Messages in this thread |  | | Date | Wed, 18 Mar 2026 09:10:03 +0000 | | Subject | Re: [PATCH v13 1/1] rust: interop: Add list module for C linked list interface | | From | Alice Ryhl <> |
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On Tue, Mar 17, 2026 at 04:17:10PM -0400, Joel Fernandes wrote: > Add a new module `kernel::interop::list` for working with C's doubly > circular linked lists. Provide low-level iteration over list nodes. > > Typed iteration over actual items is provided with a `clist_create` > macro to assist in creation of the `CList` type. > > Cc: Nikola Djukic <ndjukic@nvidia.com> > Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com> > Reviewed-by: Alexandre Courbot <acourbot@nvidia.com> > Acked-by: Alexandre Courbot <acourbot@nvidia.com> > Acked-by: Gary Guo <gary@garyguo.net> > Acked-by: Miguel Ojeda <ojeda@kernel.org> > Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>
I have a few nits below. But overall I think this looks ok:
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Please do consider my mod.rs suggestion too, though.
> +//! ``` > +//! use kernel::{ > +//! bindings, > +//! clist_create,
IMO the automatic re-exports of macros at the root shouldn't be used. Import it from kernel::interop::list::clist_create instead.
Note that you need to put a re-export below macro definition to do this.
macro_rules! clist_create { (unsafe { $head:ident, $rust_type:ty, $c_type:ty, $($field:tt).+ }) => {{ // Compile-time check that field path is a `list_head`. // SAFETY: `p` is a valid pointer to `$c_type`. let _: fn(*const $c_type) -> *const $crate::bindings::list_head = |p| unsafe { &raw const (*p).$($field).+ }; // Calculate offset and create `CList`. const OFFSET: usize = ::core::mem::offset_of!($c_type, $($field).+); // SAFETY: The caller of this macro is responsible for ensuring safety. unsafe { $crate::interop::list::CList::<$rust_type, OFFSET>::from_raw($head) } }}; } pub use clist_create; // <-- you need this
See tracepoint.rs or any of the other macros for an example.
> +//! // Create typed [`CList`] from sentinel head. > +//! // SAFETY: `head` is valid and initialized, items are `SampleItemC` with > +//! // embedded `link` field, and `Item` is `#[repr(transparent)]` over `SampleItemC`. > +//! let list = clist_create!(unsafe { head, Item, SampleItemC, link });
Did you try using this in your real use-case? You require `head` to be an :ident, but I think for any 'struct list_head' not stored on the stack, accepting an :expr would be easier to use so that you can just pass `&raw mut my_c_struct.the_list_head` directly to the macro. Right now you have to put the raw pointer in a local variable first.
Alice
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