References: <20230224-rust-error-v1-0-f8f9a9a87303@asahilina.net>
 <20230224-rust-error-v1-3-f8f9a9a87303@asahilina.net>
User-agent: mu4e 1.9.18; emacs 28.2.50
From:   Andreas Hindborg <nmi@metaspace.dk>
To:     Asahi Lina <lina@asahilina.net>
Cc:     Miguel Ojeda <ojeda@kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Wedson Almeida Filho <wedsonaf@gmail.com>,
        Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>,
        =?utf-8?Q?Bj=C3=B6rn?= Roy Baron <bjorn3_gh@protonmail.com>,
        Sven Van Asbroeck <thesven73@gmail.com>,
        Fox Chen <foxhlchen@gmail.com>, rust-for-linux@vger.kernel.org,
        linux-kernel@vger.kernel.org, asahi@lists.linux.dev
Subject: Re: [PATCH 3/5] rust: error: Add to_result() helper
Date:   Mon, 27 Feb 2023 14:26:02 +0100
In-reply-to: <20230224-rust-error-v1-3-f8f9a9a87303@asahilina.net>
Message-ID: <87lekj9r2u.fsf@metaspace.dk>
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Asahi Lina <lina@asahilina.net> writes:

> From: Wedson Almeida Filho <wedsonaf@gmail.com>
>
> Add a to_result() helper to convert kernel C return values to a Rust
> Result, mapping >=0 values to Ok(()) and negative values to Err(...),
> with Error::from_kernel_errno() ensuring that the errno is within range.
>
> Lina: Imported from rust-for-linux/rust, originally developed by Wedson
> as part of the AMBA device driver support.
>
> Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> ---

Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>

>  rust/kernel/error.rs | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
> index 3b439fdb405c..1e8371f28746 100644
> --- a/rust/kernel/error.rs
> +++ b/rust/kernel/error.rs
> @@ -167,3 +167,13 @@ impl From<core::convert::Infallible> for Error {
>  /// it should still be modeled as returning a `Result` rather than
>  /// just an [`Error`].
>  pub type Result<T = ()> = core::result::Result<T, Error>;
> +
> +/// Converts an integer as returned by a C kernel function to an error if it's negative, and
> +/// `Ok(())` otherwise.
> +pub fn to_result(err: core::ffi::c_int) -> Result {
> +    if err < 0 {
> +        Err(Error::from_kernel_errno(err))
> +    } else {
> +        Ok(())
> +    }
> +}