libpciaccess and /dev/pci changes

[Michael <macallan%netbsd.org@localhost>]

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Hello,

I just committed the following changes:
- - add mmap() support to /dev/pci* ( enable it with options  
PCI_ALLOW_MMAP ) so userland has a way to map PCI devices at their bus  
addresses in a MI way instead of having to figure out where in the  
CPU's address space the PCI buses are
- - teach libpciaccess to dig through all /dev/pci* nodes in order to  
find all PCI devices on all buses and keep track of which file  
descriptor to use when mapping them - that way it also finds devices  
not visible through pci0 and has a way to map them.

With this Xorg should be able to use any PCI graphics device on any  
hardware, no matter if it's the console or not. So far I only tested  
it on my U60 which successfully used an XVR-100 ( an RV100 with Sun  
firmware ) in the 66MHz slot as secondary head, along with an ffb with  
the ffb being the console.

Things left to do:
- - find out how lipciaccess is supposed to deal with multiple IO spaces
- - fix ROM handling ( I didn't touch it so it still won't work on  
sparc64 for example )
- - cleanup

So far pcimmap() relies on the underlying bus_space_mmap() methods to  
enforce limits, especially on architectures where RAM overlaps PCI  
space. We should not allow anyone to map system memory through /dev/ 
pci. These limits are machine dependent so we can't do much about them  
in pcimmap(). Otherwise, we could check every mmap() request against  
all known BARs on the same bus and reject everything that's not  
covered by one.

have fun
Michael

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