rust: start using the `#[expect(...)]` attribute

In Rust, it is possible to `allow` particular warnings (diagnostics,
lints) locally, making the compiler ignore instances of a given warning
within a

rust: start using the `#[expect(...)]` attribute

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:

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-function"
static void f(void) {}
#pragma GCC diagnostic pop

But way less verbose:

#[allow(dead_code)]
fn f() {}

By that virtue, it makes it possible to comfortably enable more
diagnostics by default (i.e. outside `W=` levels) that may have some
false positives but that are otherwise quite useful to keep enabled to
catch potential mistakes.

The `#[expect(...)]` attribute [1] takes this further, and makes the
compiler warn if the diagnostic was _not_ produced. For instance, the
following will ensure that, when `f()` is called somewhere, we will have
to remove the attribute:

#[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.

See the next commit for more details, nuances on its usage and
documentation on the feature.

The attribute requires the `lint_reasons` [2] unstable feature, but it
is becoming stable in 1.81.0 (to be released on 2024-09-05) and it has
already been useful to clean things up in this patch series, finding
cases where the `allow`s should not have been there.

Thus, enable `lint_reasons` and convert some of our `allow`s to `expect`s
where possible.

This feature was also an example of the ongoing collaboration between
Rust and the kernel -- we tested it in the kernel early on and found an
issue that was quickly resolved [3].

Cc: Fridtjof Stoldt <[email protected]>
Cc: Urgau <[email protected]>
Link: https://rust-lang.github.io/rfcs/2383-lint-reasons.html#expect-lint-attribute [1]
Link: https://github.com/rust-lang/rust/issues/54503 [2]
Link: https://github.com/rust-lang/rust/issues/114557 [3]
Reviewed-by: Alice Ryhl <[email protected]>
Reviewed-by: Trevor Gross <[email protected]>
Tested-by: Gary Guo <[email protected]>
Reviewed-by: Gary Guo <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Miguel Ojeda <[email protected]>

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rust: kernel: mark code fragments in docs with backticks

Fix places where comments include code fragments that are not enclosed
in backticks.

Signed-off-by: Valentin Obst <[email protected]>
R

rust: kernel: mark code fragments in docs with backticks

Fix places where comments include code fragments that are not enclosed
in backticks.

Signed-off-by: Valentin Obst <[email protected]>
Reviewed-by: Trevor Gross <[email protected]>
Reviewed-by: Martin Rodriguez Reboredo <[email protected]>
Reviewed-by: Alice Ryhl <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Miguel Ojeda <[email protected]>

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rust: ioctl: end top-level module docs with full stop

Every other module ends its first line of documentation with a full
stop. Adapt the only outlier.

Signed-off-by: Valentin Obst <kernel@valentin

rust: ioctl: end top-level module docs with full stop

Every other module ends its first line of documentation with a full
stop. Adapt the only outlier.

Signed-off-by: Valentin Obst <[email protected]>
Reviewed-by: Trevor Gross <[email protected]>
Reviewed-by: Martin Rodriguez Reboredo <[email protected]>
Reviewed-by: Alice Ryhl <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Miguel Ojeda <[email protected]>

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rust: kernel: fix multiple typos in documentation

Fixes multiple trivial typos in documentation and comments of the
kernel crate.

allocator:
- Fix a trivial list item alignment issue in the last SA

rust: kernel: fix multiple typos in documentation

Fixes multiple trivial typos in documentation and comments of the
kernel crate.

allocator:
- Fix a trivial list item alignment issue in the last SAFETY comment of
`krealloc_aligned`.

init:
- Replace 'type' with 'trait' in the doc comments of the `PinInit` and
`Init` traits.
- Add colons before starting lists.
- Add spaces between the type and equal sign to respect the code
formatting rules in example code.
- End a sentence with a full stop instead of a colon.

ioctl:
- Replace 'an' with 'a' where appropriate.

str:
- Replace 'Return' with 'Returns' in the doc comment of `bytes_written`
as the text describes what the function does.

sync/lock:
- Fix a trivial list item alignment issue in the Safety section of the
`Backend` trait's description.

sync/lock/spinlock:
- The code in this module operates on spinlocks, not mutexes. Thus,
replace 'mutex' with 'spinlock' in the SAFETY comment of `unlock`.

workqueue:
- Replace "wont" with "won't" in the doc comment of `__enqueue`.

Signed-off-by: Valentin Obst <[email protected]>
Reviewed-by: Trevor Gross <[email protected]>
Reviewed-by: Martin Rodriguez Reboredo <[email protected]>
Reviewed-by: Alice Ryhl <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Miguel Ojeda <[email protected]>

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rust: support `srctree`-relative links

Some of our links use relative paths in order to point to files in the
source tree, e.g.:

//! C header: [`include/linux/printk.h`](../../../../include/lin

rust: support `srctree`-relative links

Some of our links use relative paths in order to point to files in the
source tree, e.g.:

//! C header: [`include/linux/printk.h`](../../../../include/linux/printk.h)
/// [`struct mutex`]: ../../../../include/linux/mutex.h

These are problematic because they are hard to maintain and do not support
`O=` builds.

Instead, provide support for `srctree`-relative links, e.g.:

//! C header: [`include/linux/printk.h`](srctree/include/linux/printk.h)
/// [`struct mutex`]: srctree/include/linux/mutex.h

The links are fixed after `rustdoc` generation to be based on the absolute
path to the source tree.

Essentially, this is the automatic version of Tomonori's fix [1],
suggested by Gary [2].

Suggested-by: Gary Guo <[email protected]>
Reported-by: FUJITA Tomonori <[email protected]>
Closes: https://lore.kernel.org/r/[email protected] [1]
Fixes: 48fadf440075 ("docs: Move rustdoc output, cross-reference it")
Link: https://lore.kernel.org/rust-for-linux/20231026154525.6d14b495@eugeo/ [2]
Reviewed-by: Martin Rodriguez Reboredo <[email protected]>
Reviewed-by: Benno Lossin <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Miguel Ojeda <[email protected]>

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rust: ioctl: Add ioctl number manipulation functions

Add simple 1:1 wrappers of the C ioctl number manipulation functions.
Since these are macros we cannot bindgen them directly, and since they
shou

rust: ioctl: Add ioctl number manipulation functions

Add simple 1:1 wrappers of the C ioctl number manipulation functions.
Since these are macros we cannot bindgen them directly, and since they
should be usable in const context we cannot use helper wrappers, so
we'll have to reimplement them in Rust. Thankfully, the C headers do
declare defines for the relevant bitfield positions, so we don't need
to duplicate that.

Signed-off-by: Asahi Lina <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
[ Moved the `#![allow(non_snake_case)]` to the usual place. ]
Signed-off-by: Miguel Ojeda <[email protected]>

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