Gallagher, who appeared in Harry Potter and the Half-Blood Prince, has joined a cast that features Brendan Gleeson and S. Epatha Merkerson, who will play Gaye's mother. Jesse L. Martin will portray the soul man.
The untitled project is among the films being presented to buyers at the Cannes Film Festival in France.
Temple's film will focus on the 18 months Gaye spent in Belgium recording the album Midnight Love.
There was big superhero movie news today as Warner Bros. unveiled plans for extending the franchises of established favourites such as The Lego Movie and...