I think you are right, the option fails due to missing "--yes-i-know-what-i-am-doing" flag.
Also hdparm gives a scary warning like: Use of -m is VERY DANGEROUS. Only the old IDE drivers work correctly with -m with kernels up to at least 2.6.29. libata drives may fail and get hung if you set this flag. Please supply the --yes-i-know-what-i-am-doing flag if you really want this. Program aborted. If you still need this functionality could you please try to fix /lib/hdparm/hdparm-functions script by adding code parsing "yes-i-know-what-i-am-doing" config option from /etc/hdparm.conf and if it works please send me a patch.
