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[190.15.220.238]) by smtp.gmail.com with ESMTPSA id wi22-20020a056871a71600b00176d49bb898sm11800496oab.44.2023.03.29.07.55.02 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 29 Mar 2023 07:55:05 -0700 (PDT) Message-ID: Date: Wed, 29 Mar 2023 11:55:01 -0300 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.9.0 Subject: Re: [PATCH v2 6/6] rust: error: Add from_result() helper Content-Language: en-US To: Asahi Lina , Miguel Ojeda , Alex Gaynor , Wedson Almeida Filho , Boqun Feng , Gary Guo , =?UTF-8?Q?Bj=c3=b6rn_Roy_Baron?= , Sven Van Asbroeck Cc: Fox Chen , Andreas Hindborg , rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org, asahi@lists.linux.dev References: <20230224-rust-error-v2-0-3900319812da@asahilina.net> <20230224-rust-error-v2-6-3900319812da@asahilina.net> From: Martin Rodriguez Reboredo In-Reply-To: <20230224-rust-error-v2-6-3900319812da@asahilina.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: rust-for-linux@vger.kernel.org On 3/29/23 09:04, Asahi Lina wrote: > [...] > > + > +/// Calls a closure returning a [`crate::error::Result`] and converts the result to > +/// a C integer result. > +/// > +/// This is useful when calling Rust functions that return [`crate::error::Result`] > +/// from inside `extern "C"` functions that need to return an integer error result. > +/// > +/// `T` should be convertible from an `i16` via `From`. > +/// > +/// # Examples > +/// > +/// ```ignore > +/// # use kernel::from_result; > +/// # use kernel::bindings; > +/// unsafe extern "C" fn probe_callback( > +/// pdev: *mut bindings::platform_device, > +/// ) -> core::ffi::c_int { > +/// from_result(|| { > +/// let ptr = devm_alloc(pdev)?; > +/// bindings::platform_set_drvdata(pdev, ptr); > +/// Ok(0) > +/// }) > +/// } > +/// ``` > +// TODO: Remove `dead_code` marker once an in-kernel client is available. > +#[allow(dead_code)] > +pub(crate) fn from_result(f: F) -> T > +where > + T: From, > + F: FnOnce() -> Result, > +{ > + match f() { > + Ok(v) => v, > + // NO-OVERFLOW: negative `errno`s are no smaller than `-bindings::MAX_ERRNO`, > + // `-bindings::MAX_ERRNO` fits in an `i16` as per invariant above, > + // therefore a negative `errno` always fits in an `i16` and will not overflow. > + Err(e) => T::from(e.to_errno() as i16), > + } > +} > Reviewed-by: Martin Rodriguez Reboredo