loader: Add dri3 helper

v2: From Martin Peres
 - Try to fit in the 80-col limit as much as possible

v3: From Martin Peres
 - introduce loader_dri3_helper.la to avoid dragging the xcb dep everywhere (Kristian & Emil)
 - get rid of the width, height, dri_screen and is_different_gpu vfuncs (Kristian)
 - replace the create/destroy functions with init/fini for dri3 drawables
 - prefix static functions with dri3_ and exported ones with loader_dri3 (Emil)
 - keep the function definition consistent (Emil)

Signed-off-by: Boyan Ding <[email protected]>
Signed-off-by: Martin Peres <[email protected]>
Reviewed-by: Kristian Høgsberg <[email protected]>
Reviewed-by: Emil Velikov <[email protected]>

1 files changed, 1376 insertions, 0 deletions

diff --git a/src/loader/loader_dri3_helper.c b/src/loader/loader_dri3_helper.c
new file mode 100644
index 00000000000..9093b179317
--- /dev/null
+++ b/src/loader/loader_dri3_helper.c
@@ -0,0 +1,1376 @@
+/*
+ * Copyright © 2013 Keith Packard
+ * Copyright © 2015 Boyan Ding
+ *
+ * Permission to use, copy, modify, distribute, and sell this software and its
+ * documentation for any purpose is hereby granted without fee, provided that
+ * the above copyright notice appear in all copies and that both that copyright
+ * notice and this permission notice appear in supporting documentation, and
+ * that the name of the copyright holders not be used in advertising or
+ * publicity pertaining to distribution of the software without specific,
+ * written prior permission.  The copyright holders make no representations
+ * about the suitability of this software for any purpose.  It is provided "as
+ * is" without express or implied warranty.
+ *
+ * THE COPYRIGHT HOLDERS DISCLAIM ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
+ * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
+ * EVENT SHALL THE COPYRIGHT HOLDERS BE LIABLE FOR ANY SPECIAL, INDIRECT OR
+ * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE,
+ * DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+ * TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE
+ * OF THIS SOFTWARE.
+ */
+
+#include <fcntl.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#include <X11/xshmfence.h>
+#include <xcb/xcb.h>
+#include <xcb/dri3.h>
+#include <xcb/present.h>
+
+#include <X11/Xlib-xcb.h>
+
+#include "loader_dri3_helper.h"
+
+/* From xmlpool/options.h, user exposed so should be stable */
+#define DRI_CONF_VBLANK_NEVER 0
+#define DRI_CONF_VBLANK_DEF_INTERVAL_0 1
+#define DRI_CONF_VBLANK_DEF_INTERVAL_1 2
+#define DRI_CONF_VBLANK_ALWAYS_SYNC 3
+
+static inline void
+dri3_fence_reset(xcb_connection_t *c, struct loader_dri3_buffer *buffer)
+{
+   xshmfence_reset(buffer->shm_fence);
+}
+
+static inline void
+dri3_fence_set(struct loader_dri3_buffer *buffer)
+{
+   xshmfence_trigger(buffer->shm_fence);
+}
+
+static inline void
+dri3_fence_trigger(xcb_connection_t *c, struct loader_dri3_buffer *buffer)
+{
+   xcb_sync_trigger_fence(c, buffer->sync_fence);
+}
+
+static inline void
+dri3_fence_await(xcb_connection_t *c, struct loader_dri3_buffer *buffer)
+{
+   xcb_flush(c);
+   xshmfence_await(buffer->shm_fence);
+}
+
+static void
+dri3_update_num_back(struct loader_dri3_drawable *draw)
+{
+   draw->num_back = 1;
+   if (draw->flipping) {
+      if (!draw->is_pixmap &&
+          !(draw->present_capabilities & XCB_PRESENT_CAPABILITY_ASYNC))
+         draw->num_back++;
+      draw->num_back++;
+   }
+   if (draw->vtable->get_swap_interval(draw) == 0)
+      draw->num_back++;
+}
+
+void
+loader_dri3_set_swap_interval(struct loader_dri3_drawable *draw, int interval)
+{
+   interval = draw->vtable->clamp_swap_interval(draw, interval);
+   draw->vtable->set_swap_interval(draw, interval);
+   dri3_update_num_back(draw);
+}
+
+/** dri3_free_render_buffer
+ *
+ * Free everything associated with one render buffer including pixmap, fence
+ * stuff and the driver image
+ */
+static void
+dri3_free_render_buffer(struct loader_dri3_drawable *draw,
+                        struct loader_dri3_buffer *buffer)
+{
+   if (buffer->own_pixmap)
+      xcb_free_pixmap(draw->conn, buffer->pixmap);
+   xcb_sync_destroy_fence(draw->conn, buffer->sync_fence);
+   xshmfence_unmap_shm(buffer->shm_fence);
+   (draw->ext->image->destroyImage)(buffer->image);
+   if (buffer->linear_buffer)
+      (draw->ext->image->destroyImage)(buffer->linear_buffer);
+   free(buffer);
+}
+
+void
+loader_dri3_drawable_fini(struct loader_dri3_drawable *draw)
+{
+   int i;
+
+   (draw->ext->core->destroyDrawable)(draw->dri_drawable);
+
+   for (i = 0; i < LOADER_DRI3_NUM_BUFFERS; i++) {
+      if (draw->buffers[i])
+         dri3_free_render_buffer(draw, draw->buffers[i]);
+   }
+
+   if (draw->special_event)
+      xcb_unregister_for_special_event(draw->conn, draw->special_event);
+}
+
+int
+loader_dri3_drawable_init(xcb_connection_t *conn,
+                          xcb_drawable_t drawable,
+                          __DRIscreen *dri_screen,
+                          bool is_different_gpu,
+                          const __DRIconfig *dri_config,
+                          struct loader_dri3_extensions *ext,
+                          struct loader_dri3_vtable *vtable,
+                          struct loader_dri3_drawable *draw)
+{
+   xcb_get_geometry_cookie_t cookie;
+   xcb_get_geometry_reply_t *reply;
+   xcb_generic_error_t *error;
+   GLint vblank_mode = DRI_CONF_VBLANK_DEF_INTERVAL_1;
+   int swap_interval;
+
+   draw->conn = conn;
+   draw->ext = ext;
+   draw->vtable = vtable;
+   draw->drawable = drawable;
+   draw->dri_screen = dri_screen;
+   draw->is_different_gpu = is_different_gpu;
+
+   draw->have_back = 0;
+   draw->have_fake_front = 0;
+   draw->first_init = true;
+
+   if (draw->ext->config)
+      draw->ext->config->configQueryi(draw->dri_screen,
+                                      "vblank_mode", &vblank_mode);
+
+   switch (vblank_mode) {
+   case DRI_CONF_VBLANK_NEVER:
+   case DRI_CONF_VBLANK_DEF_INTERVAL_0:
+      swap_interval = 0;
+      break;
+   case DRI_CONF_VBLANK_DEF_INTERVAL_1:
+   case DRI_CONF_VBLANK_ALWAYS_SYNC:
+   default:
+      swap_interval = 1;
+      break;
+   }
+   draw->vtable->set_swap_interval(draw, swap_interval);
+
+   dri3_update_num_back(draw);
+
+   /* Create a new drawable */
+   draw->dri_drawable =
+      (draw->ext->image_driver->createNewDrawable)(dri_screen,
+                                                   dri_config,
+                                                   draw);
+
+   if (!draw->dri_drawable)
+      return 1;
+
+   cookie = xcb_get_geometry(draw->conn, draw->drawable);
+   reply = xcb_get_geometry_reply(draw->conn, cookie, &error);
+   if (reply == NULL || error != NULL) {
+      draw->ext->core->destroyDrawable(draw->dri_drawable);
+      return 1;
+   }
+
+   draw->width = reply->width;
+   draw->height = reply->height;
+   draw->depth = reply->depth;
+   draw->vtable->set_drawable_size(draw, draw->width, draw->height);
+   free(reply);
+
+   /*
+    * Make sure server has the same swap interval we do for the new
+    * drawable.
