rust: debugfs: use kernel::fmt

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

This backslid in commit 40ecc49466 ("rust: debugfs: Add support for
callback-based files") and commit 5e40b591cb ("rust: debugfs: Add
support for read-only files").

Acked-by: Danilo Krummrich <dakr@kernel.org>
Reviewed-by: Matthew Maurer <mmaurer@google.com>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Link: https://patch.msgid.link/20251018-cstr-core-v18-7-9378a54385f8@gmail.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/kernel/debugfs.rs

@@ -8,12 +8,12 @@
 // When DebugFS is disabled, many parameters are dead. Linting for this isn't helpful.
 #![cfg_attr(not(CONFIG_DEBUG_FS), allow(unused_variables))]
 
+use crate::fmt;
 use crate::prelude::*;
 use crate::str::CStr;
 #[cfg(CONFIG_DEBUG_FS)]
 use crate::sync::Arc;
 use crate::uaccess::UserSliceReader;
-use core::fmt;
 use core::marker::PhantomData;
 use core::marker::PhantomPinned;
 #[cfg(CONFIG_DEBUG_FS)]

rust/kernel/debugfs/callback_adapters.rs

@@ -5,10 +5,9 @@
 //! than a trait implementation. If provided, it will override the trait implementation.
 
 use super::{Reader, Writer};
+use crate::fmt;
 use crate::prelude::*;
 use crate::uaccess::UserSliceReader;
-use core::fmt;
-use core::fmt::Formatter;
 use core::marker::PhantomData;
 use core::ops::Deref;
 
@@ -76,9 +75,9 @@ impl<D, F> Deref for FormatAdapter<D, F> {
 
 impl<D, F> Writer for FormatAdapter<D, F>
 where
-    F: Fn(&D, &mut Formatter<'_>) -> fmt::Result + 'static,
+    F: Fn(&D, &mut fmt::Formatter<'_>) -> fmt::Result + 'static,
 {
-    fn write(&self, fmt: &mut Formatter<'_>) -> fmt::Result {
+    fn write(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
         // SAFETY: FormatAdapter<_, F> can only be constructed if F is inhabited
         let f: &F = unsafe { materialize_zst() };
         f(&self.inner, fmt)

rust/kernel/debugfs/file_ops.rs

@@ -3,11 +3,11 @@
 
 use super::{Reader, Writer};
 use crate::debugfs::callback_adapters::Adapter;
+use crate::fmt;
 use crate::prelude::*;
 use crate::seq_file::SeqFile;
 use crate::seq_print;
 use crate::uaccess::UserSlice;
-use core::fmt::{Display, Formatter, Result};
 use core::marker::PhantomData;
 
 #[cfg(CONFIG_DEBUG_FS)]
@@ -65,8 +65,8 @@ impl<T> Deref for FileOps<T> {
 
 struct WriterAdapter<T>(T);
 
-impl<'a, T: Writer> Display for WriterAdapter<&'a T> {
-    fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+impl<'a, T: Writer> fmt::Display for WriterAdapter<&'a T> {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.0.write(f)
     }
 }

rust/kernel/debugfs/traits.rs

@@ -3,10 +3,10 @@
 
 //! Traits for rendering or updating values exported to DebugFS.
 
+use crate::fmt;
 use crate::prelude::*;
 use crate::sync::Mutex;
 use crate::uaccess::UserSliceReader;
-use core::fmt::{self, Debug, Formatter};
 use core::str::FromStr;
 use core::sync::atomic::{
     AtomicI16, AtomicI32, AtomicI64, AtomicI8, AtomicIsize, AtomicU16, AtomicU32, AtomicU64,
@@ -24,17 +24,17 @@ use core::sync::atomic::{
 /// explicitly instead.
 pub trait Writer {
     /// Formats the value using the given formatter.
-    fn write(&self, f: &mut Formatter<'_>) -> fmt::Result;
+    fn write(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result;
 }
 
 impl<T: Writer> Writer for Mutex<T> {
-    fn write(&self, f: &mut Formatter<'_>) -> fmt::Result {
+    fn write(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         self.lock().write(f)
     }
 }
 
-impl<T: Debug> Writer for T {
-    fn write(&self, f: &mut Formatter<'_>) -> fmt::Result {
+impl<T: fmt::Debug> Writer for T {
+    fn write(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
         writeln!(f, "{self:?}")
     }
 }