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From:   Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date:   Fri, 16 Apr 2021 19:47:32 +0200
Message-ID: <CANiq72nx7ngazsH7sZgc=HeU0cNj45F9+-rwQb7AkdYsRCmRbQ@mail.gmail.com>
Subject: Re: [PATCH 04/13] Kbuild: Rust support
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     Peter Zijlstra <peterz@infradead.org>,
        Miguel Ojeda <ojeda@kernel.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        rust-for-linux@vger.kernel.org,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Alex Gaynor <alex.gaynor@gmail.com>,
        Geoffrey Thomas <geofft@ldpreload.com>,
        Finn Behrens <me@kloenk.de>,
        Adam Bratschi-Kaye <ark.email@gmail.com>,
        Wedson Almeida Filho <wedsonaf@google.com>,
        Michael Ellerman <mpe@ellerman.id.au>
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On Fri, Apr 16, 2021 at 7:05 PM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> Typical Rust error handling should match the regular kernel
> IS_ERR/ERR_PTR/PTR_ERR model fairly well, although the syntax is
> fairly different (and it's not limited to pointers).

Yeah, exactly. We already have a `KernelResult<T>` type which is a
`Result<T, Error>`, where `Error` is a wrapper for the usual kernel
int errors.

So, for instance, a function that can either fail or return `Data`
would have a declaration like:

    pub fn foo() -> KernelResult<Data>

A caller that needs to handle the error can use pattern matching or
one of the methods in `Result`. And if they only need to bubble the
error up, they can use the ? operator:

    pub fn bar() -> KernelResult<Data> {
        let data = foo()?;

        // `data` is already a `Data` here, not a `KernelResult<Data>`
    }

Cheers,
Miguel