Re: [Linux-fbdev-devel] Comments on fbgen.c and fbcon-accel

[Petr V. <VAN...@vc...>]

On  7 May 02 at 21:26, Antonino Daplas wrote:
> > And set_par() could do some optimizations based on a shadow map of the register
> > contents, also to avoid artefacts when switching to a different VC with the
> > same video timings. Like:
> > 
> >   write_reg(reg, val)
> >   {
> >       if (shadow[reg] != val) {
> >   shadow[reg] = val;
> >   hardware[reg] = val;
> >       }
> >   }

I was doing that long ago in matroxfb, and it simple does not work :-(
There is too many applications which programs video hardware directly.
So currently matroxfb always reprogram most of registers, and for
critical ones (PLL) it reads back value from hardware, and not from some
shadow area. Speed difference is invisible and reliability is much better.
                                                Best regards,
                                                    Petr Vandrovec
                                                    van...@vc...