Sun-3 to Sun-4 Porting

[Jeff Butterworth]

I've been thrust into the unfortunate circumstance of having to modify a
device driver for a Matrox video frame grabber.  In front of me I've got a
technical description of the product that is at least a few months old.
The title says "Real-Time Imaging on Sun-3/Sun-4 Workstations".  That
underlined Sun-4 is why we purchased this frame grabber.  We have a
Sun-4/280 and need to use it in an ultrasound imaging project.  The
ultrasound data will be obtained as video input, so this board looked
great.

When we unpacked everything, we found a little note saying that the device
driver would only work on a Sun-3.  We called the company and were told
that they still didn't have the device driver ported to the Sun-4.  We are
now in the process of obtaining the source code from Matrox and will
attempt to port it ourselves.

I've barely even touched a device driver before.  I don't even know where
to start looking for things to fix in this code.  If there is anyone out
there that could give me some tips on the pertinent differences between
Sun-3's and Sun-4's, then it would help me *immensely*.

Please!  Any hints at all would be greatly appreciated!