mesa/state_tracker/st_cb_bufferobjects.c

/**************************************************************************
 *
 * Copyright 2007 VMware, Inc.
 * All Rights Reserved.
 *
 * 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, sub license, 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 NON-INFRINGEMENT.
 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS 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.
 *
 **************************************************************************/


/**
 * Functions for pixel buffer objects and vertex/element buffer objects.
 */


#include <inttypes.h>  /* for PRId64 macro */

#include "main/errors.h"

#include "main/mtypes.h"
#include "main/arrayobj.h"
#include "main/bufferobj.h"

#include "st_context.h"
#include "st_cb_bufferobjects.h"
#include "st_cb_memoryobjects.h"
#include "st_debug.h"
#include "st_util.h"

#include "pipe/p_context.h"
#include "pipe/p_defines.h"
#include "util/u_inlines.h"


/**
 * There is some duplication between mesa's bufferobjects and our
 * bufmgr buffers.  Both have an integer handle and a hashtable to
 * lookup an opaque structure.  It would be nice if the handles and
 * internal structure where somehow shared.
 */
static struct gl_buffer_object *
st_bufferobj_alloc(struct gl_context *ctx, GLuint name)
{
   struct st_buffer_object *st_obj = ST_CALLOC_STRUCT(st_buffer_object);

   if (!st_obj)
      return NULL;

   _mesa_initialize_buffer_object(ctx, &st_obj->Base, name);

   return &st_obj->Base;
}


static void
release_buffer(struct gl_buffer_object *obj)
{
   struct st_buffer_object *st_obj = st_buffer_object(obj);

   if (!st_obj->buffer)
      return;

   /* Subtract the remaining private references before unreferencing
    * the buffer. See the header file for explanation.
    */
   if (st_obj->private_refcount) {
      assert(st_obj->private_refcount > 0);
      p_atomic_add(&st_obj->buffer->reference.count,
                   -st_obj->private_refcount);
      st_obj->private_refcount = 0;
   }
   st_obj->ctx = NULL;

   pipe_resource_reference(&st_obj->buffer, NULL);
}


/**
 * Deallocate/free a vertex/pixel buffer object.
 * Called via glDeleteBuffersARB().
 */
static void
st_bufferobj_free(struct gl_context *ctx, struct gl_buffer_object *obj)
{
   assert(obj->RefCount == 0);
   _mesa_buffer_unmap_all_mappings(ctx, obj);
   release_buffer(obj);
   _mesa_delete_buffer_object(ctx, obj);
}


/**
 * Replace data in a subrange of buffer object.  If the data range
 * specified by size + offset extends beyond the end of the buffer or
 * if data is NULL, no copy is performed.
 * Called via glBufferSubDataARB().
 */
static void
st_bufferobj_subdata(struct gl_context *ctx,
                     GLintptrARB offset,
                     GLsizeiptrARB size,
                     const void * data, struct gl_buffer_object *obj)
{
   struct st_buffer_object *st_obj = st_buffer_object(obj);

   /* we may be called from VBO code, so double-check params here */
   assert(offset >= 0);
   assert(size >= 0);
   assert(offset + size <= obj->Size);

   if (!size)
      return;

   /*
    * According to ARB_vertex_buffer_object specification, if data is null,
    * then the contents of the buffer object's data store is undefined. We just
    * ignore, and leave it unchanged.
    */
   if (!data)
      return;

   if (!st_obj->buffer) {
      /* we probably ran out of memory during buffer allocation */
      return;
   }

   /* Now that transfers are per-context, we don't have to figure out
    * flushing here.  Usually drivers won't need to flush in this case
    * even if the buffer is currently referenced by hardware - they
    * just queue the upload as dma rather than mapping the underlying
    * buffer directly.
    *
    * If the buffer is mapped, suppress implicit buffer range invalidation
    * by using PIPE_MAP_DIRECTLY.
    */
   struct pipe_context *pipe = st_context(ctx)->pipe;

   pipe->buffer_subdata(pipe, st_obj->buffer,
                        _mesa_bufferobj_mapped(obj, MAP_USER) ?
                           PIPE_MAP_DIRECTLY : 0,
                        offset, size, data);
}


