We utilize the IOMMU_INIT macros to create this dependency:

               [null]
                 |
       [pci_xen_swiotlb_detect]
                 |
       [pci_swiotlb_detect_override]
                 |
       [pci_swiotlb_detect_4gb]
                 |
         +-------+--------+---------------------+
        /                  \                     \
[detect_calgary]    [gart_iommu_hole_init]   [detect_intel_iommu]
                            |
                    [amd_iommu_detect]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
LKML-Reference: <1282845485-8991-10-git-send-email-konrad.wilk@oracle.com>
CC: Fujita Tomonori <fujita.tomonori@lab.ntt.co.jp>
CC: Jesse Barnes <jbarnes@virtuousgeek.org>
CC: David Woodhouse <David.Woodhouse@intel.com>
CC: Len Brown <len.brown@intel.com>
CC: Chris Wright <chrisw@sous-sol.org>
CC: Yinghai Lu <yinghai@kernel.org>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>