rust: bitmap: document panics in `next_bit` and `next_zero_bit`

`next_bit()` and `next_zero_bit()` use `bitmap_assert!()` to check
that `start` is less than `self.len()`, which panics when
`CONFIG_RUST_BITMAP_HARDENED` is enabled. However, neither function
has a `# Panics` section, and both document that `None` is returned
for exactly the input that triggers the panic.

Update the documentation of `next_bit()` and `next_zero_bit()` to add
the missing `# Panics` sections, add the missing blank doc comment line
before `Returns` in `next_zero_bit()`, and simplify the wording.

Fixes: 11eca92a2cae ("rust: add bitmap API.")
Closes: https://github.com/Rust-for-Linux/linux/issues/1252
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Signed-off-by: Georgios Androutsopoulos <georgeandrout13@gmail.com>
Signed-off-by: Yury Norov <ynorov@nvidia.com>

1 files changed, 15 insertions, 2 deletions

diff --git a/rust/kernel/bitmap.rs b/rust/kernel/bitmap.rs
index b27e0ec80d64..b51c8a96f1a8 100644
--- a/rust/kernel/bitmap.rs
+++ b/rust/kernel/bitmap.rs
@@ -459,7 +459,13 @@ impl Bitmap {
 
     /// Finds next set bit, starting from `start`.
     ///
-    /// Returns `None` if `start` is greater or equal to `self.nbits`.
+    /// Returns `None` if no bits are set on or after the given index. The
+    /// index `start` must be in bounds.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `CONFIG_RUST_BITMAP_HARDENED` is enabled and `start` is
+    /// out of bounds.
     #[inline]
     pub fn next_bit(&self, start: usize) -> Option<usize> {
         bitmap_assert!(
@@ -479,7 +485,14 @@ impl Bitmap {
     }
 
     /// Finds next zero bit, starting from `start`.
-    /// Returns `None` if `start` is greater than or equal to `self.len()`.
+    ///
+    /// Returns `None` if no bits are zero on or after the given index. The
+    /// index `start` must be in bounds.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `CONFIG_RUST_BITMAP_HARDENED` is enabled and `start` is
+    /// out of bounds.
     #[inline]
     pub fn next_zero_bit(&self, start: usize) -> Option<usize> {
         bitmap_assert!(