Added the FTDI cable pinout for reference.
diff --git a/iceprog/iceprog.c b/iceprog/iceprog.c
index 42abd86..7029f00 100644
--- a/iceprog/iceprog.c
+++ b/iceprog/iceprog.c
@@ -40,6 +40,19 @@
// MPSSE / FTDI definitions
// ---------------------------------------------------------
+/* FTDI bank pinout typically used for iCE dev boards
+ * BUS IO | Signal | Control
+ * -------+--------+--------------
+ * xDBUS0 | SCK | MPSSE
+ * xDBUS1 | MOSI | MPSSE
+ * xDBUS2 | MISO | MPSSE
+ * xDBUS3 | nc |
+ * xDBUS4 | CS | GPIO
+ * xDBUS5 | nc |
+ * xDBUS6 | CDONE | GPIO
+ * xDBUS7 | CRESET | GPIO
+ */
+
static struct ftdi_context ftdic;
static bool ftdic_open = false;
static bool verbose = false;
