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Message-ID: <20240930233257.1189730-21-lyude@redhat.com>
Date: Mon, 30 Sep 2024 19:10:03 -0400
From: Lyude Paul <lyude@...hat.com>
To: dri-devel@...ts.freedesktop.org,
rust-for-linux@...r.kernel.org
Cc: Asahi Lina <lina@...hilina.net>,
Danilo Krummrich <dakr@...nel.org>,
mcanal@...lia.com,
airlied@...hat.com,
zhiw@...dia.com,
cjia@...dia.com,
jhubbard@...dia.com,
Miguel Ojeda <ojeda@...nel.org>,
Alex Gaynor <alex.gaynor@...il.com>,
Wedson Almeida Filho <wedsonaf@...il.com>,
Boqun Feng <boqun.feng@...il.com>,
Gary Guo <gary@...yguo.net>,
Björn Roy Baron <bjorn3_gh@...tonmail.com>,
Benno Lossin <benno.lossin@...ton.me>,
Andreas Hindborg <a.hindborg@...sung.com>,
Alice Ryhl <aliceryhl@...gle.com>,
Trevor Gross <tmgross@...ch.edu>,
linux-kernel@...r.kernel.org (open list)
Subject: [WIP RFC v2 20/35] WIP: rust: drm/kms: Add drm_atomic_state bindings
Next up is introducing bindings that we can use to represent the global DRM
atomic state, along with all of the various object states contained within.
We do this by introducing a few new concepts: borrowed states, atomic state
mutators, and atomic state composers.
To understand these, we need to quickly touch upon the general life of an
atomic commit. Assuming a driver does its own internal atomic commit, the
procedure looks something like this:
* Allocate a new atomic state
* Duplicate the atomic state of each mode object we want to mutate, and add
the duplicated state to the new atomic state
* Check (possibly more then once) the atomic state, possibly modifying it
along the way
* Commit the atomic state to software (we'll call this commit time). At
this point no new objects can be added to the state
* Finish committing the atomic state to hardware asynchronously
With this in mind, we introduce AtomicStateMutator and AtomicStateComposer
(along with leaky variants intended for uses in FFI calls). An
AtomicStateMutator allows mutating an atomic state but does not allow for
adding new objects to the state. Subsequently, an AtomicStateComposer
allows for both mutating an atomic state and adding new mode objects. We
control when we expose each of these types in order to implement the
limitations required by the aforementioned example.
Note as well that AtomicStateComposer is intended to eventually be usable
directly by drivers. In this scenario, a driver will be able to create an
AtomicStateComposer (the equivalent of allocating an atomic state in C) and
then commit it by passing it to our DRM bindings by-value, insuring that
once the commit process begins it is impossible to keep using the
AtomicStateComposer.
The next part of this is allowing users to modify the atomic states of all
of the objects contained within an atomic state. Since it's an extremely
common usecase for objects to mutate the atomic state of multiple objects
at once in an unpredictable order, we need a mechanism that will allow us
to hand out &mut references to each state while ensuring at runtime that we
do not break rust's data aliasing rules (which disallow us from ever having
more then one &mut reference to the same piece of data).
We do this by introducing the concept of a "borrowed" state. This is a very
similar concept to RefCell, where it is ensured during runtime that when a
&mut reference is taken out another one cannot be created until the
corresponding Ref object has been dropped. Our equivalent Ref types are
BorrowedConnectorState, BorrowedCrtcState, and BorrowedPlaneState.
Each one of these types can be used in the same manner as a Ref - no
additional borrows for an atomic state may be taken until the existing one
has been dropped. Subsequently, all of these types implement their
respective AsRaw* and FromRaw* counter-parts - and allow dereferencing to
each driver-private data structure for fully qualified borrows (like
BorrowedCrtcState<'a, CrtcState<T>>. This allows a pretty clean way of
mutating multiple states at once without ever breaking rust's mutability
rules.
We'll use all of these types over the next few commits to begin introducing
various atomic modeset callbacks to each mode object type.
Signed-off-by: Lyude Paul <lyude@...hat.com>
---
TODO:
* Finish adding state iterators
We only have one iterator for planes right now, but the plan is to have
iterators for all types and have two different kind of iterators:
* State object iterators
Basically, these just iterate through all of the mode objects of a
specific type present in an atomic state. Currently this is what our
plane iterator does.
* State mutator iterators
With the existence of AtomicStateMutator and friends, it makes sense to
have a type of iterator that:
* Only iterates through unborrowed atomic states, removing the need to
deal with the Option<> that get_new_*_state() functions return
* Returns each (object, old_state, new_state) triplet as a dedicated
type (PlaneUpdate, CrtcUpdate, ConnectorUpdate) that can be upcasted
from an Opaque type using a single call. This is desirable, as it
would make iterating through objects with a specific Driver*
implementation as easy as just adding a .filter_map() call to the
iterator.
