Re: [PATCH 10/79] block: rust: add `command` getter to `Request`

[Andreas Hindborg]

Alice Ryhl <aliceryhl@xxxxxxxxxx> writes:

> On Mon, Feb 16, 2026 at 12:34:57AM +0100, Andreas Hindborg wrote:
>> 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@xxxxxxxxxx>
>
> With the nit below fixed:
> Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx>
>
>>  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) }
>
> Nit: scope of unsafe
>
> 	unsafe { (*self.0.get()).cmd_flags } & ((1 << bindings::REQ_OP_BITS) - 1)

The `&` is parsed as reference operator with this change. But we can do
this:

        use core::ops::BitAnd;
        // SAFETY: By C API contract and type invariant, `cmd_flags` is valid for read
        unsafe { (*self.0.get()).cmd_flags }.bitand((1u32 << bindings::REQ_OP_BITS) - 1)

Best regards,
Andreas Hindborg