Re: [PATCH] pci_alloc_consistent in an interrupt context

On Fri, Jun 14, 2002 at 07:59:30AM -0700, Tom Rini wrote:

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My only concern is that are things still consistent on non consistent
procs?

Absolutely - no change to the code path at all on non cache coherent
processors.

So kmalloc/kfree are equivilent to __get_free_pages/free_pages ?

Read that again: on *non* cache coherent processors the code path is
the same.  kmalloc() vs. __get_free_pages() is a problem for
processors which *are* cache coherent.

Yes.  And there's 2 things here which I'm wondering about:
(a) Why do we call __get_fre_pages/free_pages now on coherent procs?
Can we really just call something else and have it work?

Possibly not (though I'm not sure kmalloc() wouldn't work), which is
why my last patch reverted to using __get_free_pages()/free_pages().
But the only problem with kmalloc() is the page-alignment requirements
specified in DMA-mapping.txt, not the actual consistency/coherence.

(b) Is it really a good idea to have a function called
'consistent_alloc()' which doesn't actually do that, for the sake of
removing 2 ifdefs?

As paulus already pointer out, it *does* actually do that.  Normal
memory is consistent on cache coherent processsors - that's what cache
coherent means.

--
David Gibson			| For every complex problem there is a
david@gibson.dropbear.id.au	| solution which is simple, neat and
				| wrong.  -- H.L. Mencken
http://www.ozlabs.org/people/dgibson

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