/**
 * Called via glGetBufferSubDataARB().
 */
static void
st_bufferobj_get_subdata(struct gl_context *ctx,
                         GLintptrARB offset,
                         GLsizeiptrARB size,
                         void * data, struct gl_buffer_object *obj)
{
   struct st_buffer_object *st_obj = st_buffer_object(obj);

   /* we may be called from VBO code, so double-check params here */
   assert(offset >= 0);
   assert(size >= 0);
   assert(offset + size <= obj->Size);

   if (!size)
      return;

   if (!st_obj->buffer) {
      /* we probably ran out of memory during buffer allocation */
      return;
   }

   pipe_buffer_read(st_context(ctx)->pipe, st_obj->buffer,
                    offset, size, data);
}


/**
 * Return bitmask of PIPE_BIND_x flags corresponding a GL buffer target.
 */
static unsigned
buffer_target_to_bind_flags(GLenum target)
{
   switch (target) {
   case GL_PIXEL_PACK_BUFFER_ARB:
   case GL_PIXEL_UNPACK_BUFFER_ARB:
      return PIPE_BIND_RENDER_TARGET | PIPE_BIND_SAMPLER_VIEW;
   case GL_ARRAY_BUFFER_ARB:
      return PIPE_BIND_VERTEX_BUFFER;
   case GL_ELEMENT_ARRAY_BUFFER_ARB:
      return PIPE_BIND_INDEX_BUFFER;
   case GL_TEXTURE_BUFFER:
      return PIPE_BIND_SAMPLER_VIEW;
   case GL_TRANSFORM_FEEDBACK_BUFFER:
      return PIPE_BIND_STREAM_OUTPUT;
   case GL_UNIFORM_BUFFER:
      return PIPE_BIND_CONSTANT_BUFFER;
   case GL_DRAW_INDIRECT_BUFFER:
   case GL_PARAMETER_BUFFER_ARB:
      return PIPE_BIND_COMMAND_ARGS_BUFFER;
   case GL_ATOMIC_COUNTER_BUFFER:
   case GL_SHADER_STORAGE_BUFFER:
      return PIPE_BIND_SHADER_BUFFER;
   case GL_QUERY_BUFFER:
      return PIPE_BIND_QUERY_BUFFER;
   default:
      return 0;
   }
}


/**
 * Return bitmask of PIPE_RESOURCE_x flags corresponding to GL_MAP_x flags.
 */
static unsigned
storage_flags_to_buffer_flags(GLbitfield storageFlags)
{
   unsigned flags = 0;
   if (storageFlags & GL_MAP_PERSISTENT_BIT)
      flags |= PIPE_RESOURCE_FLAG_MAP_PERSISTENT;
   if (storageFlags & GL_MAP_COHERENT_BIT)
      flags |= PIPE_RESOURCE_FLAG_MAP_COHERENT;
   if (storageFlags & GL_SPARSE_STORAGE_BIT_ARB)
      flags |= PIPE_RESOURCE_FLAG_SPARSE;
   return flags;
}


/**
 * From a buffer object's target, immutability flag, storage flags and
 * usage hint, return a pipe_resource_usage value (PIPE_USAGE_DYNAMIC,
 * STREAM, etc).
 */
static enum pipe_resource_usage
buffer_usage(GLenum target, GLboolean immutable,
             GLbitfield storageFlags, GLenum usage)
{
   /* "immutable" means that "storageFlags" was set by the user and "usage"
    * was guessed by Mesa. Otherwise, "usage" was set by the user and
    * storageFlags was guessed by Mesa.
    *
    * Therefore, use storageFlags with immutable, else use "usage".
    */
   if (immutable) {
      /* BufferStorage */
      if (storageFlags & GL_MAP_READ_BIT)
         return PIPE_USAGE_STAGING;
      else if (storageFlags & GL_CLIENT_STORAGE_BIT)
         return PIPE_USAGE_STREAM;
      else
         return PIPE_USAGE_DEFAULT;
   }
   else {
      /* These are often read by the CPU, so enable CPU caches. */
      if (target == GL_PIXEL_PACK_BUFFER ||
          target == GL_PIXEL_UNPACK_BUFFER)
         return PIPE_USAGE_STAGING;

