Comment 28 for bug 460857

Certainly the driver in the vanilla kernel later than 2.6.31.4 works fine on x86_64.

The Changelog for the latest proposed kernel seems to show the relevant upgrade.

brad@srv:~$ cat /proc/cpuinfo | grep model
model : 2
model name : AMD Phenom(tm) 9750 Quad-Core Processor
<snip>
brad@srv:~$ uname -a
Linux srv 2.6.31.5 #16 SMP Sat Oct 24 12:58:49 WST 2009 x86_64 GNU/Linux
brad@srv:~$ lspci | grep USB
00:0a.0 USB Controller: nVidia Corporation MCP55 USB Controller (rev a1)
00:0a.1 USB Controller: nVidia Corporation MCP55 USB Controller (rev a2)

I don't use an Arduino, I use a Parallax Propeller, but the ftdi device is the same.