Hello,
after upgrading kernel from 2.6.21.5 to 2.6.22-rc6 i got following error with smartctl:

# /usr/sbin/smartctl -a /dev/sda -d ata
smartctl version 5.37 [i686-suse-linux-gnu] Copyright (C) 2002-6 Bruce Allen
Home page is http://smartmontools.sourceforge.net/

=== START OF INFORMATION SECTION ===
Model Family:     Hitachi Deskstar T7K250 series
Device Model:     HDT722516DLA380
Serial Number:    VDN71BTCDEASDG
Firmware Version: V43OA91A
User Capacity:    164,696,555,520 bytes
Device is:        In smartctl database [for details use: -P show]
ATA Version is:   7
ATA Standard is:  ATA/ATAPI-7 T13 1532D revision 1
Local Time is:    Sun Jul  1 20:04:53 2007 CEST
SMART support is: Available - device has SMART capability.
SMART support is: Enabled

Error SMART Status command failed
Please get assistance from http://smartmontools.sourceforge.net/
Register values returned from SMART Status command are:
CMD=0x50
FR =0x00
NS =0x01
SC =0x00
CL =0x00
CH =0x00
SEL=0x00
A mandatory SMART command failed: exiting. To continue, add one or more '-T permissive' options.