ACPICA: Add root node optimization to internal get namespace node function.

Detect a request for the root node (a lone backslash) up front
before invoking a full namespace lookup.

Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

diff --git a/drivers/acpi/acpica/nsutils.c b/drivers/acpi/acpica/nsutils.c
index d2dfe61721811d528bc1a825b9c43df7486ab50b..596d4ccc963f32c7fe6ad484ca6a605c4ad61e06 100644 (file)
--- a/drivers/acpi/acpica/nsutils.c
+++ b/drivers/acpi/acpica/nsutils.c
@@ -671,6 +671,8 @@ acpi_ns_get_node(struct acpi_namespace_node *prefix_node,
 
        ACPI_FUNCTION_TRACE_PTR(ns_get_node, ACPI_CAST_PTR(char, pathname));
 
+       /* Simplest case is a null pathname */
+
        if (!pathname) {
                *return_node = prefix_node;
                if (!prefix_node) {
@@ -679,6 +681,13 @@ acpi_ns_get_node(struct acpi_namespace_node *prefix_node,
                return_ACPI_STATUS(AE_OK);
        }
 
+       /* Quick check for a reference to the root */
+
+       if (ACPI_IS_ROOT_PREFIX(pathname[0]) && (!pathname[1])) {
+               *return_node = acpi_gbl_root_node;
+               return_ACPI_STATUS(AE_OK);
+       }
+
        /* Convert path to internal representation */
 
        status = acpi_ns_internalize_name(pathname, &internal_path);