Re: [PATCH v3 10/27] rust: pci: make Driver trait lifetime-parameterized

["Gary Guo" <gary@garyguo.net>]

On Sun May 17, 2026 at 1:00 AM BST, Danilo Krummrich wrote:
> Add a 'bound lifetime to the associated Data, changing type Data to type
> Data<'bound>.
>
> This allows the driver's bus device private data to capture the device /
> driver bound lifetime; device resources can be stored directly by
> reference rather than requiring Devres.
>
> The probe() and unbind() callbacks thus gain a 'bound lifetime parameter
> on the methods themselves; avoiding a global lifetime on the trait impl.
>
> Existing drivers set type Data<'bound> = Self, preserving the current
> behavior.
>
> Signed-off-by: Danilo Krummrich <dakr@kernel.org>
> ---
>  drivers/gpu/nova-core/driver.rs       |  9 ++++++---
>  rust/kernel/pci.rs                    | 24 +++++++++++++-----------
>  samples/rust/rust_dma.rs              |  7 +++++--
>  samples/rust/rust_driver_auxiliary.rs |  7 +++++--
>  samples/rust/rust_driver_pci.rs       |  7 +++++--
>  5 files changed, 34 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/nova-core/driver.rs b/drivers/gpu/nova-core/driver.rs
> index 699e27046c93..fe4eafe1ebf0 100644
> --- a/drivers/gpu/nova-core/driver.rs
> +++ b/drivers/gpu/nova-core/driver.rs
> @@ -74,10 +74,13 @@ pub(crate) struct NovaCore {
>  
>  impl pci::Driver for NovaCore {
>      type IdInfo = ();
> -    type Data = Self;
> +    type Data<'bound> = Self;
>      const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
>  
> -    fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> impl PinInit<Self, Error> {
> +    fn probe<'bound>(
> +        pdev: &'bound pci::Device<Core>,

This is technically incorrect, as the `Device<Core>` only lives as long as the
callback. Having `'bound` would be incorrect.

This can either be addressed via

    pdev: &pci::Device<Core>, pdev_bound: &'bound pci::Device<Bound>, ...

