From: John Hubbard <jhubbard@nvidia.com>
Date: Thu, 26 Mar 2026 01:38:47 +0000 (-0700)
Subject: rust: ptr: add const_align_up()
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=0a51b384e0decfe9dfe65d721a5e9cd39cabc152;p=thirdparty%2Fkernel%2Flinux.git

rust: ptr: add const_align_up()

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>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Link: https://patch.msgid.link/20260326013902.588242-17-jhubbard@nvidia.com
[ Adjusted imports style. - Miguel ]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---

diff --git a/rust/kernel/ptr.rs b/rust/kernel/ptr.rs
index 512e2eabe3ad6..c7788656a1621 100644
--- a/rust/kernel/ptr.rs
+++ b/rust/kernel/ptr.rs
@@ -225,3 +225,32 @@ macro_rules! impl_alignable_uint {
 }
 
 impl_alignable_uint!(u8, u16, u32, u64, usize);
+
+/// 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, //
+///     },
+///     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,
+    }
+}