+    */
+   loader_dri3_set_swap_interval(draw, swap_interval);
+
+   return 0;
+}
+
+/*
+ * Process one Present event
+ */
+static void
+dri3_handle_present_event(struct loader_dri3_drawable *draw,
+                          xcb_present_generic_event_t *ge)
+{
+   switch (ge->evtype) {
+   case XCB_PRESENT_CONFIGURE_NOTIFY: {
+      xcb_present_configure_notify_event_t *ce = (void *) ge;
+
+      draw->width = ce->width;
+      draw->height = ce->height;
+      draw->vtable->set_drawable_size(draw, draw->width, draw->height);
+      break;
+   }
+   case XCB_PRESENT_COMPLETE_NOTIFY: {
+      xcb_present_complete_notify_event_t *ce = (void *) ge;
+
+      /* Compute the processed SBC number from the received 32-bit serial number
+       * merged with the upper 32-bits of the sent 64-bit serial number while
+       * checking for wrap.
+       */
+      if (ce->kind == XCB_PRESENT_COMPLETE_KIND_PIXMAP) {
+         draw->recv_sbc = (draw->send_sbc & 0xffffffff00000000LL) | ce->serial;
+         if (draw->recv_sbc > draw->send_sbc)
+            draw->recv_sbc -= 0x100000000;
+         switch (ce->mode) {
+         case XCB_PRESENT_COMPLETE_MODE_FLIP:
+            draw->flipping = true;
+            break;
+         case XCB_PRESENT_COMPLETE_MODE_COPY:
+            draw->flipping = false;
+            break;
+         }
+         dri3_update_num_back(draw);
+
+         if (draw->vtable->show_fps)
+            draw->vtable->show_fps(draw, ce->ust);
+
+         draw->ust = ce->ust;
+         draw->msc = ce->msc;
+      } else {
+         draw->recv_msc_serial = ce->serial;
+         draw->notify_ust = ce->ust;
+         draw->notify_msc = ce->msc;
+      }
+      break;
+   }
+   case XCB_PRESENT_EVENT_IDLE_NOTIFY: {
+      xcb_present_idle_notify_event_t *ie = (void *) ge;
+      int b;
+
+      for (b = 0; b < sizeof(draw->buffers) / sizeof(draw->buffers[0]); b++) {
+         struct loader_dri3_buffer *buf = draw->buffers[b];
+
+         if (buf && buf->pixmap == ie->pixmap) {
+            buf->busy = 0;
+            if (draw->num_back <= b && b < LOADER_DRI3_MAX_BACK) {
+               dri3_free_render_buffer(draw, buf);
+               draw->buffers[b] = NULL;
+            }
+            break;
+         }
+      }
+      break;
+   }
+   }
+   free(ge);
+}
+
+static bool
+dri3_wait_for_event(struct loader_dri3_drawable *draw)
+{
+   xcb_generic_event_t *ev;
+   xcb_present_generic_event_t *ge;
+
+   xcb_flush(draw->conn);
+   ev = xcb_wait_for_special_event(draw->conn, draw->special_event);
+   if (!ev)
+      return false;
+   ge = (void *) ev;
+   dri3_handle_present_event(draw, ge);
+   return true;
+}
+
+/** loader_dri3_wait_for_msc
+ *
+ * Get the X server to send an event when the target msc/divisor/remainder is
+ * reached.
+ */
+bool
+loader_dri3_wait_for_msc(struct loader_dri3_drawable *draw,
+                         int64_t target_msc,
+                         int64_t divisor, int64_t remainder,
+                         int64_t *ust, int64_t *msc, int64_t *sbc)
+{
+   uint32_t msc_serial;
+
+   msc_serial = ++draw->send_msc_serial;
+   xcb_present_notify_msc(draw->conn,
+                          draw->drawable,
+                          msc_serial,
+                          target_msc,
+                          divisor,
+                          remainder);
+
+   xcb_flush(draw->conn);
+
+   /* Wait for the event */
+   if (draw->special_event) {
+      while ((int32_t) (msc_serial - draw->recv_msc_serial) > 0) {
+         if (!dri3_wait_for_event(draw))
+            return false;
+      }
+   }
+
+   *ust = draw->notify_ust;
+   *msc = draw->notify_msc;
+   *sbc = draw->recv_sbc;
+
+   return true;
+}
+
+/** loader_dri3_wait_for_sbc
+ *
+ * Wait for the completed swap buffer count to reach the specified
+ * target. Presumably the application knows that this will be reached with
+ * outstanding complete events, or we're going to be here awhile.
