[cups.general] cups detection of usb printers

rance at frontiernet.net rance at frontiernet.net
Thu Jan 31 16:33:18 PST 2008


I have a unique situation that Im not making any headway with, and I  
really need help.

I have an old parallel port dot-matix printer that prints on  
continuous feed paper, I use it for special logging situations,  
banners, and draft printing when my laser toner is running low.


the printer works fine with cups when plugged into parallel port. but  
since I have two parallel printers I bought a usb-parallel conversion  
cable from Belkin.

the dot-matrix printer worked fine as a usb printer under cups 1.1.x

1.2.x has introduced a problem.

First my OS has detected that a usb printer is installed and has  
created a /dev/usb/lpt0 device file with the correct permissions.

under cups 1.1.x that was enough, if the usb backend saw that a usb  
lpt device file was present, it would automatically add the usb port  
to the list of available connectors when adding a printer.


cups 1.2.x is different somehow but I dont understand exactly how.

cups 1.2.x does not show the usb port available in the connectors list  
when adding a new printer.

A google search led me to an article about how the new usb backend  
detects the usb print device files and then "tests" them to see if  
they are "real" printers or not.


I need help in two areas... first, is this true? does the usb backend  
"test" the device to see if its a real usb printer?

and second; If so, what is tested?

Why would a parallel-to-usb cable fail the test?  Only thing I can  
figure is the printer is so old it can't respond to a particular  
status check command that a newer real usb printer might handle ok.

The printer in question is a Panasonic KX-P1124.

I also have a relatively new OKI dot matrix printer (also parallel)  
and its doing the same thing.

both printers seem to work when plugged directly into the parallel  
port, so it isn't the printers themselves, its the usb backend somehow.







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