[PATCH] dri2: work around broken DRI2CreateDrawable callers

[Daniel Drake]

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.

Signed-off-by: Daniel Drake <drake at endlessm.com>
---
 hw/xfree86/dri2/dri2.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/hw/xfree86/dri2/dri2.c b/hw/xfree86/dri2/dri2.c
index 729a323..4eba896 100644
--- a/hw/xfree86/dri2/dri2.c
+++ b/hw/xfree86/dri2/dri2.c
@@ -328,6 +328,13 @@ DRI2CreateDrawable2(ClientPtr client, DrawablePtr pDraw, XID id,
     int rc;
 
     pPriv = DRI2GetDrawable(pDraw);
+    if (pPriv && dri2_id_out == NULL) {
+        /* We already allocated a DRI2Drawable for this drawable, and the
+         * caller doesn't care about the dri2_id. This means we don't need
+         * to allocate another one, we have nothing else to do. */
+        pPriv->prime_id = dri2_client->prime_id;
+        return Success;
+    }
     if (pPriv == NULL)
         pPriv = DRI2AllocateDrawable(pDraw);
     if (pPriv == NULL)
-- 
1.8.3.2