Backchannel data missing

[Michael Sweet]

keens312 wrote:
> ...
> In my knowledge, the data from USB should go to Apple IOKit at first, then CUPS system, then my filter.
> 
> Could you give me some suggestion about how to debug this or get the log about bachchannel?

Unfortunately, there aren't a whole lot of debug options with the
current USB backend, however you might try posting this question to
the Apple printing list as the engineer that does the USB code does
read that list.

In general, make sure that your back-channel code handles reading all
pending data on a regular basis - the pipe is non-blocking and will
drop new data if you don't read it.

-- 
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Michael Sweet, Easy Software Products           mike at easysw dot com