3 files changed, 146 insertions, 7 deletions
diff --git a/Documentation/rust/coding-guidelines.rst b/Documentation/rust/coding-guidelines.rst
index 27f2a7bb5a4a..6ff9e754755d 100644
--- a/Documentation/rust/coding-guidelines.rst
+++ b/Documentation/rust/coding-guidelines.rst
@@ -85,6 +85,18 @@ written after the documentation, e.g.:
 	    // ...
 	}
 
+This applies to both public and private items. This increases consistency with
+public items, allows changes to visibility with less changes involved and will
+allow us to potentially generate the documentation for private items as well.
+In other words, if documentation is written for a private item, then ``///``
+should still be used. For instance:
+
+.. code-block:: rust
+
+	/// My private function.
+	// TODO: ...
+	fn f() {}
+
 One special kind of comments are the ``// SAFETY:`` comments. These must appear
 before every ``unsafe`` block, and they explain why the code inside the block is
 correct/sound, i.e. why it cannot trigger undefined behavior in any case, e.g.:
@@ -191,6 +203,23 @@ or:
 	/// [`struct mutex`]: srctree/include/linux/mutex.h
 
 
+C FFI types
+-----------
+
+Rust kernel code refers to C types, such as ``int``, using type aliases such as
+``c_int``, which are readily available from the ``kernel`` prelude. Please do
+not use the aliases from ``core::ffi`` -- they may not map to the correct types.
+
+These aliases should generally be referred directly by their identifier, i.e.
+as a single segment path. For instance:
+
+.. code-block:: rust
+
+	fn f(p: *const c_char) -> c_int {
+	    // ...
+	}
+
+
 Naming
 ------
 
diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst
index 6d2607870ba4..155f7107329a 100644
--- a/Documentation/rust/quick-start.rst
+++ b/Documentation/rust/quick-start.rst
@@ -90,15 +90,53 @@ they should generally work out of the box, e.g.::
 Ubuntu
 ******
 
-Ubuntu LTS and non-LTS (interim) releases provide recent Rust releases and thus
-they should generally work out of the box, e.g.::
+25.04
+~~~~~
+
+The latest Ubuntu releases provide recent Rust releases and thus they should
+generally work out of the box, e.g.::
+
+	apt install rustc rust-src bindgen rustfmt rust-clippy
+
+In addition, ``RUST_LIB_SRC`` needs to be set, e.g.::
+
+	RUST_LIB_SRC=/usr/src/rustc-$(rustc --version | cut -d' ' -f2)/library
+
+For convenience, ``RUST_LIB_SRC`` can be exported to the global environment.
 
-	apt install rustc-1.80 rust-1.80-src bindgen-0.65 rustfmt-1.80 rust-1.80-clippy
+
+24.04 LTS and older
+~~~~~~~~~~~~~~~~~~~
+
+Though Ubuntu 24.04 LTS and older versions still provide recent Rust
+releases, they require some additional configuration to be set, using
+the versioned packages, e.g.::
+
+	apt install rustc-1.80 rust-1.80-src bindgen-0.65 rustfmt-1.80 \
+		rust-1.80-clippy
+	ln -s /usr/lib/rust-1.80/bin/rustfmt /usr/bin/rustfmt-1.80
+	ln -s /usr/lib/rust-1.80/bin/clippy-driver /usr/bin/clippy-driver-1.80
+
+None of these packages set their tools as defaults; therefore they should be
+specified explicitly, e.g.::
+
+	make LLVM=1 RUSTC=rustc-1.80 RUSTDOC=rustdoc-1.80 RUSTFMT=rustfmt-1.80 \
+		CLIPPY_DRIVER=clippy-driver-1.80 BINDGEN=bindgen-0.65
+
+Alternatively, modify the ``PATH`` variable to place the Rust 1.80 binaries
+first and set ``bindgen`` as the default, e.g.::
+
+	PATH=/usr/lib/rust-1.80/bin:$PATH
+	update-alternatives --install /usr/bin/bindgen bindgen \
+		/usr/bin/bindgen-0.65 100
+	update-alternatives --set bindgen /usr/bin/bindgen-0.65
 
