1.\" -*- nroff -*- 2.\" 3.\" Copyright (c) 1998 Doug Rabson 4.\" 5.\" All rights reserved. 6.\" 7.\" This program is free software. 8.\" 9.\" Redistribution and use in source and binary forms, with or without 10.\" modification, are permitted provided that the following conditions 11.\" are met: 12.\" 1. Redistributions of source code must retain the above copyright 13.\" notice, this list of conditions and the following disclaimer. 14.\" 2. Redistributions in binary form must reproduce the above copyright 15.\" notice, this list of conditions and the following disclaimer in the 16.\" documentation and/or other materials provided with the distribution. 17.\" 18.\" THIS SOFTWARE IS PROVIDED BY THE DEVELOPERS ``AS IS'' AND ANY EXPRESS OR 19.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21.\" IN NO EVENT SHALL THE DEVELOPERS BE LIABLE FOR ANY DIRECT, INDIRECT, 22.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28.\" 29.\" $FreeBSD$ 30.\" 31.Dd January 15, 2017 32.Dt DEVICE 9 33.Os 34.Sh NAME 35.Nm device 36.Nd an abstract representation of a device 37.Sh SYNOPSIS 38.Vt typedef struct _device *device_t ; 39.Sh DESCRIPTION 40The device object represents a piece of hardware attached to the 41system such as an expansion card, the bus which that card is plugged 42into, disk drives attached to the expansion card etc. 43The system defines one device, 44.Va root_bus 45and all other devices are created dynamically during 46autoconfiguration. 47Normally devices representing top-level buses in 48the system (ISA, PCI etc.) will be attached directly to 49.Va root_bus 50and other devices will be added as children of their relevant bus. 51.Pp 52The devices in a system form a tree. 53All devices except 54.Va root_bus 55have a parent (see 56.Xr device_get_parent 9 ) . 57In addition, any device can have children attached to it (see 58.Xr device_add_child 9 , 59.Xr device_add_child_ordered 9 , 60.Xr device_find_child 9 , 61.Xr device_get_children 9 , 62and 63.Xr device_delete_child 9 ) . 64.Pp 65A device which has been successfully probed and attached to the 66system will also have a driver (see 67.Xr device_get_driver 9 68and 69.Xr driver 9 ) 70and a devclass (see 71.Xr device_get_devclass 9 72and 73.Xr devclass 9 ) . 74Various other attributes of the device include a unit number (see 75.Xr device_get_unit 9 ) , 76verbose description (normally supplied by the driver, see 77.Xr device_set_desc 9 78and 79.Xr device_get_desc 9 ) , 80a set of bus-specific variables (see 81.Xr device_get_ivars 9 ) 82and a set of driver-specific variables (see 83.Xr device_get_softc 9 ) . 84.Pp 85Devices can be in one of several states: 86.Bl -tag -width DS_NOTPRESENT 87.It Dv DS_NOTPRESENT 88the device has not been probed for existence or the probe failed 89.It Dv DS_ALIVE 90the device probe succeeded but not yet attached 91.It Dv DS_ATTACHED 92the device has been successfully attached 93.It Dv DS_BUSY 94the device is currently open 95.El 96.Pp 97The current state of the device can be determined by calling 98.Xr device_get_state 9 . 99.Sh SEE ALSO 100.Xr devclass 9 , 101.Xr driver 9 102.Sh AUTHORS 103This manual page was written by 104.An Doug Rabson . 105