linux-kernel - Re: [PATCH v6 RESEND 4/7] rust: io: factor common I/O helpers into Io trait

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Message-ID: <dbb5ff04-83be-4caf-b7c2-4360b39959e5@nvidia.com>
Date: Tue, 18 Nov 2025 15:43:56 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Alice Ryhl <aliceryhl@...gle.com>, Zhi Wang <zhiw@...dia.com>,
 rust-for-linux@...r.kernel.org, linux-pci@...r.kernel.org,
 linux-kernel@...r.kernel.org, bhelgaas@...gle.com, kwilczynski@...nel.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, markus.probst@...teo.de,
 helgaas@...nel.org, cjia@...dia.com, smitra@...dia.com, ankita@...dia.com,
 aniketa@...dia.com, kwankhede@...dia.com, targupta@...dia.com,
 acourbot@...dia.com, joelagnelf@...dia.com, zhiwang@...nel.org
Subject: Re: [PATCH v6 RESEND 4/7] rust: io: factor common I/O helpers into Io
 trait

On 11/18/25 1:18 PM, Danilo Krummrich wrote:
> On Tue Nov 18, 2025 at 11:44 AM NZDT, John Hubbard wrote:
...
>> Other IO subsystems can also get IO errors, too.
>>
>> I wonder if we should just provide IoFallible? (It could check for the
>> 0xFFFF_FFFF case, for example, which is helpful to simplify the caller.)
> 
> For some registers this could be an expected value, plus a device can fall off
> the bus during a read was well, leaving you with broken data.
> 
> I don't think trying to make all I/O operations fallible is the way to go, it's
> just unreliable to detect in the generic layer. Instead, drivers should perform
> a plausibility check on the read values (which they have to do anyways).

OK, I feel more comfortable with the approach now, thanks.

In return, I'll resist making jokes about calling it IoMostlyFallible.
You're welcome. haha :)


thanks,
-- 
John Hubbard