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.\" -*- nroff -*-
.\"
.\" Copyright (c) 1998 Doug Rabson
.\"
.\" All rights reserved.
.\"
.\" This program is free software.
.\"
.\" Redistribution and use in source and binary forms, with or without
.\" modification, are permitted provided that the following conditions
.\" are met:
.\" 1. Redistributions of source code must retain the above copyright
.\" notice, this list of conditions and the following disclaimer.
.\" 2. Redistributions in binary form must reproduce the above copyright
.\" notice, this list of conditions and the following disclaimer in the
.\" documentation and/or other materials provided with the distribution.
.\"
.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR
.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT,
.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
.\"
.\" $Id$
.\"
.Dd June 16, 1998
.Dt device 9
.Os FreeBSD
.Sh NAME
.Nm device
.Nd an abstract representation of a device
.Sh SYNOPSYS
.Dv typedef struct device *device_t;
.Sh DESCRIPTION
.Pp
The device object represents a piece of hardware attached to the
system such as an expansion card, the bus which that card is plugged
into, disk drives attached to the expansion card etc.
The system defines one device,
.Dv root_bus
and all other devices are created dynamically during
autoconfiguration. Normally devices representing toplevel busses in
the system (ISA, PCI etc.) will be attached directly to
.Dv root_bus
and other devices will be added as children of their relavent bus.
.Pp
The devices in a system form a tree. All devices except
.Dv root_bus
have a parent (see
.Xr device_get_parent 9 ).
In addition, any device can have children attached to it (see
.Xr device_add_child 9 ,
.Xr device_add_child_after 9 ,
.Xr device_find_child 9 ,
and
.Xr device_delete_child 9 ).
.Pp
A device which has been successfully been probed and attached to the
system will also have a driver (see
.Xr device_get_driver 9
and
.Xr driver 9 )
and a devclass (see
.Xr device_get_devclass 9
and
.Xr devclass 9 ).
Various other attributes of the device include a unit number (see
.Xr device_get_unit 9 ),
verbose description (normally supplied by the driver, see
.Xr device_set_desc 9
and
.Xr device_get_desc 9 ),
a set of bus-specific variables (see
.Xr device_get_ivars 9 )
and a set of driver-specific variables (see
.Xr device_get_softc 9 ).
.Pp
Devices can be in one of several states:
.Bl -tag -width DS_NOTPRESENT
.It Ar DS_NOTPRESENT
the device has not been probed for existence or the probe failed
.It Ar DS_ALIVE
the device probe succeeded but not yet attached
.It Ar DS_ATTACHED
the device has been successfully attached
.It Ar DS_BUSY
the device is currently open
.El
.Pp
The current state of the device can be determined by calling
.Xr device_get_state 9 .
.Sh SEE ALSO
.Xr driver 9 ,
.Xr devclass 9
.Sh AUTHORS
This man page was written by
.An Doug Rabson .
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