Communication between kernel modules (what's the proper way?)

[JC]

Somewhat out of topic for the mailing list, but I guess the developers
here could advise me on the matter:

I have developed two modules that use hooks to manipulate packets, and
I wish for them to communicate with each other. The proper way to
communicate with userspace is by using ioctls. But what is a proper
way to use to pass data between the two modules, bearing in mind these
are my modules and I cant apply for a system call...?

regards,
Ioannis