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

Callback Routine for Device Notification

The callback routine, callback routine parameter block, and callback notification request functions used for device notification are listed in this section.

The device notification mechanism is used to inform clients when devices are added and removed from the USB. Clients register for notification services using the USBInstallDeviceNotification function and can request all notifications or a specific notification type. Whenever a device or interface is added or removed from the bus, all registered clients are called back with the information about the device or interface.

Clients that register for notifications must be sure to un-register with the USBRemoveDeviceNotification function before their code fragment is unloaded.

The callback routine is always called at task time, and may allocate memory, make Macintosh Toolbox calls, or perform other system maintenance operations.

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