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SubjectRe: [linux-fbdev] fbdev 2.4.0 cleanups
On Tue, Mar 14, 2000 at 10:42:48AM -0500, James A Simmons wrote:
>
> On Tue, 14 Mar 2000, Sven LUTHER wrote:
>
> > On Mon, Mar 13, 2000 at 10:27:14AM -0500, jsimmons@ugradlib.acsu.buffalo.edu wrote:
> > >
> > > > There is O_NDELAY for audio devices, is not it?
> > >
> > > Try opening /dev/dsp. I don't think it will work. It shouldn't. I can see
> > > lots of problems here.
> > >
> > > > BTW, it is really surprising
> > > > that I cannot run 'fbset' from XF86_FBDev anymore :-(
> > >
> > > Doesn't X server have keys to changes modes. I know the regular XFree86
> > > servers do. I have used keys for this. If X server fb doesn't do this then
> > > its broken and it should function just like other X servers.
> >
> > changing mode is not the only reason why one wants to run fbset, ...
>
> 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.

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, ...

Friendly,

Sven LUTHER

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