src/gallium/drivers/svga/svga_resource_buffer.c - platform/external/mesa3d - Git at Google

 /**********************************************************
  * Copyright 2008-2009 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, 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 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 "svga_cmd.h"

 #include "pipe/p_state.h"
 #include "pipe/p_defines.h"
 #include "util/u_inlines.h"
 #include "os/os_thread.h"
 #include "util/u_math.h"
 #include "util/u_memory.h"

 #include "svga_context.h"
 #include "svga_screen.h"
 #include "svga_resource_buffer.h"
 #include "svga_resource_buffer_upload.h"
 #include "svga_winsys.h"
 #include "svga_debug.h"


 /**
  * Vertex and index buffers need hardware backing.  Constant buffers
  * do not.  No other types of buffers currently supported.
  */
 static INLINE boolean
 svga_buffer_needs_hw_storage(unsigned usage)
 {
    return usage & (PIPE_BIND_VERTEX_BUFFER | PIPE_BIND_INDEX_BUFFER);
 }


 /**
  * Create a buffer transfer.
  *
  * Unlike texture DMAs (which are written immediately to the command buffer and
  * therefore inherently serialized with other context operations), for buffers
  * we try to coalesce multiple range mappings (i.e, multiple calls to this
  * function) into a single DMA command, for better efficiency in command
  * processing.  This means we need to exercise extra care here to ensure that
  * the end result is exactly the same as if one DMA was used for every mapped
  * range.
  */
 static struct pipe_transfer *
 svga_buffer_get_transfer(struct pipe_context *pipe,
                          struct pipe_resource *resource,
                          unsigned level,
                          unsigned usage,
                          const struct pipe_box *box)
 {
    struct svga_context *svga = svga_context(pipe);
    struct svga_screen *ss = svga_screen(pipe->screen);
    struct svga_buffer *sbuf = svga_buffer(resource);
    struct pipe_transfer *transfer;

    transfer = CALLOC_STRUCT(pipe_transfer);
    if (transfer == NULL) {
       return NULL;
    }

    transfer->resource = resource;
    transfer->level = level;
    transfer->usage = usage;
    transfer->box = *box;

    if (usage & PIPE_TRANSFER_WRITE) {
       if (usage & PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE) {
          /*
           * Flush any pending primitives, finish writing any pending DMA
           * commands, and tell the host to discard the buffer contents on
           * the next DMA operation.
           */

          svga_hwtnl_flush_buffer(svga, resource);

          if (sbuf->dma.pending) {
             svga_buffer_upload_flush(svga, sbuf);

             /*
              * Instead of flushing the context command buffer, simply discard
              * the current hwbuf, and start a new one.
              */

             svga_buffer_destroy_hw_storage(ss, sbuf);
          }

          sbuf->map.num_ranges = 0;
          sbuf->dma.flags.discard = TRUE;
       }

       if (usage & PIPE_TRANSFER_UNSYNCHRONIZED) {
          if (!sbuf->map.num_ranges) {
             /*
              * No pending ranges to upload so far, so we can tell the host to
              * not synchronize on the next DMA command.
              */

             sbuf->dma.flags.unsynchronized = TRUE;
          }
       } else {
          /*
           * Synchronizing, so flush any pending primitives, finish writing any
           * pending DMA command, and ensure the next DMA will be done in order.
           */

          svga_hwtnl_flush_buffer(svga, resource);

          if (sbuf->dma.pending) {
             svga_buffer_upload_flush(svga, sbuf);

             if (sbuf->hwbuf) {
                /*
                 * We have a pending DMA upload from a hardware buffer, therefore
                 * we need to ensure that the host finishes processing that DMA
                 * command before the state tracker can start overwriting the
                 * hardware buffer.
                 *
                 * XXX: This could be avoided by tying the hardware buffer to
                 * the transfer (just as done with textures), which would allow
                 * overlapping DMAs commands to be queued on the same context
                 * buffer. However, due to the likelihood of software vertex
                 * processing, it is more convenient to hold on to the hardware
                 * buffer, allowing to quickly access the contents from the CPU
                 * without having to do a DMA download from the host.
                 */

                if (usage & PIPE_TRANSFER_DONTBLOCK) {
                   /*
                    * Flushing the command buffer here will most likely cause
                    * the map of the hwbuf below to block, so preemptively
                    * return NULL here if DONTBLOCK is set to prevent unnecessary
                    * command buffer flushes.
                    */

