On Fri May 29, 2026 at 9:41 AM BST, Andreas Hindborg wrote:
> For `Copy` parameter types it is more ergonomic to retrieve the
> parameter value by copy than through a shared reference. Change
> `ModuleParamAccess::value` to return `T` by copy when `T: Copy`,
> and rename the previous reference-returning accessor to
> `value_ref`. Update the in-tree caller in `rust_minimal`.
>
> Suggested-by: Alice Ryhl <[email protected]>
> Signed-off-by: Andreas Hindborg <[email protected]>
> ---
> This change was suggested during review of the rust null block series [1].
>
> [1] https://lore.kernel.org/r/[email protected]
> ---
> rust/kernel/module_param.rs | 15 ++++++++++++++-
> samples/rust/rust_minimal.rs | 2 +-
> 2 files changed, 15 insertions(+), 2 deletions(-)
>
> diff --git a/rust/kernel/module_param.rs b/rust/kernel/module_param.rs
> index 6a8a7a875643..701210206bba 100644
> --- a/rust/kernel/module_param.rs
> +++ b/rust/kernel/module_param.rs
> @@ -132,9 +132,12 @@ pub const fn new(default: T) -> Self {
> }
>
> /// Get a shared reference to the parameter value.
> + ///
> + /// Returns a reference to the value supplied at module load time, or a
> + /// reference to the default value if the parameter has not been set.
> // 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 +149,16 @@ pub const fn as_void_ptr(&self) -> *mut c_void {
> }
> }
>
> +impl<T: Copy> ModuleParamAccess<T> {
Instead of adding a new impl block, this should just be moved to immediately
after (or before) `value_ref` with a `where T: Copy` bound instead.
This makes related code close together for readers of the code.
Thanks,
Gary
> + /// Get a copy of the parameter value.
> + ///
> + /// Returns the value supplied at module load time, or the default value
> + /// if the parameter has not been set.
> + pub fn value(&self) -> T {
> + self.value.copy().unwrap_or(self.default)
> + }
> +}
> +
> #[doc(hidden)]
> /// Generate a static
> [`kernel_param_ops`](srctree/include/linux/moduleparam.h) struct.
> ///
> diff --git a/samples/rust/rust_minimal.rs b/samples/rust/rust_minimal.rs
> index 8eb9583571d7..60d03df6cd80 100644
> --- a/samples/rust/rust_minimal.rs
> +++ b/samples/rust/rust_minimal.rs
> @@ -28,7 +28,7 @@ fn init(_module: &'static ThisModule) -> Result<Self> {
> pr_info!("Am I built-in? {}\n", !cfg!(MODULE));
> pr_info!(
> "test_parameter: {}\n",
> - *module_parameters::test_parameter.value()
> + module_parameters::test_parameter.value()
> );
>
> let mut numbers = KVec::new();
>
> ---
> base-commit: 7fd2df204f342fc17d1a0bfcd474b24232fb0f32
> change-id: 20260529-modules-value-ref-e95a7ab94fdb
>
> Best regards,
