gallium/util: add u_transfer_helper

Add a new helper that drivers can use to emulate various things that
need special handling in particular in transfer_map:

 1) z32_s8x24.. gl/gallium treats this as a single buffer with depth
    and stencil interleaved but hardware frequently treats this as
    separate z32 and s8 buffers.  Special pack/unpack handling is
    needed in transfer_map/unmap to pack/unpack the exposed buffer

 2) fake RGTC.. GPUs designed with GLES in mind, but which can other-
    wise do GL3, if native RGTC is not supported it can be emulated
    by converting to uncompressed internally, but needs pack/unpack
    in transfer_map/unmap

 3) MSAA resolves in the transfer_map() case

v2: add MSAA resolve based on Eric's "gallium: Add helpers for MSAA
    resolves in pipe_transfer_map()/unmap()." patch; avoid wrapping
    pipe_resource, to make it possible for drivers to use both this
    and threaded_context.

Signed-off-by: Rob Clark <[email protected]>

5 files changed, 649 insertions, 1 deletions

diff --git a/src/gallium/auxiliary/Makefile.sources b/src/gallium/auxiliary/Makefile.sources
index f40c4723fae..a2dae04698c 100644
--- a/src/gallium/auxiliary/Makefile.sources
+++ b/src/gallium/auxiliary/Makefile.sources
@@ -304,6 +304,8 @@ C_SOURCES := \
 	util/u_tile.h \
 	util/u_transfer.c \
 	util/u_transfer.h \
+	util/u_transfer_helper.c \
+	util/u_transfer_helper.h \
 	util/u_threaded_context.c \
 	util/u_threaded_context.h \
 	util/u_threaded_context_calls.h \
diff --git a/src/gallium/auxiliary/meson.build b/src/gallium/auxiliary/meson.build
index 4d59f07fd31..584cbe4509c 100644
--- a/src/gallium/auxiliary/meson.build
+++ b/src/gallium/auxiliary/meson.build
@@ -324,6 +324,8 @@ files_libgallium = files(
   'util/u_tile.h',
   'util/u_transfer.c',
   'util/u_transfer.h',
+  'util/u_transfer_helper.c',
+  'util/u_transfer_helper.h',
   'util/u_threaded_context.c',
   'util/u_threaded_context.h',
   'util/u_threaded_context_calls.h',
diff --git a/src/gallium/auxiliary/util/u_transfer_helper.c b/src/gallium/auxiliary/util/u_transfer_helper.c
new file mode 100644
index 00000000000..dd31049920f
--- /dev/null
+++ b/src/gallium/auxiliary/util/u_transfer_helper.c
@@ -0,0 +1,503 @@
+/*
+ * Copyright © 2017 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#include "pipe/p_screen.h"
+
+#include "util/u_box.h"
+#include "util/u_format.h"
+#include "util/u_format_rgtc.h"
+#include "util/u_format_zs.h"
+#include "util/u_inlines.h"
+#include "util/u_transfer_helper.h"
+
+
+struct u_transfer_helper {
+   const struct u_transfer_vtbl *vtbl;
+   bool separate_z32s8;
+   bool fake_rgtc;
+   bool msaa_map;
+};
+
+static inline bool handle_transfer(struct pipe_resource *prsc)
+{
+   struct u_transfer_helper *helper = prsc->screen->transfer_helper;
+
+   if (helper->vtbl->get_internal_format) {
+      enum pipe_format internal_format =
+            helper->vtbl->get_internal_format(prsc);
+      if (internal_format != prsc->format)
+         return true;
+   }
+
+   if (helper->msaa_map && (prsc->nr_samples > 1))
+      return true;
+
+   return false;
+}
+
+/* The pipe_transfer ptr could either be the driver's, or u_transfer,
+ * depending on whether we are intervening or not.  Check handle_transfer()
+ * before dereferencing.
+ */
+struct u_transfer {
+   struct pipe_transfer base;
+   /* Note that in case of MSAA resolve for transfer plus z32s8 or fake rgtc
+    * we end up with stacked u_transfer's.  The MSAA resolve case doesn't call
+    * helper->vtbl fxns directly, but calls back to pctx->transfer_map()/etc
+    * so the format related handling can work in conjunction with MSAA resolve.
