[Week 5] Import the Xen grant-table bus_dma(9) handlers from OpenBSD

[Pratyush Yadav]

Hi,

I refined my implementation of the xen-specific bus_dma(9) handlers,
with help from Roger Pau Monne.

I was allocating the grant references per DMA tag, and not per DMA
map. This was wrong. Roger pointed it out and I fixed it. It took a
lot of time because a large part of the code had to be refactored.
This was because I had to introduce a xen-specific DMA map which
contained the generic DMA map, along with some other stuff that was
needed. This meant that every method using a DMA map had to be
updated. A lot of careful changes had to be made.

Other than that, I made some minor fixes and improvements.

I expect I should have the bus_dma handlers ready, at least to some
extent, by the end of this week. I will also try to write some tests
if I get the time.

I maintain a blog on Blogger where I publish my progress every few
days. Check it out if you want more details on what I'm doing [0].


[0] http://pratyushgsoc.blogspot.in/2018/05/import-xen-grant-table-busdma9-handlers.html

-- 
Regards,
Pratyush Yadav