There is a sample (skeleton) device driver in the RKM, though I recently
found out that the Addison Wesley versions of these books are missing some
appendices. You may need to look in a 1.2 version from CBM. Someone also
posted a RAMdisk driver to Usenet a while back, which was basically an
enhancement of the skeleton driver in the RKM. If I can find it, I'll send
it on up.
Meanwhile, try the include files for sample device drivers. They are very
similar to libraries, and have the same structure. All contain Open, Close,
and Expunge routines, which are pretty standard. After that, you will need
to ass (in a jump table) all the standard commands, BeginIO, Abort, Flush,
etc.. and then you can optionally add any sort of additional commands you
want. Another include file to check might be the exec/io one.