[PATCH 2/3 v2] Do not use acpi_device to find pci root bridge in _init code.

[Tang Chen]

When the kernel is being initialized, and some hardwares are not added
to system, there won't be acpi_device structs for these devices. But
acpi_is_root_bridge() depends on acpi_device struct. As a result, all
the not-added root bridge will not be judged as a root bridge in
find_root_bridges(). And further more, no handle_hotplug_event_root()
notifier will be installed for them.

This patch introduces a new api to find all root bridges in system by
getting HID directly from ACPI namespace, not depending on acpi_device
struct.

Signed-off-by: Tang Chen <tangchen@xxxxxxxxxxxxxx>
Signed-off-by: Liu Jiang <jiang.liu@xxxxxxxxxx>
---
 drivers/acpi/pci_root.c |   19 +++++++++++--------
 1 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 6151d83..582eb11 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -129,20 +129,23 @@ EXPORT_SYMBOL_GPL(acpi_get_pci_rootbridge_handle);
  * acpi_is_root_bridge - determine whether an ACPI CA node is a PCI root bridge
  * @handle - the ACPI CA node in question.
  *
- * Note: we could make this API take a struct acpi_device * instead, but
- * for now, it's more convenient to operate on an acpi_handle.
+ * Note: If a device is not added to the system yet, there won't be an
+ * acpi_device struct for it. So do not get HID and CID from acpi_device,
+ * get them from ACPI namespace directly.
  */
 int acpi_is_root_bridge(acpi_handle handle)
 {
-	int ret;
-	struct acpi_device *device;
+	struct acpi_device_info *info;
+	acpi_status status;
 
-	ret = acpi_bus_get_device(handle, &device);
-	if (ret)
+	status = acpi_get_object_info(handle, &info);
+	if (ACPI_FAILURE(status)) {
+		printk(KERN_ERR PREFIX "%s: Error reading"
+				       "device info\n", __func__);
 		return 0;
+	}
 
-	ret = acpi_match_device_ids(device, root_device_ids);
-	if (ret)
+	if (acpi_match_object_info_ids(info, root_device_ids))
 		return 0;
 	else
 		return 1;
-- 
1.7.1

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