kernel/debugfs/
traits.rs

1// SPDX-License-Identifier: GPL-2.0
2// Copyright (C) 2025 Google LLC.
3
4//! Traits for rendering or updating values exported to DebugFS.
5
6use crate::fmt;
7use crate::prelude::*;
8use crate::sync::atomic::{Atomic, AtomicBasicOps, AtomicType, Relaxed};
9use crate::sync::Mutex;
10use crate::uaccess::UserSliceReader;
11use core::str::FromStr;
12
13/// A trait for types that can be written into a string.
14///
15/// This works very similarly to `Debug`, and is automatically implemented if `Debug` is
16/// implemented for a type. It is also implemented for any writable type inside a `Mutex`.
17///
18/// The derived implementation of `Debug` [may
19/// change](https://doc.rust-lang.org/std/fmt/trait.Debug.html#stability)
20/// between Rust versions, so if stability is key for your use case, please implement `Writer`
21/// explicitly instead.
22pub trait Writer {
23    /// Formats the value using the given formatter.
24    fn write(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result;
25}
26
27impl<T: Writer> Writer for Mutex<T> {
28    fn write(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
29        self.lock().write(f)
30    }
31}
32
33impl<T: fmt::Debug> Writer for T {
34    fn write(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
35        writeln!(f, "{self:?}")
36    }
37}
38
39/// A trait for types that can be updated from a user slice.
40///
41/// This works similarly to `FromStr`, but operates on a `UserSliceReader` rather than a &str.
42///
43/// It is automatically implemented for all atomic integers, or any type that implements `FromStr`
44/// wrapped in a `Mutex`.
45pub trait Reader {
46    /// Updates the value from the given user slice.
47    fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result;
48}
49
50impl<T: FromStr + Unpin> Reader for Mutex<T> {
51    fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
52        let mut buf = [0u8; 128];
53        if reader.len() > buf.len() {
54            return Err(EINVAL);
55        }
56        let n = reader.len();
57        reader.read_slice(&mut buf[..n])?;
58
59        let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?;
60        let val = s.trim().parse::<T>().map_err(|_| EINVAL)?;
61        *self.lock() = val;
62        Ok(())
63    }
64}
65
66impl<T: AtomicType + FromStr> Reader for Atomic<T>
67where
68    T::Repr: AtomicBasicOps,
69{
70    fn read_from_slice(&self, reader: &mut UserSliceReader) -> Result {
71        let mut buf = [0u8; 21]; // Enough for a 64-bit number.
72        if reader.len() > buf.len() {
73            return Err(EINVAL);
74        }
75        let n = reader.len();
76        reader.read_slice(&mut buf[..n])?;
77
78        let s = core::str::from_utf8(&buf[..n]).map_err(|_| EINVAL)?;
79        let val = s.trim().parse::<T>().map_err(|_| EINVAL)?;
80        self.store(val, Relaxed);
81        Ok(())
82    }
83}
kernel/debugfs/traits.rs

kernel/debugfs/
traits.rs
