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`.

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]
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

Author: ojeda

.clippy.toml

@@ -2,6 +2,8 @@
 
 msrv = "1.78.0"
 
+check-private-items = true
+
 disallowed-macros = [
     # The `clippy::dbg_macro` lint only works with `std::dbg!`, thus we simulate
     # it here, see: https://github.com/rust-lang/rust-clippy/issues/11303.

rust/kernel/init.rs

@@ -125,6 +125,7 @@
 //! use core::{ptr::addr_of_mut, marker::PhantomPinned, pin::Pin};
 //! # mod bindings {
 //! #     #![allow(non_camel_case_types)]
+//! #     #![allow(clippy::missing_safety_doc)]
 //! #     pub struct foo;
 //! #     pub unsafe fn init_foo(_ptr: *mut foo) {}
 //! #     pub unsafe fn destroy_foo(_ptr: *mut foo) {}

rust/kernel/init/__internal.rs

@@ -53,6 +53,7 @@ where
 pub unsafe trait HasPinData {
     type PinData: PinData;
 
+    #[allow(clippy::missing_safety_doc)]
     unsafe fn __pin_data() -> Self::PinData;
 }
 
@@ -82,6 +83,7 @@ pub unsafe trait PinData: Copy {
 pub unsafe trait HasInitData {
     type InitData: InitData;
 
+    #[allow(clippy::missing_safety_doc)]
     unsafe fn __init_data() -> Self::InitData;
 }
 

rust/kernel/init/macros.rs

@@ -989,6 +989,7 @@ macro_rules! __pin_data {
         //
         // The functions are `unsafe` to prevent accidentally calling them.
         #[allow(dead_code)]
+        #[allow(clippy::missing_safety_doc)]
         impl<$($impl_generics)*> $pin_data<$($ty_generics)*>
         where $($whr)*
         {

rust/kernel/print.rs

@@ -14,6 +14,7 @@ use core::{
 use crate::str::RawFormatter;
 
 // Called from `vsprintf` with format specifier `%pA`.
+#[allow(clippy::missing_safety_doc)]
 #[no_mangle]
 unsafe extern "C" fn rust_fmt_argument(
     buf: *mut c_char,