linux-kernel - Re: [PATCH v2] rust: alloc: allow coercion from `Box<T>` to `Box<dyn U>` if T implements U

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Message-ID: <Z_kltpjo9bn4ah-l@cassiopeiae>
Date: Fri, 11 Apr 2025 16:22:46 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Alexandre Courbot <acourbot@...dia.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>,
	Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>,
	Björn Roy Baron <bjorn3_gh@...tonmail.com>,
	Benno Lossin <benno.lossin@...ton.me>,
	Andreas Hindborg <a.hindborg@...nel.org>,
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] rust: alloc: allow coercion from `Box<T>` to `Box<dyn
 U>` if T implements U

On Fri, Apr 11, 2025 at 10:26:23PM +0900, Alexandre Courbot wrote:
> On Fri Apr 11, 2025 at 10:10 PM JST, Danilo Krummrich wrote:
> > On Fri, Apr 11, 2025 at 09:07:26PM +0900, Alexandre Courbot wrote:
> >> This enables the creation of trait objects backed by a Box, similarly to
> >> what can be done with the standard library.
> >> 
> >> Suggested-by: Benno Lossin <benno.lossin@...ton.me>
> >> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>
> >
> > I assume you have a specific use-case in nova-core for this? For this cycle, can
> > you get away without having this in nova-core?
> 
> That's correct, and our next nova-core iteration will likely depend on
> this to provide some basic HAL. If this cannot make it for this cycle, I
> guess I can always use Arc temporarily.

I'd prefer to take this through the alloc tree (for this cycle), but this also
means you can't use it until the next cycle in nova. I assume that's just a
minor inconvinience?