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vkbd(4) [freebsd man page]

VKBD(4) 						   BSD Kernel Interfaces Manual 						   VKBD(4)

vkbd -- the virtual AT keyboard interface SYNOPSIS
device vkbd DESCRIPTION
The vkbd interface is a software loopback mechanism that can be loosely described as the virtual AT keyboard analog of the pty(4), that is, vkbd does for virtual AT keyboards what the pty(4) driver does for terminals. The vkbd driver, like the pty(4) driver, provides two interfaces: a keyboard interface like the usual facility it is simulating (a virtual AT keyboard in the case of vkbd, or a terminal for pty(4)), and a character-special device ``control'' interface. The virtual AT keyboards are named vkbd0, vkbd1, etc., one for each control device that has been opened. The vkbd interface permits opens on the special control device /dev/vkbdctl. When this device is opened, vkbd will return a handle for the lowest unused vkbdctl device (use devname(3) to determine which). Each virtual AT keyboard supports the usual keyboard interface ioctl(2)s, and thus can be used with kbdcontrol(1) like any other keyboard. The control device supports exactly the same ioctl(2)s as the virtual AT keyboard device. Writing AT scan codes to the control device gener- ates an input on the virtual AT keyboard, as if the (non-existent) hardware had just received it. The virtual AT keyboard control device, normally /dev/vkbdctl<N>, is exclusive-open (it cannot be opened if it is already open) and is restricted to the super-user. A read(2) call will return the virtual AT keyboard status structure (defined in <dev/vkbd/vkbd_var.h>) if one is available; if not, it will either block until one is or return EWOULDBLOCK, depending on whether non-blocking I/O has been enabled. A write(2) call passes AT scan codes to be ``received'' from the virtual AT keyboard. Each AT scan code must be passed as unsigned int. Although AT scan codes must be passes as unsigned ints, the size of the buffer passed to write(2) still should be in bytes, i.e., static unsigned int codes[] = { /* Make Break */ 0x1e, 0x9e }; int main(void) { int fd, len; fd = open("/dev/vkbdctl0", O_RDWR); if (fd < 0) err(1, "open"); /* Note sizeof(codes) - not 2! */ len = write(fd, codes, sizeof(codes)); if (len < 0) err(1, "write"); close(fd); return (0); } Write will block if there is not enough space in the input queue. The control device also supports select(2) for read and write. On the last close of the control device, the virtual AT keyboard is removed. All queued scan codes are thrown away. SEE ALSO
kbdcontrol(1), atkbdc(4), psm(4), syscons(4), vt(4) HISTORY
The vkbd module was implemented in FreeBSD 6.0. AUTHORS
Maksim Yevmenkin <> CAVEATS
The vkbd interface is a software loopback mechanism, and, thus ddb(4) will not work with it. Current implementation of the syscons(4) driver can accept input from only one keyboard, even if it is virtual. Thus it is not possible to have both wired and virtual keyboard to be active at the same time. It is, however, in principal possible to obtain AT scan codes from the different sources and write them into the same vir- tual keyboard. The virtual keyboard state synchronization is the user's responsibility. BSD
August 12, 2004 BSD

Check Out this Related Man Page

CONSPY(1)							      conspy								 CONSPY(1)

conspy - virtual console spy tool SYNOPSIS
conspy [ options ] [ console ] DESCRIPTION
Conspy allows the user to take control of a Linux virtual console. The user can see what is displayed on the console and their keystrokes are sent to it. To exit from conspy press the escape key three times in quick succession. COMMAND LINE
-V, --version Print the program's version and exit. -v, --viewonly Don't send keystrokes to the virtual console. console If supplied, console must be a number in the range 1 .. 63, corresponding to the virtual console device /dev/tty1 .. /dev/tty63. If not supplied the currently active virtual console is opened and tracked. LIMITATIONS
Conspy will not pass keystrokes to a virtual console whose keyboard is configured to send scan codes. X configures its keyboard like this. If the terminal does not have at least 64 colours no colour will be displayed. Conspy ignores the mouse. Conspy may display some non- ASCII characters incorrectly. Conspy does not handle displays larger than 16000 characters (eg 200 rows x 80 columns). Conspy depends on terminfo and curses working correctly for your terminal, and sometimes they don't. Konsole is/was one example of where they don't. Typing control-L will redraw the screen, which usually fixes the mess created. It also sends a control-L to the virtual con- sole, of course. FILES
/dev/ttyX, /dev/vc/X The characters typed are sent to this device. The latter is for devfs. It is only used if the former does not exist. /dev/vcsaX, /dev/vcc/aX The display of the virtual console is read from here. The latter is for devfs. It is only used if the former does not exist. AUTHOR
Russell Stuart, <>. Version 1.8 Apr 2011 CONSPY(1)
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