FC5, FC6 and RHEL5 require you to have "modules.alias" file on the driver disk.
The DD format has been changed from RHEL4 times.

FC5 has buggy DD support, it doesn't check for the required file "modules.alias",
and it also contains bogus checks for files it doesn't use at all.

FC6 and RHEL5 have working DD support for this new format.

see: https://bugzilla.redhat.com/bugzilla/show_bug.cgi?id=195899#c18

example of modules.alias:

alias pci:v00001077d00004022sv*sd*bc*sc*i* qla4xxx