From: Marcus Sundberg <mackan@stacken.kth.se>
  To  : ggi-develop@eskimo.com
  Date: Wed, 18 Aug 1999 17:52:58 +0200

Re: kgicon C&T

Jon M. Taylor wrote:
> 
> On Tue, 17 Aug 1999, Marcus Sundberg wrote:
> 
> > James Simmons wrote:
> > >
> > > > >  Double buffering is not defined for fbdev :(
> > > >
> > > > But panning is, so ask for: yres_virtual == 2*yres when calling
> > > > FBIOPUT_VSCREENINFO, and use FBIOPAN_DISPLAY to flip between the
> > > > top half and the bottom half.  Right James ?
> > >
> > > Yes you can do that. What I was talking about where cards that do have a
> > > seperate buffer for double buffering.
> >
> > Never heard of such hardware. Any examples?
> 
>         Most new hardware supports explicit double/triple buffering, as
> opposed to the SetOrigin()-based SVGA-style double buffering.  The
> differences are minimal, and mostly involve the hardware taking care of
> automating buffer flips on vsync.

The fbdev API handles that already. This is what
#define FB_ACTIVATE_VBL        16       /* activate values on next vbl  */
is there for.

> The back buffer is still just another
> chunk of video memory, it just doesn't have to be physically continguous
> with the primary framebuffer anymore.

Fbdev has (limited) support for that too via ypanstep.

//Marcus
-- 
-------------------------------+------------------------------------
        Marcus Sundberg        | http://www.stacken.kth.se/~mackan
 Royal Institute of Technology |       Phone: +46 707 295404
       Stockholm, Sweden       |   E-Mail: mackan@stacken.kth.se