linux-kernel - Re: [PATCH 1/4] rust: dma: implement DataDirection

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Message-ID: <CAH5fLgjymw6Mr8qv8NDFA8hz+nfh3-B4XcZ_N-UAmJrc3Ug_QQ@mail.gmail.com>
Date: Mon, 18 Aug 2025 20:47:57 +0200
From: Alice Ryhl <aliceryhl@...gle.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: akpm@...ux-foundation.org, ojeda@...nel.org, alex.gaynor@...il.com, 
	boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com, 
	lossin@...nel.org, a.hindborg@...nel.org, tmgross@...ch.edu, 
	abdiel.janulgue@...il.com, acourbot@...dia.com, jgg@...pe.ca, 
	lyude@...hat.com, robin.murphy@....com, daniel.almeida@...labora.com, 
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/4] rust: dma: implement DataDirection

On Mon, Aug 18, 2025 at 7:23 PM Danilo Krummrich <dakr@...nel.org> wrote:
>
> On Mon Aug 18, 2025 at 4:00 PM CEST, Alice Ryhl wrote:
> > In general, I think we want some sort of helper function to cast
> > between arbitrary integer types in const-evaluation that panics if the
> > cast is out of bounds. Both here and many other places.
>
> What exactly do you have in mind?

        pub enum DataDirection {
            /// The DMA mapping is for bidirectional data transfer.
            ///
            /// This is used when the buffer can be both read from and
written to by the device.
            /// The cache for the corresponding memory region is both
flushed and invalidated.
            Bidirectional =
const_cast(bindings::dma_data_direction_DMA_BIDIRECTIONAL),

with no warnings and build-failure if out-of-bounds.

Alice