I think my test didn't exercise this function, but I think makes sense to fix endian here, like in opal_heartbeat(). No side effect was seen.

http://open-power.github.io/skiboot/doc/opal-api/opal-handle-interrupt.html?highlight=opal_handle_interrupt

This would indicate a programming error

OPAL_PARTIAL means the buffer is too small for the message. Might include that bit in here. Nothing we can do if we get that, really, without other changes to this function.

From the docs:

If pending opal message is greater than supplied buffer. In this case the message is DISCARDED by OPAL. This is to keep compatibility with host Operating Systems with a hard coded opal-msg-size of 72 bytes. NOT CURRENTLY IMPLEMENTED. Specified so that host OS can prepare for the possible future with either a sensible error message or by gracefully ignoring such OPAL messages.

Any reason for this extra blank line?