device(9)

NAME

device - an abstract representation of a device

SYNOPSIS

typedef struct device *device_t;

DESCRIPTION

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 de

fines one
device, root_bus and all other devices are created dynami

cally during
autoconfiguration. Normally devices representing top-level

busses in the
system (ISA, PCI etc.) will be attached directly to root_bus

and other
devices will be added as children of their relevant bus.

The devices in a system form a tree. All devices except

root_bus have a
parent (see device_get_parent(9)). In addition, any device

can have
children attached to it (see device_add_child(9),
device_add_child_ordered(9), device_find_child(9),
device_get_children(9), and device_delete_child(9)).

A device which has been successfully probed and attached to

the system
will also have a driver (see device_get_driver(9) and driv

er(9)) and a
devclass (see device_get_devclass(9) and devclass(9)). Var

ious other
attributes of the device include a unit number (see de

vice_get_unit(9)),
verbose description (normally supplied by the driver, see
device_set_desc(9) and device_get_desc(9)), a set of bus

specific variables (see device_get_ivars(9)) and a set of driver-specific

variables
(see device_get_softc(9)).

Devices can be in one of several states:

DS_NOTPRESENT the device has not been probed for existence

or the probe

failed

DS_ALIVE the device probe succeeded but not yet at

tached

DS_ATTACHED the device has been successfully attached

DS_BUSY the device is currently open

The current state of the device can be determined by calling
device_get_state(9).

SEE ALSO

devclass(9), driver(9)

AUTHORS

This manual page was written by Doug Rabson.

BSD June 16, 1998

BSD