what is the init entrance for pci bus scan in FREEbsd?

Now i am coding a fake pcihotplug module in Freebsd 5.3 release,
it contains two parts ,the userplace using a ioctl way to communicate
with an cdev in /dev, and the kernel module which
mainly operates on the Devclasses ,devlist and driverlist ....but
still in the enable function,i have to rescan the pci bus. BUT, i can
not find the pci bus scan code in the freebsd,i guess it was just an
entry of the startup table which is made by compiler,
still some one told me to follow the pci_init() way in LINUX ,but , i
find it too hard in the OO structure bus arch of Freebsd .so
WHERE can i get some code to follow in order to finish my pci rescan function? 

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