On Sat, 14 Nov 2009, Alan Stern wrote:
On Sat, 14 Nov 2009, Oliver Neukum wrote:
Am Samstag, 14. November 2009 18:47:04 schrieb Alan Stern:
The other is that the camera really is sending empty data packets.
Then one has to figure out why the camera behaves differently in the
two environments; presumably only the manufacturers have enough
information to make that determination.
Indeed. Therefore this route may be an unproductive path.
I agree. And I agree that it's looking more and more as though the
differences in schedulng between ohci-hcd and uhci-hcd are somehow
responsible. But the usbmon traces show each URB ending at exactly the
expected time, which means the scheduling is as it should be. And it's
hard to see how the driver could think that a packet contained 0 bytes
when it actually contained more.
A bus analyzer would at least help narrow down the search space.
Alan,
As much as I have gotten into this kind of thing, it would probably be
very nice if I had access to a bus analyser. But, please see the message
that I just sent in, replying to Oliver.
Basically, it seems that there is a specific command which I was not
sending, which sets up a timing circuit. So the problem seems to be
solved. More details about how this could have happened, in the other
message.
Thanks.
Theodore Kilgore
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