This function used to return a pointer to where the start of the
actual buffer would have been, even though only the requested range is
being mapped.

In the resources change, the function was modified to use a transfer
internally, and started returning the pointer to the beginning of the
transfer, ie the mapped range.

Some users of the function were changed to reflect this new behaviour,
some were not.  Since then the function has reverted to its original
behaviour, matching master.

This change restores some of the users of the map_buffer_range helper
to expect the old/original behaviour.

Work in progress...

Helper code in an aux module to avoid rewriting all the drivers.

There was very little use for this beyond permitting the
pipe_context::tex_transfer_destroy() function to omit the pipe_context
argument.

This change adds the pipe_context argument into tex_transfer_destroy()
so that it looks like other pipe_context functions, and removes the
pipe_context pointer from pipe_transfer.

commit 7a2ee04629
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Mar 11 14:19:17 2010 +0000

    nv: convert to context transfers

commit 188a3f5331
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Mar 11 14:11:10 2010 +0000

    nouveau: remove unused variable

commit 5c8e880ab4
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Mar 11 12:31:21 2010 +0000

    mesa/st: fix compilation after merge

commit c552595333
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Mar 11 12:31:06 2010 +0000

    util: fix compilation after merge

commit e80836878a
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Mar 11 12:30:47 2010 +0000

    r300g: fix compilation after merge

commit 0e4883e951
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Mar 11 12:18:45 2010 +0000

    i965g: fix incorrect merge

commit 17d74133d8
Merge: cb81c79 aa311ae
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Mar 11 12:08:32 2010 +0000

    Merge commit 'origin/master' into gallium-context-transfers

    Conflicts:
    	src/gallium/drivers/i965/brw_screen_texture.c
    	src/gallium/drivers/r300/r300_screen.c
    	src/gallium/drivers/softpipe/sp_texture.c
    	src/gallium/drivers/svga/svga_screen_texture.c
    	src/gallium/state_trackers/egl/x11/native_ximage.c

commit cb81c79098
Author: Keith Whitwell <keithw@vmware.com>
Date:   Tue Mar 2 16:04:01 2010 +0000

    egl/x11: hack for context transfers

    There is a better approach to this in the winsys-handle branch, but
    for now avoid using transfers at all by always allocating our own
    backing store directly.

commit f44a24e1d4
Author: Keith Whitwell <keithw@vmware.com>
Date:   Tue Mar 2 16:03:16 2010 +0000

    llvmpipe: context transfers

commit 4d7475ef81
Author: Keith Whitwell <keithw@vmware.com>
Date:   Tue Mar 2 16:02:50 2010 +0000

    llvmpipe: disable testprogs build

    Not working.

commit a9bf98c4d3
Merge: ee0f97e 0c616da
Author: Keith Whitwell <keithw@vmware.com>
Date:   Tue Mar 2 15:28:25 2010 +0000

    Merge commit 'origin/master' into gallium-context-transfers

    Conflicts:
    	src/mesa/state_tracker/st_cb_accum.c
    	src/mesa/state_tracker/st_cb_bitmap.c

commit ee0f97e8d9
Merge: a7f078e 828f545
Author: Keith Whitwell <keithw@vmware.com>
Date:   Fri Feb 19 13:00:29 2010 +0000

    Merge commit 'origin/master' into gallium-context-transfers

    Conflicts:
    	src/gallium/auxiliary/util/u_debug.h
    	src/gallium/drivers/i915/i915_context.h
    	src/gallium/drivers/llvmpipe/lp_flush.c
    	src/gallium/drivers/nv30/nv30_screen.h
    	src/gallium/drivers/nv40/nv40_context.h
    	src/gallium/drivers/nv40/nv40_screen.h
    	src/gallium/drivers/nv50/nv50_context.h
    	src/gallium/drivers/r300/r300_screen.c
    	src/gallium/drivers/r300/r300_winsys.h
    	src/gallium/drivers/softpipe/sp_context.c
    	src/gallium/drivers/trace/tr_context.c
    	src/gallium/state_trackers/dri/dri_context.c
    	src/gallium/state_trackers/egl/common/egl_g3d.c
    	src/gallium/state_trackers/python/st_device.c
    	src/gallium/winsys/drm/radeon/core/radeon_drm.c

commit a7f078e16d
Author: Keith Whitwell <keithw@vmware.com>
Date:   Fri Feb 5 14:16:11 2010 +0000

    gallium: move texture transfers to pipe_context

commit 7b2ffc2019
Merge: 51e190e c036d13
Author: Keith Whitwell <keithw@vmware.com>
Date:   Fri Feb 5 09:55:02 2010 +0000

