usb architecture

Hi....

I am working on linux drivers, now my project is on usb .
i have a good knowledge on usb in case of windows platform, but i do
not know about the architecture of usb in linux.
i have gone through some documents in linux on usb, but i did not get
how the enumaration happens in linux, and what is role of PNP manager
in case of linux, and role of I/O manager.
Is there any things like Registry Data base in linux to maintain all
the driver information ?
At the time of loading  a usb device driver the pnp manager looks in to
the registry information in case of windows, how that will be in case
od linux?

thanks and regards

shiva