vboot's recovery reason has a "subcode" stored next to it in NVRAM that is occasionally useful to narrow the problem down further. It's mostly used (and would be very helpful) with TPM problems like the one from http://crosbug.com/p/55764.

We store the recovery reason in the eventlog, but not the subcode. Maybe we should do both (it would just be 11 bytes instead of 10, so who cares). We could even check if the subcode is non-zero and only store it in that case, since eventlog events can be variable in length (at least when looking at the format alone... not sure if mosys would be equipped to handle that).