      /* BufferData */
      switch (usage) {
      case GL_DYNAMIC_DRAW:
      case GL_DYNAMIC_COPY:
         return PIPE_USAGE_DYNAMIC;
      case GL_STREAM_DRAW:
      case GL_STREAM_COPY:
         return PIPE_USAGE_STREAM;
      case GL_STATIC_READ:
      case GL_DYNAMIC_READ:
      case GL_STREAM_READ:
         return PIPE_USAGE_STAGING;
      case GL_STATIC_DRAW:
      case GL_STATIC_COPY:
      default:
         return PIPE_USAGE_DEFAULT;
      }
   }
}


static ALWAYS_INLINE GLboolean
bufferobj_data(struct gl_context *ctx,
               GLenum target,
               GLsizeiptrARB size,
               const void *data,
               struct gl_memory_object *memObj,
               GLuint64 offset,
               GLenum usage,
               GLbitfield storageFlags,
               struct gl_buffer_object *obj)
{
   struct st_context *st = st_context(ctx);
   struct pipe_context *pipe = st->pipe;
   struct pipe_screen *screen = st->screen;
   struct st_buffer_object *st_obj = st_buffer_object(obj);
   struct st_memory_object *st_mem_obj = st_memory_object(memObj);
   bool is_mapped = _mesa_bufferobj_mapped(obj, MAP_USER);

   if (size > UINT32_MAX || offset > UINT32_MAX) {
      /* pipe_resource.width0 is 32 bits only and increasing it
       * to 64 bits doesn't make much sense since hw support
       * for > 4GB resources is limited.
       */
      st_obj->Base.Size = 0;
      return GL_FALSE;
   }

   if (target != GL_EXTERNAL_VIRTUAL_MEMORY_BUFFER_AMD &&
       size && st_obj->buffer &&
       st_obj->Base.Size == size &&
       st_obj->Base.Usage == usage &&
       st_obj->Base.StorageFlags == storageFlags) {
      if (data) {
         /* Just discard the old contents and write new data.
          * This should be the same as creating a new buffer, but we avoid
          * a lot of validation in Mesa.
          *
          * If the buffer is mapped, we can't discard it.
          *
          * PIPE_MAP_DIRECTLY supresses implicit buffer range
          * invalidation.
          */
         pipe->buffer_subdata(pipe, st_obj->buffer,
                              is_mapped ? PIPE_MAP_DIRECTLY :
                                          PIPE_MAP_DISCARD_WHOLE_RESOURCE,
                              0, size, data);
         return GL_TRUE;
      } else if (is_mapped) {
         return GL_TRUE; /* can't reallocate, nothing to do */
      } else if (screen->get_param(screen, PIPE_CAP_INVALIDATE_BUFFER)) {
         pipe->invalidate_resource(pipe, st_obj->buffer);
         return GL_TRUE;
      }
   }

   st_obj->Base.Size = size;
   st_obj->Base.Usage = usage;
   st_obj->Base.StorageFlags = storageFlags;

   release_buffer(obj);

   const unsigned bindings = buffer_target_to_bind_flags(target);

   if (ST_DEBUG & DEBUG_BUFFER) {
      debug_printf("Create buffer size %" PRId64 " bind 0x%x\n",
                   (int64_t) size, bindings);
   }

   if (size != 0) {
      struct pipe_resource buffer;

      memset(&buffer, 0, sizeof buffer);
      buffer.target = PIPE_BUFFER;
      buffer.format = PIPE_FORMAT_R8_UNORM; /* want TYPELESS or similar */
      buffer.bind = bindings;
      buffer.usage =
         buffer_usage(target, st_obj->Base.Immutable, storageFlags, usage);
      buffer.flags = storage_flags_to_buffer_flags(storageFlags);
      buffer.width0 = size;
      buffer.height0 = 1;
      buffer.depth0 = 1;
      buffer.array_size = 1;

