[0/9] Implement "Bound" device context

Message

Danilo Krummrich March 31, 2025, 8:27 p.m. UTC

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.

This patch series is based on driver-core-next (with rust-next merged into it);
a branch containing the commits can be found in [1]. It is targeting v6.16-rc1.

[1] https://web.git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=rust/device-bound

Danilo Krummrich (9):
  rust: device: implement impl_device_context_deref!
  rust: device: implement impl_device_context_into_aref!
  rust: device: implement device context for Device
  rust: platform: preserve device context in AsRef
  rust: pci: preserve device context in AsRef
  rust: device: implement Bound device context
  rust: pci: move iomap_region() to impl Device<Bound>
  rust: devres: require a bound device
  rust: dma: require a bound device

 rust/kernel/device.rs   | 71 +++++++++++++++++++++++++++++++++++++++--
 rust/kernel/devres.rs   | 17 ++++------
 rust/kernel/dma.rs      | 14 ++++----
 rust/kernel/pci.rs      | 31 ++++++------------
 rust/kernel/platform.rs | 30 ++++-------------
 5 files changed, 98 insertions(+), 65 deletions(-)