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SubjectRe: [linux-fbdev] fbdev 2.4.0 cleanups
On Thu, 16 Mar 2000, Russell King wrote:
> James A Simmons writes:
> > Okay lets consider this. Now some video cards use different apertures for
> > their video memory. What I mean the framebuffer location is different for
> > 8 bit (it's little endian) and 16 bit (big endian). Consider this.
> > You start your X server in 8 bit mode. Now it will have write access to
> > /dev/fb. Now you start some app which opens /dev/fb in read only mode and
^^^^^^^^
> > gets the current fix info. fix->smem_start will point to the little endian
> > aperture right. Now your X server has properly ALT whatever function keys
> > that do change the video mode. Since the X server has write access it can
> > change the modes. So now you switch to 16 bit color mode which means
> > fix->smem_start has changed to the big aperture. Your other app is still
> > writing to where the little endian aperture was which is the wrong place.

> Unless there has been a major change in X11, I don't think that's possible.
> I believe that the only thing that Alt +/- can do is change resolution, not
> colour depth.
>
> IIRC, colour depth requires a restart of the server and all applications.
>
> Please correct me if I'm wrong.

Yes, X can't change color depth without restarting.

But `some app' may be something that does support color depth changing (e.g.
plain fbset).

Gr{oetje,eeting}s,
Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds


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