(written by Frank Neumann)
Some devices dislike being polled on LUNs (logical units) other than 0. What can happen here is that the SCSI bus just locks up because the device does not answer the inquiry. Quite a couple of drives have already been added to the blacklist of "bad" devices in the kernel, but there are probably more. If you discover this behavior on one of your SCSI devices, you might try adding it to the blacklist (in drivers/scsi/scsi.c) yourself or ask someone to do it for you if you are sure about it.
If you think you're adventurous and want to fix the kernel for a specific SCSI device yourself, here is what you could do. Note that these instructions are for the Amiga, but they apply in general to all systems:
Under AmigaOS, use the scsiutil command (available on Aminet) and its -i option to send an Inquiry command to that particular device. Write down its vendor identification, product identification and Product revision level. For instance, an Apple CD-300 CD-ROM drive might give (at the bottom) this output:
Vendor identification: SONY Product identification: CD-ROM CDU-8003A Product revision level: 1.9a
Now go into the kernel source tree and (under drivers/scsi/scsi.c) add your drive to the blacklist of drives that have problems (just search for "blacklist"). Recompile the kernel and try it out without the wd33c93= options you probably used so far.
If it works, you might want to send your change as a unified context diff (use "diff -u") to the Linux/m68k mailing list.