At times you may come across some old or legacy kernel source-code which could be something you stumbled across online open-source code or it could be your organization proprietary code which you no longer able to compile and get it working on your recent target kernel version(s). This is more often a common occurrence than you expect. Since as I say always Linux Kernel Source is always ever changing and evolving. So in such circumstances you may need to properly port this code to the respective intended kernel to make it fully compliant and compatible.
Usually when you try to compile such an old legacy code you may get several compilation issues, which again depends on the size and complexity of your legacy source-code.
So here is my detailed YouTube video where I discuss some of the intricacies, my tips, big-picture and approach which you can follow to port such a legacy code and make it compatible.
Refer:
Linux Kernel Module to Drop Packets captured via netfilter hooks ↗
Linux Kernel /proc Interface – create and read /proc file ↗
Linux Kernel /proc Interface category articles ↗
Example Linux Kernel source diffs discussed in my video:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/diff/?id=v6.6.35&id2=v6.6.34&dt=2
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/diff/?id=v4.19.316&id2=v4.19.315&h=linux-5.14.y
I also conduct sessions/classes on Systems and Network Software Programming, Linux Kernel Programming and Architecture. If you are interested, click HERE for more details.
If you have any queries or anything to discuss further on Linux Kernel Programming and writing Kernel modules kindly feel free to contact me.