2 files changed, 163 insertions, 0 deletions
diff --git a/Documentation/rust/coding-guidelines.rst b/Documentation/rust/coding-guidelines.rst
index 329b070a1d47..a2e326b42410 100644
--- a/Documentation/rust/coding-guidelines.rst
+++ b/Documentation/rust/coding-guidelines.rst
@@ -227,3 +227,149 @@ The equivalent in Rust may look like (ignoring documentation):
 That is, the equivalent of ``GPIO_LINE_DIRECTION_IN`` would be referred to as
 ``gpio::LineDirection::In``. In particular, it should not be named
 ``gpio::gpio_line_direction::GPIO_LINE_DIRECTION_IN``.
+
+
+Lints
+-----
+
+In Rust, it is possible to ``allow`` particular warnings (diagnostics, lints)
+locally, making the compiler ignore instances of a given warning within a given
+function, module, block, etc.
+
+It is similar to ``#pragma GCC diagnostic push`` + ``ignored`` + ``pop`` in C
+[#]_:
+
+.. code-block:: c
+
+	#pragma GCC diagnostic push
+	#pragma GCC diagnostic ignored "-Wunused-function"
+	static void f(void) {}
+	#pragma GCC diagnostic pop
+
+.. [#] In this particular case, the kernel's ``__{always,maybe}_unused``
+       attributes (C23's ``[[maybe_unused]]``) may be used; however, the example
+       is meant to reflect the equivalent lint in Rust discussed afterwards.
+
+But way less verbose:
+
+.. code-block:: rust
+
+	#[allow(dead_code)]
+	fn f() {}
+
+By that virtue, it makes it possible to comfortably enable more diagnostics by
+default (i.e. outside ``W=`` levels). In particular, those that may have some
+false positives but that are otherwise quite useful to keep enabled to catch
+potential mistakes.
+
+On top of that, Rust provides the ``expect`` attribute which takes this further.
+It makes the compiler warn if the warning was not produced. For instance, the
+following will ensure that, when ``f()`` is called somewhere, we will have to
+remove the attribute:
+
+.. code-block:: rust
+
+	#[expect(dead_code)]
+	fn f() {}
+
+If we do not, we get a warning from the compiler::
+
+	warning: this lint expectation is unfulfilled
+	 --> x.rs:3:10
+	  |
+	3 | #[expect(dead_code)]
+	  |          ^^^^^^^^^
+	  |
+	  = note: `#[warn(unfulfilled_lint_expectations)]` on by default
+
+This means that ``expect``\ s do not get forgotten when they are not needed, which
+may happen in several situations, e.g.:
+
+- Temporary attributes added while developing.
+
+- Improvements in lints in the compiler, Clippy or custom tools which may
+  remove a false positive.
+
+- When the lint is not needed anymore because it was expected that it would be
+  removed at some point, such as the ``dead_code`` example above.
+
+It also increases the visibility of the remaining ``allow``\ s and reduces the
+chance of misapplying one.
+
+Thus prefer ``expect`` over ``allow`` unless:
+
+- Conditional compilation triggers the warning in some cases but not others.
+
+  If there are only a few cases where the warning triggers (or does not
+  trigger) compared to the total number of cases, then one may consider using
+  a conditional ``expect`` (i.e. ``cfg_attr(..., expect(...))``). Otherwise,
+  it is likely simpler to just use ``allow``.
+
+- Inside macros, when the different invocations may create expanded code that
+  triggers the warning in some cases but not in others.
+
+- When code may trigger a warning for some architectures but not others, such
+  as an ``as`` cast to a C FFI type.
+
+As a more developed example, consider for instance this program:
+
+.. code-block:: rust
+
+	fn g() {}
+
+	fn main() {
+	    #[cfg(CONFIG_X)]
+	    g();
+	}
+
+Here, function ``g()`` is dead code if ``CONFIG_X`` is not set. Can we use
+``expect`` here?
+
+.. code-block:: rust
+
+	#[expect(dead_code)]
+	fn g() {}
+
+	fn main() {
+	    #[cfg(CONFIG_X)]
+	    g();
+	}
+
+This would emit a lint if ``CONFIG_X`` is set, since it is not dead code in that
+configuration. Therefore, in cases like this, we cannot use ``expect`` as-is.
+
+A simple possibility is using ``allow``:
+
+.. code-block:: rust
+
+	#[allow(dead_code)]
+	fn g() {}
+
+	fn main() {
+	    #[cfg(CONFIG_X)]
+	    g();
+	}
+
+An alternative would be using a conditional ``expect``:
+
+.. code-block:: rust
+
+	#[cfg_attr(not(CONFIG_X), expect(dead_code))]
+	fn g() {}
+
+	fn main() {
+	    #[cfg(CONFIG_X)]
+	    g();
+	}
+
+This would ensure that, if someone introduces another call to ``g()`` somewhere
+(e.g. unconditionally), then it would be spotted that it is not dead code
+anymore. However, the ``cfg_attr`` is more complex than a simple ``allow``.
+
+Therefore, it is likely that it is not worth using conditional ``expect``\ s when
+more than one or two configurations are involved or when the lint may be
+triggered due to non-local changes (such as ``dead_code``).
+
+For more information about diagnostics in Rust, please see:
+
+	https://doc.rust-lang.org/stable/reference/attributes/diagnostics.html
diff --git a/Documentation/rust/quick-start.rst b/Documentation/rust/quick-start.rst
index 2d107982c87b..4aa50e5fcb8c 100644
--- a/Documentation/rust/quick-start.rst
+++ b/Documentation/rust/quick-start.rst
@@ -87,6 +87,23 @@ they should generally work out of the box, e.g.::
 	zypper install rust rust1.79-src rust-bindgen clang
 
 
+Ubuntu
+******
+
+Ubuntu LTS and non-LTS (interim) releases provide recent Rust releases and thus
+they should generally work out of the box, e.g.::
+
+	apt install rustc-1.80 rust-1.80-src bindgen-0.65 rustfmt-1.80 rust-1.80-clippy
+
+``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
+
+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).
+
+
 Requirements: Building
 ----------------------