In Rust 1.80, the previously unstable `slice::flatten` family of methods have been stabilized and renamed to `as_flattened`.
This creates an issue as we want to use `as_flattened`, but need to support the MSRV (which at the moment is Rust 1.78) where it is named `flatten`. Solve this by enabling the `slice_flatten` feature, and abstracting `as_flatten` behind an extension trait that calls the right method depending on the Rust version. This extension trait can be removed once the MSRV passes 1.80. Suggested-by: Miguel Ojeda <[email protected]> Link: https://lore.kernel.org/all/CANiq72kK4pG=O35NwxPNoTO17oRcg1yfGcvr3==fi4edr+s...@mail.gmail.com/ Signed-off-by: Alexandre Courbot <[email protected]> --- init/Kconfig | 3 +++ rust/kernel/lib.rs | 4 ++++ rust/kernel/slice.rs | 63 ++++++++++++++++++++++++++++++++++++++++++++++++++ scripts/Makefile.build | 3 ++- 4 files changed, 72 insertions(+), 1 deletion(-) diff --git a/init/Kconfig b/init/Kconfig index cab3ad28ca49..7da93c9cccc3 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -147,6 +147,9 @@ config LD_CAN_USE_KEEP_IN_OVERLAY # https://github.com/llvm/llvm-project/pull/130661 def_bool LD_IS_BFD || LLD_VERSION >= 210000 +config RUSTC_HAS_SLICE_AS_FLATTENED + def_bool RUSTC_VERSION >= 108000 + config RUSTC_HAS_COERCE_POINTEE def_bool RUSTC_VERSION >= 108400 diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 3dd7bebe7888..2581a356d114 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -21,6 +21,9 @@ #![feature(inline_const)] #![feature(pointer_is_aligned)] // +// Stable since Rust 1.80.0. +#![feature(slice_flatten)] +// // Stable since Rust 1.81.0. #![feature(lint_reasons)] // @@ -128,6 +131,7 @@ pub mod security; pub mod seq_file; pub mod sizes; +pub mod slice; mod static_assert; #[doc(hidden)] pub mod std_vendor; diff --git a/rust/kernel/slice.rs b/rust/kernel/slice.rs new file mode 100644 index 000000000000..7e837bec4bed --- /dev/null +++ b/rust/kernel/slice.rs @@ -0,0 +1,63 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Additional (and temporary) slice helpers. + +/// Extension trait providing a portable version of [`as_flattened`] and +/// [`as_flattened_mut`]. +/// +/// In Rust 1.80, the previously unstable `slice::flatten` family of methods +/// have been stabilized and renamed from `flatten` to `as_flattened`. +/// +/// This creates an issue for as long as the MSRV is < 1.80, as the same functionality is provided +/// by different methods depending on the compiler version. +/// +/// This extension trait solves this by abstracting `as_flatten` and calling the correct method +/// depending on the Rust version. +/// +/// This trait can be removed once the MSRV passes 1.80. +/// +/// [`as_flattened`]: slice::as_flattened +/// [`as_flattened_mut`]: slice::as_flattened_mut +pub trait AsFlattened<T> { + /// Takes an `&[[T; N]]` and flattens it to a `&[T]`. + /// + /// This is an portable layer on top of [`as_flattened`]; see its documentation for details. + /// + /// [`as_flattened`]: slice::as_flattened + fn as_flattened_slice(&self) -> &[T]; + + /// Takes an `&mut [[T; N]]` and flattens it to a `&mut [T]`. + /// + /// This is an portable layer on top of [`as_flattened_mut`]; see its documentation for details. + /// + /// [`as_flattened_mut`]: slice::as_flattened_mut + fn as_flattened_slice_mut(&mut self) -> &mut [T]; +} + +impl<T, const N: usize> AsFlattened<T> for [[T; N]] { + #[allow(clippy::incompatible_msrv)] + fn as_flattened_slice(&self) -> &[T] { + #[cfg(not(CONFIG_RUSTC_HAS_SLICE_AS_FLATTENED))] + { + self.flatten() + } + + #[cfg(CONFIG_RUSTC_HAS_SLICE_AS_FLATTENED)] + { + self.as_flattened() + } + } + + #[allow(clippy::incompatible_msrv)] + fn as_flattened_slice_mut(&mut self) -> &mut [T] { + #[cfg(not(CONFIG_RUSTC_HAS_SLICE_AS_FLATTENED))] + { + self.flatten_mut() + } + + #[cfg(CONFIG_RUSTC_HAS_SLICE_AS_FLATTENED)] + { + self.as_flattened_mut() + } + } +} diff --git a/scripts/Makefile.build b/scripts/Makefile.build index d0ee33a487be..a84b9e3171a3 100644 --- a/scripts/Makefile.build +++ b/scripts/Makefile.build @@ -308,6 +308,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE # The features in this list are the ones allowed for non-`rust/` code. # +# - Stable since Rust 1.80.0: `feature(slice_flatten)`. # - Stable since Rust 1.81.0: `feature(lint_reasons)`. # - Stable since Rust 1.82.0: `feature(asm_const)`, # `feature(offset_of_nested)`, `feature(raw_ref_op)`. @@ -317,7 +318,7 @@ $(obj)/%.lst: $(obj)/%.c FORCE # # Please see https://github.com/Rust-for-Linux/linux/issues/2 for details on # the unstable features in use. -rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,offset_of_nested,raw_ref_op,used_with_arg +rust_allowed_features := asm_const,asm_goto,arbitrary_self_types,lint_reasons,offset_of_nested,raw_ref_op,slice_flatten,used_with_arg # `--out-dir` is required to avoid temporaries being created by `rustc` in the # current working directory, which may be not accessible in the out-of-tree -- 2.51.0
