Re: [PATCH v17 07/11] rust: debugfs: use `kernel::fmt`

Matthew Maurer
2025-10-15T19:40:13Z

On Wed, Oct 15, 2025 at 12:27 PM Tamir Duberstein <tamird@gmail.com> wrote:
>
> Reduce coupling to implementation details of the formatting machinery by
> avoiding direct use for `core`'s formatting traits and macros.
>
> This backslid in commit 40ecc49466c8 ("rust: debugfs: Add support for
> callback-based files") and commit 5e40b591cb46 ("rust: debugfs: Add
> support for read-only files").
>
> Signed-off-by: Tamir Duberstein <tamird@gmail.com>
> ---
> rust/kernel/debugfs.rs | 2 +-
> rust/kernel/debugfs/callback_adapters.rs | 7 +++----
> rust/kernel/debugfs/file_ops.rs | 6 +++---
> rust/kernel/debugfs/traits.rs | 10 +++++-----
> 4 files changed, 12 insertions(+), 13 deletions(-)
>

Reviewed-by: Matthew Maurer <mmaurer@google.com>

On Wed, Oct 15, 2025 at 12:27 PM Tamir Duberstein <tamird@gmail.com> wrote:
>
> Reduce coupling to implementation details of the formatting machinery by
> avoiding direct use for `core`'s formatting traits and macros.
>
> This backslid in commit 40ecc49466c8 ("rust: debugfs: Add support for
> callback-based files") and commit 5e40b591cb46 ("rust: debugfs: Add
> support for read-only files").
>
> Signed-off-by: Tamir Duberstein <tamird@gmail.com>
> ---
> rust/kernel/debugfs.rs | 2 +-
> rust/kernel/debugfs/callback_adapters.rs | 7 +++----
> rust/kernel/debugfs/file_ops.rs | 6 +++---
> rust/kernel/debugfs/traits.rs | 10 +++++-----
> 4 files changed, 12 insertions(+), 13 deletions(-)
>
> diff --git a/rust/kernel/debugfs.rs b/rust/kernel/debugfs.rs
> index 381c23b3dd83..8c35d032acfe 100644
> --- a/rust/kernel/debugfs.rs
> +++ b/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)]
> diff --git a/rust/kernel/debugfs/callback_adapters.rs b/rust/kernel/debugfs/callback_adapters.rs
> index 6c024230f676..a260d8dee051 100644
> --- a/rust/kernel/debugfs/callback_adapters.rs
> +++ b/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 @@ fn deref(&self) -> &D {
>
> 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)
> diff --git a/rust/kernel/debugfs/file_ops.rs b/rust/kernel/debugfs/file_ops.rs
> index 50fead17b6f3..9ad5e3fa6f69 100644
> --- a/rust/kernel/debugfs/file_ops.rs
> +++ b/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 @@ fn deref(&self) -> &Self::Target {
>
> 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)
> }
> }
> diff --git a/rust/kernel/debugfs/traits.rs b/rust/kernel/debugfs/traits.rs
> index ab009eb254b3..ad33bfbc7669 100644
> --- a/rust/kernel/debugfs/traits.rs
> +++ b/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 @@
> /// 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:?}")
> }
> }
>
> --
> 2.51.0
>
>