[cups.development] How are the command filters supposed to return data?

[Tim Waugh]

On Wed, 2010-07-14 at 01:43 +0200, Reinhold Kainhofer wrote:
> Okay, that makes sense (unfortunately, it's not documented in the command 
> filter docs at all... Now that you point it out, I found it in the general 
> filter docs, but without any mention of the value format being a comma-
> separated list).

Yes, that could be clearer.

> To get the response of the printer, I have to call cupsBackChannelRead, right?
> Is the data written by the command filter sent to the printer immediately by 
> the backend, or do I need to select some non-zero timeout?

I would have thought it would be sent directly to the printer if
possible, although I don't see anything in the documentation requiring
this explicitly. (IMHO it ought to be required...)

Even so, you may still need a non-zero timeout -- the printer may be
busy and unable to respond at the time (in which case the backend would
be forced to buffer the data I suppose...).

Tim.
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