CONSOLE_IOCTLS(4)

NAME
console ioctl's- ioctl's for console terminal and virtual consoles

DESCRIPTION
WARNING: If you use the following information you are going to burn yourself.

WARNING: ioctl's are undocumented Linux internals, liable to be changed without warning. Use POSIX functions where available.

The following Linux-peculiar ioctl() requests are supported. Each requires a third argument, assumed here to be argp.

KDGETLED
    Get state of LEDs. argp points to a long int. The lower three bits of *argp are set to the state of the LEDs, as follows:

        LED_CAP 0x04 caps lock led
        LEC_NUM 0x02 num lock led
        LED_SCR 0x01 scroll lock led

KDSETLED
    Set the LEDs. The LEDs are set to correspond to the lower three bits of argp. However, if a higher order bit is set, the LEDs revert to normal: displaying the state of the keyboard functions of caps lock, num lock, and scroll lock.

    Before 1.1.54, the leds just reflected the state of the corresponding keyboard flags, and KDGETLED/KDSETLED would also change the keyboard flags. Since 1.1.54 the leds can be made to display arbitrary information, but by default they display the keyboard flags. The following two ioctl's are used to access the keyboard flags.

KDGKBLED
    Get keyboard flags CapsLock, NumLock, ScrollLock (not lights). argp points to a char which is set to the flag state. The low order three bits (mask 0x7) get the current flag state, and the low order bits of the next nibble (mask 0x70) get the default flag state. (Since 1.1.54.)

KDSKBLED
    Set keyboard flags CapsLock, NumLock, ScrollLock (not lights). argp has the desired flag state. The low order three bits (mask 0x7) have the flag state, and the low order bits of the next nibble (mask 0x70) have the default flag state. (Since 1.1.54.)

KDGKBTYPE
    Get keyboard type. This returns the value KB_101, defined as 0x02.

KDADDIO
    Add I/O port as valid. Equivalent to ioperm(arg,1,1).

KDDELIO
    Delete I/O port as valid. Equivalent to ioperm(arg,1,0).

KDENABIO
    Enable I/O to video board. Equivalent to ioperm(0x3b4, 0x3df-0x3b4+1, 1).

KDDISABIO
    Disable I/O to video board. Equivalent to ioperm(0x3b4, 0x3df-0x3b4+1, 0).

KDSETMODE
    Set text/graphics mode. argp is one of these:

        KD_TEXT 0x00
        KD_GRAPHICS 0x01

KDGETMODE
    Get text/graphics mode. argp points to a long which is set to one of the above values.

KDMKTONE
    Generate tone of specified length. The lower 16 bits of argp specify the period in clock cycles, and the upper 16 bits give the duration in msec. If the duration is zero, the sound is turned off. Control returns immediately. For example, argp = (125<<16) + 0x637 would specify the beep normally associated with a ctrl-G.

KIOCSOUND
    Start or stop sound generation. The lower 16 bits of argp specify the period in clock cycles (that is, argp = 1193180/frequency). argp = 0 turns sound off. In either case, control returns immediately.

GIO_FONT
    Gets screen font in expanded form. argp points to an 8192 byte array.

PIO_FONT
    Sets screen font. Load font into the EGA/VGA character generator. argp points to a 8192 byte map, with 32 bytes per character. Only first N of them are used for an 8xN font (0 < N <= 32).

GIO_SCRNMAP
    Get screen mapping from kernel. argp points to an area of size E_TABSZ.

PIO_SCRNMAP
    Loads the "user definable" (fourth) table in the kernel which maps bytes into console screen symbols. argp points to an area of size E_TABSZ.

GIO_UNIMAP
    Get unicode-to-font mapping from kernel. argp points to a

    struct unimapdesc {
            u_short entry_ct;
            struct unipair *entries;
    };

    where entries points to an array of

    struct unipair {
            u_short unicode;
            u_short fontpos;
    };

    (Since 1.1.92.)

PIO_UNIMAP
    Put unicode-to-font mapping in kernel. argp points to a struct unimapdesc. (Since 1.1.92)

PIO_UNIMAPCLR
    Clear table, possibly advise hash algorithm. argp points to a

    struct unimapinit {
            u_short advised_hashsize;  /* 0 if no opinion */
            u_short advised_hashstep;  /* 0 if no opinion */
            u_short advised_hashlevel; /* 0 if no opinion */
    };

    (Since 1.1.92.)

