help! (much shorter)

[John Gilmore]

You can't assign an absolute address to a piece of text or data that
comes out of the C compiler.  You can make an absolute address look
like a struct (or other variable), then do a structure assignment
at runtime to initialize it if you want.  For example:

#define	DISKCTLR	(*(struct diskregs *)0xFFF304)
struct diskregs diskinit = {...};

	DISKCTLR = diskinit;
	DISKCTLR.command = DISK_RESET;
	...

Note that in the structure assignment, you can't control the ordering
of the storage references, so if it's an I/O device (not real memory),
you're probably better off doing it by hand.  Most devices are finicky
about what registers you write in what order anyway.