[PATCH v6 1/5] iommu: Return -EMEDIUMTYPE for incompatible domain and device/group

[Tian, Kevin]

> From: Jason Gunthorpe <jgg at nvidia.com>
> Sent: Friday, September 9, 2022 8:08 PM
> 
> 
> > As discussed in a side thread a note might be added to exempt calling
> > kAPI outside of the iommu driver.
> 
> Sadly, not really.. The driver is responsible to santize this if it is
> relevant. It is the main downside of this approach.
> 

Better provide a clarification on what sanitization means.

e.g. I don't think we should change errno in those kAPIs to match the
definition in iommu subsystem since e.g. -EINVAL really means different
things in different context.

So the sanitization in iommu driver is probably that:

  - If an external kAPI returns -EINVAL, convert it to -ENODEV given iommu
    domain is iommu internal object hence unlikely for external kAPIs to
    capture incompatibility issue between domain/device;
  - Otherwise just pass whatever returned to the caller, following the definition
    of "Same behavior as -ENODEV" above

Thanks
Kevin