+    */
+   struct pipe_transfer *trans;   /* driver's transfer */
+   struct pipe_transfer *trans2;  /* 2nd transfer for s8 stencil buffer in z32s8 */
+   void *ptr, *ptr2;              /* ptr to trans, and trans2 */
+   void *staging;                 /* staging buffer */
+   struct pipe_resource *ss;      /* staging resource for MSAA resolves */
+};
+
+static inline struct u_transfer *
+u_transfer(struct pipe_transfer *ptrans)
+{
+   debug_assert(handle_transfer(ptrans->resource));
+   return (struct u_transfer *)ptrans;
+}
+
+struct pipe_resource *
+u_transfer_helper_resource_create(struct pipe_screen *pscreen,
+                                  const struct pipe_resource *templ)
+{
+   struct u_transfer_helper *helper = pscreen->transfer_helper;
+   enum pipe_format format = templ->format;
+   struct pipe_resource *prsc;
+
+   if ((format == PIPE_FORMAT_Z32_FLOAT_S8X24_UINT) && helper->separate_z32s8) {
+      struct pipe_resource t = *templ;
+      struct pipe_resource *stencil;
+
+      t.format = PIPE_FORMAT_Z32_FLOAT;
+
+      prsc = helper->vtbl->resource_create(pscreen, &t);
+      if (!prsc)
+         return NULL;
+
+      prsc->format = format;  /* frob the format back to the "external" format */
+
+      t.format = PIPE_FORMAT_S8_UINT;
+      stencil = helper->vtbl->resource_create(pscreen, &t);
+
+      if (!stencil) {
+         helper->vtbl->resource_destroy(pscreen, prsc);
+         return NULL;
+      }
+
+      helper->vtbl->set_stencil(prsc, stencil);
+   } else if ((util_format_description(format)->layout == UTIL_FORMAT_LAYOUT_RGTC) &&
+         helper->fake_rgtc) {
+      struct pipe_resource t = *templ;
+      t.format = PIPE_FORMAT_R8G8B8A8_UNORM;
+
+      prsc = helper->vtbl->resource_create(pscreen, &t);
+      if (!prsc)
+         return NULL;
+
+      prsc->format = format;  /* frob the format back to the "external" format */
+   } else {
+      /* normal case, no special handling: */
+      prsc = helper->vtbl->resource_create(pscreen, templ);
+      if (!prsc)
+         return NULL;
+   }
+
+   return prsc;
+}
+
+void
+u_transfer_helper_resource_destroy(struct pipe_screen *pscreen,
+                                   struct pipe_resource *prsc)
+{
+   struct u_transfer_helper *helper = pscreen->transfer_helper;
+
+   if (helper->vtbl->get_stencil) {
+      struct pipe_resource *stencil = helper->vtbl->get_stencil(prsc);
+
+      if (stencil)
+         helper->vtbl->resource_destroy(pscreen, stencil);
+   }
+
+   helper->vtbl->resource_destroy(pscreen, prsc);
+}
+
+static bool needs_pack(unsigned usage)
+{
+   return (usage & PIPE_TRANSFER_READ) &&
+      !(usage & (PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE | PIPE_TRANSFER_DISCARD_RANGE));
+}
+
+/* In the case of transfer_map of a multi-sample resource, call back into
+ * pctx->transfer_map() to map the staging resource, to handle cases of
+ * MSAA + separate_z32s8 or fake_rgtc
+ */
+static void *
+transfer_map_msaa(struct pipe_context *pctx,
+                  struct pipe_resource *prsc,
+                  unsigned level, unsigned usage,
+                  const struct pipe_box *box,
+                  struct pipe_transfer **pptrans)
+{
+   struct pipe_screen *pscreen = pctx->screen;
+   struct u_transfer *trans = calloc(1, sizeof(*trans));
+   if (!trans)
+      return NULL;
+   struct pipe_transfer *ptrans = &trans->base;
+
+   pipe_resource_reference(&ptrans->resource, prsc);
+   ptrans->level = level;
+   ptrans->usage = usage;
+   ptrans->box = *box;
+
+   struct pipe_resource tmpl = {
+         .target = prsc->target,
+         .format = prsc->format,
+         .width0 = box->width,
+         .height0 = box->height,
+         .depth0 = 1,
+         .array_size = 1,
+   };
+   trans->ss = pscreen->resource_create(pscreen, &tmpl);
+   if (!trans->ss) {
+      free(trans);
+      return NULL;
+   }
+
+   if (needs_pack(usage)) {
+      struct pipe_blit_info blit;
+      memset(&blit, 0, sizeof(blit));
+
+      blit.src.resource = ptrans->resource;
