virtdir_offset
st->st_ino = (ino_t)virtdir_offset(&fwcfg_virtdir, ep) + 10;
off_t virtdir_offset(const virtdir_t *, const virt_dirent_t *);
st->st_ino = virtdir_offset(&pci, ep) + 10;
int virtdir_offset(virtdir_t *, virt_dirent_t *);