On Fri, Mar 14, 2025 at 3:20 PM Benno Lossin <benno.lossin@xxxxxxxxx> wrote: > > On Fri Mar 7, 2025 at 10:58 PM CET, Tamir Duberstein wrote: > > Implement `HasWork::work_container_of` in `impl_has_work!`, narrowing > > the interface of `HasWork` and replacing pointer arithmetic with > > `container_of!`. Remove the provided implementation of > > `HasWork::get_work_offset` without replacement; an implementation is > > already generated in `impl_has_work!`. Remove the `Self: Sized` bound on > > `HasWork::work_container_of` which was apparently necessary to access > > `OFFSET` as `OFFSET` no longer exists. > > > > A similar API change was discussed on the hrtimer series[1]. > > > > Link: https://lore.kernel.org/all/20250224-hrtimer-v3-v6-12-rc2-v9-1-5bd3bf0ce6cc@xxxxxxxxxx/ [1] > > Signed-off-by: Tamir Duberstein <tamird@xxxxxxxxx> > > --- > > rust/kernel/workqueue.rs | 45 ++++++++++++--------------------------------- > > 1 file changed, 12 insertions(+), 33 deletions(-) > > What is the motivation of this change? I didn't follow the discussion, > so if you explained it there, it would be nice if you could also add it > to this commit message. The motivation is right at the top: it narrows the interface and replaces pointer arithmetic with an existing macro, and then deletes unnecessary code. > > diff --git a/rust/kernel/workqueue.rs b/rust/kernel/workqueue.rs > > index 0cd100d2aefb..0e2e0ecc58a6 100644 > > --- a/rust/kernel/workqueue.rs > > +++ b/rust/kernel/workqueue.rs > > @@ -429,51 +429,23 @@ pub unsafe fn raw_get(ptr: *const Self) -> *mut bindings::work_struct { > > /// > > /// # Safety > > /// > > -/// The [`OFFSET`] constant must be the offset of a field in `Self` of type [`Work<T, ID>`]. The > > -/// methods on this trait must have exactly the behavior that the definitions given below have. > > +/// The methods on this trait must have exactly the behavior that the definitions given below have. > > /// > > /// [`impl_has_work!`]: crate::impl_has_work > > -/// [`OFFSET`]: HasWork::OFFSET > > pub unsafe trait HasWork<T, const ID: u64 = 0> { > > - /// The offset of the [`Work<T, ID>`] field. > > - const OFFSET: usize; > > - > > - /// Returns the offset of the [`Work<T, ID>`] field. > > - /// > > - /// This method exists because the [`OFFSET`] constant cannot be accessed if the type is not > > - /// [`Sized`]. > > - /// > > - /// [`OFFSET`]: HasWork::OFFSET > > - #[inline] > > - fn get_work_offset(&self) -> usize { > > - Self::OFFSET > > - } > > - > > /// Returns a pointer to the [`Work<T, ID>`] field. > > /// > > /// # Safety > > /// > > /// The provided pointer must point at a valid struct of type `Self`. > > - #[inline] > > - unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID> { > > - // SAFETY: The caller promises that the pointer is valid. > > - unsafe { (ptr as *mut u8).add(Self::OFFSET) as *mut Work<T, ID> } > > - } > > + unsafe fn raw_get_work(ptr: *mut Self) -> *mut Work<T, ID>; > > > > /// Returns a pointer to the struct containing the [`Work<T, ID>`] field. > > /// > > /// # Safety > > /// > > /// The pointer must point at a [`Work<T, ID>`] field in a struct of type `Self`. > > - #[inline] > > - unsafe fn work_container_of(ptr: *mut Work<T, ID>) -> *mut Self > > - where > > - Self: Sized, > > This bound is required in order to allow the usage of `dyn HasWork` (ie > object safety), so it should stay. > > Maybe add a comment explaining why it's there. I guess a doctest would be better, but I still don't understand why the bound is needed. Sorry, can you cite something or explain in more detail please?
