TRAU mux: add some comment to the source of the gsm_fr_map
diff --git a/openbsc/src/libtrau/trau_mux.c b/openbsc/src/libtrau/trau_mux.c
index b8b90bd..b2c630c 100644
--- a/openbsc/src/libtrau/trau_mux.c
+++ b/openbsc/src/libtrau/trau_mux.c
@@ -30,7 +30,9 @@
#include <openbsc/debug.h>
#include <osmocom/core/talloc.h>
-uint8_t gsm_fr_map[] = {
+/* this corresponds to teh bit-lengths of the individual codec
+ * parameters as indicated in Table 1.1 of TS 06.10 */
+static const uint8_t gsm_fr_map[] = {
6, 6, 5, 5, 4, 4, 3, 3,
7, 2, 2, 6, 3, 3, 3, 3,
3, 3, 3, 3, 3, 3, 3, 3,