What RT patch to use for a specific linux kernel version

Question

Running the $uname -r command on my embedded device reveals my kernel to be 4.14.73-ltsi (it is a custom Linux kernel built for an embedded device).

Now I intend to install the real time (RT) patch for this kernel version. However, on the official webpage I don't see a patch specific for kernel version 4.14.73. The nearest ones I see are patch-4.14.87-rt49.patch.xz and patches-4.14.63-rt43.tar.xz.

Which of these two patches would be most compatible with my Linux kernel version (4.14.73-ltsi) ?

Answer 1

I would try applying the latest patch for 4.14, i.e. https://mirrors.edge.kernel.org/pub/linux/kernel/projects/rt/4.14/patches-4.14.186-rt86.tar.gz - if it applies cleanly it should work.

If it doesn't please try applying earlier patches from the older subdirectory.

Answer 2

Kernel version 4.14 is currently in Long Term Support state (LTS) which means it is an old version (or better not the latest stable release), thus no more new feature added but it is, and will be for an amount of time, supported/maintained on the security side. This likely is the reason why you will not find the right patch-set for your kernel version.

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Turning to the issue, no one of the two available patch-set will be compatible with your kernel theoretically speaking. Both will fail.
Since to apply a patch means re-compile the entire kernel, it is not smart for you to try one of these patch-sets on your kernel version. The clever move is to get the right kernel version combined with the right patch-set.

e.g. staying on 4.14 kernel series for compatibility matters of your embedded device, jump on the latest 4.14.186 version