--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rvinterf/doc/tfc139.usage	Sat Jun 11 00:13:35 2016 +0000
@@ -0,0 +1,38 @@
+The tfc139 hack-utility (see ../../doc/Compal-unlock) is based on the
+rvinterf/rvtdump skeleton, and it needs to be invoked as follows:
+
+tfc139 [options] /dev/ttyXXX
+
+In the well-tested use case of breaking into TFC139 phones with fw version
+8.8.17, no options are normally needed, but the following options are supported:
+
+-a address
+
+	This option changes the RAM address into which the "shellcode" is to be
+	written; the argument is always interpreted as hex.  The default is
+	0x800000, as used by the mot931c.exe closed source tool on whose
+	reverse-engineering our hack-utility is based.
+
+-B baud
+
+	This option changes the serial baud rate just like in rvinterf and
+	rvtdump, but the default is 57600 as needed for breaking into TFC139
+	firmware.
+
+-l logfile
+
+	Log activity in a file, just like rvinterf and rvtdump.
+
+-s address
+
+	Just like mot931c.exe has been observed to do, we start our stack
+	smashing attempts at a certain address, and keep incrementing by 4
+	until we either succeed or crash the fw in some other way that does not
+	help us.  This option changes the starting address for these stack
+	smashing attempts; the argument is always interpreted as hex.  The
+	default is 0x837C54, as observed from the reverse engineering of
+	mot931c.
+
+-w number_in_seconds
+
+	See rvinterf.usage; the option is the same for tfc139 as for rvinterf.