KDGKBMODE
    Gets current keyboard mode. argp points to a long which is set to one of these:

        K_RAW 0x00
        K_XLATE 0x01
        K_MEDIUMRAW 0x02
        K_UNICODE 0x03

KDSKBMODE
    Sets current keyboard mode. argp is a long equal to one of the above values.

KDGKBMETA
    Gets meta key handling mode. argp points to a long which is set to one of these:

        K_METABIT 0x03 set high order bit
        K_ESCPREFIX 0x04 escape prefix

KDSKBMETA
    Sets meta key handling mode. argp is a long equal to one of the above values.

KDGKBENT
    Gets one entry in key translation table (keycode to action code). argp points to a

    struct kbentry {
        u_char kb_table;
        u_char kb_index;
        u_short kb_value;
    };

    with the first two members filled in: kb_table selects the key table (0 <= kb_table < MAX_NR_KEYMAPS), and kb_index is the keycode (0 <= kb_index < NR_KEYS). kb_value is set to the corresponding action code, or K_HOLE if there is no such key, or K_NOSUCHMAP if kb_table is invalid.

KDSKBENT
    Sets one entry in translation table. argp points to a struct kbentry.

KDGKBSENT
    Gets one function key string. argp points to a

    struct kbsentry {
        u_char kb_func;
        u_char kb_string[512];
    };

    kb_string is set to the (NULL terminated) string corresponding to the kb_functh function key action code.

KDSKBSENT
    Sets one function key string entry. argp points to a struct kbsentry.

KDGKBDIACR
    Read kernel accent table. argp points to a

    struct kbdiacrs {
        unsigned int kb_cnt;
        struct kbdiacr kbdiacr[256];
    };

    where kb_cnt is the number of entries in the array, each of which is a

    struct kbdiacr { u_char diacr, base, result; };

KDGETKEYCODE
    Read kernel keycode table entry (scan code to keycode). argp points to a

    struct kbkeycode { unsigned int scancode, keycode; };

    keycode is set to correspond to the given scancode. (89 <= scancode <= 255 only. For 1 <= scancode <= 88, keycode==scancode.) (Since 1.1.63.)

KDSETKEYCODE
    Write kernel keycode table entry. argp points to struct kbkeycode. (Since 1.1.63.)

KDSIGACCEPT
    The calling process indicates its willingness to accept the signal argp when it is generated by pressing an appropriate key combination. (1 <= argp <= NSIG). (See spawn_console() in linux/drivers/char/keyboard.c.)

VT_OPENQRY
    Returns the first available (non-opened) console. argp points to an int which is set to the number of the vt (1 <= *argp <= MAX_NR_CONSOLES).

VT_GETMODE
    Get mode of active vt. argp points to a

    struct vt_mode {
        char mode;     /* vt mode */
        char waitv;    /* if set, hang on writes if not active */
        short relsig;  /* signal to raise on release req */
        short acqsig;  /* signal to raise on acquisition */
        short frsig;   /* unused (set to 0) */
    };

    mode is set to one of these values:

        VT_AUTO auto vt switching
        VT_PROCESS process controls switching
        VT_ACKACQ acknowledge switch

VT_SETMODE
    Set mode of active vt. argp points to a struct vt_mode.

VT_GETSTATE
    Get global vt state info. argp points to a

    struct vt_stat {
        ushort v_active;  /* active vt */
        ushort v_signal;  /* signal to send */
        ushort v_state;   /* vt bitmask */
    };

    For each vt in use, the corresponding bit in the v_state member is set. (Kernels 1.0 through 1.1.92.)

VT_RELDISP
    Release a display.

VT_ACTIVATE
    Switch to vt argp (1 <= argp <= MAX_NR_CONSOLES).

VT_WAITACTIVE
    Wait until vt argp has been activated.

VT_DISALLOCATE
    Deallocate the memory associated with vt argp. (Since 1.1.54.)

VT_RESIZE
    Set kernel's idea of screensize. argp points to a

    struct vt_sizes {
        ushort v_rows;       /* # rows */
        ushort v_cols;       /* # columns */
        ushort v_scrollsize; /* no longer used */
    };

    (Since 1.1.54.) Note that this does not change the videomode. See resizecons(8).

