[PATCH 4/5] iommu: Regulate errno in ->attach_dev callback functions

[Jason Gunthorpe]

On Tue, Sep 13, 2022 at 01:27:03PM +0100, Jean-Philippe Brucker wrote:
> I think in the future it will be too easy to forget about the constrained
> return value of attach() while modifying some other part of the driver,
> and let an external helper return EINVAL. So I'd rather not propagate ret
> from outside of viommu_domain_attach() and finalise().

Fortunately, if -EINVAL is wrongly returned it only creates an
inefficiency, not a functional problem. So we do not need to be
precise here.

> Since we can't guarantee that APIs like virtio or ida won't ever return
> EINVAL, we should set all return values:

I dislike this alot, it squashes all return codes to try to optimize
an obscure failure path :(

Jason