Hi all, As part of the work to enable a "Generic Kernel Image" across multiple Android devices, there is a need to seperate shared, core kernel code from modular driver code that may not be needed by all SoCs. This means building IOMMU drivers as modules.
It turns out that most of the groundwork has already been done to enable the ARM SMMU drivers to be 'tristate' options in drivers/iommu/Kconfig; with a few symbols exported from the IOMMU/PCI core, everything builds nicely out of the box. The one exception is support for the legacy SMMU DT binding, which is not in widespread use and has never worked with modules, so we can simply remove that when building as a module rather than try to paper over it with even more hacks. Obviously you need to be careful about using IOMMU drivers as modules, since late loading of the driver for an IOMMU serving active DMA masters is going to end badly in many cases. On Android, we're using device links to ensure that the IOMMU probes first. Comments welcome, Will Cc: Robin Murphy <robin.mur...@arm.com> Cc: Joerg Roedel <j...@8bytes.org> Cc: Bjorn Helgaas <bhelg...@google.com> Cc: Lorenzo Pieralisi <lorenzo.pieral...@arm.com> --->8 Will Deacon (7): drivers/iommu: Export core IOMMU API symbols to permit modular drivers iommu/of: Request ACS from the PCI core when configuring IOMMU linkage PCI: Export pci_ats_disabled() as a GPL symbol to modules Revert "iommu/arm-smmu: Make arm-smmu-v3 explicitly non-modular" iommu/arm-smmu-v3: Allow building as a module Revert "iommu/arm-smmu: Make arm-smmu explicitly non-modular" iommu/arm-smmu: Allow building as a module drivers/iommu/Kconfig | 16 ++++++- drivers/iommu/arm-smmu-impl.c | 6 +++ drivers/iommu/arm-smmu-v3.c | 26 +++++++---- drivers/iommu/arm-smmu.c | 86 +++++++++++++++++++++-------------- drivers/iommu/iommu-sysfs.c | 5 ++ drivers/iommu/iommu.c | 8 ++++ drivers/iommu/of_iommu.c | 1 + drivers/pci/pci.c | 1 + 8 files changed, 102 insertions(+), 47 deletions(-) -- 2.24.0.rc0.303.g954a862665-goog _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu
