Re: [PATCH] rust: module_param: return copy from value() for Copy types

[Andreas Hindborg <a.hindborg@kernel.org>]

"Gary Guo" <gary@garyguo.net> writes:

> On Mon Mar 23, 2026 at 12:47 PM GMT, Andreas Hindborg wrote:
>> Rename the existing `value()` method to `value_ref()` which returns a
>> shared reference to the parameter value, and add a new `value()`
>> method on `ModuleParamAccess<T>` where `T: Copy` that returns the
>> value by copy.
>>
>> This provides a more ergonomic API for the common case where the
>> parameter type implements `Copy`, avoiding the need to explicitly
>> dereference the return value at call sites.
>>
>> Currently `value_ref()` has no in-tree callers, but it will be needed
>> when support for non-`Copy` parameter types such as arrays and
>> strings is added.
>>
>> Signed-off-by: Andreas Hindborg <a.hindborg@kernel.org>
>> ---
>> This change was suggested at [1].
>>
>> Link: https://lore.kernel.org/r/87cy13swpw.fsf@t14s.mail-host-address-is-not-set [1]
>> ---
>>  rust/kernel/module_param.rs  | 11 ++++++++++-
>>  samples/rust/rust_minimal.rs |  2 +-
>>  2 files changed, 11 insertions(+), 2 deletions(-)
>>
>> diff --git a/rust/kernel/module_param.rs b/rust/kernel/module_param.rs
>> index 6a8a7a875643..5dcfe2ba87a1 100644
>> --- a/rust/kernel/module_param.rs
>> +++ b/rust/kernel/module_param.rs
>> @@ -134,7 +134,7 @@ pub const fn new(default: T) -> Self {
>>      /// Get a shared reference to the parameter value.
>>      // Note: When sysfs access to parameters are enabled, we have to pass in a
>>      // held lock guard here.
>> -    pub fn value(&self) -> &T {
>> +    pub fn value_ref(&self) -> &T {
>>          self.value.as_ref().unwrap_or(&self.default)
>>      }
>>
>> @@ -146,6 +146,15 @@ pub const fn as_void_ptr(&self) -> *mut c_void {
>>      }
>>  }
>>
>> +impl<T: Copy> ModuleParamAccess<T> {
>> +    /// Get a copy of the parameter value.
>> +    // Note: When sysfs access to parameters are enabled, we have to pass in a
>> +    // held lock guard here.
>> +    pub fn value(&self) -> T {
>
> It's better to keep this close to `value_ref` in the same impl block. The `T:
> Copy` bound doesn't need to be on the impl block, it can be on the item itself
> with
>
>     pub fn value(&self) -> T where T: Copy

Cool, I'll do that.


Best regards,
Andreas Hindborg