* Upcast functions for the Borrowed* types
Signed-off-by: Lyude Paul <lyude@...hat.com>
---
rust/helpers/drm/atomic.c | 32 +++
rust/helpers/drm/drm.c | 3 +
rust/kernel/drm/kms.rs | 9 +
rust/kernel/drm/kms/atomic.rs | 419 +++++++++++++++++++++++++++++++
rust/kernel/drm/kms/connector.rs | 75 ++++++
rust/kernel/drm/kms/crtc.rs | 75 ++++++
rust/kernel/drm/kms/plane.rs | 77 ++++++
7 files changed, 690 insertions(+)
create mode 100644 rust/helpers/drm/atomic.c
create mode 100644 rust/kernel/drm/kms/atomic.rs
diff --git a/rust/helpers/drm/atomic.c b/rust/helpers/drm/atomic.c
new file mode 100644
index 0000000000000..fff70053f6943
--- /dev/null
+++ b/rust/helpers/drm/atomic.c
@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <drm/drm_atomic.h>
+
+void rust_helper_drm_atomic_state_get(struct drm_atomic_state *state)
+{
+ drm_atomic_state_get(state);
+}
+
+void rust_helper_drm_atomic_state_put(struct drm_atomic_state *state)
+{
+ drm_atomic_state_put(state);
+}
+
+// Macros for generating one repetitive atomic state accessors (like drm_atomic_get_new_plane_state)
+#define STATE_FUNC(type, tense) \
+ struct drm_ ## type ## _state *rust_helper_drm_atomic_get_ ## tense ## _ ## type ## _state( \
+ const struct drm_atomic_state *state, \
+ struct drm_ ## type *type \
+ ) { \
+ return drm_atomic_get_## tense ## _ ## type ## _state(state, type); \
+ }
+#define STATE_FUNCS(type) \
+ STATE_FUNC(type, new); \
+ STATE_FUNC(type, old);
+
+STATE_FUNCS(plane);
+STATE_FUNCS(crtc);
+STATE_FUNCS(connector);
+
+#undef STATE_FUNCS
+#undef STATE_FUNC
diff --git a/rust/helpers/drm/drm.c b/rust/helpers/drm/drm.c
index 028b8ab429572..365f6807774d4 100644
--- a/rust/helpers/drm/drm.c
+++ b/rust/helpers/drm/drm.c
@@ -1,5 +1,8 @@
// SPDX-License-Identifier: GPL-2.0
+#ifdef CONFIG_DRM_KMS_HELPER
+#include "atomic.c"
+#endif
#include "gem.c"
#ifdef CONFIG_DRM_GEM_SHMEM_HELPER
#include "gem_shmem_helper.c"
diff --git a/rust/kernel/drm/kms.rs b/rust/kernel/drm/kms.rs
index d74267c78864f..4ab039d67352e 100644
--- a/rust/kernel/drm/kms.rs
+++ b/rust/kernel/drm/kms.rs
@@ -2,6 +2,7 @@
//! KMS driver abstractions for rust.
+pub mod atomic;
pub mod connector;
pub mod crtc;
pub mod encoder;
@@ -248,6 +249,14 @@ pub(crate) fn mode_config_mutex(&self) -> &Mutex<()> {
pub fn mode_config_lock(&self) -> ModeConfigGuard<'_, T> {
ModeConfigGuard(self.mode_config_mutex().lock(), PhantomData)
}
+
+ /// Return the number of registered [`Plane`](plane::Plane) objects on this [`Device`].
+ #[inline]
+ pub fn num_plane(&self) -> i32 {
+ // SAFETY: The only context which this could change is before registration, which must be
+ // single-threaded anyway - so it's safe to just read this value
+ unsafe { (*self.as_raw()).mode_config.num_total_plane }
+ }
}
/// A modesetting object in DRM.
diff --git a/rust/kernel/drm/kms/atomic.rs b/rust/kernel/drm/kms/atomic.rs
new file mode 100644
index 0000000000000..a4354b89b07cc
--- /dev/null
+++ b/rust/kernel/drm/kms/atomic.rs
@@ -0,0 +1,419 @@
+// SPDX-License-Identifier: GPL-2.0 OR MIT
+
+//! [`struct drm_atomic_state`] related bindings for rust.
+//!
+//! [`struct drm_atomic_state`]: srctree/include/drm/drm_atomic.h
+use alloc::boxed::Box;
+use crate::{
+ bindings,
+ drm::{device::Device, drv::Driver},
+ types::*,
+ error::{from_err_ptr, to_result, from_result},
+ init::Zeroable,
+ prelude::*,
+ private::Sealed
+};
+use core::{
+ marker::*,
+ ptr::NonNull,
+ cell::Cell,
+ ffi::*,
+ slice,
+ ops::*,
+ mem::ManuallyDrop,
+ iter::Iterator,
+};
+use super::{
+ crtc::*,
+ connector::*,
+ plane::*,
+ Kms,
+ KmsDriver,
+ ModeObject
+};
+
+/// The main wrapper around [`struct drm_atomic_state`].
