ocr: Mac OS layer Application ADB Chooser Comm File Manager Other extension Toolbox System ADB shim HCDM shim I Software Hub Keyboard Mouse Other Printer Comm Mass USB class driver Composite class driver class driver class driver Storage driver ! driver layer USB Services Library (USL) USB Services USB Manager Hardware abstraction layer OpenHCI UIM UIM UIM (tuture) (future) USB Intertace Module Root hub (UIM) simulation - - USB Hardware OpenHCI Controller PCI Card Root hub cards bus connectors on computer Devices Devices Devices