diff --git a/include/acpi/actypes.h b/include/acpi/actypes.h
index 66ceb12ebc63032a9f4af8a9da7db9ac04c83178..2939a6cd7fecbfc9ba2db8ef314593e8535b870a 100644
--- a/include/acpi/actypes.h
+++ b/include/acpi/actypes.h
@@ -528,11 +528,12 @@ typedef u64 acpi_integer;
 #define ACPI_MAKE_RSDP_SIG(dest)        (memcpy (ACPI_CAST_PTR (char, (dest)), ACPI_SIG_RSDP, 8))
 
 /*
- * Algorithm to obtain access bit width.
+ * Algorithm to obtain access bit or byte width.
  * Can be used with access_width of struct acpi_generic_address and access_size of
  * struct acpi_resource_generic_register.
  */
 #define ACPI_ACCESS_BIT_WIDTH(size)     (1 << ((size) + 2))
+#define ACPI_ACCESS_BYTE_WIDTH(size)    (1 << ((size) - 1))
 
 /*******************************************************************************
  *