Hi Russell,

On Sat, Feb 12, 2022 at 3:17 PM Russell King (Oracle)
[off-list ref] wrote:

Please don't use CPU_32v6* here.

It probably makes more sense to add a symbol "HAVE_RUST" and have the
appropriate architecture Kconfig files select HAVE_RUST.

We can do it whatever way arch maintainers prefer, of course. Why
would you prefer one over the other?

Does Rust support Thumb on ARMv6 and ARMv7 architectures?

Yes, the main backend is LLVM. Some built-in targets and their support
level are listed here, if you want to take a look:

    https://doc.rust-lang.org/nightly/rustc/platform-support.html

There is also a GCC backend in `rustc` [1], which is making good
progress and may eventually give us access to architectures supported
by GCC. Furthermore, a from-scratch Rust frontend for GCC [2] is being
worked on, though this effort will likely take more time to reach a
point where it may be used for the kernel.

[1] https://github.com/rust-lang/rust/tree/master/compiler/rustc_codegen_gcc
[2] https://github.com/Rust-GCC/gccrs

Please remove every utterance of "default n" from your patch; n is the
default default which default defaults to, so you don't need to specify
default n to make the option default to n. It will default to n purely
because n is the default when no default is specified.

Certainly. I am curious, though: is there a reason for most of the
other 500+ instances in the kernel tree?

As Rust doesn't support all the architectures that the kernel supports,
Rust must not be used for core infrastructure.

Yeah, although I am not sure I understand what you are getting at here.

Cheers,
Miguel