This is where I'm going with fwcontrol

[Dieter]

More nit picking  :-)

Should

> Message ID  Root ID  R T Gap Count
>    00(2 bits)  (5 bits)    1 1    (6 bits)

be

Message ID   Root ID    R  T   Gap Count
00(2 bits)   (6 bits)   1  1   (6 bits)

send_phy_config() ANDs root_node with 0x3f, and the
"Physical ID" field in the controller register is
6 bits.