanded form.
 191 .I argp
 192 points to an 8192-byte array.
 193 Fails with error code
 194 .B EINVAL
 195 if the
 196 currently loaded font is a 512-character font, or if the console is
 197 not in text mode.
 198 .TP
 199 .B GIO_FONTX
 200 Gets screen font and associated information.
 201 .I argp
 202 points to a
 203 .I "struct consolefontdesc"
 204 (see
 205 .BR PIO_FONTX ).
 206 On call, the
 207 .I charcount
 208 field should be set to the maximum number of
 209 characters that would fit in the buffer pointed to by
 210 .IR chardata .
 211 On return, the
 212 .I charcount
 213 and
 214 .I charheight
 215 are filled with
 216 the respective data for the currently loaded font, and the
 217 .I chardata
 218 array contains the font data if the initial value of
 219 .I charcount
 220 indicated enough space was available; otherwise the
 221 buffer is untouched and
 222 .I errno
 223 is set to
 224 .BR ENOMEM .
 225 (Since Linux 1.3.1.)
 226 .TP
 227 .B PIO_FONT
 228 Sets 256-character screen font.
 229 Load font into the EGA/VGA character
 230 generator.
 231 .I argp
 232 points to an 8192-byte map, with 32 bytes per
 233 character.
 234 Only the first
 235 .I N
 236 of them are used for an 8x\fIN\fP font
 237 (0 <
 238 .I N
 239 <= 32).
 240 This call also invalidates the Unicode mapping.
 241 .TP
 242 .B PIO_FONTX
 243 Sets screen font and associated rendering information.
 244 .I argp
 245 points to a
 246 .IP
 247 .in +4n
 248 .EX
 249 struct consolefontdesc {
 250     unsigned short charcount;  /* characters in font
 251                                   (256 or 512) */
 252     unsigned short charheight; /* scan lines per
 253                                   character (1\-32) */
 254     char          *chardata;   /* font data in
 255                                   expanded form */
 256 };
 257 .EE
 258 .in
 259 .IP
 260 If necessary, the screen will be appropriately resized, and
 261 .B SIGWINCH
 262 sent to the appropriate processes.
 263 This call also invalidates the Unicode mapping.
 264 (Since Linux 1.3.1.)
 265 .TP
 266 .B PIO_FONTRESET
 267 Resets the screen font, size and Unicode mapping to the bootup
 268 defaults.
 269 .I argp
 270 is unused, but should be set to NULL to
 271 ensure compatibility with future versions of Linux.
 272 (Since Linux 1.3.28.)
 273 .TP
 274 .B GIO_SCRNMAP
 275 Get screen mapping from kernel.
 276 .I argp
 277 points to an area of size
 278 E_TABSZ, which is loaded with the font positions used to display each
 279 character.
 280 This call is likely to return useless information if the
 281 currently loaded font is more than 256 characters.
 282 .TP
 283 .B GIO_UNISCRNMAP
 284 Get full Unicode screen mapping from kernel.
 285 .I argp
 286 points to an
 287 area of size
 288 .IR "E_TABSZ*sizeof(unsigned short)" ,
 289 which is loaded with the
 290 Unicodes each character represent.
 291 A special set of Unicodes,
 292 starting at U+F000, are used to represent "direct to font" mappings.
 293 (Since Linux 1.3.1.)
 294 .TP
 295 .B PIO_SCRNMAP
 296 Loads the "user definable" (fourth) table in the kernel which maps
 297 bytes into console screen symbols.
 298 .I argp
 299 points to an area of
 300 size E_TABSZ.
 301 .TP
 302 .B PIO_UNISCRNMAP
 303 Loads the "user definable" (fourth) table in the kernel which maps
 304 bytes into Unicodes, which are then translated into screen symbols
 305 according to the currently loaded Unicode-to-font map.
 306 Special Unicodes starting at U+F000 can be used to map directly to the font
 307 symbols.
 308 (Since Linux 1.3.1.)
 309 .TP
 310 .B GIO_UNIMAP
 311 Get Unicode-to-font mapping from kernel.
 312 .I argp
 313 points to a
 314 .IP
 315 .in +4n
 316 .EX
 317 struct unimapdesc {
 318     unsigned short  entry_ct;
 319     struct unipair *entries;
 320 };
 321 .EE
 322 .in
 323 .IP
 324 where
 325 .I entries
 326 points to an array of
 327 .IP
 328 .in +4n
 329 .EX
 330 struct unipair {
 331     unsigned short unicode;
 332     unsigned short fontpos;
 333 };
 334 .EE
 335 .in
 336 .IP
 337 (Since Linux 1.1.92.)
