🚀 go-pugleaf

I hope somebody out there can help me with a problem that's driving
me crazy.

I'm trying to write a program that operates on units managed by
trackdisk.device (ie, floppy disks).  Part of the command line would
specify which drive(s) to operate on.  For the user's convenience I
want to allow names like DF0:, WorkBench:, SYS:, etc. In other words,
the user may specify an actual drive name, a volume that's in a disk drive,
or even an assign to a directory on a floppy, and my program should 
correctly determine which drive to act on.

SOOO...I have to make sure, once I've "dereferenced" the given name to
an actual device like DF0:, RAM:, or whatever, that the referenced drive
is actually controlled by trackdisk.device, without hard-coding names
like DF0: into the program--for instance, if the user mounted DF0: and
DF1: as A: and B:.

My problem is that for one solid week now I've been unable to find one
shred of a way to see what driver is controlling what device.  I can
follow the exec list of devices to find trackdisk.device, no problem.
I can follow the device list (SER:, PRT:, et al) to find DFx:, no
problem.  But no way to determine "trackdisk.device controls these
devices" or "this device is controlled by trackdisk.device".

My last good idea was to open trackdisk.device and extract the MsgPortPtr
from the initialized ioRequest structure, with the intent of comparing
it to the MsgPortPtr in the device entry for DF0:.  But The MsgPortPtr
from trackdisk.device was null, a value deliberately written there by
opendevice().  (How can this be right?  Once you open a device you're
supposed to be able to send it messages, no?)

Any help would be appreciated...

Kenneth Herron