> From: Robin Murphy <robin.murphy@xxxxxxx> > Sent: Wednesday, July 6, 2022 1:08 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. > Suppose we miss a check on iommu ops in iommu_release_device(): if (!dev->iommu) <<<<<<< return; iommu_device_unlink(dev->iommu->iommu_dev, dev); ops = dev_iommu_ops(dev); ops->release_device(dev); following the rationale in patch01 a device could be removed when it's associated with a known but not registered instance.
