[U-Boot] u-boot Atheros AP81 router platform, TP-Link (and others) possible GPL violation?

[Stephen Gutknecht (hilltx)]

Hello,

Atheros makes an AP81 router hardware platform.  Typically it includes:

  CPU: ar9130 or ar9132  (MIPS)
  Wireless:  ar9102 or ar9103
  LAN chips:  mix and match as to the OEM making the board.

So several of these systems have been identified.  Mostly due to the
fact that u-boot emits the message "AP81".  Here is a list I have
compiled for OpenWRT: http://wiki.openwrt.org/AtherosAR9100

All routers to date have found to have a 3.3v ttl rs232 serial port
and u-boot messages can be accessed.  Now from what I understand,
u-boot has to be customised for the various routers to deal with
tftpboot or other firmware loading via u-boot.  this has to have
special code for the particular LAN chip on the unique router board.
On a practical level, this means we can't trade binary u-boot between
routers.

Many of these companies have released GPL files built around Linux
kernel 2.6.15 (now 3 years old) that they run on these routers.
However, I can't seen to find a download of source code for u-boot.
u-boot is indeed GPL, correct?  And u-boot on these routers is making
our job difficult.

Examples of problems we are running into:

Trendnet TEW-652BRP and TEW-632BRP routers.  Trendnet decided to
prevent you from stopping u-boot autoboot.  So we can not tftpboot
this particular router.

Netgear WNR2000.  Netgear added some special flash checksum that makes
using flash filesystem difficult as the checksum differs on each
reboot of the router.  However, you can control the u-boot and do
tftpboot of ramdisk OpenWRT - but we can't flash OpenWRT due to u-boot
checksum they added.

TP-Link TL-WR941N / TL-WR941ND (and suspect earlier 841N model that
uses u-boot).  TP-Link has been asked for a copy of their u-boot
source code and refused.  They do number of things to make OpenWRT
difficult  They give you only one second to type "tp" to gain control
of u-boot.  They have disabled u-boot saveenv all together.  And they
have some special firmware checksum - and to date, we have been
entirely unable to tftpboot OpenWRT like we can on other AP81 routers.

TP-Link is supposed to be the largest router seller in China.  I'm
actively working on this router now, and am stuck due to the issues.
Same with the Netgear.  To see an example of the kind of issue I have
with the TP-Link, see here:

1. special checksum and header required: http://openwrt.pastebin.com/f5fce4294
2. Someone reverse engineered the special checkup and header and we
built our own newer kernel with it, but it still fails to start for
unexplained reasons: http://openwrt.pastebin.com/f74dab33e

Before I approach these companies and claim "GPL Violation" - I wanted
to confirm with this list I'm on solid ground.

As a side note, we at OpenWRT would love assistance trying to work
around the issues with the Netgear and TP-Link issues.  As we know it
can take companies several months to provide source... any assistance
on these MIPS based u-boot would be welcome.  I can even work to give
you SSH access to the serial console for you to tinker directly.  We
are working hard to help get more modern 802.11n Linux routers.

Thank you.

  Stephen Gutknecht
  ~~, Austin Texas Linux Users Group