usbpf_pkthdr
struct usbpf_pkthdr *up;
up = (struct usbpf_pkthdr *)ptr;
(sizeof(struct usbpf_pkthdr) == USBPF_HDR_LEN) ? 1 : -1];
const int addr_off = (uintptr_t)&((struct usbpf_pkthdr *)0)->up_address;
const int addr_ep = (uintptr_t)&((struct usbpf_pkthdr *)0)->up_endpoint;
struct usbpf_pkthdr up_temp;
struct usbpf_pkthdr *up;