[mythtv] an update on SVN firewire recordings

Daniel Kristjansson danielk at cuymedia.net
Sun Jun 24 17:47:33 UTC 2007

On Sat, 2007-06-23 at 17:10 -0400, Steven Adeff wrote:
> On 6/23/07, Jim Westfall <jwestfall at surrealistic.net> wrote:
> > Steven Adeff <adeffs.mythtv at gmail.com> wrote [06.23.07]:
> > > I've finally finished my move and got my mythtv backend up and running
> > > again. I've got two DCT6200 boxes daisy chained to one firewire port
> > > on my motherboard.
> > >
> > > A while back Daniel mentioned commenting a  line out to do a bus
> > > reset, which I've done. The problem is I still see some recordings not
> > > working after a bus reset. If I happen to be around and paying
> > > attention I can run firewire_tester -B, sometimes a few times, to get
> > > it to work, but the firewire recording code doesn't seem to have the
> > > same ability?
> >
> > You dont want to have the reset code enabled if you have 2+ STBs.  It
> > resets all devices on the firewire bus, which while fixing one STB it
> > will cause the other to break.  You can end up with 2 recorder threads
> > fighting trying to fix their STB, but in doing so breaking the other.
> well, there should to be a way to get the firewire_tester "fix" code
> into the backend then or one tuner can just sit there not outputting
> anything and the backend does nothing but wait for it to start
> streaming data, which it won't.

The code in MythTV that you enabled does basically what
firewire_tester does. The reason it is disabled by default
is because Linux drivers don't like it if there is another
bus master on the bus that tries to do bandwidth allocation,
so we end up having to do multiple bus resets to actually
reset the bus. With one bandwidth allocating device on
the bus we need two resets. I don't know how many we need
with 2,3,4,etc.

I no longer have a FireWire STB so I'm not likely to be
improving this. If you have one firewire recorder you
can enable the automatic resets, but if you have more
than one firewire recorder on the same bus YMMV.

The Linux drivers may improve, one of the firewire guys is
writing a completely new driver from scratch that will do
bandwidth allocation. But this may take several years and
he's only planning to support the newest firewire chips.

-- Daniel

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