PCI Express and drivers

[Christopher Bowman]

I have a Xilinx PCI Express board that has an on board PCIe interface
macro.  I intend to have an address space with memory and another with my
devices control registers.  I wish to program this board under FreeBSD.  It
would seem to me that the way to do this would be to write a driver that
would allow me to map these two address spaces into a user process which
could then directly interact with the device.  In my case my board doesn't
really support multiple users, and it doesn't really seem to make sense to
me to put a lot of code in the kernel to create some sort of interface to
allow multiple processes to interact with my device via some sort of syscall
which would impose a lot of overhead in any case.  By mapping the address
ranges into a user process I can write user programs to drive the board
without having to recompile and reboot the kernel each time I make a change,
plus if I do something stupid and crash my user space process it shouldn't
bring down the whole kernel.  Am I thinking about this wrong?  Is there some
place I can go to read up on what I should be doing?  If I am thinking about
this correctly, then how does one map device memory into a user space
process?  How does one make sure that only one process has such a mapping?
Thanks
Christopher