                   FREE(transfer);
                   return NULL;
                }

                svga_context_flush(svga, NULL);
             }
          }

          sbuf->dma.flags.unsynchronized = FALSE;
       }
    }

    if (!sbuf->swbuf && !sbuf->hwbuf) {
       if (svga_buffer_create_hw_storage(ss, sbuf) != PIPE_OK) {
          /*
           * We can't create a hardware buffer big enough, so create a malloc
           * buffer instead.
           */
          if (0) {
             debug_printf("%s: failed to allocate %u KB of DMA, "
                          "splitting DMA transfers\n",
                          __FUNCTION__,
                          (sbuf->b.b.width0 + 1023)/1024);
          }

          sbuf->swbuf = align_malloc(sbuf->b.b.width0, 16);
          if (!sbuf->swbuf) {
             FREE(transfer);
             return NULL;
          }
       }
    }

    return transfer;
 }


 /**
  * Map a range of a buffer.
  */
 static void *
 svga_buffer_transfer_map( struct pipe_context *pipe,
                           struct pipe_transfer *transfer )
 {
    struct svga_buffer *sbuf = svga_buffer(transfer->resource);

    uint8_t *map;

    if (sbuf->swbuf) {
       /* User/malloc buffer */
       map = sbuf->swbuf;
    }
    else if (sbuf->hwbuf) {
       struct svga_screen *ss = svga_screen(pipe->screen);
       struct svga_winsys_screen *sws = ss->sws;

       map = sws->buffer_map(sws, sbuf->hwbuf, transfer->usage);
    }
    else {
       map = NULL;
    }

    if (map) {
       ++sbuf->map.count;
       map += transfer->box.x;
    }

    return map;
 }


 static void
 svga_buffer_transfer_flush_region( struct pipe_context *pipe,
                                    struct pipe_transfer *transfer,
                                    const struct pipe_box *box)
 {
    struct svga_screen *ss = svga_screen(pipe->screen);
    struct svga_buffer *sbuf = svga_buffer(transfer->resource);

    unsigned offset = transfer->box.x + box->x;
    unsigned length = box->width;

    assert(transfer->usage & PIPE_TRANSFER_WRITE);
    assert(transfer->usage & PIPE_TRANSFER_FLUSH_EXPLICIT);

    pipe_mutex_lock(ss->swc_mutex);
    svga_buffer_add_range(sbuf, offset, offset + length);
    pipe_mutex_unlock(ss->swc_mutex);
 }


 static void
 svga_buffer_transfer_unmap( struct pipe_context *pipe,
                             struct pipe_transfer *transfer )
 {
    struct svga_screen *ss = svga_screen(pipe->screen);
    struct svga_winsys_screen *sws = ss->sws;
    struct svga_buffer *sbuf = svga_buffer(transfer->resource);

    pipe_mutex_lock(ss->swc_mutex);

    assert(sbuf->map.count);
    if (sbuf->map.count) {
       --sbuf->map.count;
    }

    if (sbuf->hwbuf) {
       sws->buffer_unmap(sws, sbuf->hwbuf);
    }

    if (transfer->usage & PIPE_TRANSFER_WRITE) {
       if (!(transfer->usage & PIPE_TRANSFER_FLUSH_EXPLICIT)) {
          /*
           * Mapped range not flushed explicitly, so flush the whole buffer,
           * and tell the host to discard the contents when processing the DMA
           * command.
           */

