EXCLUSIVE: Winning Time executive producer Rodney Barnes has boarded HBO’s limited series project, set to star Mahershala Ali as boxing legend Jack Johnson. Barnes, who is under an overall deal with HBO, will serve as writer and executive producer on the Untitled Jack Johnson limited series (fka Unruly), bringing a brand new take on adapting the PBS documentary Unforgivable Blackness: The Rise and Fall of Jack Johnson, produced and directed by Ken Burns, and its companion book by Geoffrey C. Ward.