linux-kernel - Re: [PATCH 1/7] rust: types: support fallible PinInit types in Opaque::pin

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Message-ID: <6dfafb34-8b85-4f54-9453-c39297d1f851@gmail.com>
Date: Fri, 30 May 2025 22:11:00 +0200
From: Christian Schrefl <chrisi.schrefl@...il.com>
To: Benno Lossin <lossin@...nel.org>, Danilo Krummrich <dakr@...nel.org>,
 gregkh@...uxfoundation.org, rafael@...nel.org, ojeda@...nel.org,
 alex.gaynor@...il.com, boqun.feng@...il.com, gary@...yguo.net,
 bjorn3_gh@...tonmail.com, benno.lossin@...ton.me, a.hindborg@...nel.org,
 aliceryhl@...gle.com, tmgross@...ch.edu
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/7] rust: types: support fallible PinInit types in
 Opaque::pin_init



On 30.05.25 9:29 PM, Benno Lossin wrote:
> On Fri May 30, 2025 at 4:24 PM CEST, Danilo Krummrich wrote:
>> Currently, Opaque::pin_init only supports infallible PinInit
>> implementations, i.e. impl PinInit<T, Infallible>.
>>
>> This has been sufficient so far, since users such as Revocable do not
>> support fallibility.
>>
>> Since this is about to change, make Opaque::pin_init() generic over the
>> error type E.
>>
>> Signed-off-by: Danilo Krummrich <dakr@...nel.org>
>> ---
>>  rust/kernel/types.rs | 8 ++++----
>>  1 file changed, 4 insertions(+), 4 deletions(-)
>>
>> diff --git a/rust/kernel/types.rs b/rust/kernel/types.rs
>> index 22985b6f6982..75c99d6facf9 100644
>> --- a/rust/kernel/types.rs
>> +++ b/rust/kernel/types.rs
>> @@ -354,13 +354,13 @@ pub const fn zeroed() -> Self {
>>      }
>>  
>>      /// Create an opaque pin-initializer from the given pin-initializer.
>> -    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 infallible,
>> +            //   - `slot` is not accessed on error,
>>              //   - `slot` is pinned in memory.
>> -            let _ = unsafe { PinInit::<T>::__pinned_init(slot, ptr) };
>> +            unsafe { PinInit::<T, E>::__pinned_init(slot, ptr) }
> 
> 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-v4-2-a86c32e47e3d@gmail.com/ 

> 
> Thanks!
> 
> ---
> Cheers,
> Benno
> 
>>          })
>>      }
>>  
>