linux-kernel - Re: [PATCH 2/3] rust: dma: convert the read/write macros to return Result

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Message-ID: <CANiq72mahS0jiOHv-7RE8QWQunYo0bJqeGo-FAVoUL7v42RsoQ@mail.gmail.com>
Date: Tue, 8 Apr 2025 15:34:12 +0200
From: Miguel Ojeda <miguel.ojeda.sandonis@...il.com>
To: Andreas Hindborg <a.hindborg@...nel.org>
Cc: Benno Lossin <benno.lossin@...ton.me>, Abdiel Janulgue <abdiel.janulgue@...il.com>, ojeda@...nel.org, 
	Danilo Krummrich <dakr@...nel.org>, Daniel Almeida <daniel.almeida@...labora.com>, 
	Robin Murphy <robin.murphy@....com>, Alex Gaynor <alex.gaynor@...il.com>, 
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, 
	"open list:DMA MAPPING HELPERS DEVICE DRIVER API [RUST]" <rust-for-linux@...r.kernel.org>, 
	Marek Szyprowski <m.szyprowski@...sung.com>, 
	"open list:DMA MAPPING HELPERS" <iommu@...ts.linux.dev>, open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/3] rust: dma: convert the read/write macros to return Result

On Tue, Apr 8, 2025 at 2:40 PM Andreas Hindborg <a.hindborg@...nel.org> wrote:
>
> But the `assert_eq!` would panic anyway if comparison fails, right?

Previously the `?` generated by the macro would return out of the
closure written by the sample, and thus it wouldn't reach the
`assert_eq!`.

Expanded:

    let _ = (|| -> Result {
        for (i, value) in TEST_VALUES.into_iter().enumerate() {
            match (
                &{
                    let item = ...::item_from_index(&self.ca, i)?;
                    unsafe { ... }
                },
                &value.0,
            ) {
                (left_val, right_val) => {
                    if !(*left_val == *right_val) {
                        ...::assert_failed(...);
                    }
                }
            };
        }
        Ok(())
    })();

Cheers,
Miguel