Re: [PATCH 1/3] rust: xarray: abstract `xa_alloc`

[Alice Ryhl <aliceryhl@google.com>]

On Mon, Oct 06, 2025 at 09:31:43PM +0200, Benno Lossin wrote:
> On Mon Oct 6, 2025 at 6:30 PM CEST, Onur Özkan wrote:
> > Implements `alloc` function to `XArray<T>` that wraps
> > `xa_alloc` safely.
> >
> > Resolves a task from the nova/core task list under the "XArray
> > bindings [XARR]" section in "Documentation/gpu/nova/core/todo.rst"
> > file.
> >
> > Signed-off-by: Onur Özkan <work@onurozkan.dev>
> > ---
> >  rust/kernel/xarray.rs | 39 +++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 39 insertions(+)
> >
> > diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs
> > index a49d6db28845..1b882cd2f58b 100644
> > --- a/rust/kernel/xarray.rs
> > +++ b/rust/kernel/xarray.rs
> > @@ -266,6 +266,45 @@ pub fn store(
> >              Ok(unsafe { T::try_from_foreign(old) })
> >          }
> >      }
> > +
> > +    /// Allocates an empty slot within the given limit range and stores `value` there.
> > +    ///
> > +    /// May drop the lock if needed to allocate memory, and then reacquire it afterwards.
> > +    ///
> > +    /// On success, returns the allocated id.
> > +    ///
> > +    /// On failure, returns the element which was attempted to be stored.
> > +    pub fn alloc(
> > +        &mut self,
> > +        limit: bindings::xa_limit,
> > +        value: T,
> > +        gfp: alloc::Flags,
> > +    ) -> Result<u32, StoreError<T>> {
> 
> I think it would be a good idea to make the id a newtype wrapper around
> u32. Maybe not even allow users to manually construct it or even inspect
> it if possible.

What? People need to know what the assigned index is.

Alice