 338 .TP
 339 .B PIO_UNIMAP
 340 Put unicode-to-font mapping in kernel.
 341 .I argp
 342 points to a
 343 .IR "struct unimapdesc" .
 344 (Since Linux 1.1.92)
 345 .TP
 346 .B PIO_UNIMAPCLR
 347 Clear table, possibly advise hash algorithm.
 348 .I argp
 349 points to a
 350 .IP
 351 .in +4n
 352 .EX
 353 struct unimapinit {
 354     unsigned short advised_hashsize;  /* 0 if no opinion */
 355     unsigned short advised_hashstep;  /* 0 if no opinion */
 356     unsigned short advised_hashlevel; /* 0 if no opinion */
 357 };
 358 .EE
 359 .in
 360 .IP
 361 (Since Linux 1.1.92.)
 362 .TP
 363 .B KDGKBMODE
 364 Gets current keyboard mode.
 365 .I argp
 366 points to a
 367 .I long
 368 which is set to one
 369 of these:
 370 .TS
 371 l l.
 372 K_RAW   0x00  /* Raw (scancode) mode */
 373 K_XLATE 0x01  /* Translate keycodes using keymap */
 374 K_MEDIUMRAW     0x02  /* Medium raw (scancode) mode */
 375 K_UNICODE       0x03  /* Unicode mode */
 376 K_OFF   0x04  /* Disabled mode; since Linux 2.6.39 */
 377 .\" K_OFF: commit 9fc3de9c83565fcaa23df74c2fc414bb6e7efb0a
 378 .TE
 379 .TP
 380 .B KDSKBMODE
 381 Sets current keyboard mode.
 382 .I argp
 383 is a
 384 .I long
 385 equal to one of the values shown for
 386 .BR KDGKBMODE .
 387 .TP
 388 .B KDGKBMETA
 389 Gets meta key handling mode.
 390 .I argp
 391 points to a
 392 .I long
 393 which is
 394 set to one of these:
 395 .TS
 396 l l l.
 397 K_METABIT       0x03    set high order bit
 398 K_ESCPREFIX     0x04    escape prefix
 399 .TE
 400 .TP
 401 .B KDSKBMETA
 402 Sets meta key handling mode.
 403 .I argp
 404 is a
 405 .I long
 406 equal to one of the values shown above for
 407 .BR KDGKBMETA .
 408 .TP
 409 .B KDGKBENT
 410 Gets one entry in key translation table (keycode to action code).
 411 .I argp
 412 points to a
 413 .IP
 414 .in +4n
 415 .EX
 416 struct kbentry {
 417     unsigned char  kb_table;
 418     unsigned char  kb_index;
 419     unsigned short kb_value;
 420 };
 421 .EE
 422 .in
 423 .IP
 424 with the first two members filled in:
 425 .I kb_table
 426 selects the key table (0 <=
 427 .I kb_table
 428 < MAX_NR_KEYMAPS),
 429 and
 430 .IR kb_index
 431 is the keycode (0 <=
 432 .I kb_index
 433 < NR_KEYS).
 434 .I kb_value
 435 is set to the corresponding action code,
 436 or K_HOLE if there is no such key,
 437 or K_NOSUCHMAP if
 438 .I kb_table
 439 is invalid.
 440 .TP
 441 .B KDSKBENT
 442 Sets one entry in translation table.
 443 .I argp
 444 points to a
 445 .IR "struct kbentry" .
 446 .TP
 447 .B KDGKBSENT
 448 Gets one function key string.
 449 .I argp
 450 points to a
 451 .IP
 452 .in +4n
 453 .EX
 454 struct kbsentry {
 455     unsigned char kb_func;
 456     unsigned char kb_string[512];
 457 };
 458 .EE
 459 .in
 460 .IP
 461 .I kb_string
 462 is set to the (null-terminated) string corresponding to
 463 the
 464 .IR kb_func th
 465 function key action code.
