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Diffstat (limited to 'rust/kernel/error.rs')
-rw-r--r-- | rust/kernel/error.rs | 59 |
1 files changed, 59 insertions, 0 deletions
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs new file mode 100644 index 000000000000..466b2a8fe569 --- /dev/null +++ b/rust/kernel/error.rs @@ -0,0 +1,59 @@ +// SPDX-License-Identifier: GPL-2.0 + +//! Kernel errors. +//! +//! C header: [`include/uapi/asm-generic/errno-base.h`](../../../include/uapi/asm-generic/errno-base.h) + +use alloc::collections::TryReserveError; + +/// Contains the C-compatible error codes. +pub mod code { + /// Out of memory. + pub const ENOMEM: super::Error = super::Error(-(crate::bindings::ENOMEM as i32)); +} + +/// Generic integer kernel error. +/// +/// The kernel defines a set of integer generic error codes based on C and +/// POSIX ones. These codes may have a more specific meaning in some contexts. +/// +/// # Invariants +/// +/// The value is a valid `errno` (i.e. `>= -MAX_ERRNO && < 0`). +#[derive(Clone, Copy, PartialEq, Eq)] +pub struct Error(core::ffi::c_int); + +impl Error { + /// Returns the kernel error code. + pub fn to_kernel_errno(self) -> core::ffi::c_int { + self.0 + } +} + +impl From<TryReserveError> for Error { + fn from(_: TryReserveError) -> Error { + code::ENOMEM + } +} + +/// A [`Result`] with an [`Error`] error type. +/// +/// To be used as the return type for functions that may fail. +/// +/// # Error codes in C and Rust +/// +/// In C, it is common that functions indicate success or failure through +/// their return value; modifying or returning extra data through non-`const` +/// pointer parameters. In particular, in the kernel, functions that may fail +/// typically return an `int` that represents a generic error code. We model +/// those as [`Error`]. +/// +/// In Rust, it is idiomatic to model functions that may fail as returning +/// a [`Result`]. Since in the kernel many functions return an error code, +/// [`Result`] is a type alias for a [`core::result::Result`] that uses +/// [`Error`] as its error type. +/// +/// Note that even if a function does not return anything when it succeeds, +/// it should still be modeled as returning a `Result` rather than +/// just an [`Error`]. +pub type Result<T = ()> = core::result::Result<T, Error>; |