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

[Joerg Roedel]

On Mon, Aug 15, 2022 at 11:14:33AM -0700, Nicolin Chen wrote:
> Provide a dedicated errno from the IOMMU driver during attach that the
> reason attached failed is because of domain incompatability. EMEDIUMTYPE
> is chosen because it is never used within the iommu subsystem today and
> evokes a sense that the 'medium' aka the domain is incompatible.

I am not a fan of re-using EMEDIUMTYPE or any other special value. What
is needed here in EINVAL, but with a way to tell the caller which of the
function parameters is actually invalid.

For that I prefer adding an additional pointer parameter to the attach
functions in which the reason for the failure can be communicated up the
chain.

For the top-level iommu_attach_device() function I am okay with having a
special version which has this additional paremter.

Regards,

	Joerg