[patch RFC 21/38] PCI: MSI: Provide pci_dev_has_special_msi_domain() helper

[Thomas Gleixner <tglx@xxxxxxxxxxxxx>]

Provide a helper function to check whether a PCI device is handled by a
non-standard PCI/MSI domain. This will be used to exclude such devices
which hang of a special bus, e.g. VMD, to be excluded from the irq domain
override in irq remapping.

Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
Cc: linux-pci@xxxxxxxxxxxxxxx
---
 drivers/pci/msi.c   |   22 ++++++++++++++++++++++
 include/linux/msi.h |    1 +
 2 files changed, 23 insertions(+)

--- a/drivers/pci/msi.c
+++ b/drivers/pci/msi.c
@@ -1553,4 +1553,26 @@ struct irq_domain *pci_msi_get_device_do
                                             DOMAIN_BUS_PCI_MSI);
        return dom;
 }
+
+/**
+ * pci_dev_has_special_msi_domain - Check whether the device is handled by
+ *                                 a non-standard PCI-MSI domain
+ * @pdev:      The PCI device to check.
+ *
+ * Returns: True if the device irqdomain or the bus irqdomain is
+ * non-standard PCI/MSI.
+ */
+bool pci_dev_has_special_msi_domain(struct pci_dev *pdev)
+{
+       struct irq_domain *dom = dev_get_msi_domain(&pdev->dev);
+
+       if (!dom)
+               dom = dev_get_msi_domain(&pdev->bus->dev);
+
+       if (!dom)
+               return true;
+
+       return dom->bus_token != DOMAIN_BUS_PCI_MSI;
+}
+
 #endif /* CONFIG_PCI_MSI_IRQ_DOMAIN */
--- a/include/linux/msi.h
+++ b/include/linux/msi.h
@@ -374,6 +374,7 @@ int pci_msi_domain_check_cap(struct irq_
                             struct msi_domain_info *info, struct device *dev);
 u32 pci_msi_domain_get_msi_rid(struct irq_domain *domain, struct pci_dev 
*pdev);
 struct irq_domain *pci_msi_get_device_domain(struct pci_dev *pdev);
+bool pci_dev_has_special_msi_domain(struct pci_dev *pdev);
 #else
 static inline struct irq_domain *pci_msi_get_device_domain(struct pci_dev 
*pdev)
 {