linux-kernel - [PATCH v3 3/3] rust: alloc: Add doctest for `ArrayLayout`

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Message-ID: <e683a5df7d66cca81d762803d602fba62bdd5905.1734477232.git.jtostler1@gmail.com>
Date: Tue, 17 Dec 2024 16:23:12 -0800
From: Jimmy Ostler <jtostler1@...il.com>
To: Danilo Krummrich <dakr@...nel.org>,
	Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>,
	Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>,
	Trevor Gross <tmgross@...ch.edu>,
	Wedson Almeida Filho <walmeida@...rosoft.com>,
	Filipe Xavier <felipe_life@...e.com>,
	Valentin Obst <kernel@...entinobst.de>,
	Daniel Sedlak <daniel@...lak.dev>,
	Alex Mantel <alexmantel93@...lbox.org>
Cc: rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jimmy Ostler <jtostler1@...il.com>
Subject: [PATCH v3 3/3] rust: alloc: Add doctest for `ArrayLayout`

Add a rustdoc example and Kunit test to the `ArrayLayout` struct's
`ArrayLayout::new()` function.

This patch depends on the first patch in this series in order for the
kunit test to compile.

Suggested-by: Boqun Feng <boqun.feng@...il.com>
Link: https://github.com/Rust-for-Linux/linux/issues/1131
Signed-off-by: Jimmy Ostler <jtostler1@...il.com>
---
 rust/kernel/alloc/layout.rs | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/rust/kernel/alloc/layout.rs b/rust/kernel/alloc/layout.rs
index 4b3cd7fdc816..0e053dcc7941 100644
--- a/rust/kernel/alloc/layout.rs
+++ b/rust/kernel/alloc/layout.rs
@@ -43,6 +43,25 @@ pub const fn empty() -> Self {
     /// # Errors
     ///
     /// When `len * size_of::<T>()` overflows or when `len * size_of::<T>() > isize::MAX`.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// # use kernel::alloc::layout::{ArrayLayout, LayoutError};
+    /// let layout = ArrayLayout::<i32>::new(15)?;
+    /// assert_eq!(layout.len(), 15);
+    ///
+    /// // Errors because `len * size_of::<T>()` overflows
+    /// let layout = ArrayLayout::<i32>::new(isize::MAX as usize);
+    /// assert!(layout.is_err());
+    ///
+    /// // Errors because `len * size_of::<i32>() > isize::MAX`,
+    /// // even though `len < isize::MAX`
+    /// let layout = ArrayLayout::<i32>::new(isize::MAX as usize / 2);
+    /// assert!(layout.is_err());
+    ///
+    /// # Ok::<(), Error>(())
+    /// ```
     pub const fn new(len: usize) -> Result<Self, LayoutError> {
         match len.checked_mul(core::mem::size_of::<T>()) {
             Some(size) if size <= ISIZE_MAX => {
-- 
2.47.1