[comp.unix.xenix] Questions about memory mapped device drivers

bill@ftp.COM (Bill Lampman) (06/16/88)

	I've been trying to write memory mapped device drivers for the
	Western Digital WD8003 and the Micom Interlan NI5210 ethernet
	cards on a pc clone. Is there something strange about how Xenix
	maps its memory, ie. are there some addresses that cannot be used
	by device drivers ? I've tried setting up the boards as described
	in the example video driver in the manual :

		#define	MEMSIZ	0x2000

		unsigned	sel;
		long		addr;
		faddr_t		board;

		addr = 0xd0000;

		sel = dscralloc();
		mmudescr(sel, addr, MEMSIZ-1, DSA_DATA);
		board = sotofar(sel, 0);

	I cannot access the memory on the boards no matter what I try.
	Do I have to "tell Xenix" in some way that there is memory here
	that wasn't there at system startup ?

	Thanks in advance for the help.

Bill

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