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Date: Mon, 02 Feb 2026 15:21:18 +0100
Message-Id: <DG4JJTAZ90DS.S76K5YX47PBE@kernel.org>
Subject: Re: [PATCH 3/6] rust: io: provide Mmio relaxed ops through a
 wrapper type
Cc: "Alexandre Courbot" <acourbot@nvidia.com>, "Alice Ryhl"
 <aliceryhl@google.com>, "Daniel Almeida" <daniel.almeida@collabora.com>,
 "Miguel Ojeda" <ojeda@kernel.org>, "Boqun Feng" <boqun.feng@gmail.com>,
 =?utf-8?q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, "Benno Lossin"
 <lossin@kernel.org>, "Andreas Hindborg" <a.hindborg@kernel.org>, "Trevor
 Gross" <tmgross@umich.edu>, "Bjorn Helgaas" <bhelgaas@google.com>,
 =?utf-8?q?Krzysztof_Wilczy=C5=84ski?= <kwilczynski@kernel.org>,
 <driver-core@lists.linux.dev>, <rust-for-linux@vger.kernel.org>,
 <linux-kernel@vger.kernel.org>, <linux-pci@vger.kernel.org>, "Zhi Wang"
 <zhiw@nvidia.com>, "Lyude Paul" <lyude@redhat.com>, "Eliot Courtney"
 <ecourtney@nvidia.com>
To: "Gary Guo" <gary@garyguo.net>
From: "Danilo Krummrich" <dakr@kernel.org>
References: <20260202-io-v1-0-9bb2177d23be@nvidia.com>
 <20260202-io-v1-3-9bb2177d23be@nvidia.com>
 <DG4J98HVOUEX.I7XOB7LPB49L@garyguo.net>
 <DG4JHKY0Y19S.24TZ7TAX5ISD@kernel.org>
In-Reply-To: <DG4JHKY0Y19S.24TZ7TAX5ISD@kernel.org>

On Mon Feb 2, 2026 at 3:18 PM CET, Danilo Krummrich wrote:
> On Mon Feb 2, 2026 at 3:07 PM CET, Gary Guo wrote:
>> I think ultimately choice of order to use for each I/O access is local t=
o the
>> specific access, not a global property.
>>
>> I know you can just do `RelaxedMmio::from(io).access()` for each single =
access
>> too, but it feels quite verbose.
>
> mmio.relaxed().access() would work as well.
>
>> I guess one alternative design is explicit order on the access, e.g.
>>
>>     io.read32(Relaxed)
>>
>> Or
>>
>>     io.read32(Full)
>>
>> however this is verbose in some other ways... I'd like to hear how Boqun=
 thinks
>> on this one.
>
> This apprach would be misleading for a lot of other I/O backends. For ins=
tance,
> the I2C bus has no relaxed ordering.

Forgot to mention, relaxed ordering accesses are far less common, hence thi=
s
would become unnecessarily verbose.