linux-kernel - Re: [PATCH v2 6/6] soc: qcom: socinfo: Convert to Rust

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Message-Id: <DG5HGZG62NNS.18BCSOO6TR70G@kernel.org>
Date: Tue, 03 Feb 2026 17:56:14 +0100
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Cc: "Matthew Maurer" <mmaurer@...gle.com>, "Bjorn Andersson"
 <andersson@...nel.org>, "Konrad Dybcio" <konradybcio@...nel.org>, "Satya
 Durga Srinivasu Prabhala" <satyap@...cinc.com>, "Miguel Ojeda"
 <ojeda@...nel.org>, "Boqun Feng" <boqun.feng@...il.com>, "Gary Guo"
 <gary@...yguo.net>, Björn Roy Baron
 <bjorn3_gh@...tonmail.com>, "Benno Lossin" <lossin@...nel.org>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Alice Ryhl" <aliceryhl@...gle.com>,
 "Trevor Gross" <tmgross@...ch.edu>, "Daniel Almeida"
 <daniel.almeida@...labora.com>, "Rafael J. Wysocki" <rafael@...nel.org>,
 "David Airlie" <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>,
 "Michal Wilczynski" <m.wilczynski@...sung.com>, "Dave Ertman"
 <david.m.ertman@...el.com>, "Ira Weiny" <ira.weiny@...el.com>, "Leon
 Romanovsky" <leon@...nel.org>, "Trilok Soni" <tsoni@...cinc.com>,
 <linux-kernel@...r.kernel.org>, <linux-arm-msm@...r.kernel.org>,
 <rust-for-linux@...r.kernel.org>, <driver-core@...ts.linux.dev>,
 <dri-devel@...ts.freedesktop.org>, <linux-pwm@...r.kernel.org>
Subject: Re: [PATCH v2 6/6] soc: qcom: socinfo: Convert to Rust

On Tue Feb 3, 2026 at 5:48 PM CET, Greg Kroah-Hartman wrote:
> On Tue, Feb 03, 2026 at 05:35:24PM +0100, Danilo Krummrich wrote:
>> On Tue Feb 3, 2026 at 5:28 PM CET, Greg Kroah-Hartman wrote:
>> > On Tue, Feb 03, 2026 at 03:46:35PM +0000, Matthew Maurer wrote:
>> >> +impl Smem {
>> >> +    pub(crate) fn access<'a>(&'a self, dev: &'a Device<Bound>) -> Option<&'a Mmio> {
>> >> +        if *dev != *self.dev {
>> >
>> > How can this ever happen?
>> 
>> You are right, since this resource is local to the driver, it should not be
>> possible to have another devce from somewhere else (especially not a
>> &Device<Bound>).
>> 
>> However, from a Rust perspective I think not having this check would be unsound,
>> as the method by itself would not be able guarantee correct behavor anymore.
>> 
>
> I don't really understand this last sentence, sorry.  If this is "not
> possible" why would that at the same time be "unsound"?

It would be considered unsound because the function itself can not guarantee
that it does not produce undefined behavior, i.e. it would otherwise becomes
unsafe.

But I'm not an expert on this, I'll let Benno and Gary jump in.