linux-kernel - Re: [PATCH v2 0/9] Implement "Bound" device context

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Message-ID: <aAEaubIVd9XDflxc@cassiopeiae>
Date: Thu, 17 Apr 2025 17:14:01 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: bhelgaas@...gle.com, kwilczynski@...nel.org, gregkh@...uxfoundation.org,
	rafael@...nel.org, abdiel.janulgue@...il.com
Cc: 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,
	daniel.almeida@...labora.com, robin.murphy@....com,
	linux-pci@...r.kernel.org, rust-for-linux@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/9] Implement "Bound" device context

On Sun, Apr 13, 2025 at 07:36:55PM +0200, Danilo Krummrich wrote:
> Currently, we do not ensure that APIs that require a bound device instance can
> only be called with a bound device.
> 
> Examples of such APIs are Devres, dma::CoherentAllocation and
> pci::Device::iomap_region().
> 
> This patch series introduces the "Bound" device context such that we can ensure
> to only ever pass a bound device to APIs that require this precondition.
> 
> In order to get there, we need some prerequisites:
> 
> (1) Implement macros to consistently derive Deref implementations for the
>     different device contexts. For instance, Device<Core> can be dereferenced to
>     Device<Bound>, since all device references we get from "core" bus callbacks
>     are guaranteed to be from a bound device. Device<Bound> can always be
>     dereferenced to Device (i.e. Device<Normal>), since the "Normal" device
>     context has no specific requirements.
> 
> (2) Implement device context support for the generic Device type. Some APIs such
>     as Devres and dma::CoherentAllocation work with generic devices.
> 
> (3) Preserve device context generics in bus specific device' AsRef
>     implementation, such that we can derive the device context when converting
>     from a bus specific device reference to a generic device reference.
> 
> With this, Devres::new(), for instance, can take a &Device<Bound> argument and
> hence ensure that it can't be called with a Device reference that is not
> guaranteed to be bound to a driver.
> 
> A branch containing the patches can be found in [1].
> 
> [1] https://web.git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=rust/device-bound

With the following changes, applied to driver-core/topic/device-context, thanks!

  *  Add missing `::` prefix in macros.
  *  Fix typos pointed out by Bjorn.

- Danilo