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Add an `Align` type so it can also be specified via const generics. Signed-off-by: Gary Guo --- Andreas, could you see if this patch meets your need for cache-line aligning? Changes in v2: - Added `Clone`, `Copy`, `Debug` impl. (Sashiko) - Expand impl to 65536, i.e. PAGE_SIZE_64K. Kernel technically support PAGE_SIZE_256K, but it's uncommon enough so I think there's no need to support it unless a need arises. (Sashiko) - Use `_align` in example, as usually the field is not going to be referenced. - Link to v1: https://patch.msgid.link/20260609120325.233721-1-gary@kernel.org --- rust/kernel/lib.rs | 1 + rust/kernel/mem.rs | 70 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 71 insertions(+) diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs index 9512af7156df..0a12c3011c61 100644 --- a/rust/kernel/lib.rs +++ b/rust/kernel/lib.rs @@ -92,6 +92,7 @@ pub mod kunit; pub mod list; pub mod maple_tree; +pub mod mem; pub mod miscdevice; pub mod mm; pub mod module_param; diff --git a/rust/kernel/mem.rs b/rust/kernel/mem.rs new file mode 100644 index 000000000000..7f7545c6e545 --- /dev/null +++ b/rust/kernel/mem.rs @@ -0,0 +1,70 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Utilities handling things related to memory layouts. + +// TODO: `Alignment` should be moved here as well, Rust moved it upstream in 1.96. +pub use crate::ptr::Alignment; + +/// Trait indicating that [`Align`] is a valid alignment. +pub trait ValidAlign { + #[doc(hidden)] + type Repr: Copy; +} + +/// Zero-sized type that provides the alignment specified via the generic parameter. +/// +/// # Examples +/// +/// ``` +/// # use kernel::mem::Align; +/// const ALIGN: usize = 128; +/// struct MyStruct { +/// _align: Align, +/// } +/// assert_eq!(align_of::(), ALIGN); +/// ``` +#[repr(transparent)] +#[derive(Default, Clone, Copy)] +pub struct Align([::Repr; 0]) +where + Self: ValidAlign; + +impl Align +where + Self: ValidAlign, +{ + /// Create a new [`Align`]. + #[inline] + pub const fn new() -> Self { + Align([]) + } +} + +macro_rules! impl_align { + () => {}; + ($a:literal $($rest:literal)*) => { + const _: () = { + #[repr(align($a))] + #[derive(Clone, Copy)] + pub struct Repr; + + impl ValidAlign for Align<$a> { + type Repr = Repr; + } + }; + + impl_align!($($rest)*); + } +} + +impl_align!(1 2 4 8 16 32 64 128 256 512 1024 2048 4096 8192 16384 32768 65536); + +impl core::fmt::Debug for Align +where + Self: ValidAlign, +{ + #[inline] + fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result { + write!(f, "Align<{N}>") + } +} --- base-commit: a87737435cfa134f9cdcc696ba3080759d04cf72 change-id: 20260610-const-align-7020a76367ce Best regards, -- Gary Guo