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From:   Asahi Lina <lina@asahilina.net>
Date:   Mon, 03 Apr 2023 18:48:13 +0900
Subject: [PATCH v3 4/6] rust: error: Add to_result() helper
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Message-Id: <20230224-rust-error-v3-4-03779bddc02b@asahilina.net>
References: <20230224-rust-error-v3-0-03779bddc02b@asahilina.net>
In-Reply-To: <20230224-rust-error-v3-0-03779bddc02b@asahilina.net>
To:     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>
Cc:     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, Asahi Lina <lina@asahilina.net>
Precedence: bulk

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>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.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 1af0d75d3a73..e8697ad6b62e 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -178,3 +178,13 @@ 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(())
+    }
+}

-- 
2.40.0