driver help for adaptec scsi controller model AHA-2940 Ultra

[Khalif]

hi i'm trying to locate a driver for AHA-2940 Ultra. this controller is install system which is running Red Linux 5 Enterprise version...issue,i'm unable see my Dat drive...when i run the "lspci i could see the controller but it shows as uknown device.
please help if there is any open source any where which could have the driver that particular controller.

thank you
Khalif