linux-kernel - Re: [PATCH v2 0/2] Add Opaque::cast

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Message-ID: <9ccd25dc-d642-4fcd-8dbb-ae221fa97556@kernel.org>
Date: Tue, 24 Jun 2025 17:35:52 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
 Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>,
 David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>,
 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>, Trevor Gross <tmgross@...ch.edu>,
 dri-devel@...ts.freedesktop.org, rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] Add Opaque::cast_from

On 6/24/25 5:27 PM, Alice Ryhl wrote:
> Since commit b20fbbc08a36 ("rust: check type of `$ptr` in
> `container_of!`") we have enforced that the field pointer passed to
> container_of! must match the declared field. This caused mismatches when
> using a pointer to bindings::x for fields of type Opaque<bindings::x>.
> 
> This situation encourages the user to simply pass field.cast() to the
> container_of! macro, but this is not great because you might
> accidentally pass a *mut bindings::y when the field type is
> Opaque<bindings::x>, which would be wrong.
> 
> To help catch this kind of mistake, add a new Opaque::cast_from that
> wraps a raw pointer in Opaque without changing the inner type. Also
> rename raw_get() to cast_into() for naming consistency.

Reviewed-by: Danilo Krummrich <dakr@...nel.org>