Merge patch series "rust: drm: Higher-Ranked Lifetime private data"

Danilo Krummrich <dakr@kernel.org> says:

DRM ioctls run in process context without any guarantee that the parent
bus device is still bound. This series solves the problem by introducing
RegistrationGuard -- a guard representing a drm_dev_enter/exit SRCU
critical section that proves the parent bus device is bound for the
lifetime of the guard.

As initial plumbing for this, the DRM DeviceContext typestates are
reworked: Uninit is renamed to Normal, defaults are adjusted,
AlwaysRefCounted is restricted to Normal, and a Deref chain from
Device<T, Registered> to Device<T, Normal> is established. This gives
Device<T, Registered> the semantic that the device is currently
registered and the parent bus device is bound, which makes the
RegistrationGuard and ioctl dispatch much cleaner. An Ioctl context
restricts registration_guard() to ioctl dispatch, where the DRM core
guarantees prior registration.

On top of that, add RegistrationData as a GAT (Generic Associated Type)
on drm::Driver, allowing drivers to store data whose lifetime is tied to
the parent bus device binding scope. The data is allocated in
Registration::new(), lifetime-erased to 'static for storage, and made
accessible through Device<T, Registered>::registration_data_with(). The
closure's HRTB ties the lifetime to the closure scope; internally the
'static pointer is cast back to the closure-scoped lifetime. The
reference is valid for the duration of the drm_dev_enter/exit critical
section held by RegistrationGuard.

Also update the ioctl dispatch macro to wrap every handler in a
RegistrationGuard, returning ENODEV if the device has been unplugged,
and pass the registration data to handlers.

Link: https://patch.msgid.link/20260628145406.2107056-1-dakr@kernel.org
Signed-off-by: Danilo Krummrich <dakr@kernel.org>

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