Smith has not played this season and has a history of injury. He appeared in six games for the Lions last season, rushing for 133 yards. In his rookie season of 2008, Smith rushed for 976 yards and eight touchdowns.
The Lions needed to add depth in their backfield as running back Jahvid Best has been sidelined recently with concussion problems and Jerome Harrison is out for the season after being diagnosed with a brain tumor.
Meanwhile, it is unclear where Davis fits on the Lions' offensive line or what corresponding roster move the Lions will make to add Davis to the team.
Detroit is coming off an open date and will play Chicago next week. The Lions are 6-2, but they've had occasional problems protecting quarterback Matthew Stafford.
The Cowboys cut the 33-year-old Davis before training camp. The move saved the Cowboys $6 million against the salary cap in 2011. Davis was scheduled to earn $6 million in base salary and count $9.416 million against the cap this season.
Davis, who signed a seven-year deal worth $49 million in 2007 as a free agent from Arizona, started every game he played for the Cowboys and was named to the Pro Bowl in each of his first three seasons.
Information from ESPNDallas.com's Calvin Watkins and Todd Archer and The Associated Press was used in this report.