Although it was a DMA patch, it was not in the DMA subsystem that Christoph maintains. More specifically, it was not a file in the kernel/dma directory, but rather a file in the rust/kernel directory, which is where the Rust subsystem lives.
The Rust code is essentially a consumer of the DMA public API, much like many other subsystems in the kernel that consume it.
This is why some people are upset and confused about the situation; he added a Nacked-by tag to a patch that is outside his area. He had good reasons for it, but it was hard to see them based on the way he wrote his replies.
Wait what? Thought I saw somwehere that he's the DMA maintainer, and wasn't this a DMA patch?
> he is simply being obstructionist out of tribalism.
Or is it the Rust people who are being intrusionist out of their tribalism? Looks at least as much like that to me.