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Date: Fri, 30 May 2025 23:27:14 +0200
Message-Id: <DA9TATN3QCAW.3V5G2YL8OV23P@kernel.org>
Cc: <rust-for-linux@vger.kernel.org>, <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/7] rust: types: support fallible PinInit types in
 Opaque::pin_init
From: "Benno Lossin" <lossin@kernel.org>
To: "Christian Schrefl" <chrisi.schrefl@gmail.com>, "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>
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References: <20250530142447.166524-1-dakr@kernel.org>
 <20250530142447.166524-2-dakr@kernel.org>
 <DA9QST4SISFK.37NSCTH594NSF@kernel.org>
 <6dfafb34-8b85-4f54-9453-c39297d1f851@gmail.com>
In-Reply-To: <6dfafb34-8b85-4f54-9453-c39297d1f851@gmail.com>

On Fri May 30, 2025 at 10:11 PM CEST, Christian Schrefl wrote:
> On 30.05.25 9:29 PM, Benno Lossin wrote:
>> On Fri May 30, 2025 at 4:24 PM CEST, Danilo Krummrich wrote:
>>> -    pub fn pin_init(slot: impl PinInit<T>) -> impl PinInit<Self> {
>>> -        Self::ffi_init(|ptr: *mut T| {
>>> +    pub fn pin_init<E>(slot: impl PinInit<T, E>) -> impl PinInit<Self,=
 E> {
>>> +        Self::try_ffi_init(|ptr: *mut T| -> Result<(), E> {
>>>              // SAFETY:
>>>              //   - `ptr` is a valid pointer to uninitialized memory,
>>> -            //   - `slot` is not accessed on error; the call is infall=
ible,
>>> +            //   - `slot` is not accessed on error,
>>>              //   - `slot` is pinned in memory.
>>> -            let _ =3D unsafe { PinInit::<T>::__pinned_init(slot, ptr) =
};
>>> +            unsafe { PinInit::<T, E>::__pinned_init(slot, ptr) }
>>=20
>> Could you move this function into an `impl pin_init::Wrapper<T>` block?
>> (it's the same function, but in a trait that was recently added)
>
> This is then basically this patch [0] from my `UnsafePinned` series.
> Just that I did not update the comment. :)
>
> [0]: https://lore.kernel.org/rust-for-linux/20250511-rust_unsafe_pinned-v=
4-2-a86c32e47e3d@gmail.com/=20

Oh yeah, I completely forgot we had this... I even reviewed it haha!

---
Cheers,
Benno