 466 .TP
 467 .B KDSKBSENT
 468 Sets one function key string entry.
 469 .I argp
 470 points to a
 471 .IR "struct kbsentry" .
 472 .TP
 473 .B KDGKBDIACR
 474 Read kernel accent table.
 475 .I argp
 476 points to a
 477 .IP
 478 .in +4n
 479 .EX
 480 struct kbdiacrs {
 481     unsigned int   kb_cnt;
 482     struct kbdiacr kbdiacr[256];
 483 };
 484 .EE
 485 .in
 486 .IP
 487 where
 488 .I kb_cnt
 489 is the number of entries in the array, each of which
 490 is a
 491 .IP
 492 .in +4n
 493 .EX
 494 struct kbdiacr {
 495     unsigned char diacr;
 496     unsigned char base;
 497     unsigned char result;
 498 };
 499 .EE
 500 .in
 501 .TP
 502 .B KDGETKEYCODE
 503 Read kernel keycode table entry (scan code to keycode).
 504 .I argp
 505 points to a
 506 .IP
 507 .in +4n
 508 .EX
 509 struct kbkeycode {
 510     unsigned int scancode;
 511     unsigned int keycode;
 512 };
 513 .EE
 514 .in
 515 .IP
 516 .I keycode
 517 is set to correspond to the given
 518 .IR scancode .
 519 (89 <=
 520 .I scancode
 521 <= 255 only.
 522 For 1 <=
 523 .I scancode
 524 <= 88,
 525 .IR keycode == scancode .)
 526 (Since Linux 1.1.63.)
 527 .TP
 528 .B KDSETKEYCODE
 529 Write kernel keycode table entry.
 530 .I argp
 531 points to a
 532 .IR "struct kbkeycode" .
 533 (Since Linux 1.1.63.)
 534 .TP
 535 .B KDSIGACCEPT
 536 The calling process indicates its willingness to accept the signal
 537 .I argp
 538 when it is generated by pressing an appropriate key combination.
 539 (1 <=
 540 .I argp
 541 <= NSIG).
 542 (See
 543 .IR spawn_console ()
 544 in
 545 .IR linux/drivers/char/keyboard.c .)
 546 .TP
 547 .B VT_OPENQRY
 548 Returns the first available (non-opened) console.
 549 .I argp
 550 points to an
 551 .I int
 552 which is set to the
 553 number of the vt (1 <=
 554 .I *argp
 555 <= MAX_NR_CONSOLES).
 556 .TP
 557 .B VT_GETMODE
 558 Get mode of active vt.
 559 .I argp
 560 points to a
 561 .IP
 562 .in +4n
 563 .EX
 564 struct vt_mode {
 565     char  mode;    /* vt mode */
 566     char  waitv;   /* if set, hang on writes if not active */
 567     short relsig;  /* signal to raise on release req */
 568     short acqsig;  /* signal to raise on acquisition */
 569     short frsig;   /* unused (set to 0) */
 570 };
 571 .EE
 572 .in
 573 .IP
 574 which is set to the mode of the active vt.
 575 .I mode
 576 is set to one of these values:
 577 .TS
 578 l l.
 579 VT_AUTO auto vt switching
 580 VT_PROCESS      process controls switching
 581 VT_ACKACQ       acknowledge switch
 582 .TE
 583 .TP
 584 .B VT_SETMODE
 585 Set mode of active vt.
 586 .I argp
 587 points to a
 588 .IR "struct vt_mode" .
 589 .TP
 590 .B VT_GETSTATE
 591 Get global vt state info.
 592 .I argp
 593 points to a
 594 .IP
 595 .in +4n
 596 .EX
 597 struct vt_stat {
 598     unsigned short v_active;  /* active vt */
 599     unsigned short v_signal;  /* signal to send */
 600     unsigned short v_state;   /* vt bit mask */
 601 };
 602 .EE
 603 .in
 604 .IP
 605 For each vt in use, the corresponding bit in the
 606 .I v_state
 607 member is set.
 608 (Kernels 1.0 through 1.1.92.)
 609 .TP
 610 .B VT_RELDISP
 611 Release a display.
 612 .TP
 613 .B VT_ACTIVATE
 614 Switch to vt
 615 .IR argp
 616 (1 <=
 617 .I argp
 618 <= MAX_NR_CONSOLES).
 619 .TP
 620 .B VT_WAITACTIVE
 621 Wait until vt
 622 .I argp
 623 has been activated.
