ACPICA: Comment update; no functional change

Add a usage note to InstallAddressSpaceHandler.
Signed-off-by: Bob Moore <robert.moore@intel.com>
Signed-off-by: Lin Ming <ming.m.lin@intel.com>
Signed-off-by: Len Brown <len.brown@intel.com>

drivers/acpi/acpica/evxfregn.c

@@ -64,6 +64,12 @@ ACPI_MODULE_NAME("evxfregn")
  *
  * DESCRIPTION: Install a handler for all op_regions of a given space_id.
  *
+ * NOTE: This function should only be called after acpi_enable_subsystem has
+ * been called. This is because any _REG methods associated with the Space ID
+ * are executed here, and these methods can only be safely executed after
+ * the default handlers have been installed and the hardware has been
+ * initialized (via acpi_enable_subsystem.)
+ *
  ******************************************************************************/
 acpi_status
 acpi_install_address_space_handler(acpi_handle device,