The USB software layers (1)

• The code executed by the host controller handles the traffic across the USB bus (see previous lecture)

• The host controller interfaces the PC through a set of I/O ports

• A first software layer (UHDCI or OHDCI) manages the I/O ports of the host controller and allows the upper level software layer to issue requests to USB devices by means of USB Request Blocks (URB): see drivers/usb/uhci.c, drivers/usb/usb-uhci.c, and drivers/usb/usb-ohdci.c