 624 .TP
 625 .B VT_DISALLOCATE
 626 Deallocate the memory associated with vt
 627 .IR argp .
 628 (Since Linux 1.1.54.)
 629 .TP
 630 .B VT_RESIZE
 631 Set the kernel's idea of screensize.
 632 .I argp
 633 points to a
 634 .IP
 635 .in +4n
 636 .EX
 637 struct vt_sizes {
 638     unsigned short v_rows;       /* # rows */
 639     unsigned short v_cols;       /* # columns */
 640     unsigned short v_scrollsize; /* no longer used */
 641 };
 642 .EE
 643 .in
 644 .IP
 645 Note that this does not change the videomode.
 646 See
 647 .BR resizecons (8).
 648 (Since Linux 1.1.54.)
 649 .TP
 650 .B VT_RESIZEX
 651 Set the kernel's idea of various screen parameters.
 652 .I argp
 653 points to a
 654 .IP
 655 .in +4n
 656 .EX
 657 struct vt_consize {
 658     unsigned short v_rows;  /* number of rows */
 659     unsigned short v_cols;  /* number of columns */
 660     unsigned short v_vlin;  /* number of pixel rows
 661                                on screen */
 662     unsigned short v_clin;  /* number of pixel rows
 663                                per character */
 664     unsigned short v_vcol;  /* number of pixel columns
 665                                on screen */
 666     unsigned short v_ccol;  /* number of pixel columns
 667                                per character */
 668 };
 669 .EE
 670 .in
 671 .IP
 672 Any parameter may be set to zero, indicating "no change", but if
 673 multiple parameters are set, they must be self-consistent.
 674 Note that this does not change the videomode.
 675 See
 676 .BR resizecons (8).
 677 (Since Linux 1.3.3.)
 678 .PP
 679 The action of the following ioctls depends on the first byte in the struct
 680 pointed to by
 681 .IR argp ,
 682 referred to here as the
 683 .IR subcode .
 684 These are legal only for the superuser or the owner of the current terminal.
 685 .TP
 686 .B "TIOCLINUX, subcode=0"
 687 Dump the screen.
 688 Disappeared in Linux 1.1.92.  (With kernel 1.1.92 or later, read from
 689 .I /dev/vcsN
 690 or
 691 .I /dev/vcsaN
 692 instead.)
 693 .TP
 694 .B "TIOCLINUX, subcode=1"
 695 Get task information.
 696 Disappeared in Linux 1.1.92.
 697 .TP
 698 .B "TIOCLINUX, subcode=2"
 699 Set selection.
 700 .I argp
 701 points to a
 702 .IP
 703 .in +4n
 704 .EX
 705 struct {
 706     char  subcode;
 707     short xs, ys, xe, ye;
 708     short sel_mode;
 709 };
 710 .EE
 711 .in
 712 .IP
 713 .I xs
 714 and
 715 .I ys
 716 are the starting column and row.
 717 .I xe
 718 and
 719 .I ye
 720 are the ending
 721 column and row.
 722 (Upper left corner is row=column=1.)
 723 .I sel_mode
 724 is 0 for character-by-character selection,
 725 1 for word-by-word selection,
 726 or 2 for line-by-line selection.
 727 The indicated screen characters are highlighted and saved
 728 in the static array sel_buffer in
 729 .IR devices/char/console.c .
 730 .TP
 731 .B "TIOCLINUX, subcode=3"
 732 Paste selection.
 733 The characters in the selection buffer are
 734 written to
 735 .IR fd .
 736 .TP
 737 .B "TIOCLINUX, subcode=4"
 738 Unblank the screen.
 739 .TP
 740 .B "TIOCLINUX, subcode=5"
 741 Sets contents of a 256-bit look up table defining characters in a "word",
 742 for word-by-word selection.
 743 (Since Linux 1.1.32.)
 744 .TP
 745 .B "TIOCLINUX, subcode=6"
 746 .I argp
 747 points to a char which is set to the value of the kernel
 748 variable
 749 .IR shift_state .
 750 (Since Linux 1.1.32.)
 751 .TP
 752 .B "TIOCLINUX, subcode=7"
 753 .I argp
 754 points to a char which is set to the value of the kernel
 755 variable
 756 .IR report_mouse .
