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