Bug #7639: Only swap out pixmaps (rather than everything) on VT switch in EXA.

This is a new behavior for version 2.1 of EXA, and only takes effect if the
driver has requested that.  Otherwise, the previous behavior remains the same.

exa/exa.h

@@ -39,7 +39,7 @@
 #include "fb.h"
 
 #define EXA_VERSION_MAJOR   2
-#define EXA_VERSION_MINOR   0
+#define EXA_VERSION_MINOR   1
 #define EXA_VERSION_RELEASE 0
 
 typedef struct _ExaOffscreenArea ExaOffscreenArea;
@@ -73,8 +73,8 @@ struct _ExaOffscreenArea {
 typedef struct _ExaDriver {
     /**
      * exa_major and exa_minor should be set by the driver to the version of
-     * EXA which the driver was compiled for (or configures itself at runtime to
+     * EXA which the driver was compiled for (or configures itself at runtime
-     * support).  This allows EXA to extend the structure for new features
+     * to support).  This allows EXA to extend the structure for new features
      * without breaking ABI for drivers compiled against older versions.
      */
     int exa_major, exa_minor;

exa/exa_migration.c

@@ -249,7 +249,7 @@ exaCopyDirtyToFb (PixmapPtr pPixmap)
  * Called when the memory manager decides it's time to kick the pixmap out of
  * framebuffer entirely.
  */
-static void
+void
 exaPixmapSave (ScreenPtr pScreen, ExaOffscreenArea *area)
 {
     PixmapPtr pPixmap = area->privData;

exa/exa_offscreen.c

@@ -81,15 +81,14 @@ ExaOffscreenKickOut (ScreenPtr pScreen, ExaOffscreenArea *area)
  * @param save callback for when the area is evicted from memory
  * @param privdata private data for the save callback.
  *
- * Allocates offscreen memory from the device associated with pScreen.  size and
+ * Allocates offscreen memory from the device associated with pScreen.  size
- * align deteremine where and how large the allocated area is, and locked will
+ * and align deteremine where and how large the allocated area is, and locked
- * mark whether it should be held in card memory.  privdata may be any pointer
+ * will mark whether it should be held in card memory.  privdata may be any
- * for the save callback when the area is removed.
+ * pointer for the save callback when the area is removed.
  *
- * Note that locked areas do get evicted on VT switch, because during that time
+ * Note that locked areas do get evicted on VT switch unless the driver
- * all offscreen memory becomes inaccessible.  This may change in the future,
+ * requested version 2.1 or newer behavior.  In that case, the save callback is
- * but drivers should be aware of this and provide a callback to mark that their
+ * still called.
- * locked allocation was evicted, and then restore it if necessary on EnterVT.
  */
 ExaOffscreenArea *
 exaOffscreenAlloc (ScreenPtr pScreen, int size, int align,
@@ -256,6 +255,9 @@ exaOffscreenAlloc (ScreenPtr pScreen, int size, int align,
     return area;
 }
 
+/**
+ * Ejects all offscreen areas, and uninitializes the offscreen memory manager.
+ */
 void
 ExaOffscreenSwapOut (ScreenPtr pScreen)
 {
@@ -283,12 +285,56 @@ ExaOffscreenSwapOut (ScreenPtr pScreen)
     ExaOffscreenFini (pScreen);
 }
 
+/** Ejects all pixmaps managed by EXA. */
+static void
+ExaOffscreenEjectPixmaps (ScreenPtr pScreen)
+{
+    ExaScreenPriv (pScreen);
+
+    ExaOffscreenValidate (pScreen);
+    /* loop until a single free area spans the space */
+    for (;;)
+    {
+	ExaOffscreenArea *area;
+
+	for (area = pExaScr->info->offScreenAreas; area != NULL;
+	     area = area->next)
+	{
+	    if (area->state == ExaOffscreenRemovable &&
+		area->save == exaPixmapSave)
+	    {
+		(void) ExaOffscreenKickOut (pScreen, area);
+		ExaOffscreenValidate (pScreen);
+		break;
+	    }
+	}
+	if (area == NULL)
+	    break;
+    }
+    ExaOffscreenValidate (pScreen);
+}
+
 void
 ExaOffscreenSwapIn (ScreenPtr pScreen)
 {
     exaOffscreenInit (pScreen);
 }
 
+/**
+ * Prepares EXA for disabling of FB access, or restoring it.
+ *
+ * In version 2.1, the disabling results in pixmaps being ejected, while other
+ * allocations remain.  With this plus the prevention of migration while
+ * swappedOut is set, EXA by itself should not cause any access of the
+ * framebuffer to occur while swapped out.  Any remaining issues are the
+ * responsibility of the driver.
+ *
+ * Prior to version 2.1, all allocations, including locked ones, are ejected
+ * when access is disabled, and the allocator is torn down while swappedOut
+ * is set.  This is more drastic, and caused implementation difficulties for
+ * many drivers that could otherwise handle the lack of FB access while
+ * swapped out.
+ */
 void
 exaEnableDisableFBAccess (int index, Bool enable)
 {
@@ -296,9 +342,13 @@ exaEnableDisableFBAccess (int index, Bool enable)
     ExaScreenPriv (pScreen);
 
     if (!enable) {
+	if (pExaScr->info->exa_minor < 1)
 	    ExaOffscreenSwapOut (pScreen);
+	else
+	    ExaOffscreenEjectPixmaps (pScreen);
 	pExaScr->swappedOut = TRUE;
     } else {
+	if (pExaScr->info->exa_minor < 1)
 	    ExaOffscreenSwapIn (pScreen);
 	pExaScr->swappedOut = FALSE;
     }

exa/exa_priv.h

@@ -412,4 +412,7 @@ exaGlyphs (CARD8	op,
 void
 exaDoMigration (ExaMigrationPtr pixmaps, int npixmaps, Bool can_accel);
 
+void
+exaPixmapSave (ScreenPtr pScreen, ExaOffscreenArea *area);
+
 #endif /* EXAPRIV_H */