+ */
+int
+loader_dri3_wait_for_sbc(struct loader_dri3_drawable *draw,
+                         int64_t target_sbc, int64_t *ust,
+                         int64_t *msc, int64_t *sbc)
+{
+   /* From the GLX_OML_sync_control spec:
+    *
+    *     "If <target_sbc> = 0, the function will block until all previous
+    *      swaps requested with glXSwapBuffersMscOML for that window have
+    *      completed."
+    */
+   if (!target_sbc)
+      target_sbc = draw->send_sbc;
+
+   while (draw->recv_sbc < target_sbc) {
+      if (!dri3_wait_for_event(draw))
+         return 0;
+   }
+
+   *ust = draw->ust;
+   *msc = draw->msc;
+   *sbc = draw->recv_sbc;
+   return 1;
+}
+
+/** loader_dri3_find_back
+ *
+ * Find an idle back buffer. If there isn't one, then
+ * wait for a present idle notify event from the X server
+ */
+static int
+dri3_find_back(struct loader_dri3_drawable *draw)
+{
+   int b;
+   xcb_generic_event_t *ev;
+   xcb_present_generic_event_t *ge;
+
+   for (;;) {
+      for (b = 0; b < draw->num_back; b++) {
+         int id = LOADER_DRI3_BACK_ID((b + draw->cur_back) % draw->num_back);
+         struct loader_dri3_buffer *buffer = draw->buffers[id];
+
+         if (!buffer || !buffer->busy) {
+            draw->cur_back = id;
+            return id;
+         }
+      }
+      xcb_flush(draw->conn);
+      ev = xcb_wait_for_special_event(draw->conn, draw->special_event);
+      if (!ev)
+         return -1;
+      ge = (void *) ev;
+      dri3_handle_present_event(draw, ge);
+   }
+}
+
+static xcb_gcontext_t
+dri3_drawable_gc(struct loader_dri3_drawable *draw)
+{
+   if (!draw->gc) {
+      uint32_t v = 0;
+      xcb_create_gc(draw->conn,
+                    (draw->gc = xcb_generate_id(draw->conn)),
+                    draw->drawable,
+                    XCB_GC_GRAPHICS_EXPOSURES,
+                    &v);
+   }
+   return draw->gc;
+}
+
+
+static struct loader_dri3_buffer *
+dri3_back_buffer(struct loader_dri3_drawable *draw)
+{
+   return draw->buffers[LOADER_DRI3_BACK_ID(draw->cur_back)];
+}
+
+static struct loader_dri3_buffer *
+dri3_fake_front_buffer(struct loader_dri3_drawable *draw)
+{
+   return draw->buffers[LOADER_DRI3_FRONT_ID];
+}
+
+static void
+dri3_copy_area(xcb_connection_t *c,
+               xcb_drawable_t    src_drawable,
+               xcb_drawable_t    dst_drawable,
+               xcb_gcontext_t    gc,
+               int16_t           src_x,
+               int16_t           src_y,
+               int16_t           dst_x,
+               int16_t           dst_y,
+               uint16_t          width,
+               uint16_t          height)
+{
+   xcb_void_cookie_t cookie;
+
+   cookie = xcb_copy_area_checked(c,
+                                  src_drawable,
+                                  dst_drawable,
+                                  gc,
+                                  src_x,
+                                  src_y,
+                                  dst_x,
+                                  dst_y,
+                                  width,
+                                  height);
+   xcb_discard_reply(c, cookie.sequence);
+}
+
+/**
+ * Asks the driver to flush any queued work necessary for serializing with the
+ * X command stream, and optionally the slightly more strict requirement of
+ * glFlush() equivalence (which would require flushing even if nothing had
+ * been drawn to a window system framebuffer, for example).
+ */
+void
+loader_dri3_flush(struct loader_dri3_drawable *draw,
+                  unsigned flags,
+                  enum __DRI2throttleReason throttle_reason)
+{
+   /* NEED TO CHECK WHETHER CONTEXT IS NULL */
+   __DRIcontext *dri_context = draw->vtable->get_dri_context(draw);
+
+   if (dri_context) {
+      draw->ext->flush->flush_with_flags(dri_context, draw->dri_drawable,
+                                         flags, throttle_reason);
+   }
+}
+
+void
+loader_dri3_copy_sub_buffer(struct loader_dri3_drawable *draw,
+                            int x, int y,
+                            int width, int height,
+                            bool flush)
+{
+   struct loader_dri3_buffer *back;
+   unsigned flags = __DRI2_FLUSH_DRAWABLE;
+   __DRIcontext *dri_context;
+
+   dri_context = draw->vtable->get_dri_context(draw);
+
+   /* Check we have the right attachments */
+   if (!draw->have_back || draw->is_pixmap)
+      return;
+
+   if (flush)
+      flags |= __DRI2_FLUSH_CONTEXT;
+   loader_dri3_flush(draw, flags, __DRI2_THROTTLE_SWAPBUFFER);
+
+   back = dri3_back_buffer(draw);
+   y = draw->height - y - height;
+
+   if (draw->is_different_gpu && draw->vtable->in_current_context(draw)) {
+      /* Update the linear buffer part of the back buffer
+       * for the dri3_copy_area operation
+       */
+      draw->ext->image->blitImage(dri_context,
+                                  back->linear_buffer,
+                                  back->image,
+                                  0, 0, back->width,
+                                  back->height,
+                                  0, 0, back->width,
+                                  back->height, __BLIT_FLAG_FLUSH);
+      /* We use blitImage to update our fake front,
+       */
+      if (draw->have_fake_front)
+         draw->ext->image->blitImage(dri_context,
+                                     dri3_fake_front_buffer(draw)->image,
+                                     back->image,
+                                     x, y, width, height,
+                                     x, y, width, height, __BLIT_FLAG_FLUSH);
+   }
+
+   dri3_fence_reset(draw->conn, back);
+   dri3_copy_area(draw->conn,
+                  dri3_back_buffer(draw)->pixmap,
+                  draw->drawable,
+                  dri3_drawable_gc(draw),
+                  x, y, x, y, width, height);
+   dri3_fence_trigger(draw->conn, back);
+   /* Refresh the fake front (if present) after we just damaged the real
+    * front.
