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This article describes an independent driver called the USB generic parent driver (Usbccgp.sys) that Microsoft provides Microsoft for composite devices.
Many USB devices expose multiple USB interfaces. These devices are called composite devices. The Windows operating system includes a generic parent facility in the USB bus driver (Usbhub.sys) that exposes each interface of the composite device as a separate device. This facility is streamlined and improved by transferring it to an independent driver called the USB generic parent driver (Usbccgp.sys). Device vendors can use the generic parent driver to make selective use of Microsoft-supplied driver support for some interfaces.
The interfaces of some composite devices operate independently. For example, a composite USB keyboard with power buttons might have one interface for the keyboard and another interface for the power buttons. The USB generic parent driver enumerates each of these interfaces as a separate device. The operating system loads the Microsoft-supplied keyboard driver to manage the keyboard interface. It loads the Microsoft-supplied power keys driver to manage the power keys interface.
If the native Windows drivers don't support a device's interface, the vendor of the device should provide a driver for the interface and an information (INF) file. The INF file should have an INF DDInstall section that matches the device ID of the interface. The INF file must not match the device ID for the composite device itself. This configuration prevents the generic parent driver from loading. For an explanation of how the operating system loads the USB generic parent driver, see Enumeration of USB composite devices.
Some devices group interfaces into interface collections that work together to perform a function. When interfaces are grouped in interface collections, the generic parent driver treats each collection as a device, rather than each individual interface. For more information, see Overview of enumeration of interface collections on USB composite devices.
After Windows loads the client drivers for the interfaces of a composite device, the generic parent driver multiplexes the data flow from the client drivers. It combines the separate interactions into a single data stream for the composite device. The generic parent is power policy owner for the entire composite device and all of its interfaces. It also manages synchronization and Plug and Play requests.
If Microsoft-supplied drivers support some interfaces but not others, the generic parent driver can simplify the task for vendors of composite hardware. Vendors only need to supply drivers for the unsupported interfaces. The generic parent driver facilitates the use of Microsoft-supplied drivers for the supported interfaces.
The following articles describe the features and functions of the generic parent driver:
- Enumeration of USB composite devices
- Descriptors on USB composite devices
- Enumeration of interfaces on USB composite devices
- Enumeration of interface collections on USB composite devices
- Content security features in Usbccgp.sys