[PATCH v4 03/16] PCI: quirk pci_for_each_dma_alias()

[Alex Williamson <alex.williamson@redhat.com>]

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.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/pci/search.c |   11 +++++++++++
 include/linux/pci.h  |    3 +++
 2 files changed, 14 insertions(+)

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index 5601cdb..2c19f3f 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;
 
diff --git a/include/linux/pci.h b/include/linux/pci.h
index 545903d..9d4035c 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -171,6 +171,8 @@ enum pci_dev_flags {
 	PCI_DEV_FLAGS_ASSIGNED = (__force pci_dev_flags_t) (1 << 2),
 	/* Flag for quirk use to store if quirk-specific ACS is enabled */
 	PCI_DEV_FLAGS_ACS_ENABLED_QUIRK = (__force pci_dev_flags_t) (1 << 3),
+	/* Flag to indicate the device uses dma_alias_devfn */
+	PCI_DEV_FLAGS_DMA_ALIAS_DEVFN = (__force pci_dev_flags_t) (1 << 4),
 };
 
 enum pci_irq_reroute_variant {
@@ -268,6 +270,7 @@ struct pci_dev {
 	u8		rom_base_reg;	/* which config register controls the ROM */
 	u8		pin;		/* which interrupt pin this device uses */
 	u16		pcie_flags_reg;	/* cached PCIe Capabilities Register */
+	u8		dma_alias_devfn;/* devfn of DMA alias, if any */
 
 	struct pci_driver *driver;	/* which driver has allocated this device */
 	u64		dma_mask;	/* Mask of the bits of bus address this