[Printing-architecture] Automatic printer setup with Printer Applications

[Solomon Peachy]

On Wed, Feb 24, 2021 at 12:25:48PM +0100, Till Kamppeter wrote:
> udev-configure-printer will need an interface at all Printer Applications
> where it can send a device ID and the Printer Application answers back
> whether it supports this printer (with driver name), and that without the
> Printer Application talking to the physical printers. 

I wanted to add a comment here -- We need to think about what happens if 
multiple applications claim to support the printer, either because more 
than one genuinely does, or because of wildcard catch-all rules for 
"generic PCL" (or whatever) that could bind to any device exporting a 
USB Printer Class endpoint, much like the current CUPS backend.

The CUPS backend supports a blacklist so it can exclude printers, but 
given that printer applications can't drop files outside their sandbox, 
a new mechanism would need to be devised.  

> Great would be if a Printer Application also could report back support 
> level (generic, third-party, manufacturer, ...). It could perhaps also 
> prioritize unknown Printer Applications as they are most probably from 
> the manufacturer and not from the distro.

I don't know if there's any reasonable priority rules we could apply 
that would always yield the "correct" choice.  Except perhaps to put 
"generic" options at the bottom, but even if those generic options are 
the only ones available, the odds are they won't actually function 
properly anyway.

BTW, current (RHEL/Fedora) distro practice is to extract the complete 
list of supported printers at "printer driver packaging" time, and use 
that to figure out what package needs to be installed at runtime.  IIRC 
this exclusively uses IEEE1284 IDs.

And as a depressing data point, Gutenprint only has IEEE1284 IDs for 
about 15% of its supported models, and USB VID/PIDs for about 3%.  So a 
mechanism to auto-match based on the Manufacturer & Model strings out of 
the USB or IEEE1284 descriptors would still be a good idea..

 - Solomon
-- 
Solomon Peachy			      pizza at shaftnet dot org (email&xmpp)
                                      @pizza:shaftnet dot org   (matrix)
High Springs, FL                      speachy (freenode)
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