On Wed, Mar 08, 2006 at 05:04:51PM +0000, David Howells wrote:
> > [For information on bus mastering DMA and coherency please read ....]
> > sincee have a doc on this
>
> Documentation/pci.txt?
and:
Documentation/DMA-mapping.txt
Documentation/DMA-API.txt
>
> > The use of volatile generates poorer code and hides the serialization in
> > type declarations that may be far from the code.
>
> I'm not sure what you mean by that.
in foo.h
struct blah {
volatile int x; /* need serialization
}
2 million miles away
blah.x = 1;
blah.y = 4;
And you've no idea that its magically serialized due to a type declaration
in a header you've never read. Hence the "dont use volatile" rule
> > Is this true of IA-64 ??
>
> Are you referring to non-temporal loads and stores?
Yep. But Matthew answered that
> > Should clarify local ordering v SMP ordering for locks implied here.
>
> Do you mean explain what each sort of lock does?
spin_unlock ensures that local CPU writes before the lock are visible
to all processors before the lock is dropped but it has no effect on
I/O ordering. Just a need for clarity.
> > > + (*) inX(), outX():
> > > +
> > > + These are intended to talk to legacy i386 hardware using an
> > > alternate bus
> > > + addressing mode. They are synchronous as far as the x86 CPUs are
> >
> > Not really true. Lots of PCI devices use them. Need to talk about "I/O
> > space"
>
> Which bit is not really true?
The "legacy i386 hardware" bit. Many processors have an I/O space.
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