      if (st_mem_obj) {
         st_obj->buffer = screen->resource_from_memobj(screen, &buffer,
                                                       st_mem_obj->memory,
                                                       offset);
      }
      else if (target == GL_EXTERNAL_VIRTUAL_MEMORY_BUFFER_AMD) {
         st_obj->buffer =
            screen->resource_from_user_memory(screen, &buffer, (void*)data);
      }
      else {
         st_obj->buffer = screen->resource_create(screen, &buffer);

         if (st_obj->buffer && data)
            pipe_buffer_write(pipe, st_obj->buffer, 0, size, data);
      }

      if (!st_obj->buffer) {
         /* out of memory */
         st_obj->Base.Size = 0;
         return GL_FALSE;
      }

      st_obj->ctx = ctx;
   }

   /* The current buffer may be bound, so we have to revalidate all atoms that
    * might be using it.
    */
   if (st_obj->Base.UsageHistory & USAGE_ARRAY_BUFFER)
      ctx->NewDriverState |= ST_NEW_VERTEX_ARRAYS;
   /* if (st_obj->Base.UsageHistory & USAGE_ELEMENT_ARRAY_BUFFER) */
   /*    ctx->NewDriverState |= TODO: Handle indices as gallium state; */
   if (st_obj->Base.UsageHistory & USAGE_UNIFORM_BUFFER)
      ctx->NewDriverState |= ST_NEW_UNIFORM_BUFFER;
   if (st_obj->Base.UsageHistory & USAGE_SHADER_STORAGE_BUFFER)
      ctx->NewDriverState |= ST_NEW_STORAGE_BUFFER;
   if (st_obj->Base.UsageHistory & USAGE_TEXTURE_BUFFER)
      ctx->NewDriverState |= ST_NEW_SAMPLER_VIEWS | ST_NEW_IMAGE_UNITS;
   if (st_obj->Base.UsageHistory & USAGE_ATOMIC_COUNTER_BUFFER)
      ctx->NewDriverState |= ctx->DriverFlags.NewAtomicBuffer;

   return GL_TRUE;
}

/**
 * Allocate space for and store data in a buffer object.  Any data that was
 * previously stored in the buffer object is lost.  If data is NULL,
 * memory will be allocated, but no copy will occur.
 * Called via ctx->Driver.BufferData().
 * \return GL_TRUE for success, GL_FALSE if out of memory
 */
static GLboolean
st_bufferobj_data(struct gl_context *ctx,
                  GLenum target,
                  GLsizeiptrARB size,
                  const void *data,
                  GLenum usage,
                  GLbitfield storageFlags,
                  struct gl_buffer_object *obj)
{
   return bufferobj_data(ctx, target, size, data, NULL, 0, usage, storageFlags, obj);
}

static GLboolean
st_bufferobj_data_mem(struct gl_context *ctx,
                      GLenum target,
                      GLsizeiptrARB size,
                      struct gl_memory_object *memObj,
                      GLuint64 offset,
                      GLenum usage,
                      struct gl_buffer_object *bufObj)
{
   return bufferobj_data(ctx, target, size, NULL, memObj, offset, usage, 0, bufObj);
}

/**
 * Called via glInvalidateBuffer(Sub)Data.
 */
static void
st_bufferobj_invalidate(struct gl_context *ctx,
                        struct gl_buffer_object *obj,
                        GLintptr offset,
                        GLsizeiptr size)
{
   struct st_context *st = st_context(ctx);
   struct pipe_context *pipe = st->pipe;
   struct st_buffer_object *st_obj = st_buffer_object(obj);

   /* We ignore partial invalidates. */
   if (offset != 0 || size != obj->Size)
      return;

   /* If the buffer is mapped, we can't invalidate it. */
   if (!st_obj->buffer || _mesa_bufferobj_mapped(obj, MAP_USER))
      return;

   pipe->invalidate_resource(pipe, st_obj->buffer);
}


/**
 * Convert GLbitfield of GL_MAP_x flags to gallium pipe_map_flags flags.
 * \param wholeBuffer  is the whole buffer being mapped?
 */
enum pipe_map_flags
st_access_flags_to_transfer_flags(GLbitfield access, bool wholeBuffer)
{
   enum pipe_map_flags flags = 0;

   if (access & GL_MAP_WRITE_BIT)
      flags |= PIPE_MAP_WRITE;

