PCI: Add I/O BAR support to generic pci_mmap_resource_range()

This will need to call into an arch-provided pci_iobar_pfn() function.

Signed-off-by: David Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 98a72ab..9f30244 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1648,8 +1648,12 @@ int pci_mmap_page_range(struct pci_dev *pdev, int bar,
 #ifndef arch_can_pci_mmap_wc
 #define arch_can_pci_mmap_wc()		0
 #endif
+
 #ifndef arch_can_pci_mmap_io
 #define arch_can_pci_mmap_io()		0
+#define pci_iobar_pfn(pdev, bar, vma) (-EINVAL)
+#else
+int pci_iobar_pfn(struct pci_dev *pdev, int bar, struct vm_area_struct *vma);
 #endif
 
 #ifndef pci_root_bus_fwnode