    Merge commit 'origin/master' into gallium-screen-context

    Conflicts:
    	src/gallium/winsys/drm/nouveau/drm/nouveau_drm_api.c

    This branch has got a pretty tortured history now, I expect
    a squash merge will be appropriate when it is done.

commit 51e190e95a
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 17:58:02 2010 +0000

    gallium: fix some build issues

commit f524bdaa72
Merge: f906212 3aba0a2
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 17:51:32 2010 +0000

    Merge commit 'origin/master' into gallium-screen-context

commit f906212688
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 17:17:12 2010 +0000

    gallium/docs: small description of screen::create_context

commit efcb37bd3d
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:42:42 2010 +0000

    drm/radeon: more dead create_context wrapper removal

commit 6badc0dd9e
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:42:30 2010 +0000

    drm/i965: more dead create_context wrapper removal

commit cf04ebd5a5
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:42:05 2010 +0000

    st/python: more dead create_context wrapper removal

commit 444f114c35
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:37:58 2010 +0000

    idenity: wrapped context creation

commit 5a6d09cb9e
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:28:47 2010 +0000

    ws/gdi: remove dead context_create wrapper

commit 132b55f4be
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:27:52 2010 +0000

    ws/gdi: remove dead context_create wrapper

commit 56d2d21a0c
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:25:38 2010 +0000

    st/xorg: use screen::context_create

commit 838c5cfe56
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:23:20 2010 +0000

    glx/xlib: simplify creation of trace-wrapped contexts

    Trace screen knows how to properly wrap context creation in the
    wrapped screen, so nothing special to do here.

commit c99404c03e
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:18:24 2010 +0000

    st/python: no need to special case context creation for trace

commit 193a527a68
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:15:30 2010 +0000

    drm/radeon: remove dead create_context declaration

commit bb984eecc2
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:14:58 2010 +0000

    nv/drm: remove dead create_context ref

commit e809313a44
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:12:51 2010 +0000

    st/egl: remove a layer of wrappers around screen::create_context

commit 39caa6672a
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:05:28 2010 +0000

    r300g: fill in screen::context_create

commit 407f12556d
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 16:04:04 2010 +0000

    cell: adapt for screen::create_context, untested

commit d02b0c6ce3
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 15:50:24 2010 +0000

    drm/nv: adapt for screen::create_context

    All contexts now created directly through the screen, so remove
    equivalent code here.

    Remove apparently un-needed array of contexts in the winsys.

commit 53eec5b134
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 15:50:08 2010 +0000

    stw: adapt for screen::create_context, untested

commit c6a64de3eb
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 15:49:20 2010 +0000

    trace: expose the wrapped context's priv data

    If we are going to keep this priv idea, really want an accessor
    function for it so that trace and other drivers can wrap that.

commit 75d6104e11
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 15:47:55 2010 +0000

    nv30: adapt to screen::context_create

commit 12f5deb6ed
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 15:44:47 2010 +0000

    nv40: adapt to screen::context_create

commit 14baccaa3b
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 15:35:27 2010 +0000

    nv50: adapt to screen::create_context

    Not build tested.  Need to figure out how to build nouveau.

commit a0e94505cc
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 15:22:27 2010 +0000

    llvmpipe: update for screen::create_context, untested

commit 0eae17107c
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 15:16:57 2010 +0000

    xlib/llvmpipe: remove dead winsys context creation path

commit 2f69f9ffaa
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 14:58:27 2010 +0000

    gallium: convert most code to use screen::create_context

    I wish I could build all of gallium at once to find breakages.

commit d7b57f4061
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 12:46:21 2010 +0000

    glx: permit building with older protocol headers

    I'd like to be able to build mesa on current distro releases without
    having to upgrade from the standard dri2proto and glproto headers.  With
    this change I'm able to build on ancient releases such as Ubuntu 9-10...

    In general, it would be nice to be able to build-test mesa to check for
    unintended breakages without having to follow the external dependencies
    of every group working on the codebase.

commit 57adedd6fb
Merge: da71847 e1906ae
Author: Keith Whitwell <keithw@vmware.com>
Date:   Thu Feb 4 11:38:15 2010 +0000

    Merge commit 'origin/master' into gallium-screen-context

    Conflicts:
    	src/gallium/drivers/softpipe/sp_video_context.h
    	src/gallium/drivers/trace/tr_context.c
    	src/gallium/state_trackers/wgl/shared/stw_context.c
    	src/gallium/winsys/gdi/gdi_softpipe_winsys.c

commit da71847ea6
Author: José Fonseca <jfonseca@vmware.com>
Date:   Sat May 2 08:57:39 2009 +0100

    wgl: Use pipe_screen::context_create.