 757 (Since Linux 1.1.33.)
 758 .TP
 759 .B "TIOCLINUX, subcode=8"
 760 Dump screen width and height, cursor position, and all the
 761 character-attribute pairs.
 762 (Kernels 1.1.67 through 1.1.91 only.
 763 With kernel 1.1.92 or later, read from
 764 .I /dev/vcsa*
 765 instead.)
 766 .TP
 767 .B "TIOCLINUX, subcode=9"
 768 Restore screen width and height, cursor position, and all the
 769 character-attribute pairs.
 770 (Kernels 1.1.67 through 1.1.91 only.
 771 With kernel 1.1.92 or later, write to
 772 .I /dev/vcsa*
 773 instead.)
 774 .TP
 775 .B "TIOCLINUX, subcode=10"
 776 Handles the Power Saving
 777 feature of the new generation of monitors.
 778 VESA screen blanking mode is set to
 779 .IR argp[1] ,
 780 which governs what
 781 screen blanking does:
 782 .RS
 783 .IP 0: 3
 784 Screen blanking is disabled.
 785 .IP 1:
 786 The current video adapter
 787 register settings are saved, then the controller is programmed to turn off
 788 the vertical synchronization pulses.
 789 This puts the monitor into "standby" mode.
 790 If your monitor has an Off_Mode timer, then
 791 it will eventually power down by itself.
 792 .IP 2:
 793 The current settings are saved, then both the vertical and horizontal
 794 synchronization pulses are turned off.
 795 This puts the monitor into "off" mode.
 796 If your monitor has no Off_Mode timer,
 797 or if you want your monitor to power down immediately when the
 798 blank_timer times out, then you choose this option.
 799 .RI ( Caution:
 800 Powering down frequently will damage the monitor.)
 801 (Since Linux 1.1.76.)
 802 .RE
 803 .SH RETURN VALUE
 804 On success, 0 is returned.
 805 On error, \-1 is returned, and
 806 .I errno
 807 is set.
 808 .SH ERRORS
 809 .I errno
 810 may take on these values:
 811 .TP
 812 .B EBADF
 813 The file descriptor is invalid.
 814 .TP
 815 .B EINVAL
 816 The file descriptor or
 817 .I argp
 818 is invalid.
 819 .TP
 820 .B ENOTTY
 821 The file descriptor is not associated with a character special device,
 822 or the specified request does not apply to it.
 823 .TP
 824 .B EPERM
 825 Insufficient permission.
 826 .SH NOTES
 827 .BR Warning :
 828 Do not regard this man page as documentation of the Linux console ioctls.
 829 This is provided for the curious only, as an alternative to reading the
 830 source.
 831 Ioctl's are undocumented Linux internals, liable to be changed
 832 without warning.
 833 (And indeed, this page more or less describes the
 834 situation as of kernel version 1.1.94;
 835 there are many minor and not-so-minor
 836 differences with earlier versions.)
 837 .PP
 838 Very often, ioctls are introduced for communication between the
 839 kernel and one particular well-known program (fdisk, hdparm, setserial,
 840 tunelp, loadkeys, selection, setfont, etc.), and their behavior will be
 841 changed when required by this particular program.
 842 .PP
 843 Programs using these ioctls will not be portable to other versions
 844 of UNIX, will not work on older versions of Linux, and will not work
 845 on future versions of Linux.
 846 .PP
 847 Use POSIX functions.
 848 .SH SEE ALSO
 849 .BR dumpkeys (1),
 850 .BR kbd_mode (1),
 851 .BR loadkeys (1),
 852 .BR mknod (1),
 853 .BR setleds (1),
 854 .BR setmetamode (1),
 855 .BR execve (2),
 856 .BR fcntl (2),
 857 .BR ioctl_tty (2),
 858 .BR ioperm (2),
 859 .BR termios (3),
 860 .BR console_codes (4),
 861 .BR mt (4),
 862 .BR sd (4),
 863 .BR tty (4),
 864 .BR ttyS (4),
 865 .BR vcs (4),
 866 .BR vcsa (4),
 867 .BR charsets (7),
 868 .BR mapscrn (8),
 869 .BR resizecons (8),
 870 .BR setfont (8)
 871 .PP
 872 .IR /usr/include/linux/kd.h ,
 873 .I /usr/include/linux/vt.h