Rvinterf (the specific program by this name) is an extended version of rvtdump
(see rvtdump.usage) that decodes and dumps and/or logs any and all output
generated by the firmware running on the target just like rvtdump, but also
creates a local UNIX domain socket on the host machine to which "client"
programs can connect.  "Client" programs connecting to rvinterf via this local
socket interface can:

1. Receive copies of selected RVTMUX packets coming from the target;

2. Send arbitrary RVTMUX packets toward the target.

Rvinterf is invoked just like rvtdump:

rvinterf [options] /dev/ttyXXX

The following options have the same meaning as in rvtdump, see rvtdump.usage
for the details: -b, -B, -d and -l.  The only difference is that -b without -l
is potentially useful and thus allowed.

Additional rvinterf options which don't exist in rvtdump are:

-n

	Suppress the output on stdout like -b, but don't fork into background.
	This option is passed by "client" programs when they invoke rvinterf
	behind the scenes instead of connecting to an already-running rvinterf
	instance.

-s pathname_for_socket

	By default the local UNIX domain socket created by rvinterf is bound to
	/tmp/rvinterf_socket; this option allows any other pathname to be
	specified.

-S <file descriptor number>

	This option is not meant for direct use by human users.  It is passed
	by "client" programs when they invoke rvinterf behind the scenes with
	an unnamed and unbound socket pair instead of conecting to an already-
	running rvinterf instance.

-w number_in_seconds

	It has been discovered experimentally that if an RVTMUX packet is sent
	to a target when the latter is in the "deep sleep" state, the target
	wakes up, but the packet that was sent is not received correctly.  TI's
	reference fw seems to wait for 10 s after last serial activity before
	falling into deep sleep (provided that all other conditions for that
	sleep mode are satisfied), hence the following workaround has been
	implemented in rvinterf: if a packet is to be sent to the target and
	more than a set time has elapsed since the last transmitted packet, the
	packet is preceded by a "wake-up shot" of 64 0 bytes (outside of a
	packet, ignored by the fw) and a 100 ms pause.  This hack is not pretty,
	but it appears to do its job of making RVTMUX communication with target
	firmwares reliable.

	The -w option changes the elapsed time threshold at which the "wake-up
	shot" is sent; the default is 7 s.  Specify -w 0 to disable this hack
	altogether.