[SeaBIOS] [Qemu-devel] [PATCH 0/3] switch to seavgabios

[Kevin O'Connor]

On Wed, Apr 18, 2012 at 10:45:06PM +0400, malc wrote:
> On Wed, 18 Apr 2012, Gerd Hoffmann wrote:
> > > We talked with malc briefly on irc yesterday, and this is what
> > > he gave me:
> > > 
> > > http://cvs.savannah.gnu.org/viewvc/vgabios/vbe.c?root=vgabios&r1=1.47&r2=1.48
> > > 
> > > this is not the test case but the missing support he's referring to.
> > > 
> > > It appears the patch implements just 2 functions which both just does
> > > int10,
> > 
> > It isn't that simple.  Just invoking int10 from protected mode isn't
> > guaranteed to have the desired effect.  It certainly wouldn't work for
> > linux vesafb panning.  It might work for dos extenders, they might have
> > the idt entry for int10 and other bios interrupts setup accordingly to
> > do a real-mode -> bios call -> protected mode transition to simplify
> > porting dos code to the 32bit extender.  But even for that use case it
> > is IMHO pointless as the reason to have a 32bit interface is to avoid
> > the expensive real mode switch in the first place ...
> 
> I needed DOS to work and it did, for me, in turn, linux vesafb is 
> pointless.

One can't issue "int 0x10" in 32bit mode under DOS and expect it to do
anything reasonable.  It may have worked for your particular
application, but it is just as likely to crash the machine with the
next application.

-Kevin