Messages in this thread Patch in this message | | | From | Asahi Lina <> | Date | Wed, 29 Mar 2023 21:04:38 +0900 | Subject | [PATCH v2 6/6] rust: error: Add from_result() helper |
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From: Wedson Almeida Filho <wedsonaf@gmail.com>
Add a helper function to easily return C result codes from a Rust function that calls functions which return a Result<T>.
Lina: Imported from rust-for-linux/rust, originally developed by Wedson as part of file_operations.rs. Added the allow() flags since there is no user in the kernel crate yet and fixed a typo in a comment. Replaced the macro with a function taking a closure, per discussion on the ML.
Co-developed-by: Fox Chen <foxhlchen@gmail.com> Signed-off-by: Fox Chen <foxhlchen@gmail.com> Co-developed-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com> Signed-off-by: Asahi Lina <lina@asahilina.net> --- rust/kernel/error.rs | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+)
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs index 6b10129075a7..4d8b19d5967d 100644 --- a/rust/kernel/error.rs +++ b/rust/kernel/error.rs @@ -226,3 +226,42 @@ pub(crate) fn from_err_ptr<T>(ptr: *mut T) -> Result<*mut T> { } Ok(ptr) } + +/// Calls a closure returning a [`crate::error::Result<T>`] and converts the result to +/// a C integer result. +/// +/// This is useful when calling Rust functions that return [`crate::error::Result<T>`] +/// from inside `extern "C"` functions that need to return an integer error result. +/// +/// `T` should be convertible from an `i16` via `From<i16>`. +/// +/// # Examples +/// +/// ```ignore +/// # use kernel::from_result; +/// # use kernel::bindings; +/// unsafe extern "C" fn probe_callback( +/// pdev: *mut bindings::platform_device, +/// ) -> core::ffi::c_int { +/// from_result(|| { +/// let ptr = devm_alloc(pdev)?; +/// bindings::platform_set_drvdata(pdev, ptr); +/// Ok(0) +/// }) +/// } +/// ``` +// TODO: Remove `dead_code` marker once an in-kernel client is available. +#[allow(dead_code)] +pub(crate) fn from_result<T, F>(f: F) -> T +where + T: From<i16>, + F: FnOnce() -> Result<T>, +{ + match f() { + Ok(v) => v, + // NO-OVERFLOW: negative `errno`s are no smaller than `-bindings::MAX_ERRNO`, + // `-bindings::MAX_ERRNO` fits in an `i16` as per invariant above, + // therefore a negative `errno` always fits in an `i16` and will not overflow. + Err(e) => T::from(e.to_errno() as i16), + } +} -- 2.40.0
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