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: NDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: NBjorn Helgaas <bhelgaas@google.com>

drivers/pci/mmap.c

@@ -48,9 +48,7 @@ int pci_mmap_resource_range(struct pci_dev *pdev, int bar,
 			    enum pci_mmap_state mmap_state, int write_combine)
 {
 	unsigned long size;
-
-	if (mmap_state == pci_mmap_io)
-		return -EINVAL;
+	int ret;
 
 	size = ((pci_resource_len(pdev, bar) - 1) >> PAGE_SHIFT) + 1;
 	if (vma->vm_pgoff + vma_pages(vma) > size)
@@ -61,7 +59,13 @@ int pci_mmap_resource_range(struct pci_dev *pdev, int bar,
 	else
 		vma->vm_page_prot = pgprot_device(vma->vm_page_prot);
 
-	vma->vm_pgoff += (pci_resource_start(pdev, bar) >> PAGE_SHIFT);
+	if (mmap_state == pci_mmap_io) {
+		ret = pci_iobar_pfn(pdev, bar, vma);
+		if (ret)
+			return ret;
+	} else
+		vma->vm_pgoff += (pci_resource_start(pdev, bar) >> PAGE_SHIFT);
+
 	vma->vm_ops = &pci_phys_vm_ops;
 
 	return io_remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,

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