linux-kernel - Re: [PATCH v6 05/18] rust: str: introduce `kstrtobool` function

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Message-Id: <A97ECEE6-25A7-45ED-8547-527AC4362BA6@collabora.com>
Date: Wed, 27 Aug 2025 10:10:42 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: Boqun Feng <boqun.feng@...il.com>,
 Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>,
 Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <lossin@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>,
 Danilo Krummrich <dakr@...nel.org>,
 Jens Axboe <axboe@...nel.dk>,
 Breno Leitao <leitao@...ian.org>,
 linux-block@...r.kernel.org,
 rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 05/18] rust: str: introduce `kstrtobool` function



> On 22 Aug 2025, at 09:14, Andreas Hindborg <a.hindborg@...nel.org> wrote:
> 
> Add a Rust wrapper for the kernel's `kstrtobool` function that converts
> common user inputs into boolean values.
> 
> Signed-off-by: Andreas Hindborg <a.hindborg@...nel.org>
> ---
> rust/kernel/str.rs | 57 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
> 1 file changed, 57 insertions(+)
> 
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index d8326f7bc9c1..d070c0bd86c3 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -4,6 +4,7 @@
> 
> use crate::{
>     alloc::{flags::*, AllocError, KVec},
> +    error::Result,
>     fmt::{self, Write},
>     prelude::*,
> };
> @@ -920,6 +921,62 @@ fn write_str(&mut self, s: &str) -> fmt::Result {
>     }
> }
> 
> +/// Convert common user inputs into boolean values using the kernel's `kstrtobool` function.
> +///
> +/// This routine returns `Ok(bool)` if the first character is one of 'YyTt1NnFf0', or
> +/// \[oO\]\[NnFf\] for "on" and "off". Otherwise it will return `Err(EINVAL)`.
> +///
> +/// # Examples
> +///
> +/// ```
> +/// # use kernel::{c_str, str::kstrtobool};
> +///
> +/// // Lowercase
> +/// assert_eq!(kstrtobool(c_str!("true")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("tr")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("t")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("twrong")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("false")), Ok(false));
> +/// assert_eq!(kstrtobool(c_str!("f")), Ok(false));
> +/// assert_eq!(kstrtobool(c_str!("yes")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("no")), Ok(false));
> +/// assert_eq!(kstrtobool(c_str!("on")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("off")), Ok(false));
> +///
> +/// // Camel case
> +/// assert_eq!(kstrtobool(c_str!("True")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("False")), Ok(false));
> +/// assert_eq!(kstrtobool(c_str!("Yes")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("No")), Ok(false));
> +/// assert_eq!(kstrtobool(c_str!("On")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("Off")), Ok(false));
> +///
> +/// // All caps
> +/// assert_eq!(kstrtobool(c_str!("TRUE")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("FALSE")), Ok(false));
> +/// assert_eq!(kstrtobool(c_str!("YES")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("NO")), Ok(false));
> +/// assert_eq!(kstrtobool(c_str!("ON")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("OFF")), Ok(false));
> +///
> +/// // Numeric
> +/// assert_eq!(kstrtobool(c_str!("1")), Ok(true));
> +/// assert_eq!(kstrtobool(c_str!("0")), Ok(false));
> +///
> +/// // Invalid input
> +/// assert_eq!(kstrtobool(c_str!("invalid")), Err(EINVAL));
> +/// assert_eq!(kstrtobool(c_str!("2")), Err(EINVAL));
> +/// ```
> +pub fn kstrtobool(string: &CStr) -> Result<bool> {
> +    let mut result: bool = false;
> +
> +    // SAFETY: `string` is a valid null-terminated C string, and `result` is a valid
> +    // pointer to a bool that we own.
> +    let ret = unsafe { bindings::kstrtobool(string.as_char_ptr(), &mut result) };
> +
> +    kernel::error::to_result(ret).map(|()| result)
> +}
> +
> /// An owned string that is guaranteed to have exactly one `NUL` byte, which is at the end.
> ///
> /// Used for interoperability with kernel APIs that take C strings.
> 
> -- 
> 2.47.2
> 
> 
> 

Reviewed-by: Daniel Almeida <daniel.almeida@...labora.com>