linux-kernel - Re: [PATCH v2 09/10] rust: pci: add basic PCI device / driver abstractions

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Date: Tue, 25 Jun 2024 15:33:24 +0200
From: Danilo Krummrich <dakr@...hat.com>
To: Andreas Hindborg <nmi@...aspace.dk>
Cc: gregkh@...uxfoundation.org, rafael@...nel.org, bhelgaas@...gle.com,
	ojeda@...nel.org, alex.gaynor@...il.com, wedsonaf@...il.com,
	boqun.feng@...il.com, gary@...yguo.net, bjorn3_gh@...tonmail.com,
	benno.lossin@...ton.me, a.hindborg@...sung.com,
	aliceryhl@...gle.com, airlied@...il.com, fujita.tomonori@...il.com,
	lina@...hilina.net, pstanner@...hat.com, ajanulgu@...hat.com,
	lyude@...hat.com, robh@...nel.org, daniel.almeida@...labora.com,
	rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-pci@...r.kernel.org
Subject: Re: [PATCH v2 09/10] rust: pci: add basic PCI device / driver
 abstractions

On Tue, Jun 25, 2024 at 12:53:48PM +0200, Andreas Hindborg wrote:
> Hi Danilo,
> 
> Thanks for working on this. I just finished rebasing the Rust NVMe
> driver on these patches, and I have just one observation for now.
> 
> Danilo Krummrich <dakr@...hat.com> writes:
> 
> [...]
> 
> > +pub trait Driver {
> > +    /// Data stored on device by driver.
> > +    ///
> > +    /// Corresponds to the data set or retrieved via the kernel's
> > +    /// `pci_{set,get}_drvdata()` functions.
> > +    ///
> > +    /// Require that `Data` implements `ForeignOwnable`. We guarantee to
> > +    /// never move the underlying wrapped data structure.
> > +    ///
> > +    /// TODO: Use associated_type_defaults once stabilized:
> > +    ///
> > +    /// `type Data: ForeignOwnable = ();`
> > +    type Data: ForeignOwnable;
> > +
> > +    /// The type holding information about each device id supported by the driver.
> > +    ///
> > +    /// TODO: Use associated_type_defaults once stabilized:
> > +    ///
> > +    /// type IdInfo: 'static = ();
> > +    type IdInfo: 'static;
> > +
> > +    /// The table of device ids supported by the driver.
> > +    const ID_TABLE: IdTable<'static, DeviceId, Self::IdInfo>;
> > +
> > +    /// PCI driver probe.
> > +    ///
> > +    /// Called when a new platform device is added or discovered.
> > +    /// Implementers should attempt to initialize the device here.
> > +    fn probe(dev: &mut Device, id: Option<&Self::IdInfo>) -> Result<Self::Data>;
> 
> Since you changed the `Device` representation to be basically an `ARef`,
> the `&mut` makes no sense. I think we should either pass by value or
> immutable reference.

Agreed, I think we should just pass it by value.

I also noticed that I need to fix `set_master` and `enable_device_mem` to
require a mutable reference.

> 
> 
> Best regards,
> Andreas
> 
> 
> > +
> > +    /// PCI driver remove.
> > +    ///
> > +    /// Called when a platform device is removed.
> > +    /// Implementers should prepare the device for complete removal here.
> > +    fn remove(data: &Self::Data);
> > +}
> > +
> > +/// The PCI device representation.
> > +///
> > +/// A PCI device is based on an always reference counted `device:Device` instance. Cloning a PCI
> > +/// device, hence, also increments the base device' reference count.
> > +#[derive(Clone)]
> > +pub struct Device(ARef<device::Device>);
> > +
>