diff --git a/include/hardware/hwcomposer.h b/include/hardware/hwcomposer.h
index 11176ec..a036da3 100644
--- a/include/hardware/hwcomposer.h
+++ b/include/hardware/hwcomposer.h
@@ -64,7 +64,7 @@
 
     /*
      * eventControl(..., event, enabled)
-     * Enables or disables h/w composer events for a display.
+     * Enables or disables h/w composer events.
      *
      * eventControl can be called from any thread and takes effect
      * immediately.
@@ -77,14 +77,13 @@
      */
 
     int (*eventControl)(
-            struct hwc_composer_device_1* dev, int dpy,
-            int event, int enabled);
+            struct hwc_composer_device_1* dev, int event, int enabled);
 
     /*
      * This field is OPTIONAL and can be NULL.
      *
      * blank(..., blank)
-     * Blanks or unblanks a display's screen.
+     * Blanks or unblanks the screen.
      *
      * Turns the screen off when blank is nonzero, on when blank is zero.
      * Blanking may also be triggered by a call to set..., 0, 0, 0).  Multiple
@@ -93,7 +92,7 @@
      * returns 0 on success, negative on error.
      */
 
-    int (*blank)(struct hwc_composer_device_1* dev, int dpy, int blank);
+    int (*blank)(struct hwc_composer_device_1* dev, int blank);
 
 } hwc_methods_1_t;
 
@@ -216,14 +215,8 @@
 
 } hwc_layer_1_t;
 
-/* This represents a display, typically an EGLDisplay object */
-typedef void* hwc_display_t;
-
-/* This represents a surface, typically an EGLSurface object  */
-typedef void* hwc_surface_t;
-
 /*
- * hwc_display_contents_1_t::flags values
+ * hwc_layer_list_t::flags values
  */
 enum {
     /*
@@ -235,36 +228,21 @@
 };
 
 /*
- * Description of the contents to output on a display.
- *
- * This is the top-level structure passed to the prepare and set calls to
- * negotiate and commit the composition of a display image.
+ * List of layers.
+ * The handle members of hwLayers elements must be unique.
  */
-typedef struct hwc_display_contents_1 {
-    /* File descriptor referring to a Sync HAL fence object which will signal
-     * when this display image is no longer visible, i.e. when the following
-     * set() takes effect. The fence object is created and returned by the set
-     * call; this field will be -1 on entry to prepare and set. SurfaceFlinger
-     * will close the returned file descriptor.
-     */
-    int flipFenceFd;
-
-    /* (dpy, sur) is the target of SurfaceFlinger's OpenGL ES composition.
-     * They aren't relevant to prepare. The set call should commit this surface
-     * atomically to the display along with any overlay layers.
-     */
-    hwc_display_t dpy;
-    hwc_surface_t sur;
-
-    /* List of layers that will be composed on the display. The buffer handles
-     * in the list will be unique. If numHwLayers is 0 and/or hwLayers is NULL,
-     * all composition will be performed by SurfaceFlinger.
-     */
+typedef struct hwc_layer_list_1 {
     uint32_t flags;
     size_t numHwLayers;
     hwc_layer_1_t hwLayers[0];
+} hwc_layer_list_1_t;
 
-} hwc_display_contents_1_t;
+/* This represents a display, typically an EGLDisplay object */
+typedef void* hwc_display_t;
+
+/* This represents a surface, typically an EGLSurface object  */
+typedef void* hwc_surface_t;
+
 
 /* see hwc_composer_device::registerProcs()
  * Any of the callbacks can be NULL, in which case the corresponding
@@ -284,10 +262,9 @@
 
     /*
      * (*vsync)() is called by the h/w composer HAL when a vsync event is
-     * received and HWC_EVENT_VSYNC is enabled on a display
-     * (see: hwc_event_control).
+     * received and HWC_EVENT_VSYNC is enabled (see: hwc_event_control).
      *
-     * the "dpy" parameter indicates which display the vsync event is for.
+     * the "zero" parameter must always be 0.
      * the "timestamp" parameter is the system monotonic clock timestamp in
      *   nanosecond of when the vsync event happened.
      *
@@ -301,8 +278,9 @@
      * hwc_composer_device.set(..., 0, 0, 0) (screen off). The implementation
      * can either stop or continue to process VSYNC events, but must not
      * crash or cause other problems.
+     *
      */
-    void (*vsync)(struct hwc_procs* procs, int dpy, int64_t timestamp);
+    void (*vsync)(struct hwc_procs* procs, int zero, int64_t timestamp);
 } hwc_procs_t;
 
 
@@ -321,55 +299,72 @@
      *
      * (*prepare)() can be called more than once, the last call prevails.
      *
-     * The HWC responds by setting the compositionType field in each layer to
-     * either HWC_FRAMEBUFFER or HWC_OVERLAY. In the former case, the
-     * composition for the layer is handled by SurfaceFlinger with OpenGL ES,
-     * in the later case, the HWC will have to handle the layer's composition.
+     * The HWC responds by setting the compositionType field to either
+     * HWC_FRAMEBUFFER or HWC_OVERLAY. In the former case, the composition for
+     * this layer is handled by SurfaceFlinger with OpenGL ES, in the later
+     * case, the HWC will have to handle this layer's composition.
      *
      * (*prepare)() is called with HWC_GEOMETRY_CHANGED to indicate that the
      * list's geometry has changed, that is, when more than just the buffer's
      * handles have been updated. Typically this happens (but is not limited to)
      * when a window is added, removed, resized or moved.
      *
+     * a NULL list parameter or a numHwLayers of zero indicates that the
+     * entire composition will be handled by SurfaceFlinger with OpenGL ES.
+     *
      * returns: 0 on success. An negative error code on error. If an error is
      * returned, SurfaceFlinger will assume that none of the layer will be
      * handled by the HWC.
      */
     int (*prepare)(struct hwc_composer_device_1 *dev,
-                    size_t numDisplays, hwc_display_contents_1_t** displays);
+                    hwc_layer_list_1_t* list);
 
