This was scheduled to be removed in 2012 by:

 commit 69c86373
 Author: florian@mickler.org <florian@mickler.org>
 Date:   Wed Feb 24 12:05:16 2010 +0100

     Document the rfkill sysfs ABI

     This moves sysfs ABI info from Documentation/rfkill.txt to the
     ABI subfolder and reformats it.

     This also schedules the deprecated sysfs parts to be removed in
     2012 (claim file) and 2014 (state file).
Signed-off-by: Florian Mickler <florian@mickler.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
Signed-off-by: João Paulo Rechi Vita <jprvita@endlessm.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>