DVD-ROM problem with Freebsd 7

I'm debugging a problem with an Intel Bigby chipset and a DVD-ROM drive. We've swapped it out with a regular CD-ROM and have the same problem, so its likely not the drive. It gets probed as ATA_I82801IB_AH6.

The problem is that certain types of media don't work. Some work, some don't.   We're going to build a LINUX system to try to see if its the driver or some physical thing, but the media works on our other systems so it appears to be the driver.

In pouring over the drivers, I've noticed that the setmode function never seems to get called, and I'm wondering what the point of the setup variables are if they're never called. What should be the sequence of calls to properly set up the controller?

Barney