Bugzilla Bug 185341

app-laptop/pbbuttonsd-0.8.1 installs a file /etc/power/pmcs-config containing
the following default initialisation parameters:

   performance_HDOptions="-p"
   custom_HDOptions="-p"
   powersave_HDOptions="-p"

These are used by /etc/power/scripts.d/hdsetup and passed as argument to
hdparm. The hdparm man page says for option "-p":

"Attempt to reprogram the IDE interface chipset for the specified PIO mode, or
attempt to auto-tune for the 'best' PIO mode supported by the drive. This
feature is supported in the kernel for only a few 'known' chipsets, and even
then the support is iffy at best. Some IDE chipsets are unable to alter the PIO
mode for a single drive, in which case this flag may cause the PIO mode for
*both* drives to be set. Many IDE chipsets support either fewer or more than
the standard six (0 to 5) PIO modes, so the exact speed setting that is
actually  implemented will vary by chipset/driver sophistication.
*Use*with*extreme*caution!* This feature includes zero protection for the
unwary, and an  unsuccessful outcome may result in
*severe*filesystem*corruption!*"

For the Intel PIIX/ICH driver in kernel 2.6.22, the effect of "hdparm -p" is
that DMA for the device is disabled.

In short, "-p" is an unsuitable and dangerous default and should be replaced by
the empty string. Users who want to tune their HD performance can still change
the pcms-config file or specify their options in /etc/conf.d/hdparm.

Okay, I reported this upstream and added a patch to portage.  Thanks.