+    */
+   if (draw->have_fake_front && !draw->is_different_gpu) {
+      dri3_fence_reset(draw->conn, dri3_fake_front_buffer(draw));
+      dri3_copy_area(draw->conn,
+                     dri3_back_buffer(draw)->pixmap,
+                     dri3_fake_front_buffer(draw)->pixmap,
+                     dri3_drawable_gc(draw),
+                     x, y, x, y, width, height);
+      dri3_fence_trigger(draw->conn, dri3_fake_front_buffer(draw));
+      dri3_fence_await(draw->conn, dri3_fake_front_buffer(draw));
+   }
+   dri3_fence_await(draw->conn, back);
+}
+
+void
+loader_dri3_copy_drawable(struct loader_dri3_drawable *draw,
+                          xcb_drawable_t dest,
+                          xcb_drawable_t src)
+{
+   loader_dri3_flush(draw, __DRI2_FLUSH_DRAWABLE, 0);
+
+   dri3_fence_reset(draw->conn, dri3_fake_front_buffer(draw));
+   dri3_copy_area(draw->conn,
+                  src, dest,
+                  dri3_drawable_gc(draw),
+                  0, 0, 0, 0, draw->width, draw->height);
+   dri3_fence_trigger(draw->conn, dri3_fake_front_buffer(draw));
+   dri3_fence_await(draw->conn, dri3_fake_front_buffer(draw));
+}
+
+void
+loader_dri3_wait_x(struct loader_dri3_drawable *draw)
+{
+   struct loader_dri3_buffer *front;
+   __DRIcontext *dri_context;
+
+   if (draw == NULL || !draw->have_fake_front)
+      return;
+
+   front = dri3_fake_front_buffer(draw);
+   dri_context = draw->vtable->get_dri_context(draw);
+
+   loader_dri3_copy_drawable(draw, front->pixmap, draw->drawable);
+
+   /* In the psc->is_different_gpu case, the linear buffer has been updated,
+    * but not yet the tiled buffer.
+    * Copy back to the tiled buffer we use for rendering.
+    * Note that we don't need flushing.
+    */
+   if (draw->is_different_gpu && draw->vtable->in_current_context(draw))
+      draw->ext->image->blitImage(dri_context,
+                                  front->image,
+                                  front->linear_buffer,
+                                  0, 0, front->width,
+                                  front->height,
+                                  0, 0, front->width,
+                                  front->height, 0);
+}
+
+void
+loader_dri3_wait_gl(struct loader_dri3_drawable *draw)
+{
+   struct loader_dri3_buffer *front;
+   __DRIcontext *dri_context;
+
+   if (draw == NULL || !draw->have_fake_front)
+      return;
+
+   front = dri3_fake_front_buffer(draw);
+   dri_context = draw->vtable->get_dri_context(draw);
+
+   /* In the psc->is_different_gpu case, we update the linear_buffer
+    * before updating the real front.
+    */
+   if (draw->is_different_gpu && draw->vtable->in_current_context(draw))
+      draw->ext->image->blitImage(dri_context,
+                                  front->linear_buffer,
+                                  front->image,
+                                  0, 0, front->width,
+                                  front->height,
+                                  0, 0, front->width,
+                                  front->height, __BLIT_FLAG_FLUSH);
+   loader_dri3_copy_drawable(draw, draw->drawable, front->pixmap);
+}
+
+/** dri3_flush_present_events
+ *
+ * Process any present events that have been received from the X server
+ */
+static void
+dri3_flush_present_events(struct loader_dri3_drawable *draw)
+{
+   /* Check to see if any configuration changes have occurred
+    * since we were last invoked
+    */
+   if (draw->special_event) {
+      xcb_generic_event_t    *ev;
+
+      while ((ev = xcb_poll_for_special_event(draw->conn,
+                                              draw->special_event)) != NULL) {
+         xcb_present_generic_event_t *ge = (void *) ev;
+         dri3_handle_present_event(draw, ge);
+      }
+   }
+}
+
+/** loader_dri3_swap_buffers_msc
+ *
+ * Make the current back buffer visible using the present extension
+ */
+int64_t
+loader_dri3_swap_buffers_msc(struct loader_dri3_drawable *draw,
+                             int64_t target_msc, int64_t divisor,
+                             int64_t remainder, unsigned flush_flags,
+                             bool force_copy)
+{
+   struct loader_dri3_buffer *back;
+   __DRIcontext *dri_context;
+   int64_t ret = 0;
+   uint32_t options = XCB_PRESENT_OPTION_NONE;
+   int swap_interval;
+
+   dri_context = draw->vtable->get_dri_context(draw);
+   swap_interval = draw->vtable->get_swap_interval(draw);
+
+   draw->vtable->flush_drawable(draw, flush_flags);
+
+   back = draw->buffers[LOADER_DRI3_BACK_ID(draw->cur_back)];
+   if (draw->is_different_gpu && back) {
+      /* Update the linear buffer before presenting the pixmap */
+      draw->ext->image->blitImage(dri_context,
+                                  back->linear_buffer,
+                                  back->image,
+                                  0, 0, back->width,
+                                  back->height,
+                                  0, 0, back->width,
+                                  back->height, __BLIT_FLAG_FLUSH);
+      /* Update the fake front */
+      if (draw->have_fake_front)
+         draw->ext->image->blitImage(dri_context,
+                                     draw->buffers[LOADER_DRI3_FRONT_ID]->image,
+                                     back->image,
+                                     0, 0, draw->width, draw->height,
+                                     0, 0, draw->width, draw->height,
+                                     __BLIT_FLAG_FLUSH);
+   }
+
+   dri3_flush_present_events(draw);
+
+   if (back && !draw->is_pixmap) {
+      dri3_fence_reset(draw->conn, back);
+
+      /* Compute when we want the frame shown by taking the last known
+       * successful MSC and adding in a swap interval for each outstanding swap
+       * request. target_msc=divisor=remainder=0 means "Use glXSwapBuffers()
+       * semantic"
+       */
+      ++draw->send_sbc;
+      if (target_msc == 0 && divisor == 0 && remainder == 0)
+         target_msc = draw->msc + swap_interval *
+                      (draw->send_sbc - draw->recv_sbc);
+      else if (divisor == 0 && remainder > 0) {
+         /* From the GLX_OML_sync_control spec:
+          *     "If <divisor> = 0, the swap will occur when MSC becomes
+          *      greater than or equal to <target_msc>."
