[9fans] Floppy driver

[lucio@proxima.alt.za]

The following code:

print ("floppyrevive(%d): %lux - %lux\n", ++x, &fl, fl.d);
		/* reset controller and turn all motors off */
		splhi();
		fl.ncmd = 1;
		fl.cmd[0] = 0;
		outb(Pdor, 0);
		delay(10);
		outb(Pdor, Fintena|Fena);
		delay(10);
		spllo();
print ("floppyrevive(%d): %lux - %lux\n", ++x, &fl, fl.d);

from /sys/src/boot/pc/devfloppy.c:/^floppyrevive (I seem to recall)
reveals that fl.d changes value from a valid address to 0xffffffff.

Now, "fl" is the FController structure, defined in ..../devfloppy.h
(and in devfloppy.c, I removed the second declaration) and I really
cannot figure how one (or more) fields within that structure could
be affected by the operations between.

Also, this only occurs on an old 386/387 platform, with an add-on
ATA and floppy controller.  I have not seen the symptom on the
Pentium I first experimented with.  The symptom itself is obscure:
from trap.c: "exception/interrupt 12".

Clues, anyone?

++L