usb probing malforms Epson TM-T70 label printer output

Patch proposal for Artful.

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As the backends do not filter data but simply pass the data through it is not clear whether the "usb" CUPS backend really causes the problem. Especially in this case the CUPS backend still lets go data to the printer and the printer prints something.

So before modifying the backend behavior I would like to know what kind of data you feed to the printer and what does CUPS exactly do.

Did you create a CUPS queue with a driver/PPD file? Which driver or PPD file (please attach your print queue's PPD file from /etc/cups/ppd/)? Or did you create a raw (unfiltered) queue? How do you send jobs to CUPS? Do you simply send them or do you use the "-o raw" option (unfiltered by-job)? Are you sending jobs as plain text or as PDF, PostScript, ...?

If you add the quirk rule to blacklist your printer the "usb" CUPS backend would ignore the printer preventing the backend to discover the printer. How are you using the printer then? Another CUPS backend? Which one? No use of CUPS at all (like "cat file > /dev/usb/lp0")? Are you using a driver/filter then?

Please also follow the instructions of the sections "CUPS error_log", "USB printer", "Capturing print job data", and "Getting the data which would go to the printer" for the case when you are using the "usb" CUPS backend without changes in the quirk rules and also when using CUPS with the change. also run

sudo lsusb -vvv > lsusb-out.txt

and attach the resulting file.

Please do not compress any of the files you get and do not package them together. Attach them to this bug report one by one.

Till,
The printer in question is was used completely *outside* CUPS - via the /dev/usb/lp* nodes only. Although there was also an attempt with using it with a raw queue - with the same result: whenever CUPS was enabled or the printer was not blacklisted the output from the printer was malformed.

My understanding is that something that CUPS libusb backend was doing in the 'probing' phase (backends/usb-libusb.c find_device()) is influencing the printer configuration and changing it's settings set by control characters.

Attaching the lsusb portion related to the printer in question.

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