Macro configfs_attrs

macro_rules! configfs_attrs {
    (
        container: $container:ty,
        data: $data:ty,
        attributes: [
            $($name:ident: $attr:literal),* $(,)?
        ] $(,)?
    ) => { ... };
    (
        container: $container:ty,
        data: $data:ty,
        child: $child:ty,
        attributes: [
            $($name:ident: $attr:literal),* $(,)?
        ] $(,)?
    ) => { ... };
    (count:
     @container($container:ty),
     @data($data:ty),
     @child($($child:ty)?),
     @no_child($($no_child:ident)?),
     @attrs($($aname:ident $aattr:literal)*),
     @eat($name:ident $attr:literal, $($rname:ident $rattr:literal,)*),
     @assign($($assign:block)*),
     @cnt($cnt:expr),
    ) => { ... };
    (count:
     @container($container:ty),
     @data($data:ty),
     @child($($child:ty)?),
     @no_child($($no_child:ident)?),
     @attrs($($aname:ident $aattr:literal)*),
     @eat(),
     @assign($($assign:block)*),
     @cnt($cnt:expr),
    ) => { ... };
    (final:
     @container($container:ty),
     @data($data:ty),
     @child($($child:ty)?),
     @no_child($($no_child:ident)?),
     @attrs($($name:ident $attr:literal)*),
     @assign($($assign:block)*),
     @cnt($cnt:expr),
    ) => { ... };
}

Define a list of configfs attributes statically.

Invoking the macro in the following manner:

let item_type = configfs_attrs! {
    container: configfs::Subsystem<Configuration>,
    data: Configuration,
    child: Child,
    attributes: [
        message: 0,
        bar: 1,
    ],
};

Expands the following output:

let item_type = {
    static CONFIGURATION_MESSAGE_ATTR: kernel::configfs::Attribute<
        0,
        Configuration,
        Configuration,
    > = unsafe {
        kernel::configfs::Attribute::new({
            const S: &str = "message\u{0}";
            const C: &kernel::str::CStr = match kernel::str::CStr::from_bytes_with_nul(
                S.as_bytes()
            ) {
                Ok(v) => v,
                Err(_) => {
                    core::panicking::panic_fmt(core::const_format_args!(
                        "string contains interior NUL"
                    ));
                }
            };
            C
        })
    };

    static CONFIGURATION_BAR_ATTR: kernel::configfs::Attribute<
            1,
            Configuration,
            Configuration
    > = unsafe {
        kernel::configfs::Attribute::new({
            const S: &str = "bar\u{0}";
            const C: &kernel::str::CStr = match kernel::str::CStr::from_bytes_with_nul(
                S.as_bytes()
            ) {
                Ok(v) => v,
                Err(_) => {
                    core::panicking::panic_fmt(core::const_format_args!(
                        "string contains interior NUL"
                    ));
                }
            };
            C
        })
    };

    const N: usize = (1usize + (1usize + 0usize)) + 1usize;

    static CONFIGURATION_ATTRS: kernel::configfs::AttributeList<N, Configuration> =
        unsafe { kernel::configfs::AttributeList::new() };

    {
        const N: usize = 0usize;
        unsafe { CONFIGURATION_ATTRS.add::<N, 0, _>(&CONFIGURATION_MESSAGE_ATTR) };
    }

    {
        const N: usize = (1usize + 0usize);
        unsafe { CONFIGURATION_ATTRS.add::<N, 1, _>(&CONFIGURATION_BAR_ATTR) };
    }

    static CONFIGURATION_TPE:
      kernel::configfs::ItemType<configfs::Subsystem<Configuration> ,Configuration>
        = kernel::configfs::ItemType::<
                configfs::Subsystem<Configuration>,
                Configuration
                >::new_with_child_ctor::<N,Child>(
            &THIS_MODULE,
            &CONFIGURATION_ATTRS
        );

    &CONFIGURATION_TPE
}