Re: [PATCH v13 4/6] rust: module: update the module macro with module parameter support

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

"Benno Lossin" <lossin@kernel.org> writes:

> On Thu Jun 12, 2025 at 3:40 PM CEST, Andreas Hindborg wrote:
>> +
>> +    fn emit_params(&mut self, info: &ModuleInfo) {
>> +        let Some(params) = &info.params else {
>> +            return;
>> +        };
>> +
>> +        for param in params {
>> +            let ops = param_ops_path(&param.ptype);
>> +
>> +            // Note: The spelling of these fields is dictated by the user space
>> +            // tool `modinfo`.
>> +            self.emit_param("parmtype", &param.name, &param.ptype);
>> +            self.emit_param("parm", &param.name, &param.description);
>
> I just read this part again and I want to voice my dissatisfaction with
> these key names. (not that you can do anything about that :)
>
>> +
>> +            write!(
>> +                self.param_buffer,
>> +                "
>> +                    pub(crate) static {param_name}:
>
> Does this need to be accessed by anything else except the static below?
> If no, then can we move it inside of that static? So
>
>     #[link_section = \"__param\"]
>     #[used]
>     static __{module_name}_{param_name}_struct: ::kernel::module_param::RacyKernelParam = {
>         static {param_name}:
>             ::kernel::module_param::ModuleParamAccess<{param_type}> =
>                 ::kernel::module_param::ModuleParamAccess::new({param_default});
>         // ...
>     };

It is used to access the value of the parameter from the module. If you
reduce visibility you will get an error when trying to read the
parameter value:

    RUSTC     samples/rust/rust_minimal.o
  error[E0425]: cannot find value `test_parameter` in module `module_parameters`
    --> /home/aeh/src/linux-rust/module-params/samples/rust/rust_minimal.rs:31:33
    |
  31 |             *module_parameters::test_parameter.get()
    |                                 ^^^^^^^^^^^^^^ not found in `module_parameters`

  error: aborting due to 1 previous error


Best regards,
Andreas Hindborg