+///
+/// This type is usually embedded within another interface such as an [`AtomicStateMutator`].
+///
+/// # Invariants
+///
+/// - The data layout of this type is identical to [`struct drm_atomic_state`].
+/// - `state` is initialized for as long as this type is exposed to users.
+///
+/// [`struct drm_atomic_state`]: srctree/include/drm/drm_atomic.h
+#[repr(transparent)]
+pub struct AtomicState<T: KmsDriver> {
+ pub(super) state: Opaque<bindings::drm_atomic_state>,
+ _p: PhantomData<T>,
+}
+
+impl<T: KmsDriver> AtomicState<T> {
+ /// Reconstruct an immutable reference to an atomic state from the given pointer
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must point to a valid initialized instance of [`struct drm_atomic_state`].
+ ///
+ /// [`struct drm_atomic_state`]: srctree/include/drm/drm_atomic.h
+ pub(super) unsafe fn from_raw<'a>(ptr: *const bindings::drm_atomic_state) -> &'a Self {
+ // SAFETY: Our data layout is identical
+ unsafe { &*ptr.cast() }
+ }
+
+ pub(crate) fn as_raw(&self) -> *mut bindings::drm_atomic_state {
+ self.state.get()
+ }
+
+ /// Return the [`Device`] associated with this [`AtomicState`].
+ pub fn drm_dev(&self) -> &Device<T> {
+ // SAFETY:
+ // * `state` is initialized via our type invariants.
+ // * `dev` is invariant throughout the lifetime of `AtomicState`
+ unsafe { Device::borrow((*self.state.get()).dev) }
+ }
+
+ /// Return the old atomic state for `crtc`, if it is present within this [`AtomicState`].
+ pub fn get_old_crtc_state<C>(&self, crtc: &C) -> Option<&C::State>
+ where
+ C: AsRawCrtc<Driver = T>,
+ {
+ // SAFETY: This function either returns NULL or a valid pointer to a `drm_crtc_state`
+ unsafe {
+ bindings::drm_atomic_get_old_crtc_state(
+ self.as_raw(),
+ crtc.as_raw()
+ ).as_ref().map(|p| unsafe { C::State::from_raw(p) })
+ }
+ }
+
+ /// Return the old atomic state for `plane`, if it is present within this [`AtomicState`].
+ pub fn get_old_plane_state<P>(&self, plane: &P) -> Option<&P::State>
+ where
+ P: AsRawPlane<Driver = T>,
+ {
+ // SAFETY: This function either returns NULL or a valid pointer to a `drm_plane_state`
+ unsafe {
+ bindings::drm_atomic_get_old_plane_state(
+ self.as_raw(),
+ plane.as_raw()
+ ).as_ref().map(|p| unsafe { P::State::from_raw(p) })
+ }
+ }
+
+ /// Return the old atomic state for `connector` if it is present within this [`AtomicState`].
+ pub fn get_old_connector_state<C>(&self, connector: &C) -> Option<&C::State>
+ where
+ C: AsRawConnector<Driver = T>
+ {
+ // SAFETY: THis function either returns NULL or a valid pointer to a `drm_connector_state`.
+ unsafe {
+ bindings::drm_atomic_get_old_connector_state(
+ self.as_raw(),
+ connector.as_raw()
+ ).as_ref().map(|p| unsafe { C::State::from_raw(p) })
+ }
+ }
+}
+
+// SAFETY: DRM atomic state objects are always reference counted and the get/put functions satisfy
+// the requirements.
+unsafe impl<T: KmsDriver> AlwaysRefCounted for AtomicState<T> {
+ fn inc_ref(&self) {
+ // SAFETY: FFI call with no special requirements
+ unsafe { bindings::drm_atomic_state_get(self.state.get()) }
+ }
+
+ unsafe fn dec_ref(obj: NonNull<Self>) {
+ // SAFETY: FFI calls with no special requirements
+ unsafe { bindings::drm_atomic_state_put(obj.as_ptr().cast()) }
+ }
+}
+
+/// A smart-pointer for modifying the contents of an atomic state.
+///
+/// As it's not unreasonable for a modesetting driver to want to have references to the state of
+/// multiple modesetting objects at once, along with mutating multiple states for unique modesetting
+/// objects at once, this type provides a mechanism for safely doing both of these things.
+///
+/// To honor Rust's aliasing rules regarding mutable references, this structure ensures only one
+/// mutable reference to a mode object's atomic state may exist at a time - and refuses to provide
+/// another if one has already been taken out using runtime checks.
