On Sat, Jun 21, 2025 at 09:43:28PM +0200, Danilo Krummrich wrote:
> Implement generic accessors for the private data of a driver bound to a
> device.
>
> Those accessors should be used by bus abstractions from their
> corresponding core callbacks, such as probe(), remove(), etc.
>
> Implementing them for device::Internal guarantees that driver's can't
> interfere with the logic implemented by the bus abstraction.
>
> Signed-off-by: Danilo Krummrich <dakr@xxxxxxxxxx>
> ---
> rust/helpers/device.c | 10 ++++++++++
> rust/kernel/device.rs | 43 ++++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 52 insertions(+), 1 deletion(-)
>
> diff --git a/rust/helpers/device.c b/rust/helpers/device.c
> index b2135c6686b0..9bf252649c75 100644
> --- a/rust/helpers/device.c
> +++ b/rust/helpers/device.c
> @@ -8,3 +8,13 @@ int rust_helper_devm_add_action(struct device *dev,
> {
> return devm_add_action(dev, action, data);
> }
> +
> +void *rust_helper_dev_get_drvdata(const struct device *dev)
> +{
> + return dev_get_drvdata(dev);
> +}
> +
> +void rust_helper_dev_set_drvdata(struct device *dev, void *data)
> +{
> + dev_set_drvdata(dev, data);
> +}
> diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
> index e9094d8322d5..146eba147d2f 100644
> --- a/rust/kernel/device.rs
> +++ b/rust/kernel/device.rs
> @@ -6,7 +6,7 @@
>
> use crate::{
> bindings,
> - types::{ARef, Opaque},
> + types::{ARef, ForeignOwnable, Opaque},
> };
> use core::{fmt, marker::PhantomData, ptr};
>
> @@ -62,6 +62,47 @@ pub unsafe fn get_device(ptr: *mut bindings::device) -> ARef<Self> {
> }
> }
>
> +impl Device<Internal> {
> + /// Store a pointer to the bound driver's private data.
> + pub fn set_drvdata(&self, data: impl ForeignOwnable) {
> + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`.
> + unsafe { bindings::dev_set_drvdata(self.as_raw(), data.into_foreign().cast()) }
> + }
Ah, but a driver's private data in the device is NOT a bus-specific
thing, it's a driver-specific thing, so your previous patch about
Internal being there for busses feels odd.
> +
> + /// Take ownership of the private data stored in this [`Device`].
> + ///
> + /// # Safety
> + ///
> + /// - Must only be called once after a preceding call to [`Device::set_drvdata`].
> + /// - The type `T` must match the type of the `ForeignOwnable` previously stored by
> + /// [`Device::set_drvdata`].
> + pub unsafe fn drvdata_obtain<T: ForeignOwnable>(&self) -> T {
> + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`.
> + let ptr = unsafe { bindings::dev_get_drvdata(self.as_raw()) };
> +
> + // SAFETY: By the safety requirements of this function, `ptr` comes from a previous call to
> + // `into_foreign()`.
> + unsafe { T::from_foreign(ptr.cast()) }
> + }
> +
> + /// Borrow the driver's private data bound to this [`Device`].
> + ///
> + /// # Safety
> + ///
> + /// - Must only be called after a preceding call to [`Device::set_drvdata`] and before
> + /// [`Device::drvdata_obtain`].
> + /// - The type `T` must match the type of the `ForeignOwnable` previously stored by
> + /// [`Device::set_drvdata`].
> + pub unsafe fn drvdata_borrow<T: ForeignOwnable>(&self) -> T::Borrowed<'_> {
> + // SAFETY: By the type invariants, `self.as_raw()` is a valid pointer to a `struct device`.
> + let ptr = unsafe { bindings::dev_get_drvdata(self.as_raw()) };
> +
> + // SAFETY: By the safety requirements of this function, `ptr` comes from a previous call to
> + // `into_foreign()`.
> + unsafe { T::borrow(ptr.cast()) }
> + }
> +}
Why can't this be part of Core?
thanks,
greg k-h
