[mythtv] Firewire STB keeps jumping ports in 0.21-fixes. Suggestions?

Steven Adeff adeffs.mythtv at gmail.com
Wed Feb 20 21:29:47 UTC 2008

On Feb 17, 2008 9:26 AM, William Munson <w.munson at comcast.net> wrote:
> Daniel Kristjansson wrote:
> > On Sat, 2008-02-16 at 22:03 -0500, William Munson wrote:
> >
> >> First off, sorry to post this to the dev list however I have not gotten
> >> any answers in the users list.
> >>
> >> I am testing the 0.21-fixes branch on ubuntu and am running into a
> >> situation where if I accidentally tune a bad channel with my DCT6416 STB
> >> it will cause the STB to switch ports from 1 to 0 and back again. The
> >> port is still stable and firewire_tester will still capture packets in
> >> broadcast mode just fine however the backend does not realize that the
> >> port has moved even though the UUID is still the same. Am I missing
> >> something or is there a bug that causes the backend end to miss the fact
> >> that the port has changed? What can I do to troubleshoot this and
> >> provide more useful info?
> >>
> >
> > LinuxFirewireDevice::UpdateDeviceListItem() should update the device
> > list when there is a reset, and LinuxFirewireDevice::HandleBusReset()
> > should reconnect the device when it calls iec61883_cmp_reconnect(),
> > but it doesn't always work. The Linux firewire guys weren't too
> > interested in fixing this driver problem when I discovered it (though
> > they were helpful in many ways with the firewire code.) They were
> > working on a new driver which I understand should be immune to these
> > types of problems. I no longer use the firewire recorder, so this is
> > not something I've looked into further.
> >
> > The OSX FirewireRecorder does recover in these instances. But it has
> > it's own problems. The OSX driver devs decided to always issue a bus
> > reset when an application starts or stops using firewire, so you end
> > up losing portions of your recordings if you have more than one STB
> > or have some other firewire devices on the same bus.
> >
> > The upshot is that AFAICT the bug is in the Linux Firewire drivers and
> > not in MythTV; unless you track down the bug in the drivers yourself
> > it is not likely to be fixed until the whole firewire driver stack is
> > replaced with the next generation firewire stack. BUT, it has been a
> > while since I've been on top of this so you might want to read up on
> > the posts in the linux1394-devel at lists.sourceforge.net the next gen
> > driver might be in a usable state at this point, or it might have been
> > abandoned, and/or someone might have written some patches to fix the
> > problem in the existing drivers.
> >
> > Searching the linux1394 mailing list for "bus reset" might give you
> > something useful...
> >
> > -- Daniel
> >
> >
> Thank you for the info. One more question. Is there a location in the
> database that stores the current port? I was thinking of writing a
> channel change script that would take a look at plugreport on each
> channel change and update the database before changing channels. If myth
> looks at this variable when setting up a recording then I could
> dynamically update things whenever I change channel. It would also allow
> me to stabilize the connection if required. This looks to be easier than
> trying to patch the ubuntu 1394 stack.
> TIA,
> William

I have a channel change script that uses the Firewire GUID for the box
in question to change the channel. It doesn't affect the database but
since I've started using it (to fix 0-byte recordings) I've yet to
miss a firewire recording. The downside is you have to manually give
mythtv-setup the GUID of the box in the channel changer field, but
otherwise it works great.



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