IOMMU_GET_HW_INFO
IOCTL_OP(IOMMU_GET_HW_INFO, iommufd_get_hw_info, struct iommu_hw_info,
TEST_LENGTH(iommu_hw_info, IOMMU_GET_HW_INFO, __reserved);
ret = ioctl(fd, IOMMU_GET_HW_INFO, &cmd);