Add more doxygen documentation, including notes on WaitMarker() and

    MarkSync() that I noticed were needed while reading the VIA driver.

1 files changed, 9 insertions, 0 deletions

diff --git a/exa/exa.h b/exa/exa.h
index d4d660bf7..2cb200854 100644
--- a/exa/exa.h
+++ b/exa/exa.h
@@ -564,6 +564,11 @@ typedef struct _ExaDriver {
      * data with the CPU, but is not important in the current incarnation of
      * EXA.
      *
+     * Note that drivers should call exaMarkSync() when they have done some
+     * acceleration, rather than their own MarkSync() handler, as otherwise EXA
+     * will be unaware of the driver's acceleration and not sync to it during
+     * fallbacks.
+     *
      * MarkSync() is optional.
      */
     int		(*MarkSync)   (ScreenPtr pScreen);
@@ -574,6 +579,10 @@ typedef struct _ExaDriver {
      * meaningless, and all rendering by the hardware should be completed before
      * WaitMarker() returns.
      *
+     * Note that drivers should call exaWaitSync() to wait for all acceleration
+     * to finish, as otherwise EXA will be unaware of the driver having
+     * synchronized, resulting in excessive WaitMarker() calls.
+     *
      * WaitMarker() is required of all drivers.
      */
     void	(*WaitMarker) (ScreenPtr pScreen, int marker);