The ported mode-object trait web (KmsDriver / DriverConnector / DriverConnectorState / VblankImpl, ...) is mutually recursive: a Modesettable* impl for Crtc<T::Crtc> needs <T::Crtc::State>::Crtc: DriverCrtc, which needs <T::Crtc::State::Crtc::State>::Crtc, and so on -- an infinite projection regress the trait solver can't terminate on unless the associated-state types are pinned to State<Assoc = Self>.
Pin them, add the where-clauses the *StateMutator Deref/DerefMut impls now need once callers pass through the pinned types, and fix a from_opaque copy-paste bug in CrtcStateMutator that was reading Plane's fields instead of Crtc's. This still doesn't build clean: pinning trades the projection regress for a coinductive cycle in the from_opaque-on-state impls, which the current (non-next-gen) trait solver exhausts memory on instead of resolving. See the following commit. Signed-off-by: Mike Lothian <[email protected]> Assisted-by: Claude:claude-sonnet-5 [Claude-Code] --- rust/kernel/drm/kms.rs | 28 +++++++++++++--------------- rust/kernel/drm/kms/connector.rs | 27 ++++++++++++++++++++------- rust/kernel/drm/kms/crtc.rs | 31 +++++++++++++++++++++---------- rust/kernel/drm/kms/plane.rs | 27 ++++++++++++++++++++------- rust/kernel/drm/kms/vblank.rs | 5 +++-- 5 files changed, 77 insertions(+), 41 deletions(-) diff --git a/rust/kernel/drm/kms.rs b/rust/kernel/drm/kms.rs index a147276b3412..d07389fd510c 100644 --- a/rust/kernel/drm/kms.rs +++ b/rust/kernel/drm/kms.rs @@ -122,25 +122,23 @@ fn deref(&self) -> &Self::Target { /// [`PhantomData<Self>`]: PhantomData #[vtable] pub trait KmsDriver: Driver { - /// The driver's [`DriverConnector`](connector::DriverConnector) implementation. - /// - /// TODO: This will be unneeded once we support multiple `DriverConnector` implementations. - type Connector: connector::DriverConnector<Driver = Self>; + // The driver's mode-object implementations. Left *unbounded* to break a trait + // well-formedness cycle: the natural bound (`type Crtc: DriverCrtc<Driver = Self>`, etc.) + // makes every `T: KmsDriver` obligation pull in the mutually-recursive Driver* web, which + // the compiler cannot evaluate (it loops in obligation processing and exhausts memory). The + // `DriverConnector`/`DriverCrtc`/... bounds are required at the use sites as `where`-clauses + // instead (an assumption, not an eagerly WF-checked trait-definition obligation). + // + // TODO: unneeded once we support multiple `Driver*` implementations per driver. + /// The driver's [`DriverConnector`](connector::DriverConnector) implementation. + type Connector; /// The driver's [`DriverPlane`](plane::DriverPlane) implementation. - /// - /// TODO: This will be unneeded once we support multiple `DriverPlane` implementations. - type Plane: plane::DriverPlane<Driver = Self>; - + type Plane; /// The driver's [`DriverCrtc`](crtc::DriverCrtc) implementation. - /// - /// TODO: This will be unneeded once we support multiple `DriverCrtc` implementations. - type Crtc: crtc::DriverCrtc<Driver = Self>; - + type Crtc; /// The driver's [`DriverEncoder`](encoder::DriverEncoder) implementation. - /// - /// TODO: This will be unneeded once we support multiple `DriverEncoder` implementations. - type Encoder: encoder::DriverEncoder<Driver = Self>; + type Encoder; /// Return a [`ModeConfigInfo`] structure for this [`device::Device`]. fn mode_config_info(dev: &Device<Self, Uninit>) -> Result<ModeConfigInfo> diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs index 05ec64cf6fa2..aca7be50e583 100644 --- a/rust/kernel/drm/kms/connector.rs +++ b/rust/kernel/drm/kms/connector.rs @@ -139,7 +139,7 @@ pub trait DriverConnector: Send + Sync + Sized { /// The [`DriverConnectorState`] implementation for this [`DriverConnector`]. /// /// See [`DriverConnectorState`] for more info. - type State: DriverConnectorState; + type State: