[cups.bugs] [LOW] STR #2824: Misleading error reporting.

Michael Sweet mike at easysw.com
Mon May 19 20:24:10 PDT 2008

Kim Bruning wrote:
 > ...
> In essence, I am my linux distributor. 

Well, you'll need to be prepared to do a lot more work to get
printing working than someone using an established Linux distro...

> ...
> Sure, no problem, but on the other hand, if everything in logs and UI
> blithely asserts  that CUPS can , will, and is successfully communicating
> with the printer (but in fact there is something wrong), it's going to be
> rather tricky to deduce that the problem is that there's actually a
> printer driver missing.

Ah, if only there was a way for the computer to know that a) a printer
requires a specific driver and b) there was a single place to get those

As long as the computer can feed data to the printer and the filters
are all working, then what can it do but report that everything is

> ...
> In this case, it would be possible to get an id-string back from
> the printer (on linux, lsusb already does this, for instance) and
> compare it to an entry in the driver file.  If the two don't match, you
> can warn that something is not quite right.  "Warning: Printer ID doesn't
> match ID in driver file.  Possibly you have the wrong driver?" 

1284 device IDs can indeed be used to auto-select a driver, and we
do use them when they are available.  Otherwise we fall back on
product and make/model strings.

Most PPD files do not include 1284 device IDs (this is a driver
developer issue...), and we generally can only get the device ID for
USB-connected printers.  Moreover, some printer vendors do not provide
unique device IDs, like some Epson printers, so auto-selecting a
driver can be problematic.  Logging a warning message in this case
would likely be confusing/frightening for the user.

>> "man" and the on-line help at "http://localhost:631" (which is included at
>> the bottom of every man page and in the README file for CUPS) is the sum
>> total of all CUPS documentation we maintain.  
> That's fine too. In the html interface, would it be hard to make
> error messages in the following form? :

Yes, since the errors in the error_log file are not (and cannot be)
HTML, and since we can't direct users to resources that are OS/distro/
driver/device dependent.

We *do* offer ways to provide help text and links for conditions
reported using printer-state-reasons keywords, but none of the
open source drivers currently use them.


In short, CUPS is just the core printing system and can't provide
"better error detection/reporting" when the driver and UI software
that supports printers does not provide any error detection or

Michael Sweet, Easy Software Products           mike at easysw dot com

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