ACPICA: AcpiGetDevices: Eliminate unnecessary _STA calls

In the case where a specific _HID is requested, do not run _STA
until a _HID match is found. This eliminates potentially dozens
of _STA calls during a search for a particular device/HID.

Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

1 files changed, 33 insertions, 19 deletions

diff --git a/drivers/acpi/acpica/nsxfeval.c b/drivers/acpi/acpica/nsxfeval.c
index c5a5357c69e6..ebef8a7fd707 100644
--- a/drivers/acpi/acpica/nsxfeval.c
+++ b/drivers/acpi/acpica/nsxfeval.c
@@ -562,25 +562,20 @@ acpi_ns_get_device_callback(acpi_handle obj_handle,
                 return (AE_BAD_PARAMETER);
         }
 
-        /* Run _STA to determine if device is present */
-
-        status = acpi_ut_execute_STA(node, &flags);
-        if (ACPI_FAILURE(status)) {
-                return (AE_CTRL_DEPTH);
-        }
-
-        if (!(flags & ACPI_STA_DEVICE_PRESENT) &&
-            !(flags & ACPI_STA_DEVICE_FUNCTIONING)) {
-                /*
-                 * Don't examine the children of the device only when the
-                 * device is neither present nor functional. See ACPI spec,
-                 * description of _STA for more information.
-                 */
-                return (AE_CTRL_DEPTH);
-        }
-
-        /* Filter based on device HID & CID */
-
+        /*
+         * First, filter based on the device HID and CID.
+         *
+         * 01/2010: For this case where a specific HID is requested, we don't
+         * want to run _STA until we have an actual HID match. Thus, we will
+         * not unnecessarily execute _STA on devices for which the caller
+         * doesn't care about. Previously, _STA was executed unconditionally
+         * on all devices found here.
+         *
+         * A side-effect of this change is that now we will continue to search
+         * for a matching HID even under device trees where the parent device
+         * would have returned a _STA that indicates it is not present or
+         * not functioning (thus aborting the search on that branch).
+         */
         if (info->hid != NULL) {
                 status = acpi_ut_execute_HID(node, &hid);
                 if (status == AE_NOT_FOUND) {
@@ -620,6 +615,25 @@ acpi_ns_get_device_callback(acpi_handle obj_handle,
                 }
         }
 
+        /* Run _STA to determine if device is present */
+
+        status = acpi_ut_execute_STA(node, &flags);
+        if (ACPI_FAILURE(status)) {
+                return (AE_CTRL_DEPTH);
+        }
+
+        if (!(flags & ACPI_STA_DEVICE_PRESENT) &&
+            !(flags & ACPI_STA_DEVICE_FUNCTIONING)) {
+                /*
+                 * Don't examine the children of the device only when the
+                 * device is neither present nor functional. See ACPI spec,
+                 * description of _STA for more information.
+                 */
+                return (AE_CTRL_DEPTH);
+        }
+
+        /* We have a valid device, invoke the user function */
+
         status = info->user_function(obj_handle, nesting_level, info->context,
                                      return_value);
         return (status);