Re: [Linux-fbdev-devel] [PATCH] FBDev: vga16fb port

Sven Luther (luther@dpt-info.u-strasbg.fr)
Thu, 5 Dec 2002 19:03:14 +0100


On Thu, Dec 05, 2002 at 05:35:56PM +0000, James Simmons wrote:
>
> > If X is running in native mode then it has to save the register state.
> > Otherwise you cannot switch to a console. If X is running on top of
> > fbdev, then state restore/saves are done using fb_set_var and
> > fb_get_var. The registers are not touched, that's the purpose of fbdev.
> >
> > If you are running vgacon, fbdev, and native X, then yes, fbdev and X
> > has to do a save of their initial state.
>
> Not really. When X closes /dev/fb then fb_release is called which if the

That supposes X is fbdev aware (either using the fbdev driver or the
UseFBDev option), right ? What if X knows nothing about fbdev, it will
try restoring stuff as if it was in text mode.

> driver supports it will switch back to text mode. The exception is
> firmware based fbdev drivers like vesafb and offb.
>
> > > Does this also apply to vesafb ?
> > Not too sure about this. vesa requires real-mode initialization. Either
> > you do this at boot time, or fake a real-mode environment like what X
> > does.
>
> X has to reset the vidoe hardware back to the state that matches what the
> VESA mode was. Other wise it will mess you your system.
>
> P.S
>
> X on VESA fb always foobars my system when I exit X.

With which driver ? (i am happily running the vesa X driver on top of
vesafb without problems).

Friendly,

Sven Luther

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