+pub struct AtomicStateMutator<T: KmsDriver> {
+ /// The state being mutated. Note that the use of `ManuallyDrop` here is because mutators are
+ /// only constructed in FFI callbacks and thus borrow their references to the atomic state from
+ /// DRM. Composers, which make use of mutators internally, can potentially be owned by rust code
+ /// if a driver is performing an atomic commit internally - and thus will call the drop
+ /// implementation here.
+ state: ManuallyDrop<ARef<AtomicState<T>>>,
+
+ /// Bitmask of borrowed CRTC state objects
+ pub(super) borrowed_crtcs: Cell<u32>,
+ /// Bitmask of borrowed plane state objects
+ pub(super) borrowed_planes: Cell<u32>,
+ /// Bitmask of borrowed connector state objects
+ pub(super) borrowed_connectors: Cell<u32>,
+}
+
+impl<T: KmsDriver> AtomicStateMutator<T> {
+ /// Construct a new [`AtomicStateMutator`]
+ ///
+ /// # Safety
+ ///
+ /// `ptr` must point to a valid `drm_atomic_state`
+ pub(super) unsafe fn new(ptr: NonNull<bindings::drm_atomic_state>) -> Self {
+ Self {
+ // SAFETY: The data layout of `AtomicState<T>` is identical to drm_atomic_state
+ state: ManuallyDrop::new(unsafe { ARef::from_raw(ptr.cast()) }),
+ borrowed_planes: Cell::default(),
+ borrowed_crtcs: Cell::default(),
+ borrowed_connectors: Cell::default(),
+ }
+ }
+
+ pub(crate) fn as_raw(&self) -> *mut bindings::drm_atomic_state {
+ self.state.as_raw()
+ }
+
+ /// Return the [`Device`] for this [`AtomicStateMutator`]
+ pub fn drm_dev(&self) -> &Device<T> {
+ self.state.drm_dev()
+ }
+
+ /// Retrieve the last committed atomic state for `crtc` if `crtc` has already been added to the
+ /// atomic state being composed.
+ ///
+ /// Returns `None` otherwise.
+ pub fn get_old_crtc_state<C>(&self, crtc: &C) -> Option<&C::State>
+ where
+ C: AsRawCrtc<Driver = T>
+ {
+ self.state.get_old_crtc_state(crtc)
+ }
+
+ /// Retrieve the last committed atomic state for `connector` if `connector` has already been
+ /// added to the atomic state being composed.
+ ///
+ /// Returns `None` otherwise.
+ pub fn get_old_connector_state<C>(&self, connector: &C) -> Option<&C::State>
+ where
+ C: AsRawConnector<Driver = T>
+ {
+ self.state.get_old_connector_state(connector)
+ }
+
+ /// Retrieve the last committed atomic state for `plane` if `plane` has already been added to
+ /// the atomic state being composed.
+ ///
+ /// Returns `None` otherwise.
+ pub fn get_old_plane_state<P>(&self, plane: &P) -> Option<&P::State>
+ where
+ P: AsRawPlane<Driver = T>,
+ {
+ self.state.get_old_plane_state(plane)
+ }
+
+ /// Return a composer for `plane`s new atomic state if it was previously added to the atomic
+ /// state being composed.
+ ///
+ /// Returns `None` otherwise, or if a composer still exists for this state.
+ pub fn get_new_crtc_state<C>(&self, crtc: &C) -> Option<BorrowedCrtcState<'_, C::State>>
+ where
+ C: AsRawCrtc<Driver = T>
+ {
+ // SAFETY: DRM either returns NULL or a valid pointer to a `drm_crtc_state`
+ let state = unsafe {
+ bindings::drm_atomic_get_new_crtc_state(self.as_raw(), crtc.as_raw())
+ };
+
+ BorrowedCrtcState::<C::State>::new(self, NonNull::new(state)?)
+ }
+
+ /// Return a composer for `plane`s new atomic state if it was previously added to the atomic
+ /// state being composed.
+ ///
+ /// Returns `None` otherwise, or if a composer still exists for this state.
+ pub fn get_new_plane_state<P>(&self, plane: &P) -> Option<BorrowedPlaneState<'_, P::State>>
+ where
+ P: AsRawPlane<Driver = T>,
+ {
+ // SAFETY: DRM either returns NULL or a valid pointer to a `drm_plane_state`.
+ let state = unsafe {
+ bindings::drm_atomic_get_new_plane_state(self.as_raw(), plane.as_raw())
+ };
+
+ BorrowedPlaneState::<P::State>::new(self, NonNull::new(state)?)
+ }
+
+ /// Return a composer for `crtc`s new atomic state if it was previously added to the atomic
+ /// state being composed.