          SVGA_DBG(DEBUG_DMA, "flushing the whole buffer\n");

          sbuf->dma.flags.discard = TRUE;

          svga_buffer_add_range(sbuf, 0, sbuf->b.b.width0);
       }
    }

    pipe_mutex_unlock(ss->swc_mutex);
 }


 /**
  * Destroy transfer
  */
 static void
 svga_buffer_transfer_destroy(struct pipe_context *pipe,
                              struct pipe_transfer *transfer)
 {
    FREE(transfer);
 }


 static void
 svga_buffer_destroy( struct pipe_screen *screen,
 		     struct pipe_resource *buf )
 {
    struct svga_screen *ss = svga_screen(screen);
    struct svga_buffer *sbuf = svga_buffer( buf );

    assert(!p_atomic_read(&buf->reference.count));

    assert(!sbuf->dma.pending);

    if(sbuf->handle)
       svga_buffer_destroy_host_surface(ss, sbuf);

    if(sbuf->uploaded.buffer)
       pipe_resource_reference(&sbuf->uploaded.buffer, NULL);

    if(sbuf->hwbuf)
       svga_buffer_destroy_hw_storage(ss, sbuf);

    if(sbuf->swbuf && !sbuf->user)
       align_free(sbuf->swbuf);

    FREE(sbuf);
 }


 struct u_resource_vtbl svga_buffer_vtbl =
 {
    u_default_resource_get_handle,      /* get_handle */
    svga_buffer_destroy,		     /* resource_destroy */
    svga_buffer_get_transfer,	     /* get_transfer */
    svga_buffer_transfer_destroy,     /* transfer_destroy */
    svga_buffer_transfer_map,	     /* transfer_map */
    svga_buffer_transfer_flush_region,  /* transfer_flush_region */
    svga_buffer_transfer_unmap,	     /* transfer_unmap */
    u_default_transfer_inline_write   /* transfer_inline_write */
 };


 struct pipe_resource *
 svga_buffer_create(struct pipe_screen *screen,
 		   const struct pipe_resource *template)
 {
    struct svga_screen *ss = svga_screen(screen);
    struct svga_buffer *sbuf;

    sbuf = CALLOC_STRUCT(svga_buffer);
    if(!sbuf)
       goto error1;

    sbuf->b.b = *template;
    sbuf->b.vtbl = &svga_buffer_vtbl;
    pipe_reference_init(&sbuf->b.b.reference, 1);
    sbuf->b.b.screen = screen;

    if(svga_buffer_needs_hw_storage(template->bind)) {
       if(svga_buffer_create_host_surface(ss, sbuf) != PIPE_OK)
          goto error2;
    }
    else {
       sbuf->swbuf = align_malloc(template->width0, 64);
       if(!sbuf->swbuf)
          goto error2;
    }

    debug_reference(&sbuf->b.b.reference,
                    (debug_reference_descriptor)debug_describe_resource, 0);

    return &sbuf->b.b;

 error2:
    FREE(sbuf);
 error1:
    return NULL;
 }

 struct pipe_resource *
 svga_user_buffer_create(struct pipe_screen *screen,
                         void *ptr,
                         unsigned bytes,
 			unsigned bind)
 {
    struct svga_buffer *sbuf;

    sbuf = CALLOC_STRUCT(svga_buffer);
    if(!sbuf)
       goto no_sbuf;

    pipe_reference_init(&sbuf->b.b.reference, 1);
    sbuf->b.vtbl = &svga_buffer_vtbl;
    sbuf->b.b.screen = screen;
    sbuf->b.b.format = PIPE_FORMAT_R8_UNORM; /* ?? */
    sbuf->b.b.usage = PIPE_USAGE_IMMUTABLE;
    sbuf->b.b.bind = bind;
    sbuf->b.b.width0 = bytes;
    sbuf->b.b.height0 = 1;
    sbuf->b.b.depth0 = 1;
    sbuf->b.b.array_size = 1;

    sbuf->swbuf = ptr;
    sbuf->user = TRUE;

    debug_reference(&sbuf->b.b.reference,
                    (debug_reference_descriptor)debug_describe_resource, 0);

    return &sbuf->b.b;

 no_sbuf:
    return NULL;
 }
	/**********************************************************
	* Copyright 2008-2009 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, 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 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 "svga_cmd.h"

