is umplock optional?

[mihailescu2m]

https://github.com/endlessm/xf86-video-armsoc/blob/master/src/armsoc_driver.c#L807

so if you don't have ump enabled, will this pass?
also, is the old code, before umplock, used? (if -1 != umplock_fd {ump_lock code} else {old_code})
or is umplock assumed?