window usb struct

http://www.eetop.cn/blog/html/97/24597-1390.html
http://www.eetop.cn/blog/html/97/24597-1391.html
http://www.eetop.cn/blog/html/97/24597-1392.html

FreeBSD ehci source code

http://fxr.watson.org/fxr/source/pc/usbehci.c?v=PLAN9