Re: [RFC] generic device DMA implementation

[Miles Bader <miles@lsi.nec.co.jp>]

James Bottomley <James.Bottomley@steeleye.com> writes:
> > How is the driver supposed to tell whether a given dma_addr_t value
> > represents consistent memory or not?  It seems like an
> > (arch-specific) `dma_addr_is_consistent' function is necessary, but
> > I couldn't see one in your patch.
> 
> If you have a machine that has both consistent and inconsistent blocks, you 
> need to encode that in dma_addr_t (which is a platform definable type).
> 
> The sync functions would just decode the type and either nop or perform the 
> sync.

My thinking was that a driver might want to do things like --

  if (dma_addr_is_consistent (some_funky_addr)) {
    do it quickly;
  } else
    do_it_the_slow_way (some_funky_addr);

in other words, something besides just calling the sync functions, in
the case where the memory was consistent.

-Miles
-- 
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