Of course! We don't include any linux specific headers in the code that is meant to be cross-platform, but for local debugging that's no issue.

If you're in the nvidia.ko portion of the codebase (src/nvidia/...), portDbgPrintf() is generally a thin wrapper around printk() that you can readily use without including anything. Also NV_PRINTF(LEVEL_ERRORS, "...") behaves very similarly to printk() with some added functionality.