Hi Lyude,
> On 30 Sep 2024, at 20:10, Lyude Paul <lyude@xxxxxxxxxx> wrote:
>
> Optional trait methods for implementing the atomic_begin and atomic_flush
> callbacks for a CRTC.
>
> Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
> ---
> rust/kernel/drm/kms/crtc.rs | 78 ++++++++++++++++++++++++++++++++++++-
> 1 file changed, 76 insertions(+), 2 deletions(-)
>
> diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
> index ec9b58763dcca..a4e955364bd8c 100644
> --- a/rust/kernel/drm/kms/crtc.rs
> +++ b/rust/kernel/drm/kms/crtc.rs
> @@ -90,8 +90,8 @@ pub trait DriverCrtc: Send + Sync + Sized {
> mode_set: None,
> mode_valid: None,
> mode_fixup: None,
> - atomic_begin: None,
> - atomic_flush: None,
> + atomic_begin: if Self::HAS_ATOMIC_BEGIN { Some(atomic_begin_callback::<Self>) } else { None },
> + atomic_flush: if Self::HAS_ATOMIC_FLUSH { Some(atomic_flush_callback::<Self>) } else { None },
> mode_set_nofb: None,
> mode_set_base: None,
> mode_set_base_atomic: None,
> @@ -132,6 +132,36 @@ fn atomic_check(
> ) -> Result {
> build_error::build_error("This should not be reachable")
> }
> +
> + /// The optional [`drm_crtc_helper_funcs.atomic_begin`] hook.
> + ///
> + /// This hook will be called before a set of [`Plane`] updates are performed for the given
> + /// [`Crtc`].
> + ///
> + /// [`drm_crtc_helper_funcs.atomic_begin`]: srctree/include/drm/drm_modeset_helper_vtables.h
> + fn atomic_begin(
> + crtc: &Crtc<Self>,
> + old_state: &CrtcState<Self::State>,
> + new_state: BorrowedCrtcState<'_, CrtcState<Self::State>>,
> + state: &AtomicStateMutator<Self::Driver>
> + ) {
> + build_error::build_error("This should not be reachable")
> + }
> +
> + /// The optional [`drm_crtc_helper_funcs.atomic_flush`] hook.
> + ///
> + /// This hook will be called after a set of [`Plane`] updates are performed for the given
> + /// [`Crtc`].
> + ///
> + /// [`drm_crtc_helper_funcs.atomic_flush`]: srctree/include/drm/drm_modeset_helper_vtables.h
> + fn atomic_flush(
> + crtc: &Crtc<Self>,
> + old_state: &CrtcState<Self::State>,
> + new_state: BorrowedCrtcState<'_, CrtcState<Self::State>>,
> + state: &AtomicStateMutator<Self::Driver>
> + ) {
> + build_error::build_error("This should never be reachable")
> + }
> }
Same comment here as in the previous patches, i.e.: if this is optional, why do we have a
default implementation with build_error?
>
> /// The generated C vtable for a [`DriverCrtc`].
> @@ -776,3 +806,47 @@ fn as_raw(&self) -> *mut bindings::drm_crtc_state {
> Ok(0)
> })
> }
> +
> +unsafe extern "C" fn atomic_begin_callback<T: DriverCrtc>(
> + crtc: *mut bindings::drm_crtc,
> + state: *mut bindings::drm_atomic_state,
> +) {
> + // 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: We're guaranteed by DRM that `state` points to a valid instance of `drm_atomic_state`
> + let state = unsafe { AtomicStateMutator::new(NonNull::new_unchecked(state)) };
> +
> + // SAFETY: We're guaranteed by DRM that both the old and new atomic state are present within
> + // this `drm_atomic_state`
> + let (old_state, new_state) = unsafe {(
> + state.get_old_crtc_state(crtc).unwrap_unchecked(),
> + state.get_new_crtc_state(crtc).unwrap_unchecked(),
> + )};
> +
> + T::atomic_begin(crtc, old_state, new_state, &state);
> +}
> +
> +unsafe extern "C" fn atomic_flush_callback<T: DriverCrtc>(
> + crtc: *mut bindings::drm_crtc,
> + state: *mut bindings::drm_atomic_state,
> +) {
> + // 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: We're guaranteed by DRM that `state` points to a valid instance of `drm_atomic_state`
> + let state = unsafe { AtomicStateMutator::new(NonNull::new_unchecked(state)) };
> +
> + // SAFETY: We're in an atomic flush callback, so we know that both the new and old state are
> + // present
> + let (old_state, new_state) = unsafe {(
> + state.get_old_crtc_state(crtc).unwrap_unchecked(),
> + state.get_new_crtc_state(crtc).unwrap_unchecked(),
> + )};
> +
> + T::atomic_flush(crtc, old_state, new_state, &state);
> +}
> --
> 2.46.1
>
>
— Daniel
