3:36 PM PT -- Darius Rucker's attorney, Mark Puryear, tells TMZ … "Darius Rucker is fully cooperating with authorities related to misdemeanor charges."
Darius Rucker got busted on a minor drug offense in Tennessee -- and from the sound of the charge he was booked on ... it basically amounts to an alleged handoff.
The country singer -- obviously famous from Hootie & the Blowfish -- was taken into custody Thursday in Williamson County, which is where he lives. He posed for this mug shot for the Sheriff's Dept. there ... and was booked on three separate charges, all misdemeanors.