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Date: Fri, 16 Jan 2026 16:27:27 +0100
Message-Id: <DFQ4B7CJR5EW.TMEE2YAES7O2@kernel.org>
Cc: "Alice Ryhl" <aliceryhl@google.com>, "Zhi Wang" <zhiw@nvidia.com>,
 <rust-for-linux@vger.kernel.org>, <linux-pci@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>, <bhelgaas@google.com>,
 <kwilczynski@kernel.org>, <ojeda@kernel.org>, <alex.gaynor@gmail.com>,
 <boqun.feng@gmail.com>, <bjorn3_gh@protonmail.com>, <lossin@kernel.org>,
 <a.hindborg@kernel.org>, <tmgross@umich.edu>, <markus.probst@posteo.de>,
 <helgaas@kernel.org>, <cjia@nvidia.com>, <smitra@nvidia.com>,
 <ankita@nvidia.com>, <aniketa@nvidia.com>, <kwankhede@nvidia.com>,
 <targupta@nvidia.com>, <acourbot@nvidia.com>, <joelagnelf@nvidia.com>,
 <jhubbard@nvidia.com>, <zhiwang@kernel.org>,
 <daniel.almeida@collabora.com>, <markus.probst@posteo.de>
To: "Gary Guo" <gary@garyguo.net>
From: "Danilo Krummrich" <dakr@kernel.org>
Subject: Re: [PATCH v9 2/5] rust: io: factor common I/O helpers into Io
 trait
References: <20260115212657.399231-1-zhiw@nvidia.com>
 <20260115212657.399231-3-zhiw@nvidia.com> <aWoWntMxyhBc9Unx@google.com>
 <DFQ481S2NI1S.3HMMZMYEQ9QP8@garyguo.net>
In-Reply-To: <DFQ481S2NI1S.3HMMZMYEQ9QP8@garyguo.net>

(Cc: Markus)

On Fri Jan 16, 2026 at 4:23 PM CET, Gary Guo wrote:
> I wonder if we can keep all methods on `Io` trait. And then have marker t=
rait to
> represent capability on performing Io access.
>
> Something like:
>
> trait IoCapable<T> {}
>
> trait Io {
>      fn read8(&self, offset: usize) -> u8 where Self: IoCapable<u8>;
>      fn read16(&self, offset: usize) -> u16 where Self: IoCapable<u16>;
>      fn read32(&self, offset: usize) -> u32 where Self: IoCapable<u32>;
>      fn read64(&self, offset: usize) -> u64 where Self: IoCapable<u64>;
> }
>
> Then you have a single (non-marker) trait and not a hierachy of them.

I think that is a great idea. I think it will also help with supporting I/O
backends based on regmap.