On Wed, Aug 13, 2025 at 7:36 PM Andreas Hindborg <a.hindborg@xxxxxxxxxx> wrote:
>
> "Alice Ryhl" <aliceryhl@xxxxxxxxxx> writes:
>
> > For your convenience, I already wrote a safe wrapper of kstrtobool for
> > an out-of-tree driver. You're welcome to copy-paste this:
> >
> > fn kstrtobool(kstr: &CStr) -> Result<bool> {
> > let mut res = false;
> > to_result(unsafe {
> > kernel::bindings::kstrtobool(kstr.as_char_ptr(), &mut res) })?;
> > Ok(res)
> > }
>
> Thanks, I did one as well today, accepting `&str` instead. The examples
> highlight why it is not great:
Yeah, well, I think we should still use it for consistency.
> /// 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::str::kstrtobool;
> ///
> /// // Lowercase
> /// assert_eq!(kstrtobool("true"), Ok(true));
> /// assert_eq!(kstrtobool("tr"), Ok(true));
> /// assert_eq!(kstrtobool("t"), Ok(true));
> /// assert_eq!(kstrtobool("twrong"), Ok(true)); // <-- 🤷
> /// assert_eq!(kstrtobool("false"), Ok(false));
> /// assert_eq!(kstrtobool("f"), Ok(false));
> /// assert_eq!(kstrtobool("yes"), Ok(true));
> /// assert_eq!(kstrtobool("no"), Ok(false));
> /// assert_eq!(kstrtobool("on"), Ok(true));
> /// assert_eq!(kstrtobool("off"), Ok(false));
> ///
> /// // Camel case
> /// assert_eq!(kstrtobool("True"), Ok(true));
> /// assert_eq!(kstrtobool("False"), Ok(false));
> /// assert_eq!(kstrtobool("Yes"), Ok(true));
> /// assert_eq!(kstrtobool("No"), Ok(false));
> /// assert_eq!(kstrtobool("On"), Ok(true));
> /// assert_eq!(kstrtobool("Off"), Ok(false));
> ///
> /// // All caps
> /// assert_eq!(kstrtobool("TRUE"), Ok(true));
> /// assert_eq!(kstrtobool("FALSE"), Ok(false));
> /// assert_eq!(kstrtobool("YES"), Ok(true));
> /// assert_eq!(kstrtobool("NO"), Ok(false));
> /// assert_eq!(kstrtobool("ON"), Ok(true));
> /// assert_eq!(kstrtobool("OFF"), Ok(false));
> ///
> /// // Numeric
> /// assert_eq!(kstrtobool("1"), Ok(true));
> /// assert_eq!(kstrtobool("0"), Ok(false));
> ///
> /// // Invalid input
> /// assert_eq!(kstrtobool("invalid"), Err(EINVAL));
> /// assert_eq!(kstrtobool("2"), Err(EINVAL));
> /// ```
> pub fn kstrtobool(input: &str) -> Result<bool> {
> let mut result: bool = false;
> let c_str = CString::try_from_fmt(fmt!("{input}"))?;
>
> // SAFETY: `c_str` points to a valid null-terminated C string, and `result` is a valid
> // pointer to a bool that we own.
> let ret = unsafe { bindings::kstrtobool(c_str.as_char_ptr(), &mut result as *mut bool) };
>
> kernel::error::to_result(ret).map(|_| result)
> }
>
> Not sure if we should take `CStr` or `str`, what do you think?
Using CStr makes sense, since it avoids having the caller perform a
useless utf-8 check.
Alice
