This company has one of the strangest interview processes that I have encountered.
The process starts with a fairly lengthy questionnaire that starts by asking what your high-school peers would remember you for. The next stage is a web-based reaction time test in which you have to solve verbal, spatial and arithmetic puzzles as fast as you can, as these are flashed on the screen.
While I can understand the use of an extended statement of purpose, I just don't see how how a speed of reaction test maps to the ability to write any kind of code, leave alone kernel code where the ability to hold a LOT of context in one's head -- multiple threads of control, multiple address spaces in concurrent use - would be far more important than 'speed'.