[Printing-architecture] Debian dropping the Linux Standard Base - Better way to supply distribution-independent printer driver packages?
Till Kamppeter
till.kamppeter at gmail.com
Sat Feb 6 01:31:43 UTC 2016
Hi,
here are some first thoughts about how to distribute printer drivers in
distribution-indpendent package without making use of the LSB:
First thought is to link the executables of the package statically to
not depend on the presence and version of locally available libraries.
But static linking causes several problems, especially see
https://www.akkadia.org/drepper/no_static_linking.html
and
http://unix.stackexchange.com/questions/227910/will-my-linux-binary-work-on-all-distros
One problem is that libc uses dlopen() to link libraries dynamically and
if you link in libc statically you need exactly the same libc on your
computer so that the dlopen() works.
A possibility is to replace libc by specialized alternative, musl, when
building the executables:
http://www.musl-libc.org/
musl only needs to be installed on the machine where the packages get
built and there not even as the system's libc. So for statically linked
executables this looks like a good possibility.
Another possibility is to link only some libs (libc, X11, openGL)
dynamically and the rest statically:
http://blog.sagargv.com/2014/09/on-building-portable-linux-binaries.html
In general, we need to find the least complicated way which can be
easily adopted by most printer manufacturers.
Another way to get universally working printers/drivers is keeping the
level of complexity of the drivers as low as possible by dosigning
printers (and drivers) the right way:
Level 0:
driverless printing, the standard Linux distributions bring already all
software needed to print on the printer and the printer can get queried
for all needed capability info, usually via Bonjour and/or IPP. A good
example are IPP Everywhere printers.
Level 1:
Only data files, like PPDs are needed, all executable files are already
contained in the standard Linux distributions. This can be done with
PostScript, PCL, PDF, PWG Raster, ... printers.
Level 2:
Only executables are filters, meaning that the printer works with the
backends supplied by CUPS and cups-filters and only needs a known PDL,
usually PWG or CUPS Raster being converted to the printer-specific,
proprietary language.
Level 3:
Backends are needed to make the printer work. Backends are more complex
than filters as they have to implement a way of communication between
the computer and a peripheral, via USB, network, ... so more resources
of system libraries are needed which could make static linking or
universally working binaries more difficult.
Extras:
Scanner driver (SANE):
For multi-function devices often a scanner driver is supplied. Scanner
drivers are dynamic libraries which are linked by scanning clients, I do
not know whether such a library by itself can get linked statically.
Scripting languages:
If a scripting language is used, it must be a standard one, usually
Python, perhaps also Perl, and if libraries are needed they should be
preferrably shipped with the package.
GUI:
Should be avoided whenever possible for a printer driver package because
making this universally executable is even more complicated.
First step is a good printer design, ideally an IPP Everywhere printer.
If the printer is already there and a Linux driver has to be designed,
at first the level of complexity needs to be minimized. Especially if
the printer follows a standard PDL (like PCL XL) or a standard
communication protocol (like IPP-over-USB) but it does not work with the
software of the Linux distributions, do not write your own, proprietary
work-around filters and backends, but report bugs of feature requests on
the existing software or better contribute patches.
Any thoughts and any additional hints to get distribution-independent
printer driver packages without needing the LSB?
Till
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