1 files changed, 102 insertions, 0 deletions
diff --git a/rust/kernel/debugfs/traits.rs b/rust/kernel/debugfs/traits.rs
new file mode 100644
index 000000000000..ab009eb254b3
--- /dev/null
+++ b/rust/kernel/debugfs/traits.rs
@@ -0,0 +1,102 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2025 Google LLC.
+
+//! Traits for rendering or updating values exported to DebugFS.
+
+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,
+    AtomicU8, AtomicUsize, Ordering,
+};
+
+/// A trait for types that can be written into a string.
+///
+/// This works very similarly to `Debug`, and is automatically implemented if `Debug` is
+/// implemented for a type. It is also implemented for any writable type inside a `Mutex`.
+///
+/// The derived implementation of `Debug` [may
+/// change](https://doc.rust-lang.org/std/fmt/trait.Debug.html#stability)
+/// between Rust versions, so if stability is key for your use case, please implement `Writer`
+/// explicitly instead.
+pub trait Writer {
+    /// Formats the value using the given formatter.
+    fn write(&self, f: &mut Formatter<'_>) -> fmt::Result;
+}
+
+impl<T: Writer> Writer for Mutex<T> {
+    fn write(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        self.lock().write(f)
+    }
+}
+
+impl<T: Debug> Writer for T {
+    fn write(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        writeln!(f, "{self:?}")
+    }
+}
+
+/// A trait for types that can be updated from a user slice.
+///
+/// This works similarly to `FromStr`, but operates on a `UserSliceReader` rather than a &str.
+///
+/// It is automatically implemented for all atomic integers, or any type that implements `FromStr`
+/// wrapped in a `Mutex`.
+pub trait Reader {
+    /// Updates the value from the given user slice.
+    fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result;
+}
+
+impl<T: FromStr> Reader for Mutex<T> {
+    fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
+        let mut buf = [0u8; 128];
+        if reader.len() > buf.len() {
+            return Err(EINVAL);
+        }
+        let n = reader.len();
+        reader.read_slice(&mut buf[..n])?;
+
+        let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?;
+        let val = s.trim().parse::<T>().map_err(|_| EINVAL)?;
+        *self.lock() = val;
+        Ok(())
+    }
+}
+
+macro_rules! impl_reader_for_atomic {
+    ($(($atomic_type:ty, $int_type:ty)),*) => {
+        $(
+            impl Reader for $atomic_type {
+                fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
+                    let mut buf = [0u8; 21]; // Enough for a 64-bit number.
+                    if reader.len() > buf.len() {
+                        return Err(EINVAL);
+                    }
+                    let n = reader.len();
+                    reader.read_slice(&mut buf[..n])?;
+
+                    let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?;
+                    let val = s.trim().parse::<$int_type>().map_err(|_| EINVAL)?;
+                    self.store(val, Ordering::Relaxed);
+                    Ok(())
+                }
+            }
+        )*
+    };
+}
+
+impl_reader_for_atomic!(
+    (AtomicI16, i16),
+    (AtomicI32, i32),
+    (AtomicI64, i64),
+    (AtomicI8, i8),
+    (AtomicIsize, isize),
+    (AtomicU16, u16),
+    (AtomicU32, u32),
+    (AtomicU64, u64),
+    (AtomicU8, u8),
+    (AtomicUsize, usize)
+);