	#include "pipe/p_state.h"
	#include "pipe/p_defines.h"
	#include "util/u_inlines.h"
	#include "os/os_thread.h"
	#include "util/u_math.h"
	#include "util/u_memory.h"

	#include "svga_context.h"
	#include "svga_screen.h"
	#include "svga_resource_buffer.h"
	#include "svga_resource_buffer_upload.h"
	#include "svga_winsys.h"
	#include "svga_debug.h"


	/**
	* Vertex and index buffers need hardware backing. Constant buffers
	* do not. No other types of buffers currently supported.
	*/
	static INLINE boolean
	svga_buffer_needs_hw_storage(unsigned usage)
	{
	return usage & (PIPE_BIND_VERTEX_BUFFER \| PIPE_BIND_INDEX_BUFFER);
	}


	/**
	* Create a buffer transfer.
	*
	* Unlike texture DMAs (which are written immediately to the command buffer and
	* therefore inherently serialized with other context operations), for buffers
	* we try to coalesce multiple range mappings (i.e, multiple calls to this
	* function) into a single DMA command, for better efficiency in command
	* processing. This means we need to exercise extra care here to ensure that
	* the end result is exactly the same as if one DMA was used for every mapped
	* range.
	*/
	static struct pipe_transfer *
	svga_buffer_get_transfer(struct pipe_context *pipe,
	struct pipe_resource *resource,
	unsigned level,
	unsigned usage,
	const struct pipe_box *box)
	{
	struct svga_context *svga = svga_context(pipe);
	struct svga_screen *ss = svga_screen(pipe->screen);
	struct svga_buffer *sbuf = svga_buffer(resource);
	struct pipe_transfer *transfer;

	transfer = CALLOC_STRUCT(pipe_transfer);
	if (transfer == NULL) {
	return NULL;
	}

	transfer->resource = resource;
	transfer->level = level;
	transfer->usage = usage;
	transfer->box = *box;

	if (usage & PIPE_TRANSFER_WRITE) {
	if (usage & PIPE_TRANSFER_DISCARD_WHOLE_RESOURCE) {
	/*
	* Flush any pending primitives, finish writing any pending DMA
	* commands, and tell the host to discard the buffer contents on
	* the next DMA operation.
	*/

	svga_hwtnl_flush_buffer(svga, resource);

	if (sbuf->dma.pending) {
	svga_buffer_upload_flush(svga, sbuf);

	/*
	* Instead of flushing the context command buffer, simply discard
	* the current hwbuf, and start a new one.
	*/

	svga_buffer_destroy_hw_storage(ss, sbuf);
	}

	sbuf->map.num_ranges = 0;
	sbuf->dma.flags.discard = TRUE;
	}

	if (usage & PIPE_TRANSFER_UNSYNCHRONIZED) {
	if (!sbuf->map.num_ranges) {
	/*
	* No pending ranges to upload so far, so we can tell the host to
	* not synchronize on the next DMA command.
	*/

	sbuf->dma.flags.unsynchronized = TRUE;
	}
	} else {
	/*
	* Synchronizing, so flush any pending primitives, finish writing any
	* pending DMA command, and ensure the next DMA will be done in order.
	*/

	svga_hwtnl_flush_buffer(svga, resource);

	if (sbuf->dma.pending) {
	svga_buffer_upload_flush(svga, sbuf);

	if (sbuf->hwbuf) {
	/*
	* We have a pending DMA upload from a hardware buffer, therefore
	* we need to ensure that the host finishes processing that DMA
	* command before the state tracker can start overwriting the
	* hardware buffer.
	*
	* XXX: This could be avoided by tying the hardware buffer to
	* the transfer (just as done with textures), which would allow
	* overlapping DMAs commands to be queued on the same context
	* buffer. However, due to the likelihood of software vertex
	* processing, it is more convenient to hold on to the hardware
	* buffer, allowing to quickly access the contents from the CPU
	* without having to do a DMA download from the host.
	*/

	if (usage & PIPE_TRANSFER_DONTBLOCK) {
	/*
	* Flushing the command buffer here will most likely cause
	* the map of the hwbuf below to block, so preemptively
	* return NULL here if DONTBLOCK is set to prevent unnecessary
	* command buffer flushes.
	*/

