Problem: Wait for VSync on pipe A and Wake up on pipe B

Jesse Barnes jbarnes at
Thu Aug 20 09:21:17 PDT 2009

On Thu, 20 Aug 2009 09:41:28 +0000 (GMT)
Nicolas Cadio <nicolas.cadio at> wrote:

> Hello,
> I have an application which must to synchronize with the vertical
> synchronisation of my display. To do this synchronization, I use a
> function of GLX (glXWaitVideoSyncSGI).
> This function call the function DRM to wait the vertical
> synchronization (drmWaitVBlank) and the driver (drm.ko) does a wait
> on the pipe A of my Xserver.
> But my output  (LVDS) of my Xserver is connected to the pipe B and so
> the driver (drm.ko) does a wake up on the pipe B.
> So my applicaton is not synchronized with my display.
> I would like to know how to configure my application for it uses the
> pipe B when it does a wait for the vertical synchronization. Where I
> can configure my application for it uses the pipe B for the VSync ?
> Is it in the xorg.conf or elsewhere?

With DRI2 we don't currently have a way to do this, but we're working
on adding one (along with some other sync

Jesse Barnes, Intel Open Source Technology Center

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