Hehe, that was the only part of this article I didn't particularly love. This is how it works: A handle ID is a 64bit integer. If lowest bit (BUS1_NODE_FLAG_MANAGED) is set it is a handle ID allocated by the kernel (the only mode currently supported). If the second lowest bit (BUS1_NODE_FLAG_ALLOCATE) is set a new handle should be allocated by the kernel, otherwise the handle ID must refer to an existing handle.