[Week 7] Import the Xen grant-table bus_dma(9) handlers from OpenBSD

[Pratyush Yadav]

Hi,

At this point, the Xen-specific bus_dma(9) implementation is nearly
complete, with some minor fixes and additions required. So this last
week I went through the blkfront driver, so I can understand how it
works before starting to convert it to use the xen busdma.

That itself raised the question, how would a driver use the xen busdma
implementation, instead of the default implementation? After some help
from Roger, I modified xenpv.c to return the new implementation's tag
when a driver calls its bus_get_dma_tag(). Functionality to
"bootstrap" the dma tag was also added to busdma_xen.

This week, I will try to convert the blkfront driver to use the Xen's
busdma implementation.

You can check the code here [0].

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 [1].



[0] https://pratyushgsoc.blogspot.com/
[1] https://github.com/prati0100/freebsd/tree/master

--
Regards,
Pratyush Yadav