   if (access & GL_MAP_READ_BIT)
      flags |= PIPE_MAP_READ;

   if (access & GL_MAP_FLUSH_EXPLICIT_BIT)
      flags |= PIPE_MAP_FLUSH_EXPLICIT;

   if (access & GL_MAP_INVALIDATE_BUFFER_BIT) {
      flags |= PIPE_MAP_DISCARD_WHOLE_RESOURCE;
   }
   else if (access & GL_MAP_INVALIDATE_RANGE_BIT) {
      if (wholeBuffer)
         flags |= PIPE_MAP_DISCARD_WHOLE_RESOURCE;
      else
         flags |= PIPE_MAP_DISCARD_RANGE;
   }

   if (access & GL_MAP_UNSYNCHRONIZED_BIT)
      flags |= PIPE_MAP_UNSYNCHRONIZED;

   if (access & GL_MAP_PERSISTENT_BIT)
      flags |= PIPE_MAP_PERSISTENT;

   if (access & GL_MAP_COHERENT_BIT)
      flags |= PIPE_MAP_COHERENT;

   /* ... other flags ...
   */

   if (access & MESA_MAP_NOWAIT_BIT)
      flags |= PIPE_MAP_DONTBLOCK;
   if (access & MESA_MAP_THREAD_SAFE_BIT)
      flags |= PIPE_MAP_THREAD_SAFE;
   if (access & MESA_MAP_ONCE)
      flags |= PIPE_MAP_ONCE;

   return flags;
}


/**
 * Called via glMapBufferRange().
 */
static void *
st_bufferobj_map_range(struct gl_context *ctx,
                       GLintptr offset, GLsizeiptr length, GLbitfield access,
                       struct gl_buffer_object *obj,
                       gl_map_buffer_index index)
{
   struct pipe_context *pipe = st_context(ctx)->pipe;
   struct st_buffer_object *st_obj = st_buffer_object(obj);

   assert(offset >= 0);
   assert(length >= 0);
   assert(offset < obj->Size);
   assert(offset + length <= obj->Size);

   enum pipe_map_flags transfer_flags =
      st_access_flags_to_transfer_flags(access,
                                        offset == 0 && length == obj->Size);

   /* Sometimes games do silly things like MapBufferRange(UNSYNC|DISCARD_RANGE)
    * In this case, the the UNSYNC is a bit redundant, but the games rely
    * on the driver rebinding/replacing the backing storage rather than
    * going down the UNSYNC path (ie. honoring DISCARD_x first before UNSYNC).
    */
   if (unlikely(st_context(ctx)->options.ignore_map_unsynchronized)) {
      if (transfer_flags & (PIPE_MAP_DISCARD_RANGE | PIPE_MAP_DISCARD_WHOLE_RESOURCE))
         transfer_flags &= ~PIPE_MAP_UNSYNCHRONIZED;
   }

   obj->Mappings[index].Pointer = pipe_buffer_map_range(pipe,
                                                        st_obj->buffer,
                                                        offset, length,
                                                        transfer_flags,
                                                        &st_obj->transfer[index]);
   if (obj->Mappings[index].Pointer) {
      obj->Mappings[index].Offset = offset;
      obj->Mappings[index].Length = length;
      obj->Mappings[index].AccessFlags = access;
   }
   else {
      st_obj->transfer[index] = NULL;
   }

   return obj->Mappings[index].Pointer;
}


static void
st_bufferobj_flush_mapped_range(struct gl_context *ctx,
                                GLintptr offset, GLsizeiptr length,
                                struct gl_buffer_object *obj,
                                gl_map_buffer_index index)
{
   struct pipe_context *pipe = st_context(ctx)->pipe;
   struct st_buffer_object *st_obj = st_buffer_object(obj);

   /* Subrange is relative to mapped range */
   assert(offset >= 0);
   assert(length >= 0);
   assert(offset + length <= obj->Mappings[index].Length);
   assert(obj->Mappings[index].Pointer);

   if (!length)
      return;

   pipe_buffer_flush_mapped_range(pipe, st_obj->transfer[index],
                                  obj->Mappings[index].Offset + offset,
                                  length);
}


