2 files changed, 82 insertions, 0 deletions

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 888cb9f5c5fb..e5099919e574 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -329,6 +329,87 @@ static struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle)
         return NULL;
 }
 
+struct acpi_handle_node {
+        struct list_head node;
+        acpi_handle handle;
+};
+
+/**
+ * acpi_get_pci_dev - convert ACPI CA handle to struct pci_dev
+ * @handle: the handle in question
+ *
+ * Given an ACPI CA handle, the desired PCI device is located in the
+ * list of PCI devices.
+ *
+ * If the device is found, its reference count is increased and this
+ * function returns a pointer to its data structure.  The caller must
+ * decrement the reference count by calling pci_dev_put().
+ * If no device is found, %NULL is returned.
+ */
+struct pci_dev *acpi_get_pci_dev(acpi_handle handle)
+{
+        int dev, fn;
+        unsigned long long adr;
+        acpi_status status;
+        acpi_handle phandle;
+        struct pci_bus *pbus;
+        struct pci_dev *pdev = NULL;
+        struct acpi_handle_node *node, *tmp;
+        struct acpi_pci_root *root;
+        LIST_HEAD(device_list);
+
+        /*
+         * Walk up the ACPI CA namespace until we reach a PCI root bridge.
+         */
+        phandle = handle;
+        while (!acpi_is_root_bridge(phandle)) {
+                node = kzalloc(sizeof(struct acpi_handle_node), GFP_KERNEL);
+                if (!node)
+                        goto out;
+
+                INIT_LIST_HEAD(&node->node);
+                node->handle = phandle;
+                list_add(&node->node, &device_list);
+
+                status = acpi_get_parent(phandle, &phandle);
+                if (ACPI_FAILURE(status))
+                        goto out;
+        }
+
+        root = acpi_pci_find_root(phandle);
+        if (!root)
+                goto out;
+
+        pbus = root->bus;
+
+        /*
+         * Now, walk back down the PCI device tree until we return to our
+         * original handle. Assumes that everything between the PCI root
+         * bridge and the device we're looking for must be a P2P bridge.
+         */
+        list_for_each_entry(node, &device_list, node) {
+                acpi_handle hnd = node->handle;
+                status = acpi_evaluate_integer(hnd, "_ADR", NULL, &adr);
+                if (ACPI_FAILURE(status))
+                        goto out;
+                dev = (adr >> 16) & 0xffff;
+                fn  = adr & 0xffff;
+
+                pdev = pci_get_slot(pbus, PCI_DEVFN(dev, fn));
+                if (hnd == handle)
+                        break;
+
+                pbus = pdev->subordinate;
+                pci_dev_put(pdev);
+        }
+out:
+        list_for_each_entry_safe(node, tmp, &device_list, node)
+                kfree(node);
+
+        return pdev;
+}
+EXPORT_SYMBOL_GPL(acpi_get_pci_dev);
+
 /**
  * acpi_pci_osc_control_set - commit requested control to Firmware
  * @handle: acpi_handle for the target ACPI object
diff --git a/include/acpi/acpi_drivers.h b/include/acpi/acpi_drivers.h
index 7a2ce53146aa..dbe3989952ee 100644
--- a/include/acpi/acpi_drivers.h
+++ b/include/acpi/acpi_drivers.h
@@ -98,6 +98,7 @@ void acpi_pci_irq_del_prt(int segment, int bus);
 
 struct pci_bus;
 
+struct pci_dev *acpi_get_pci_dev(acpi_handle);
 acpi_status acpi_get_pci_id(acpi_handle handle, struct acpi_pci_id *id);
 int acpi_pci_bind_root(struct acpi_device *device, struct acpi_pci_id *id,
                        struct pci_bus *bus);