[cups.development] USB Backchannel read while printing

Michael R Sweet msweet at apple.com
Wed Apr 9 19:51:51 PDT 2008


Joel Hess wrote:
> I'm developing a driver for a USB printer, and am having a problem with the readbacks that are occuring during printing. The firmware in my printer doesn't know what the request if for, so it fails, and apparently there are a number of retries before it gives up. This is causing a significant slowdown in my print process.
> 
> What is the backchannel request expecting for a response so I can resolve the fimware issue? Either that, or is there a way to disable it besides building a different backend that doesn't try the backchannel requests?

It is just expecting whatever data would be sent back, usually status
information.  You can return a 0-byte response ("no data").

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Michael R Sweet                        Senior Printing System Engineer





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