[cups] Still conceptually possible to use SCSI backend in latest CUPS?

[Protea Wines Japan]

On Mon, Feb 22, 2021 at 3:59 PM Jörg Thümmler
<listen at vordruckleitverlag.de> wrote:

Hallo Jörg,

Many thanks for the reply.

> Am 20.02.21 um 18:47 schrieb Protea Wines Japan:
> > On Fri, Feb 19, 2021 at 4:01 PM Johannes Meixner <jsmeix at suse.de> wrote:
> >>
> >> On 2021-02-18 18:20, Protea Wines Japan wrote (excerpt):
> >>> Is it conceptually still possible to compile
> >>> the old scsi.c backend in CUPS 1.2
> >>
> >> conceptually a CUPS backend is an arbitrary program
> >> that gets data and sends it to a recipient, see
> >>
> >> https://en.opensuse.org/SDB:Using_Your_Own_Backends_to_Print_with_CUPS
> >
> > Many thanks Johannes, I could tell from your document that there is nothing
> > specifically preventing the SCSI backend from being used, provided it uses
> > the right commands to the SCSI high-level driver.
> > I spent some time reading up on the SCSI subsystem in linux again, and the
> > sg3 high-level driver.
> > It looks like the scsi.c file should still be compilable and usable as is,
> > since it uses the sg_io_hdr which is what is currently used in sg3 also.
> >
> > I ran into a problem with compiling though. I wonder if you or anyone
> > familiar with the current (forked?) CUPS code can help:
> >
> > hase at hase:~/src/CUPS-SCSI-Backend$ gcc -o scsi-backend scsi.c
> > In file included from scsi.c:59:
> > /usr/include/cups/i18n.h:18:12: fatal error: config.h: No such file or
> > directory
> >     18 | #  include "config.h"
> >        |            ^~~~~~~~~~
> > compilation terminated.
> >
> > It looks like the CUPS header file config.h is missing. I am not sure where
> > I should find this, I have all available development packages installed I
> > think. Even downloading the Debian CUPS source package does not find this
> > file although there are 2 config.h files in subsystem source trees:
> > hase at hase:~/src/CUPS-SCSI-Backend/cups-2.3.3op2$ find . -name config.h
> > ./vcnet/config.h
> > ./xcode/config.h
> >
> > As for linux, there are 2 config.h files in the source tree (none in the
> > common headers):
> > hase at hase:~/src/CUPS-SCSI-Backend/cups-2.3.3op2$ find
> > /usr/src/linux-headers-5.10.0-3-amd64 -name config.h
> > /usr/src/linux-headers-5.10.0-3-amd64/include/config/snd/intel/dsp/config.h
> > /usr/src/linux-headers-5.10.0-3-amd64/include/config/pci/lockless/config.h
> Hi,
>
> i'm in no case familiar with cups code ;-)
>
> But your "gcc -o scsi-backend scsi.c" may need some -I<dir> option (see
> man gcc) as it may not find the config.h in its standard include path.
>
> Or - another "blind shot" - you may have to install the kernel header
> files therefor. "i18n.h" sounds like an include a lot of programs will
> use so it may be will look for a "central" config.h...
>
> At least a look into this i18n.h will maybe show, in which context the
> "config.h" is searched and that may give you a hint, which "config.h" to
> include.
>
> Another way may be to use the "configure" feature (if cups-devel has
> that), which usually does the trick of writing of correct make files for
> compiling and then try to find a appropriate gcc line for some analogue
> backend compiling.

Will do. I already discovered in the meantime trying something like
you suggest but just with examination of the current Debian CUPS
package source code, that cups has many files like i18n-private.h
which are copied to i18n.h by the configuration script.
I see many other header files that should be produced by configure,
but they do not match well the existing CUPS header files in my
/usr/include/cups directory, which are supplied by libcups2-dev.
I therefore came to the conclusion, perhaps too soon, that maybe the
CUPS development packages are not in sync with the current CUPS
package.

I checked that I already have the linux-headers package installed.
I also tried to grab header files from existing backends in the Debian
CUPS source package, as well as updating the logic for SIGSET and
SIGACTION, still errors though.

Now I will check what happens if I compile the CUPS source package in
/opt or something like that, whether come include files are generated
that I can make use of instead of the current ones provided by
libcups2-dev.

Best regards,
Gernot Hassenpflug