3 files changed, 98 insertions, 22 deletions

diff --git a/drivers/acpi/glue.c b/drivers/acpi/glue.c
index 17e15d11bd39..408f6b2a5fa8 100644
--- a/drivers/acpi/glue.c
+++ b/drivers/acpi/glue.c
@@ -79,34 +79,99 @@ static struct acpi_bus_type *acpi_get_bus_type(struct device *dev)
         return ret;
 }
 
-static acpi_status do_acpi_find_child(acpi_handle handle, u32 lvl_not_used,
-                                      void *addr_p, void **ret_p)
+static acpi_status acpi_dev_present(acpi_handle handle, u32 lvl_not_used,
+                                  void *not_used, void **ret_p)
 {
-        unsigned long long addr, sta;
-        acpi_status status;
+        struct acpi_device *adev = NULL;
 
-        status = acpi_evaluate_integer(handle, METHOD_NAME__ADR, NULL, &addr);
-        if (ACPI_SUCCESS(status) && addr == *((u64 *)addr_p)) {
+        acpi_bus_get_device(handle, &adev);
+        if (adev) {
                 *ret_p = handle;
-                status = acpi_bus_get_status_handle(handle, &sta);
-                if (ACPI_SUCCESS(status) && (sta & ACPI_STA_DEVICE_ENABLED))
-                        return AE_CTRL_TERMINATE;
+                return AE_CTRL_TERMINATE;
         }
         return AE_OK;
 }
 
-acpi_handle acpi_get_child(acpi_handle parent, u64 address)
+static bool acpi_extra_checks_passed(acpi_handle handle, bool is_bridge)
 {
-        void *ret = NULL;
+        unsigned long long sta;
+        acpi_status status;
+
+        status = acpi_bus_get_status_handle(handle, &sta);
+        if (ACPI_FAILURE(status) || !(sta & ACPI_STA_DEVICE_ENABLED))
+                return false;
+
+        if (is_bridge) {
+                void *test = NULL;
+
+                /* Check if this object has at least one child device. */
+                acpi_walk_namespace(ACPI_TYPE_DEVICE, handle, 1,
+                                    acpi_dev_present, NULL, NULL, &test);
+                return !!test;
+        }
+        return true;
+}
+
+struct find_child_context {
+        u64 addr;
+        bool is_bridge;
+        acpi_handle ret;
+        bool ret_checked;
+};
+
+static acpi_status do_find_child(acpi_handle handle, u32 lvl_not_used,
+                                 void *data, void **not_used)
+{
+        struct find_child_context *context = data;
+        unsigned long long addr;
+        acpi_status status;
 
-        if (!parent)
-                return NULL;
+        status = acpi_evaluate_integer(handle, METHOD_NAME__ADR, NULL, &addr);
+        if (ACPI_FAILURE(status) || addr != context->addr)
+                return AE_OK;
 
-        acpi_walk_namespace(ACPI_TYPE_DEVICE, parent, 1, NULL,
-                            do_acpi_find_child, &address, &ret);
-        return (acpi_handle)ret;
+        if (!context->ret) {
+                /* This is the first matching object.  Save its handle. */
+                context->ret = handle;
+                return AE_OK;
+        }
+        /*
+         * There is more than one matching object with the same _ADR value.
+         * That really is unexpected, so we are kind of beyond the scope of the
+         * spec here.  We have to choose which one to return, though.
+         *
+         * First, check if the previously found object is good enough and return
+         * its handle if so.  Second, check the same for the object that we've
+         * just found.
+         */
+        if (!context->ret_checked) {
+                if (acpi_extra_checks_passed(context->ret, context->is_bridge))
+                        return AE_CTRL_TERMINATE;
+                else
+                        context->ret_checked = true;
+        }
+        if (acpi_extra_checks_passed(handle, context->is_bridge)) {
+                context->ret = handle;
+                return AE_CTRL_TERMINATE;
+        }
+        return AE_OK;
+}
+
+acpi_handle acpi_find_child(acpi_handle parent, u64 addr, bool is_bridge)
+{
+        if (parent) {
+                struct find_child_context context = {
+                        .addr = addr,
+                        .is_bridge = is_bridge,
+                };
+
+                acpi_walk_namespace(ACPI_TYPE_DEVICE, parent, 1, do_find_child,
+                                    NULL, &context, NULL);
+                return context.ret;
+        }
+        return NULL;
 }
-EXPORT_SYMBOL(acpi_get_child);
+EXPORT_SYMBOL_GPL(acpi_find_child);
 
 int acpi_bind_one(struct device *dev, acpi_handle handle)
 {
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index dbdc5f7e2b29..01e264fb50e0 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -317,13 +317,20 @@ void acpi_pci_remove_bus(struct pci_bus *bus)
 /* ACPI bus type */
 static int acpi_pci_find_device(struct device *dev, acpi_handle *handle)
 {
-        struct pci_dev * pci_dev;
-        u64     addr;
+        struct pci_dev *pci_dev = to_pci_dev(dev);
+        bool is_bridge;
+        u64 addr;
 
-        pci_dev = to_pci_dev(dev);
+        /*
+         * pci_is_bridge() is not suitable here, because pci_dev->subordinate
+         * is set only after acpi_pci_find_device() has been called for the
+         * given device.
+         */
+        is_bridge = pci_dev->hdr_type == PCI_HEADER_TYPE_BRIDGE
+                        || pci_dev->hdr_type == PCI_HEADER_TYPE_CARDBUS;
         /* Please ref to ACPI spec for the syntax of _ADR */
         addr = (PCI_SLOT(pci_dev->devfn) << 16) | PCI_FUNC(pci_dev->devfn);
-        *handle = acpi_get_child(DEVICE_ACPI_HANDLE(dev->parent), addr);
+        *handle = acpi_find_child(ACPI_HANDLE(dev->parent), addr, is_bridge);
         if (!*handle)
                 return -ENODEV;
         return 0;
diff --git a/include/acpi/acpi_bus.h b/include/acpi/acpi_bus.h
index 5026aaa35133..94383a70c1a3 100644
--- a/include/acpi/acpi_bus.h
+++ b/include/acpi/acpi_bus.h
@@ -441,7 +441,11 @@ struct acpi_pci_root {
 };
 
 /* helper */
-acpi_handle acpi_get_child(acpi_handle, u64);
+acpi_handle acpi_find_child(acpi_handle, u64, bool);
+static inline acpi_handle acpi_get_child(acpi_handle handle, u64 addr)
+{
+        return acpi_find_child(handle, addr, false);
+}
 int acpi_is_root_bridge(acpi_handle);
 struct acpi_pci_root *acpi_pci_find_root(acpi_handle handle);
 #define DEVICE_ACPI_HANDLE(dev) ((acpi_handle)ACPI_HANDLE(dev))