linux-kernel - Re: [PATCH v6 3/6] rust: irq: add support for non-threaded IRQs and handlers

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Message-Id: <18B23FD3-56E9-4531-A50C-F204616E7D17@collabora.com>
Date: Sun, 13 Jul 2025 11:48:53 -0300
From: Daniel Almeida <daniel.almeida@...labora.com>
To: Danilo Krummrich <dakr@...nel.org>
Cc: Benno Lossin <lossin@...nel.org>,
 Miguel Ojeda <ojeda@...nel.org>,
 Alex Gaynor <alex.gaynor@...il.com>,
 Boqun Feng <boqun.feng@...il.com>,
 Gary Guo <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>,
 Andreas Hindborg <a.hindborg@...nel.org>,
 Alice Ryhl <aliceryhl@...gle.com>,
 Trevor Gross <tmgross@...ch.edu>,
 Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Thomas Gleixner <tglx@...utronix.de>,
 Bjorn Helgaas <bhelgaas@...gle.com>,
 Krzysztof Wilczyński <kwilczynski@...nel.org>,
 linux-kernel@...r.kernel.org,
 rust-for-linux@...r.kernel.org,
 linux-pci@...r.kernel.org
Subject: Re: [PATCH v6 3/6] rust: irq: add support for non-threaded IRQs and
 handlers

> On 13 Jul 2025, at 11:27, Danilo Krummrich <dakr@...nel.org> wrote:
> 
> On Sun Jul 13, 2025 at 4:19 PM CEST, Danilo Krummrich wrote:
>> On Sun Jul 13, 2025 at 4:09 PM CEST, Daniel Almeida wrote:
>>> On a second look, I wonder how useful this will be.
>>> 
>>> fn handle(&self, dev: &Device<Bound>) -> IrqReturn
>>> 
>>> Sorry for borrowing this terminology, but here we offer Device<Bound>, while I
>>> suspect that most drivers will be looking for the most derived Device type
>>> instead. So for drm drivers this will be drm::Device, for example, not the base
>>> dev::Device type. I assume that this pattern will hold for other subsystems as
>>> well.
>>> 
>>> Which brings me to my second point: drivers can store an ARef<drm::Device> on
>>> the handler itself, and I assume that the same will be possible in other
>>> subsystems.
>> 
>> Well, the whole point is that you can use a &Device<Bound> to directly access
>> device resources without any overhead, i.e.
>> 
>> fn handle(&self, dev: &Device<Bound>) -> IrqReturn {
>>   let io = self.iomem.access(dev);
>> 
>>   io.write32(...);
>> }
> 
> So, yes, you can store anything in your handler, but the &Device<Bound> is a
> cookie for the scope.

Fine, but can’t you get a &Device<Bound> from a ARef<drm::Device>, for example?
Perhaps a nicer solution would be to offer this capability instead?