Re: [PATCH v2 2/4] rust: xarray: abstract `xa_alloc`

[Alice Ryhl <aliceryhl@google.com>]

On Wed, Oct 08, 2025 at 03:46:17PM +0300, Onur Özkan wrote:
> Implements `alloc` function to `XArray<T>` that wraps
> `xa_alloc` safely, which will be used to generate the
> auxiliary device IDs.
> 
> 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 | 41 ++++++++++++++++++++++++++++++++++++++++-
>  1 file changed, 40 insertions(+), 1 deletion(-)
> 
> diff --git a/rust/kernel/xarray.rs b/rust/kernel/xarray.rs
> index 90e27cd5197e..0711ccf99fb4 100644
> --- a/rust/kernel/xarray.rs
> +++ b/rust/kernel/xarray.rs
> @@ -10,7 +10,7 @@
>      ffi::c_void,
>      types::{ForeignOwnable, NotThreadSafe, Opaque},
>  };
> -use core::{iter, marker::PhantomData, pin::Pin, ptr::NonNull};
> +use core::{iter, marker::PhantomData, ops::Range, pin::Pin, ptr::NonNull};
>  use pin_init::{pin_data, pin_init, pinned_drop, PinInit};
> 
>  /// An array which efficiently maps sparse integer indices to owned objects.
> @@ -268,6 +268,45 @@ pub fn store(
>              Ok(unsafe { T::try_from_foreign(old) })
>          }
>      }
> +
> +    /// Allocates an empty slot within the given `limit` and stores `value` there.
> +    ///
> +    /// May drop the lock if needed to allocate memory, and then reacquire it afterwards.
> +    ///
> +    /// On success, returns the allocated index.
> +    ///
> +    /// On failure, returns the element which was attempted to be stored.
> +    pub fn alloc(
> +        &mut self,
> +        limit: Range<u32>,

The Range type is inclusive/exclusive but xa_limit is
inclusive/inclusive. They should match to avoid confusion.

Alice