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

[Kevin O'Connor]

On Mon, Sep 11, 2017 at 12:33:24PM +0200, Gerd Hoffmann wrote:
> On Fri, 2017-09-08 at 14:53 -0400, Kevin O'Connor wrote:
> > On Fri, Sep 08, 2017 at 08:18:27AM +0200, Gerd Hoffmann wrote:
> > > Allows to run the serial console in parallel with a vga display.
> > > Output will show up on both vga and serial line.
> > > Input will be accepted from both keyboard and serial line.
> > 
> > [...]
> > > +        SET_LOW(sercon_enable, (mode == 0x03));
> > 
> > [...]
> > > +        // sercon disabled - verify not 0x03 modeset and otherwise
> > > exit
> > > +3:      popl %eax
> > > +        cmpw $0x0003, %ax
> > > +        jne 5f
> > 
> > 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.)

-Kevin