Re: [PATCH v3 5/6] hppa: Add emulation of Artist graphics

[Sven Schnelle]

Hi Mark,

On Sat, Oct 26, 2019 at 10:35:20AM +0100, Mark Cave-Ayland wrote:

> > However, the VRAM in Artist is not really exposed to the Host. Instead,
> > there's the Chipset inbetween that can do byte swapping (Colormap is LE,
> > VRAM is BE) and Bit-to-Byte/Word/Dword conversion. For example you could
> > write 0x55 into that VRAM region, and the chipset would expand that to
> > VRAM Bytes: 00 01 00 01 00 01 00 01. And to make it even worse emulation
> > wise it can also do different encodings for Read or Write accesses, and
> > mask out certain bits of the data. So after trying to convert it to the
> > "dirty bitmap" API i decided to just leave it as it is. The CPU load
> > used by the display update code is usually < 1%, so it's ok for me.
> 
> Wow that sounds that some interesting hardware(!). Does it make sense to 
> model the
> behaviour of the chipset separately using a proxy MemoryRegion similar to 
> virtio i.e.
> introduce an intermediate IO MemoryRegion that does the swapping and then 
> forward it
> onto the VRAM MemoryRegion?

Thanks for the pointer, i'll check whether that would work. For now i
think i'll remove the Artist patch from the series, so we can apply the
other patches, and i'll re-submit Artist when it's done. I guess the
rewrite to use a MemRegion is a bit bigger. But i would to get the other
patches in especially the LASI Stuff as both Helge and i have a lot of
stuff depending on that.

Regards
Sven