This series adds initial support for being able to use the ARM SMMU driver as a loadable kernel module. The series also adds to the IOMMU framework, so that it can defer probing for devices that depend on an IOMMU driver that may be a loadable module. The primary reason behind these changes is that having the ARM SMMU driver as a module allows for the same kernel image to be used across different platforms. For example, if one platform contains an IOMMU that implements one version of the ARM SMMU specification, and another platform simply does not have an IOMMU, the only way that these platforms can share the same kernel image is if the ARM SMMU driver is compiled into the kernel image. This solution is not scalable, as it will lead to bloating the kernel image with support for several future versions of the SMMU specification to maintain a common kernel image that works across all platforms. Having the ARM SMMU driver as a module allows for a common kernel image to be supported across all platforms, while yielding a smaller kernel image size, since the correct SMMU driver can be loaded at runtime, if necessary. Patchset Summary: 1. Since the ARM SMMU driver depends on symbols being exported from several subsystems, the first three patches are dedicated to exporting the necessary symbols. 2. Similar to how the pinctrl framework handles deferring probes, the subsequent patch makes it so that the IOMMU framework will defer probes indefinitely if there is a chance that the IOMMU driver that a device is waiting for is a module. Otherwise, it upholds the current behavior of stopping probe deferrals once all of the builtin drivers have finished probing. The ARM SMMU driver currently has support for the deprecated "mmu-masters" binding, which relies on the notion of initcall ordering for setting the bus ops to ensure that all SMMU devices have been bound to the driver. This poses a problem with making the driver a module, as there is no such notion with loadable modules. Will support for this be completely deprecated? If not, might it be useful to leverage the device tree ordering, and assign a property to the last SMMU device, and set the bus ops at that point? Or perhaps have some deferred timer based approach to know when to set the bus ops? Thanks, Isaac Isaac J. Manjarres (4): of: Export of_phandle_iterator_args() to modules PCI: Export PCI ACS and DMA searching functions to modules iommu: Export core IOMMU functions to kernel modules iommu: Add probe deferral support for IOMMU kernel modules drivers/iommu/iommu-sysfs.c | 3 +++ drivers/iommu/iommu.c | 6 ++++++ drivers/iommu/of_iommu.c | 8 ++++++-- drivers/of/base.c | 1 + drivers/pci/pci.c | 1 + drivers/pci/search.c | 1 + 6 files changed, 18 insertions(+), 2 deletions(-) -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project
