[Qemu-devel] Re: [PATCH 0/2] pckbd improvements

[Blue Swirl]

On 5/16/10, Paolo Bonzini <address@hidden> wrote:
> On 05/15/2010 11:49 AM, Blue Swirl wrote:
>
> > In 2/2, A20 logic changes a bit but I doubt any guest would be broken
> > if A20 line written through I/O port 92 couldn't be read via i8042.
> > The reverse (write using i8042 and read port 92) will work.
> >
>
>  Why take the risk?

The alternative is to route a signal from port 92 to i8042. Or maybe
port 92 should belong to i8042, that could make things simpler but
then the port would appear on non-PC architectures as well.

But I doubt any OS would depend on such details, because the details
seem to be murky:
http://www.win.tue.nl/~aeb/linux/kbd/A20.html