xref: /freebsd/share/man/man9/device.9 (revision 6990ffd8a95caaba6858ad44ff1b3157d1efba8f)
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29.\" $FreeBSD$
30.\"
31.Dd June 16, 1998
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.Dv root_bus
45and all other devices are created dynamically during
46autoconfiguration.  Normally devices representing toplevel busses in
47the system (ISA, PCI etc.) will be attached directly to
48.Dv root_bus
49and other devices will be added as children of their relevant bus.
50.Pp
51The devices in a system form a tree.
52All devices except
53.Dv root_bus
54have a parent (see
55.Xr device_get_parent 9 ) .
56In addition, any device can have children attached to it (see
57.Xr device_add_child 9 ,
58.Xr device_add_child_ordered 9 ,
59.Xr device_find_child 9 ,
60.Xr device_get_children 9 ,
61and
62.Xr device_delete_child 9 ) .
63.Pp
64A device which has been successfully probed and attached to the
65system will also have a driver (see
66.Xr device_get_driver 9
67and
68.Xr driver 9 )
69and a devclass (see
70.Xr device_get_devclass 9
71and
72.Xr devclass 9 ) .
73Various other attributes of the device include a unit number (see
74.Xr device_get_unit 9 ) ,
75verbose description (normally supplied by the driver, see
76.Xr device_set_desc 9
77and
78.Xr device_get_desc 9 ) ,
79a set of bus-specific variables (see
80.Xr device_get_ivars 9 )
81and a set of driver-specific variables (see
82.Xr device_get_softc 9 ) .
83.Pp
84Devices can be in one of several states:
85.Bl -tag -width DS_NOTPRESENT
86.It Ar DS_NOTPRESENT
87the device has not been probed for existence or the probe failed
88.It Ar DS_ALIVE
89the device probe succeeded but not yet attached
90.It Ar DS_ATTACHED
91the device has been successfully attached
92.It Ar DS_BUSY
93the device is currently open
94.El
95.Pp
96The current state of the device can be determined by calling
97.Xr device_get_state 9 .
98.Sh SEE ALSO
99.Xr devclass 9 ,
100.Xr driver 9
101.Sh AUTHORS
102This man page was written by
103.An Doug Rabson .
104