Extern or forward variable declaration at include/linux/iommu.h, line 47 References: arch/arm/mm/dma-mapping.c, line 2141 drivers/gpu/host1x/bus.c, line 331 drivers/iommu/iommu.c, line 113 drivers/iommu/iommu.c, line 1168 drivers/iommu/iommu.c, line 1217 drivers/iommu/iommu.c, line 1235 drivers/iommu/iommu.c, line 1241 drivers/iommu/iommu.c, line 1273 drivers/iommu/iommu.c, line 1293 drivers/thunderbolt/domain.c, line 302 drivers/vfio/mdev/mdev_driver.c, line 75 drivers/vfio/vfio_iommu_type1.c, line 1183 drivers/vfio/vfio_iommu_type1.c, line 1349 include/linux/iommu.h, line 47 include/linux/iommu.h, line 286 include/linux/iommu.h, line 287 include/linux/iommu.h, line 288 include/linux/iommu.h, line 289 include/linux/iommu.h, line 412 include/linux/iommu.h, line 417 include/linux/iommu.h, line 422