What relationship did Malcolm X and Ellsworth Raymond (Bumpy) Johnson actually have?

So, I've watched the series God Father Harlem, which inspired me to read the autobiography of Malcolm X. His autobiography doesn't mention Bumpy Johnson at all, while the series portrays them as good friends. I've also read that there isn't much known about their relationship, except that Bumpy provided personal security for Malcolm. So they did at least have some kind of relationship.

Can anyone tell me more about them or point me to something to read or watch?