--- a/sh/c139-gen-fc-ffs-img	Sat Jun 10 08:16:10 2023 +0000
+++ b/sh/c139-gen-fc-ffs-img	Sat Jun 10 23:20:44 2023 +0000
@@ -1,5 +1,13 @@
 #!/bin/sh
 
+# This shell script generates an fc-ffs.bin image specifically for FreeCalypso
+# on C139.  It contains hard-coded FFS geometry of 64x7 (correct for 4 MiB
+# flash only, FC Tourmaline), and it invokes c139-gen-fc-ffs-tree script to
+# populate the FFS content.  The latter script is intended to be C139-specific:
+# it uses aud-c139 audio mode config files, and in the future it will also
+# populate PWT buzzer melodies that aren't applicable to other C1xx targets
+# (too small FFS on C11x and no buzzer on C155).
+
 if [ $# != 2 ]
 then
 	echo "usage: $0 rfbin-dir imei-file" 1>&2