PATHHardware Documentation > USB Devices > Mac OS USB DDK API Reference

Overview

The USB Manager maintains a database of all the currently connected devices that communicate using the USB protocol. Whenever a device is added to the USB, it is the responsibility of the USB Manager to register the device with the Name Registry and load the device's driver software. In the event of a device being removed, the USB Manager must ensure that the driver is removed cleanly from the system and all references to the device in the Name Registry are removed.

Figure 5-1 depicts the sequence of events that the USB Manager participates in when a device is added to the USB.

Figure 5-1 Device addition event sequence on the USB

The USB Manager consists of native code fragments wrapped in a file of type 'expt' . During the Macintosh boot sequence, the USB Manager is loaded immediately following all native drivers ('ndrv') and before generic INIT files. The USB Manager resides in the Extensions folder.

The USB Manager is responsible for the following services which support the USB architecture.

• Maintain USB topology in database: keep updated information about the USB in the Name Registry and dynamically update the information as devices are added or removed from the bus.
• Provide access functions for database information: Device information needed by either the USL or a device driver should be accessible via the USB Manager.
• Generate unique opaque bus reference, a USBBusRef defined is a USBReference (SInt32), when a root hub is detected/loaded. For possible future use, a unique bus reference is generated by the USB Manager for each instantiated root hub. Every device record stores the bus reference of the bus.

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