     /*
      * (*set)() is used in place of eglSwapBuffers(), and assumes the same
      * functionality, except it also commits the work list atomically with
      * the actual eglSwapBuffers().
      *
-     * The layer lists are guaranteed to be the same as the ones returned from
-     * the last call to (*prepare)().
+     * The list parameter is guaranteed to be the same as the one returned
+     * from the last call to (*prepare)().
      *
-     * When this call returns the caller assumes that the displays will be
-     * updated in the near future with the content of their work lists, without
-     * artifacts during the transition from the previous frame.
+     * When this call returns the caller assumes that:
      *
-     * A display with a NULL layer list or a numHwLayers of zero indicates that
-     * the entire composition has been handled by SurfaceFlinger with OpenGL ES.
+     * - the display will be updated in the near future with the content
+     *   of the work list, without artifacts during the transition from the
+     *   previous frame.
+     *
+     * - all objects are available for immediate access or destruction, in
+     *   particular, hwc_region_t::rects data and hwc_layer_t::layer's buffer.
+     *   Note that this means that immediately accessing (potentially from a
+     *   different process) a buffer used in this call will not result in
+     *   screen corruption, the driver must apply proper synchronization or
+     *   scheduling (eg: block the caller, such as gralloc_module_t::lock(),
+     *   OpenGL ES, Camera, Codecs, etc..., or schedule the caller's work
+     *   after the buffer is freed from the actual composition).
+     *
+     * a NULL list parameter or a numHwLayers of zero indicates that the
+     * entire composition has been handled by SurfaceFlinger with OpenGL ES.
      * In this case, (*set)() behaves just like eglSwapBuffers().
      *
-     * The dpy, surf, and layers fields are set to NULL to indicate that the
-     * screen is turning off. This happens WITHOUT prepare() being called first.
-     * This is a good time to free h/w resources and/or power down the relevant
-     * h/w blocks.
+     * dpy, sur, and list are set to NULL to indicate that the screen is
+     * turning off. This happens WITHOUT prepare() being called first.
+     * This is a good time to free h/w resources and/or power
+     * the relevant h/w blocks down.
      *
      * IMPORTANT NOTE: there is an implicit layer containing opaque black
-     * pixels behind all the layers in the list. It is the responsibility of
-     * the hwcomposer module to make sure black pixels are output (or blended
-     * from).
+     * pixels behind all the layers in the list.
+     * It is the responsibility of the hwcomposer module to make
+     * sure black pixels are output (or blended from).
      *
      * returns: 0 on success. An negative error code on error:
      *    HWC_EGL_ERROR: eglGetError() will provide the proper error code
      *    Another code for non EGL errors.
+     *
      */
     int (*set)(struct hwc_composer_device_1 *dev,
-                size_t numDisplays, hwc_display_contents_1_t** displays);
+                hwc_display_t dpy,
+                hwc_surface_t sur,
+                hwc_layer_list_1_t* list);
 
     /*
      * This field is OPTIONAL and can be NULL.
diff --git a/modules/hwcomposer/hwcomposer.cpp b/modules/hwcomposer/hwcomposer.cpp
index f0a5512..0e49e4c 100644
--- a/modules/hwcomposer/hwcomposer.cpp
+++ b/modules/hwcomposer/hwcomposer.cpp
@@ -67,26 +67,26 @@
             l->displayFrame.bottom);
 }
 
-static int hwc_prepare(hwc_composer_device_1_t *dev,
-        size_t numDisplays, hwc_display_contents_1_t** displays) {
-    if (displays && (displays[0]->flags & HWC_GEOMETRY_CHANGED)) {
-        for (size_t i=0 ; i<displays[0]->numHwLayers ; i++) {
+static int hwc_prepare(hwc_composer_device_1_t *dev, hwc_layer_list_1_t* list) {
+    if (list && (list->flags & HWC_GEOMETRY_CHANGED)) {
+        for (size_t i=0 ; i<list->numHwLayers ; i++) {
             //dump_layer(&list->hwLayers[i]);
-            displays[0]->hwLayers[i].compositionType = HWC_FRAMEBUFFER;
+            list->hwLayers[i].compositionType = HWC_FRAMEBUFFER;
         }
     }
     return 0;
 }
 
 static int hwc_set(hwc_composer_device_1_t *dev,
-        size_t numDisplays, hwc_display_contents_1_t** displays)
+        hwc_display_t dpy,
+        hwc_surface_t sur,
+        hwc_layer_list_1_t* list)
 {
     //for (size_t i=0 ; i<list->numHwLayers ; i++) {
     //    dump_layer(&list->hwLayers[i]);
     //}
 
-    EGLBoolean sucess = eglSwapBuffers((EGLDisplay)displays[0]->dpy,
-            (EGLSurface)displays[0]->sur);
+    EGLBoolean sucess = eglSwapBuffers((EGLDisplay)dpy, (EGLSurface)sur);
     if (!sucess) {
         return HWC_EGL_ERROR;
     }