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rust: faux: Allow retrieving a bound Device

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When writing up some rust code that used faux devices for unit testing, I
noticed that we never actually added the Bound device context to
faux::Registration's AsRef<device::Device> implementation. This being said:
the Registration object itself is proof that a driver is bound to the
device - so this should be safe.

Signed-off-by: Lyude Paul <lyude@redhat.com>
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Danilo Krummrich <dakr@kernel.org>
Link: https://patch.msgid.link/20260612194436.585385-4-lyude@redhat.com
Signed-off-by: Danilo Krummrich <dakr@kernel.org>
This commit is contained in:
Lyude Paul 2026-06-12 15:43:35 -04:00 committed by Danilo Krummrich
parent 616c229ab0
commit fa8cc4e306
1 changed files with 13 additions and 5 deletions
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18
rust/kernel/faux.rs
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@ -25,7 +25,8 @@
///
/// # Invariants
///
/// `self.0` always holds a valid pointer to an initialized and registered [`struct faux_device`].
/// - `self.0` always holds a valid pointer to an initialized and registered [`struct faux_device`].
/// - This object is proof that the object described by this `Registration` is bound to a device.
///
/// [`struct faux_device`]: srctree/include/linux/device/faux.h
pub struct Registration(NonNull<bindings::faux_device>);
@ -59,10 +60,17 @@ fn as_raw(&self) -> *mut bindings::faux_device {
}
}
impl AsRef<device::Device> for Registration {
fn as_ref(&self) -> &device::Device {
// SAFETY: The underlying `device` in `faux_device` is guaranteed by the C API to be
// a valid initialized `device`.
impl AsRef<device::Device<device::Bound>> for Registration {
fn as_ref(&self) -> &device::Device<device::Bound> {
// SAFETY:
// - The underlying `device` in `faux_device` is guaranteed by the C API to be a valid
// initialized `device`.
// - `faux_match()` always returns 1, and probe runs synchronously
// (PROBE_FORCE_SYNCHRONOUS).
// - `suppress_bind_attrs = true` on faux_driver prevents userspace-triggered unbind via
// sysfs.
// - `mem::forget(Registration)` is not a problem; if the `Registration` is leaked, the faux
// device stays bound forever.
unsafe { device::Device::from_raw(addr_of_mut!((*self.as_raw()).dev)) }
}
}