rust: id_pool: add contiguous ID reservation

Add `IdPool::reserve_ids` which allocates a contiguous range with the
given offset, count, and alignment.

Reviewed-by: Burak Emir <burak.emir@gmail.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Eliot Courtney <ecourtney@nvidia.com>
Reviewed-by: Yury Norov <ynorov@nvidia.com>
Link: https://patch.msgid.link/20260930-chid-v9-7-0d6cca376cff@nvidia.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 32 insertions, 0 deletions

diff --git a/rust/kernel/id_pool.rs b/rust/kernel/id_pool.rs
index 384753fe0e44..06a4c71c4c6c 100644
--- a/rust/kernel/id_pool.rs
+++ b/rust/kernel/id_pool.rs
@@ -4,8 +4,14 @@
 
 //! Rust API for an ID pool backed by a [`BitmapVec`].
 
+use core::{
+    num::NonZero,
+    ops::Range, //
+};
+
 use crate::alloc::{AllocError, Flags};
 use crate::bitmap::BitmapVec;
+use crate::ptr::Alignment;
 
 /// Represents a dynamic ID pool backed by a [`BitmapVec`].
 ///
@@ -240,6 +246,32 @@ impl IdPool {
     pub fn release_id(&mut self, id: usize) {
         self.map.clear_bit(id);
     }
+
+    /// Reserves a contiguous area of `count` IDs at or after `offset`.
+    ///
+    /// The start of the returned area is a multiple of `align`.
+    ///
+    /// Returns the reserved range upon success, or [`None`] if no such area could be found.
+    #[inline]
+    #[must_use]
+    pub fn reserve_ids(
+        &mut self,
+        offset: usize,
+        count: NonZero<usize>,
+        align: Alignment,
+    ) -> Option<Range<usize>> {
+        let start = self.map.next_zero_area(offset, count, align)?;
+        self.map.set(start, count);
+        Some(start..start + count.get())
+    }
+
+    /// Releases a contiguous area of IDs.
+    #[inline]
+    pub fn release_ids(&mut self, range: &Range<usize>) {
+        if let Some(nbits) = NonZero::new(range.len()) {
+            self.map.clear(range.start, nbits);
+        }
+    }
 }
 
 /// Represents an unused id in an [`IdPool`].