sdmmc question.

[Phil Nelson <phil%netbsd.org@localhost>]

Hello,

   I'm working with a student to get NetBSD working on the SiFive
HiFive Unleashed board.  I know this is no longer being made, but
we have one.  He has the kernel running on the board until it wants
to mount root.  We want to get a sd driver working.  The issue
is that the sd device is on the spi bus on that hardware and sdmmc
doesn't work on the spi bus.

   We want to figure out how to connect the sdmmc to the spi bus.
We have tried a number of things in the config framework to get
sdmmc connected, but we don't know the internals of config well
enough and we have not found any prior work that will help us
get that done.

   Can anyone help us with the config framework and what is needed
to get sdmmc to talk to the spi bus?

   I'm presuming that we'll need something in the dev/spi/files.spi,
but haven't figured out what to say to get it to work.   And I'm
assuming there is a .c file that needs to implement the interface
between the sdmmc and the spi, but I'm not sure.   Do we need
something in another place?  

   Pointers to examples and/or documentation would be appreciated.

   Thanks.

--Phil