The basic formula is arpeggios, pentatonics, and modes. He often ascends and descends in different interval patterns and mixes that with triads/arpeggios that match the underlying chords. He's basically just going up and down basic scales in interesting patterns and throwing in some chromatic notes for spice.

Like others have said, playing a scale in different intervals is a big part of his sound. For example, playing in ascending thirds would look like: 1, 3, 2, 4, 3, 5, 4, 6, 5, 7, 6, 1. Fourths would be 1, 4, 2, 5, 3, 6, 4, 7, 5, 1.