Re: [PATCH v4 4/4] rust: add parameter support to the `module!` macro

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

"Petr Pavlu" <petr.pavlu@suse.com> writes:

> On 1/9/25 11:54, Andreas Hindborg wrote:
>> This patch includes changes required for Rust kernel modules to utilize
>> module parameters. This code implements read only support for integer
>> types without `sysfs` support.
>>

[cut]

>> +
>> +        // SAFETY: `old_value` is valid for writes, as we have exclusive
>> +        // access. `old_value` is pointing to an initialized static, an
>
> Typo: an -> and

Thanks.

[cut]

>> +
>> +    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);
>> +
>> +            write!(
>> +                self.param_buffer,
>> +                "
>> +                    pub(crate) static {param_name}:
>> +                        ::kernel::module_param::ModuleParamAccess<{param_type}> =
>> +                            ::kernel::module_param::ModuleParamAccess::new({param_default});
>> +
>> +                    #[link_section = \"__param\"]
>> +                    #[used]
>> +                    static __{module_name}_{param_name}_struct:
>> +                        ::kernel::module_param::RacyKernelParam =
>> +                        ::kernel::module_param::RacyKernelParam(::kernel::bindings::kernel_param {{
>> +                            name: if cfg!(MODULE) {{
>> +                                c\"{module_name}.{param_name}\"
>> +                            }} else {{
>> +                                c\"{param_name}\"
>> +                            }}.as_ptr(),
>
> This should be the other way around? Running
> 'insmod rust_minimal.ko test_parameter=2' reports for me that the
> parameter is unknown while specifying 'rust_minimal.test_parameter=2'
> works. The prefix should be used only if the module is built-in so the
> parameter can be distinguished on the kernel command line.

Thanks for testing! This actually gave me quite a headache when I was
using the series elsewhere. I forgot to resend the series with the fix,
sorry.


Best regards,
Andreas Hindborg