commit 2595a188f9
Author: José Fonseca <jfonseca@vmware.com>
Date:   Sat May 2 08:56:47 2009 +0100

    trace: Implement pipe_screen::context_create.

commit f3640e4ae3
Author: José Fonseca <jfonseca@vmware.com>
Date:   Sat May 2 08:56:17 2009 +0100

    softpipe: Implement pipe_screen::context_create.

commit 347266bddc
Author: José Fonseca <jfonseca@vmware.com>
Date:   Sat May 2 08:55:31 2009 +0100

    gallium: New pipe_screen::context_create callback.

Into os/os_thread.h and util/u_atomic.h respectively.

PIPE_BUFFER_USAGE_DISCARD flag now exists.

Always test for PIPE_TRANSFER_READ/WRITE using the bit-wise and operator, and
add a pipe_transfer_buffer_flags() helper for getting the buffer usage flags
corresponding to them.

This prevents the driver from discarding a buffer when the whole buffer
is mapped for writing, but only a portion is effectively written.

This is a temporary fix, because WRITE shouldn't imply DISCARD.

The full fix implies using PIPE_BUFFER_USAGE_DISCARD, throughout
the code, and will go only into master.

When a buffer was mapped for write and no explicit flush range was provided
the existing semantics were that the whole buffer would be flushed, mostly
for backwards compatability with non map-buffer-range aware code.

However if the buffer was mapped/unmapped with nothing really written --
something that often happens with the vbo -- we were unnecessarily assuming
that the whole buffer was written.

The new PIPE_BUFFER_USAGE_FLUSH_EXPLICIT flag (based from ARB_map_buffer_range
's GL_MAP_FLUSH_EXPLICIT_BIT flag) allows to clearly distinguish the
legacy usage from the nothing written usage.

Which are slightly different from ARB_map_buffer_range semantics, since
gallium still supports more than one mapping of the same buffer.

The core reference counting code is centralized in p_refcnt.h.

This has some consequences related to struct pipe_buffer:

* The screen member of struct pipe_buffer must be initialized, or
  pipe_buffer_reference() will crash trying to destroy a buffer with reference
  count 0. u_simple_screen takes care of this, but I may have missed some of
  the drivers not using it.
* Except for rare exceptions deep in winsys code, buffers must always be
  allocated via pipe_buffer_create() or via screen->*buffer_create() rather
  than via winsys->*buffer_create().

This allows the pipe driver to do more efficient DMA upload/downloads, by
avoiding to read/write unneeded/unmodified data.

Saves code, and will simplify future interface changes.

Instead, a new pipe_transfer object has to be created and mapped for
transferring data between the CPU and a texture. This gives the driver more
flexibility for textures in address spaces that aren't CPU accessible.

This is a first pass; softpipe/xlib builds and runs glxgears, but it only shows
a black window. Looks like something's off related to the Z buffer, so the
depth test always fails.

move it to pipe/internal/p_winsys_screen.h and start converting
the state trackers to the screen usage

allows the driver to overwrite buffer allocation, first step on the way
to making winsys interface internal to the drivers. state trackers and
the code above it will go through the screen

This commit is mostly just a cosmetic change that cleans-up the interfaces,
replacing pipe_winsys::surface_* calls by

   /**
    * Allocate storage for a display target surface.
    *
    * Often surfaces which are meant to be blitted to the front screen (i.e.,
    * display targets) must be allocated with special characteristics, memory
    * pools, or obtained directly from the windowing system.
    *
    * This callback is invoked by the pipe_screenwhen creating a texture marked
    * with the PIPE_TEXTURE_USAGE_DISPLAY_TARGET flag  to get the underlying
    * buffer storage.
    */
   struct pipe_buffer *(*surface_buffer_create)(struct pipe_winsys *ws,
                                        unsigned width, unsigned height,
                                        enum pipe_format format,
                                        unsigned usage,
                                        unsigned *stride);

Most drivers were updated but not all were tested. Use the softpipe pipe
driver and the xlib winsys changes as a reference when fixing other drivers.

We want to use the pipe_buffer_* inlines everywhere, but a pipe context
is not always available nor is it needed.

These functions are now per-screen, not per-context.

This will allow creating textures before a rendering context exists, for example.
Only implemented in i915 driver for now.  i915pipe->texture_create() just
dispatches through to the i915screen->texture_create() to avoid state tracker
changes for now.

Added pipe field to pipe_texture (temporary, see comments).
First step toward context-less texture creation...