or perhaps by adding a lifetime to `Core<'_>`

    pdev: &'bound pci::Device<Core<'_>>,

Best,
Gary

> +        _info: &'bound Self::IdInfo,
> +    ) -> impl PinInit<Self, Error> + 'bound {
>          pin_init::pin_init_scope(move || {
>              dev_dbg!(pdev, "Probe Nova Core GPU driver.\n");
>  
> @@ -109,7 +112,7 @@ fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> impl PinInit<Self, E
>          })
>      }
>  
> -    fn unbind(pdev: &pci::Device<Core>, this: Pin<&Self>) {
> +    fn unbind<'bound>(pdev: &'bound pci::Device<Core>, this: Pin<&'bound Self>) {
>          this.gpu.unbind(pdev.as_ref());
>      }
>  }
> diff --git a/rust/kernel/pci.rs b/rust/kernel/pci.rs
> index c06ac3fb2a64..8060861199d4 100644
> --- a/rust/kernel/pci.rs
> +++ b/rust/kernel/pci.rs
> @@ -64,7 +64,7 @@
>  // - `DEVICE_DRIVER_OFFSET` is the correct byte offset to the embedded `struct device_driver`.
>  unsafe impl<T: Driver> driver::DriverLayout for Adapter<T> {
>      type DriverType = bindings::pci_driver;
> -    type DriverData<'bound> = T::Data;
> +    type DriverData<'bound> = T::Data<'bound>;
>      const DEVICE_DRIVER_OFFSET: usize = core::mem::offset_of!(Self::DriverType, driver);
>  }
>  
> @@ -130,7 +130,7 @@ extern "C" fn remove_callback(pdev: *mut bindings::pci_dev) {
>          // SAFETY: `remove_callback` is only ever called after a successful call to
>          // `probe_callback`, hence it's guaranteed that `Device::set_drvdata()` has been called
>          // and stored a `Pin<KBox<T::Data>>`.
> -        let data = unsafe { pdev.as_ref().drvdata_borrow::<T::Data>() };
> +        let data = unsafe { pdev.as_ref().drvdata_borrow::<T::Data<'_>>() };
>  
>          T::unbind(pdev, data);
>      }
> @@ -279,13 +279,13 @@ macro_rules! pci_device_table {
>  ///
>  /// impl pci::Driver for MyDriver {
>  ///     type IdInfo = ();
> -///     type Data = Self;
> +///     type Data<'bound> = Self;
>  ///     const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
>  ///
> -///     fn probe(
> -///         _pdev: &pci::Device<Core>,
> -///         _id_info: &Self::IdInfo,
> -///     ) -> impl PinInit<Self, Error> {
> +///     fn probe<'bound>(
> +///         _pdev: &'bound pci::Device<Core>,
> +///         _id_info: &'bound Self::IdInfo,
> +///     ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound {
>  ///         Err(ENODEV)
>  ///     }
>  /// }
> @@ -302,7 +302,7 @@ pub trait Driver: Send {
>      type IdInfo: 'static;
>  
>      /// The type of the driver's bus device private data.
> -    type Data;
> +    type Data<'bound>: 'bound;
>  
>      /// The table of device ids supported by the driver.
>      const ID_TABLE: IdTable<Self::IdInfo>;
> @@ -311,8 +311,10 @@ pub trait Driver: Send {
>      ///
>      /// Called when a new pci device is added or discovered. Implementers should
>      /// attempt to initialize the device here.
> -    fn probe(dev: &Device<device::Core>, id_info: &Self::IdInfo)
> -        -> impl PinInit<Self::Data, Error>;
> +    fn probe<'bound>(
> +        dev: &'bound Device<device::Core>,
> +        id_info: &'bound Self::IdInfo,
> +    ) -> impl PinInit<Self::Data<'bound>, Error> + 'bound;
>  
>      /// PCI driver unbind.
>      ///
> @@ -324,7 +326,7 @@ fn probe(dev: &Device<device::Core>, id_info: &Self::IdInfo)
>      /// operations to gracefully tear down the device.
>      ///
>      /// Otherwise, release operations for driver resources should be performed in `Drop`.
> -    fn unbind(dev: &Device<device::Core>, this: Pin<&Self::Data>) {
> +    fn unbind<'bound>(dev: &'bound Device<device::Core>, this: Pin<&'bound Self::Data<'bound>>) {
>          let _ = (dev, this);
>      }
>  }
> diff --git a/samples/rust/rust_dma.rs b/samples/rust/rust_dma.rs
> index e583c6b8390a..943655a85ec6 100644
> --- a/samples/rust/rust_dma.rs
> +++ b/samples/rust/rust_dma.rs
> @@ -58,10 +58,13 @@ unsafe impl kernel::transmute::FromBytes for MyStruct {}
>  
>  impl pci::Driver for DmaSampleDriver {
>      type IdInfo = ();
> -    type Data = Self;
> +    type Data<'bound> = Self;
>      const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
>  
> -    fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> impl PinInit<Self, Error> {
> +    fn probe<'bound>(
> +        pdev: &'bound pci::Device<Core>,
> +        _info: &'bound Self::IdInfo,
> +    ) -> impl PinInit<Self, Error> + 'bound {
>          pin_init::pin_init_scope(move || {
>              dev_info!(pdev, "Probe DMA test driver.\n");
>  
> diff --git a/samples/rust/rust_driver_auxiliary.rs b/samples/rust/rust_driver_auxiliary.rs
> index 61d5bf2e8c0d..2f57912fe87f 100644
> --- a/samples/rust/rust_driver_auxiliary.rs
> +++ b/samples/rust/rust_driver_auxiliary.rs
> @@ -66,11 +66,14 @@ struct ParentDriver {
>  
>  impl pci::Driver for ParentDriver {
>      type IdInfo = ();
> -    type Data = Self;
> +    type Data<'bound> = Self;
>  
>      const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
>  
> -    fn probe(pdev: &pci::Device<Core>, _info: &Self::IdInfo) -> impl PinInit<Self, Error> {
> +    fn probe<'bound>(
> +        pdev: &'bound pci::Device<Core>,
> +        _info: &'bound Self::IdInfo,
> +    ) -> impl PinInit<Self, Error> + 'bound {
>          Ok(Self {
>              _reg0: auxiliary::Registration::new(
>                  pdev.as_ref(),
> diff --git a/samples/rust/rust_driver_pci.rs b/samples/rust/rust_driver_pci.rs
> index f43c6a660b39..30b9311812f3 100644
> --- a/samples/rust/rust_driver_pci.rs
> +++ b/samples/rust/rust_driver_pci.rs
> @@ -140,11 +140,14 @@ fn config_space(pdev: &pci::Device<Bound>) {
>  
>  impl pci::Driver for SampleDriver {
>      type IdInfo = TestIndex;
> -    type Data = Self;
> +    type Data<'bound> = Self;
>  
>      const ID_TABLE: pci::IdTable<Self::IdInfo> = &PCI_TABLE;
>  
> -    fn probe(pdev: &pci::Device<Core>, info: &Self::IdInfo) -> impl PinInit<Self, Error> {
> +    fn probe<'bound>(
> +        pdev: &'bound pci::Device<Core>,
> +        info: &'bound Self::IdInfo,
> +    ) -> impl PinInit<Self, Error> + 'bound {
>          pin_init::pin_init_scope(move || {
>              let vendor = pdev.vendor_id();
>              dev_dbg!(