linux-toradex.git/rust/kernel/print.rs, branch v6.18-rc6

rust: use `kernel::{fmt,prelude::fmt!}`

2025-07-20T23:16:35+00:00

Reduce coupling to implementation details of the formatting machinery by
avoiding direct use for `core`'s formatting traits and macros.

Signed-off-by: Tamir Duberstein 
Reviewed-by: Benno Lossin 
Reviewed-by: Alice Ryhl 
Link: https://lore.kernel.org/r/20250704-core-cstr-prepare-v1-3-a91524037783@gmail.com
Signed-off-by: Miguel Ojeda

rust: enable `clippy::ptr_as_ptr` lint

2025-06-22T21:08:42+00:00

In Rust 1.51.0, Clippy introduced the `ptr_as_ptr` lint [1]:

> Though `as` casts between raw pointers are not terrible,
> `pointer::cast` is safer because it cannot accidentally change the
> pointer's mutability, nor cast the pointer to other types like `usize`.

There are a few classes of changes required:
- Modules generated by bindgen are marked
  `#[allow(clippy::ptr_as_ptr)]`.
- Inferred casts (` as _`) are replaced with `.cast()`.
- Ascribed casts (` as *... T`) are replaced with `.cast::()`.
- Multistep casts from references (` as *const _ as *const T`) are
  replaced with `core::ptr::from_ref(&x).cast()` with or without `::`
  according to the previous rules. The `core::ptr::from_ref` call is
  required because `(x as *const _).cast::()` results in inference
  failure.
- Native literal C strings are replaced with `c_str!().as_char_ptr()`.
- `*mut *mut T as _` is replaced with `let *mut *const T = (*mut *mut
  T)`.cast();` since pointer to pointer can be confusing.

Apply these changes and enable the lint -- no functional change
intended.

Link: https://rust-lang.github.io/rust-clippy/master/index.html#ptr_as_ptr [1]
Reviewed-by: Benno Lossin 
Reviewed-by: Boqun Feng 
Signed-off-by: Tamir Duberstein 
Acked-by: Viresh Kumar 
Acked-by: Greg Kroah-Hartman 
Acked-by: Tejun Heo 
Acked-by: Danilo Krummrich 
Link: https://lore.kernel.org/r/20250615-ptr-as-ptr-v12-1-f43b024581e8@gmail.com
[ Added `.cast()` for `opp`. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: replace rustdoc references to alloc::format

2025-05-11T22:20:25+00:00

Replace alloc::format[1] in the pr_* and dev_* macros' doc comments
with std::format[2] because they are identical but less likely to get
confused with the kernel's alloc crate.

And add a url link for the std::format! macro.

Link: https://doc.rust-lang.org/alloc/macro.format.html [1]
Link: https://doc.rust-lang.org/std/macro.format.html [2]
Reviewed-by: Benno Lossin 
Signed-off-by: Andrew Ballance 
Link: https://lore.kernel.org/r/20250325133352.441425-1-andrewjballance@gmail.com
[ Fixed typo and reworded slightly. - Miguel ]
Signed-off-by: Miguel Ojeda

print: use new #[export] macro for rust_fmt_argument

2025-03-09T19:52:46+00:00

This moves the rust_fmt_argument function over to use the new #[export]
macro, which will verify at compile-time that the function signature
matches what is in the header file.

Reviewed-by: Andreas Hindborg 
Reviewed-by: Tamir Duberstein 
Acked-by: Greg Kroah-Hartman 
Signed-off-by: Alice Ryhl 
Acked-by: Petr Mladek 
Link: https://lore.kernel.org/r/20250303-export-macro-v3-4-41fbad85a27f@google.com
[ Removed period as requested by Andy. - Miguel ]
Signed-off-by: Miguel Ojeda

rust: fix signature of rust_fmt_argument

2025-03-09T19:52:46+00:00

Without this change, the rest of this series will emit the following
error message:

error[E0308]: `if` and `else` have incompatible types
  --> /rust/kernel/print.rs:22:22
   |
21 | #[export]
   | --------- expected because of this
22 | unsafe extern "C" fn rust_fmt_argument(
   |                      ^^^^^^^^^^^^^^^^^ expected `u8`, found `i8`
   |
   = note: expected fn item `unsafe extern "C" fn(*mut u8, *mut u8, *mut c_void) -> *mut u8 {bindings::rust_fmt_argument}`
              found fn item `unsafe extern "C" fn(*mut i8, *mut i8, *const c_void) -> *mut i8 {print::rust_fmt_argument}`

The error may be different depending on the architecture.