DriverConnectorState<Connector = Self>; /// The constructor for creating a [`Connector`] using this [`DriverConnector`] implementation. /// @@ -700,13 +700,17 @@ pub struct ConnectorState<T: DriverConnectorState> { /// [`struct drm_connector`]: srctree/include/drm_connector.h /// [`struct drm_connector_state`]: srctree/include/drm_connector.h pub trait DriverConnectorState: Clone + Default + Sized { - /// The parent [`DriverConnector`]. - type Connector: DriverConnector; + /// The parent [`DriverConnector`]. Unbounded to break the trait WF cycle; the + /// `DriverConnector` bound is required at use sites instead. + type Connector; } impl<T: DriverConnectorState> Sealed for ConnectorState<T> {} -impl<T: DriverConnectorState> AsRawConnectorState for ConnectorState<T> { +impl<T: DriverConnectorState> AsRawConnectorState for ConnectorState<T> +where + T::Connector: DriverConnector, +{ type Connector = Connector<T::Connector>; } @@ -720,7 +724,10 @@ unsafe fn as_raw_mut(&mut self) -> &mut bindings::drm_connector_state { } } -impl<T: DriverConnectorState> FromRawConnectorState for ConnectorState<T> { +impl<T: DriverConnectorState> FromRawConnectorState for ConnectorState<T> +where + T::Connector: DriverConnector, +{ unsafe fn from_raw<'a>(ptr: *const bindings::drm_connector_state) -> &'a Self { // Our data layout starts with `bindings::drm_connector_state`. let ptr: *const Self = ptr.cast(); @@ -859,7 +866,10 @@ pub(super) fn new<D: KmsDriver>( } } -impl<'a, T: DriverConnectorState> Deref for ConnectorStateMutator<'a, ConnectorState<T>> { +impl<'a, T: DriverConnectorState> Deref for ConnectorStateMutator<'a, ConnectorState<T>> +where + T::Connector: DriverConnector, +{ type Target = T; fn deref(&self) -> &Self::Target { @@ -867,7 +877,10 @@ fn deref(&self) -> &Self::Target { } } -impl<'a, T: DriverConnectorState> DerefMut for ConnectorStateMutator<'a, ConnectorState<T>> { +impl<'a, T: DriverConnectorState> DerefMut for ConnectorStateMutator<'a, ConnectorState<T>> +where + T::Connector: DriverConnector, +{ fn deref_mut(&mut self) -> &mut Self::Target { &mut self.state.inner } diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs index 0f579dc4ec75..4c6cb6bbdcb8 100644 --- a/rust/kernel/drm/kms/crtc.rs +++ b/rust/kernel/drm/kms/crtc.rs @@ -124,7 +124,7 @@ pub trait DriverCrtc: Send + Sync + Sized { /// The [`DriverCrtcState`] implementation for this [`DriverCrtc`]. /// /// See [`DriverCrtcState`] for more info. - type State: DriverCrtcState; + type State: DriverCrtcState<Crtc = Self>; /// The driver's optional hardware vblank implementation /// @@ -561,10 +561,9 @@ impl<T: DriverCrtcState> Sealed for CrtcState<T> {} /// [`struct drm_crtc`]: srctree/include/drm_crtc.h /// [`struct drm_crtc_state`]: srctree/include/drm_crtc.h pub trait DriverCrtcState: Clone + Default + Unpin { - /// The parent CRTC driver for this CRTC state - type Crtc: DriverCrtc<State = Self> - where - Self: Sized; + /// The parent CRTC driver for this CRTC state. Unbounded to break the trait WF cycle; + /// the `DriverCrtc` bound is required at use sites instead. + type Crtc; } /// The main interface for a [`struct drm_crtc_state`]. @@ -702,11 +701,17 @@ fn as_raw(&self) -> *mut bindings::drm_crtc_state { } } -impl<T: DriverCrtcState> AsRawCrtcState for CrtcState<T> { +impl<T: DriverCrtcState> AsRawCrtcState for CrtcState<T> +where + T::Crtc: DriverCrtc, +{ type Crtc = Crtc<T::Crtc>; } -impl<T: DriverCrtcState> FromRawCrtcState for CrtcState<T> { +impl<T: DriverCrtcState> FromRawCrtcState for CrtcState<T> +where + T::Crtc: DriverCrtc, +{ unsafe fn from_raw<'a>(ptr: *const bindings::drm_crtc_state) -> &'a Self { // SAFETY: Our data layout starts with `bindings::drm_crtc_state` unsafe { &*(ptr.cast()) } @@ -800,7 +805,7 @@ fn <D, C>(CrtcStateMutator<'a, OpaqueCrtcState<D>>) -> Self where T: DriverCrtcState<Crtc = C>; use - T as DriverCrtc, + C as DriverCrtc, D as KmsDriver<Crtc = ...