[SeaBIOS] [PATCH 5/6] sercon: split-output implementation

[Kevin O'Connor]

On Tue, Sep 12, 2017 at 08:25:44AM +0200, Gerd Hoffmann wrote:
>   Hi,
> 
> > > > Minor note - I realized after I sent my last patch that doing:
> > > > 
> > > >     SET_LOW(sercon_enable, (mode <= 0x07));
> > > 
> > > I don't think so.  0,1,2,3,7 are text modes, but 4,5,6 not.
> > 
> > It's safe to enter the C code on 4,5,6 though.  Also, I don't think
> > it
> > was unusual to write text while in cga mode.  (CGA support isn't a
> > priority though.)
> 
> Oh.  So the char write int10h calls work in cga mode too?

Yes.

On SeaVGABIOS, text writing now works in all graphic modes, though not
all vgabios support that.  The original bochs vgabios didn't support
it in "direct" or "packed" modes, and I think it was broken for years
in planar mode.  So, it's rare for text writing to be seen in any mode
above 7.  (It's also rare for anything to go into cga mode today, but
for ancient programs, it would not have been unusual to write out text
in cga mode.)

-Kevin