On Wed, Mar 05, 2025 at 05:59:35PM -0500, Lyude Paul wrote:
> 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")
> + }
We've spent an awful lot of time trying to get rid of
old_state/new_state in the atomic hooks, so I'd prefer to not
reintroduce them again in Rust, even more so if you have accessors to go
from AtomicStateComposer to CrtcStateMutator, which I think you do.
Maxime
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