to list all the devices in freebsd &definition analyse

[kylin]

I
i can use pciconf in freebsd to list the pci device ,but how to list
the device tree in freeebsd?
II
i got some anornymous definition on devclass driver and device that
differ from the current man page
i think they seems reasonable but how can devclass  Represents a bus
or leaf device driver while driver still Represents a bus or
leaf-level end-device driver ?
and device is just a instance of bus or (leaf) end-device.??
is it oop? can the disigner of the arch show us a word?:)

devclass
Represents a bus or leaf device driver, e.g. pci_devclass (PCI bus),
ahc_devclass (Adaptec SCSI host-bus adapter). It contains a list of
drivers that belong to it. At run-time it also has a list populated by
device instances of this class indexed by unit numbers.
driver
Represents a bus or leaf-level end-device driver. Each driver forms a
devclass. All drivers are attached to single parent devclass (with the
exception of root_devclass). Drivers have list of methods/operations
e.g. probe/attach that are also inherited by it's instance devices.
device
Represents an instance of bus or (leaf) end-device. All devices have
unique unit numbers in class to which they belong. Each device has one
parent and may have a list of children. Devices inherit their
operations and class from driver to which they belong. Device can be
in any of the states as defined in device_state_t below



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