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Date:   Wed, 29 Mar 2023 21:36:14 +0100
From:   Gary Guo <gary@garyguo.net>
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>,
        =?UTF-8?B?QmrDtnJu?= Roy Baron <bjorn3_gh@protonmail.com>,
        Sven Van Asbroeck <thesven73@gmail.com>,
        Fox Chen <foxhlchen@gmail.com>,
        Martin Rodriguez Reboredo <yakoyoku@gmail.com>,
        Andreas Hindborg <a.hindborg@samsung.com>,
        rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org,
        asahi@lists.linux.dev
Subject: Re: [PATCH v2 4/6] rust: error: Add to_result() helper
Message-ID: <20230329213614.5fa23dba.gary@garyguo.net>
In-Reply-To: <20230224-rust-error-v2-4-3900319812da@asahilina.net>
References: <20230224-rust-error-v2-0-3900319812da@asahilina.net>
        <20230224-rust-error-v2-4-3900319812da@asahilina.net>
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On Wed, 29 Mar 2023 21:04:36 +0900
Asahi Lina <lina@asahilina.net> wrote:

> 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_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>
> Reviewed-by: Andreas Hindborg <a.hindborg@samsung.com>
> Signed-off-by: Asahi Lina <lina@asahilina.net>
> ---
>  rust/kernel/error.rs | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
> index 659468bd1735..4f599c4d1752 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_errno(err))
> +    } else {
> +        Ok(())
> +    }
> +}
> 

Reviewed-by: Gary Guo <gary@garyguo.net>