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Enumeration of Interfaces on USB Composite Devices

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Interfaces on a composite USB device can be grouped in collections or represent one USB function individually. When the interfaces are not grouped in collections, the generic parent driver creates a PDO for each interface and generates a set of hardware IDs for each PDO.

The device ID for an interface PDO has the following form:

USB\VID_v(4)&PID_p(4)&MI_z(2)

In these IDs:

  • v(4) is the four-digit vendor code that the USB standards committee assigns to the vendor.
  • p(4) is the four-digit product code that the vendor assigns to the device.
  • z(2) is the interface number that is extracted from the bInterfaceNumber field of the interface descriptor.

The generic parent driver also generates the following compatible IDs by using the information from the interface descriptor (USB_INTERFACE_DESCRIPTOR):

USB\CLASS_d(2)&SUBCLASS_s(2)&PROT_p(2)

USB\CLASS_d(2)&SUBCLASS_s(2)

USB\CLASS_d(2)

In these IDs:

  • d(2) is the class code (bInterfaceClass)
  • s(2) is the subclass code (bInterfaceSubClass)
  • p(2) is the protocol code (bInterfaceProtocol)

Each of these codes is a four-digit number.

Enumeration of Interface Collections on USB Composite Devices
USB Generic Parent Driver (Usbccgp.sys)
Microsoft-provided USB drivers