linux-kernel - Re: [PATCH] rust: add this

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Message-ID: <Y9kasJQZf146ekp+@kroah.com>
Date:   Tue, 31 Jan 2023 14:42:08 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Martin Rodriguez Reboredo <yakoyoku@...il.com>
Cc:     linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
        Miguel Ojeda <ojeda@...nel.org>,
        Alex Gaynor <alex.gaynor@...il.com>,
        Wedson Almeida Filho <wedsonaf@...il.com>,
        Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
        Björn Roy Baron <bjorn3_gh@...tonmail.com>
Subject: Re: [PATCH] rust: add this_module macro

On Tue, Jan 31, 2023 at 10:08:41AM -0300, Martin Rodriguez Reboredo wrote:
> Adds a Rust equivalent to the handy THIS_MODULE macro from C.
> 
> Signed-off-by: Martin Rodriguez Reboredo <yakoyoku@...il.com>
> ---
>  rust/kernel/lib.rs | 12 ++++++++++++
>  1 file changed, 12 insertions(+)
> 
> diff --git a/rust/kernel/lib.rs b/rust/kernel/lib.rs
> index e0b0e953907d..afb6b0390426 100644
> --- a/rust/kernel/lib.rs
> +++ b/rust/kernel/lib.rs
> @@ -80,6 +80,18 @@ impl ThisModule {
>      }
>  }
>  
> +/// Returns the current module.
> +#[macro_export]
> +macro_rules! this_module {
> +    () => {
> +        if cfg!(MODULE) {
> +            Some(unsafe { $crate::ThisModule::from_ptr(&mut $crate::bindings::__this_module) })
> +        } else {
> +            None
> +        }
> +    };
> +}

While this is handy, what exactly will it be used for?  The C
wrappers/shim/whatever should probably handle this for you already when
you save this pointer into a structure right?

Surely you aren't trying to increment your own module's reference count,
right?  That just doesn't work :)

thanks,

greg k-h