How long till digital-to-olfactory smell technology is a thing? How do we reach the scientific progress to make this possible?

Example use case: sometimes, in art, don't you want to KNOW the smell, not just imagine it? Artists could attach their own personally crafted interpretation of what it would smell like, be it realistic or with a creative flair, allowing them to tap into an additional human sensory system and enrich peoples' enjoyment of their work.