Hi Lyude
> On 30 Sep 2024, at 20:10, Lyude Paul <lyude@xxxxxxxxxx> wrote:
>
> Optional trait methods for implementing the atomic_enable and
> atomic_disable callbacks of a CRTC.
>
> Signed-off-by: Lyude Paul <lyude@xxxxxxxxxx>
> ---
> rust/kernel/drm/kms/crtc.rs | 76 ++++++++++++++++++++++++++++++++++++-
> 1 file changed, 74 insertions(+), 2 deletions(-)
>
> diff --git a/rust/kernel/drm/kms/crtc.rs b/rust/kernel/drm/kms/crtc.rs
> index a4e955364bd8c..ef1b331f742d0 100644
> --- a/rust/kernel/drm/kms/crtc.rs
> +++ b/rust/kernel/drm/kms/crtc.rs
> @@ -80,8 +80,8 @@ pub trait DriverCrtc: Send + Sync + Sized {
> },
>
> helper_funcs: bindings::drm_crtc_helper_funcs {
> - atomic_disable: None,
> - atomic_enable: None,
> + atomic_disable: if Self::HAS_ATOMIC_DISABLE { Some(atomic_disable_callback::<Self>) } else { None },
> + atomic_enable: if Self::HAS_ATOMIC_ENABLE { Some(atomic_enable_callback::<Self>) } else { None },
> atomic_check: if Self::HAS_ATOMIC_CHECK { Some(atomic_check_callback::<Self>) } else { None },
> dpms: None,
> commit: None,
> @@ -162,6 +162,34 @@ fn atomic_flush(
> ) {
> build_error::build_error("This should never be reachable")
> }
> +
> + /// The optional [`drm_crtc_helper_funcs.atomic_enable`] hook.
> + ///
> + /// This hook will be called before enabling a [`Crtc`] in an atomic commit.
> + ///
> + /// [`drm_crtc_helper_funcs.atomic_enable`]: srctree/include/drm/drm_modeset_helper_vtables.h
> + fn atomic_enable(
> + 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")
> + }
> +
> + /// The optional [`drm_crtc_helper_funcs.atomic_disable`] hook.
> + ///
> + /// This hook will be called before disabling a [`Crtc`] in an atomic commit.
> + ///
> + /// [`drm_crtc_helper_funcs.atomic_disable`]: srctree/include/drm/drm_modeset_helper_vtables.h
> + fn atomic_disable(
> + 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 previous patches.
>
> /// The generated C vtable for a [`DriverCrtc`].
> @@ -850,3 +878,47 @@ fn as_raw(&self) -> *mut bindings::drm_crtc_state {
>
> T::atomic_flush(crtc, old_state, new_state, &state);
> }
> +
> +unsafe extern "C" fn atomic_enable_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: DRM never passes an invalid ptr for `state`
> + let state = unsafe { AtomicStateMutator::new(NonNull::new_unchecked(state)) };
> +
> + // SAFETY: We're in an atomic enable 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_enable(crtc, old_state, new_state, &state);
> +}
> +
> +unsafe extern "C" fn atomic_disable_callback<T: DriverCrtc>(
> + crtc: *mut bindings::drm_crtc,
> + state: *mut bindings::drm_atomic_state,
> +) {
> + // SAFETY:
> + // * We're guaranteed `crtc` points to a valid instance of `drm_crtc`
> + // * We're guaranteed that `crtc` is of type `Plane<T>` by `DriverPlane`s type invariants.
> + let crtc = unsafe { Crtc::from_raw(crtc) };
> +
> + // SAFETY: We're guaranteed that `state` points to a valid `drm_crtc_state` by DRM
> + let state = unsafe { AtomicStateMutator::new(NonNull::new_unchecked(state)) };
> +
> + // SAFETY: We're in an atomic commit 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_disable(crtc, old_state, new_state, &state);
> +}
> --
> 2.46.1
>
>
FYI, they all look good to me. It’s just a matter of figuring out this build_error pattern and whether it’s
really needed.
— Daniel
