linux-kernel - Re: [PATCH v2 1/4] rust: io: Add big-endian read and write functions

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Message-Id: <DG6A0WRA0JZC.SPDT9WEXF92K@kernel.org>
Date: Wed, 04 Feb 2026 16:18:47 +0100
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Link Mauve" <linkmauve@...kmauve.fr>
Cc: <rust-for-linux@...r.kernel.org>, "Madhavan Srinivasan"
 <maddy@...ux.ibm.com>, "Michael Ellerman" <mpe@...erman.id.au>, "Nicholas
 Piggin" <npiggin@...il.com>, "Christophe Leroy (CS GROUP)"
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 Jonathan Neuschäfer <j.neuschaefer@....net>
Subject: Re: [PATCH v2 1/4] rust: io: Add big-endian read and write
 functions

On Wed Feb 4, 2026 at 5:04 AM CET, Link Mauve wrote:
> Another option would be to call u32::swap_bytes() on the data being
> read/written, but these helpers make the Rust code as ergonomic as the C
> code.
>
> Signed-off-by: Link Mauve <linkmauve@...kmauve.fr>

The I/O stuff recently changed quite significantly, please have a look at the
driver-core-next branch [1] in the driver-core tree.

Also, instead of providing additional *be() methods, we should just create a new
type io::Endianness and use it to indicate the device endianness when requesting
the I/O resource.

For instance, for your driver we could have

	request.iomap_exclusive_sized::<8>(Endianness::Big)?

and then let the I/O backend choose the correct accessors based on this.

I.e. the device is either big or little endian, hence we don't need to provide
both accessors at the same time.

[1] https://git.kernel.org/pub/scm/linux/kernel/git/driver-core/driver-core.git/log/?h=driver-core-next