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  defines
       one  device,  root_bus  and all other devices are created dynamically 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 driver(9)) and a devclass (see device_get_devclass(9) and devclass(9)).  Various
       other attributes of the device include  a  unit  number  (see  device_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 attached

       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.

Debian                                            June 16, 1998                                        DEVICE(9)