+ ///
+ /// Returns `None` otherwise, or if a composer still exists for this state.
+ pub fn get_new_connector_state<C>(
+ &self,
+ connector: &C
+ ) -> Option<BorrowedConnectorState<'_, C::State>>
+ where
+ C: AsRawConnector<Driver = T>,
+ {
+ // SAFETY: DRM either returns NULL or a valid pointer to a `drm_connector_state`
+ let state = unsafe {
+ bindings::drm_atomic_get_new_connector_state(self.as_raw(), connector.as_raw())
+ };
+
+ BorrowedConnectorState::<C::State>::new(self, NonNull::new(state)?)
+ }
+
+ /// Iterate through each of the planes (regardless of type) currently in this atomic state.
+ pub fn iter_planes(&self) -> AtomicStatePlaneIter<'_, T> {
+ AtomicStatePlaneIter::new(&self.state)
+ }
+}
+
+/// An [`AtomicStateMutator`] wrapper which is not yet part of any commit operation.
+///
+/// Since it's not yet part of a commit operation, new mode objects may be added to the state. It
+/// also holds a reference to the underlying [`AtomicState`] that will be released when this object
+/// is dropped.
+pub struct AtomicStateComposer<T: KmsDriver>(AtomicStateMutator<T>);
+
+impl<T: KmsDriver> Deref for AtomicStateComposer<T> {
+ type Target = AtomicStateMutator<T>;
+
+ fn deref(&self) -> &Self::Target {
+ &self.0
+ }
+}
+
+impl<T: KmsDriver> Drop for AtomicStateComposer<T> {
+ fn drop(&mut self) {
+ // SAFETY: We're in drop, so this is guaranteed to be the last possible reference
+ unsafe { ManuallyDrop::drop(&mut self.0.state) }
+ }
+}
+
+impl<T: KmsDriver> AtomicStateComposer<T> {
+ /// # Safety
+ ///
+ /// The caller guarantees that `ptr` points to a valid instance of `drm_atomic_state`.
+ pub(crate) unsafe fn new(ptr: NonNull<bindings::drm_atomic_state>) -> Self {
+ // SAFETY: see `AtomicStateMutator::from_raw()`
+ Self(unsafe { AtomicStateMutator::new(ptr) })
+ }
+
+ /// Attempt to add the state for `crtc` to the atomic state for this composer if it hasn't
+ /// already been added, and create a mutator for it.
+ ///
+ /// If a composer already exists for this `crtc`, this function returns `Error(EBUSY)`. If
+ /// attempting to add the state fails, another error code will be returned.
+ pub fn add_crtc_state<C>(&self, crtc: &C) -> Result<BorrowedCrtcState<'_, C::State>>
+ where
+ C: AsRawCrtc<Driver = T>
+ {
+ // SAFETY: DRM will only return a valid pointer to a [`drm_crtc_state`] - or an error.
+ let state = unsafe {
+ from_err_ptr(
+ bindings::drm_atomic_get_crtc_state(self.as_raw(), crtc.as_raw())
+ ).map(|c| NonNull::new_unchecked(c))
+ }?;
+
+ BorrowedCrtcState::<C::State>::new(self, state).ok_or(EBUSY)
+ }
+
+ /// Attempt to add the state for `plane` to the atomic state for this composer if it hasn't
+ /// already been added, and create a mutator for it.
+ ///
+ /// If a composer already exists for this `plane`, this function returns `Error(EBUSY)`. If
+ /// attempting to add the state fails, another error code will be returned.
+ pub fn add_plane_state<P>(&self, plane: &P) -> Result<BorrowedPlaneState<'_, P::State>>
+ where
+ P: AsRawPlane<Driver = T>,
+ {
+ // SAFETY: DRM will only return a valid pointer to a [`drm_plane_state`] - or an error.
+ let state = unsafe {
+ from_err_ptr(
+ bindings::drm_atomic_get_plane_state(self.as_raw(), plane.as_raw())
+ ).map(|p| NonNull::new_unchecked(p))
+ }?;
+
+ BorrowedPlaneState::<P::State>::new(self, state).ok_or(EBUSY)
+ }
+
+ /// Attempt to add the state for `connector` to the atomic state for this composer if it hasn't
+ /// already been added, and create a mutator for it.
+ ///
+ /// If a composer already exists for this `connector`, this function returns `Error(EBUSY)`. If
+ /// attempting to add the state fails, another error code will be returned.
+ pub fn add_connector_state<C>(
+ &self,
+ connector: &C
+ ) -> Result<BorrowedConnectorState<'_, C::State>>
+ where
+ C: AsRawConnector<Driver = T>,
+ {
+ // SAFETY: DRM will only return a valid pointer to a [`drm_plane_state`] - or an error.