	FREE(transfer);
	return NULL;
	}

	svga_context_flush(svga, NULL);
	}
	}

	sbuf->dma.flags.unsynchronized = FALSE;
	}
	}

	if (!sbuf->swbuf && !sbuf->hwbuf) {
	if (svga_buffer_create_hw_storage(ss, sbuf) != PIPE_OK) {
	/*
	* We can't create a hardware buffer big enough, so create a malloc
	* buffer instead.
	*/
	if (0) {
	debug_printf("%s: failed to allocate %u KB of DMA, "
	"splitting DMA transfers\n",
	__FUNCTION__,
	(sbuf->b.b.width0 + 1023)/1024);
	}

	sbuf->swbuf = align_malloc(sbuf->b.b.width0, 16);
	if (!sbuf->swbuf) {
	FREE(transfer);
	return NULL;
	}
	}
	}

	return transfer;
	}


	/**
	* Map a range of a buffer.
	*/
	static void *
	svga_buffer_transfer_map( struct pipe_context *pipe,
	struct pipe_transfer *transfer )
	{
	struct svga_buffer *sbuf = svga_buffer(transfer->resource);

	uint8_t *map;

	if (sbuf->swbuf) {
	/* User/malloc buffer */
	map = sbuf->swbuf;
	}
	else if (sbuf->hwbuf) {
	struct svga_screen *ss = svga_screen(pipe->screen);
	struct svga_winsys_screen *sws = ss->sws;

	map = sws->buffer_map(sws, sbuf->hwbuf, transfer->usage);
	}
	else {
	map = NULL;
	}

	if (map) {
	++sbuf->map.count;
	map += transfer->box.x;
	}

	return map;
	}


	static void
	svga_buffer_transfer_flush_region( struct pipe_context *pipe,
	struct pipe_transfer *transfer,
	const struct pipe_box *box)
	{
	struct svga_screen *ss = svga_screen(pipe->screen);
	struct svga_buffer *sbuf = svga_buffer(transfer->resource);

	unsigned offset = transfer->box.x + box->x;
	unsigned length = box->width;

	assert(transfer->usage & PIPE_TRANSFER_WRITE);
	assert(transfer->usage & PIPE_TRANSFER_FLUSH_EXPLICIT);

	pipe_mutex_lock(ss->swc_mutex);
	svga_buffer_add_range(sbuf, offset, offset + length);
	pipe_mutex_unlock(ss->swc_mutex);
	}


	static void
	svga_buffer_transfer_unmap( struct pipe_context *pipe,
	struct pipe_transfer *transfer )
	{
	struct svga_screen *ss = svga_screen(pipe->screen);
	struct svga_winsys_screen *sws = ss->sws;
	struct svga_buffer *sbuf = svga_buffer(transfer->resource);

	pipe_mutex_lock(ss->swc_mutex);

	assert(sbuf->map.count);
	if (sbuf->map.count) {
	--sbuf->map.count;
	}

	if (sbuf->hwbuf) {
	sws->buffer_unmap(sws, sbuf->hwbuf);
	}

	if (transfer->usage & PIPE_TRANSFER_WRITE) {
	if (!(transfer->usage & PIPE_TRANSFER_FLUSH_EXPLICIT)) {
	/*
	* Mapped range not flushed explicitly, so flush the whole buffer,
	* and tell the host to discard the contents when processing the DMA
	* command.
	*/

