Re: inconsistent Self-ID

Stefan Richter wrote:
> On 4 Mar, Dai Yuwen wrote:
>
>>I have a Sony DCR-TRV 38E DV. When I connect it to the
>>firewire 1394 card on my PC, using dvgrab to capture vedio,
>>there're endless messages saying:
>>OHCI.o: inconsistent self-ID [0Xxxxxxxxx/0Xxxxxxxxx]
>>
>>then the system hangs. So, what does the above info mean?
>
>
> Self-ID (self identification) packets are sent by all nodes
> shortly after a bus reset. (A bus reset occurs for example when a
> device is added or disconnected.) Either does the camera create
> incorrect self-ID packets, or the cabling is defective, or the
> host adapter is unable to receive them correctly. Your host
> adapter VT6306 is however supported by Linux. (I own one myself
> but don't use it for video apps.)
>
> The check in ohci1394 that returns the "SelfID is inconsistent"
> message simply compares the 1st half of each packet with the
> second half. The standard requires that the 2nd is the binary
> inverse of the 1st. That is, the packets were either defective in
> the firts place or were corrupted during transmission or
> reception.
>
> But the system (the kernel at least) should not hang because of
> this.

Stefan,
    I completely agree with you and he should check the two quadlet to
be inverses of each other, or close but a corrupted bit ot something.
That would clearly be a failure.

    The one other thing I can think of that might effect this would be
that during Iso time it's possible that a transmitting device will send
an Iso packet with no payload. This packet will be 2 quadlets only. It's
important that the stack check *any* 2 quadlet packet to see if it is 1)
A Self-ID or 2) An Iso packet with no data payload. Is it possible that
this is a properly formated Iso packet with a data payload of 0, but the
stack has a corner condition problem in the code that isn't recognizing it?

    Just a thought.

Cheers,
Mark

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Received on Thu Mar 4 23:36:07 2004