To fix this, change the void pointer argument to use a const pointer,
and change the imports to use crate::ffi instead of core::ffi for
integer types.

Fixes: 787983da7718 ("vsprintf: add new `%pA` format specifier")
Reviewed-by: Tamir Duberstein 
Acked-by: Greg Kroah-Hartman 
Signed-off-by: Alice Ryhl 
Acked-by: Petr Mladek 
Link: https://lore.kernel.org/r/20250303-export-macro-v3-1-41fbad85a27f@google.com
Signed-off-by: Miguel Ojeda

rust: cleanup unnecessary casts

2024-12-16T20:49:33+00:00

With `long` mapped to `isize`, `size_t`/`__kernel_size_t` mapped to
`usize` and `char` mapped to `u8`, many of the existing casts are no
longer necessary.

Signed-off-by: Gary Guo 
Reviewed-by: Alice Ryhl 
Link: https://lore.kernel.org/r/20240913213041.395655-6-gary@garyguo.net
[ Moved `uaccess` changes to the previous commit, since they were
  irrefutable patterns that Rust >= 1.82.0 warns about. Removed a
  couple casts that now use `c""` literals. Rebased on top of
  `rust-next`. - Miguel ]
Signed-off-by: Miguel Ojeda

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

2024-10-07T19:39:57+00:00

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 
Cc: Urgau 
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 
Reviewed-by: Trevor Gross 
Tested-by: Gary Guo 
Reviewed-by: Gary Guo 
Link: https://lore.kernel.org/r/20240904204347.168520-18-ojeda@kernel.org
Signed-off-by: Miguel Ojeda

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

2024-10-07T19:39:57+00:00

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 
Reviewed-by: Alice Ryhl 
Tested-by: Gary Guo 
Reviewed-by: Gary Guo 
Link: https://lore.kernel.org/r/20240904204347.168520-16-ojeda@kernel.org
Signed-off-by: Miguel Ojeda

rust: enable `clippy::undocumented_unsafe_blocks` lint

2024-10-07T19:39:05+00:00

Checking that we are not missing any `// SAFETY` comments in our `unsafe`
blocks is something we have wanted to do for a long time, as well as
cleaning up the remaining cases that were not documented [1].

Back when Rust for Linux started, this was something that could have
been done via a script, like Rust's `tidy`. Soon after, in Rust 1.58.0,
Clippy implemented the `undocumented_unsafe_blocks` lint [2].

Even though the lint has a few false positives, e.g. in some cases where
attributes appear between the comment and the `unsafe` block [3], there
are workarounds and the lint seems quite usable already.

Thus enable the lint now.

We still have a few cases to clean up, so just allow those for the moment
by writing a `TODO` comment -- some of those may be good candidates for
new contributors.

Link: https://github.com/Rust-for-Linux/linux/issues/351 [1]
Link: https://rust-lang.github.io/rust-clippy/master/#/undocumented_unsafe_blocks [2]
Link: https://github.com/rust-lang/rust-clippy/issues/13189 [3]
Reviewed-by: Alice Ryhl 
Reviewed-by: Trevor Gross 
Tested-by: Gary Guo 
Reviewed-by: Gary Guo 
Link: https://lore.kernel.org/r/20240904204347.168520-5-ojeda@kernel.org
Signed-off-by: Miguel Ojeda

rust: kernel: use docs.kernel.org links in code documentation

2024-08-25T12:44:34+00:00

Use links to docs.kernel.org instead of www.kernel.org/doc/html/latest
in the code documentation. The links are shorter and cleaner.

Link: https://github.com/Rust-for-Linux/linux/issues/1101
Signed-off-by: Michael Vetter 
[ Reworded slightly. - Miguel ]
Signed-off-by: Miguel Ojeda