Re: Address spaces on a i386 - Getting Confused

Brian Gerst (bgerst@quark.vpplus.com)
Tue, 30 Mar 1999 08:35:01 -0500

Paul Sargent wrote:
> As far as I can see there are probably three distinct address spaces used
> (please correct me if I'm wrong)
> * Kernel space Virtual Addresses
> * User Space Virtual Addresses (1 address space per process)
> * Physical (Bus) addresses

Actually physical and bus addresses are not always identical. On the
i386 they are the same but on some other achitectures they are not. So
you also need phys_to_bus() (which is just an empty macro on the i386)
to return the real bus address which you can give to the card's DMA
controller.

--


				Brian Gerst


-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.rutgers.edu
Please read the FAQ at http://www.tux.org/lkml/