Re: FBdev remains in unusable state

From: Petr Vandrovec (
Date: Thu Dec 13 2001 - 12:02:28 EST

On 13 Dec 01 at 14:29, Pozsar Balazs wrote:
> On Thu, 13 Dec 2001, David Woodhouse wrote:
> >
> > said:
> > > Documentation/fb/vesafb.txt, X11 paragraph, last sentence:
> > > -------8<-----
> > > The X-Server must restore the video mode correctly, else you end up
> > > with a broken console (and vesafb cannot do anything about this).
> > > -------8<-----
> >
> > This isn't strictly true. We could just call the VESA BIOS to set it up
> > again for us. The 'vesa' XFree86 driver manages to do this perfectly well
> > from userspace, even.
> Then why not include this set up code into vesafb?

As it requires userspace, complete realmode 16bit DOS environment, it
should not live in kernel (due to being 16bit code, and requiring its
own mm). There was some patch which used protected mode VESA services
to set videomode, but as nobody uses these services, BIOSes either do
not provide them at all, or services provided are buggy and unusable.

If VESA BIOS virtualization it is something like (debian) 'read-edid'
package does - then please no. It prints dozens of messages to screen
for about 2 minutes on Matrox hardware, and if you switch consoles
during that, CRTC setting is hopelessly damaged and only starting X
brings picture back to you. And it does not read any EDID, of course...
                                            Petr Vandrovec
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This archive was generated by hypermail 2b29 : Sat Dec 15 2001 - 21:00:26 EST