+ let state = unsafe {
+ from_err_ptr(
+ bindings::drm_atomic_get_connector_state(self.as_raw(), connector.as_raw())
+ ).map(|c| NonNull::new_unchecked(c))
+ }?;
+
+ BorrowedConnectorState::<C::State>::new(self, state).ok_or(EBUSY)
+ }
+
+ /// Attempt to add any planes affected by changes on `crtc` to this [`AtomicStateComposer`].
+ ///
+ /// Will return an [`Error`] if this fails.
+ pub fn add_affected_planes(&self, crtc: &impl AsRawCrtc<Driver = T>) -> Result {
+ // SAFETY: FFI call with no special safety requirements
+ to_result(unsafe {
+ bindings::drm_atomic_add_affected_planes(self.as_raw(), crtc.as_raw())
+ })
+ }
+}
+
+/// An iterator which goes through each DRM plane currently in an atomic state.
+///
+/// Note that this iterator will return [`OpaquePlane`]s, because it's entirely possible for a
+/// driver to have multiple implementations of [`DriverPlane`] - so we don't know what the fully
+/// qualified type of each plane is.
+pub struct AtomicStatePlaneIter<'a, T: KmsDriver> {
+ state: &'a AtomicState<T>,
+ current_idx: u8,
+}
+
+impl<'a, T: KmsDriver> Iterator for AtomicStatePlaneIter<'a, T> {
+ type Item = &'a OpaquePlane<T>;
+
+ fn next(&mut self) -> Option<Self::Item> {
+ let ptr = self.state.state.get();
+
+ // SAFETY: `planes` is initialized by the time we expose AtomicState<T> through any form to
+ // users. And because we don't allow state mutation outside of mutators, which are single
+ // threaded, the contents of this struct are at least guaranteed not to change through the
+ // duration of this borrow.
+ let planes: &[bindings::__drm_planes_state] = unsafe {
+ slice::from_raw_parts((*ptr).planes.cast_const(), self.state.drm_dev().num_plane() as _)
+ };
+
+ for plane_states in &planes[self.current_idx as _..] {
+ self.current_idx += 1;
+ if !plane_states.ptr.is_null() {
+ // SAFETY: OpaquePlane has an identical data layout, and its only possible values
+ // are NULL or pointing at a valid drm_plane
+ return Some(unsafe { OpaquePlane::from_raw(plane_states.ptr) });
+ }
+ }
+
+ None
+ }
+}
+
+impl<'a, T: KmsDriver> AtomicStatePlaneIter<'a, T> {
+ fn new(state: &'a AtomicState<T>) -> AtomicStatePlaneIter<'a, T> {
+ Self {
+ current_idx: 0,
+ state
+ }
+ }
+}
diff --git a/rust/kernel/drm/kms/connector.rs b/rust/kernel/drm/kms/connector.rs
index f62740d7f6469..6fcfce8b48c64 100644
--- a/rust/kernel/drm/kms/connector.rs
+++ b/rust/kernel/drm/kms/connector.rs
@@ -31,6 +31,7 @@
ModeConfigGuard,
encoder::*,
KmsDriver,
+ atomic::*,
};
use macros::pin_data;
@@ -679,6 +680,80 @@ unsafe fn from_raw_mut<'a>(ptr: *mut bindings::drm_connector_state) -> &'a mut S
}
}
+/// An interface for mutating a [`Connector`]s atomic state.
+///
+/// This type is typically returned by an [`AtomicStateMutator`] within contexts where it is
+/// possible to safely mutate a connector's state. In order to uphold rust's data-aliasing rules,
+/// only [`BorrowedConnectorState`] may exist at a time.
