gallium: fix behavior of pipe_buffer_map_range

To match what transfer_map returns. Really, subtracting the offset leads
to bugs if someone expects it to work exactly like transfer_map.

Reviewed-by: Brian Paul <[email protected]>

1 files changed, 6 insertions, 5 deletions

diff --git a/src/mesa/state_tracker/st_draw.c b/src/mesa/state_tracker/st_draw.c
index a21160c956d..6d6fc858de4 100644
--- a/src/mesa/state_tracker/st_draw.c
+++ b/src/mesa/state_tracker/st_draw.c
@@ -824,16 +824,17 @@ handle_fallback_primitive_restart(struct pipe_context *pipe,
                                   start * ibuffer->index_size, /* start */
                                   count * ibuffer->index_size, /* length */
                                   PIPE_TRANSFER_READ, &transfer);
+      if (!ptr)
+         return;
+
+      ptr = (uint8_t*)ptr + (ibuffer->offset - start * ibuffer->index_size);
    }
    else {
       ptr = ib->ptr;
+      if (!ptr)
+         return;
    }
 
-   if (!ptr)
-      return;
-
-   ptr = ADD_POINTERS(ptr, ibuffer->offset);
-
    sub_prims = find_sub_primitives(ptr, ibuffer->index_size,
                                    0, count, orig_info->restart_index,
                                    &num_sub_prims);