This variant is returned if the device’s vendor ID and device ID exist
in the PCI ID database, and information such as a string representing
the name of the vendor or device can be returned.
This variant is returned if the device’s vendor ID or device ID were not
found in the PCI ID database.
This is not necessarily an error, as it may indicate that the database
has not been updated to include a newer device, the device is a
prototype that has not yet been registered with PCI-SIG, or the device
is not a “real” device but an emulated device provided by a virtual
machine. An unknown device may still be used, provided that its
Class, Subclass, and prog IF provide sufficient information to
program that device.