[RFC] DRI2 synchronization and swap bits

Eric Anholt eric at anholt.net
Fri Oct 30 11:42:06 PDT 2009

On Fri, 2009-10-30 at 10:59 -0700, Jesse Barnes wrote:
> I've put up some trees (after learning my lesson about working in the
> main tree) with the latest DRI2 sync/swap bits:
>   git://git.freedesktop.org/home/jbarnes/xserver master branch
>   git://git.freedesktop.org/home/jbarnes/mesa master branch
> They includes support for some new DRI2 requests (proto for which is in
> the dri2-swapbuffers branch of dri2proto), including:
>   DRI2SwapBuffers
>   DRI2GetMSC
>   DRI2WaitMSC
> and
>   DRI2WaitSBC
> These allow us to support GLX extensions like SGI_video_sync,
> OML_swap_control and SGI_swap_interval.
> There have been a few comments about the protocol so far:
>   1) DRI2SwapBuffers
>      a) Concern about doing another round trip to fetch new buffers
> 	following the swap.
>         I think this is a valid concern, we could potentially respond
>         from the swap with the new buffers, but this would make some
>         memory saving optimizations more difficult (e.g. freeing
>         buffers if no drawing comes in for a short time after the swap).

You're doing one round-trip anyway, and if users are concerned about the
second one, go use XCB already.  (We need to go fix Mesa to do that).

Eric Anholt
eric at anholt.net                         eric.anholt at intel.com

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