	SVGA_DBG(DEBUG_DMA, "flushing the whole buffer\n");

	sbuf->dma.flags.discard = TRUE;

	svga_buffer_add_range(sbuf, 0, sbuf->b.b.width0);
	}
	}

	pipe_mutex_unlock(ss->swc_mutex);
	}


	/**
	* Destroy transfer
	*/
	static void
	svga_buffer_transfer_destroy(struct pipe_context *pipe,
	struct pipe_transfer *transfer)
	{
	FREE(transfer);
	}


	static void
	svga_buffer_destroy( struct pipe_screen *screen,
	struct pipe_resource *buf )
	{
	struct svga_screen *ss = svga_screen(screen);
	struct svga_buffer *sbuf = svga_buffer( buf );

	assert(!p_atomic_read(&buf->reference.count));

	assert(!sbuf->dma.pending);

	if(sbuf->handle)
	svga_buffer_destroy_host_surface(ss, sbuf);

	if(sbuf->uploaded.buffer)
	pipe_resource_reference(&sbuf->uploaded.buffer, NULL);

	if(sbuf->hwbuf)
	svga_buffer_destroy_hw_storage(ss, sbuf);

	if(sbuf->swbuf && !sbuf->user)
	align_free(sbuf->swbuf);

	FREE(sbuf);
	}


	struct u_resource_vtbl svga_buffer_vtbl =
	{
	u_default_resource_get_handle, /* get_handle */
	svga_buffer_destroy, /* resource_destroy */
	svga_buffer_get_transfer, /* get_transfer */
	svga_buffer_transfer_destroy, /* transfer_destroy */
	svga_buffer_transfer_map, /* transfer_map */
	svga_buffer_transfer_flush_region, /* transfer_flush_region */
	svga_buffer_transfer_unmap, /* transfer_unmap */
	u_default_transfer_inline_write /* transfer_inline_write */
	};



	struct pipe_resource *
	svga_buffer_create(struct pipe_screen *screen,
	const struct pipe_resource *template)
	{
	struct svga_screen *ss = svga_screen(screen);
	struct svga_buffer *sbuf;

	sbuf = CALLOC_STRUCT(svga_buffer);
	if(!sbuf)
	goto error1;

	sbuf->b.b = *template;
	sbuf->b.vtbl = &svga_buffer_vtbl;
	pipe_reference_init(&sbuf->b.b.reference, 1);
	sbuf->b.b.screen = screen;

	if(svga_buffer_needs_hw_storage(template->bind)) {
	if(svga_buffer_create_host_surface(ss, sbuf) != PIPE_OK)
	goto error2;
	}
	else {
	sbuf->swbuf = align_malloc(template->width0, 64);
	if(!sbuf->swbuf)
	goto error2;
	}

	debug_reference(&sbuf->b.b.reference,
	(debug_reference_descriptor)debug_describe_resource, 0);

	return &sbuf->b.b;

	error2:
	FREE(sbuf);
	error1:
	return NULL;
	}

	struct pipe_resource *
	svga_user_buffer_create(struct pipe_screen *screen,
	void *ptr,
	unsigned bytes,
	unsigned bind)
	{
	struct svga_buffer *sbuf;

	sbuf = CALLOC_STRUCT(svga_buffer);
	if(!sbuf)
	goto no_sbuf;

	pipe_reference_init(&sbuf->b.b.reference, 1);
	sbuf->b.vtbl = &svga_buffer_vtbl;
	sbuf->b.b.screen = screen;
	sbuf->b.b.format = PIPE_FORMAT_R8_UNORM; /* ?? */
	sbuf->b.b.usage = PIPE_USAGE_IMMUTABLE;
	sbuf->b.b.bind = bind;
	sbuf->b.b.width0 = bytes;
	sbuf->b.b.height0 = 1;
	sbuf->b.b.depth0 = 1;
	sbuf->b.b.array_size = 1;

	sbuf->swbuf = ptr;
	sbuf->user = TRUE;

	debug_reference(&sbuf->b.b.reference,
	(debug_reference_descriptor)debug_describe_resource, 0);

	return &sbuf->b.b;

	no_sbuf:
	return NULL;
	}