Re: ZONE_DMA

[Jesse Barnes <jesse.barnes@intel.com>]

On Friday, September 22, 2006 11:08 am, Christoph Lameter wrote:
> On Fri, 22 Sep 2006, Jesse Barnes wrote:
> > Ok and right after I sent this my brain returned from vacation and I
> > remembered jejb's DMA allocation API.  It's powerful enough to cover
> > most driver use cases I think (users of GFP_DMA should probably be
> > converted), but for example block layer bounce buffering might need a
> > different interface as I see you've proposed in another mail.
>
> Could you dig that out and give us some refs or even better port that
> thing to a current mm tree?

Oh, it's already there in the tree, but obviously some drivers still need 
to be converted.  See Documentation/DMA-API.txt.  It's not PCI specific 
like the old PCI DMA interface (Documentation/DMA-mapping.txt) and 
provides a way for drivers to specify their addressing limitations 
(dma_supported and dma_set_mask), which allows the underlying architecture 
code to report a failure if necessary.

I think many of the examples I cited can be converted to use the DMA API, 
but block layer bounce buffering might need special treatment or perhaps a 
way to get at the underlying struct device for the associated request...

Jesse