Re: Prevent duplicate bus_space_map for TURBOchannel?

[Martin Husemann <martin%duskware.de@localhost>]

On Wed, May 04, 2016 at 07:18:13AM +0200, Felix Deichmann wrote:
> 2016-05-04 0:26 GMT+02:00 David Brownlee <abs%netbsd.org@localhost>:
> >> Trying to use a TC driver under VAX, I hit the point where a "duplicate"
> >> bus_space_map is necessary/performed: The generic TC stuff in tc.c,
> >> especially tc_checkslot(), wants to access memory space by pointers and
> >> "linearly", so for VAX TC, I must map physical space before (which is the
> >> same as calling bus_space_map), for example in tc_vsbus.c before calling
> >> tcattach().
> >> The TC device drivers attached by tc(4) again will call bus_space_map, which
> >> can lead to multiple allocations of the same region.
> >>
> >> [...]
> >
> > You might want to ask on one of the more general tech-kern@ or similar
> > list - as the specific concepts are probably not VAX or even
> > TURBOchannel specific :)
> 
> True, but as the other platforms seem to work like that and a change
> would be needed for VAX only, I hoped to get some ideas here first. On
> to tech-kern@ then.
> 
> Felix

You could create a special tc@vs-bus_space that maps the vs space upfront and
submaps part of that to tc-callers (but I have not looked at the vax bus space
implementation, so this might be more tricky than it looks)

Martin