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. On top of that, add RegistrationData as a ForLt 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. This series is based on [1]; a branch with all patches can be found in [2]. [1] https://lore.kernel.org/driver-core/[email protected]/ [2] https://git.kernel.org/pub/scm/linux/kernel/git/dakr/linux.git/log/?h=drm-lifetime Changes in v3: - Rename UnbindGuard to RegistrationGuard - RegistrationGuard no longer dereferences to &Device<Bound>; it dereferences to &drm::Device<T, Registered> instead - Drop Registration::new() and rename Registration::new_with_lt() to Registration::new() - Rework DeviceContext typestates: rename Uninit to Normal, restrict AlwaysRefCounted to Normal, establish Deref chain from Registered to Normal - Add AsRef<ParentDevice<Bound>> on Device<T, Registered> for parent device access - Move registration_data_with() from RegistrationGuard to drm::Device<T, Registered> - Ioctl handlers no longer receive &Device<Bound>, only registration data and drm::Device<T, Registered> - Use Device<Registered>::as_ref() to access parent device in nova-drm Changes in v2: - Replace unsafe direct registration data access in ioctl dispatch with safe UnbindGuard::registration_data_with() closure - Eliminate unbind_guard() free function; use type-inference anchor to enable direct dev.unbind_guard() method call in the ioctl macro - UnbindGuard::registration_data_with() provides both parent device and registration data to the closure - Add nova-drm conversion patch demonstrating lifetime-aware registration data with &'bound auxiliary::Device<Bound> - Various safety comment and documentation improvements Danilo Krummrich (13): rust: drm: rename Uninit DeviceContext to Normal rust: drm: Add Driver::ParentDevice associated type rust: drm: change default DeviceContext to Normal rust: drm: restrict AlwaysRefCounted to Normal Device context rust: drm: restrict AlwaysRefCounted to Normal GEM Object context rust: drm: split Deref for Device context typestates rust: drm: return ParentDevice from Device AsRef rust: drm: add AsRef<ParentDevice<Bound>> for Device<Registered> rust: drm: Add RegistrationGuard for drm_dev_enter/exit critical sections rust: drm: Add RegistrationData to drm::Driver rust: drm: Wrap ioctl dispatch in RegistrationGuard rust: drm: Pass registration data to ioctl handlers drm: nova: Use drm::Device<Registered> to access the parent bus device drivers/gpu/drm/nova/driver.rs | 41 ++--- drivers/gpu/drm/nova/file.rs | 18 ++- drivers/gpu/drm/nova/gem.rs | 18 +-- drivers/gpu/drm/tyr/driver.rs | 28 ++-- drivers/gpu/drm/tyr/file.rs | 1 + drivers/gpu/drm/tyr/gem.rs | 11 +- rust/kernel/drm/device.rs | 264 +++++++++++++++++++++++---------- rust/kernel/drm/driver.rs | 129 +++++++++++----- rust/kernel/drm/gem/mod.rs | 98 ++++++------ rust/kernel/drm/gem/shmem.rs | 79 +++++----- rust/kernel/drm/ioctl.rs | 27 +++- rust/kernel/drm/mod.rs | 3 +- 12 files changed, 449 insertions(+), 268 deletions(-) base-commit: 9ece8b7075e983bc01223a4aa1eb1c99285f83ad -- 2.54.0
