Message-ID: <4224983e-7788-4c40-8046-a67e67c9d052@nvidia.com>
Date: Mon, 1 Dec 2025 14:52:34 -0800
From: John Hubbard <jhubbard@...dia.com>
To: Joel Fernandes <joelagnelf@...dia.com>, linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org, dri-devel@...ts.freedesktop.org,
 nouveau@...ts.freedesktop.org, Danilo Krummrich <dakr@...nel.org>,
 Dave Airlie <airlied@...il.com>
Cc: Alexandre Courbot <acourbot@...dia.com>,
 Alistair Popple <apopple@...dia.com>, Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>, Boqun Feng <boqun.feng@...il.com>,
 Gary Guo <gary@...yguo.net>, 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>,
 Simona Vetter <simona@...ll.ch>,
 Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 Timur Tabi <ttabi@...dia.com>, Joel Fernandes <joel@...lfernandes.org>,
 Lyude Paul <elle@...thered-steel.dev>,
 Daniel Almeida <daniel.almeida@...labora.com>,
 Andrea Righi <arighi@...dia.com>, Philipp Stanner <phasta@...nel.org>
Subject: Re: [PATCH v3] rust: clist: Add support to interface with C linked
 lists

On 12/1/25 2:43 PM, Joel Fernandes wrote:
> On 12/1/2025 5:17 PM, John Hubbard wrote:
>> On 12/1/25 12:32 PM, Joel Fernandes wrote:
>>> On 11/30/2025 7:34 PM, John Hubbard wrote:
>>>> On 11/29/25 1:30 PM, Joel Fernandes wrote:
>> ...
> You may want to read [1]. CONFIG_RUST_KERNEL_DOCTESTS are run at runtime. You
> enable it and boot the kernel. The documentation clearly says "doctests get
> compiled as Rust kernel objects, allowing them to run against a built kernel.".
> And this is how I have run it as well.
> 
> [1] https://docs.kernel.org/rust/testing.html
> 
> This also explains why you think list_add_tail() is a noop in my patch, which it
> is not.

Yes, I forgot that they are actually run, you are right.

> 
>>
>> I would humbly suggest that you build and *run* your own samples code, for
>> new code that has no users yet.
> 
> Yes, I already have an internal tree running it. :) I am not sure why the
> assume_init() triggered for you but not for me, I don't think has anything to do
> with doctests since the doctests is in fact just rust code compiled as KUNIT tests.

I think it's because I wrote separate code that was not a doctest, and
that code is naturally different from however the doctest exercised it.
But it is a good question.

> 
>> Because if you are skipping steps like this (posting the code before
>> there is an actual caller), then the documentation of how to use it
>> is not "just documentation" anymore--it really needs to run correctly.
> 
> No, that's the thing, these are run. You really are in the wrong here and appear
> to not understand how doctests work.

That's a reasonable statement. :)

> 
>> And actually, after writing the above...I still think it would be better
>> to post this with its first caller (DRM_BUDDY, or BUDDY_DRM_ALUMNI, or
>> however it ends up), so that we can see how it looks and behaves in
>> practice.
>>
>> What's the rush?
> 
> Who said anything about a rush? I am really confused by what you mean. It is
> useful to post patches even if there are external dependencies to get feedback.
> So this is also an invalid review comment unfortunately. There is no rush, this
> is v3 now, did you miss that?
> 

I mean, doctests are far weaker than actual code that uses the new API.
It feels rushed to propose merging code without a caller. And I don't
think doctests are a "real enough" caller.

thanks,
-- 
John Hubbard

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