[PATCH] dri2: work around broken DRI2CreateDrawable callers

[Chris Wilson]

On Fri, Feb 07, 2014 at 08:43:11AM -0600, Daniel Drake wrote:
> The state of the DRI2CreateDrawable request is a little unclear.
> dri2proto.txt states that it was dropped in version 1.99.2, but
> actually this must still be called exactly once for each drawable
> before GetBuffers and friends can be called, because it is the only
> way that the internal DRI2DrawableRec structure will be allocated.
> 
> Mali fails to obey this unwritten rule and instead calls CreateDrawable
> before each and every GetBuffers request. That causes a new dri2_id and
> internal reference to be created every time. When we then come to
> invalidate the drawable after GetBuffers+SwapBuffers for frame N, we end
> up generating N invalidate events from DRI2InvalidateDrawable. Things
> quickly get out of hand.
> 
> Fix this by detecting the fact that we're being called from
> the DRI2CreateDrawable request context (i.e. caller does not get to
> learn about the assigned dri2_id). In that case, just ensure that
> we have allocated the relevant internal DRI2 private data, and return.

I recently came across something very similar because it affects mesa
also. The problem is that we do want to track a reference per Client, so
simply creating a single reference seems fraught with danger. For mesa,
I thought using a named reference, i.e. passing the dri2_id from the
Client to use for the reference, and then destroying that reference
along with mesa's glXDrawable, actually fixes a few bugs in
mesa/src/glx/dri2_glx.c

Did you find an alternative solution for mali? If not, I think I can
generalise this into only allocating a single reference per DRI2 Client
per Drawable.
-Chris

-- 
Chris Wilson, Intel Open Source Technology Centre