But there is one difference: Now 

 cat /proc/acpi/asus/lcd

gives "1" (and no dmesg error message) and echoing values into it is
accepted without trouble. Unfortunately, the display remains dark. 

When booting with kernel option acpi_sleep=s3_bios, the background
light for the display comes on, but the display shows nothing.

If there is any more information I can provide, please let me know.

Regards,
Georg

-- 
Georg C. F. Greve                                       <greve-mXXj517/zsQ@public.gmane.org>
Free Software Foundation Europe	                 (http://fsfeurope.org)
Brave GNU World	                           (http://brave-gnu-world.org)