gallium: New PIPE_BUFFER_USAGE_FLUSH_EXPLICIT flag for buffer_flush_mapped_range.

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.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/gallium/include/pipe/p_inlines.h b/src/gallium/include/pipe/p_inlines.h
index 1232c87968..cf176c9209 100644
--- a/src/gallium/include/pipe/p_inlines.h
+++ b/src/gallium/include/pipe/p_inlines.h
@@ -117,7 +117,9 @@ pipe_buffer_write(struct pipe_screen *screen,
    assert(offset + size <= buf->size);
    assert(size);
 
-   map = pipe_buffer_map_range(screen, buf, offset, size, PIPE_BUFFER_USAGE_CPU_WRITE);
+   map = pipe_buffer_map_range(screen, buf, offset, size, 
+                               PIPE_BUFFER_USAGE_CPU_WRITE | 
+                               PIPE_BUFFER_USAGE_FLUSH_EXPLICIT);
    assert(map);
    if(map) {
       memcpy(map + offset, data, size);