Refactor and fix core vblank support

Consolidate support for synchronizing to and retrieving vblank counters.  Also
fix the core vblank code to return monotonic MSC counters, which are required
by some GLX extensions.  Adding support for multiple pipes to a low level
driver is fairly easy, the Intel 965 driver provides simple example code (see
intel_buffers.c:intelWindowMoved()).

The new code bumps the media stream counter extension version to 2 and adds a
new getDrawableMSC callback.  This callback takes a drawablePrivate pointer,
which is used to calculate the MSC value seen by clients based on the actual
vblank counter(s) returned from the kernel.  The new drawable private fields
are as follows:
  - vblSeq - used for tracking vblank counts for buffer swapping
  - vblFlags - flags (e.g. current pipe), updated by low level driver
  - msc_base - MSC counter from the last time the current pipe changed
  - vblank_base - kernel DRM vblank counter from the last time the pipe changed

Using the above variables, the core vblank code (in vblank.c) can calculate a
monotonic MSC value.  The low level DRI drivers are responsible for updating
the current pipe (by setting VBLANK_FLAG_SECONDARY for example in vblFlags)
along with msc_base and vblank_base whenever the pipe associated with a given
drawable changes (again, see intelWindowMoved for an example of this).

Drivers should fill in the GetDrawableMSC DriverAPIRec field to point to
driDrawableGetMSC32 and add code for pipe switching as outlined above to fully
support the new scheme.

1 files changed, 13 insertions, 1 deletions

diff --git a/include/GL/internal/dri_interface.h b/include/GL/internal/dri_interface.h
index e7fbf8e8b..1b637afaf 100644
--- a/include/GL/internal/dri_interface.h
+++ b/include/GL/internal/dri_interface.h
@@ -170,7 +170,7 @@ struct __DRIframeTrackingExtensionRec {
  * Used by drivers that implement the GLX_SGI_video_sync extension.
  */
 #define __DRI_MEDIA_STREAM_COUNTER "DRI_MediaStreamCounter"
-#define __DRI_MEDIA_STREAM_COUNTER_VERSION 1
+#define __DRI_MEDIA_STREAM_COUNTER_VERSION 2
 struct __DRImediaStreamCounterExtensionRec {
     __DRIextension base;
 
@@ -189,6 +189,18 @@ struct __DRImediaStreamCounterExtensionRec {
     int (*waitForMSC)(__DRIdrawable *drawable,
 		      int64_t target_msc, int64_t divisor, int64_t remainder,
 		      int64_t * msc, int64_t * sbc);
+
+    /**
+     * Like the screen version of getMSC, but also takes a drawable so that
+     * the appropriate pipe's counter can be retrieved.
+     *
+     * Get the number of vertical refreshes since some point in time before
+     * this function was first called (i.e., system start up).
+     *
+     * \since Internal API version 2
+     */
+    int (*getDrawableMSC)(__DRIscreen *screen, void *drawablePrivate,
+			  int64_t *msc);
 };