RE: [PATCH v2 01/11] iommu: Add new iommu op to create domains owned by userspace

[Tian, Kevin]

> From: Liu, Yi L <yi.l.liu@xxxxxxxxx>
> Sent: Thursday, May 11, 2023 10:39 PM
> @@ -229,6 +238,15 @@ struct iommu_iotlb_gather {
>   *           after use. Return the data buffer if success, or ERR_PTR on
>   *           failure.
>   * @domain_alloc: allocate iommu domain
> + * @domain_alloc_user: allocate user iommu domain
> + * @domain_alloc_user_data_len: return the required length of the user
> data
> + *                              to allocate a specific type user iommu domain.
> + *                              @hwpt_type is defined as enum iommu_hwpt_type
> + *                              in include/uapi/linux/iommufd.h. The returned
> + *                              length is the corresponding sizeof driver data
> + *                              structures in include/uapi/linux/iommufd.h.
> + *                              -EOPNOTSUPP would be returned if the input
> + *                              @hwpt_type is not supported by the driver.

Can this be merged with earlier @hw_info callback? That will already
report a list of supported hwpt types. is there a problem to further
describe the data length for each type in that interface?