Comment by thesuperbigfrog
2 days ago
Linus's reply is perfect in tone and hopefully will settle this issue.
He is forceful in making his points, but respectful in the way he addressed Christoph's concerns.
This gives me great hope that the Linux maintainer community and contributers using Rust will be able to continue working together, find more common ground, and have more success.
The response addressed Christoph's concerns _in word_.
According to the policy, rust folks should fix the rust binding when C changes breaks the binding. The C maintainer don't need to care rust, at all.
In practice, though, I would expect this needs lots of coordination. A PR with C only changes that breaks the whole building (because rust binding is broken) is unlikely to be merged to mainline.
Linus can reiterate his policy, but the issue can't be resolved without some rust developers keep on their persistent work and builds up their reputation.
> rust folks should fix the rust binding when C changes breaks the binding
I have never understood how that could work long-time. How do you release a kernel, where some parts are broken? Either you wait for Rust people to fix their side or you drop the C changes. Or your users suddenly find their driver doesn‘t work anymore after a kernel update.
As a preliminary measure when there isn‘t a substantial amount of Rust code, yet, sure. But the fears of some maintainers that the policy will change to "you either learn Rust and fix things or your code can be held up until someone else helps you out" are well-founded, IMO.
Are you familiar with Linux kernel development process? Features can be merged only in two weeks long merge window. After the merge window closes, only fixes are merged for eight weeks. Rust binding can be fixed in that time. I don't see any problems.
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I think the way you do this is set things up so that no bits that are written in Rust are built by default, and make sure that the build system is set up such that Rust bindings for C code are only built when there's Rust code that's enabled that requires them.
Then sure, some people who download a kernel release might enable a Rust driver, and that makes the build fail. But until Rust is considered a first-class, fully-supported language in the kernel, that's fine.
In practice, though, I would expect that the Rust maintainers would fix those sorts of things up before an actual release is cut, after the 2-week merge window, during the period when only fixes are accepted. Maybe not every single time, but most of the time; if no one is available to fix a particular bit of breakage, then it's broken for that release. And that's fine too, even if it might be annoying to some users.
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Because nothing is forcing a distro to adopt a kernel that has items that are broken. Not a lot of folks out there are manually compiling and deploying standalone kernels to production systems.
C can break rust, and Debian/Ubuntu/Redhat/suse/etc can wait for it to be fixed before pushing a new kernel to end users.
You can merge it into your branch as e.g. the DMA maintainer, then the rust folk can pull your changes and fix the bindings. Maybe you as maintainer could give them a heads up and a quick consideration of the error.
Yes, Rust as something optional doesn't really make sense long term. Either it will continue to only be used in nieche drivers (in which case why bother?) or eventually you need to build Rust code to have a usable kernel for common hardware. Any promises to the contrary need to be backed up with more than "trus me bro".
Why wouldn't it be merged? No Rust code is built unless CONFIG_RUST is on, and it is off by default. It won't be on by default for a long time.
That's the theory. However, isn't likely that as things like the new Nova Nvidia driver is written in Rust, the things that depend on Rust are suddenly so important, that shipping with it disabled is unrealistic, even without a policy change. (I don't think this is bad)
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How many kb ram is enough for everyone?
Linus is one of the few people who can forcefully argue the case for moderation, and I've recognized some of the lines I've used to shift really contentious meetings back into place. There's the "shot-and-chaser" technique (a) this is what needs to happen now for the conversation...
"I respect you technically, and I like working with you[...] there needs to be people who just stand up to me and tell me I'm full of shit[...] But now I'm calling you out on YOURS."
...and (b) this is me recognizing that me taking charge of a conversation is a different thing than me taking control of your decisions:
"And no, I don't actually think it needs to be all that black-and-white."
(Of course Linus has changed over time for the better, he's recognized that, and I've learned a lot with him and have made amends with old colleagues.)
I really liked this reply from Torvalds. I've seen a lot of his older rants, and while I respect his technical achievements, it really turned me off on the guy himself. I was skeptical of his come-to-jesus moment back in 2018 (or whenever it was), but these days it's great to read his measured responses when there's controversy.
It's really cool to see someone temper their language and tone, but still keep their tell-it-like-it-is attitude. I probably wouldn't feel good if I were Christoph Hellwig reading that reply, but I also wouldn't feel like someone had personally attacked me and screamed at me far out of proportion to what I'd done.