Add a method to extract the command operation code from a request. The
command is obtained by masking the lower bits of `cmd_flags` as defined by
`REQ_OP_BITS`. This allows Rust block drivers to determine the type of
operation being requested.

Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
---
 rust/kernel/block/mq/request.rs | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/rust/kernel/block/mq/request.rs b/rust/kernel/block/mq/request.rs
index b49197a0c66d7..0dd329ae93dfc 100644
--- a/rust/kernel/block/mq/request.rs
+++ b/rust/kernel/block/mq/request.rs
@@ -78,6 +78,12 @@ pub(crate) unsafe fn aref_from_raw(ptr: *mut bindings::request) -> ARef<Self> {
         unsafe { ARef::from_raw(NonNull::new_unchecked(ptr.cast())) }
     }
 
+    /// Get the command identifier for the request
+    pub fn command(&self) -> u32 {
+        // SAFETY: By C API contract and type invariant, `cmd_flags` is valid for read
+        unsafe { (*self.0.get()).cmd_flags & ((1 << bindings::REQ_OP_BITS) - 1) }
+    }
+
     /// Complete the request by scheduling `Operations::complete` for
     /// execution.
     ///

-- 
2.51.2