  A full description of a magnetic sample includes a correct treatment of the
boundary conditions (BCs). This is in particular important in thin film
systems, where even bulk properties might be modified by the properties of the
boundary of the sample. We study generic ferromagnets with broken spatial
inversion symmetry and derive the general micromagnetic BCs of a system with
Dzyaloshinskii-Moriya interaction (DMI). We demonstrate that the BCs require
the full tensorial structure of the third-rank DMI tensor and not just the
antisymmetric part, which is usually taken into account. Specifically, we study
systems with $C_{\infty v}$ symmetry and explore the consequences of the DMI.
Interestingly, we find that the DMI already in the simplest case of a
ferromagnetic thin-film leads to a purely boundary-driven magnetic twist state
at the edges of the sample. The twist state represents a new type of
DMI-induced spin structure, which is completely independent of the internal DMI
field. We estimate the size of the texture-induced magnetoresistance effect
being in the range of that of domain walls.
