Re: [PATCH v1] rust: Add pr_*_once macros

[Dirk Behme <dirk.behme@gmail.com>]

On 03.11.24 04:05, FUJITA Tomonori wrote:
> Add Rust version of pr_[emerg|alert|crit|err|warn|notic|info]_once
> functions, which print a message only once.

Maybe it should be mentioned why this is added? Who will use this?

> Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
> ---
>  rust/kernel/print.rs | 92 ++++++++++++++++++++++++++++++++++++++++++++
>  1 file changed, 92 insertions(+)
> 
> diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
> index a28077a7cb30..57dbb45ba5c0 100644
> --- a/rust/kernel/print.rs
> +++ b/rust/kernel/print.rs
> @@ -414,3 +414,95 @@ macro_rules! pr_cont (
>          $crate::print_macro!($crate::print::format_strings::CONT, true, $($arg)*)
>      )
>  );
> +
> +/// Executes code only once if the condition is true.
> +///
> +/// Public but hidden since it should only be used from public macros.
> +#[doc(hidden)]
> +#[macro_export]
> +macro_rules! do_once_lite_if (
> +    ($condition:expr, $e:expr) => (
> +        {
> +            #[link_section = ".data.once"]
> +            static ALREADY_DONE: core::sync::atomic::AtomicBool =
> +                core::sync::atomic::AtomicBool::new(false);
> +            let mut ret = false;
> +
> +            if $condition && !ALREADY_DONE.swap(true, core::sync::atomic::Ordering::Relaxed) {

What is '$condition'  good for? It looks to me that it is set just to
'true' everywhere below? Could it be dropped?

> +                $e;
> +                ret = true;
> +            }
> +            ret
> +        }
> +    )
> +);
> +
> +/// Prints an emergency-level message (level 0) only once.
> +///
> +/// Equivalent to the kernel's [`pr_emerg_once`] macro.

Here and below:

Would it make sense to use a similar header style like with the
existing pr_*()? And add '# Examples'?

Best regards

Dirk


> +#[macro_export]
> +macro_rules! pr_emerg_once (
> +    ($($arg:tt)*) => (
> +        $crate::do_once_lite_if!(true, $crate::pr_emerg!($($arg)*))
> +    )
> +);
> +
> +/// Prints an alert-level message (level 1) only once.
> +///
> +/// Equivalent to the kernel's [`pr_alert_once`] macro.
> +#[macro_export]
> +macro_rules! pr_alert_once (
> +    ($($arg:tt)*) => (
> +        $crate::do_once_lite_if!(true, $crate::pr_alert!($($arg)*))
> +    )
> +);
> +
> +/// Prints a critical-level message (level 2) only once.
> +///
> +/// Equivalent to the kernel's [`pr_crit_once`] macro.
> +#[macro_export]
> +macro_rules! pr_crit_once (
> +    ($($arg:tt)*) => (
> +        $crate::do_once_lite_if!(true, $crate::pr_crit!($($arg)*))
> +    )
> +);
> +
> +/// Prints an error-level message (level 3) only once.
> +///
> +/// Equivalent to the kernel's [`pr_err_once`] macro.
> +#[macro_export]
> +macro_rules! pr_err_once (
> +    ($($arg:tt)*) => (
> +        $crate::do_once_lite_if!(true, $crate::pr_err!($($arg)*))
> +    )
> +);
> +
> +/// Prints a warning-level message (level 4) only once.
> +///
> +/// Equivalent to the kernel's [`pr_warn_once`] macro.
> +#[macro_export]
> +macro_rules! pr_warn_once (
> +    ($($arg:tt)*) => (
> +        $crate::do_once_lite_if!(true, $crate::pr_warn!($($arg)*))
> +    )
> +);
> +
> +/// Prints a notice-level message (level 5) only once.
> +///
> +/// Equivalent to the kernel's [`pr_notice_once`] macro.
> +#[macro_export]
> +macro_rules! pr_notice_once (
> +    ($($arg:tt)*) => (
> +        $crate::do_once_lite_if!(true, $crate::pr_notice!($($arg)*))
> +    )
> +);
> +
> +/// Prints an info-level message (level 6) only once.
> +///
> +/// Equivalent to the kernel's [`pr_info_once`] macro.
> +#[macro_export]
> +macro_rules! pr_info_once (
> +    ($($arg:tt)*) => (
> +        $crate::do_once_lite_if!(true, $crate::pr_info!($($arg)*))
> +    )
> +);
> 
> base-commit: ae7851c29747fa3765ecb722fe722117a346f988