[Letux-kernel] IP connection to GTA04 to Mac (El Capitan) over USB

H. Nikolaus Schaller hns at goldelico.com
Fri Jul 29 08:55:53 CEST 2016


Hi,
after finding the workaround for twl4030 charging, the ethernet gadget is
now working again.

This allows to connect a GTA04 (or Letux device) through the USB cable
(OTG port) to some host computer and set up an IP connection so that it
is possible to

a) ssh into the GTA04 (no need for serial console, faster, more flexible, easier to use in scripts)
b) ssh from GTA04 to the host (e.g. use its larger X11 screen)
c) scp files between (makes installation of kernel and rootfs patches easier)

But one thing needs additional setup: routing packets from the GTA04
through the host computer to the Internet and backwards.

This is called IP forwarding.

It did work in my setup up to OS X 10.9 (Mavericks) but after upgrading
to OS X 10.11 (El Capitan) it failed. The reason is that the mechanisms
to set up NAT on OS X have completely changed. Now, it is part of the
OpenBSD packet filter (PF).

I have written a wiki page how to set it up:

	http://projects.goldelico.com/p/gta04-kernel/page/EthernetGadget/

It is missing a similar description for a Linux PC (haven't experimented yet)
and some formatting.

With such a setup it is now (again) possible to ssh into the GTA04 and run
an apt-get update or apt-get install on the device.

This allows me to continue to work on the camera driver where I wasn't able
to install the v4l-utils package to control the ISP (Image Signal Processor)
of the DM3730 SoC.

Now the tools are sharp again. Let's start looking into the camera driver...

BR,
Nikolaus


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