C style
-------

The kernel CodingStyle where applicable

https://www.kernel.org/doc/html/latest/process/coding-style.html

Error messages
--------------

* formatting:
  * use `error("string ...")`
  * no trailing newline
  * small letter starts the first word
  * no string splitting
  * move string to new line if it's too long, un-indent to the left if it
    exceeds 80 chars
* contents:
  * be descriptive