+      blit.src.format = ptrans->resource->format;
+      blit.src.level = ptrans->level;
+      blit.src.box = *box;
+
+      blit.dst.resource = trans->ss;
+      blit.dst.format = trans->ss->format;
+      blit.dst.box.width = box->width;
+      blit.dst.box.height = box->height;
+      blit.dst.box.depth = 1;
+
+      blit.mask = util_format_get_mask(prsc->format);
+      blit.filter = PIPE_TEX_FILTER_NEAREST;
+
+      pctx->blit(pctx, &blit);
+   }
+
+   void *ss_map = pctx->transfer_map(pctx, trans->ss, 0, usage, box,
+         &trans->trans);
+   if (!ss_map) {
+      free(trans);
+      return NULL;
+   }
+
+   *pptrans = ptrans;
+   return ss_map;
+}
+
+void *
+u_transfer_helper_transfer_map(struct pipe_context *pctx,
+                               struct pipe_resource *prsc,
+                               unsigned level, unsigned usage,
+                               const struct pipe_box *box,
+                               struct pipe_transfer **pptrans)
+{
+   struct u_transfer_helper *helper = pctx->screen->transfer_helper;
+   struct u_transfer *trans;
+   struct pipe_transfer *ptrans;
+   enum pipe_format format = prsc->format;
+   unsigned width = box->width;
+   unsigned height = box->height;
+
+   if (!handle_transfer(prsc))
+      return helper->vtbl->transfer_map(pctx, prsc, level, usage, box, pptrans);
+
+   if (helper->msaa_map && (prsc->nr_samples > 1))
+      return transfer_map_msaa(pctx, prsc, level, usage, box, pptrans);
+
+   debug_assert(box->depth == 1);
+
+   trans = calloc(1, sizeof(*trans));
+   if (!trans)
+      return NULL;
+
+   ptrans = &trans->base;
+   pipe_resource_reference(&ptrans->resource, prsc);
+   ptrans->level = level;
+   ptrans->usage = usage;
+   ptrans->box   = *box;
+   ptrans->stride = util_format_get_stride(format, box->width);
+   ptrans->layer_stride = ptrans->stride * box->height;
+
+   trans->staging = malloc(ptrans->layer_stride);
+   if (!trans->staging)
+      goto fail;
+
+   trans->ptr = helper->vtbl->transfer_map(pctx, prsc, level, usage, box,
+                                           &trans->trans);
+   if (!trans->ptr)
+      goto fail;
+
+   if (prsc->format == PIPE_FORMAT_Z32_FLOAT_S8X24_UINT) {
+      struct pipe_resource *stencil = helper->vtbl->get_stencil(prsc);
+      trans->ptr2 = helper->vtbl->transfer_map(pctx, stencil, level,
+                                               usage, box, &trans->trans2);
+
+      if (needs_pack(usage)) {
+         util_format_z32_float_s8x24_uint_pack_z_float(trans->staging,
+                                                       ptrans->stride,
+                                                       trans->ptr,
+                                                       trans->trans->stride,
+                                                       width, height);
+         util_format_z32_float_s8x24_uint_pack_s_8uint(trans->staging,
+                                                       ptrans->stride,
+                                                       trans->ptr2,
+                                                       trans->trans2->stride,
+                                                       width, height);
+      }
+   } else if (needs_pack(usage) &&
+              util_format_description(prsc->format)->layout == UTIL_FORMAT_LAYOUT_RGTC) {
+      switch (prsc->format) {
+      case PIPE_FORMAT_RGTC1_UNORM:
+      case PIPE_FORMAT_RGTC1_SNORM:
+      case PIPE_FORMAT_LATC1_UNORM:
+      case PIPE_FORMAT_LATC1_SNORM:
+         util_format_rgtc1_unorm_pack_rgba_8unorm(trans->staging,
+                                                  ptrans->stride,
+                                                  trans->ptr,
+                                                  trans->trans->stride,
+                                                  width, height);
+         break;
+      case PIPE_FORMAT_RGTC2_UNORM:
+      case PIPE_FORMAT_RGTC2_SNORM:
+      case PIPE_FORMAT_LATC2_UNORM:
+      case PIPE_FORMAT_LATC2_SNORM:
