Waiting for vertical refresh on Intel 965 and 945 chips in recent git

[Hamish Moffatt]

On Fri, Jun 08, 2007 at 08:23:05AM +0200, Michel Dänzer wrote:
> On Thu, 2007-06-07 at 18:00 +0100, Simon Farnsworth wrote:
> > 
> > In the 7.2 release, I could use the DRM directly to wait for vertical
> > blanking, using the DRM_IOCTL_WAIT_VBLANK ioctl. The intel driver has
> > been changed to only enable the interrupt if 3D is in use, so I reworked
> > my code to use the GLX_SGI_video_sync extension to wait for VBlank.
> > 
> > I am now finding that the OpenGL based wait for VBlank also fails if the
> > window I create to get an OpenGL context is fully obscured;
> > glXWaitVideoSyncSGI returns 5 (GLX_BAD_CONTEXT). My code automatically
> > falls back to trying the DRM method, but DRM_IOCTL_WAIT_VBLANK returns
> > 16 (EBUSY).
> 
> Yes, this is because the X server DRI layer now counts DRI windows
> according to visibility, to allow e.g. page flipping to work with
> multiple windows as long as only one of them is visible. So the intel
> driver can't tell the difference between a window being invisible and it
> not existing at all and disables the vblank interrupts.

How is "3D in use" defined?

MythTV uses DRM vertical blanking sync with Xv output; I wouldn't say it
uses 3D by any stretch of the imagination.


thanks,
Hamish
-- 
Hamish Moffatt VK3SB <hamish at debian.org> <hamish at cloud.net.au>