Maximal lattice-free convex sets in linear subspaces

We consider a model that arises in integer programming, and show that all irredundant inequalities are obtained from maximal lattice-free convex sets in an affine subspace. We also show that these sets are polyhedra. The latter result extends a theorem of Lov\'asz characterizing maximal lattice-free convex sets in $\mathbb{R}^n$.