An optional trait method for implementing a CRTC's atomic state check.
Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
---
V3:
* Document uses of ManuallyDrop
Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
---
rust/kernel/drm/kms/atomic.rs | 1 -
rust/kernel/drm/kms/crtc.rs | 55 +++++++++++++++++++++++++++++++++--
2 files changed, 52 insertions(+), 4 deletions(-)
diff --git a/rust/kernel/drm/kms/atomic.rs b/rust/kernel/drm/kms/atomic.rs
index 3d5c70dbc4274..e0a1b5b860d6f 100644
--- a/rust/kernel/drm/kms/atomic.rs
+++ b/rust/kernel/drm/kms/atomic.rs
@@ -274,7 +274,6 @@ impl<T: KmsDriver> AtomicStateComposer<T> {
/// # Safety
///
/// The caller guarantees that `ptr` points to a valid instance of `drm_atomic_state`.
- #[allow(dead_code)]
pub(crate) unsafe fn new(ptr: NonNull<bindings::drm_atomic_state>) -> Self {
// SAFETY: see `AtomicStateMutator::from_raw()`
Self(unsafe { AtomicStateMutator::new(ptr) })
diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
index 3b9c9d97fcf24..50f5b68f4a3fe 100644
--- a/rust/kernel/drm/kms/crtc.rs
+++ b/rust/kernel/drm/kms/crtc.rs
@@ -12,7 +12,7 @@
alloc::KBox,
bindings,
drm::device::Device,
- error::to_result,
+ error::{from_result, to_result},
init::Zeroable,
prelude::*,
private::Sealed,
@@ -21,7 +21,7 @@
use core::{
cell::{Cell, UnsafeCell},
marker::*,
- mem,
+ mem::{self, ManuallyDrop},
ops::{Deref, DerefMut},
ptr::{addr_of_mut, null, null_mut, NonNull},
};
@@ -78,7 +78,11 @@ pub trait DriverCrtc: Send + Sync + Sized {
helper_funcs: bindings::drm_crtc_helper_funcs {
atomic_disable: None,
atomic_enable: None,
- atomic_check: None,
+ atomic_check: if Self::HAS_ATOMIC_CHECK {
+ Some(atomic_check_callback::<Self>)
+ } else {
+ None
+ },
dpms: None,
commit: None,
prepare: None,
@@ -113,6 +117,21 @@ pub trait DriverCrtc: Send + Sync + Sized {
///
/// Drivers may use this to instantiate their [`DriverCrtc`] object.
fn new(device: &Device<Self::Driver>, args: &Self::Args) -> impl PinInit<Self, Error>;
+
+ /// The optional [`drm_crtc_helper_funcs.atomic_check`] hook for this crtc.
+ ///
+ /// Drivers may use this to customize the atomic check phase of their [`Crtc`] objects. The
+ /// result of this function determines whether the atomic check passed or failed.
+ ///
+ /// [`drm_crtc_helper_funcs.atomic_check`]: srctree/include/drm/drm_modeset_helper_vtables.h
+ fn atomic_check(
+ _crtc: &Crtc<Self>,
+ _old_state: &CrtcState<Self::State>,
+ _new_state: CrtcStateMutator<'_, CrtcState<Self::State>>,
+ _state: &AtomicStateComposer<Self::Driver>,
+ ) -> Result {
+ build_error::build_error("This should not be reachable")
+ }
}
/// The generated C vtable for a [`DriverCrtc`].
@@ -859,3 +878,33 @@ fn vtable(&self) -> *const Self::Vtable {
// SAFETY: DRM takes ownership of the state from here, and will never move it
unsafe { bindings::__drm_atomic_helper_crtc_reset(crtc.as_raw(), KBox::into_raw(new).cast()) };
}
+
+unsafe extern "C" fn atomic_check_callback<T: DriverCrtc>(
+ crtc: *mut bindings::drm_crtc,
+ state: *mut bindings::drm_atomic_state,
+) -> i32 {
+ // SAFETY:
+ // - We're guaranteed `crtc` is of type `Crtc<T>` via type invariants.
+ // - We're guaranteed by DRM that `crtc` is pointing to a valid initialized state.
+ let crtc = unsafe { Crtc::from_raw(crtc) };
+
+ // SAFETY: DRM guarantees `state` points to a valid `drm_atomic_state`
+ // We use a ManuallyDrop here to avoid AtomicStateComposer dropping an owned reference we never
+ // acquired.
+ let state =
+ unsafe { ManuallyDrop::new(AtomicStateComposer::new(NonNull::new_unchecked(state))) };
+
+ // SAFETY: Since we are in the atomic update callback, we're guaranteed by DRM that both the old
+ // and new atomic state are present within `state`
+ let (old_state, new_state) = unsafe {
+ (
+ state.get_old_crtc_state(crtc).unwrap_unchecked(),
+ state.get_new_crtc_state(crtc).unwrap_unchecked(),
+ )
+ };
+
+ from_result(|| {
+ T::atomic_check(crtc, old_state, new_state, &state)?;
+ Ok(0)
+ })
+}
--
2.48.1
