Comment by chongli

10 months ago

If you're forking the Linux kernel then it becomes your own project, de facto, since you're taking over maintenance of the fork. You're free to rewrite it in Rust when you do that!

Where is anyone forcing anyone else to do a rewrite in Rust?

When hellwig likened the R4L project to a cancer, he was implying exactly this. He saw this one patch as a Trojan horse (in the original Greek sense, not in the computer virus sense) to get Rust into the main kernel tree. This brings all of the toolchain and language issues into it. By relegating Rust to drivers only, the kernel maintainers avoid the issue of having to maintain a cross-language codebase and toolchain, whether they like it or not.

Being a maintainer of a project that accepts patches from contributors is like operating an orphanage. Allowing anyone to just drop off their unwanted babies results in an unmaintainable nightmare. You can say that the Rust for Linux team have been acting in good faith but the very public actions of one of their (now former) leaders contradicts this. The stated goal of the project was to allow drivers to be written in Rust. Adding Rust bindings to the kernel oversteps that goal. It's a legitimate concern.

4 comments

chongli

mustache_kimono 10 months ago

> He saw this one patch as a Trojan horse (in the original Greek sense, not in the computer virus sense) to get Rust into the main kernel tree.

You are aware this patch introduced no code into the main kernel tree?

    rust/bindings/bindings_helper.h |   1 +
    rust/kernel/dma.rs              | 271 ++++++++++++++++++++++++++++++++
    rust/kernel/error.rs            |   1 +
    rust/kernel/lib.rs              |   1 +
    4 files changed, 274 insertions(+)
    create mode 100644 rust/kernel/dma.rs

See: https://lkml.org/lkml/2025/1/8/801

> The stated goal of the project was to allow drivers to be written in Rust. Adding Rust bindings to the kernel oversteps that goal. It's a legitimate concern.

You do recognize that all drivers will need to bind to some C interfaces? So -- your argument (or the argument you suppose Hellwig has) is that it is better that each driver author recreate each such interface for themselves? Now, when these interfaces break as a result of a change in the underlying C code, instead of fixing that breakage at possibly a single place, that one true binding, now a maintainer might have to fix that breakage in a dozen such places? And this is preferable? This will cause less work for the overburdened maintainer?

chongli 10 months ago
You are aware this patch introduced no code into the main kernel tree?
It doesn't have to. By becoming a single point of failure for all Rust drivers that depend on it, it becomes the responsibility of all maintainers of the kernel to avoid breaking it when they change the C interfaces. It's a foothold into a world where all kernel maintainers need to run and test Rust builds, something Christoph does not want the headache of dealing with.
When your teenager brings home a puppy and promises you he'll never let the puppy leave his room, you know that's not true and it won't be long before you're the one taking care of it.
Ultimately it's about motivations. Long-term kernel maintainers are motivated to protect and promote the kernel as a maintainable and successful project. R4L developers, on the other hand, seem more interested in promoting Rust than promoting Linux.
- mustache_kimono 10 months ago
  
  >> You are aware this patch introduced no code into the main kernel tree?
  > It doesn't have to.
  Ah, it's one of those other kinds of Trojan horses that don't enter the city walls.
  > By becoming a single point of failure for all Rust drivers that depend on it, it becomes the responsibility of all maintainers of the kernel to avoid breaking it when they change the C interfaces.
  So -- I'll ask what the Rust for Linux people asked Hellwig -- what is your suggested alternative? Where do we go from here? Is it Rust drivers not be allowed to common interfaces ever? In that case, what are the Rust for Linux team doing?
  Or is it that you would like Linus rethink his decision re: adding Rust to the kernel? And if so, why didn't Hellwig make that case directly to Linus? What's with all this performative bellyaching on the LKML?
  
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