PCI: Add support for DMA alias quirks

Some devices are broken and use a requester ID other than their physical
devfn.  Add a byte, using an existing gap in the pci_dev structure, to
store an alternate "alias" devfn.  A bit in the dev_flags tells us when
this is valid.  We then add the alias as one more step in the
pci_for_each_dma_alias() iterator.

Tested-by: George Spelvin <linux@horizon.com>
Tested-by: Pat Erley <pat-lkml@erley.org>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index 5601cdb8bbb3..2c19f3f40621 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -37,6 +37,17 @@ int pci_for_each_dma_alias(struct pci_dev *pdev,
         if (ret)
                 return ret;
 
+        /*
+         * If the device is broken and uses an alias requester ID for
+         * DMA, iterate over that too.
+         */
+        if (unlikely(pdev->dev_flags & PCI_DEV_FLAGS_DMA_ALIAS_DEVFN)) {
+                ret = fn(pdev, PCI_DEVID(pdev->bus->number,
+                                         pdev->dma_alias_devfn), data);
+                if (ret)
+                        return ret;
+        }
+
         for (bus = pdev->bus; !pci_is_root_bus(bus); bus = bus->parent) {
                 struct pci_dev *tmp;