[PATCH kernel] powerpc/iommu: Add iommu_ops to report capabilities and allow blocking domains

[Tian, Kevin]

> From: Alexey Kardashevskiy <aik at ozlabs.ru>
> Sent: Friday, July 8, 2022 5:46 PM
> 
> >>>
> >>> In general, is "domain" something from hardware or it is a software
> >>> concept? Thanks,
> >>>
> >
> > 'domain' is a software concept to represent the hardware I/O page
> > table. A blocking domain means all DMAs from a device attached to
> > this domain are blocked/rejected (equivalent to an empty I/O page
> > table), usually enforced in the .attach_dev() callback.
> >
> > Yes, a comment for why having a NULL .attach_dev() is OK is welcomed.
> 
> 
> Making it NULL makes __iommu_attach_device() fail, .attach_dev() needs
> to return 0 in this crippled environment. Thanks for explaining the
> rest, good food for thoughts.
> 

Yeah, that's a typo. 😊