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SubjectRe: [linux-fbdev] fbdev 2.4.0 cleanups
On Tue, Mar 14, 2000 at 11:02:27AM -0500, James A Simmons wrote:
>
> > > Here is the main reasons why I have it so only one app can open /dev/fb at
> > > a time. Its called SMP. Consider two apps running at the same time both
> > > with /dev/fb opened. Problem:
> > >
> > > 1)
> > > Both apps mmap the MMIO region. Both program the accel engine at the
> > > same. Hey the card locks up.
> > >
> > > 2)
> > > DRI and fbdev MMIO region. DRI is using accel engine. Some app running
> > > from a xterm mmaps MMIO region then uses accel engine. The card locks up.
> > >
> > > 3)
> > > Someone runs fbset while the X server is using accel engine via /dev/fb
> > > or DRI. Card locks up. You should only change the mode when the accel
> > > engine is idle.
> > >
> > >
> > > Now do people agree with me that /dev/fb should only be opened once.
> >
> > Err, ...
> >
> > not, there is no reason i should not be able to change mode of Xfree-fbdev
> > whit fbset, not sure it will work, but still that is xfree who is broken.
>
> No the X server should change the modes. Their is also the problem of two
> apps trying to set the video mode at the same time. Broken apps shouldn't
> force the kernel to be broken.

Too, bad, ...

fbset has a nice interface i understand, while the Xserver offer no such
thing, appart from the limited ctr+alt+[+-] stuff.
>
> > But anyway, i don't agree with you, there is no reason that a lots of people
> > can open /dev/fb in read only mode, sure if some guys want to write to it at
> > the same time, it could cause problems, ...
>
> Security :) One of the goals is to allow anyone to run a app on /dev/fb.
> No more root.

I do not understand you here, ...

whats the problem with me wanting to know what resolution my xserver is
currently running at ?

i just do a fbset -i on it, and then i can for example set the console fbdev
mode to exatcly the same to avoid slow switching between the console and X.

Friendly,

Sven LUTHER

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