+         util_format_rgtc2_unorm_pack_rgba_8unorm(trans->staging,
+                                                  ptrans->stride,
+                                                  trans->ptr,
+                                                  trans->trans->stride,
+                                                  width, height);
+         break;
+      default:
+         assert(!"Unexpected format");
+         break;
+      }
+   } else {
+      unreachable("bleh");
+   }
+
+   *pptrans = ptrans;
+   return trans->staging;
+
+fail:
+   if (trans->trans)
+      helper->vtbl->transfer_unmap(pctx, trans->trans);
+   if (trans->trans2)
+      helper->vtbl->transfer_unmap(pctx, trans->trans2);
+   pipe_resource_reference(&ptrans->resource, NULL);
+   free(trans->staging);
+   free(trans);
+   return NULL;
+}
+
+static void
+flush_region(struct pipe_context *pctx, struct pipe_transfer *ptrans,
+             const struct pipe_box *box)
+{
+   struct u_transfer_helper *helper = pctx->screen->transfer_helper;
+   struct u_transfer *trans = u_transfer(ptrans);
+   enum pipe_format iformat, format = ptrans->resource->format;
+   unsigned width = box->width;
+   unsigned height = box->height;
+   void *src, *dst;
+
+   if (!(ptrans->usage & PIPE_TRANSFER_WRITE))
+      return;
+
+   if (trans->ss) {
+      struct pipe_blit_info blit;
+      memset(&blit, 0, sizeof(blit));
+
+      blit.src.resource = trans->ss;
+      blit.src.format = trans->ss->format;
+      blit.src.box = *box;
+
+      blit.dst.resource = ptrans->resource;
+      blit.dst.format = ptrans->resource->format;
+      blit.dst.level = ptrans->level;
+
+      u_box_2d(ptrans->box.x + box->x,
+               ptrans->box.y + box->y,
+               box->width, box->height,
+               &blit.dst.box);
+
+      blit.mask = util_format_get_mask(ptrans->resource->format);
+      blit.filter = PIPE_TEX_FILTER_NEAREST;
+
+      pctx->blit(pctx, &blit);
+
+      return;
+   }
+
+   iformat = helper->vtbl->get_internal_format(ptrans->resource);
+
+   src = (uint8_t *)trans->staging +
+         (box->y * ptrans->stride) +
+         (box->x * util_format_get_blocksize(format));
+   dst = (uint8_t *)trans->ptr +
+         (box->y * trans->trans->stride) +
+         (box->x * util_format_get_blocksize(iformat));
+
+   switch (format) {
+   case PIPE_FORMAT_Z32_FLOAT_S8X24_UINT:
+      util_format_z32_float_s8x24_uint_unpack_z_float(dst,
+                                                      trans->trans->stride,
+                                                      src,
+                                                      ptrans->stride,
+                                                      width, height);
+      /* fallthru */
+   case PIPE_FORMAT_X32_S8X24_UINT:
+      dst = (uint8_t *)trans->ptr2 +
+            (box->y * trans->trans2->stride) +
+            (box->x * util_format_get_blocksize(PIPE_FORMAT_S8_UINT));
+
+      util_format_z32_float_s8x24_uint_unpack_s_8uint(dst,
+                                                      trans->trans2->stride,
+                                                      src,
+                                                      ptrans->stride,
+                                                      width, height);
+      break;
+   case PIPE_FORMAT_RGTC1_UNORM:
+   case PIPE_FORMAT_RGTC1_SNORM:
+   case PIPE_FORMAT_LATC1_UNORM:
+   case PIPE_FORMAT_LATC1_SNORM:
+      util_format_rgtc1_unorm_unpack_rgba_8unorm(dst,
+                                                 trans->trans->stride,
+                                                 src,
+                                                 ptrans->stride,
+                                                 width, height);
+      break;
+   case PIPE_FORMAT_RGTC2_UNORM:
+   case PIPE_FORMAT_RGTC2_SNORM:
+   case PIPE_FORMAT_LATC2_UNORM:
+   case PIPE_FORMAT_LATC2_SNORM:
+      util_format_rgtc2_unorm_unpack_rgba_8unorm(dst,
+                                                 trans->trans->stride,
