It may be technically insufficient, if the RfL folks can't integrate Rust without C changes. And if that's true, (and it seems to be true) then it's time for an architectural discussion to come to an agreement on if Rust for Linux should be pursued or if C code flexibility and readability is more important.
> if the RfL folks can't integrate Rust without C changes
The RfL folks can integrate Rust without C changes.
All of the changes in the patch (ever since v1) have been entirely contained inside the rust directory, with most of the changes being in the rust/kernel/dma.rs file. There were no changes to C files, or to files inside the kernel/dma directory.