+pub struct BorrowedConnectorState<'a, T: FromRawConnectorState> {
+ state: &'a mut T,
+ mask: &'a Cell<u32>
+}
+
+impl<'a, T: FromRawConnectorState> BorrowedConnectorState<'a, T> {
+ pub(super) fn new<D: KmsDriver>(
+ mutator: &'a AtomicStateMutator<D>,
+ state: NonNull<bindings::drm_connector_state>
+ ) -> Option<Self> {
+ // SAFETY: `connector` is invariant throughout the lifetime of the atomic state, is
+ // initialized by this point, and we're guaranteed it is of type `OpaqueConnector<T>` by
+ // type invariance
+ let connector = unsafe { T::Connector::from_raw((*state.as_ptr()).connector) };
+ let conn_mask = connector.mask();
+ let borrowed_mask = mutator.borrowed_connectors.get();
+
+ if borrowed_mask & conn_mask == 0 {
+ mutator.borrowed_connectors.set(borrowed_mask | conn_mask);
+ Some(Self {
+ mask: &mutator.borrowed_connectors,
+ // SAFETY: We're guaranteed `state` is of `ConnectorState<T>` by type invariance,
+ // and we just confirmed by checking `borrowed_connectors` that no other mutable
+ // borrows have been taken out for `state`
+ state: unsafe { T::from_raw_mut(state.as_ptr()) },
+ })
+ } else {
+ // TODO: Print a kernel warning here, this is a user error
+ None
+ }
+ }
+}
+
+impl<'a, T: DriverConnectorState> Deref for BorrowedConnectorState<'a, ConnectorState<T>> {
+ type Target = T;
+
+ fn deref(&self) -> &Self::Target {
+ &self.state.inner
+ }
+}
+
+impl<'a, T: DriverConnectorState> DerefMut for BorrowedConnectorState<'a, ConnectorState<T>> {
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ &mut self.state.inner
+ }
+}
+
+impl<'a, T: FromRawConnectorState> Drop for BorrowedConnectorState<'a, T> {
+ fn drop(&mut self) {
+ let mask = self.state.connector().mask();
+ self.mask.set(self.mask.get() & !mask);
+ }
+}
+
+impl<'a, T: FromRawConnectorState> AsRawConnectorState for BorrowedConnectorState<'a, T> {
+ type Connector = T::Connector;
+}
+
+impl<'a, T: FromRawConnectorState> private::AsRawConnectorState for BorrowedConnectorState<'a, T> {
+ fn as_raw(&self) -> &bindings::drm_connector_state {
+ self.state.as_raw()
+ }
+
+ unsafe fn as_raw_mut(&mut self) -> &mut bindings::drm_connector_state {
+ // SAFETY: We're bound by the same safety contract as this function
+ unsafe { self.state.as_raw_mut() }
+ }
+}
+
unsafe extern "C" fn atomic_duplicate_state_callback<T: DriverConnectorState>(
connector: *mut bindings::drm_connector
) -> *mut bindings::drm_connector_state
diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index 246d15a15c14d..7864540705f76 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -3,6 +3,7 @@
//! KMS driver abstractions for rust.
use super::{
+ atomic::*,
plane::*,
ModeObject,
StaticModeObject,
@@ -552,6 +553,80 @@ unsafe fn from_raw<'a>(ptr: *const bindings::drm_crtc_state) -> &'a Self {
unsafe { &*(ptr.cast()) }
}
}
+
+/// An interface for mutating a [`Crtc`]s atomic state.
+///
+/// This type is typically returned by an [`AtomicStateMutator`] within contexts where it is
+/// possible to safely mutate a plane's state. In order to uphold rust's data-aliasing rules, only
+/// [`BorrowedCrtcState`] may exist at a time.
+///
+/// # Invariants
+///
+/// `self.state` always points to a valid instance of a [`FromRawCrtcState`] object.
+pub struct BorrowedCrtcState<'a, T: FromRawCrtcState> {
+ state: NonNull<T>,
+ mask: &'a Cell<u32>,
+}
+
+impl<'a, T: FromRawCrtcState> BorrowedCrtcState<'a, T> {
+ pub(super) fn new<D: KmsDriver>(
+ mutator: &'a AtomicStateMutator<D>,
+ state: NonNull<bindings::drm_crtc_state>
+ ) -> Option<Self> {
+ // SAFETY: `crtc` is invariant throughout the lifetime of the atomic state, and always
+ // points to a valid `Crtc<T::Crtc>`
+ let crtc = unsafe { T::Crtc::from_raw((*state.as_ptr()).crtc) };
+ let crtc_mask = crtc.mask();
+ let borrowed_mask = mutator.borrowed_crtcs.get();
+
+ if borrowed_mask & crtc_mask == 0 {
+ mutator.borrowed_crtcs.set(borrowed_mask | crtc_mask);
+ Some(Self {
+ mask: &mutator.borrowed_crtcs,
+ state: state.cast()
+ })
+ } else {
+ None
+ }
+ }
+}
+
+impl<'a, T: FromRawCrtcState> Drop for BorrowedCrtcState<'a, T> {
+ fn drop(&mut self) {
+ // SAFETY: Our interface is proof that we are the only ones with a reference to this data
