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Re: Booting arguments for NetBSD under qemu


On Wed, 23 Apr 2014 23:41:33 +0100
David Brownlee <> wrote:

> My question was more "why does NetBSD try to attach tcx0 on a machine
> with serial console  and genfb on the same machine with graphical
> console (albeit an emulated qemu machine). Should it not be trying to
> attach tcx in box cases?

Because tcx was never updated to return a match score higher than 1.
I'll fix that in a minute.
Frankly I'm surprised that people actually use genfb at sbus, given its
lack of colour map control ( thanks to OBP < 3 not having a standard
method to do it... ) ;)

> >> >> So an immediate workaround to enable running NetBSD-6.x would be to
> >> >> update to qemu-2.0.0 and use "-vga cg3", meanwhile someone can have a
> >> >> poke at NetBSD and see why -nographic and emulated tcx have issues...
> >> >> :)
> >> >
> >> > See above. A proper workaround would be to either add the missing bits
> >> > to qemu or find a way for our tcx driver to detect qemu and skip the
> >> > hardware that's not actually emulated.
> >>
> >> Would the output of "ofctl -p" give any clues (attached). This is from
> >> a "not -nographic" run from a HEAD kernel.
> >
> > Actually the diff between "-nographics" and "not -nographics" would be more 
> > interesting.
> That we can do. The "-nographics" case is with a kernel compiled without tcx0:
> -
> -
> Thats... clever - the only difference to the tcx properties in the
> -nographics case is that it is missing 'address'

And that matches real OBP / OF - no need for the firmware to map the
framebuffer if it isn't going to scribble into it.
So qemu doesn't emulate a complete tcx in the -nographics case but it
doesn't really tell us. As a workaround I could check
for /packages/grubfs-files and skip tcx if that node is present and tcx
isn't the console. Looks more like a bug in qemu though.

have fun

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