[PATCH v4 04/16] iommu: Always register bus notifiers

[Tian, Kevin]

> From: Robin Murphy <robin.murphy at arm.com>
> Sent: Tuesday, August 16, 2022 12:20 AM
> 
> The number of bus types that the IOMMU subsystem deals with is small and
> manageable, so pull that list into core code as a first step towards
> cleaning up all the boilerplate bus-awareness from drivers. Calling
> iommu_probe_device() before bus->iommu_ops is set will simply return
> -ENODEV and not break the notifier call chain, so there should be no
> harm in proactively registering all our bus notifiers at init time.
> 
> Tested-by: Marek Szyprowski <m.szyprowski at samsung.com>
> Tested-by: Matthew Rosato <mjrosato at linux.ibm.com> # s390
> Tested-by: Niklas Schnelle <schnelle at linux.ibm.com> # s390
> Signed-off-by: Robin Murphy <robin.murphy at arm.com>

Reviewed-by: Kevin Tian <kevin.tian at intel.com>