ACPICA: Namespace: Change namespace override to avoid node deletion

ACPICA commit c0ce529e1fbb8ec47d2522a3aa10f3ab77e16e41

There is no reference counting implemented for struct acpi_namespace_node, so it
is currently not removable during runtime.
This patch changes the namespace override code to keep the old
struct acpi_namespace_node undeleted so that the override mechanism can happen
during runtime. Bob Moore.

Link: https://github.com/acpica/acpica/commit/c0ce529e
Signed-off-by: Lv Zheng <lv.zheng@intel.com>
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/acpi/acpica/nssearch.c

@@ -331,13 +331,28 @@ acpi_ns_search_and_enter(u32 target_name,
 
 			/*
 			 * If the namespace override feature is enabled for this node,
-			 * delete any existing node. This can only happen during the
-			 * boot stage, thus it is safe to remove the node here.
+			 * delete any existing attached sub-object and make the node
+			 * look like a new node that is owned by the override table.
 			 */
 			if (flags & ACPI_NS_OVERRIDE_IF_FOUND) {
+				ACPI_DEBUG_PRINT((ACPI_DB_NAMES,
+						  "Namespace override: %4.4s pass %u type %X Owner %X\n",
+						  ACPI_CAST_PTR(char,
+								&target_name),
+						  interpreter_mode,
+						  (*return_node)->type,
+						  walk_state->owner_id));
+
 				acpi_ns_delete_children(*return_node);
-				acpi_ns_remove_node(*return_node);
-				*return_node = ACPI_ENTRY_NOT_FOUND;
+				if (acpi_gbl_runtime_namespace_override) {
+					acpi_ut_remove_reference((*return_node)->object);
+					(*return_node)->object = NULL;
+					(*return_node)->owner_id =
+					    walk_state->owner_id;
+				} else {
+					acpi_ns_remove_node(*return_node);
+					*return_node = ACPI_ENTRY_NOT_FOUND;
+				}
 			}
 
 			/* Return an error if we don't expect to find the object */

include/acpi/acpixf.h

@@ -228,6 +228,11 @@ ACPI_INIT_GLOBAL(u8, acpi_gbl_disable_auto_repair, FALSE);
  */
 ACPI_INIT_GLOBAL(u8, acpi_gbl_disable_ssdt_table_install, FALSE);
 
+/*
+ * Optionally enable runtime namespace override.
+ */
+ACPI_INIT_GLOBAL(u8, acpi_gbl_runtime_namespace_override, TRUE);
+
 /*
  * We keep track of the latest version of Windows that has been requested by
  * the BIOS. ACPI 5.0.