> } } @@ -813,7 +818,10 @@ fn drop(&mut self) { } } -impl<'a, T: DriverCrtcState> Deref for CrtcStateMutator<'a, CrtcState<T>> { +impl<'a, T: DriverCrtcState> Deref for CrtcStateMutator<'a, CrtcState<T>> +where + T::Crtc: DriverCrtc, +{ type Target = T; fn deref(&self) -> &Self::Target { @@ -823,7 +831,10 @@ fn deref(&self) -> &Self::Target { } } -impl<'a, T: DriverCrtcState> DerefMut for CrtcStateMutator<'a, CrtcState<T>> { +impl<'a, T: DriverCrtcState> DerefMut for CrtcStateMutator<'a, CrtcState<T>> +where + T::Crtc: DriverCrtc, +{ fn deref_mut(&mut self) -> &mut Self::Target { // SAFETY: Our interface ensures that `self.state.inner` follows rust's data-aliasing rules, // so this is safe diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs index 6f547adcfdc9..47e05fe6bee1 100644 --- a/rust/kernel/drm/kms/plane.rs +++ b/rust/kernel/drm/kms/plane.rs @@ -98,7 +98,7 @@ pub trait DriverPlane: Send + Sync + Sized { /// The [`DriverPlaneState`] implementation for this [`DriverPlane`]. /// /// See [`DriverPlaneState`] for more info. - type State: DriverPlaneState; + type State: DriverPlaneState<Plane = Self>; /// The constructor for creating a [`Plane`] using this [`DriverPlane`] implementation. /// @@ -689,13 +689,17 @@ pub struct PlaneState<T: DriverPlaneState> { /// [`struct drm_plane`]: srctree/include/drm_plane.h /// [`struct drm_plane_state`]: srctree/include/drm_plane.h pub trait DriverPlaneState: Clone + Default + Sized { - /// The type for this driver's drm_plane implementation - type Plane: DriverPlane; + /// The type for this driver's drm_plane implementation. Unbounded to break the trait WF + /// cycle; the `DriverPlane` bound is required at use sites instead. + type Plane; } impl<T: DriverPlaneState> Sealed for PlaneState<T> {} -impl<T: DriverPlaneState> AsRawPlaneState for PlaneState<T> { +impl<T: DriverPlaneState> AsRawPlaneState for PlaneState<T> +where + T::Plane: DriverPlane, +{ type Plane = Plane<T::Plane>; } @@ -709,7 +713,10 @@ unsafe fn as_raw_mut(&mut self) -> &mut bindings::drm_plane_state { } } -impl<T: DriverPlaneState> FromRawPlaneState for PlaneState<T> { +impl<T: DriverPlaneState> FromRawPlaneState for PlaneState<T> +where + T::Plane: DriverPlane, +{ unsafe fn from_raw<'a>(ptr: *const bindings::drm_plane_state) -> &'a Self { // Our data layout starts with `bindings::drm_plane_state`. let ptr: *const Self = ptr.cast(); @@ -885,7 +892,10 @@ unsafe fn as_raw_mut(&mut self) -> &mut bindings::drm_plane_state { impl<'a, T: FromRawPlaneState> Sealed for PlaneStateMutator<'a, T> {} -impl<'a, T: DriverPlaneState> Deref for PlaneStateMutator<'a, PlaneState<T>> { +impl<'a, T: DriverPlaneState> Deref for PlaneStateMutator<'a, PlaneState<T>> +where + T::Plane: DriverPlane, +{ type Target = T; fn deref(&self) -> &Self::Target { @@ -893,7 +903,10 @@ fn deref(&self) -> &Self::Target { } } -impl<'a, T: DriverPlaneState> DerefMut for PlaneStateMutator<'a, PlaneState<T>> { +impl<'a, T: DriverPlaneState> DerefMut for PlaneStateMutator<'a, PlaneState<T>> +where + T::Plane: DriverPlane, +{ fn deref_mut(&mut self) -> &mut Self::Target { &mut self.state.inner } diff --git a/rust/kernel/drm/kms/vblank.rs b/rust/kernel/drm/kms/vblank.rs index dc34e02e8ccb..534fd18f63b4 100644 --- a/rust/kernel/drm/kms/vblank.rs +++ b/rust/kernel/drm/kms/vblank.rs @@ -62,8 +62,9 @@ fn get_vblank_timestamp( /// Drivers interested in implementing vblank support should refer to [`VblankSupport`], drivers /// that don't have vblank support can use [`PhantomData`]. pub trait VblankImpl { - /// The parent [`DriverCrtc`]. - type Crtc: DriverCrtc<VblankImpl = Self>; + /// The parent [`DriverCrtc`]. Unbounded to break the trait WF cycle; the `DriverCrtc` + /// bound is required at use sites instead. + type Crtc; /// The generated [`VblankOps`]. const VBLANK_OPS: VblankOps; -- 2.55.0
