linux-kernel - Re: [PATCH] rust: irq: add support for request

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Message-Id: <71A92388-A636-47F4-9B1C-0154D9AA9839@collabora.com>
Date: Wed, 15 Jan 2025 09:31:22 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Gary Guo <gary@...yguo.net>
Cc: Alice Ryhl <aliceryhl@...gle.com>,
 Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Benno Lossin <benno.lossin@...ton.me>,
 Andreas Hindborg <a.hindborg@...nel.org>,
 Trevor Gross <tmgross@...ch.edu>,
 linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org
Subject: Re: [PATCH] rust: irq: add support for request_irq()



> On 15 Jan 2025, at 08:38, Gary Guo <gary@...yguo.net> wrote:
> 
> On Tue, 14 Jan 2025 15:57:57 -0300
> Daniel Almeida <daniel.almeida@...labora.com> wrote:
> 
>>> 
>>> It's not the pin_init! stuff, but the Opaque stuff. If it fails, then
>>> it runs the destructor of Opaque<T>, which does *not* run the
>>> destructor of T.
>>> 
>>> Alice  
>> 
>> This is pretty unintuitive if you take into account trivial examples like
>> 
>> ```
>> struct Foo(T)
>> ```
>> 
>> Where dropping Foo drops T.
>> 
>> Is there any reason why dropping Opaque<T> doesn’t behave similarly?
>> 
>> — Daniel
> 
> `Opaque` means that "this is a blob of bytes and don't touch it". It
> can be uninitialized, so no meaningful action can be performed when
> it's dropped.
> 
> Best,
> Gary
> 

I really think that the documentation for this type has to be improved somehow.

How is this a blob of bytes that can’t be touched, if it gives out a *mut T?

I think I’ve consistently seen code that either accesses or mutates the inner T through
the pointer.