Rust version requirement (was: [PATCH V2 3/3] powerpc: Enable Rust for ppc64le)

[J. Neuschäfer]

On Thu, Feb 05, 2026 at 09:12:01PM +0530, Mukesh Kumar Chaurasiya wrote:
[...]
> use rust version nightly-2026-01-28
> 
> the latest one has some issue. I just raised a bug for the rustc
> here[1].
> 
> [1] https://github.com/rust-lang/rust/issues/152177

Another reason to use a nightly version is that Rust inline assembly for
PowerPC will only be stabilized[1] in version 1.94, so current release
versions fail like this (tested with 1.91.1):

    error[E0658]: inline assembly is not stable yet on this architecture
      --> ../rust/kernel/sync/barrier.rs:19:14
       |
    19 |     unsafe { core::arch::asm!("") };
       |              ^^^^^^^^^^^^^^^^^^^^
       |
       = note: see issue #93335 <https://github.com/rust-lang/rust/issues/93335> for more information
       = help: add `#![feature(asm_experimental_arch)]` to the crate attributes to enable
       = note: this compiler was built on 2025-11-07; consider upgrading it if it is out of date

This is somewhat at odds with Documentation/process/changes.rst which
only requires Rust 1.78. I wonder if the rust version requirement should
generally be bumped, or if there should be arch-specific requirements
somewhere in changes.rst or rust/arch-support.rst.

Best regards,
J. Neuschäfer

[1]: https://github.com/rust-lang/rust/pull/147996