.\"	$OpenBSD: bio.4,v 1.7 2004/08/25 23:58:14 jmc Exp $
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.\" Copyright (c) 2002 Niklas Hallqvist
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.Dd June 8, 2002
.Dt BIO 4
.Os
.Sh NAME
.Nm bio
.Nd ioctl tunnel pseudo-device
.Sh SYNOPSIS
.Cd "pseudo-device bio" Op Ar count
.Sh DESCRIPTION
The
.Nm
driver provides userland applications ioctl access to devices otherwise not
found as
.Pa /dev
nodes.
The
.Pa /dev/bio
device node operates by delegating
.Xr ioctl 2
calls to a requested device driver.
Only drivers which have registered with the
.Nm
device can be accessed via this interface.
.Pp
If
.Ar count
is given in the specification, and is greater than 0, a maximum of one
.Nm bio
device is created.
.Pp
The following
.Xr ioctl 2
calls apply to the
.Nm bio
device:
.Bl -tag -width BIOCLOCATE
.It Dv BIOCLOCATE
Locate a named device and give back a cookie to the application
for subsequent ioctl calls.
The cookie is used to tunnel further ioctls to the right device.
.El
.Sh FILES
.Bl -tag -width /dev/bio -compact
.It Pa /dev/bio
ioctl tunnel device
.El
.Sh SEE ALSO
.Xr ioctl 2 ,
.Xr gdt 4
.Sh HISTORY
The
.Nm
driver first appeared in
.Ox 3.2 .