Who ruled the Khazars between Tong Yabgu to Irbis, if not Irbis himself?

Who ruled the Khazars between Tong Yabgu to Irbis, if not Irbis himself?

Tong Yangu khagan finished his reign on 628. Who ruled the Khazars between Tong Yabgu to Irbis, if not Irbis himself?