From: Bob Moore <robert.moore@intel.com>
Date: Mon, 31 Dec 2012 00:05:33 +0000 (+0000)
Subject: ACPICA: Add root node optimization to internal get namespace node function.
X-Git-Tag: upstream/snapshot3+hdmi~5715^2~11^2~33
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=f8c9bfe461bb2923ae5d070f1ec0fb312825caad;p=platform%2Fadaptation%2Frenesas_rcar%2Frenesas_kernel.git

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 d2dfe61..596d4cc 100644
--- 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);