+          *
+          * Note that there's no mention of the remainder.  The Present
+          * extension throws BadValue for remainder != 0 with divisor == 0, so
+          * just drop the passed in value.
+          */
+         remainder = 0;
+      }
+
+      /* From the GLX_EXT_swap_control spec
+       * and the EGL 1.4 spec (page 53):
+       *
+       *     "If <interval> is set to a value of 0, buffer swaps are not
+       *      synchronized to a video frame."
+       *
+       * Implementation note: It is possible to enable triple buffering
+       * behaviour by not using XCB_PRESENT_OPTION_ASYNC, but this should not be
+       * the default.
+       */
+      if (swap_interval == 0)
+          options |= XCB_PRESENT_OPTION_ASYNC;
+      if (force_copy)
+          options |= XCB_PRESENT_OPTION_COPY;
+
+      back->busy = 1;
+      back->last_swap = draw->send_sbc;
+      xcb_present_pixmap(draw->conn,
+                         draw->drawable,
+                         back->pixmap,
+                         (uint32_t) draw->send_sbc,
+                         0,                                    /* valid */
+                         0,                                    /* update */
+                         0,                                    /* x_off */
+                         0,                                    /* y_off */
+                         None,                                 /* target_crtc */
+                         None,
+                         back->sync_fence,
+                         options,
+                         target_msc,
+                         divisor,
+                         remainder, 0, NULL);
+      ret = (int64_t) draw->send_sbc;
+
+      /* If there's a fake front, then copy the source back buffer
+       * to the fake front to keep it up to date. This needs
+       * to reset the fence and make future users block until
+       * the X server is done copying the bits
+       */
+      if (draw->have_fake_front && !draw->is_different_gpu) {
+         dri3_fence_reset(draw->conn, draw->buffers[LOADER_DRI3_FRONT_ID]);
+         dri3_copy_area(draw->conn,
+                        back->pixmap,
+                        draw->buffers[LOADER_DRI3_FRONT_ID]->pixmap,
+                        dri3_drawable_gc(draw),
+                        0, 0, 0, 0,
+                        draw->width, draw->height);
+         dri3_fence_trigger(draw->conn, draw->buffers[LOADER_DRI3_FRONT_ID]);
+      }
+      xcb_flush(draw->conn);
+      if (draw->stamp)
+         ++(*draw->stamp);
+   }
+
+   (draw->ext->flush->invalidate)(draw->dri_drawable);
+
+   return ret;
+}
+
+int
+loader_dri3_query_buffer_age(struct loader_dri3_drawable *draw)
+{
+   int back_id = LOADER_DRI3_BACK_ID(dri3_find_back(draw));
+
+   if (back_id < 0 || !draw->buffers[back_id])
+      return 0;
+
+   if (draw->buffers[back_id]->last_swap != 0)
+      return draw->send_sbc - draw->buffers[back_id]->last_swap + 1;
+   else
+      return 0;
+}
+
+/** loader_dri3_open
+ *
+ * Wrapper around xcb_dri3_open
+ */
+int
+loader_dri3_open(xcb_connection_t *conn,
+                 xcb_window_t root,
+                 uint32_t provider)
+{
+   xcb_dri3_open_cookie_t       cookie;
+   xcb_dri3_open_reply_t        *reply;
+   int                          fd;
+
+   cookie = xcb_dri3_open(conn,
+                          root,
+                          provider);
+
+   reply = xcb_dri3_open_reply(conn, cookie, NULL);
+   if (!reply)
+      return -1;
+
+   if (reply->nfd != 1) {
+      free(reply);
+      return -1;
+   }
+
+   fd = xcb_dri3_open_reply_fds(conn, reply)[0];
+   fcntl(fd, F_SETFD, fcntl(fd, F_GETFD) | FD_CLOEXEC);
+
+   return fd;
+}
+
+static uint32_t
+dri3_cpp_for_format(uint32_t format) {
+   switch (format) {
+   case  __DRI_IMAGE_FORMAT_R8:
+      return 1;
+   case  __DRI_IMAGE_FORMAT_RGB565:
+   case  __DRI_IMAGE_FORMAT_GR88:
+      return 2;
+   case  __DRI_IMAGE_FORMAT_XRGB8888:
+   case  __DRI_IMAGE_FORMAT_ARGB8888:
+   case  __DRI_IMAGE_FORMAT_ABGR8888:
+   case  __DRI_IMAGE_FORMAT_XBGR8888:
+   case  __DRI_IMAGE_FORMAT_XRGB2101010:
+   case  __DRI_IMAGE_FORMAT_ARGB2101010:
+   case  __DRI_IMAGE_FORMAT_SARGB8:
+      return 4;
+   case  __DRI_IMAGE_FORMAT_NONE:
+   default:
+      return 0;
+   }
+}
+
+/** loader_dri3_alloc_render_buffer
+ *
+ * Use the driver createImage function to construct a __DRIimage, then
+ * get a file descriptor for that and create an X pixmap from that
+ *
+ * Allocate an xshmfence for synchronization
+ */
+static struct loader_dri3_buffer *
+dri3_alloc_render_buffer(struct loader_dri3_drawable *draw, unsigned int format,
+                         int width, int height, int depth)
+{
+   struct loader_dri3_buffer *buffer;
+   __DRIimage *pixmap_buffer;
+   xcb_pixmap_t pixmap;
+   xcb_sync_fence_t sync_fence;
+   struct xshmfence *shm_fence;
+   int buffer_fd, fence_fd;
+   int stride;
+
+   /* Create an xshmfence object and
+    * prepare to send that to the X server
+    */
+
+   fence_fd = xshmfence_alloc_shm();
+   if (fence_fd < 0)
+      return NULL;
+
+   shm_fence = xshmfence_map_shm(fence_fd);
+   if (shm_fence == NULL)
+      goto no_shm_fence;
+
+   /* Allocate the image from the driver
+    */
+   buffer = calloc(1, sizeof *buffer);
+   if (!buffer)
+      goto no_buffer;
+
+   buffer->cpp = dri3_cpp_for_format(format);
+   if (!buffer->cpp)
+      goto no_image;
+
+   if (!draw->is_different_gpu) {
+      buffer->image = (draw->ext->image->createImage)(draw->dri_screen,
+                                                      width, height,
+                                                      format,
+                                                      __DRI_IMAGE_USE_SHARE |
+                                                      __DRI_IMAGE_USE_SCANOUT,
+                                                      buffer);
+      pixmap_buffer = buffer->image;
