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Date: Thu, 12 Jun 2025 17:48:36 +0200
Message-Id: <DAKO8MMSCUE4.1WVR6SBADGP8W@kernel.org>
Cc: <rust-for-linux@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/4] rust: revocable: support fallible PinInit types
From: "Benno Lossin" <lossin@kernel.org>
To: "Danilo Krummrich" <dakr@kernel.org>, <gregkh@linuxfoundation.org>,
 <rafael@kernel.org>, <ojeda@kernel.org>, <alex.gaynor@gmail.com>,
 <boqun.feng@gmail.com>, <gary@garyguo.net>, <bjorn3_gh@protonmail.com>,
 <benno.lossin@proton.me>, <a.hindborg@kernel.org>, <aliceryhl@google.com>,
 <tmgross@umich.edu>
X-Mailer: aerc 0.20.1
References: <20250612145145.12143-1-dakr@kernel.org>
 <20250612145145.12143-2-dakr@kernel.org>
In-Reply-To: <20250612145145.12143-2-dakr@kernel.org>

On Thu Jun 12, 2025 at 4:51 PM CEST, Danilo Krummrich wrote:
> Currently, Revocable::new() only supports infallible PinInit
> implementations, i.e. impl PinInit<T, Infallible>.
>
> This has been sufficient so far, since users such as Devres do not
> support fallibility.
>
> Since this is about to change, make Revocable::new() generic over the
> error type E.
>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  rust/kernel/devres.rs    | 2 +-
>  rust/kernel/revocable.rs | 7 +++++--
>  2 files changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/rust/kernel/devres.rs b/rust/kernel/devres.rs
> index d8bdf2bdb879..a7df9fbd724f 100644
> --- a/rust/kernel/devres.rs
> +++ b/rust/kernel/devres.rs
> @@ -98,7 +98,7 @@ struct DevresInner<T> {
>  impl<T> DevresInner<T> {
>      fn new(dev: &Device<Bound>, data: T, flags: Flags) -> Result<Arc<Dev=
resInner<T>>> {
>          let inner =3D Arc::pin_init(
> -            pin_init!( DevresInner {
> +            try_pin_init!( DevresInner {
>                  dev: dev.into(),
>                  callback: Self::devres_callback,
>                  data <- Revocable::new(data),
> diff --git a/rust/kernel/revocable.rs b/rust/kernel/revocable.rs
> index fa1fd70efa27..41b8fe374af6 100644
> --- a/rust/kernel/revocable.rs
> +++ b/rust/kernel/revocable.rs
> @@ -82,8 +82,11 @@ unsafe impl<T: Sync + Send> Sync for Revocable<T> {}
> =20
>  impl<T> Revocable<T> {
>      /// Creates a new revocable instance of the given data.
> -    pub fn new(data: impl PinInit<T>) -> impl PinInit<Self> {
> -        pin_init!(Self {
> +    pub fn new<E>(data: impl PinInit<T, E>) -> impl PinInit<Self, Error>
> +    where
> +        Error: From<E>,

I don't think we need this bound as you don't use it in the function
body.

---
Cheers,
Benno

> +    {
> +        try_pin_init!(Self {
>              is_available: AtomicBool::new(true),
>              data <- Opaque::pin_init(data),
>          })