Re: [PATCH] dmatest: flush and invalidate destination bufferbefore DMA

[Atsushi Nemoto]

On Mon, 05 Jan 2009 18:29:56 -0700, Dan Williams <dan.j.williams@xxxxxxxxx> wrote:
> > Yes, MIPS and ARM do different thing on partial cache line.  But I
> > suppose this belongs to "implementation dependent" area of DMA API so
> > users of the API should not depend on it.  (Well, maybe I'm biased to
> > MIPS ;-))
> > In general, drivers must not put normal data and DMA buffer on same
> > cacheline anyway to avoid unexpected writeback and data loss.  So this
> > ambiguity is not a problem.  IMHO writeback of the partial line for
> > DMA_FROM_DEVICE just _hides_ abusing of the DMA API and potential data
> > loss.
> 
> Hmm... one implementation does the right thing in all cases.

Yes, with additional checking in generic path :-)

> The other silently allows data corruption unless each callsite that
> accidentally or purposely passes cacheline-unaligned buffers adds
> extra maintenance code.  Which implementation are you biased towards
> now? :-).

Hmm... this is generic DMA mapping API (or linux-arch) issue.  Let's
wait comments from arch maintainers.  Ralf ?

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