TiVo Hacking: Getting a Linksys WUSB54G working

So, I have a TiVo Series 2 stand-alone DVR with a Product Lifetime subscription. For years, I’ve had it connected to the home network using a Linksys WUSB11 wireless network adapter, but it finally died. I went and grabbed a Linksys WUSB54G as a replacement, but found out that the TiVo doesn’t support it. No problem, I know the TiVo runs Linux and there’s plenty of documentation on how to “hack” the TiVo so I can load my own kernel modules on it, etc.

It turns out that the Linksys WUSB54G v4 uses the Ralink 2570 chipset. Fortunately, there’s been effort on native Linux drivers for the Ralink family of wireless chipsets. The hurdle, of course, is that the TiVo’s MIPS R5432 is big-endian, so it presents a bit of a challenge porting the driver to the TiVo.

Working off the latest code for the legacy rt2570 driver from CVS, I’ve gotten it to compile using TiVo’s Linux 2.4.20 kernel. Loading the module, however, results in this:

rt2570: init
usb.c: registered new driver rt2570
rt2570: idVendor = 0x13b1, idProduct = 0xd
rt2570: idVendor = 0x13b1, idProduct = 0xd
rt2570: using permanent MAC addr
rt2570: Active MAC addr: 00:12:17:89:f5:02.
rt2570: driver version 1.0.0
Unaligned Access to 0x80230b2b in kernel mode at 0xc0217be4
Unaligned Access to 0x80230b2d in kernel mode at 0xc0217c04
Unaligned Access to 0x80357076 in kernel mode at 0xc021b3dc
Unaligned Access to 0x80357076 in kernel mode at 0xc021b408
Unaligned Access to 0x80357076 in kernel mode at 0xc021dc2c
Unaligned Access to 0x80357076 in kernel mode at 0xc021dc08
Unaligned Access to 0x80357076 in kernel mode at 0xc021cd8c
Unaligned Access to 0x80230f47 in kernel mode at 0xc0217be4
Unaligned Access to 0x80230f49 in kernel mode at 0xc0217c04
Unaligned Access to 0x80231155 in kernel mode at 0xc0217be4
Unaligned Access to 0x80231157 in kernel mode at 0xc0217c04

So, now I get to go fishing through /proc/ksyms and try to fix up all these unaligned access errors. Hopefully, I’ll be able to get through all of this and get the driver working.

Anyone out there have experience porting Linux device drivers like this? Got any tips or techniques that might help me? I’d really love any help I can get …

Update: I’m posting my debugging progress in a rt2x00 forum thread. Given enough eyeballs, all bugs are shallow, right?

Update: I’ve gotten it working! I’ve addressed the majority of the unaligned access traps and I can now use my WUSB54G as a wireless NIC on my TiVo! Here’s a patch against rt2570-cvs-2008102616 of the driver and the corresponding kernel module binary:

• rt2570-tivo-mips.patch
• rt2570.o.gz (1.42 MB)
  MD5: 64605e019929db714d583d160a6b513c

If you have a SA2 TiVo and want to use a Linksys WUSB54G as your wireless NIC, this driver is what you want. It works for me, anyway!

Tags: Linux, TiVo, open source, hacking, Linksys WUSB54G, Ralink 2570