rust: clean Rust 1.88.0's warning about `clippy::disallowed_macros` configuration

Starting with Rust 1.88.0 (expected 2025-06-26) [1], Clippy may start
warning about paths that do not resolve in the

rust: clean Rust 1.88.0's warning about `clippy::disallowed_macros` configuration

Starting with Rust 1.88.0 (expected 2025-06-26) [1], Clippy may start
warning about paths that do not resolve in the `disallowed_macros`
configuration:

warning: `kernel::dbg` does not refer to an existing macro
--> .clippy.toml:10:5
|
10 | { path = "kernel::dbg", reason = "the `dbg!` macro is intended as a debugging tool" },
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

This is a lint we requested at [2], due to the trouble debugging
the lint due to false negatives (e.g. [3]), which we use to emulate
`clippy::dbg_macro` [4]. See commit 8577c9dca799 ("rust: replace
`clippy::dbg_macro` with `disallowed_macros`") for more details.

Given the false negatives are not resolved yet, it is expected that
Clippy complains about not finding this macro.

Thus, until the false negatives are fixed (and, even then, probably we
will need to wait for the MSRV to raise enough), use the escape hatch
to allow an invalid path.

Cc: [email protected] # Needed in 6.12.y and later (Rust is pinned in older LTSs).
Link: https://github.com/rust-lang/rust-clippy/pull/14397 [1]
Link: https://github.com/rust-lang/rust-clippy/issues/11432 [2]
Link: https://github.com/rust-lang/rust-clippy/issues/11431 [3]
Link: https://github.com/rust-lang/rust-clippy/issues/11303 [4]
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: give Clippy the minimum supported Rust version

Clippy's lints may avoid emitting a suggestion to use a language or
library feature that is not supported by the minimum supported version,
if gi

rust: give Clippy the minimum supported Rust version

Clippy's lints may avoid emitting a suggestion to use a language or
library feature that is not supported by the minimum supported version,
if given by the `msrv` field in the configuration file.

For instance, Clippy should not suggest using `let ... else` in a lint
if the MSRV did not implement that syntax.

If the MSRV is not provided, Clippy will assume all features are available.

Thus enable it with the minimum Rust version the kernel supports.

Note that there is currently a small disadvantage in doing so: since
we still use unstable features that nevertheless work in the range
of versions we support (e.g. `#[expect(...)]`), we lose suggestions
for those. However, over time we will stop using unstable features
(especially language and library ones) as it is our goal, thus, in the
end, we will want to have the `msrv` set.

Rust is also considering adding a similar feature in `rustc` too, which
we should probably enable if it becomes available [2].

Link: https://github.com/rust-lang/rust-clippy/blob/8298da72e7b81fa30c515631b40fc4c0845948cb/clippy_utils/src/msrvs.rs#L20 [1]
Link: https://github.com/rust-lang/compiler-team/issues/772 [2]
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: enable Clippy's `check-private-items`

In Rust 1.76.0, Clippy added the `check-private-items` lint configuration
option. When turned on (the default is off), it makes several lints
check privat

rust: enable Clippy's `check-private-items`

In Rust 1.76.0, Clippy added the `check-private-items` lint configuration
option. When turned on (the default is off), it makes several lints
check private items as well.

In our case, it affects two lints we have enabled [1]:
`missing_safety_doc` and `unnecessary_safety_doc`.

It also seems to affect the new `too_long_first_doc_paragraph` lint [2],
even though the documentation does not mention it.

Thus allow the few instances remaining we currently hit and enable
the lint.

Link: https://doc.rust-lang.org/nightly/clippy/lint_configuration.html#check-private-items [1]
Link: https://rust-lang.github.io/rust-clippy/master/index.html#/too_long_first_doc_paragraph [2]
Reviewed-by: Trevor Gross <[email protected]>
Reviewed-by: Alice Ryhl <[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: replace `clippy::dbg_macro` with `disallowed_macros`

Back when we used Rust 1.60.0 (before Rust was merged in the kernel),
we added `-Wclippy::dbg_macro` to the compilation flags. This worked

rust: replace `clippy::dbg_macro` with `disallowed_macros`

Back when we used Rust 1.60.0 (before Rust was merged in the kernel),
we added `-Wclippy::dbg_macro` to the compilation flags. This worked
great with our custom `dbg!` macro (vendored from `std`, but slightly
modified to use the kernel printing facilities).

However, in the very next version, 1.61.0, it stopped working [1] since
the lint started to use a Rust diagnostic item rather than a path to find
the `dbg!` macro [1]. This behavior remains until the current nightly
(1.83.0).

Therefore, currently, the `dbg_macro` is not doing anything, which
explains why we can invoke `dbg!` in samples/rust/rust_print.rs`, as well
as why changing the `#[allow()]`s to `#[expect()]`s in `std_vendor.rs`
doctests does not work since they are not fulfilled.

One possible workaround is using `rustc_attrs` like the standard library
does. However, this is intended to be internal, and we just started
supporting several Rust compiler versions, so it is best to avoid it.

Therefore, instead, use `disallowed_macros`. It is a stable lint and
is more flexible (in that we can provide different macros), although
its diagnostic message(s) are not as nice as the specialized one (yet),
and does not allow to set different lint levels per macro/path [2].

In turn, this requires allowing the (intentional) `dbg!` use in the
sample, as one would have expected.

Finally, in a single case, the `allow` is fixed to be an inner attribute,
since otherwise it was not being applied.

Link: https://github.com/rust-lang/rust-clippy/issues/11303 [1]
Link: https://github.com/rust-lang/rust-clippy/issues/11307 [2]
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: introduce `.clippy.toml`

Some Clippy lints can be configured/tweaked. We will use these knobs to
our advantage in later commits.

This is done via a configuration file, `.clippy.toml` [1]. The

rust: introduce `.clippy.toml`

Some Clippy lints can be configured/tweaked. We will use these knobs to
our advantage in later commits.

This is done via a configuration file, `.clippy.toml` [1]. The file is
currently unstable. This may be a problem in the future, but we can adapt
as needed. In addition, we proposed adding Clippy to the Rust CI's RFL
job [2], so we should be able to catch issues pre-merge.

Thus introduce the file.

Link: https://doc.rust-lang.org/clippy/configuration.html [1]
Link: https://github.com/rust-lang/rust/pull/128928 [2]
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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