Question How to troublshoot FireWire on Ubuntu 18.04 that crapped out

[cormanaz]

I had been using FireWire on an Ubuntu 16.04 machine to control channel changes on a cable set-top-box. It worked fine for years, then suddenly stopped working. I just upgraded to Ubuntu 18.04 and it is still not working. lspci shows the device is there:

06:07.0 FireWire (IEEE 1394): Texas Instruments TSB43AB23 IEEE-1394a-2000 Controller (PHY/Link)

sudo plugreport gives:

Host Adapter 0
==============

Node 0 GUID 0x00e6bc100000241d
------------------------------
libiec61883 error: error reading oMPR
libiec61883 error: error reading iMPR

If memory serves me, when my setup was working there was a Node 1 where the cable box actually lived.

Searching around on this error led me to an old thread in a redhat bug tracker that says it's a problem with the OS not chowning the firewire device on boot up. When I check permissions on /dev/fw0 I get:

crw------- 1 root root 241, 0 Jul 27 18:31 fw0

That matches what is in the bug report, though I never checked this permission when I had a working system so I don't know if this is really a problem. Also I am on Ubuntu rather than Fedora. Also TBH don't get why the OS would need to chown a device on startup, so I don' t know if this is relevant.

Can anyone advise how to troubleshoot this, or have any guesses what the problem could be?

 

[cormanaz]

I'm fortunate enough to have another Ubuntu box, so I ordered an inexpensive PCI-E firewire card for it, which allowed me to test. On the test box plugreport showed the set-top-box. The card came with a full-size to mini-size firewire cable, which I connected to the other 1394 socket on my original machine, and voila, plugreport on that machine showed the set-top-box. So it seems that either the mini-size socket on my original machine went bad, or the mini-to-mini cable went bad. I have no idea how that can happen to things sitting there undisturbed, but there you have it. So this is SOLVED.

UPDATE: not solved. After 24 hours it reverted to the original situation...plugreport shows a node 0 that it can't access (normal) not not a node 1 with the cable box. Bizarre. I have no idea what is going on.