Subject: Re: [PATCH v4 16/20] Kbuild: add Rust support

From: "Russell King (Oracle)" <[email-masked]>
Date: Sat, 12 Feb 2022 14:16:50 +0000

On Sat, Feb 12, 2022 at 02:03:42PM +0100, Miguel Ojeda wrote:
> +config RUST
> +	bool "Rust support"
> +	depends on RUST_IS_AVAILABLE
> +	depends on ARM64 || CPU_32v6 || CPU_32v6K || (PPC64 && CPU_LITTLE_ENDIAN) || X86_64 || RISCV

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.

Does Rust support Thumb on ARMv6 and ARMv7 architectures?

> +	depends on !MODVERSIONS
> +	depends on !GCC_PLUGIN_RANDSTRUCT
> +	select CONSTRUCTORS
> +	default n

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.

> +	help
> +	  Enables Rust support in the kernel.
> +
> +	  This allows other Rust-related options, like drivers written in Rust,
> +	  to be selected.

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

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