Hellwig controls the DMA code. The Rust bindings use the DMA code. Hellwig is free to change the DMA code without considering whether or not it breaks the rust bindings. the rust bindings are not his problem, nor does he need to start maintaining any rust code.

from Linus:

> You are not forced to take any Rust code, or care about any Rust code in the DMA code. You can ignore it. [...] So when you change the C interfaces, the Rust people will have to deal with the fallout, and will have to fix the Rust bindings.

sounds like it's structured as a downstream user to me.