The action of the following ioctls depends on the first byte in the struct pointed to by argp, referred to here as the subcode. These are legal only for the superuser or the owner of the current tty.

TIOCLINUX, subcode=0
    Dump the screen. Disappeared in 1.1.92. (With kernel 1.1.92 or later, read from /dev/vcsN or /dev/vcsaN instead.)

TIOCLINUX, subcode=1
    Get task information. Disappeared in 1.1.92.

TIOCLINUX, subcode=2
    Set selection. argp points to a

       struct {char subcode;
           short xs, ys, xe, ye;
           short sel_mode;
       }

    xs and ys are the starting column and row. xe and ye are the ending column and row. (Upper left corner is row=column=1.) sel_mode is 0 for character-by-character selection, 1 for word-by-word selection, or 2 for line-by-line selection. The indicated screen characters are highlighted and saved in the static array sel_buffer in devices/char/console.c.

TIOCLINUX, subcode=3
    Paste selection. The characters in the selection buffer are written to fd.

TIOCLINUX, subcode=4
    Unblank the screen.

TIOCLINUX, subcode=5
    Sets contents of a 256-bit look up table defining characters in a "word", for word-by-word selection. (Since 1.1.32.)

TIOCLINUX, subcode=6
    argp points to a char which is set to the value of the kernel variable shift_state. (Since 1.1.32.)

TIOCLINUX, subcode=7
    argp points to a char which is set to the value of the kernel variable report_mouse. (Since 1.1.33.)

TIOCLINUX, subcode=8
    Dump screen width and height, cursor position, and all the character-attribute pairs. (Kernels 1.1.67 through 1.1.91 only. With kernel 1.1.92 or later, read from /dev/vcsa* instead.)

TIOCLINUX, subcode=9
    Restore screen width and height, cursor position, and all the character-attribute pairs. (Kernels 1.1.67 through 1.1.91 only. With kernel 1.1.92 or later, write to /dev/vcsa* instead.)

TIOCLINUX, subcode=10
    Handles the Power Saving feature of the new generation of monitors. VESA screen blanking mode is set to argp, which is one of:

        0: Screen blanking is disabled.

        1: The current video adapter register settings are saved, then the controller is programmed to turn off the vertical synchronization pulses. This puts the monitor into "standby" mode. If your monitor has an Off_Mode timer, then it will eventually power down by itself.

        2: The current settings are saved, then both the vertical and horizontal synchronization pulses are turned off. This puts the monitor into "off" mode. If your monitor has no Off_Mode timer, or if you want your monitor to power down immediately when the blank_timer times out, then you choose this option. (Caution: Powering down frequently will damage the monitor.)

    (Since 1.1.76.)

RETURN VALUES
-1 for error, and errno is set.

ERRORS
errno may take on these values:

EBADF	file descriptor is invalid.
ENOTTY	file descriptor is not associated with a character
		special device, or the specified request does not
		apply to it.
EINVAL	file descriptor or argp is invalid.
EPERM	permission violation.

WARNING
Do not regard this man page as documentation of the Linux console ioctl's. This is provided for the curious only, as an alternative to reading the source. Ioctl's are undocumented Linux internals, liable to be changed without warning. (And indeed, this page more or less describes the situation as of kernel version 1.1.94; there are many minor and not-so-minor differences with earlier versions.)

Very often, ioctl's are introduced for communication between the kernel and one particular well-known program (fdisk(8), hdparm(8), setserial(8), tunelp(8), loadkeys(1), gpm(8), consolechars(8), etc.), and their behavior will be changed when required by these particular programs.

Programs using these ioctl's will not be portable to other versions of Unix, will not work on older versions of Linux, and will not work on future versions of Linux.

Use POSIX functions.

SEE ALSO
kbd_mode(1), loadkeys(1), dumpkeys(1), mknod(1), setleds(1), setmetamode(1), ioperm(2), termios(2), execve(2), fcntl(2), mt(4), sd(4), tty(4), ttys(4), vcs(4), vcsa(4), mapscrn(8), consolechars(8), resizecons(8), /usr/include/linux/kd.h, /usr/include/linux/vt.h.