From 3d5bef5d47c371e17041cd6c84e9c08e54ea9e63 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 13 Apr 2025 02:56:50 +0200 Subject: rust: add C FFI types to the prelude Rust kernel code is supposed to use the custom mapping of C FFI types, i.e. those from the `ffi` crate, rather than the ones coming from `core`. Thus, to minimize mistakes and to simplify the code everywhere, just provide them in the `kernel` prelude and ask in the Coding Guidelines to use them directly, i.e. as a single segment path. After this lands, we can start cleaning up the existing users. Ideally, we would use something like Clippy's `disallowed-types` to prevent the use of the `core` ones, but that one sees through aliases. Link: https://lore.kernel.org/rust-for-linux/CANiq72kc4gzfieD-FjuWfELRDXXD2vLgPv4wqk3nt4pjdPQ=qg@mail.gmail.com/ Reviewed-by: Danilo Krummrich Reviewed-by: Alice Ryhl Link: https://lore.kernel.org/r/20250413005650.1745894-1-ojeda@kernel.org [ Reworded content of the documentation to focus on how to use the aliases first. - Miguel ] Signed-off-by: Miguel Ojeda --- Documentation/rust/coding-guidelines.rst | 17 +++++++++++++++++ rust/kernel/prelude.rs | 5 +++++ 2 files changed, 22 insertions(+) diff --git a/Documentation/rust/coding-guidelines.rst b/Documentation/rust/coding-guidelines.rst index 6c6c51b4cf46..6ff9e754755d 100644 --- a/Documentation/rust/coding-guidelines.rst +++ b/Documentation/rust/coding-guidelines.rst @@ -203,6 +203,23 @@ or: /// [`struct mutex`]: srctree/include/linux/mutex.h +C FFI types +----------- + +Rust kernel code refers to C types, such as ``int``, using type aliases such as +``c_int``, which are readily available from the ``kernel`` prelude. Please do +not use the aliases from ``core::ffi`` -- they may not map to the correct types. + +These aliases should generally be referred directly by their identifier, i.e. +as a single segment path. For instance: + +.. code-block:: rust + + fn f(p: *const c_char) -> c_int { + // ... + } + + Naming ------ diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs index baa774a351ce..f869b02f1f25 100644 --- a/rust/kernel/prelude.rs +++ b/rust/kernel/prelude.rs @@ -14,6 +14,11 @@ #[doc(no_inline)] pub use core::pin::Pin; +pub use ::ffi::{ + c_char, c_int, c_long, c_longlong, c_schar, c_short, c_uchar, c_uint, c_ulong, c_ulonglong, + c_ushort, c_void, +}; + pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, VBox, VVec, Vec}; #[doc(no_inline)] -- cgit v1.2.3