OHCI
OHCI (Open Host Controller Interface) is a standardized interface for the connection of an USB 1.1 host controller to the PCI bus. The driver for OHCI in ReactOS is usbohci.sys.
OHCI supports USB 1.1 full and low speed devices. It does not support USB 2.0 or "high speed" devices.
Source Code
The path for the source code of usbohci.sys is /reactos/drivers/usb/usbohci/.
For high level functionality of the driver the libusb is used (reactos/lib/drivers/libusb). Thus changes in libusb influence the functionality usbohci.sys.
