I mentioned this already to Danilo via alternate channels, but to clarify - this patch -is- actually needed, as we make use of `AsRef<Device<Bound>>` in the kunit test for SGTable
On Thu, 2026-06-04 at 15:25 +0200, Danilo Krummrich wrote: > On Wed Jun 3, 2026 at 9:42 PM CEST, Lyude Paul wrote: > > 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. > > Yes, it should be, but the reasons are non-trivial and should be part > of the > safety comment below. > > - 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 > > > Signed-off-by: Lyude Paul <[email protected]> > > I can pick this through the driver-core tree already, as it seems > this it not > needed by this series. Feel free to resend as individual patch for > thus purpose. > > > --- > > rust/kernel/faux.rs | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/rust/kernel/faux.rs b/rust/kernel/faux.rs > > index 43b4974f48cd2..e0856b2964a2c 100644 > > --- a/rust/kernel/faux.rs > > +++ b/rust/kernel/faux.rs > > @@ -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>); > > @@ -59,8 +60,8 @@ fn as_raw(&self) -> *mut bindings::faux_device { > > } > > } > > > > -impl AsRef<device::Device> for Registration { > > - fn as_ref(&self) -> &device::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`. > > unsafe { > > device::Device::from_raw(addr_of_mut!((*self.as_raw()).dev)) } > > -- > > 2.54.0
