Re: [PATCH v4 3/4] rust: configfs: add a sample demonstrating configfs usage

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

"Daniel Almeida" <daniel.almeida@collabora.com> writes:

> Hi Andreas,
>
>> On 24 Feb 2025, at 10:21, Andreas Hindborg <a.hindborg@kernel.org> wrote:
>>
>> Add a sample to the samples folder, demonstrating the intended use of the
>> rust configfs API.
>
> nit: this is not the first time I see Rust not capitalized in this series.

Will fix 👍

[...]

>> +impl kernel::InPlaceModule for RustConfigfs {
>> +    fn init(_module: &'static ThisModule) -> impl PinInit<Self, Error> {
>> +        pr_info!("Rust configfs sample (init)\n");
>> +
>> +        let item_type = configfs_attrs! {
>> +            container: configfs::Subsystem<Configuration>,
>> +            data: Configuration,
>> +            child: Child,
>> +            attributes: [
>> +                message: 0,
>> +                bar: 1,
>> +            ],
>> +        };
>
> As I said in the previous patch, this macro is a bit complex. Is there anything more you can do with it?
>
> If so, it better be in this driver, because I hardly think anybody will go through the source code itself
> to figure out. My 2c.

I can add some inline comments on the usage here. Is that what you are
thinking of?

>
>
>> +
>> +        try_pin_init!(Self {
>> +            config <- configfs::Subsystem::new(
>> +                c_str!("rust_configfs"), item_type, Configuration::new()
>> +            ),
>> +        })
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::GroupOperations for Configuration {
>> +    type Child = Child;
>> +
>> +    fn make_group(&self, name: &CStr) -> Result<impl PinInit<configfs::Group<Child>, Error>> {
>> +        let tpe = configfs_attrs! {
>> +            container: configfs::Group<Child>,
>> +            data: Child,
>> +            child: GrandChild,
>> +            attributes: [
>> +                baz: 0,
>> +            ],
>> +        };
>> +
>> +        Ok(configfs::Group::new(name.try_into()?, tpe, Child::new()))
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::AttributeOperations<0> for Configuration {
>> +    type Data = Configuration;
>> +
>> +    fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
>> +        pr_info!("Show message\n");
>> +        let data = container.message;
>> +        page[0..data.len()].copy_from_slice(data);
>> +        Ok(data.len())
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::AttributeOperations<1> for Configuration {
>> +    type Data = Configuration;
>> +
>> +    fn show(container: &Configuration, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
>> +        pr_info!("Show bar\n");
>> +        let guard = container.bar.lock();
>> +        let data = guard.0.as_slice();
>> +        let len = guard.1;
>> +        page[0..len].copy_from_slice(&data[0..len]);
>> +        Ok(len)
>> +    }
>> +
>> +    fn store(container: &Configuration, page: &[u8]) -> Result {
>> +        pr_info!("Store bar\n");
>> +        let mut guard = container.bar.lock();
>> +        guard.0[0..page.len()].copy_from_slice(page);
>> +        guard.1 = page.len();
>> +        Ok(())
>> +    }
>> +}
>> +
>> +#[pin_data]
>> +struct Child {}
>
> nit: you don’t need the braces here

Can't do that. The `pin_data` macro won't eat it. I'll add a comment.

>
>> +
>> +impl Child {
>> +    fn new() -> impl PinInit<Self, Error> {
>> +        try_pin_init!(Self {})
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::GroupOperations for Child {
>> +    type Child = GrandChild;
>> +
>> +    fn make_group(&self, name: &CStr) -> Result<impl PinInit<configfs::Group<GrandChild>, Error>> {
>> +        let tpe = configfs_attrs! {
>> +            container: configfs::Group<GrandChild>,
>> +            data: GrandChild,
>> +            attributes: [
>> +                gc: 0,
>> +            ],
>> +        };
>> +
>> +        Ok(configfs::Group::new(
>> +            name.try_into()?,
>> +            tpe,
>> +            GrandChild::new(),
>> +        ))
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::AttributeOperations<0> for Child {
>> +    type Data = Child;
>> +
>> +    fn show(_container: &Child, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
>> +        pr_info!("Show baz\n");
>> +        let data = c"Hello Baz\n".to_bytes();
>> +        page[0..data.len()].copy_from_slice(data);
>> +        Ok(data.len())
>> +    }
>> +}
>> +
>> +#[pin_data]
>> +struct GrandChild {}
>
> …nor here

>
>> +
>> +impl GrandChild {
>> +    fn new() -> impl PinInit<Self, Error> {
>> +        try_pin_init!(Self {})
>> +    }
>> +}
>> +
>> +#[vtable]
>> +impl configfs::AttributeOperations<0> for GrandChild {
>> +    type Data = GrandChild;
>> +
>> +    fn show(_container: &GrandChild, page: &mut [u8; PAGE_SIZE]) -> Result<usize> {
>> +        pr_info!("Show baz\n");
>
> As I said in the cover letter, perhaps this one slip through :)

Yes, thank you.

>
>> +        let data = c"Hello GC\n".to_bytes();
>> +        page[0..data.len()].copy_from_slice(data);
>> +        Ok(data.len())
>> +    }
>> +}
>>
>> --
>> 2.47.0
>>
>>
>
> I’m OK with this patch. It works, and it does what it’s supposed to do, i.e.: showcase the API.
>
> With the “Show baz” nit fixed:
>
> Reviewed-by: Daniel Almeida <daniel.almeida@collabora.com>

Thanks!


Best regards,
Andreas Hindborg