[Bug 90789] Vsync doesn't work for rotated display

[Richard Wilbur]

Interesting that in the patch
--------------------------------------------

diff --git a/src/drmmode_display.c b/src/drmmode_display.c
[...]
@@ -2253,6 +2317,9 @@ Bool drmmode_set_desired_modes(ScrnInfoPtr
pScrn, drmmode_ptr drmmode,
  crtc->desiredY = 0;
  }

+ if (1 || info->tear_free || info->shadow_primary)
+    crtc->driverIsPerformingTransform = TRUE;
+
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Seems to me this will always short-circuit to true which makes the
conditional superfluous.  I'm guessing there may still be some merit
to conditionally setting driverIsPerformingTransform but the details
simply need to be worked out?