Barnsley have completed the signing of Hull's Nathan Doyle on a free transfer.
The 23-year-old utility player, who has been on loan at Oakwell since 18 September 2009, has agreed a two-and-a-half year deal.
Reds boss Mark Robins told the club website: "Nathan did very well during his loan spell and we are delighted to bring him back to the club.
"This is a deal we have been working on for a while and I am delighted that it has now come to fruition."
Meanwhile Grimsby are expected to complete the signing of striker Michael Coulson on a permanent basis.
Coulson has been on loan at Blundell Park since November.