[xg15]

> I suppose the biggest reason is that C programmers are more likely than not trained to kinda know what the assembly will look like in many cases, or have a very good idea of how an optimizer compiler will optimize things

This is the only way Hellwig's objection makes any kind of sense to me. Obviously, intra-kernel module boundaries are no REST-APIs, where providers and clients would be completely separated from each other. Here I imagine that both the DMA module as well as its API consumers are compiled together into a monolithic binary, so if assumptions about the API consumers change, this could affect how the module itself is compiled.