[PATCH v9 16/31] rust: ptr: add const_align_up()

John Hubbard
2026-03-26T01:39:39Z

Add const_align_up() to kernel::ptr as the const-compatible equivalent
of Alignable::align_up().

Suggested-by: Danilo Krummrich <dakr@kernel.org>
Suggested-by: Gary Guo <gary@garyguo.net>
Suggested-by: Miguel Ojeda <ojeda@kernel.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: John Hubbard <jhubbard@nvidia.com>
---
rust/kernel/ptr.rs | 24 ++++++++++++++++++++++++
1 file changed, 24 insertions(+)

diff --git a/rust/kernel/ptr.rs b/rust/kernel/ptr.rs
index bdc2d79ff669..7e99f129543b 100644
--- a/rust/kernel/ptr.rs
+++ b/rust/kernel/ptr.rs
@@ -253,3 +253,27 @@ fn size(p: *const Self) -> usize {
p.len() * size_of::<T>()
}
}
+
+/// Aligns `value` up to `align`.
+///
+/// This is the const-compatible equivalent of [`Alignable::align_up`].
+///
+/// Returns [`None`] on overflow.
+///
+/// # Examples
+///
+/// ```
+/// use kernel::ptr::{const_align_up, Alignment};
+/// use kernel::sizes::SZ_4K;
+///
+/// assert_eq!(const_align_up(0x4f, Alignment::new::<16>()), Some(0x50));
+/// assert_eq!(const_align_up(0x40, Alignment::new::<16>()), Some(0x40));
+/// assert_eq!(const_align_up(1, Alignment::new::<SZ_4K>()), Some(SZ_4K));
+/// ```
+#[inline(always)]
+pub const fn const_align_up(value: usize, align: Alignment) -> Option<usize> {
+ match value.checked_add(align.as_usize() - 1) {
+ Some(v) => Some(v & align.mask()),
+ None => None,
+ }
+}
--
2.53.0