Re: PCI DAC DMA APIs

[David Miller <davem@davemloft.net>]

From: Christoph Hellwig <hch@infradead.org>
Date: Thu, 15 Mar 2007 19:18:34 +0000

> On Thu, Mar 15, 2007 at 12:38:13PM +0000, Jan Beulich wrote:
> > While the kernel headers provide for this, there don't appear to be any
> > in-tree users (which seems contrary to general Linux policies). Would there
> > be objections to remove all of these?
> 
> They should go away.  Having them in for more than five years without
> any users is almost a guarantee for bitrot.

Yes, probably we should get rid of them.

The idea wasn't sparc optimizations, it was for things like those
Dolphin clustering cards that essentially want to get at all of
physical memory from the PCI card.

The IOMMU is a limited resource, so at the expense of lack of
prefetching and write caching we provide a way to do unlimited DMA
mapping with 64-bit DAC addresses.

None of these drivers ever got integrated, so it's a total loss.

Someone will complain when we pull it out, but fsck them, they
had years to do something about this. :)