+ 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;
+
+ /* 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.
+ */
+ pipe_buffer_write(st_context(ctx)->pipe,
+ st_obj->buffer,
+ offset, size, data);