Date:   Sat, 25 Feb 2023 00:45:32 +0000
From:   Gary Guo <gary@garyguo.net>
To:     Asahi Lina <lina@asahilina.net>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        =?UTF-8?B?QmrDtnJu?= Roy Baron <bjorn3_gh@protonmail.com>,
        Masahiro Yamada <masahiroy@kernel.org>,
        Nathan Chancellor <nathan@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Nicolas Schier <nicolas@fjasle.eu>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-kbuild@vger.kernel.org, asahi@lists.linux.dev
Subject: Re: [PATCH] rust: Enable the new_uninit feature for kernel and
 driver crates
Message-ID: <20230225004532.5f1bf427.gary@garyguo.net>
In-Reply-To: <20230224-rust-new_uninit-v1-1-c951443d9e26@asahilina.net>
References: <20230224-rust-new_uninit-v1-1-c951443d9e26@asahilina.net>
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On Fri, 24 Feb 2023 17:09:47 +0900
Asahi Lina <lina@asahilina.net> wrote:

> The unstable new_uninit feature enables various library APIs to create
> uninitialized containers, such as `Box::assume_init()`. This is
> necessary to build abstractions that directly initialize memory at the
> target location, instead of doing copies through the stack.
> 
> Will be used by the DRM scheduler abstraction in the kernel crate, and
> by field-wise initialization (e.g. using `place!()` or a future
> replacement macro which may itself live in `kernel`) in driver crates.
> 
> See [1] [2] [3] for background information.
> 
> [1] https://github.com/Rust-for-Linux/linux/issues/879
> [2] https://github.com/Rust-for-Linux/linux/issues/2
> [3] https://github.com/rust-lang/rust/issues/63291
> 
> Signed-off-by: Asahi Lina <lina@asahilina.net>

Reviewed-by: Gary Guo <gary@garyguo.net>

> ---
>  rust/kernel/lib.rs     | 1 +
>  scripts/Makefile.build | 2 +-
>  2 files changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index 223564f9f0cc..1118cd3e0b5f 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -17,6 +17,7 @@
>  #![feature(core_ffi_c)]
>  #![feature(dispatch_from_dyn)]
>  #![feature(generic_associated_types)]
> +#![feature(new_uninit)]
>  #![feature(receiver_trait)]
>  #![feature(unsize)]
>  
> diff --git a/scripts/Makefile.build b/scripts/Makefile.build
> index a0d5c6cca76d..0f637e1ca8dc 100644
> --- a/scripts/Makefile.build
> +++ b/scripts/Makefile.build
> @@ -277,7 +277,7 @@ $(obj)/%.lst: $(src)/%.c FORCE
>  # Compile Rust sources (.rs)
>  # ---------------------------------------------------------------------------
>  
> -rust_allowed_features := core_ffi_c
> +rust_allowed_features := core_ffi_c,new_uninit
>  
>  rust_common_cmd = \
>  	RUST_MODFILE=$(modfile) $(RUSTC_OR_CLIPPY) $(rust_flags) \
> 
> ---
> base-commit: 83f978b63fa7ad474ca22d7e2772c5988101c9bd
> change-id: 20230224-rust-new_uninit-a575d34987c3
> 
> Thank you,
> ~~ Lina
>