[eximius]

Hmm... This is certainly very interesting. Can anyone think of any neat kernel-only things that one might implement for kicks as a learning project? Particularly for someone who hasn't done kernel programming? It could definitely be a silly thing, but probably more useful than printing to the kernel log.

[jevinskie]

Providing guaranteed access to random numbers has been a recent example of a new, badly needed, but fairly simple syscall. With getrandom(), you avoid the complexities of open/read/close and its associated error handling.

https://lwn.net/Articles/606141/

[brenns10]

Character devices are a fertile ground for cool projects in my opinion. They're not very hard to make (typically just a kernel module, no booting a custom kernel), most unix tools interact with them naturally because they're just files, and they can do many interesting things within the kernel. One of my recent projects (after system calls) was to create a "chat server" in the kernel with a character device. Good references are Robert Love's Linux Kernel Development, 3rd edition, and the Linux Kernel Module Development Guide.