+ let mask = unsafe { self.state.as_ref() }.crtc().mask();
+ self.mask.set(self.mask.get() & !mask);
+ }
+}
+
+impl<'a, T: DriverCrtcState> Deref for BorrowedCrtcState<'a, CrtcState<T>> {
+ type Target = T;
+
+ fn deref(&self) -> &Self::Target {
+ // SAFETY: Our interface ensures that `self.state.inner` follows rust's data-aliasing rules,
+ // so this is safe
+ unsafe { &*(*self.state.as_ptr()).inner.get() }
+ }
+}
+
+impl<'a, T: DriverCrtcState> DerefMut for BorrowedCrtcState<'a, CrtcState<T>> {
+ 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
+ unsafe { (*self.state.as_ptr()).inner.get_mut() }
+ }
+}
+
+impl<'a, T: FromRawCrtcState> AsRawCrtcState for BorrowedCrtcState<'a, T> {
+ type Crtc = T::Crtc;
+}
+
+impl<'a, T: FromRawCrtcState> private::AsRawCrtcState for BorrowedCrtcState<'a, T> {
+ fn as_raw(&self) -> *mut bindings::drm_crtc_state {
+ self.state.as_ptr().cast()
+ }
+}
+
unsafe extern "C" fn crtc_destroy_callback<T: DriverCrtc>(
crtc: *mut bindings::drm_crtc
) {
diff --git a/rust/kernel/drm/kms/plane.rs b/rust/kernel/drm/kms/plane.rs
index 1c151ae3b3dcc..d6e11a65cc101 100644
--- a/rust/kernel/drm/kms/plane.rs
+++ b/rust/kernel/drm/kms/plane.rs
@@ -29,6 +29,7 @@
UnregisteredKmsDevice,
ModeObject,
StaticModeObject,
+ atomic::*,
};
/// The main trait for implementing the [`struct drm_plane`] API for [`Plane`]
@@ -597,6 +598,82 @@ unsafe fn from_raw_mut<'a>(ptr: *mut bindings::drm_plane_state) -> &'a mut Self
unsafe { &mut *ptr.cast() }
}
}
+
+/// An interface for mutating a [`Plane`]s atomic state.
+///
+/// This type is typically returned by an [`AtomicStateMutator`] within contexts where it is
+/// possible to safely mutate a plane's state. In order to uphold rust's data-aliasing rules, only
+/// [`BorrowedPlaneState`] may exist at a time.
+pub struct BorrowedPlaneState<'a, T: FromRawPlaneState> {
+ state: &'a mut T,
+ mask: &'a Cell<u32>
+}
+
+impl<'a, T: FromRawPlaneState> BorrowedPlaneState<'a, T> {
+ pub(super) fn new<D: KmsDriver>(
+ mutator: &'a AtomicStateMutator<D>,
+ state: NonNull<bindings::drm_plane_state>
+ ) -> Option<Self> {
+ // SAFETY: `plane` is invariant throughout the lifetime of the atomic state, is
+ // initialized by this point, and we're guaranteed it is of type `AsRawPlane` by type
+ // invariance
+ let plane = unsafe { T::Plane::from_raw((*state.as_ptr()).plane) };
+ let plane_mask = plane.mask();
+ let borrowed_mask = mutator.borrowed_planes.get();
+
+ if borrowed_mask & plane_mask == 0 {
+ mutator.borrowed_planes.set(borrowed_mask | plane_mask);
+ Some(Self {
+ mask: &mutator.borrowed_planes,
+ // SAFETY: We're guaranteed `state` is of `FromRawPlaneState` by type invariance,
+ // and we just confirmed by checking `borrowed_planes` that no other mutable borrows
+ // have been taken out for `state`
+ state: unsafe { T::from_raw_mut(state.as_ptr()) },
+ })
+ } else {
+ None
+ }
+ }
+}
+
+impl<'a, T: FromRawPlaneState> Drop for BorrowedPlaneState<'a, T> {
+ fn drop(&mut self) {
+ let mask = self.state.plane().mask();
+ self.mask.set(self.mask.get() & !mask);
+ }
+}
+
+impl<'a, T: FromRawPlaneState> AsRawPlaneState for BorrowedPlaneState<'a, T> {
+ type Plane = T::Plane;
+}
+
+impl<'a, T: FromRawPlaneState> private::AsRawPlaneState for BorrowedPlaneState<'a, T> {
+ fn as_raw(&self) -> &bindings::drm_plane_state {
+ self.state.as_raw()
+ }
+
+ unsafe fn as_raw_mut(&mut self) -> &mut bindings::drm_plane_state {
+ // SAFETY: This function is bound by the same safety contract as `self.inner.as_raw_mut()`
+ unsafe { self.state.as_raw_mut() }
+ }
+}
+
+impl<'a, T: FromRawPlaneState> Sealed for BorrowedPlaneState<'a, T> {}
+
+impl<'a, T: DriverPlaneState> Deref for BorrowedPlaneState<'a, PlaneState<T>> {
+ type Target = T;
+
+ fn deref(&self) -> &Self::Target {
+ &self.state.inner
+ }
+}
+
+impl<'a, T: DriverPlaneState> DerefMut for BorrowedPlaneState<'a, PlaneState<T>> {
+ fn deref_mut(&mut self) -> &mut Self::Target {
+ &mut self.state.inner
+ }
+}
+
unsafe extern "C" fn plane_destroy_callback<T: DriverPlane>(
plane: *mut bindings::drm_plane
) {
--
2.46.1
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