+
+      if (!buffer->image)
+         goto no_image;
+   } else {
+      buffer->image = (draw->ext->image->createImage)(draw->dri_screen,
+                                                      width, height,
+                                                      format,
+                                                      0,
+                                                      buffer);
+
+      if (!buffer->image)
+         goto no_image;
+
+      buffer->linear_buffer =
+        (draw->ext->image->createImage)(draw->dri_screen,
+                                        width, height, format,
+                                        __DRI_IMAGE_USE_SHARE |
+                                           __DRI_IMAGE_USE_LINEAR,
+                                        buffer);
+      pixmap_buffer = buffer->linear_buffer;
+
+      if (!buffer->linear_buffer)
+         goto no_linear_buffer;
+   }
+
+   /* X wants the stride, so ask the image for it
+    */
+   if (!(draw->ext->image->queryImage)(pixmap_buffer, __DRI_IMAGE_ATTRIB_STRIDE,
+                                       &stride))
+      goto no_buffer_attrib;
+
+   buffer->pitch = stride;
+
+   if (!(draw->ext->image->queryImage)(pixmap_buffer, __DRI_IMAGE_ATTRIB_FD,
+                                       &buffer_fd))
+      goto no_buffer_attrib;
+
+   xcb_dri3_pixmap_from_buffer(draw->conn,
+                               (pixmap = xcb_generate_id(draw->conn)),
+                               draw->drawable,
+                               buffer->size,
+                               width, height, buffer->pitch,
+                               depth, buffer->cpp * 8,
+                               buffer_fd);
+
+   xcb_dri3_fence_from_fd(draw->conn,
+                          pixmap,
+                          (sync_fence = xcb_generate_id(draw->conn)),
+                          false,
+                          fence_fd);
+
+   buffer->pixmap = pixmap;
+   buffer->own_pixmap = true;
+   buffer->sync_fence = sync_fence;
+   buffer->shm_fence = shm_fence;
+   buffer->width = width;
+   buffer->height = height;
+
+   /* Mark the buffer as idle
+    */
+   dri3_fence_set(buffer);
+
+   return buffer;
+
+no_buffer_attrib:
+   (draw->ext->image->destroyImage)(pixmap_buffer);
+no_linear_buffer:
+   if (draw->is_different_gpu)
+      (draw->ext->image->destroyImage)(buffer->image);
+no_image:
+   free(buffer);
+no_buffer:
+   xshmfence_unmap_shm(shm_fence);
+no_shm_fence:
+   close(fence_fd);
+   return NULL;
+}
+
+/** loader_dri3_update_drawable
+ *
+ * Called the first time we use the drawable and then
+ * after we receive present configure notify events to
+ * track the geometry of the drawable
+ */
+static int
+dri3_update_drawable(__DRIdrawable *driDrawable,
+                     struct loader_dri3_drawable *draw)
+{
+   if (draw->first_init) {
+      xcb_get_geometry_cookie_t                 geom_cookie;
+      xcb_get_geometry_reply_t                  *geom_reply;
+      xcb_void_cookie_t                         cookie;
+      xcb_generic_error_t                       *error;
+      xcb_present_query_capabilities_cookie_t   present_capabilities_cookie;
+      xcb_present_query_capabilities_reply_t    *present_capabilities_reply;
+
+      draw->first_init = false;
+
+      /* Try to select for input on the window.
+       *
+       * If the drawable is a window, this will get our events
+       * delivered.
+       *
+       * Otherwise, we'll get a BadWindow error back from this request which
+       * will let us know that the drawable is a pixmap instead.
+       */
+
+      draw->eid = xcb_generate_id(draw->conn);
+      cookie =
+         xcb_present_select_input_checked(draw->conn, draw->eid, draw->drawable,
+                                          XCB_PRESENT_EVENT_MASK_CONFIGURE_NOTIFY |
+                                          XCB_PRESENT_EVENT_MASK_COMPLETE_NOTIFY |
+                                          XCB_PRESENT_EVENT_MASK_IDLE_NOTIFY);
+
+      present_capabilities_cookie =
+         xcb_present_query_capabilities(draw->conn, draw->drawable);
+
+      /* Create an XCB event queue to hold present events outside of the usual
+       * application event queue
+       */
+      draw->special_event = xcb_register_for_special_xge(draw->conn,
+                                                         &xcb_present_id,
+                                                         draw->eid,
+                                                         draw->stamp);
+      geom_cookie = xcb_get_geometry(draw->conn, draw->drawable);
+
+      geom_reply = xcb_get_geometry_reply(draw->conn, geom_cookie, NULL);
+
+      if (!geom_reply)
+         return false;
+
+      draw->width = geom_reply->width;
+      draw->height = geom_reply->height;
+      draw->depth = geom_reply->depth;
+      draw->vtable->set_drawable_size(draw, draw->width, draw->height);
+
+      free(geom_reply);
+
+      draw->is_pixmap = false;
+
+      /* Check to see if our select input call failed. If it failed with a
+       * BadWindow error, then assume the drawable is a pixmap. Destroy the
+       * special event queue created above and mark the drawable as a pixmap
+       */
+
+      error = xcb_request_check(draw->conn, cookie);
+
+      present_capabilities_reply =
+          xcb_present_query_capabilities_reply(draw->conn,
+                                               present_capabilities_cookie,
+                                               NULL);
+
+      if (present_capabilities_reply) {
+         draw->present_capabilities = present_capabilities_reply->capabilities;
+         free(present_capabilities_reply);
+      } else
+         draw->present_capabilities = 0;
+
+      if (error) {
+         if (error->error_code != BadWindow) {
+            free(error);
+            return false;
+         }
+         draw->is_pixmap = true;
