[cups.bugs] [HIGH] STR #2019: Since the advent of back-channel API, Minolta USB printer hasn't worked properly.

[Johannes Meixner]

Hello,

On Oct 9 13:51 Andrej Podzimek wrote (shortened):
> Printer: Konica Minolta PagePro 1300W (GDI, low-end B/W laser, USB 1.1)
....
> Thousands of lines like these appear in the error_log. (LogLevel debug)
> 
> D [06/Oct/2006:12:19:33 +0200] [Job 627] Wrote 8192 bytes of print data...
> D [06/Oct/2006:12:19:33 +0200] [Job 627] Received 40 bytes of back-channel
> data!
> D [06/Oct/2006:12:19:34 +0200] [Job 627] Read 8192 bytes of print data...
> D [06/Oct/2006:12:19:34 +0200] [Job 627] Received 40 bytes of back-channel
> data!
> 
> I guess the printer keeps sending acknowledgements of some kind after each
> 8 kB of data, but nobody reads them.
> 
> There is always an offset of 1 second between the back-channel data lines.
> It seems that there is a timeout (perhaps the one defined in
> src/cups-1.2.4/cups/backend.c) that blocks the transfer and waits for the
> driver to read the back-channel data. The driver obviously doesn't read
> from the pipe. By the way, which driver should do so? The min12xxw? But
> that's just a non-interactive filter...
> 
> This means that the data is transferred to the printer at the speed of 8
> kBps. For a 800 kB big print job, 100 seconds are needed for the
> transfer... Is it possible to disable the back-channel data transfers?
> Could one at least set the timeout to 0 somehow?

As a workaround shouldn't it help to use a selfmade "stupid"
usb backend which does only "cat - >/dev/usb/lp0" instead
of the default CUPS usb backend?
If such a workaround works well for you, it shows that it is really
the CUPS usb backend which causes the problem.

Kind Regards
Johannes Meixner
-- 
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