how to write cross-version/platform Linux kernel modules?

Question

I'm new to programming Linux kernel modules, and many getting started guides on the topic include little information about how to build a kernel module which will run on many versions and CPU platforms of Linux. Most of the guides I've seen simply state things like, "Linux doesn't ensure any ABI/API compatibility between versions." However, other OSes do provide these guarantees for major versions, and the guides are mostly targeting 2.7 (which is a bit old now).

I was wondering if there is any kind of ABI/API compatibility now, or if there are any standard ways to deal with versioning other than isolating the kernel-dependent bits of my code into files with a ton of preprocessor directives. (Also, are there any standard preprocessor symbols I should be using in the second case?)

Answer 1

There isn't a stable ABI for the kernel and most likely never will be because it'd make Linux suck. The reasons for not having one are all pretty much documented in that link.

The best way to deal with this is to get your driver merged upstream where it'll be maintained by other kernel developers.

As to being cross-platform, that pretty much comes free with the Linux kernel as long as you only use the standard, platform-independent functions provided in the API.