+         xcb_unregister_for_special_event(draw->conn, draw->special_event);
+         draw->special_event = NULL;
+      }
+   }
+   dri3_flush_present_events(draw);
+   return true;
+}
+
+/* the DRIimage createImage function takes __DRI_IMAGE_FORMAT codes, while
+ * the createImageFromFds call takes __DRI_IMAGE_FOURCC codes. To avoid
+ * complete confusion, just deal in __DRI_IMAGE_FORMAT codes for now and
+ * translate to __DRI_IMAGE_FOURCC codes in the call to createImageFromFds
+ */
+static int
+image_format_to_fourcc(int format)
+{
+
+   /* Convert from __DRI_IMAGE_FORMAT to __DRI_IMAGE_FOURCC (sigh) */
+   switch (format) {
+   case __DRI_IMAGE_FORMAT_SARGB8: return __DRI_IMAGE_FOURCC_SARGB8888;
+   case __DRI_IMAGE_FORMAT_RGB565: return __DRI_IMAGE_FOURCC_RGB565;
+   case __DRI_IMAGE_FORMAT_XRGB8888: return __DRI_IMAGE_FOURCC_XRGB8888;
+   case __DRI_IMAGE_FORMAT_ARGB8888: return __DRI_IMAGE_FOURCC_ARGB8888;
+   case __DRI_IMAGE_FORMAT_ABGR8888: return __DRI_IMAGE_FOURCC_ABGR8888;
+   case __DRI_IMAGE_FORMAT_XBGR8888: return __DRI_IMAGE_FOURCC_XBGR8888;
+   }
+   return 0;
+}
+
+/** dri3_get_pixmap_buffer
+ *
+ * Get the DRM object for a pixmap from the X server and
+ * wrap that with a __DRIimage structure using createImageFromFds
+ */
+static struct loader_dri3_buffer *
+dri3_get_pixmap_buffer(__DRIdrawable *driDrawable, unsigned int format,
+                       enum loader_dri3_buffer_type buffer_type,
+                       struct loader_dri3_drawable *draw)
+{
+   int                                  buf_id = loader_dri3_pixmap_buf_id(buffer_type);
+   struct loader_dri3_buffer            *buffer = draw->buffers[buf_id];
+   xcb_drawable_t                       pixmap;
+   xcb_dri3_buffer_from_pixmap_cookie_t bp_cookie;
+   xcb_dri3_buffer_from_pixmap_reply_t  *bp_reply;
+   int                                  *fds;
+   xcb_sync_fence_t                     sync_fence;
+   struct xshmfence                     *shm_fence;
+   int                                  fence_fd;
+   __DRIimage                           *image_planar;
+   int                                  stride, offset;
+
+   if (buffer)
+      return buffer;
+
+   pixmap = draw->drawable;
+
+   buffer = calloc(1, sizeof *buffer);
+   if (!buffer)
+      goto no_buffer;
+
+   fence_fd = xshmfence_alloc_shm();
+   if (fence_fd < 0)
+      goto no_fence;
+   shm_fence = xshmfence_map_shm(fence_fd);
+   if (shm_fence == NULL) {
+      close (fence_fd);
+      goto no_fence;
+   }
+
+   xcb_dri3_fence_from_fd(draw->conn,
+                          pixmap,
+                          (sync_fence = xcb_generate_id(draw->conn)),
+                          false,
+                          fence_fd);
+
+   /* Get an FD for the pixmap object
+    */
+   bp_cookie = xcb_dri3_buffer_from_pixmap(draw->conn, pixmap);
+   bp_reply = xcb_dri3_buffer_from_pixmap_reply(draw->conn,
+                                                bp_cookie, NULL);
+   if (!bp_reply)
+      goto no_image;
+   fds = xcb_dri3_buffer_from_pixmap_reply_fds(draw->conn, bp_reply);
+
+   stride = bp_reply->stride;
+   offset = 0;
+
+   /* createImageFromFds creates a wrapper __DRIimage structure which
+    * can deal with multiple planes for things like Yuv images. So, once
+    * we've gotten the planar wrapper, pull the single plane out of it and
+    * discard the wrapper.
+    */
+   image_planar =
+      (draw->ext->image->createImageFromFds)(draw->dri_screen, bp_reply->width,
+                                             bp_reply->height,
+                                             image_format_to_fourcc(format),
+                                             fds, 1, &stride, &offset, buffer);
+   close(fds[0]);
+   if (!image_planar)
+      goto no_image;
+
+   buffer->image = (draw->ext->image->fromPlanar)(image_planar, 0, buffer);
+
+   (draw->ext->image->destroyImage)(image_planar);
+
+   if (!buffer->image)
+      goto no_image;
+
+   buffer->pixmap = pixmap;
+   buffer->own_pixmap = false;
+   buffer->width = bp_reply->width;
+   buffer->height = bp_reply->height;
+   buffer->buffer_type = buffer_type;
+   buffer->shm_fence = shm_fence;
+   buffer->sync_fence = sync_fence;
+
+   draw->buffers[buf_id] = buffer;
+   return buffer;
+
+no_image:
+   xcb_sync_destroy_fence(draw->conn, sync_fence);
+   xshmfence_unmap_shm(shm_fence);
+no_fence:
+   free(buffer);
+no_buffer:
+   return NULL;
+}
+
+/** dri3_get_buffer
+ *
+ * Find a front or back buffer, allocating new ones as necessary
+ */
+static struct loader_dri3_buffer *
+dri3_get_buffer(__DRIdrawable *driDrawable,
+                unsigned int format,
+                enum loader_dri3_buffer_type buffer_type,
+                struct loader_dri3_drawable *draw)
+{
+   struct loader_dri3_buffer *buffer;
+   int buf_id;
+   __DRIcontext *dri_context;
+
+   dri_context = draw->vtable->get_dri_context(draw);
+
+   if (buffer_type == loader_dri3_buffer_back) {
+      buf_id = dri3_find_back(draw);
+
+      if (buf_id < 0)
+         return NULL;
+   } else {
+      buf_id = LOADER_DRI3_FRONT_ID;
+   }
+
+   buffer = draw->buffers[buf_id];
+
+   /* Allocate a new buffer if there isn't an old one, or if that
+    * old one is the wrong size
+    */
+   if (!buffer || buffer->width != draw->width ||
+       buffer->height != draw->height) {
+      struct loader_dri3_buffer *new_buffer;
+
+      /* Allocate the new buffers
+       */
+      new_buffer = dri3_alloc_render_buffer(draw,
+                                                   format,
+                                                   draw->width,
+                                                   draw->height,
+                                                   draw->depth);
+      if (!new_buffer)
+         return NULL;
+
+      /* When resizing, copy the contents of the old buffer, waiting for that
+       * copy to complete using our fences before proceeding
+       */
