On Wed, Oct 09, 2024 at 09:38:11AM -0700, Nicolin Chen wrote: > Add a new driver-type for ARM SMMUv3 to enum iommu_viommu_type. Implement > +static inline struct iommufd_viommu * > +arm_vsmmu_alloc(struct iommu_device *iommu_dev, struct iommu_domain *parent, > + struct iommufd_ctx *ictx, unsigned int viommu_type) > +{ > + return ERR_PTR(-EOPNOTSUPP); > +} Let's do #define NULL here instead so we don't get an op at all. > +struct iommufd_viommu * > +arm_vsmmu_alloc(struct iommu_device *iommu_dev, struct iommu_domain *parent, > + struct iommufd_ctx *ictx, unsigned int viommu_type) > +{ > + struct arm_smmu_device *smmu = > + container_of(iommu_dev, struct arm_smmu_device, iommu); > + struct arm_smmu_domain *s2_parent = to_smmu_domain(parent); > + struct arm_vsmmu *vsmmu; > + > + if (viommu_type != IOMMU_VIOMMU_TYPE_ARM_SMMUV3) > + return ERR_PTR(-EOPNOTSUPP); So what happens if the user tries to create a default domain? It skips this and just creates an normal viommu object But then what? The driver needs to make sure it never casts that to a arm_vsmmu ? How? Jason