When I load st, I don't get any /dev/st0 device with 2.6.31.
linux> lsmod | grep st
st 31272 0
scsi_mod 136336 4 st,sg,libata,sd_mod
Might there be some other bug preventing st from detection the ATAPI tape drive?
Quite possibly - what does dmesg show when ata_piix is loaded ?