* This function maps a region of a gbm bo for cpu read and/or write
* access.
*
+ * The mapping exposes a linear view of the buffer object even if the buffer
+ * has a non-linear modifier.
+ *
+ * This function may require intermediate buffer copies (ie. it may be slow).
+ *
* \param bo The buffer object
* \param x The X (top left origin) starting position of the mapped region for
* the buffer