[mythtv-users] i2c errors (revisited)

[Michael T. Dean]

On 01/08/2012 01:57 PM, Devin Heitmueller wrote:
> On Sun, Jan 8, 2012 at 8:25 AM, Michael T. Dean wrote:
>> On 01/08/2012 06:24 AM, Keith Edmunds wrote:
>>>    - Tuners: 2 x Hauppauge Nova-T Stick (USB) and 1 x PCTV Nanostick 290e
>>>      (also USB)
>> Just a wild guess, but do you have EIT enabled on more than one of the
>> cards? I've heard there are problems with some cards where if EIT is
>> used on multiple cards, it causes the driver/device to "break".  (Don't
>> know any details, though.)
> Wow, that's pretty disturbing if it's true (I'm saying this with my
> "linux-media driver developer" hat).  I guess devices such as the
> Nova-T 500 could be more susceptible to this sort of bug given a
> single i2c master is shared across two tuners, but you definitely
> shouldn't see this sort of issue between two different cards (with
> different i2c masters).
>
> Any links/background you can point me to on this issue would be helpful.
>

I don't know any details.  "Multiple cards" was used in the MythTV 
sense, where it means multiple cards, as defined in the MythTV database 
(which may be the same physical card).  I had never even heard it being 
i2c errors--just "doesn't work with EIT on active on multiple cards."

All I can say for sure is that the reason the setting to enable/disable 
EIT collection on a per-card basis exists is because of issues with some 
cards.  The Nova-T 500 was specifically mentioned:
http://www.gossamer-threads.com/lists/mythtv/commits/313479#313479
but I had never actually seen anyone describe the specific boundaries of 
the issue and what all hardware/drivers/... come into play.  The 
information you provided may actually be the best description of the 
issue I've seen, yet, if it is an i2c thing.

As I said, it was, "Just a wild guess,"--more specifically, it was based 
on seeing DVB-T and Nova in the description and knowing nothing at all 
about the actual hardware/differences (and whether the device may have 
even been a 500 and the OP just didn't provide specific model name or 
whatever--though now I'm guessing the 500 isn't even USB, which means 
someone who knows the hardware would have know that it's not a 500).  :)

Anyway, I guess it's not the problem, here, but I always feel a lot more 
guilty when I don't take a wild guess, and weeks or months later see the 
same user report that he finally determined that it was the issue I 
would have guessed, rather than when I do guess and am wrong.  :)  (And, 
yeah, there have been many times where this happened, and it just seems 
to be a huge waste of time when it happens.)

Sorry I can't provide any real information, but if it's really something 
that's worth investigating, I'm pretty sure some of the UK devs/users 
would be able to help more than I.

Mike