Re: [patch] radeonfb: FB_WAITFORVSYNC implementation

["Ville Syrjälä" <syrjala@sci.fi>]

On Sat, Mar 12, 2005 at 10:33:45AM -0500, Jon Smirl wrote:
> You can't do this without coordination from X and DRM. If either of
> those are in use you will lock the machine with this patch.  DRM also
> implements WAITFORVSYNC as well as other interrupts. If you clear the
> ISR DRM is going to stop working.
> 
> X is a bigger problem. If the radeonfb adapter is not the primary X
> adapter, X is going to disable its IO/MEM access at the PCI level on
> VT switch. Your radeonfb will then take an interrupt and not be able
> to acknowledge it. This results in an interrupt loop and you rebooting
> your machine.
> 
> See the "Who is stomping PCI config space?" thread in the x.org xserver list.
> 
> Because of these issues WAITFORVSYNC in radeondb has to wait for
> merged DRM/fbdev to be implemented.

It's not a problem if one doesn't use X.Org/XFree86. Also this patch 
should not affect X.Org/XFree86 users unless they manage to call the 
FBIO_WAITFORVSYNC ioctl. matroxfb and atyfb both have similar interrupt 
support and X can still be used with both.

-- 
Ville Syrjälä
syrjala@sci.fi
http://www.sci.fi/~syrjala/


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