[ACPI] CONFIG_ACPI_RELAXED_AML from 2.4

http://bugzilla.kernel.org/show_bug.cgi?id=1248

drivers/acpi/Kconfig

@@ -281,5 +281,17 @@ config ACPI_EFI
 	depends on IA64
 	default y
 
+config ACPI_RELAXED_AML
+	bool
+	depends on ACPI_INTERPRETER
+	depends on !IA64_SGI_SN
+	default n
+	help
+	  If you say `Y' here, the ACPI interpreter will relax its checking
+	  for valid AML and will ignore some AML mistakes, such as off-by-one
+	  errors in region sizes.  Some laptops may require this option.  In
+	  particular, many Toshiba laptops require this for correct operation
+	  of the AC module.
+
 endmenu
 

drivers/acpi/executer/exfldio.c

@@ -139,7 +139,41 @@ acpi_ex_setup_region (
 			field_datum_byte_offset, obj_desc->common_field.access_byte_width,
 			rgn_desc->region.node->name.ascii, rgn_desc->region.length));
 
-		return_ACPI_STATUS (AE_AML_REGION_LIMIT);
+		#ifdef CONFIG_ACPI_RELAXED_AML
+		{
+			/*
+			 * Allow access to the field if it is within the region size
+			 * rounded up to a multiple of the access byte width.  This
+			 * overcomes "off-by-one" programming errors in the AML often
+			 * found in Toshiba laptops.  These errors were allowed by
+			 * the Microsoft ASL compiler.
+			 */
+			u32 rounded_length = ACPI_ROUND_UP(rgn_desc->region.length,
+									obj_desc->common_field.access_byte_width);
+
+			if (rounded_length < (obj_desc->common_field.base_byte_offset
+						+ field_datum_byte_offset
+						+ obj_desc->common_field.access_byte_width)) {
+				return_ACPI_STATUS (AE_AML_REGION_LIMIT);
+			} else {
+				static int	warn_once = 1;
+				if (warn_once) {
+					// Could also associate a flag with each field, and
+					// warn once for each field.
+					ACPI_REPORT_WARNING((
+						"The ACPI AML in your computer contains errors, "
+						"please nag the manufacturer to correct it.\n"));
+					ACPI_REPORT_WARNING((
+						"Allowing relaxed access to fields; "
+						"turn on CONFIG_ACPI_DEBUG for details.\n"));
+					warn_once = 0;
+				}
+				return_ACPI_STATUS (AE_OK);
+			}
+		}
+		#else
+			return_ACPI_STATUS (AE_AML_REGION_LIMIT);
+		#endif
 	}
 
 	return_ACPI_STATUS (AE_OK);