After the switch to dlopen() the lzma and zstd compression libraries,
libkmod2 does no longer depend on the liblzma5 and libzstd1 packages.
This is bad because kmod is not going to be automatically rebuilt should
one of these libraries change SONAME.  Policy §8.6 recommends to
generate dependencies on dlopen'ed libraries:

,----
| Other packages which use a shared library (for example using
| "dlopen()") should compute appropriate dependencies using these files
| at build time as well.
`----

I think that this would be a very rare event, hence it could be easily
handled manually.
Do you believe that there are any other reasons to declare such
dependencies?

One reason to depend on decompression libraries is so that they are
added to the initramfs -- otherwise we end up with an initramfs that is
unable to decompress .xz-compressed modules.

Did you actually test this? If this really happens then it can be better
fixed in /usr/share/initramfs-tools/hooks/kmod by checking if compressed
modules are being installed in the initramfs.

Yes, I tested it. On a kernel built with CONFIG_MODULE_DECOMPRESS=n
modules were not being loaded and I was dropped at the initramfs shell.

I fixed it by adding a hook with

    copy_exec /usr/lib/*-linux-gnu/liblzma.so.5

but I'm not sure what the best way to detect the path is.

Please copy this updated hook on your system and let me know if it
works.

https://salsa.debian.org/md/kmod/-/blob/master/debian/kmod.initramfs-hook

We believe that the bug you reported is fixed in the latest version of
kmod, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 1099801@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Marco d'Itri <md@linux.it> (supplier of updated kmod package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@ftp-master.debian.org)
Format: 1.8
Date: Fri, 25 Apr 2025 11:50:41 +0200
Source: kmod
Architecture: source
Version: 34.2-2
Distribution: unstable
Urgency: medium
Maintainer: Marco d'Itri <md@linux.it>
Changed-By: Marco d'Itri <md@linux.it>
Closes: 1099801
Changes:
 kmod (34.2-2) unstable; urgency=medium
 .
   * kmod.initramfs-hook: if compressed modules have been copied to the
     initramfs and CONFIG_MODULE_DECOMPRESS=n (which is not the default
     in Debian kernels) then also copy the compression libraries needed
     by kmod to load them. (Closes: #1099801)
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