+                                                 src,
+                                                 ptrans->stride,
+                                                 width, height);
+      break;
+   default:
+      assert(!"Unexpected staging transfer type");
+      break;
+   }
+}
+
+void
+u_transfer_helper_transfer_flush_region(struct pipe_context *pctx,
+                                        struct pipe_transfer *ptrans,
+                                        const struct pipe_box *box)
+{
+   struct u_transfer_helper *helper = pctx->screen->transfer_helper;
+
+   if (handle_transfer(ptrans->resource)) {
+      struct u_transfer *trans = u_transfer(ptrans);
+
+      flush_region(pctx, ptrans, box);
+
+      /* handle MSAA case, since there could be multiple levels of
+       * wrapped transfer, call pctx->transfer_flush_region()
+       * instead of helper->vtbl->transfer_flush_region()
+       */
+      if (trans->ss) {
+         pctx->transfer_flush_region(pctx, trans->trans, box);
+         return;
+      }
+
+      helper->vtbl->transfer_flush_region(pctx, trans->trans, box);
+      if (trans->trans2)
+         helper->vtbl->transfer_flush_region(pctx, trans->trans2, box);
+
+   } else {
+      helper->vtbl->transfer_flush_region(pctx, ptrans, box);
+   }
+}
+
+void
+u_transfer_helper_transfer_unmap(struct pipe_context *pctx,
+                                 struct pipe_transfer *ptrans)
+{
+   struct u_transfer_helper *helper = pctx->screen->transfer_helper;
+
+   if (handle_transfer(ptrans->resource)) {
+      struct u_transfer *trans = u_transfer(ptrans);
+
+      if (!(ptrans->usage & PIPE_TRANSFER_FLUSH_EXPLICIT)) {
+         struct pipe_box box;
+         u_box_2d(0, 0, ptrans->box.width, ptrans->box.height, &box);
+         flush_region(pctx, ptrans, &box);
+      }
+
+      /* in MSAA case, there could be multiple levels of wrapping
+       * so don't call helper->vtbl->transfer_unmap() directly
+       */
+      if (trans->ss) {
+         pctx->transfer_unmap(pctx, trans->trans);
+         pipe_resource_reference(&trans->ss, NULL);
+      } else {
+         helper->vtbl->transfer_unmap(pctx, trans->trans);
+         if (trans->trans2)
+            helper->vtbl->transfer_unmap(pctx, trans->trans2);
+      }
+
+      free(trans);
+   } else {
+      helper->vtbl->transfer_unmap(pctx, ptrans);
+   }
+}
+
+struct u_transfer_helper *
+u_transfer_helper_create(const struct u_transfer_vtbl *vtbl,
+                         bool separate_z32s8,
+                         bool fake_rgtc,
+                         bool msaa_map)
+{
+   struct u_transfer_helper *helper = calloc(1, sizeof(*helper));
+
+   helper->vtbl = vtbl;
+   helper->separate_z32s8 = separate_z32s8;
+   helper->fake_rgtc = fake_rgtc;
+   helper->msaa_map = msaa_map;
+
+   return helper;
+}
+
+void
+u_transfer_helper_destroy(struct u_transfer_helper *helper)
+{
+   free(helper);
+}
diff --git a/src/gallium/auxiliary/util/u_transfer_helper.h b/src/gallium/auxiliary/util/u_transfer_helper.h
new file mode 100644
index 00000000000..b13a1ec06c1
--- /dev/null
+++ b/src/gallium/auxiliary/util/u_transfer_helper.h
@@ -0,0 +1,135 @@
+/*
+ * Copyright © 2017 Red Hat
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef _U_TRANSFER_HELPER_H
+#define _U_TRANSFER_HELPER_H
+
+#include "pipe/p_state.h"
+#include "pipe/p_context.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* A helper to implement various "lowering" for transfers:
+ *
+ *  - exposing separate z32 and s8 as z32x24s8
+ *  - fake RGTC support for GLES class hardware which needs it to expose GL3+
+ *  - MSAA resolves
+ *
+ * To use this, drivers should:
+ *
+ *  1) populate u_transfer_vtbl and plug that into pipe_screen::transfer_helper
+ *  2) plug the transfer helpers into pipe_screen/pipe_context
+ *
+ * To avoid subclassing pipe_resource (and conflicting with threaded_context)
+ * the vtbl contains setter/getter methods used for fake_rgct & separate_stencil
+ * to access the internal_format and separate stencil buffer.
