usb_fs_open
struct usb_fs_open fs_open;
struct usb_fs_open *popen;
error = usb_fs_open(f, u.popen, fflags,
usb_fs_open(struct usb_fifo *f, struct usb_fs_open *popen,
struct usb_fs_open fs_open;
#define USB_FS_OPEN _IOWR('U', 197, struct usb_fs_open)