provide more common DMA API functions V2

[Christoph Hellwig]

On Mon, Aug 17, 2015 at 10:45:52PM -0700, Andrew Morton wrote:
> > > 
> > > I'll merge these 5 patches for 4.3.  That means I'll release them into
> > > linux-next after 4.2 is released.
> > 
> > So you only add for-4.3 code to -next after 4.2 is odd?  Isn't thast the
> > wrong way around?
> 
> Linus will be releasing 4.2 in 1-2 weeks and until then, linux-next is
> supposed to contain only 4.2 material.  Once 4.2 is released,
> linux-next is open for 4.3 material.

Hmm, I'm pretty sure there's tons of 4.3 material in linux-next at the
moment, at least I got merge warning messages from Stephen about
some yesterday.