155 lines
3.5 KiB
Groff
155 lines
3.5 KiB
Groff
.\" $Id: vkbd.4,v 1.4 2004/11/16 16:49:39 max Exp $
|
|
.\" $FreeBSD$
|
|
.\"
|
|
.Dd August 12, 2004
|
|
.Os
|
|
.Dt VKBD 4
|
|
.Sh NAME
|
|
.Nm vkbd
|
|
.Nd the virtual AT keyboard interface
|
|
.Sh SYNOPSIS
|
|
.Cd device vkbd
|
|
.Sh DESCRIPTION
|
|
The
|
|
.Nm
|
|
interface is a software loopback mechanism that can be loosely
|
|
described as the virtual AT keyboard analog of the
|
|
.Xr pty 4 ,
|
|
that is,
|
|
.Nm
|
|
does for virtual AT keyboards what the
|
|
.Nm pty
|
|
driver does for terminals.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
driver, like the
|
|
.Nm pty
|
|
driver, provides two interfaces: a keyboard interface like the usual
|
|
facility it is simulating (a virtual AT keyboard in the case of
|
|
.Nm ,
|
|
or a terminal for
|
|
.Nm pty ) ,
|
|
and a character-special device
|
|
.Dq control
|
|
interface.
|
|
.Pp
|
|
The virtual AT keyboards are named
|
|
.Dq Li vkbd0 ,
|
|
.Dq Li vkbd1 ,
|
|
etc., one for each control device that has been opened.
|
|
.Pp
|
|
The
|
|
.Nm
|
|
interface permits opens on the special control device
|
|
.Pa /dev/vkbdctl .
|
|
When this device is opened,
|
|
.Nm
|
|
will return a handle for the lowest unused
|
|
.Nm vkbdctl
|
|
device (use
|
|
.Xr devname 3
|
|
to determine which).
|
|
.Pp
|
|
Each virtual AT keyboad supports the usual keyboard interface
|
|
.Xr ioctl 2 Ns s ,
|
|
and thus can be used with
|
|
.Xr kbdcontrol 1
|
|
like any other keyboard.
|
|
The control device supports exactly the same
|
|
.Xr ioctl 2 Ns s
|
|
as the virtual AT keyboad device.
|
|
Writing AT scan codes to the control device generates an input on
|
|
the virtual AT keyboard, as if the
|
|
(non-existent)
|
|
hardware had just received it.
|
|
.Pp
|
|
The virtual AT kerboard control device, normally
|
|
.Pa /dev/vkbdctl Ns Sy N ,
|
|
is exclusive-open
|
|
(it cannot be opened if it is already open)
|
|
and is restricted to the super-user.
|
|
A
|
|
.Fn read
|
|
call will return the virtual AT keyboard status structure
|
|
(defined in
|
|
.In dev/vkbd/vkbd_var.h )
|
|
if one is available;
|
|
if not, it will either block until one is or return
|
|
.Er EWOULDBLOCK ,
|
|
depending on whether non-blocking I/O has been enabled.
|
|
.Pp
|
|
A
|
|
.Xr write 2
|
|
call passes AT scan codes to be
|
|
.Dq received
|
|
from the virtual AT keyboard.
|
|
Each AT scan code must be passed as
|
|
.Vt unsigned int .
|
|
Although AT scan codes must be passes as
|
|
.Vt unsigned int Ns s ,
|
|
the size of the buffer passed to
|
|
.Xr write 2
|
|
still should be in bytes, i.e.
|
|
.Bd -literal -offset indent
|
|
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);
|
|
}
|
|
.Ed
|
|
.Pp
|
|
Write will block if there is not enough space in the input queue.
|
|
.Pp
|
|
The control device also supports
|
|
.Xr select 2
|
|
for read and write.
|
|
.Pp
|
|
On the last close of the control device, the virtual AT keyboard is removed.
|
|
All queued scan codes are thrown away.
|
|
.Sh SEE ALSO
|
|
.Xr kbdcontrol 1 ,
|
|
.Xr atkbdc 4 ,
|
|
.Xr pcvt 4 ,
|
|
.Xr psm 4 ,
|
|
.Xr syscons 4
|
|
.Sh CAVEAT
|
|
The
|
|
.Nm
|
|
interface is a software loopback mechanism, and, thus
|
|
.Xr ddb 4
|
|
will not work with it.
|
|
Current implementation of the
|
|
.Xr syscons 4
|
|
driver can accept input from only one keyboard, even if it is virtual.
|
|
Thus is it 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 virtual keyboard.
|
|
The virtual keyboard state synchronization is the user's responsibility.
|
|
.Sh HISTORY
|
|
The
|
|
.Nm
|
|
module was implemented in
|
|
.Fx 6.0 .
|
|
.Sh AUTHORS
|
|
.An Maksim Yevmenkin Aq m_evmenkin@yahoo.com
|