+ */
+
+struct u_transfer_vtbl {
+   /* NOTE I am not expecting resource_create_from_handle() or
+    * resource_create_with_modifiers() paths to be creating any
+    * resources that need special handling.  Otherwise they would
+    * need to be wrapped too.
+    */
+   struct pipe_resource * (*resource_create)(struct pipe_screen *pscreen,
+                                             const struct pipe_resource *templ);
+
+   void (*resource_destroy)(struct pipe_screen *pscreen,
+                            struct pipe_resource *prsc);
+
+   void *(*transfer_map)(struct pipe_context *pctx,
+                         struct pipe_resource *prsc,
+                         unsigned level,
+                         unsigned usage,
+                         const struct pipe_box *box,
+                         struct pipe_transfer **pptrans);
+
+
+   void (*transfer_flush_region)(struct pipe_context *pctx,
+                                 struct pipe_transfer *ptrans,
+                                 const struct pipe_box *box);
+
+   void (*transfer_unmap)(struct pipe_context *pctx,
+                          struct pipe_transfer *ptrans);
+
+   /*
+    * auxiliary methods to access internal format, stencil:
+    */
+
+   /**
+    * Must be implemented if separate_z32s8 or fake_rgtc is used.  The
+    * internal_format is the format the resource was created with.  In
+    * the case of separate_z32s8 or fake_rgtc, prsc->format is set back
+    * to the state tracker visible format (Z32_FLOAT_S8X24_UINT or
+    * PIPE_FORMAT_{RTGC,LATC}* after the resource is created.
+    */
+   enum pipe_format (*get_internal_format)(struct pipe_resource *prsc);
+
+   /**
+    * Must be implemented if separate_z32s8 is used.  Used to set/get
+    * the separate s8 stencil buffer.
+    *
+    * These two do not get/put references to the pipe_resource.  The
+    * stencil resource will be destroyed by u_transfer_helper_resource_destroy().
+    */
+   void (*set_stencil)(struct pipe_resource *prsc, struct pipe_resource *stencil);
+   struct pipe_resource *(*get_stencil)(struct pipe_resource *prsc);
+};
+
+struct pipe_resource *u_transfer_helper_resource_create(
+      struct pipe_screen *pscreen, const struct pipe_resource *templ);
+
+void u_transfer_helper_resource_destroy(struct pipe_screen *pscreen,
+                                        struct pipe_resource *prsc);
+
+void *u_transfer_helper_transfer_map(struct pipe_context *pctx,
+                                     struct pipe_resource *prsc,
+                                     unsigned level,
+                                     unsigned usage,
+                                     const struct pipe_box *box,
+                                     struct pipe_transfer **pptrans);
+
+
+void u_transfer_helper_transfer_flush_region(struct pipe_context *pctx,
+                                             struct pipe_transfer *ptrans,
+                                             const struct pipe_box *box);
+
+void u_transfer_helper_transfer_unmap(struct pipe_context *pctx,
+                                      struct pipe_transfer *ptrans);
+
+struct u_transfer_helper;
+
+struct u_transfer_helper * u_transfer_helper_create(const struct u_transfer_vtbl *vtbl,
+                                                    bool separate_z32s8,
+                                                    bool fake_rgtc,
+                                                    bool msaa_map);
+
+void u_transfer_helper_destroy(struct u_transfer_helper *helper);
+
+#ifdef __cplusplus
+} // extern "C" {
+#endif
+
+#endif /* _U_TRANSFER_HELPER_H */
diff --git a/src/gallium/include/pipe/p_screen.h b/src/gallium/include/pipe/p_screen.h
index c249c7d63b4..101e229088b 100644
--- a/src/gallium/include/pipe/p_screen.h
+++ b/src/gallium/include/pipe/p_screen.h
@@ -60,7 +60,7 @@ struct pipe_box;
 struct pipe_memory_info;
 struct disk_cache;
 struct driOptionCache;
-
+struct u_transfer_helper;
 
 /**
  * Gallium screen/adapter context.  Basically everything
@@ -68,6 +68,12 @@ struct driOptionCache;
  * context.
  */
 struct pipe_screen {
+
+   /**
+    * For drivers using u_transfer_helper:
+    */
+   struct u_transfer_helper *transfer_helper;
+
    void (*destroy)( struct pipe_screen * );
 
    const char *(*get_name)( struct pipe_screen * );