Tried that, did not work. It seems the SCSI module is not loaded during boot
although its present in minirt.gz in /modules/scsi/aic7xxx.ko

How can I force loading that module?
gentoo a # lspci
01:07.0 SCSI storage controller: Adaptec AIC-7892A U160/m (rev 02)
gentoo a # cat /proc/scsi/aic7xxx/0
Adaptec AIC7xxx driver version: 7.0
Adaptec 29160 Ultra160 SCSI adapter
aic7892: Ultra160 Wide Channel A, SCSI Id=7, 32/253 SCBs