/**
 * Called via glUnmapBufferARB().
 */
static GLboolean
st_bufferobj_unmap(struct gl_context *ctx, struct gl_buffer_object *obj,
                   gl_map_buffer_index index)
{
   struct pipe_context *pipe = st_context(ctx)->pipe;
   struct st_buffer_object *st_obj = st_buffer_object(obj);

   if (obj->Mappings[index].Length)
      pipe_buffer_unmap(pipe, st_obj->transfer[index]);

   st_obj->transfer[index] = NULL;
   obj->Mappings[index].Pointer = NULL;
   obj->Mappings[index].Offset = 0;
   obj->Mappings[index].Length = 0;
   return GL_TRUE;
}


/**
 * Called via glCopyBufferSubData().
 */
static void
st_copy_buffer_subdata(struct gl_context *ctx,
                       struct gl_buffer_object *src,
                       struct gl_buffer_object *dst,
                       GLintptr readOffset, GLintptr writeOffset,
                       GLsizeiptr size)
{
   struct pipe_context *pipe = st_context(ctx)->pipe;
   struct st_buffer_object *srcObj = st_buffer_object(src);
   struct st_buffer_object *dstObj = st_buffer_object(dst);
   struct pipe_box box;

   if (!size)
      return;

   /* buffer should not already be mapped */
   assert(!_mesa_check_disallowed_mapping(src));
   /* dst can be mapped, just not the same range as the target range */

   u_box_1d(readOffset, size, &box);

   pipe->resource_copy_region(pipe, dstObj->buffer, 0, writeOffset, 0, 0,
                              srcObj->buffer, 0, &box);
}

/**
 * Called via glClearBufferSubData().
 */
static void
st_clear_buffer_subdata(struct gl_context *ctx,
                        GLintptr offset, GLsizeiptr size,
                        const void *clearValue,
                        GLsizeiptr clearValueSize,
                        struct gl_buffer_object *bufObj)
{
   struct pipe_context *pipe = st_context(ctx)->pipe;
   struct st_buffer_object *buf = st_buffer_object(bufObj);
   static const char zeros[16] = {0};

   if (!pipe->clear_buffer) {
      _mesa_ClearBufferSubData_sw(ctx, offset, size,
                                  clearValue, clearValueSize, bufObj);
      return;
   }

   if (!clearValue)
      clearValue = zeros;

   pipe->clear_buffer(pipe, buf->buffer, offset, size,
                      clearValue, clearValueSize);
}

static void
st_bufferobj_page_commitment(struct gl_context *ctx,
                             struct gl_buffer_object *bufferObj,
                             GLintptr offset, GLsizeiptr size,
                             GLboolean commit)
{
   struct pipe_context *pipe = st_context(ctx)->pipe;
   struct st_buffer_object *buf = st_buffer_object(bufferObj);
   struct pipe_box box;

   u_box_1d(offset, size, &box);

   if (!pipe->resource_commit(pipe, buf->buffer, 0, &box, commit)) {
      _mesa_error(ctx, GL_OUT_OF_MEMORY, "glBufferPageCommitmentARB(out of memory)");
      return;
   }
}

void
st_init_bufferobject_functions(struct pipe_screen *screen,
                               struct dd_function_table *functions)
{
   functions->NewBufferObject = st_bufferobj_alloc;
   functions->DeleteBuffer = st_bufferobj_free;
   functions->BufferData = st_bufferobj_data;
   functions->BufferDataMem = st_bufferobj_data_mem;
   functions->BufferSubData = st_bufferobj_subdata;
   functions->GetBufferSubData = st_bufferobj_get_subdata;
   functions->MapBufferRange = st_bufferobj_map_range;
   functions->FlushMappedBufferRange = st_bufferobj_flush_mapped_range;
   functions->UnmapBuffer = st_bufferobj_unmap;
   functions->CopyBufferSubData = st_copy_buffer_subdata;
   functions->ClearBufferSubData = st_clear_buffer_subdata;
   functions->BufferPageCommitment = st_bufferobj_page_commitment;

   if (screen->get_param(screen, PIPE_CAP_INVALIDATE_BUFFER))
      functions->InvalidateBufferSubData = st_bufferobj_invalidate;
}