 ``RUST_LIB_SRC`` needs to be set when using the versioned packages, e.g.::
 
 	RUST_LIB_SRC=/usr/src/rustc-$(rustc-1.80 --version | cut -d' ' -f2)/library
 
+For convenience, ``RUST_LIB_SRC`` can be exported to the global environment.
+
 In addition, ``bindgen-0.65`` is available in newer releases (24.04 LTS and
 24.10), but it may not be available in older ones (20.04 LTS and 22.04 LTS),
 thus ``bindgen`` may need to be built manually (please see below).
diff --git a/Documentation/rust/testing.rst b/Documentation/rust/testing.rst
index f692494f7b74..f43cb77bcc69 100644
--- a/Documentation/rust/testing.rst
+++ b/Documentation/rust/testing.rst
@@ -133,13 +133,85 @@ please see:
 The ``#[test]`` tests
 ---------------------
 
-Additionally, there are the ``#[test]`` tests. These can be run using the
-``rusttest`` Make target::
+Additionally, there are the ``#[test]`` tests. Like for documentation tests,
+these are also fairly similar to what you would expect from userspace, and they
+are also mapped to KUnit.
+
+These tests are introduced by the ``kunit_tests`` procedural macro, which takes
+the name of the test suite as an argument.
+
+For instance, assume we want to test the function ``f`` from the documentation
+tests section. We could write, in the same file where we have our function:
+
+.. code-block:: rust
+
+	#[kunit_tests(rust_kernel_mymod)]
+	mod tests {
+	    use super::*;
+
+	    #[test]
+	    fn test_f() {
+	        assert_eq!(f(10, 20), 30);
+	    }
+	}
+
+And if we run it, the kernel log would look like::
+
+	    KTAP version 1
+	    # Subtest: rust_kernel_mymod
+	    # speed: normal
+	    1..1
+	    # test_f.speed: normal
+	    ok 1 test_f
+	ok 1 rust_kernel_mymod
+
+Like documentation tests, the ``assert!`` and ``assert_eq!`` macros are mapped
+back to KUnit and do not panic. Similarly, the
+`? <https://doc.rust-lang.org/reference/expressions/operator-expr.html#the-question-mark-operator>`_
+operator is supported, i.e. the test functions may return either nothing (i.e.
+the unit type ``()``) or ``Result`` (i.e. any ``Result<T, E>``). For instance:
+
+.. code-block:: rust
+
+	#[kunit_tests(rust_kernel_mymod)]
+	mod tests {
+	    use super::*;
+
+	    #[test]
+	    fn test_g() -> Result {
+	        let x = g()?;
+	        assert_eq!(x, 30);
+	        Ok(())
+	    }
+	}
+
+If we run the test and the call to ``g`` fails, then the kernel log would show::
+
+	    KTAP version 1
+	    # Subtest: rust_kernel_mymod
+	    # speed: normal
+	    1..1
+	    # test_g: ASSERTION FAILED at rust/kernel/lib.rs:335
+	    Expected is_test_result_ok(test_g()) to be true, but is false
+	    # test_g.speed: normal
+	    not ok 1 test_g
+	not ok 1 rust_kernel_mymod
+
+If a ``#[test]`` test could be useful as an example for the user, then please
+use a documentation test instead. Even edge cases of an API, e.g. error or
+boundary cases, can be interesting to show in examples.
+
+The ``rusttest`` host tests
+---------------------------
+
+These are userspace tests that can be built and run in the host (i.e. the one
+that performs the kernel build) using the ``rusttest`` Make target::
 
 	make LLVM=1 rusttest
 
-This requires the kernel ``.config``. It runs the ``#[test]`` tests on the host
-(currently) and thus is fairly limited in what these tests can test.
+This requires the kernel ``.config``.
+
+Currently, they are mostly used for testing the ``macros`` crate's examples.
 
 The Kselftests
 --------------