+      switch (buffer_type) {
+      case loader_dri3_buffer_back:
+         if (buffer) {
+            if (!buffer->linear_buffer) {
+               dri3_fence_reset(draw->conn, new_buffer);
+               dri3_fence_await(draw->conn, buffer);
+               dri3_copy_area(draw->conn,
+                              buffer->pixmap,
+                              new_buffer->pixmap,
+                              dri3_drawable_gc(draw),
+                              0, 0, 0, 0,
+                              draw->width, draw->height);
+               dri3_fence_trigger(draw->conn, new_buffer);
+            } else if (draw->vtable->in_current_context(draw)) {
+               draw->ext->image->blitImage(dri_context,
+                                           new_buffer->image,
+                                           buffer->image,
+                                           0, 0, draw->width, draw->height,
+                                           0, 0, draw->width, draw->height, 0);
+            }
+            dri3_free_render_buffer(draw, buffer);
+         }
+         break;
+      case loader_dri3_buffer_front:
+         dri3_fence_reset(draw->conn, new_buffer);
+         dri3_copy_area(draw->conn,
+                        draw->drawable,
+                        new_buffer->pixmap,
+                        dri3_drawable_gc(draw),
+                        0, 0, 0, 0,
+                        draw->width, draw->height);
+         dri3_fence_trigger(draw->conn, new_buffer);
+
+         if (new_buffer->linear_buffer &&
+             draw->vtable->in_current_context(draw)) {
+            dri3_fence_await(draw->conn, new_buffer);
+            draw->ext->image->blitImage(dri_context,
+                                        new_buffer->image,
+                                        new_buffer->linear_buffer,
+                                        0, 0, draw->width, draw->height,
+                                        0, 0, draw->width, draw->height, 0);
+         }
+         break;
+      }
+      buffer = new_buffer;
+      buffer->buffer_type = buffer_type;
+      draw->buffers[buf_id] = buffer;
+   }
+   dri3_fence_await(draw->conn, buffer);
+
+   /* Return the requested buffer */
+   return buffer;
+}
+
+/** dri3_free_buffers
+ *
+ * Free the front bufffer or all of the back buffers. Used
+ * when the application changes which buffers it needs
+ */
+static void
+dri3_free_buffers(__DRIdrawable *driDrawable,
+                  enum loader_dri3_buffer_type buffer_type,
+                  struct loader_dri3_drawable *draw)
+{
+   struct loader_dri3_buffer *buffer;
+   int first_id;
+   int n_id;
+   int buf_id;
+
+   switch (buffer_type) {
+   case loader_dri3_buffer_back:
+      first_id = LOADER_DRI3_BACK_ID(0);
+      n_id = LOADER_DRI3_MAX_BACK;
+      break;
+   case loader_dri3_buffer_front:
+      first_id = LOADER_DRI3_FRONT_ID;
+      n_id = 1;
+   }
+
+   for (buf_id = first_id; buf_id < first_id + n_id; buf_id++) {
+      buffer = draw->buffers[buf_id];
+      if (buffer) {
+         dri3_free_render_buffer(draw, buffer);
+         draw->buffers[buf_id] = NULL;
+      }
+   }
+}
+
+/** loader_dri3_get_buffers
+ *
+ * The published buffer allocation API.
+ * Returns all of the necessary buffers, allocating
+ * as needed.
+ */
+int
+loader_dri3_get_buffers(__DRIdrawable *driDrawable,
+                        unsigned int format,
+                        uint32_t *stamp,
+                        void *loaderPrivate,
+                        uint32_t buffer_mask,
+                        struct __DRIimageList *buffers)
+{
+   struct loader_dri3_drawable *draw = loaderPrivate;
+   struct loader_dri3_buffer   *front, *back;
+
+   buffers->image_mask = 0;
+   buffers->front = NULL;
+   buffers->back = NULL;
+
+   front = NULL;
+   back = NULL;
+
+   if (!dri3_update_drawable(driDrawable, draw))
+      return false;
+
+   /* pixmaps always have front buffers */
+   if (draw->is_pixmap)
+      buffer_mask |= __DRI_IMAGE_BUFFER_FRONT;
+
+   if (buffer_mask & __DRI_IMAGE_BUFFER_FRONT) {
+      /* All pixmaps are owned by the server gpu.
+       * When we use a different gpu, we can't use the pixmap
+       * as buffer since it is potentially tiled a way
+       * our device can't understand. In this case, use
+       * a fake front buffer. Hopefully the pixmap
+       * content will get synced with the fake front
+       * buffer.
+       */
+      if (draw->is_pixmap && !draw->is_different_gpu)
+         front = dri3_get_pixmap_buffer(driDrawable,
+                                               format,
+                                               loader_dri3_buffer_front,
+                                               draw);
+      else
+         front = dri3_get_buffer(driDrawable,
+                                        format,
+                                        loader_dri3_buffer_front,
+                                        draw);
+
+      if (!front)
+         return false;
+   } else {
+      dri3_free_buffers(driDrawable, loader_dri3_buffer_front, draw);
+      draw->have_fake_front = 0;
+   }
+
+   if (buffer_mask & __DRI_IMAGE_BUFFER_BACK) {
+      back = dri3_get_buffer(driDrawable,
+                                    format,
+                                    loader_dri3_buffer_back,
+                                    draw);
+      if (!back)
+         return false;
+      draw->have_back = 1;
+   } else {
+      dri3_free_buffers(driDrawable, loader_dri3_buffer_back, draw);
+      draw->have_back = 0;
+   }
+
+   if (front) {
+      buffers->image_mask |= __DRI_IMAGE_BUFFER_FRONT;
+      buffers->front = front->image;
+      draw->have_fake_front = draw->is_different_gpu || !draw->is_pixmap;
+   }
+
+   if (back) {
+      buffers->image_mask |= __DRI_IMAGE_BUFFER_BACK;
+      buffers->back = back->image;
+   }
+
+   draw->stamp = stamp;
+
+   return true;
+}