vdisk_ioctl
static int vdisk_ioctl(struct open_file *, ulong_t, void *);
.dv_ioctl = vdisk_ioctl,
status = (*dev->vdisk_ioctl)(dev->vdisk, cmd, (uintptr_t)arg);
ASSERT(dev->vdisk_ioctl != NULL);
vd_efi_ioctl_func vdisk_ioctl; /* vdisk ioctl function */
(efi_dev).vdisk_ioctl = ioctl; \