Geert Uytterhoeven geert at linux-m68k.org
Thu Mar 18 15:18:35 GMT 2004

On Thu, 18 Mar 2004, Matthew Wilcox wrote:
> On Thu, Mar 18, 2004 at 11:50:48AM +0100, Richard Zidlicky wrote:
> > so far, every time I stumbled over a readl in a driver it was a missing
> It's perfectly legal to ioremap() ISA memory and call readl() on it.
> If you don't believe me, see Linus' words on the matter:
> --- begin quopte from Documentation/IO-mapping.txt ---
> There is a completely different type of memory too, and that's the "shared
> memory" on the PCI or ISA bus. That's generally not RAM (although in the case
> of a video graphics card it can be normal DRAM that is just used for a frame
> buffer), but can be things like a packet buffer in a network card etc.
> This memory is called "PCI memory" or "shared memory" or "IO memory" or
> whatever, and there is only one way to access it: the readb/writeb and
> related functions.
> --- end quote ---
> (ok, this document isn't quite up to date, but this is the clear intention
> from reading the rest of the file).

But on non-PC, ISA memory space is not always a subset of PCI memory space,
while ISA I/O space is always a subset of PCI I/O space.



Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
							    -- Linus Torvalds

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