Re: [PATCH v12 2/3] rust: add parameter support to the `module!` macro

Benno Lossin
2025-06-12T07:52:36Z

On Wed Jun 11, 2025 at 12:31 PM CEST, Andreas Hindborg wrote:
> "Benno Lossin" <lossin@kernel.org> writes:
>> On Tue May 6, 2025 at 3:02 PM CEST, Andreas Hindborg wrote:
>>> diff --git a/rust/macros/helpers.rs b/rust/macros/helpers.rs
>>> index a3ee27e29a6f..16d300ad3d3b 100644
>>> --- a/rust/macros/helpers.rs
>>> +++ b/rust/macros/helpers.rs
>>> @@ -10,6 +10,17 @@ pub(crate) fn try_ident(it: &mut token_stream::IntoIter) -> Option<String> {
>>> }
>>> }
>>>
>>> +pub(crate) fn try_sign(it: &mut token_stream::IntoIter) -> Option<char> {
>>> + let peek = it.clone().next();
>>> + match peek {
>>> + Some(TokenTree::Punct(punct)) if punct.as_char() == '-' => {
>>
>> Should we also allow a leading `+`?
>
> I would argue no, because rust literals cannot start with `+`.

Makes sense.

>>> + let _ = it.next();
>>> + Some(punct.as_char())
>>> + }
>>> + _ => None,
>>> + }
>>> +}
>>> +
>>> pub(crate) fn try_literal(it: &mut token_stream::IntoIter) -> Option<String> {
>>> if let Some(TokenTree::Literal(literal)) = it.next() {
>>> Some(literal.to_string())
>>> @@ -86,3 +97,17 @@ pub(crate) fn function_name(input: TokenStream) -> Option<Ident> {
>>> }
>>> None
>>> }
>>> +
>>> +/// Parse a token stream of the form `expected_name: "value",` and return the
>>> +/// string in the position of "value".
>>> +///
>>> +/// # Panics
>>> +///
>>> +/// - On parse error.
>>> +pub(crate) fn expect_string_field(it: &mut token_stream::IntoIter, expected_name: &str) -> String {
>>> + assert_eq!(expect_ident(it), expected_name);
>>> + assert_eq!(expect_punct(it), ':');
>>> + let string = expect_string(it);
>>> + assert_eq!(expect_punct(it), ',');
>>
>> This won't allow omitting the trailing comma.
>
> This is in line with the rest of the module macro.

Then we should change that:

https://github.com/Rust-for-Linux/linux/issues/1172

>>> + string
>>> +}
>>
>> [...]
>>
>>> @@ -186,33 +336,35 @@ pub(crate) fn module(ts: TokenStream) -> TokenStream {
>>> let info = ModuleInfo::parse(&mut it);
>>>
>>> let mut modinfo = ModInfoBuilder::new(info.name.as_ref());
>>> - if let Some(author) = info.author {
>>> - modinfo.emit("author", &author);
>>> + if let Some(author) = &info.author {
>>> + modinfo.emit("author", author);
>>> }
>>> - if let Some(authors) = info.authors {
>>> + if let Some(authors) = &info.authors {
>>> for author in authors {
>>> - modinfo.emit("author", &author);
>>> + modinfo.emit("author", author);
>>> }
>>> }
>>> - if let Some(description) = info.description {
>>> - modinfo.emit("description", &description);
>>> + if let Some(description) = &info.description {
>>> + modinfo.emit("description", description);
>>> }
>>> modinfo.emit("license", &info.license);
>>> - if let Some(aliases) = info.alias {
>>> + if let Some(aliases) = &info.alias {
>>> for alias in aliases {
>>> - modinfo.emit("alias", &alias);
>>> + modinfo.emit("alias", alias);
>>> }
>>> }
>>> - if let Some(firmware) = info.firmware {
>>> + if let Some(firmware) = &info.firmware {
>>> for fw in firmware {
>>> - modinfo.emit("firmware", &fw);
>>> + modinfo.emit("firmware", fw);
>>
>> I don't like that you have to change all of these.
>
> Why not? If I was to write this code in the first place, I would have
> used a reference rather than pass by value.

That's fine, but do it in a separate commit then.

>> Can't you just take a
>> `&[Parameter]` argument in `emit_params` instead of the whole
>> `ModuleInfo` struct?
>
> I don't think that is a nice solution. I would have to pass the name
> field as well, increasing the number of parameters to the function.

Ah right makes sense.

---
Cheers,
Benno